CT Enteroclysis

Computed tomographic (CT) enteroclysis is a hybrid technique that combines the methods of fluoroscopic intubation-infusion small-bowel examinations with that of abdominal CT. The use of multidetector CT technology has made this a versatile examination that has evolved into two distinct technical modifications. CT enteroclysis can be performed by using positive enteral contrast material without intravenous contrast material and neutral enteral contrast material with intravenous contrast material. CT enteroclysis has been shown to be superior to other imaging tests such as peroral small-bowel examinations, conventional CT, and barium enteroclysis, except in the demonstration of early apthous ulcers of Crohn disease. CT enteroclysis is complementary to capsule endoscopy in the elective investigation of small-bowel disease, with a specific role in the investigation of Crohn disease, small-bowel obstruction, and unexplained gastrointestinal bleeding.     

CT angiography

The advent of spiral (helical, volume ) CT has revolutionised the performance of body CT and allowed the development of CT angiography (CTA). CT angiography is a non-invasive method of visualising the vascular system and in some instances can replace conventional angiography. In spiral CT a volume of data is obtained rapidly with no respiratory misregistration at peak vascular opacification following the peripheral injection of contrast. Appropriate timing will ensure that either the venous or arterial tree is visualised and from the volume of data multiple overlapping slices can be obtained to generate 2D and 3D images with no increase in radiation to the patient. CT angiography may be performed as a dedicated study or be undertaken retrospectively using post-processing of data from a conventional diagnostic spiral scan to provide additional information about the vascular tree. When undertaken as a dedicated study CTA is quicker, less invasive and less costly than a conventional angiogram with a decrease in the radiation dose to the patient; however, the spatial resolution is limited with vessels less than 2 mm not visualised and there is no contrast saving. Received: 25 March 1998; Revision received: 16 July 1998; Accepted: 22 July 1998     

Spiral CT vs incremental CT: Is spiral CT superior in imaging of the brain?

The aim of this study was to evaluate image quality of spiral CT of the brain as compared with incremental CT using identical scanning parameters. Incremental or spiral cranial CT was performed on 46 consecutive, randomized patients with non-traumatic disease of the brain on a Siemens (Erlangen, Germany) Somatom Plus 4. Evaluation was done in a randomized blinded way by two experienced radiologists. Different anatomical structures, image noise, and artifacts were scaled 1 (bad) to 4 (very good). Statistical analysis was done using the F-test of variance for partial sums of squares as well as Student's t-test. Incremental CT was superior to spiral CT for evaluation of the internal capsule, supratentorial artifacts, gray/white matter differentiation, and image noise. No statistically significant differences were seen for evaluation of the pons, infratentorial artifacts, and eye muscles. With identical scanning parameters incremental CT is superior to spiral CT in the assessment of small, complex structures in a low-contrast setting. No differences are seen for larger structures or small structures in a medium-contrast range. Artifacts localized close to the skull in spiral CT can easily mimic hemorrhage in traumatized patients. Spiral CT should therefore only be used for CT angiography and if 3D reconstructions are needed. Received 19 June 1997; Accepted 6 August 1997     

CT scout view as an essential part of CT reading

Computed tomography scout view is a mode of operating a CT system. It is generally used to prescribe CT slices and to display slice locations rather than for direct diagnosis. However, we found that a careful study of CT scout view can contribute significantly to the diagnosis. We show seven abdominal, two chest and two head CT, where the study of CT scout view allowed diagnoses to be made that were not readily apparent from the axial slices.     

Multislice CT angiography

The introduction of multislice CT into clinical radiology constitutes a quantum leap that significantly widens the scope of vascular CT imaging. The advances over conventional spiral CT have been quantitative, mainly in terms of increased image acquisition speed which provides unprecedented volume coverage and spatial resolution. Moreover, significant technical innovations, such as cardiac scanning capabilities, have brought about a qualitative shift towards applications that were thought to be beyond the scope of CT imaging. This way multislice CT offers a wealth of new opportunities for quickly and accurately diagnosing suspected vascular disease in all organ systems; however, as we move towards faster and faster image acquisition techniques, we are also facing new challenges that require development of novel strategies in order to take full advantage of the increased capabilities of multislice CT in its current form and future generations of CT scanners.     

Pediatric CT angiography

Advances in CT technology are having profound impact on imaging children and have made CT angiography possible even in neonates. Even with the tiny anatomy of neonates, small volumes of contrast material, and small venous access catheters, successful CT angiography can be performed with attention to detail. Meticulous attention to patient preparation, the proper selection of technical factors, and optimal delivery of contrast material are crucial. Data post-processing and the creation of 3-D reconstructions are also essential in establishing a correct diagnosis. The applications of CT angiography are different in children than in adults and most applications in children involve assessment of congenital and postoperative vascular and cardiac diseases. The use of CT angiography offers the opportunity to eliminate the long periods of sedation associated with MR and reduce the radiation exposure associated with conventional angiography. Generally, the benefits of CT angiography in children outweigh the risk, namely that of radiation exposure. However, care must still be taken to minimize the radiation exposure.     

Pediatric CT angiography

Advances in CT technology are having profound impact on imaging children and have made CT angiography possible even in neonates. Even with the tiny anatomy of neonates, small volumes of contrast material, and small venous access catheters, successful CT angiography can be performed with attention to detail. Meticulous attention to patient preparation, the proper selection of technical factors, and optimal delivery of contrast material are crucial. Data post-processing and the creation of 3-D reconstructions are also essential in establishing a correct diagnosis. The applications of CT angiography are different in children than in adults and most applications in children involve assessment of congenital and postoperative vascular and cardiac diseases. The use of CT angiography offers the opportunity to eliminate the long periods of sedation associated with MR and reduce the radiation exposure associated with conventional angiography. Generally, the benefits of CT angiography in children outweigh the risk, namely that of radiation exposure. However, care must still be taken to minimize the radiation exposure.     

Limitations of CT during PET/CT.

Our aim was to determine the diagnostic limitations of low-dose, unenhanced CT scans performed for anatomic reference and attenuation correction during PET/CT. METHODS: The Radiology Information System at our oncologic hospital was queried during the 9-mo period from July 2002 to April 2003 for patients with PET/CT scans and diagnostic enhanced CT within 2 wk of each other. One radiologist interpreted the CT portion of the PET/CT (CT(p)) unaware of the PET results and the associated enhanced diagnostic CT (CT(d)). A medical student compared this interpretation with the official report of the CT(d) and listed all discrepancies between reports. A separate radiologist compared CT(p) and CT(d) images and classified true discrepant findings as due to lack of intravenous contrast, arm-position artifact, lack of enteric contrast, low milliamperage (mA), and quality of lung images. RESULTS: Among 100 patients, the most common malignancies were lymphoma (n = 37), cancer of the colorectum (n = 31), and esophageal cancer (n = 15). Among 194 true discrepancies in which findings were missed at CT(p), causes were as follows: (a) lack of intravenous contrast (128/194, 66%), (b) arm-down artifact (17/194, 9%), (c) quality of lung images (26/194, 13%), (d) lack of enteric contrast (15/194, 8%), and (e) low mA (8/194, 4%). Discrepancies were seen most commonly in detecting lymphadenopathy and visceral metastases. CONCLUSION: Most missed findings on the unenhanced CT portion of the PET/CT scans were due to technical factors that could be altered. Discrepant findings would have led to altered management in only 2 patients, suggesting a role for limited repeat imaging to reduce radiation and use of valuable resources.     

CT设备中CT值线性的测量与分析

目的测量CT设备的CT值线性,评价物质材料的CT值（测量值）对其衰减系数μ是否满足线性关系。方法利用Catphan体模对18台CT设备进行测试,计算出CT值线性。结果18台设备中有14台设备的CT值线性达到指标,其余4台则有所偏移。结论（1）有多种因素影响CT值线性,且CT值线性不好会导致图像的伪影。（2）必须定期对CT值线性这项参数进行校正,确保其稳定性,以利于设备的正确诊断。     

Safety and feasibility of a CT protocol for acute stroke: combined CT,CT angiography,and CT perfusion imaging in 53 consecutive patients

By combining non-contrast-enhanced CT imaging, CT perfusion imaging, and cranial-to-chest CT angiography (CTA), the entire cerebrovascular axis can be imaged during acute stroke. To our knowledge, the safety and feasibility of this technique have not been previously reported. In a consecutive series of 53 patients with suspected acute stroke, renal failure was not observed. Median imaging time was 27 minutes (range, 9-67 minutes). Image quality was degraded by motion in 1.3% of vessels studied. Dynamic CT perfusion data were successfully obtained in 52 patients (98% of patients). High-speed, multisection, helical CT scanners allow rapid, safe imaging of the entire neurovascular axis in patients with acute stroke by use of combined CT imaging, CT perfusion imaging, and CTA.     

CT of emphysema

This article focuses on three main topics: (1) the importance of emphysema as a serious respiratory disease, (2) qualitative assessment of emphysema using CT, and (3) the emerging importance of quantitative CT in the evaluation of patients with emphysema for surgery and drug therapy. CT also can identify the major anatomic subtypes of emphysema. CT is critical in the assessment of patients with the potential for lung volume reduction surgery. CT may well be superior to pulmonary function tests in the longitudinal assessment of current and proposed drug therapies for the treatment of emphysema.     

High-resolution CT and CT angiography of peripheral pulmonary vascular disorders.

Peripheral pulmonary vascular disorders that can be evaluated with computed tomography (CT) include various disease entities with overlapping imaging features and a wide range of clinical manifestations. The overall accuracy of CT in the diagnosis of pulmonary vascular disorders increases with improved spatial resolution, administration of a high-flow contrast material bolus, and the use of cardiac gating. The integration of high-resolution CT and CT angiographic techniques into one scanning protocol has important clinical implications for multisection CT and makes it the imaging modality of choice in the evaluation of this complex group of disorders.     

Renal lymphoma: CT patterns with emphasis on helical CT.

Renal lymphoma is most often seen in conjunction with multisystemic, disseminated lymphoma or as tumor recurrence. Renal lymphoma may also be seen in immunocompromised patients or, rarely, as primary disease. Computed tomography (CT) is the most sensitive, efficient, and comprehensive examination for evaluation of the kidneys in patients with suspected renal lymphoma. Helical CT in particular improves detection and characterization of lymphomatous renal involvement by optimizing contrast dynamics and data acquisition and is the current modality of choice for accurate staging of lymphoma. Typical CT patterns in renal lymphoma include single and multiple masses, invasion from contiguous retroperitoneal disease, perirenal disease, and diffuse renal infiltration. Atypical CT patterns may also be encountered and provide a diagnostic challenge. These include spontaneous hemorrhage, necrosis, heterogeneous attenuation, cystic transformation, and calcification. Solid renal masses including renal cell carcinoma and metastases are the most commonly encountered entities that mimic renal lymphoma at CT and require biopsy for definitive diagnosis. CT (particularly helical CT) is useful in the evaluation of patients with suspected renal lymphoma, and familiarity with the spectrum of findings in renal lymphoma is important for accurate diagnosis.     

SPECT/CT.

In view of the commercial success of integrated PET/CT scanners, there is an increasing interest in comparable SPECT/CT systems. SPECT in combination with CT enables a direct correlation of anatomic information and functional information, resulting in better localization and definition of scintigraphic findings. Besides anatomic referencing, the added value of CT coregistration is based on the attenuation correction capabilities of CT. The number of clinical studies is limited, but pilot studies have indicated a higher specificity and a significant reduction in indeterminate findings. The superiority of SPECT/CT over planar imaging or SPECT has been demonstrated in bone scintigraphy, somatostatin receptor scintigraphy, parathyroid scintigraphy, and adrenal gland scintigraphy. Also, rates of detection of sentinel nodes by biopsy can be increased with SPECT/CT. This review highlights recent technical developments in integrated SPECT/CT systems and summarizes the current literature on potential clinical uses and future directions for SPECT/CT in cardiac, neurologic, and oncologic applications.     

Radiation exposure in CT

The use of CT has increased rapidly in the past two decades, in part because of the development of helical CT and multidetector row CT. The benefits obtained by CT are not, however, without risks. This paper emphasizes the importance of keeping radiation doses during CT procedures as low as reasonably possible, especially for pediatric and small adult patients. In order to evaluate the risk of exposure, precise dosimetry is important. This paper introduces a new film dosimetry system that can be used easily in any institution and with any CT apparatus.     

CT vs 68Ge attenuation correction in a combined PET/CT system: evaluation of the effect of lowering the CT tube current

With the introduction of combined positron emission tomography/computed tomography (PET/CT) systems, several questions have to be answered.In this work we addressed two of these questions: (a) to what value can the CT tube current be reduced while still yielding adequate maps for the attenuation correction of PET emission scans and (b) how do quantified uptake values in tumours derived from CT and germanium-68 attenuation correction compare. In 26 tumour patients, multidetector CT scans were acquired with 10, 40, 80 and 120 mA (CT10, CT40, CT80 and CT120) and used for the attenuation correction of a single FDG PET emission scan, yielding four PET scans designated PET(CT10)-PET(CT120). In 60 tumorous lesions, FDG uptake and lesion size were quantified on PET(CT10)-PET(CT120). In another group of 18 patients, one CT scan acquired with 80 mA and a standard transmission scan acquired using 68Ge sources were employed for the attenuation correction of the FDG emission scan (PET(CT80), PET(68Ge)). Uptake values and lesion size in 26 lesions were compared on PET(CT80) and PET(68Ge). In the first group of patients, analysis of variance revealed no significant effect of CT current on tumour FDG uptake or lesion size. In the second group, tumour FDG uptake was slightly higher using CT compared with 68Ge attenuation correction, especially in lesions with high FDG uptake. Lesion size was similar on PET(CT80) and PET(68Ge). In conclusion, low CT currents yield adequate maps for the attenuation correction of PET emission scans. Although the discrepancy between CT- and 68Ge-derived uptake values is probably not relevant in most cases, it should be kept in mind if standardised uptake values derived from CT and 68Ge attenuation correction are compared.     

CT arthrography of the glenohumeral joint: CT fluoroscopy versus conventional CT and fluoroscopy--comparison of image-guidance techniques

PURPOSE: To compare examination time with radiologist time and to measure radiation dose of computed tomographic (CT) fluoroscopy, conventional CT, and conventional fluoroscopy as guiding modalities for shoulder CT arthrography. MATERIALS AND METHODS: Glenohumeral injection of contrast material for CT arthrography was performed in 64 consecutive patients (mean age, 32 years; age range, 16-74 years) and was guided with CT fluoroscopy (n = 28), conventional CT (n = 14), or conventional fluoroscopy (n = 22). Room times (arthrography, room change, CT, and total examination times) and radiologist times (time the radiologist spent in the fluoroscopy or CT room) were measured. One-way analysis of variance and Bonferroni-Dunn posthoc tests were performed for comparison of mean times. Mean effective radiation dose was calculated for each method with examination data, phantom measurements, and standard software. RESULTS: Mean total examination time was 28.0 minutes for CT fluoroscopy, 28.6 minutes for conventional CT, and 29.4 minutes for conventional fluoroscopy; mean radiologist time was 9.9 minutes, 10.5 minutes, and 9.0 minutes, respectively. These differences were not statistically significant. Mean effective radiation dose was 0.0015 mSv for conventional fluoroscopy (mean, nine sections), 0.22 mSv for CT fluoroscopy (120 kV; 50 mA; mean, 15 sections), and 0.96 mSv for conventional CT (140 kV; 240 mA; mean, six sections). Effective radiation dose can be reduced to 0.18 mSv for conventional CT by changing imaging parameters to 120 kV and 100 mA. Mean effective radiation dose of the diagnostic CT arthrographic examination (140 kV; 240 mA; mean, 25 sections) was 2.4 mSv. CONCLUSION: CT fluoroscopy and conventional CT are valuable alternative modalities for glenohumeral CT arthrography, as examination and radiologist times are not significantly different. CT guidance requires a greater radiation dose than does conventional fluoroscopy, but with adequate parameters CT guidance constitutes approximately 8% of the radiation dose.     

An auxiliary CT tabletop for radiography at the time of CT.

An auxiliary CT tabletop was designed and manufactured such that radiographic images might be acquired, with use of a ceiling-mounted X-ray tube, without removing the patient from the CT table. The tabletop required no modifications to the original CT table housing and did not produce artifacts in the CT images. Radiographs obtained with the overhead X-ray tube and auxiliary tabletop demonstrated image quality equivalent to traditional radiographs.     

Perfusion CT and angio CT in the assessment of acute stroke

In order to evaluate the clinical utility of non-enhanced CT with perfusion and angio CT in the assessment of acute ischaemic stroke, 42 patients with symptoms of acute stroke were examined within the first 6 h from onset of symptoms with non-enhanced CT (NECT), perfusion CT (PCT) and CT angiography (CTA). Maps of cerebral blood flow (CBF), cerebral blood volume (CBV) and mean transit time (MTT) were analysed visually, and after drawing regions of interest (ROIs) in the territory of anterior, middle and posterior cerebral arteries, maximum-intensity projection and volume-rendering images of the cervical and cerebral vessels were created. All patients underwent a control CT or MR examination 24–48 h after the initial examination. Twenty-nine patients developed an area of infarction at control examinations. Significant perfusion abnormalities were found in 27 cases, whilst in two patients the perfusion studies were considered to be normal. All the cases with perfusion abnormalities showed arterial stenoses or occlusions on angio CT. Small infarctions at levels other than the ones selected for perfusion CT, and arteriosclerotic changes, were observed in the two cases with no perfusion abnormalities. In conclusion, combining non-enhanced CT with PCT and CTA is a simple and a very valuable tool in the initial assessment of acute stroke.