Female pelvic floor: endovaginal MR imaging of normal anatomy

Five types of processed corn were compared to determine the effects of processing on lactational performance and nutrient digestibilities in dairy cows. Forty lactating Holstein cows averaging 160 +/- 60 d in milk were randomly divided into five groups on the basis of pretreatment milk yields and were fed diets containing 40% corn grain for 56 d. Treatments were 1) finely ground corn, 2) coarsely ground corn, 3) steam-flaked corn at a low density, 4) steam-flaked corn at a medium density, and 5) steam-rolled corn. Cows fed the diet containing steam-flaked corn at a medium density had a higher milk yield (37.1 kg/d) than did cows fed the diets containing coarsely ground corn, steam-flaked corn at a low density, or steam-rolled corn; cows fed the diet containing finely ground corn had an intermediate milk yield (35.5 kg/d). Efficiency of feed utilization was greater, and dry matter intake was lower, for cows fed the diet containing finely ground corn than for cows fed the other diets. The fat content of milk was higher for cows fed the diets containing coarsely ground corn and steam-rolled corn than for cows fed the diet containing steam-flaked corn at a medium density. Milk protein and SNF contents and yields of protein, lactose, and SNF did not differ among diets. Apparent starch digestibilities in the total digestive tract were lower for diets containing coarsely ground corn (87.4%) and steam-rolled corn (91.3%) than for the other diets (X = 96.3%). Milk yield was highest for cows fed the diet containing steam-flaked corn with a medium density. Fine grinding resulted in the greatest efficiency of feed utilization.     

In vitro and in vivo MR imaging of hyaline cartilage: zonal anatomy, imaging pitfalls, and pathologic conditions

Hyaline cartilage plays an essential role in the maintenance of normal synovial joint function by reducing friction and distributing loads. Histologic analysis of hyaline cartilage reveals zonal variation in cellular morphology, proteoglycan concentration, and collagen fiber size and orientation. High-resolution magnetic resonance (MR) imaging reveals an analogous laminar anatomy that is often visible on clinical images obtained with proper attention to technique. In vitro and in vivo pulse sequences show three distinct laminae: a hypointense superficial lamina, a hyperintense intermediate lamina, and a heterogeneous deep lamina that consists of alternating hyperintense and hypointense bands perpendicular to the subchondral bone. Imaging pitfalls include magic angle effects, truncation artifact, partial volume effect, regional anatomic variation, chemical shift, and magnetic susceptibility effects. Pathologic conditions that affect articular cartilage include chondromalacia patellae, osteoarthritis, and localized traumatic lesions. Although detection of early cartilage disease remains elusive, MR imaging can demonstrate intermediate and advanced lesions.     

Beyond anatomy: MR imaging as a molecular diagnostic tool

Technical advances in software and hardware make MR imaging competitive with CAT scanning as an anatomic imaging tool. Although anatomic relationships remain important, increased understanding of cell structure and function is rapidly moving us toward diagnosis and treatment at the cellular level. By virtue of its reliance on nuclear magnetic spin moment, MR imaging is responsive to real time physico-chemical characteristics of cells and tissues being imaged. This intrinsic advantage of MR imaging is being rapidly developed through the use of targeted imaging agents and magnetic resonance spectroscopy. Imaging agents that target specific cell populations have been prepared by using monoclonal antibodies, liposomes, and short peptides bound to chelates containing paramagnetic atoms. Using magnetic resonance spectroscopy, the chemical composition of tumors can be analyzed and compared with normal tissues in vivo and in vitro. Areas of possible clinical usefulness for magnetic spectral analysis include: (1) in vitro or in vivo characterization of lesions as benign or malignant, (2) differentiation between in situ and invasive carcinomas, (3) determination of responsiveness to specific chemotherapeutic regimens before their institution, (4) study of in vivo drug metabolism by neoplasms, and (5) assessment of response to therapy and of residual disease at the completion of therapy. Early experiences in these parallel fields show great promise, with widespread clinical applications expected in the near future.     

Measurement of regional aortic compliance by MR imaging: a study of reproducibility

The reproducibility of MR imaging for the measurement of aortic compliance was studied in 47 healthy volunteers. Long and short term reproducibility and intraobserver variability were tested. The method was modified to improve image quality and short term reproducibility and intraobserver variability retested. For comparison, spin echo imaging was compared with cine gradient echo imaging. Initial long term reproducibility showed a mean difference (+/-SE) of 3% (+/- 7%) with 95% confidence interval (CI) for limits of agreement of +/- 69%. Short term reproducibility (7% +/- 6%, 95% CI +/- 46%) and intraobserver variability (1% +/- 2%, 95% CI +/- 31%) were better. After modification of the technique and optimization of image quality, both short term reproducibility and intraobserver variability improved (0% +/- 3%, 95% CI +/- 17% and 5% +/- 2%, 95% CI +/- 16% respectively). Aortic compliance can be measured using spin echo MR imaging with good reproducibility provided care is taken to obtain good quality images with high spatial resolution.     

Fetal central nervous system anomalies: MR imaging augments sonographic diagnosis

PURPOSE: To evaluate fetuses with sonographically suspected central nervous system anomalies to determine the frequency with which obstetric magnetic resonance (MR) imaging adds clinically useful information to that provided by ultrasonography (US). MATERIALS AND METHODS: US and MR images and diagnoses in 18 pregnant women were reviewed and compared by two radiologists. Postnatal physical examination and imaging findings and fetal autopsy results were standards. Referring physicians were questioned as to how the additional information provided by MR imaging changed patient counseling. RESULTS: In 10 (55%) patients, MR imaging demonstrated 11 additional findings. These findings were agenesis of the corpus callosum (n = 4), cerebellar hypoplasia (n = 2), cortical cleft (n = 2), polymicrogyria (n = 1), porencephaly (n = 1), and partial agenesis of the septi pellucidi (n = 1). In seven (39%) patients, additional information provided by MR imaging altered counseling. In one case of suspected agenesis of the corpus callosum, diagnosis at MR imaging was at least partially incorrect. CONCLUSION: US and MR imaging are complementary imaging methods in the evaluation of high-risk pregnancy. When a central nervous system anomaly is suspected at US, MR imaging may demonstrate additional findings that can alter patient counseling.     

MR arthrography of the shoulder: rethinking traditional imaging procedures to meet the technical requirements of MR imaging guidance

Increased serum levels of mucin-associated antigen have been previously demonstrated in patients with cystic fibrosis (CF) and interstitial pneumonia, and in lung-transplant recipients. The present study assessed the serum airway mucin levels in patients with acute respiratory distress syndrome (ARDS). An enzyme-linked immunosorbent assay (ELISA) method with a human-airway-mucin-specific monoclonal antibody (17Q2) was used to measure serum mucin levels in normal subjects, chronic smokers, patients with chronic bronchitis and other pulmonary diseases, patients with acute cardiogenic lung edema, and patients with ARDS. The serum mucin levels measured 9.9 +/- 0.8 ng/ml (mean +/- SEM, n = 59) in normal subjects, 12.7 +/- 1.6 ng/ml (n = 29) in chronic smokers, 21.8 +/- 1.9 ng/ml (n = 28) in patients with chronic bronchitis and other pulmonary diseases, 9.0 +/- 3.1 ng/ml (n = 5) in patients with acute cardiogenic lung edema. The serum mucin level was 53.8 +/- 6.6 ng/ml (n = 13) in patients with ARDS (p < 0.05, as compared with the four other groups). Serial measurements of serum mucin levels were obtained in patients with ARDS. Statistical analysis showed an inverse correlation of serial measurements of serum mucin with static respiratory-system compliance (p = 0.021), an inverse correlation of sequential serum mucin levels and log(Pa(O2)/Fl(O2)) (p = 0.016), and a positive correlation of sequential serum mucin levels and lung injury score (LIS) (p = 0.019). Gel-filtration analysis showed that mucin-associated antigens in ARDS sera were polydispersed and smaller than the antigens in normal sera. This study indicates that an increasing amount of degraded mucin occurs in patients with ARDS.     

Basic pulse sequences for fast cardiac MR imaging

Technical challenges of cardiac MRI include minimizing the effects of cardiac and respiratory motion and developing techniques that allow for both high spatial resolution and high SNR given the small size of small structures such as the coronary vessels. Fast imaging techniques provide considerable time savings and increased flexibility which allow to further optimize image quality.     

Prostatic cryosurgery: use of MR imaging in evaluation of success and technical modifications

PURPOSE: To evaluate the usefulness of contrast material-enhanced magnetic resonance (MR) imaging in objective assessment of prostatic cryosurgery and the role of MR imaging in the modification of prostatic cryosurgical technique. MATERIALS AND METHODS: Thirty-eight consecutive patients with localized (T1-3, N0, M0) prostatic adenocarcinoma treated with prostatic cryosurgery underwent MR imaging without contrast enhancement before cryosurgery and unenhanced and gadolinium-enhanced MR imaging within 1-3 weeks after cryosurgery. The first 20 patients also underwent MR imaging at 3 months after cryosurgery. MR imaging findings were correlated with those from transrectal ultrasound-directed prostatic staging biopsy. RESULTS: Cryonecrotic prostate was identified as avascular regions characterized by absolute signal void on contrast-enhanced images. With progressive modification of cryosurgical technique, complete cryoablation of the prostate was achieved in the latter nine of the 38 patients. When cryoablation was considered complete according to MR imaging criteria, findings invariably correlated with those at biopsy, with no residual prostate tissue or tumor. CONCLUSION: Gadolinium-enhanced MR imaging of the prostate after cryosurgery provides a highly accurate means of monitoring success. Objective MR imaging findings allow modifications to the technology and technique, resulting in optimal therapeutic results with prostatic cryosurgery.     

Multishot echoplanar MR imaging of the female pelvis: comparison with fast spin-echo MR imaging in an initial clinical trial

OBJECTIVE: The purpose of this study was to apply multishot echoplanar MR imaging (EPI) to the female pelvis and compare image quality with that of fast spin-echo MR imaging. SUBJECTS AND METHODS: Twenty-one patients with suspected pelvic disease and five healthy female volunteers were prospectively examined. MR imaging was obtained using an EPI-capable 1.0-T imager and a pelvic phased-array coil. Axial EPI and fast Spin-echo sequences were obtained at identical image locations in each patient and volunteer. Spin-echo EPI images were obtained using a multishot number of 16. Acquisition time for each EPI sequence was 2 min 10 sec. Fat-suppressed T2-weighted fast spin-echo images were obtained in 2 min 12 sec. Paired EPI and fast spin-echo MR images were independently evaluated by three reviewers. RESULTS: Delineation of the perivaginal and parametrial venous plexus on EPI was rated superior to the fast spin-echo images in 62 (77%) of 81 cases. On EPI, uterine zone anatomy and ovary visualization were judged to be inferior in 44 (56%) of 78 cases and in 18 (33%) of 54 cases, respectively. For delineation of uterine abnormalities, including leiomyoma and adenomyosis, both sequences performed almost equally well. However, ovarian cystic lesions were revealed more precisely by the fast spin-echo sequence. An overall fat-suppression effect was seen on EPI images in 62 (77%) of 81 cases. CONCLUSION: Multishot EPI cannot replace fast spin-echo sequences for imaging the female pelvis; however, because EPI has a potent fat-suppression effect and heavily T2-weighted contrast, EPI sequences can be a valuable adjunct to routine examination.     

SPLICE: sub-second diffusion-sensitive MR imaging using a modified fast spin-echo acquisition mode

Recent human studies for measuring of the apparent diffusion coefficient in tissue by magnetic resonance imaging have been conducted by time-consuming standard spin-echo acquisition sequences and phase correction with navigator echoes. Diffusion-weighted echo-planar sequences have been shown to be rapid alternatives for brain imaging. Both methods show inherent disadvantages in applications on thoracic or abdominal sites. A new approach combining single-shot diffusion-weighted imaging with a modified fast spin-echo acquisition mode is reported here. The modification is necessary, because normal fast spin-echo acquisition requires a particular phase relation between the magnetization and the refocusing pulses. Unfortunately, this phase relation is not provided after diffusion sensitive preparation. Therefore, the split echo acquisition mode was developed and is shown to be insensitive to the phase of the magnetization. The advantages of both fast spin-echo acquisition and diffusion weighting can be combined in the SPLICE sequence (split aqcuisition of fast spin-echo signals for diffusion imaging). The applicability of the new technique is shown by series of sub-second diffusion-weighted images from different parts of the body.     

MR cholangiography: technical advances and clinical applications

Magnetic resonance (MR) cholangiography is a fast, accurate, noninvasive alternative to endoscopic retrograde cholangiography (ERC) in the evaluation of biliary tract disease. Technical improvements in imaging sequences (eg, half-Fourier rapid acquisition with relaxation enhancement) and use of phased-array coils allow high-quality imaging comparable to that available with ERC. In choledocholithiasis, common bile duct stones as small as 2 mm can be detected with MR cholangiography and appear as low-signal-intensity foci within the high-signal-intensity bile. MR cholangiography may help establish the diagnosis of malignant obstruction and is useful in the evaluation of patients in whom ERC was unsuccessful or incomplete. The role of MR cholangiography in the evaluation of intrahepatic duct disease continues to evolve. MR cholangiography plays a crucial role in evaluating postsurgical biliary tract alterations and can be used to demonstrate a variety of congenital anomalies of the biliary tract (eg, aberrant ducts, choledochal cysts, pancreas divisum). In addition, intentional or incidental imaging of the gallbladder with MR cholangiography can be used to identify calculi or help determine the presence and extent of neoplastic disease.     

MR defecography: depiction of anorectal anatomy and pathology

This is a report of clinical, CT and MRI findings in a patient with toxic spongiform leucoencephalopathy after heroin ingestion. The disease is observed in drug addicts who inhale pre-heated heroin. The clinical onset, which usually occurs some days or even longer after the last heroin consumption, is characterized by a cerebellar syndrome. The cerebellar hemispheres, the cerebellar and cerebral peduncles and the pyramidal tract may be affected. Spongiform demyelination is the morphological substrate of the lesions, which are not contrast enhancing, hypodense on CT and hyperintense on T2-weighted MRI. The frequently perfect symmetry of the affection of functional systems points to a toxic and/or metabolic pathophysiological mechanism.     

Preoperative staging of endometrial carcinoma: diagnostic effect of T2-weighted fast spin-echo MR imaging

PURPOSE: To evaluate the usefulness of T2-weighted fast spin-echo magnetic resonance (MR) imaging with a 512 x 256 matrix for assessment of the preoperative stage of endometrial carcinoma. MATERIALS AND METHODS: Twenty-eight women with histopathologically proved endometrial carcinoma underwent preoperative T2-weighted fast spin-echo, dynamic T1-weighted fast spin-echo, and postcontrast T1-weighted spin-echo MR imaging with a phased-array surface coil. The uterine long-axis planes in each sequence were reviewed at separate sessions by three radiologists blinded to the histopathologic data. RESULTS: For the diagnosis of myometrial invasion, no statistically significant differences were found among T2-weighted imaging, dynamic imaging, and postcontrast T1-weighted imaging. For the diagnosis of deep myometrial invasion, T2-weighted and dynamic images showed higher specificity than postcontrast T1-weighted images (T2-weighted, 89%; dynamic, 88%; and postcontrast T1-weighted, 80%). For cervical invasion, T2-weighted and dynamic images showed larger areas under receiver operating characteristic curves than did postcontrast T1-weighted images (T2-weighted, 0.78; dynamic, 0.71; and postcontrast T1-weighted, 0.67). CONCLUSION: T2-weighted imaging is useful for identifying the stage of endometrial carcinoma.     

Anterior cruciate ligament injury: fast spin-echo MR imaging with arthroscopic correlation in 217 examinations

OBJECTIVE: Our objective was to evaluate the accuracy of MR imaging strategy that uses primarily fast spin-echo sequences for the diagnosis of anterior cruciate ligament tears. MATERIALS AND METHODS: The original clinical interpretations of MR images of 217 examinations of the knee joint were correlated with subsequent arthroscopic results. Each MR examination included a double-echo fast spin-echo sequence as the only imaging sequence in the sagittal plane. Subsequent discordant MR and arthroscopic examinations were then subjected to reanalysis by two observers who were unaware of arthroscopic results to determine if misinterpretations were observer or image dependent. Two hundred sixteen patients who underwent MR imaging for suspected internal derangement of the knee subsequently underwent arthroscopic surgery. Two patients had both knees evaluated. One patient was excluded because he was referred for evaluation for osteomyelitis, not internal derangement. This yielded a total number of 217 MR examinations for suspected internal derangement of the knee. RESULTS: For 56 arthroscopically proven tears, the sensitivity of MR imaging was 96%. The specificity was 98%, yielding an overall accuracy rate of 98%. The positive and negative predictive values were 95% and 99%, respectively. These values are within the ranges of previously reported MR imaging strategies using conventional spin-echo sequences. CONCLUSION: Fast spin-echo MR imaging of the knee can be an alternative to conventional spin-echo imaging for the detection of anterior cruciate ligament tears.     

T2-weighted spin-echo MR imaging of the liver: breath-hold fast spin-echo versus non-breath-hold fast spin-echo images with and without fat suppression

OBJECTIVE: The goal of our study was to compare a T2-weighted breath-hold fast spin-echo (BHSE) technique with T2-weighted non-breath-hold fast spin-echo techniques for imaging the liver. SUBJECTS AND METHODS: Thirty-three patients with hepatic lesions had T2-weighted BHSE images obtained in 22 sec and conventional T2-weighted non-breath-hold fast spin-echo images obtained in 3 min 12 sec with and without fat suppression. Images were analyzed quantitatively by measuring the lesion-liver contrast, spleen-liver contrast, and signal-to-noise ratios of lesions and qualitatively by evaluating the sharpness of hepatic contours, visibility of intrahepatic vessels and other segmental landmarks, and presence of artifacts. RESULTS: Quantitatively, lesion-liver contrast, spleen-liver contrast, and signal-to-noise ratios obtained with the BHSE technique were inferior to those obtained with fast spin-echo techniques with and without fat suppression (11.2 +/- 7.1 versus 15.4 +/- 10.6 and 14.5 +/- 9.8, p < .001; 5.3 +/- 3.7 versus 8.7 +/- 3.5 and 7.0 +/- 3.8, p < .001; 16.2 +/- 8.2 versus 20.1 +/- 10.9 and 19.7 +/- 9.5, p < .01, respectively; Student's t test). Qualitatively, image artifacts and intrahepatic vessel depiction on BHSE images were similar to those obtained with the fast spin-echo techniques. The BHSE technique was superior to fat-suppressed fast spin-echo technique for showing hepatic contours (p < .01; Wilcoxon signed-rank test). CONCLUSION: The BHSE technique is quantitatively inferior to non-breath-hold fast spin-echo techniques. However, further studies with a surgical standard of reference are needed to compare the three techniques in terms of sensitivity.     

Pancreatic adenocarcinoma: combination of MR imaging, MR angiography and MR cholangiopancreatography for the diagnosis and assessment of resectability

BACKGROUND: Enteropancreatic malignancy is an important cause of morbidity and mortality associated with multiple endocrine neoplasia type 1 (MEN 1). However, the risk factors and mechanisms of the tumorigenesis of this malignancy are poorly understood. METHODS: The authors conducted a retrospective study of factors associated with the development of malignant enteropancreatic tumor in 69 patients with MEN 1 belonging to a single family. RESULTS: Metastatic enteropancreatic tumor and gastrinoma were identified in 20% and 36% of patients, respectively. Compared with MEN 1 patients who did not have an immediate family history of enteropancreatic malignancy, MEN 1 patients with a first-degree relative affected by enteropancreatic malignancy had an increased risk of developing disseminated tumor (odds ratio, 3.7; P < 0.05). In addition, hypergastrinemia and advanced age were both associated with a significant increase in the risk of enteropancreatic malignancy. Elevated serum glycoprotein alpha subunit levels were associated with enterochromaffin-like cell hyperplasia, gastric carcinoid formation, and disseminated enteropancreatic tumor in hypergastrinemic patients (P < 0.05). CONCLUSIONS: Disease modifier factors act in concert with the MEN 1 gene to modulate the development of enteropancreatic neoplasia. It is possible to identify MEN 1 patients at high risk for developing aggressive enteropancreatic tumors. Heritable disease modifier factor(s) affecting enteropancreatic malignancy appear to reside at loci distinct from that of the MEN 1 gene.     

Non-breath-hold fast spin-echo versus breath-hold fast spin-echo and spoiled gradient-recalled echo MR imaging in the detection of hepatic tumors: correlation with surgical findings

OBJECTIVE: Our objective was to compare the sensitivity of non-breath-hold T2-weighted fast spin-echo with and without fat suppression, breath-hold T2-weighted fast spin-echo without fat suppression, and spoiled gradient-recalled echo (GRE) MR imaging for detecting hepatic tumors using surgical findings as the standard of reference. SUBJECTS AND METHODS: Eighteen patients with 36 surgically proven hepatic tumors had non-breath-hold T2-weighted fast spin-echo (6000/117 [TR/effective TE; echo train length, 16) MR imaging with and without fat suppression, breath-hold T2-weighted fast spin-echo MR imaging (2700/105; echo train length, 20), and spoiled GRE images (10.1/1.9; flip angle, 30 degrees) obtained before and after injection of a gadolinium chelate. Images were analyzed separately by two independent readers, with disagreements resolved by consensus reading. RESULTS: Non-breath-hold T2-weighted fast spin-echo MR imaging with and without fat suppression depicted 22 (61%; 95% confidence interval [CI], 43-77%) and 20 (56%; 95% CI, 37-72%) of 36 hepatic tumors, respectively. Breath-hold T2-weighted fast spin-echo imaging allowed detection of 19 (53%; 95% CI, 35-69%) of 36 hepatic tumors. Unenhanced and gadolinium chelate-enhanced spoiled GRE images allowed depiction of 18 (50%; 95% CI, 33-67%) and 29 (81%; 95% CI, 63-91%) of 36 hepatic tumors, respectively. Gadolinium chelate-enhanced spoiled GRE images allowed depiction of significantly more hepatic tumors than any of the other pulse sequences. CONCLUSION: Gadolinium chelate-enhanced spoiled GRE imaging is more sensitive than T2-weighted MR imaging obtained with a breath-hold or a non-breath-hold technique.     

Breath-hold fast spin-echo MR imaging of the liver: a technique for high-quality T2-weighted images

The added technical complexity associated with the transfixion screws for interlocking nailing has introduced new complications. We present a case of a femoral arteriovenous fistula caused by the distal interlocking screw after intramedullary nailing of a comminuted diaphyseal femoral fracture.