The Diagnostic Accuracy of Contrast-Enhanced CT of the Neck for the Investigation of Sialolithiasis

BACKGROUND AND PURPOSE:Sialolithiasis is a common benign pathology affecting the salivary glands but it is unclear if contrast-enhanced CT, which is commonly used for investigation of head and neck pathology, can identify calculi as accurately as noncontrast CT. The aim of this study was to assess the diagnostic accuracy of contrast-enhanced CT of the neck in the diagnosis of sialolithiasis compared with noncontrast CT of the neck used as the criterion standard.MATERIALS AND METHODS:This was a retrospective, case-control study of 92 consecutive cases in 90 patients who underwent both noncontrast CT of the neck and contrast-enhanced CT of the neck in 2 tertiary referral centers from January 2011 to December 2015 for investigation of sialolithiasis. Axial 3-mm-section images were assessed by a fellowship-trained diagnostic neuroradiologist and diagnostic neuroradiology fellow in consensus. Blinded assessment of the contrast-enhanced CT of the neck was performed first, followed by noncontrast CT of the neck after a 2-week interval. The presence or absence of a stone and stone location and size were documented. Statistical analysis was undertaken to assess the agreement between CT protocols and calculate the sensitivity and specificity of contrast-enhanced CT of the neck.RESULTS:Fifty calculi were identified on noncontrast CT of the neck in 31 cases; and 48 calculi, in 31 cases on contrast-enhanced CT of the neck. No calculi were identified in the remaining 61 cases. The sensitivity and specificity of contrast-enhanced CT of the neck in the detection of sialolithiasis was 96% (95% CI, 86.3%–99.5%) and 100% (95% CI, 94.1%–100%), respectively. The positive predictive value of contrast-enhanced CT of the neck was 100% (95% CI, 92.6%–100%), and the negative predictive value was 96.8% (95% CI, 89%–99.6%). The accuracy of contrast-enhanced CT of the neck in diagnosing the presence or absence of salivary calculi was 98%.CONCLUSIONS:Contrast-enhanced CT of the neck is accurate in the detection of sialolithiasis, with no difference in diagnostic accuracy compared with noncontrast CT of the neck.

Sialolithiasis is defined as the formation of calculi within the salivary glands.¹ It is the most common non-neoplastic condition that affects them. Calculi, which are often multiple, cause partial or complete obstruction of the salivary duct, resulting in obstructive sialadenitis, which may manifest as acute or chronic unilateral gland swelling and pain.^2–6 Symptoms typically arise during eating because chewing food precipitates salivation.⁷ Sialadenitis can be complicated by bacterial infection and abscess formation.^5,8 While calculi in the distal submandibular duct may be readily detectable clinically by bimanual palpation, calculi in the proximal submandibular duct or gland and parotid duct or gland depend on imaging for diagnosis.⁸Noncontrast CT of the neck (NCCTN) has been recommended for the evaluation of salivary calculi because it is sensitive for the detection of calcifications.⁹ One of the drawbacks of NCCTN is that it provides less detail of duct dilation and intraductal or glandular pathology than contrast-enhanced CT of the neck (CECTN).¹⁰ Traditionally, the use of CECTN in this setting has been in addition to the NCCTN rather than as a stand-alone test.¹¹ Concerns have been raised that on CECTN, blood vessels may simulate small sialoliths and lead to a false-positive diagnosis or reduce diagnostic certainty.^9,11 CECTN has been used for the evaluation of complicated stone disease in a suspected abscess or an inflammatory process after calculi have been identified on NCCTN.^9,11,12 The use of NCCTN alone gives less detail of glandular and periglandular inflammation.⁹ The addition of CECTN, however, will cause an increase in the patient radiation dose.The purpose of this study was to determine the accuracy of CECTN alone in the detection of salivary calculi compared with NCCTN alone. A secondary objective was to calculate the patient radiation dose when performing both NCCTN and CECTN.     

CT Angiography Findings in Carotid Blowout Syndrome and Its Role as a Predictor of 1-Year Survival

BACKGROUND AND PURPOSE:Carotid blowout is a serious late complication of prior treatment of advanced head and neck cancer. We evaluate the efficacy of CTA in the diagnosis of impending carotid blowout syndrome in patients with head and neck cancer, and its capability to predict clinical outcome.MATERIALS AND METHODS:The clinical data of 29 patients with impending carotid blowout who underwent CTA were collected and analyzed. Imaging signs included tissue necrosis, exposed artery, viable perivascular tumor, pseudoaneurysm, and contrast extravasation. DSA was obtained in 20 patients. One-year outcomes were compared based on management.RESULTS:The most common CTA finding was necrosis (94%), followed by exposed artery (73%), viable tumor (67%), pseudoaneurysm (58%), and contrast extravasation (30%). Exposed artery, pseudoaneurysm, and contrast extravasation were the 3 CTA findings related to outcomes. All of the pseudoaneurysm and contrast extravasation cases were associated with an exposed artery. An exposed artery was the most important prognostic predictor and could not be diagnosed on DSA. Patients without the 3 findings on CTA (group 1) had the best survival rate at 1-year follow-up, followed by patients with the 3 findings treated immediately by permanent artery occlusion (group 2). Patients with the 3 findings who had no immediate treatment (group 3) had the worst outcomes (P < .001 in group 1 vs group 3 and group 2 vs group 3; P = .056 group 1 vs group 2).CONCLUSIONS:CTA, with its ability to diagnose an exposed artery compared with DSA, may offer important management and prognostic information in patients with impending carotid blowout.

Carotid blowout syndrome (CBS) is defined as rupture of the carotid artery and its branches and is a serious complication after treatment of advanced head and neck cancer. Potential causes of CBS include radical resection, radiation therapy and radiation necrosis, carotid exposure, wound infection, pharyngocutaneous fistula, and recurrent or persistent carcinoma.¹ The overall incidence of carotid blowout after neck dissection has been reported to be as high as 4.3%, and the risk is increased another 7.6-fold with further radiation therapy.² CBS typically occurs 2–20 years after surgery or radiation therapy,^3,4 and average estimates of cumulative neurologic morbidity and mortality are above 60% and 40%, respectively, in patients with CBS.⁵ CBS can be categorized into 1 of 3 categories: threatened, impending, and acute carotid blowout.¹ Threatened carotid blowout is defined as physical examination or imaging results that suggest inevitable hemorrhage from 1 of the carotid arteries or its branches if no action is taken. Impending carotid blowout (also called sentinel hemorrhage) is defined as transient hemorrhage that resolves spontaneously or with packing or pressure. Acute carotid blowout represents hemorrhage that cannot be controlled by packing or pressure.¹ Surgical management of carotid blowout is usually technically difficult and is associated with high morbidity and mortality rates.^1,2,6,7 After surgical ligation or permanent arterial occlusion (PAO) of the carotid artery, the incidence of immediate or delayed cerebral ischemic complications can be as high as 15%–20%.^7,8–12 The complication rate of a balloon occlusion test before PAO of the carotid artery is reported to be as high as 3.2%, and it may be even higher in fragile postirradiation vessels.¹³ Delayed ischemia after passing the balloon occlusion test is yet another concern.^10,14,15 Stent-graft deployment, with or without coiling, is another endovascular treatment of CBS. Stent-grafting can preserve the affected carotid flow but has a high rate of early and delayed complications.^16–19 No significant difference in short-term outcome between stent-graft deployment and PAO has been reported,²⁰ and long-term results have not been reported.¹⁷CTA has become widely available and is sensitive and specific in the detection of hemorrhagic vascular disorders such as aneurysms, arteriovenous malformations, dural arteriovenous fistulas, and intracranial dissections. Contrast extravasation on CTA predicts hematoma expansion, mortality, and clinical outcome in primary intracerebral hemorrhage.^21–26 To our knowledge, there have been no past reports about the use of CTA in the diagnosis of CBS or as an outcome predictor. The aim of our study was to evaluate the efficacy of CTA in the diagnosis of impending CBS, and its capability to predict clinical outcome after management.     

Subspecialty Virtual Impact Factors within a Dedicated Neuroimaging Journal

BACKGROUND AND PURPOSE:The growing number of subspecialties within neuroradiology compete for pages in neuroradiology journals. We performed a bibliometric analysis of the American Journal of Neuroradiology to identify the virtual Impact Factor of different journal subsections and article topics.MATERIALS AND METHODS:Original Research and Review Articles published in American Journal of Neuroradiology during 2010–2012 were evaluated. The journal section for each article was recorded, and the number of citations was evaluated by using the Web of Science database. Numbers of citations within the first 2 years after publication were evaluated, normalized to the 2013 journal Impact Factor (for American Journal of Neuroradiology, 3.675), and used to calculate a virtual Impact Factor for different journal subsections.RESULTS:One thousand forty-nine Original Research and Review Articles were published during this time, which obtained an average of 6.59 citations each within their first 2 years after publication; 91.8% of articles obtained at least 1 citation. Expedited Publications had the greatest number of citations, averaging 43.7 citations each (virtual Impact Factor, 24.39), followed by Review Articles averaging 9.39 citations each (virtual Impact Factor 5.23). Virtual Impact Factors for other sections were the following: Interventional, 4.54; Brain, 3.70; Pediatrics, 2.91; Functional, 2.74; Head & Neck, 2.24; and Spine, 1.86. Virtual Impact Factors for article topics were the following: interventional, 4.75; functional/advanced, 3.79; brain, 3.66; pediatrics, 2.99; head and neck, 2.46; and spine, 2.32.CONCLUSIONS:Citation patterns of Original Research and Review Articles in American Journal of Neuroradiology varied widely on the basis of subsections. Understanding the citation patterns of specific topics and subsections of a journal may aid authors and editors in evaluating the appropriate balance among various topics and allow authors to determine whether their articles are being cited at a level expected for similar ones in a journal.

Citation analysis is an important means of evaluating the performance of journals and of authors, with implications regarding promotions, grant funding, advertising sales, and library selections.^1–3 The growing number of subspecialties within neuroradiology compete for journal pages, and citation profiles of these different subsections have not been evaluated. We performed a bibliometric analysis of American Journal of Neuroradiology (AJNR) to identify citation patterns based on subsections and article topics.Neuroradiology encompasses evaluation of the brain, head and neck, spine, and peripheral nervous system, including minimally invasive diagnostic and therapeutic techniques in these areas. Several journals dedicated to neuroradiology exist; however, neuroradiologic articles are also included in general radiology journals and in radiology subspecialty journals such as those dedicated to pediatric radiology. While there is a growing body of bibliometric analyses in the radiology literature,^4–7 few studies have focused on neuroradiology topics to date.^8–10We hypothesized that the citation characteristics of a journal are heterogeneous among journal subsections and varying topics. We undertook a bibliometric analysis to evaluate the citation characteristics of neuroradiology articles within a neuroradiology journal. We additionally sought to determine the citation characteristics of neuroradiology articles pertaining to specific subtopics.     

Diagnostic Yield of Emergency Department Arch-to-Vertex CT Angiography in Patients with Suspected Acute Stroke

BACKGROUND AND PURPOSE:Our aim was to investigate how often relevant diagnostic findings in an arch-to-vertex CTA scan, obtained specifically as part of the acute stroke CT protocol, are located in the head, neck, and upper chest regions.MATERIALS AND METHODS:Radiology reports were reviewed in 302 consecutive patients (170 men, 132 women; median ages, 66 and 73 years, respectively) who underwent emergency department investigation of suspected acute stroke between January and July 2010. Diagnostic CTA findings relevant to patient management were recorded for the head, neck, and chest regions individually. Additionally, the contributions to the total CTA scan effective dose were estimated from each of the 3 anatomic regions by using the ImPACT CT Dose Calculator.RESULTS:Of the 302 patients, 161 (54%) had relevant diagnostic findings in the head; 94 (31%), in the neck; and 4 (1%), in the chest. The estimated contributions to the total CTA scan dose from each body region, head, neck, and upper chest, were 14 ± 2%, 33 ± 5%, and 53 ± 6%, respectively.CONCLUSIONS:Most clinically relevant findings are in the head and neck, supporting inclusion of these regions in arch-to-vertex CTA performed specifically in patients with acute stroke in the emergency department. Further studies are required to investigate extending the scan to the upper chest because only 1% of patients in our study had clinically relevant findings in the mediastinum, yet half the CTA effective dose was due to scanning in this region.

In the evaluation of patients presenting to the emergency department within 4.5 hours of the onset of acute stroke or strokelike symptoms, emphasis is placed on the immediate identification of inclusion and exclusion criteria for the administration of intravenous thrombolytic therapy.^1–6 Subsequent investigation of risk factors for stroke is an elective process and typically does not begin until after the acute event has passed.^7–9With improvement in CT technology, the limitations on scan coverage of neurovascular CTA have relaxed, and single-pass imaging from the aortic arch to the skull vertex has become commonplace.^10–15 Nevertheless, we have found no studies that evaluated benefit to the patient from this practice. Furthermore, current guidelines for the emergency management of patients with acute stroke remain focused on noncontrast head CT and CTA evaluation only of the intracranial circulation.^1,16–17Our primary purpose was to investigate the incidence of diagnostically relevant findings reported in the head, neck, and chest components of an arch-to-vertex CTA performed in the emergency department as part of the immediate evaluation and triage of acute stroke. A secondary aim was to estimate the individual contributions to the total effective dose in these regions.     

Acute Bleeding in the Head and Neck: Angiographic Findings and Endovascular Management

BACKGROUND AND PURPOSE:Life-threatening bleeding in the head and neck requires urgent management. This study evaluated the angiographic findings related to head and neck bleeding and presents endovascular management techniques.MATERIAL AND METHODS:Sixty-one consecutive patients who presented with acute bleeding in the head and neck areas and subsequently underwent endovascular therapy between January 2002 and October 2012 were included in our study. We evaluated the angiographic findings, techniques, and results of endovascular management.RESULTS:Contrast leakage (n = 10), pseudoaneurysm (n = 20), or both (n = 10) were the most common life-threatening angiographic findings (66%) and were the foci of immediate embolization or endoluminal vessel reconstruction. Seventeen patients (28%) had hypervascular staining of the tumor or mucosa, and 4 patients (6%) did not have any abnormal findings. The acute bleeding was successfully controlled by endovascular management according to the bleeding foci. Carotid arterial lesions, so-called “carotid blowout,” required reconstructive or deconstructive therapy. Bleeding of the external carotid artery required specific branch embolization by a combination of various embolic materials. No procedure-related complications occurred except in 1 patient who experienced acute infarction caused by thromboemboli from the covered stent. Seventeen patients (28%) were retreated due to rebleeding after the mean 20-month follow-up.CONCLUSIONS:Contrast leakage or a pseudoaneurysm or both seen on angiography are active bleeding foci and targets for therapy in patients with acute bleeding in the head and neck area. Despite different bleeding-control strategies according to vessel involvement, endovascular treatment is safe and effective for controlling hemorrhage.

Acute bleeding in the head and neck area occurs due to various causes and often is a life-threatening situation. If conservative management is unsuccessful, conventional angiography followed by endovascular treatment can have a major role in localizing the source of the bleeding and obliterating bleeding foci, thus leading to immediate and complete hemostasis.Head and neck cancers are the main cause of intractable hemorrhage from local tumor irradiation or spontaneous tumor bleeding.^1–5 Acute rupture of irradiated, large vessels is a rare but life-threatening therapy complication.⁶ In addition to tumor-related bleeding, there is also iatrogenic bleeding related to surgical procedures or craniomaxillofacial trauma, which can also lead to intractable, life-threatening bleeding.The distribution of bleeding foci is diverse and can range from large vessels, such as the internal or common carotid arteries, to small branches of the external carotid artery (ECA). Identification of the lesion location is mandatory when performing an angiographic procedure and analyzing the angiographic findings because the exact localization of the bleeding site is associated with immediate bleeding control.The endovascular management of bleeding arising from the extracranial carotid arteries, the so-called “carotid blowout syndrome,” has been extensively reported.^7–14 However, to our knowledge, the exact extent of the carotid blowout syndrome (CBS) in patients with acute bleeding has not been evaluated or compared with that of patients without CBS, despite the completely different application of endovascular hemostatic techniques for CBS versus non-CBS lesions. Therefore, we present our experience of endovascular management of 61 patients with acute head and neck bleeding from a variety of causes, with an emphasis on the angiographic results and the subsequent endovascular management according to the angiographic findings. We also compared the differences between patients with and without tumors related to the causative angiographic features, treatment outcome, and rate of endovascular retreatment.     

Low-Tube-Voltage 80-kVp Neck CT: Evaluation of Diagnostic Accuracy and Interobserver Agreement

BACKGROUND AND PURPOSE:Low-tube-voltage acquisition has been shown to facilitate substantial dose savings for neck CT with similar image contrast compared with standard 120-kVp acquisition. However, its potential for the detection of neck pathologies is uncertain. Our aim was to evaluate the effects of low-tube-voltage 80-kV(peak) acquisitions for neck CT on diagnostic accuracy and interobserver agreement.MATERIALS AND METHODS:Three radiologists individually analyzed 80-kVp and linearly blended 120-kVp image series of 170 patients with a variety of pathologies who underwent dual-energy neck CT. Reviewers were unblinded to the clinical indication for CT but were otherwise blinded to any other data or images and were asked to state a final main diagnosis. Findings were compared with medical record charts, CT reports, and pathology results. Sensitivity, specificity, positive predictive value, and negative predictive value were calculated for each observer. Interobserver agreement was evaluated by using intraclass correlation coefficients.RESULTS:Diagnoses were grouped as squamous cell carcinoma–related (n = 107, presence/absence of primary/recurrent squamous cell carcinoma), lymphoma-related (n = 40, presence/absence of primary/recurrent lymphoma), and benign (n = 23, eg, abscess). Cumulative sensitivity, specificity, positive predictive value, and negative predictive value for 80-kVp and blended 120-kVp images were 94.8%, 93.0%, 95.9%, and 91.1%, respectively. Results were also consistently high for squamous cell carcinoma–related (94.8%/95.3%, 89.1%/89.1%, 94.3%/94.4%, 90.1%/91.0%) and lymphoma-related (95.0%, 100.0%, 100.0%, 95.2%) 80-kVp/120-kVp image series. Global interobserver agreement was almost perfect (intraclass correlation coefficient, 0.82, 0.80; 95% CI, 0.76–0.74, 0.86–0.85). Calculated dose-length product was reduced by 48% with 80-kVp acquisitions compared with the standard 120-kVp scans (135.5 versus 282.2 mGy × cm).CONCLUSIONS:Low-tube-voltage 80-kVp CT of the neck provides sufficient image quality with high diagnostic accuracy in routine clinical practice and has the potential to substantially decrease radiation exposure.

CT is a standard imaging technique in routine clinical practice for detection, staging, and follow-up evaluation of various pathologies of the neck, including squamous cell carcinoma (SCC), cervical lymphoma or lymphadenopathy, and parapharyngeal or retropharyngeal abscess.^1–5 CT examinations contribute a substantial amount of cumulative radiation exposure to patients with cervical pathologies, especially if follow-up CT is required.⁶ Thus, various approaches for dose reduction of CT of the neck, brain, paranasal sinus, and the facial skeleton have been proposed, including reduction of tube current and tube potential, high-pitch acquisition, and application of automated exposure-control software.^7–10 The combination of such techniques with an iterative reconstruction algorithm can also provide similar image quality while substantially reducing exposure to ionizing radiation compared with the standard 120-kVp acquisitions.^11,12Several studies have demonstrated that low-tube-voltage acquisitions at 80 kVp can increase iodine attenuation and image contrast of soft-tissue structures and reduce radiation exposure.^13–15 However, only a few studies have investigated low-tube-voltage acquisition CT techniques for imaging of the neck.^16–18 We hypothesized that an 80-kVp acquisition may provide comparable image quality for evaluation of the neck region. To evaluate the efficacy of this technique in simulated routine clinical practice, we retrospectively assessed the diagnostic accuracy of low-tube-voltage 80-kVp image series from dual-energy neck CT (DECT) for evaluation of a variety of cervical pathologies, and the results were compared with linearly blended images representing a standard 120-kVp acquisition. We also assessed interobserver agreement and calculated the potential radiation dose reduction.     

Kimura disease: CT and MR imaging findings

BACKGROUND AND PURPOSE:KD is a rare chronic inflammatory disorder of unknown etiology. The purpose of this study was to evaluate the CT and MR imaging findings of KD in the head and neck.MATERIALS AND METHODS:We retrospectively reviewed the CT (n = 21) and MR (n = 9) images obtained in 28 patients (24 males and 4 females; mean age, 32 years; age range, 10–62 years) with histologically proved KD in the head and neck.RESULTS:In these 28 patients, CT and MR images demonstrated a total of 52 non-nodal lesions, 1–8 cm in greatest diameter, in the head and neck. The lesions were unilateral in 11 patients and bilateral in 17 patients. Eleven patients had a solitary lesion, and 17 patients had 2–4 lesions. The parotid and/or periparotid area was the most frequent location, with 36 lesions in 23 patients. The margin of the lesions was well-defined in 1 and ill-defined in 51 cases. Compared with the adjacent muscle, the MR signal intensity of all lesions was iso- to slightly hyperintense on T1-weighted images and hyperintense on T2-weighted images. Most of the lesions demonstrated mild or moderate enhancement on postcontrast CT scans and moderate or marked enhancement on postcontrast MR images. MR images also showed tubular signal-intensity voids in 7 of 13 lesions. Associated lymphadenopathy was demonstrated in 23 patients, usually bilaterally.CONCLUSIONS:Multiple ill-defined enhancing masses within and around the parotid gland with associated regional lymphadenopathy are characteristic CT and MR imaging findings of KD in the head and neck.

KD is a rare chronic inflammatory disorder of unknown etiology, characterized by angiolymphoid proliferation with peripheral eosinophilia and elevated serum IgE. The disease has a predilection for the head and neck and typically occurs in young Asian males.^1,2 Although it was first described in the Chinese literature in 1937 under the designation of “eosinophilic hyperplastic lymphogranuloma,” it was not until 1948 that the disease to become widely known as KD when Kimura and Ishikawa³ reported it in the Japanese literature.⁴ KD often produces subcutaneous tumorlike nodules with frequently associated involvement of the major salivary gland and regional lymph nodes.⁵Although the clinical and histopathologic findings of KD have been well described in the literature, only a few reports have dealt with its radiologic findings, and generally as case reports or small case series.^6–15 The purpose of this study was to describe the CT and MR imaging findings of histologically proved KD involving the head and neck in 28 patients. To our knowledge, this is the largest imaging study of patients with KD of the head and neck.     

Diagnostic Accuracy of Neuroimaging to Delineate Diffuse Gliomas within the Brain: A Meta-Analysis

BACKGROUND:Brain imaging in diffuse glioma is used for diagnosis, treatment planning, and follow-up.PURPOSE:In this meta-analysis, we address the diagnostic accuracy of imaging to delineate diffuse glioma.DATA SOURCES:We systematically searched studies of adults with diffuse gliomas and correlation of imaging with histopathology.STUDY SELECTION:Study inclusion was based on quality criteria. Individual patient data were used, if available.DATA ANALYSIS:A hierarchic summary receiver operating characteristic method was applied. Low- and high-grade gliomas were analyzed in subgroups.DATA SYNTHESIS:Sixty-one studies described 3532 samples in 1309 patients. The mean Standard for Reporting of Diagnostic Accuracy score (13/25) indicated suboptimal reporting quality. For diffuse gliomas as a whole, the diagnostic accuracy was best with T2-weighted imaging, measured as area under the curve, false-positive rate, true-positive rate, and diagnostic odds ratio of 95.6%, 3.3%, 82%, and 152. For low-grade gliomas, the diagnostic accuracy of T2-weighted imaging as a reference was 89.0%, 0.4%, 44.7%, and 205; and for high-grade gliomas, with T1-weighted gadolinium-enhanced MR imaging as a reference, it was 80.7%, 16.8%, 73.3%, and 14.8. In high-grade gliomas, MR spectroscopy (85.7%, 35.0%, 85.7%, and 12.4) and ¹¹C methionine–PET (85.1%, 38.7%, 93.7%, and 26.6) performed better than the reference imaging.LIMITATIONS:True-negative samples were underrepresented in these data, so false-positive rates are probably less reliable than true-positive rates. Multimodality imaging data were unavailable.CONCLUSIONS:The diagnostic accuracy of commonly used imaging is better for delineation of low-grade gliomas than high-grade gliomas on the basis of limited evidence. Improvement is indicated from advanced techniques, such as MR spectroscopy and PET.

Diffuse gliomas are the most common primary brain tumors in adults, with an annual incidence of approximately 6 per 100,000. Despite advances in neurosurgery, radiation therapy, and chemotherapy, gliomas are fatal.¹ Brain imaging is indispensable for diagnosis, treatment planning, evaluation, and follow-up. Although imaging standards to plan resection and radiation therapy vary between institutions and specialists, conventional imaging is in common use, typically consisting of T1-weighted MR imaging before and after gadolinium and T2/FLAIR-weighted imaging for gliomas. Of these conventional sequences, T2/FLAIR-weighted imaging is often considered as a reference for low-grade gliomas, and T1-weighted gadolinium-enhanced imaging, for high-grade gliomas in neurosurgical planning, combined with T2-weighted imaging in radiation therapy planning.^2,3Compared with other cancer types, accurate delineation of gliomas within the brain for treatment planning is particularly important due to the proximity of eloquent brain structures, which are vulnerable to surgery and radiation therapy.⁴ Conversely, more extensive resections and boosted radiation therapy correlate with longer survival.^5–7 At the same time, clinical observations challenge the diagnostic accuracy of current imaging protocols: Gliomas recur even after a radiologically complete resection,^8,9 and glioma cells have been detected outside MR imaging abnormalities.^10,11 Brain imaging techniques, such as multivoxel spectroscopy and PET, were developed to improve tumor grading and delineation.^12,13Inherent in any regional treatment, such as surgery and radiation therapy, is the need to delineate a target volume, which mandates a dichotomous classification into tumor and normal tissue. Low- and high-grade gliomas have different treatment strategies and prognosis, while both are characterized by diffuse tumor infiltration. This supports our pooled analysis for diffuse glioma in addition to subgroup analysis by glioma grade. More accurate glioma delineation may improve the consistency between treatment results and survival. For instance, more accurate delineation may serve to identify patients eligible for more aggressive surgery than would have been considered on the basis of conventional imaging and may identify patients with glioma infiltration beyond meaningful surgical therapy so that useless and possibly harmful resections can be avoided.The diagnostic accuracy of imaging techniques to delineate gliomas has not been systematically addressed, to our knowledge. In this meta-analysis, we estimate and compare the diagnostic accuracies of conventional imaging techniques and advanced MR imaging and PET to delineate newly diagnosed diffuse gliomas within brain tissue in adults.     

Osteoradionecrosis after Radiation Therapy for Head and Neck Cancer: Differentiation from Recurrent Disease with CT and PET/CT Imaging

BACKGROUND AND PURPOSE:Our aim was to compare the CT and PET/CT imaging features of osteoradionecrosis with those of recurrent disease after treatment of head and neck malignancy.MATERIALS AND METHODS:We retrospectively reviewed maxillofacial and neck CT scans obtained for suspected osteoradionecrosis or tumor recurrence for the presence of the following: 1) discrete solid mass, 2) cystic mass, 3) interruption of the bony cortex, 4) bony fragmentation, 5) bony trabecular loss, 6) intraosseous gas, and 7) bony sclerosis. Trabecular bone loss was further categorized as permeative (<75% loss of trabecula) or lucent (>75% loss). PET/CT studies performed for suspected osteoradionecrosis or tumor recurrence were evaluated for mean standard uptake value and maximum standard uptake value.RESULTS:Ten maxillofacial CT, 53 neck CT, and 23 PET/CT studies were performed in 63 patients. Osteoradionecrosis was diagnosed by pathology or imaging stability in 46 patients, and tumor recurrence, in 17 patients. Bony sclerosis was found to be significantly more prevalent in osteoradionecrosis and was never seen with tumor recurrence (P = .013). Patients with tumor recurrence were more likely to have a solid (P < .001) or cystic mass (P = .025), which was rare in osteoradionecrosis. While patients with tumor recurrence had significantly higher mean standard uptake values and maximum standard uptake values, there was significant overlap in mean standard uptake values and maximum standard uptake values between the 2 groups.CONCLUSIONS:There is significant overlap of standard uptake values in patients with osteoradionecrosis and tumor recurrence. CT findings provide more reliable diagnostic tools, with a solid or cystic mass strongly associated with tumor recurrence and bony sclerosis seen only with osteoradionecrosis.

Osteoradionecrosis (ORN), often with coexistent osteomyelitis, is a serious and often debilitating complication of radiation therapy for head and neck neoplasms. The mandible is the most common site of ORN due to its tenuous blood supply,^1–3 though ORN can be seen in almost any bone within a radiated field. The primary factor implicated in the pathogenesis of ORN is the amount of radiation given to the affected bone, with both early (<2 years from radiation) and late onset ORN (>2 years from radiation) seen.⁴ There is a wide range of incidence of mandibular ORN reported, ranging from 5% to 22%, with more recent studies showing a decreased incidence, presumably attributable to increasing awareness and to improvements in preventive care and radiation techniques.^5–9Patients are often referred for imaging to evaluate the extent of clinically suspected ORN, and, at the same time, to assess potential tumor recurrence. Multiple previous reports have characterized the imaging findings of ORN,^10–14 namely soft-tissue thickening and enhancement, cortical bone erosion, trabecular disorganization, and bone fragmentation. All these findings can be seen in tumor recurrence, however, making the imaging differentiation of these 2 entities quite challenging.We compared the relative frequency of CT and PET/CT findings of ORN and tumor recurrence to find patterns that might allow reliable differentiation of one entity from the other.     

Repeated Head CT in the Neurosurgical Intensive Care Unit: Feasibility of Sinogram-Affirmed Iterative Reconstruction–Based Ultra-Low-Dose CT for Surveillance

BACKGROUND AND PURPOSE:Patients in the neurosurgical intensive care unit undergo multiple head CT scans, resulting in high cumulative radiation exposures. Our aim was to assess the acceptability of a dedicated, special-purpose sinogram-affirmed iterative reconstruction–based ultra-low-dose CT protocol for neurosurgical intensive care unit surveillance head CT examinations, comparing image quality with studies performed with our standard-of-care sinogram-affirmed iterative reconstruction low-dose CT and legacy filtered back-projection standard-dose CT protocols.MATERIAL AND METHODS:A retrospective analysis was performed of 54 head CT examinations: ultra-low-dose CT (n = 22), low-dose CT (n = 12), and standard-dose CT (n = 20) in 22 patients in the neurosurgical intensive care unit. Standard-dose CT was reconstructed by using filtered back-projection on a Somatom Sensation 64 scanner. Ultra-low-dose CT and ultra-low-dose CT examinations were performed on a Siemens AS+128 scanner with commercially available sinogram-affirmed iterative reconstruction. Qualitative and quantitative parameters, including image quality and dose, were evaluated.RESULTS:Sinogram-affirmed iterative reconstruction ultra-low-dose CT represented a 68% lower dose index volume compared with filtered back-projection standard-dose CT techniques in the same patients while maintaining similar quality and SNR levels. Sinogram-affirmed iterative reconstruction low-dose CT offered higher image quality than filtered back-projection standard-dose CT (P < .05) with no differences in SNR at a 24% lower dose index volume. Compared with low-dose CT, ultra-low-dose CT had significantly lower SNR (P = .001) but demonstrated clinically satisfactory measures of image quality.CONCLUSIONS:In this cohort of patients in the neurosurgical intensive care unit, dedicated ultra-low-dose CT for surveillance head CT imaging led to a significant dose reduction while maintaining adequate image quality.

CT by using iterative reconstruction (IR), an alternative to legacy filtered back-projection (FBP), is now ubiquitously available. IR methods loop iteratively through the image reconstruction, reducing noise, with each pass permitting the use of lower levels of ionizing radiation while preserving acceptable image quality.^1,2 IR methods have been successfully applied in cardiovascular,^3,4 thoracic,^5–8 abdominal,^9,10 and head CT applications.^11–14 This study used a commercially available advanced IR technique, sinogram-affirmed iterative reconstruction. Sinogram-Affirmed Iterative Reconstruction (SAFIRE) is a raw data and image domain–based¹⁵ noise-modeling technique with 5 user-selectable strength levels. Previous work established the feasibility of SAFIRE for the study of body regions^15–20 and more recently in head CT²¹ applications.Patients in the neurosurgical intensive care unit (NICU) typically undergo multiple head CT examinations, resulting in high cumulative radiation exposures. In this study, we evaluated radiation dose and image quality of head CTs obtained with a NICU-designated ultra-low-dose (ULDCT) protocol (120 dose-modulated effective milliampere-second), with a dose index volume (CTDI_vol) approximately 80% below the recommended reference level in the current American College of Radiology guidelines.²² We compared these studies with our standard-of-care low-dose (LDCT) IR protocol (290 dose-modulated effective mAs), also SAFIRE-based, and with our legacy standard-dose (SDCT) FBP protocol (350 fixed milliampere-second). To our knowledge, the use of SAFIRE to support ultra-low-dose head CT for the repeated, approximately daily surveillance examinations in the vulnerable NICU population has not been reported.     

Diffusion-Weighted Imaging of the Head and Neck in Healthy Subjects: Reproducibility of ADC Values in Different MRI Systems and Repeat Sessions

BACKGROUND AND PURPOSE:DWI is typically performed with EPI sequences in single-center studies. The purpose of this study was to determine the reproducibility of ADC values in the head and neck region in healthy subjects. In addition, the reproducibility of ADC values in different tissues was assessed to identify the most suitable reference tissue.MATERIALS AND METHODS:We prospectively studied 7 healthy subjects, with EPI and TSE sequences, on 5 MR imaging systems at 3 time points in 2 institutions. ADC maps of EPI (with 2 b-values and 6 b-values) and TSE sequences were compared. Mean ADC values for different tissues (submandibular gland, sternocleidomastoid muscle, spinal cord, subdigastric lymph node, and tonsil) were used to evaluate intra- and intersubject, intersystem, and intersequence variability by using a linear mixed model.RESULTS:On 97% of images, a region of interest could be placed on the spinal cord, compared with 87% in the tonsil. ADC values derived from EPI-DWI with 2 b-values and calculated EPI-DWI with 2 b-values extracted from EPI-DWI with 6 b-values did not differ significantly. The standard error of ADC measurement was the smallest for the tonsil and spinal cord (standard error of measurement = 151.2 × 10⁻⁶ mm/s² and 190.1 × 10⁻⁶ mm/s², respectively). The intersystem difference for mean ADC values and the influence of the MR imaging system on ADC values among the subjects were statistically significant (P < .001). The mean difference among examinations was negligible (ie, <10 × 10⁻⁶ mm/s²).CONCLUSIONS:In this study, the spinal cord was the most appropriate reference tissue and EPI-DWI with 6 b-values was the most reproducible sequence. ADC values were more precise if subjects were measured on the same MR imaging system and with the same sequence. ADC values differed significantly between MR imaging systems and sequences.

Almost 3% of all malignancies are head and neck cancer, 95% of which are squamous cell carcinomas.¹ MR imaging is one of the modalities used in the work-up of patients with head and neck cancer.² DWI is an MR imaging technique by which diffusion properties of water can be quantified as an ADC value.³ Changes in ADC are inversely correlated with changes in cellularity.⁴ In tissues with high cellularity, diffusion of extracellular water in particular is limited by cell membranes, which give low ADC values. In tissues with low cellularity, when diffusion is facilitated (eg, in edematous or necrotic tissue), ADC values are high.Indications for DWI in head and neck cancer include tissue characterization of primary tumors and nodal metastases, prediction and monitoring of treatment response after chemotherapy or radiation therapy, and differentiation of radiation changes and residual or recurrent disease.⁵Neither the optimal DWI sequence for assessment of the head and neck region nor its reproducibility has been clearly established, to our knowledge. DWI can be performed with either EPI or TSE sequences, of which the EPI sequence is most commonly used in the head and neck area.^6,7 On EPI-DWI, more malignant lesions can be detected and lesion delineation is facilitated. However, the interobserver agreement of ADC values is reported to be higher on TSE-DWI, probably due to the frequent occurrence of artifacts and geometric distortions in EPI-DWI.⁸Currently the use of DWI in head and neck imaging is mostly confined to research protocols and advanced academic centers. Before DWI can be used in multicenter studies, its reproducibility across different centers and MR imaging systems should be validated.⁹ ADC values may be affected by the selected technique and MR imaging system (eg, due to differences in gradient systems, coils, pulse-sequence designs, imaging parameters, and artifacts related to susceptibility effects or eddy currents).¹⁰ Information on variance is needed.¹¹ Furthermore, the use of reference tissues might help ascertain the variability among different MR imaging systems and could potentially help correct for differences in ADC values among MR imaging systems.The purpose of this prospective study was to determine the reproducibility of ADC values in the head and neck region obtained from DWI on the basis of both EPI and TSE sequences in repeated measurement on different MR imaging systems in healthy subjects. In addition, we assessed which tissue shows the highest reproducibility in ADC values, so that it could function as a reference tissue in future studies.     

Cystlike Lesions as a Late Sequela of Radiotherapy in Pediatric Patients

BACKGROUND AND PURPOSE:The developing nervous system is particularly vulnerable to late adverse effects of cranial radiation therapy, such as leukoencephalopathy, microbleeds, and cavernomas. Cystlike lesions have been rarely described and characterized in the literature. We aimed to characterize cystlike lesions, their risk factors, and association with other late adverse effects.MATERIALS AND METHODS:Children treated for brain tumors during a 30-year period (n = 139) were included. We documented imaging findings, focusing on cystlike lesion development and its relationship with clinical history and other imaging findings. Multivariable analysis was performed using logistic regression and negative binomial regression models.RESULTS:Cystlike lesions developed in 16.5% of patients treated with radiotherapy, with a median of 2 years until the development of the first lesion. For every 4-year age increase, there were 50% decreased odds of developing lesions and a 50% decrease in the average count of lesions. Females demonstrated a 4.00 rate ratio of developing a higher number of lesions. Patients who underwent chemoradiotherapy had 3.20 increased odds of developing cystlike lesions compared with patients with radiation therapy alone. A larger proportion of patients treated with methotrexate (25%) developed cystlike lesions, but this was not statistically significant. Cystlike lesions tended to develop in cerebral locations where leukoencephalopathy was worse. A strong relationship was found between the development of cystlike lesions and leukoencephalopathy severity.CONCLUSIONS:Cystlike lesions are frequent and under-reported late adverse effects of cranial radiation therapy in children. Younger age, chemoradiotherapy, and the severity of leukoencephalopathy represent risk factors for the development of cystlike lesions.

Central nervous system tumors are the most common solid tumors in children, accounting for up to 22% of tumors in patients between 0 and 14 years of age.¹ The 5-year relative cancer survival rate in these patients has been increasing in the past decades.² Childhood cancer therapy causes chronic health problems in almost 75% of survivors, which can become clinically visible several years after treatment and are frequently irreversible and progressive.¹Late adverse effects are related to chemotherapy, radiation therapy (RT), or a combination of both.^1,3,4 These adverse effects of treatment are additive, with a higher disease burden in patients who had more aggressive therapies or were younger at diagnosis.^5,6 The developing nervous system of young children is particularly vulnerable to cancer treatment, especially to the effects of radiation.^4,7,8 One of the chemotherapy agents with more significant CNS adverse effects is methotrexate (MTX). Concomitant brain radiation and young age represent risk factors for MTX-associated adverse effects.^3,4Neuroimaging abnormalities after chemotherapy, RT, or multimodal therapy are described in several studies, ranging from the common leukoencephalopathy (LE), microbleeds, and cavernomas to the rarely described cystlike lesions (CLL).^4,8 In fact, only 3 cohort studies describe these lesions.^9-11 This study aimed to characterize the risk factors and associations of CLL with other late adverse effects.     

Differentiation between Treatment-Induced Necrosis and Recurrent Tumors in Patients with Metastatic Brain Tumors: Comparison among 11C-Methionine-PET,FDG-PET,MR Permeability Imaging,and MRI-ADC—Preliminary Results

BACKGROUND AND PURPOSE:In patients with metastatic brain tumors after gamma knife radiosurgery, the superiority of PET using ¹¹C-methionine for differentiating radiation necrosis and recurrent tumors has been accepted. To evaluate the feasibility of MR permeability imaging, it was compared with PET using ¹¹C-methionine, FDG-PET, and DWI for differentiating radiation necrosis from recurrent tumors.MATERIALS AND METHODS:The study analyzed 18 lesions from 15 patients with metastatic brain tumors who underwent gamma knife radiosurgery. Ten lesions were identified as recurrent tumors by an operation. In MR permeability imaging, the transfer constant between intra- and extravascular extracellular spaces (/minute), extravascular extracellular space, the transfer constant from the extravascular extracellular space to plasma (/minute), the initial area under the signal intensity–time curve, contrast-enhancement ratio, bolus arrival time (seconds), maximum slope of increase (millimole/second), and fractional plasma volume were calculated. ADC was also acquired. On both PET using ¹¹C-methionine and FDG-PET, the ratio of the maximum standard uptake value of the lesion divided by the maximum standard uptake value of the symmetric site in the contralateral cerebral hemisphere was measured (¹¹C-methionine ratio and FDG ratio, respectively). The receiver operating characteristic curve was used for analysis.RESULTS:The area under the receiver operating characteristic curve for differentiating radiation necrosis from recurrent tumors was the best for the ¹¹C-methionine ratio (0.90) followed by the contrast-enhancement ratio (0.81), maximum slope of increase (millimole/second) (0.80), the initial area under the signal intensity–time curve (0.78), fractional plasma volume (0.76), bolus arrival time (seconds) (0.76), the transfer constant between intra- and extravascular extracellular spaces (/minute) (0.74), extravascular extracellular space (0.68), minimum ADC (0.60), the transfer constant from the extravascular extracellular space to plasma (/minute) (0.55), and the FDG-ratio (0.53). A significant difference in the ¹¹C-methionine ratio (P < .01), contrast-enhancement ratio (P < .01), maximum slope of increase (millimole/second) (P < .05), and the initial area under the signal intensity–time curve (P < .05) was evident between radiation necrosis and recurrent tumor.CONCLUSIONS:The present study suggests that PET using ¹¹C-methionine may be superior to MR permeability imaging, ADC, and FDG-PET for differentiating radiation necrosis from recurrent tumors after gamma knife radiosurgery for metastatic brain tumors.

Stereotactic radiosurgery such as gamma knife radiosurgery (GK) and CyberKnife (Accuray, Sunnyvale, California) is an effective method for treating intracranial neoplasms.^1,2 For metastatic tumors of the brain, stereotactic radiosurgery has generally been the main tool used in therapeutic regimens.^3,4 Although stereotactic radiosurgery is an effective treatment method, it has a risk of radiation necrosis. Radiation necrosis after stereotactic radiosurgery for metastatic tumors of the brain is more common than previously reported.^5,6 It generally occurs 3–12 months after therapy⁷ and often resembles recurrent tumors on conventional imaging techniques, such as MR imaging,^8–11 CT,¹² and SPECT.¹³ Differentiating radiation necrosis and recurrent tumor is extremely important because of the different treatment implications. Histologic examination from a biopsy or resection may aid in differentiating these 2 events. However, a noninvasive method is needed for diagnosing whether a contrast-enhanced lesion with surrounding edema on conventional MR imaging is radiation necrosis or a recurrent tumor.Advanced MR imaging techniques including MR spectroscopy,¹⁴ DWI,¹⁵ and DTI¹⁶ have been used for differentiation of radiation necrosis and recurrent tumors. The CTP technique has also been reported as promising in this field.¹⁷ CTP has the advantage of using widely available CT scanners, though x-ray exposure and administration of ionizing contrast material limit the clinical use. In radionuclide studies, SPECT with ²⁰¹TI-chloride,¹⁸ technetium Tc99m-sestamibi,^{19 123}I-alfa-methyl-L-tyrosine,²⁰O-(2-[¹⁸F]-fluoroethyl)-L-tyrosine (FET-PET),^21,22 6-[¹⁸F]-fluoro-L-dopa (FDOPA),²³ and FDG-PET^24–26 have been reported to differentiate between radiation necrosis and recurrent tumors. Compared with those studies, the superiority of PET with ¹¹C-methionine (MET) for differentiating radiation necrosis and recurrent tumors has been accepted because of the high sensitivity and specificity.^27–31 However, MET-PET is not widely available. Dynamic contrast-enhanced MR imaging with a contrast agent has been used to characterize brain tumors^32,33 and stroke.³⁴MR permeability imaging with dynamic contrast-enhanced–MR imaging based on the Tofts model³⁵ has recently been developed and used for evaluating cerebrovascular diseases,³⁶ brain tumors,^37–39 nasopharyngeal carcinomas,^40,41 rectal carcinomas,⁴² and prostate carcinomas.⁴³ The endothelial permeability of vessels in brain tumors can be quantitatively acquired with MR permeability imaging. The vascular microenvironment in tumors can be measured by parameters such as influx transfer constant, reverse transfer constant, and the extravascular extracellular space.⁴⁴ These parameters may reflect tissue characteristics including vascular density, a damaged blood-brain barrier, vascularity, and neoangiogenesis.⁴⁴ If the feasibility of MR permeability imaging for differentiating radiation necrosis and recurrent tumors could be demonstrated, this technique may contribute to the management of patients after stereotactic radiosurgery and conventional radiation therapy because MR permeability imaging is widely available. To evaluate the feasibility of MR permeability imaging in the present study, we compared it with MET-PET, FDG-PET, and DWI for differentiating radiation necrosis from recurrent tumor after GK in patients with metastatic brain tumors.     

Diagnostic Performance of Ultrafast Brain MRI for Evaluation of Abusive Head Trauma

BACKGROUND AND PURPOSE:MR imaging with sedation is commonly used to detect intracranial traumatic pathology in the pediatric population. Our purpose was to compare nonsedated ultrafast MR imaging, noncontrast head CT, and standard MR imaging for the detection of intracranial trauma in patients with potential abusive head trauma.MATERIALS AND METHODS:A prospective study was performed in 24 pediatric patients who were evaluated for potential abusive head trauma. All patients received noncontrast head CT, ultrafast brain MR imaging without sedation, and standard MR imaging with general anesthesia or an immobilizer, sequentially. Two pediatric neuroradiologists independently reviewed each technique blinded to other modalities for intracranial trauma. We performed interreader agreement and consensus interpretation for standard MR imaging as the criterion standard. Diagnostic accuracy was calculated for ultrafast MR imaging, noncontrast head CT, and combined ultrafast MR imaging and noncontrast head CT.RESULTS:Interreader agreement was moderate for ultrafast MR imaging (κ = 0.42), substantial for noncontrast head CT (κ = 0.63), and nearly perfect for standard MR imaging (κ = 0.86). Forty-two percent of patients had discrepancies between ultrafast MR imaging and standard MR imaging, which included detection of subarachnoid hemorrhage and subdural hemorrhage. Sensitivity, specificity, and positive and negative predictive values were obtained for any traumatic pathology for each examination: ultrafast MR imaging (50%, 100%, 100%, 31%), noncontrast head CT (25%, 100%, 100%, 21%), and a combination of ultrafast MR imaging and noncontrast head CT (60%, 100%, 100%, 33%). Ultrafast MR imaging was more sensitive than noncontrast head CT for the detection of intraparenchymal hemorrhage (P = .03), and the combination of ultrafast MR imaging and noncontrast head CT was more sensitive than noncontrast head CT alone for intracranial trauma (P = .02).CONCLUSIONS:In abusive head trauma, ultrafast MR imaging, even combined with noncontrast head CT, demonstrated low sensitivity compared with standard MR imaging for intracranial traumatic pathology, which may limit its utility in this patient population.

The incidence of abusive head trauma (AHT) in the United States from 2000 to 2009 was 39.8 per 100,000 children younger than 1 year of age and 6.8 per 100,000 children 1 year of age.¹ The outcomes of patients with AHT are worse than those of children with accidental traumatic brain injury, including higher rates of mortality and permanent disability from neurologic impairment.^2–5 The diagnosis of AHT is frequently not recognized when affected patients initially present to a physician, and up to 28% of children with a missed AHT diagnosis may be re-injured, leading to permanent neurologic damage or even death.⁶ Because neuroimaging plays a central role in AHT, continued improvement in neuroimaging is necessary.Common neuroimaging findings of AHT include intracranial hemorrhage, ischemia, axonal injury, and skull fracture, with advantages and disadvantages for both CT and MR imaging for the detection of AHT.⁷ A noncontrast head CT (nHCT) is usually the initial imaging study in suspected AHT due to its high sensitivity for the detection of acute hemorrhage and fracture and the high level of accessibility from the emergency department, and it can be performed quickly and safely without the need for special monitoring equipment.^8,9 The disadvantages of CT include ionizing radiation, particularly in children, and the reduced sensitivity in detecting microhemorrhages, axonal injury, and acute ischemia compared with MR imaging.¹⁰MR imaging is frequently performed in AHT and adds additional information in 25% of all children with abnormal findings on the initial CT scan.¹¹ Brain MR imaging can also be useful for identifying bridging vein thrombosis, differentiating subdural fluid collections from enlarged subarachnoid spaces, characterizing the signal of subdural blood, and demonstrating membrane formation within subdural collections.^12–16 Brain MR imaging findings have correlated with poor outcomes associated with findings on diffusion-weighted imaging and susceptibility-weighted imaging in AHT; however, disadvantages of MR imaging continue to include the need for sedation in children and compatible monitoring equipment.^17–22 Although there is greater accessibility of CT compared with MR imaging, the availability of MR imaging is relatively high and imaging techniques that allow neuroimaging in patients with potential AHT without sedation would be valuable, particularly given the potential adverse effects of sedation on the developing brain.^23,24A potential solution for diagnostic-quality brain MR imaging without sedation in AHT is the use of ultrafast MR imaging (ufMRI) sequences, also termed “fast MR imaging,” “quick MR imaging,” or “rapid MR imaging.” Ultrafast MR imaging uses pulse sequences that rapidly acquire images, potentially reducing motion artifacts and the need for sedation. ufMRI has been most commonly used in pediatric neuroradiology for the evaluation of intracranial shunts in children with hydrocephalus, and most of the reported ufMRI brain protocols include only multiplanar T2-weighted HASTE sequences.^25–34 Consequently, previously reported limitations of ufMRI in detecting intracranial hemorrhage is primarily due to the lack of blood sensitive sequences.³⁵Recently, an ufMRI protocol incorporating sequences in addition to T2 sequences has been reported in pediatric patients with trauma.³⁶ This study did not compare findings with those of a standard MR imaging (stMRI) and included a wider age range of pediatric patients, so the value of ufMRI in pediatric abusive head trauma remains uncertain.³⁶ Therefore, the purpose of our study was to evaluate an ufMRI brain protocol performed without sedation for feasibility in terms of scanning time and diagnostic value as well as diagnostic accuracy compared with nHCT and stMRI of the brain for the detection of intracranial traumatic pathology in patients with suspected AHT.     

Ossification of the Vascular Pedicle in Microsurgical Fibular Free Flap Reconstruction of the Head and Neck

BACKGROUND AND PURPOSE:The fibular free flap, often used for osseous reconstruction following extirpation of head and neck malignancies, has been associated with heterotopic periosteal ossification. We aimed to determine the frequency and radiologic characteristics of this process and describe its clinical correlates.MATERIALS AND METHODS:Surgical records for 2 years and neck imaging reports for 10 years were evaluated to identify patients with fibular free flap reconstruction and CT and/or PET/CT imaging available for review. The images were evaluated for the quality, type, and contour of ossification, and the reports were reviewed for associated clinical findings and radiologic impressions.RESULTS:Of 32 patients with posttreatment CT or PET/CT imaging, ossification was evident in 16 patients (50%) as early as 1 month following fibular free flap reconstruction. In 8 patients, it mimicked a new bone; in 5, it appeared as linear attenuation; in 2, as multiple short segments; and in 1 patient, a mixed appearance was found. No associated FDG uptake was seen on PET/CT. On MR imaging, these findings were extremely subtle or not appreciable. In only 1 patient was new bone associated with symptoms.CONCLUSIONS:Periosteal ossification of the vascular pedicle is commonly evident on CT following fibular free flap, even as early as 1 month after reconstruction, though the finding is not typically noted on imaging. While symptoms related to new bone are uncommon, they may mimic recurrent tumor. The location and pattern of ossification and the absence of a soft-tissue mass or FDG uptake are useful distinguishing imaging features.

Microsurgical free flaps are commonly used for reconstruction of surgical defects in patients with head and neck malignancies. Such flaps allow cosmetic and functional improvement following resection of neoplasms, and they may additionally provide protection for vulnerable tissues before radiation therapy.^1,2 Following resection of all or part of the mandible or maxilla, osteocutaneous flaps may be used for reconstruction, with the most frequent choice being the fibular free flap (FFF).² After fibula bone harvest, the distal aspect of the bone is osteotomized and contoured to fit the facial bone defect, while the vascular pedicle is carefully preserved and then anastomosed to available neck vessels in either the ipsilateral or contralateral neck.³Posttreatment imaging evaluation after free flap reconstruction is often complex, with loss of reliably symmetric anatomic landmarks and altered signal intensity (MR imaging) or attenuation (CT) of both native and flap tissues, particularly with denervation changes in the muscular component of myogenous flaps. Concurrently, the clinical examination after reconstruction can be difficult, both in the early postoperative edematous phase and the more delayed phase, especially when radiation is also delivered.While the imaging features of microsurgical free flaps^4–6 have been described and imaging features suggesting recurrent tumor have also been delineated,^7,8 we have observed an unusual finding on neck CT scans of new bone developing in patients with prior fibular free flap placement. This new bone has been described in the surgical literature, predominantly in case reports, and has been ascribed to heterotopic ossification arising from fibula periosteum, which is preserved as part of the vascular pedicle during microvascular reconstruction.^9–16 It has been described as a potential clinical pitfall, presenting as a new hard neck mass and mimicking recurrent disease. We sought to determine the frequency, timing, and radiologic characteristics of heterotopic ossification after flap placement and the frequency with which it was described in CT, MR imaging, and PET/CT imaging reports or was clinically concerning.     

Radiographic Local Control of Spinal Metastases with Percutaneous Radiofrequency Ablation and Vertebral Augmentation

BACKGROUND AND PURPOSE:Combination radiofrequency ablation and vertebral augmentation is an emerging minimally invasive therapy for patients with metastatic spine disease who have not responded to or have contraindications to radiation therapy. The purpose of this study was to evaluate the rate of radiographic local control of spinal metastases treated with combination radiofrequency ablation and vertebral augmentation.MATERIALS AND METHODS:We retrospectively reviewed our tumor ablation database for all patients who underwent radiofrequency ablation and vertebral augmentation of spinal metastases between April 2012 and July 2014. Tumors treated in conjunction with radiation therapy were excluded. Tumor characteristics, procedural details, and complications were recorded. Posttreatment imaging was reviewed for radiographic evidence of tumor progression.RESULTS:Fifty-five tumors met study inclusion criteria. Radiographic local tumor control rates were 89% (41/46) at 3 months, 74% (26/35) at 6 months, and 70% (21/30) at 1 year after treatment. Clinical follow-up was available in 93% (51/55) of cases. The median duration of clinical follow-up was 34 weeks (interquartile range, 15–89 weeks), during which no complications were reported and no patients had clinical evidence of metastatic spinal cord compression at the treated levels.CONCLUSIONS:Combination radiofrequency ablation and vertebral augmentation appears to be an effective treatment for achieving local control of spinal metastases. A prospective clinical trial is now needed to replicate these results.

Metastatic spine disease affects 5%–10% of patients with cancer.¹ Approximately 90% of symptomatic patients present with pain, which is most commonly due to biochemical stimulation of endosteal nociceptors, tumor mass effect, and/or associated pathologic fracture.² These patients are also at risk for metastatic spinal cord compression, which occurs in 10%–20% of patients and is most often due to posterior extension of vertebral body tumor.^3,4 The resulting pain and neurologic deficits are associated with decreased quality of life and shortened life expectancy.⁵ Therefore, the goals of treatment are both pain palliation and local tumor control.Radiation therapy is the standard of care for pain palliation and local control of spinal metastases, but it has several important limitations. First, certain tumor histologies respond less favorably to radiation therapy, particularly non-small cell lung cancer, renal cell carcinoma, melanoma, and sarcoma.⁶ Second, radiation therapy of spinal metastases is limited by the cumulative tolerance of the spinal cord, which often precludes retreatment of recurrent disease or progressive disease at adjacent vertebral levels.⁷ Third, radiation therapy excludes patients from certain systemic chemotherapy clinical trials.Combination radiofrequency ablation (RFA) and vertebral augmentation is an emerging minimally invasive therapy for patients with metastatic spine disease who have not responded to or have contraindications to radiation therapy. An ablation probe is percutaneously placed into the tumor, and high-frequency alternating current is passed through an electrode at the probe tip, generating frictional heating and necrosis of adjacent tissue.⁸ Cement is then instilled through the same percutaneous cannula to stabilize or prevent associated pathologic fracture.^9,10 The tandem procedure can be performed in an outpatient setting with the patient under conscious sedation, requires minimal recovery, and does not hinder or delay adjuvant therapies such as radiation or systemic chemotherapy. Multiple case series have shown decreased pain scores after RFA and vertebral augmentation of spinal metastases,^11–15 but evidence that percutaneous therapy achieves local tumor control is limited to case reports and small case series without internal controls.^13,14 The purpose of this study was to retrospectively evaluate the rate of radiographic local control of spinal metastases treated with combination RFA and vertebral augmentation at a National Cancer Institute–Designated Cancer Center.     

MRI Texture Analysis Predicts p53 Status in Head and Neck Squamous Cell Carcinoma

BACKGROUND AND PURPOSE:Head and neck cancer is common, and understanding the prognosis is an important part of patient management. In addition to the Tumor, Node, Metastasis staging system, tumor biomarkers are becoming more useful in understanding prognosis and directing treatment. We assessed whether MR imaging texture analysis would correctly classify oropharyngeal squamous cell carcinoma according to p53 status.MATERIALS AND METHODS:A cohort of 16 patients with oropharyngeal squamous cell carcinoma was prospectively evaluated by using standard clinical, histopathologic, and imaging techniques. Tumors were stained for p53 and scored by an anatomic pathologist. Regions of interest on MR imaging were selected by a neuroradiologist and then analyzed by using our 2D fast time-frequency transform tool. The quantified textures were assessed by using the subset-size forward-selection algorithm in the Waikato Environment for Knowledge Analysis. Features found to be significant were used to create a statistical model to predict p53 status. The model was tested by using a Bayesian network classifier with 10-fold stratified cross-validation.RESULTS:Feature selection identified 7 significant texture variables that were used in a predictive model. The resulting model predicted p53 status with 81.3% accuracy (P < .05). Cross-validation showed a moderate level of agreement (κ = 0.625).CONCLUSIONS:This study shows that MR imaging texture analysis correctly predicts p53 status in oropharyngeal squamous cell carcinoma with ∼80% accuracy. As our knowledge of and dependence on tumor biomarkers expand, MR imaging texture analysis warrants further study in oropharyngeal squamous cell carcinoma and other head and neck tumors.

Head and neck cancer is the sixth most common cancer worldwide,¹ with squamous cell carcinoma accounting for approximately 90% of all cases. Most head and neck squamous cell carcinoma (HNSCC) occurs in the oral cavity, oropharynx, and larynx. Alcohol and tobacco consumption and prior infection with human papillomavirus are the major risk factors associated with the development of head and neck squamous cell carcinoma. Oropharyngeal squamous cell carcinoma is of particular interest because its incidence is increasing, particularly among younger, nonsmoking patients.²Accurate staging of HNSCC is essential for treatment planning and prognostication, and a standard tool used for staging is the American Joint Committee on Cancer Tumor, Node, Metastasis staging system, currently in its seventh revision.³ As we learn more about tumor biology, however, it is clear that this staging system does not fully predict clinical behavior and prognosis. Our knowledge of head and neck cancer pathogenesis has rapidly increased, and better understanding of molecular mechanisms holds the promise of discovering predictive and prognostic biomarkers that might be helpful in the management of HNSCC.⁴ The tumor suppressor p53 plays an important role in conserving genomic stability.⁵ p53 facilitates DNA repair by regulating the cell cycle and has a role in preventing cancer emergence.^6,7 Mutations in the gene encoding the p53 protein, TP53, occur in almost 50% of all cancers.^8,9 In most of HNSCC, mutation and inactivation of p53 is an essential and early event in neoplastic transformation, and TP53 mutations are associated with poor prognosis in HNSCC.^10–12 A landmark prospective study classified TP53 gene mutations on the basis of their effect on p53 protein structure.¹³ Broadly, disruptive mutations disturb the formation of p53-DNA complexes, while nondisruptive mutations have little effect on the association between p53 and DNA. The study reported a significant association between the presence of TP53 disruptive mutations and worse overall survival in surgically treated HNSCC compared with both nondisruptive TP53 mutations and wild-type TP53.¹³ A recent study has also implicated disruptive mutations in TP53 leading to radiation-treatment failure.¹⁴Medical imaging plays a critical role in the assessment of many head and neck tumors, and both CT and MR imaging have important roles in the anatomic evaluation of HNSCC.^15–18 In addition to anatomic details, the analysis of MR images provides additional metabolic and biologic information in tumors.¹⁹ Mathematic techniques that quantify image characteristics have been applied to a vast array of pathologies, from multiple sclerosis,²⁰ attention deficit/hyperactivity disorder,²¹ and Alzheimer disease²² to breast cancer,²³ cervical cancer,²⁴ and brain tumors.²⁵ Studies in glioblastoma have shown that there is a correlation between the methylation of O6-methylguanine-DNA methyltransferase and MR imaging features.²⁶ Levner et al²⁷ extracted texture features from MR images by using spatial frequency analysis and the Stockwell transform (ST) representation²⁸ and fed these characteristics into a neural network to predict the methylation status with an average accuracy of 87.7%.²⁷ Brown et al²⁵ also extracted ST texture features from brain MR images to find that codeletion of chromosomes 1p and 19q, a marker of good prognosis in oligodendroglioma brain cancer, could be predicted with 94% accuracy. These studies suggest that differences in tumor-tissue composition react with MR imaging signals differently, thus affecting texture features.Yu et al²⁹ looked at differentiating tissues by using texture characterization on FDG-PET/CT images in head and neck cancers. We explored the use of ST texture features on MR images with a machine-learning technique to objectively differentiate head and neck tumors by p53 status. We hypothesized that MR image analysis could successfully discriminate p53-positive and -negative tumors.     

Advanced Modeled Iterative Reconstruction in Low-Tube-Voltage Contrast-Enhanced Neck CT: Evaluation of Objective and Subjective Image Quality

BACKGROUND AND PURPOSE:Dose-saving techniques in neck CT cause increased image noise that can be counteracted by iterative reconstruction. Our aim was to evaluate the image quality of advanced modeled iterative reconstruction (ADMIRE) in contrast-enhanced low-tube-voltage neck CT.MATERIALS AND METHODS:Sixty-one patients underwent 90-kV(peak) neck CT by using third-generation 192-section dual-source CT. Image series were reconstructed with standard filtered back-projection and ADMIRE strength levels 1, 3, and 5. Attenuation and noise of the sternocleidomastoid muscle, internal jugular vein, submandibular gland, tongue, subscapularis muscle, and cervical fat were measured. Signal-to-noise and contrast-to-noise ratios were calculated. Two radiologists assessed image noise, image contrast, delineation of smaller structures, and overall diagnostic acceptability. Interobserver agreement was calculated.RESULTS:Image noise was significantly reduced by using ADMIRE compared with filtered back-projection with the lowest noise observed in ADMIRE 5 (filtered back-projection, 9.4 ± 2.4 Hounsfield units [HU]; ADMIRE 1, 8.3 ± 2.8 HU; ADMIRE 3, 6.7 ± 2.0 HU; ADMIRE 5, 5.4 ± 1.7 HU; all, P < .001). Sternocleidomastoid SNR and internal jugular vein–sternocleidomastoid contrast-to-noise ratios were significantly higher for ADMIRE with the best results in ADMIRE 5 (all, P < .001). Subjective image quality and image contrast of ADMIRE 3 and 5 were consistently rated better than those for filtered back-projection and ADMIRE 1 (all, P < .001). Image noise was rated highest for ADMIRE 5 (all, P < .005). Delineation of smaller structures was voted higher in all ADMIRE strength levels compared with filtered back-projection (P < .001). Global interobserver agreement was good (0.75).CONCLUSIONS:Contrast-enhanced 90-kVp neck CT is feasible, and ADMIRE 5 shows superior objective image quality compared with filtered back-projection. ADMIRE 3 and 5 show the best subjective image quality.

Contrast-enhanced CT is a well-established initial cross-sectional imaging technique for examination of the head and neck region.^1–3 Several strategies have been developed for both radiation dose reduction and improvement of image quality. These typically involve adjusting CT acquisition parameters such as tube voltage, tube current, tube rotation time, pitch, and collimation to the patient body and examined body region.^4–6 The interaction of these parameters is complex, and manual adjustments may result in nondiagnostic images. Thus, commercially available techniques, including tube current modulation,⁷ automatic exposure control,^8,9 automated tube voltage adaptation,^10,11 iterative reconstruction,^12–15 and selective in-plane shielding (thyroid, eye lens, breast, and gonads),¹⁶ have been introduced to support the radiologic technologist, physicist, and radiologist team in developing appropriate CT protocols.Reduced tube voltage can increase contrast-to-noise ratio (CNR) of iodine enhancing soft-tissue structures, while the radiation dose is substantially reduced.⁴ The drawback of an increased image noise in low-tube-voltage examinations can be counteracted by iterative reconstruction, which reduces image noise compared with filtered back-projection (FBP).^12,14 Recently introduced advanced modeled iterative reconstruction (ADMIRE) performs detailed modeling in the projection data domain, resulting in less noise and improved artifact suppression.¹⁷ ADMIRE includes a local signal-to-noise relationship analysis and decomposes the image data into information and noise.¹⁸ Further technical details have been described in recent studies.^14,17,18 Thus, neck CT may potentially be performed with a reduced tube voltage and therefore lower radiation dose without impairing image quality.The purpose of our study was to evaluate the impact of ADMIRE on image quality in low-tube-voltage contrast-enhanced neck CT compared with FBP on a 192-section third-generation dual-source CT (DSCT).     

Does the Addition of a “Black Bone” Sequence to a Fast Multisequence Trauma MR Protocol Allow MRI to Replace CT after Traumatic Brain Injury in Children?

BACKGROUND AND PURPOSE:Head CT is the current neuroimaging tool of choice in acute evaluation of pediatric head trauma. The potential cancer risks of CT-related ionizing radiation should limit its use in children. We evaluated the role of MR imaging, including a “black bone” sequence, compared with CT in detecting skull fractures and intracranial hemorrhages in children with acute head trauma.MATERIALS AND METHODS:We performed a retrospective evaluation of 2D head CT and brain MR imaging studies including the black bone sequence of children with head trauma. Two experienced pediatric neuroradiologists in consensus created the standard of reference. Another pediatric neuroradiologist blinded to the diagnosis evaluated brain MR images and head CT images in 2 separate sessions. The presence of skull fractures and intracranial posttraumatic hemorrhages was evaluated. We calculated the sensitivity and specificity of CT and MR imaging with the black bone sequence in the diagnosis of skull fractures and intracranial hemorrhages.RESULTS:Twenty-eight children (24 boys; mean age, 4.89 years; range, 0–15.5 years) with head trauma were included. MR imaging with the black bone sequence revealed lower sensitivity (66.7% versus 100%) and specificity (87.5% versus 100%) in identifying skull fractures. Four of 6 incorrectly interpreted black bone MR imaging studies showed cranial sutures being misinterpreted as skull fractures and vice versa.CONCLUSIONS:Our preliminary results show that brain MR imaging complemented by a black bone sequence is a promising nonionizing alternative to head CT for the assessment of skull fractures in children. However, accuracy in the detection of linear fractures in young children and fractures of aerated bone remains limited.

CT is the initial neuroimaging technique of choice for the acute evaluation of pediatric head trauma due to its wider availability, lower cost, and short acquisition time. In addition, CT identifyies most traumatic injuries that require urgent treatment and correlates well with clinical scales and outcome.¹ However, CT-related ionizing radiation involves the potential risk of patients developing cancer and strongly argues in favor of alternative neuroimaging techniques such as MR imaging.² The lifetime cancer mortality risk attributable to the radiation from a single CT scan of the head in a 1-year-old child has been estimated as 0.07%. This small risk translates into a large population-level risk, especially because head trauma in children from 0 to 14 years of age accounts for nearly half a million emergency department visits in the United States annually.^3,4MR imaging is a nonionizing technique that provides superior contrast resolution and has a higher sensitivity and specificity for parenchymal lesions compared with CT.^3,4 Especially, advanced MR imaging techniques (DWI, SWI) provide additional information that correlates well with outcome.^5,6 Nonhemorrhagic shear injuries and subtle microhemorrhages are typically seen with higher sensitivity by MR imaging compared with CT. Nevertheless, the role of MR imaging in the acute diagnostic work-up of head trauma in children is still limited.^2,7,8 This limitation may be partially explained by longer acquisition times and the subsequent need for sedation as well as the low sensitivity of MR imaging for skull fractures.^2,8 Recently, black bone MR images have been introduced as a new sequence for the evaluation of structural bony abnormalities such as craniosynostosis.⁹On the basis of the inherent diagnostic quality of the black bone sequence, we aimed to determine whether a trauma brain MR imaging protocol with an included black bone MR image could be an alternative to head CT in the acute work-up of children with head trauma. To address our goal, we compared the diagnostic accuracy of brain MR imaging including the black bone sequence with CT for the detection of skull fractures after traumatic brain injury in children. Images were also studied for coexisting intracranial lesions.