Evaluation of an experimental low-attenuation gastrointestinal contrast agent for CT imaging of intestinal ischemia in an animal model.

RATIONALE AND OBJECTIVES: The authors evaluated the use of MRX-320, a low-attenuation, expansile oral contrast agent, for the demonstration of intestinal ischemia in an animal model. MATERIALS AND METHODS: Nine dogs were given either MRX-320, water, or diatrizoate as an oral contrast agent through a jejunostomy tube. Two dogs received no oral contrast agent. Helical computed tomography (CT) was performed before the intravenous injection of 2.5 mL/kg iohexol at 4 mL/sec, during the arterial phase, and during the portal venous phase. Mesenteric ischemia was surgically induced, and the imaging protocol was repeated. Three readers rated the randomly assigned images for quality and demonstration of ischemia. Attenuation values for the intestinal lumen and wall were recorded. RESULTS: Examinations performed with MRX-320 provided the best discrimination between ischemic and nonischemic conditions (P < .05), followed by examinations with no oral contrast medium, examinations with water, and examinations with diatrizoate. Images obtained with MRX-320 also scored significantly higher on measures of image quality than those obtained with water or no oral contrast medium (P < .05). On images obtained with MRX-320, the bowel lumen measured -836.5 HU (P < .05 compared with other techniques). Water provided the least uniformity of distention, and diatrizoate provided the least mucosal detail. CONCLUSION: The use of MRX-320 as an oral contrast agent with an intravenous bolus of iohexol at CT increased reader confidence for the diagnosis of intestinal ischemia and improved subjective measures of image quality.

Effect of field of view on MR diagnosis of rotator cuff tears.

PURPOSE: To determine the effect of decreasing the field of view (FOV) on the accuracy of MR for diagnosing rotator cuff tears. MATERIAL AND METHODS: One hundred shoulder MR scans with surgical correlation were evaluated for the presence or absence of a cuff tear. The sensitivity and specificity of MR relative to the surgical results were determined for the 59 patients scanned with a 24-cm FOV, and the 41 patients scanned with an 18-cm FOV. All other imaging parameters including acquisition time were identical. The sensitivity and specificity of the two groups were compared using a t-test. RESULTS: The specificity of MR for diagnosing a rotator cuff tear improved from 0.65 for the 24-cm FOV group to 0.89 for the 18-cm FOV group (P = 0.04). The sensitivity changed from 0.91 to 0.96 (P = 0.25). CONCLUSION: Reducing the FOV from 24 cm to 18 cm results in a statistically significant improvement in specificity of MR for diagnosing rotator cuff tears.

Abdominal hernias: CT findings.

Abdominal hernias remain a common and vexing problem for both clinicians and radiologists. Unlike inguinal hernias, which are usually diagnosed clinically and are amenable to minor surgical repair, internal hernias can be difficult to diagnose, require more extensive surgical intervention, and have an increased risk of serious complications. Additionally, it is important to recognize structures contained within a hernia sac, so that precautions are taken at surgery. Therefore, accurate preoperative diagnosis can lead to more timely and appropriate surgical management. Abdominal imaging is often the first clue to the correct diagnosis. In the past, the diagnosis of a hernia was either made clinically, with plain radiographs, or with barium studies [1]. Currently, specific diagnoses are made more frequently by CT in patients with nonspecific abdominal complaints [2]. The CT findings may be subtle or confusing; therefore, familiarity with a broad range of imaging appearances can help the radiologist make an early and specific diagnosis of abdominal hernia.

Diagnosis of partial and complete rotator cuff tears using combined gradient echo and spin echo imaging.

Most magnetic resonance (MR) studies evaluating the rotator cuff for tears have used T2-weighted imaging in the coronal oblique and sagittal oblique planes. T2*-weighted gradient echo imaging, however, has advantages over spin echo imaging, including contiguous slices without cross-talk, high contrast around the cuff, and intrinsically shorter imaging times which can be used to increase the number of signals averaged and thus improve the signal-to-noise ratio. We reviewed the shoulder MR scans of 87 consecutive patients who underwent both a MR scan and a shoulder arthroscopy during which the size of tears, if present, was graded. The reviewers were blinded as to the history and arthroscopic results. The MR scans included oblique coronal T2*-weighted gradient echo and oblique sagittal T2-weighted spin echo images. MR cuff grades were correlated with arthroscopic findings. For complete tears, the sensitivity of MR was 0.91 and the specificity 0.95. For partial tears, the sensitivity was 0.74 and the specificity 0.87. This accuracy is similar to two-plane T2-weighted imaging as previously reported in the literature. There was a statistically significant correlation (p < 0.0005) between the cuff grade as determined by MR and the arthroscopic findings.

MR diagnosis of meniscal tears of the knee: importance of high signal in the meniscus that extends to the surface.

OBJECTIVE: The presence of intrameniscal signal in contact with the surface is a commonly used criterion for the diagnosis of meniscal tear. This signal presumably represents the actual tear in the meniscus. However, some menisci with signal that contacts the surface are noted to be intact at arthroscopy whereas other menisci that have no signal in contact with the surface are found to be torn. We investigated the relationship between the presence of a meniscal tear at arthroscopy and the location within the menisci of signal that contacted the surface. We hypothesized that patterns were present that would improve the accuracy of MR diagnosis of a meniscal tear. MATERIALS AND METHODS: We reviewed the MR and arthroscopic findings from 200 consecutive patients who had both knee MR examinations and knee arthroscopy. There were 108 medial and 58 lateral meniscal tears on arthroscopy. Each MR examination was reviewed for three aspects of intrameniscal signal: the number of images showing signal possibly or definitely contacting the surface, the specific surfaces involved, and the signal location. The coronal and sagittal images were evaluated separately. We correlated each of these features with the presence of a meniscal tear at arthroscopy. RESULTS: Menisci with signal possibly contacting the surface had the same frequency of tears (three tears in 33 menisci) as menisci without signal contacting the surface (15 tears in 194 menisci). More than 90% of menisci with signal contacting the surface on more than one image were torn, but only 55% of medial and 30% of lateral menisci with such signal on only one image were torn. In the torn menisci with signal contacting the surface, such signal was seen only on sagittal MR images in 31% of the medial menisci and 45% of the lateral menisci. Sixteen percent of the torn lateral menisci had signal contacting the meniscal surface in only the anterior two thirds of the meniscus, whereas this was true in only 2% of the torn medial menisci. Distinct patterns were not seen in the association between tears and signal contacting either the superior or the inferior surface. CONCLUSION: We found definite patterns in the location of intrameniscal signal that comes in contact with the meniscal surface. These patterns vary in the frequency of associated meniscal tears. Although menisci with internal signal in contact with the surface are usually torn, a tear is less likely if such signal is present on only one image. Tears may be identifiable on only one image plane. Tears in the anterior horn of the lateral meniscus are not uncommon. Knowledge of these patterns should help in the MR diagnosis of meniscal tears.

Diagnosis of meniscal tears of the knee with MR imaging: effect of observer variation and sample size on sensitivity and specificity.

OBJECTIVE: A wide range in the efficacy of MR imaging for the diagnosis of meniscal tears of the knee has been reported. To evaluate two possible causes for this variation, we studied how sensitivity and specificity are affected when different observers and sample sizes are used. MATERIALS AND METHODS: Two hundred MR examinations of the knee in patients for whom the results of arthroscopy were available were used for the study. One hundred eight medial meniscal tears and 58 lateral meniscal tears were found at arthroscopy. The sensitivity and specificity for detection of meniscal tears were determined for the original interpretations and retrospective evaluations by three observers. Comparisons were also made between sample sizes of 25 and 100. chi 2 analysis was used for unmatched data sets and McNemar's statistic was used for matched sets. RESULTS: For the 200 examinations, the sensitivity was 0.89-0.93 for medial meniscal tears and 0.79-0.83 for lateral meniscal tears. The specificity was 0.86 for medial meniscal tears and 0.90-0.92 for lateral meniscal tears. Sensitivity and specificity varied widely among different observers and different sample sizes. However, we found no significant difference between any of the comparisons at the p < .05 level. The largest interobserver variation occurred in the detection of lateral meniscal tears, with a sensitivity of 0.71 for one observer and 0.88 for another observer (p = .16). The largest variation between sets of 100 examinations was a change in sensitivity for detection of lateral meniscal tears from 0.74 to 0.88 for the original interpretations (p = .10). For the sample sets of 25 cases, the variation was even larger, with the sensitivity for detection of lateral meniscal tears varying from 0.5 for one set to 1.0 for another. CONCLUSION: We conclude that chance variation related to sample size can cause large but not statistically significant variations in sensitivity and specificity in this setting. These variations are of sufficient magnitude to explain many of the differences in reported sensitivity and specificity for MR imaging in the diagnosis of meniscal tears. We found no significant difference in observer performance.

Scatter radiation exposure during knee arthrography.

Knee arthrography, as performed at the authors' institution, was simulated and scattered radiation exposure to a radiologist's gonads, thyroid, and eye lens was measured with a sensitive ionization chamber. Results show that radiologists who regularly conduct knee arthrography examinations can incur doses to the gonads that are less than 6% of the U.S. limits, and to the thyroid and eye that are approximately 10% of the U.S. limits. Since the scatter radiation from overhead imaging of stress views constituted most (greater than or equal to 60%) of the dose to the lens of the eye and the thyroid, spot imaging was evaluated as a substitute for overhead imaging in the assessment of the anterior cruciate ligament. This substitution resulted in no loss of clinical information and has now completely replaced overhead imaging of stress views at this institution.

Ultrasound imaging as a screening study for malignant soft-tissue tumors.

Fifty patients who had a palpable soft-tissue mass and an apparently normal radiograph were studied with ultrasound imaging before excision or biopsy of the lesion was done. As shown by the sonograms, thirty-five lesions had a discrete echo pattern (usually reduced echoes and a clearly defined lesional margin) and fifteen had an ill defined pattern (similar to the pattern of the surrounding normal tissues with no definable lesional margin). Fourteen lesions were malignant and thirty-six, benign. The sonograms of all fourteen malignant lesions showed a discrete pattern, while the sonograms of the benign ones showed twenty-one discrete and fifteen ill defined patterns. Therefore, the malignant lesions produced a discrete pattern in every instance, and every lesion that produced an ill defined pattern was benign. Fourteen of the fifty lesions were cystic; of these, thirteen were benign and one was malignant. The sonograms correctly identified the cyst in seven of the thirteen benign lesions and in the one malignant cystic lesion. Based on these findings, we concluded that all palpable soft-tissue masses that appear to be discrete on a sonogram should be diagnosed without delay by examination of a specimen taken at biopsy, whereas lesions that have an ill defined appearance on a sonogram may be assumed to be benign and may safely be observed in selected patients.

Tomographic digital subtraction angiography: initial clinical studies using tomosynthesis. Work in progress.

We have developed a method for acquiring multiple tomographic subtraction images using a rapid, repetitive, circular tomographic motion. The method combines the principles of digital subtraction angiography (DSA) and electronic tomosynthesis. Fifteen patients were examined with the technique using single intravenous bolus injections of contrast material. The image sequence obtained during each injection was first processed with a nontomographic mask subtraction, and the result was then compared with the tomographic DSA scans synthesized from the same sequence. The effective section thickness was approximately 0.5 cm, with each section being 0.5-1.0 cm apart. Twelve of the intravenous DSA scans provided the necessary diagnostic or clinically useful information. Two of the three nondiagnostic scans were caused by avoidable technical reasons. In eight cases, the tomographic DSA scans were superior in quality to the nontomographic scans, exhibited significantly less artifact from patient motion and overlying bowel gas, and were effective in separating overlapping vessels. Tomosynthesis permits multiple electronic imaging of the area of interest without reinjection of contrast material and appears to be more informative than nontomographic intravenous DSA imaging.

Computed tomography of spontaneous osteoporotic sacral fractures.

Spontaneous osteoporotic sacral fractures are an uncommon entity. They are difficult to image on plain films. Clinically, they may be confused with metastatic disease. A peculiar H-shaped uptake pattern on bone scan should suggest the condition, and CT can then demonstrate the fracture. In this case this combination of radionuclide scan and CT permitted differentiation of a sacral fracture from presumed bony metastases.

Femoral defect after anterior dislocation.

A case is reported of a wedge-shaped defect in the anterolateral portion of the femoral head following an anterior dislocation of the obturator type. This hatchet-like defect is similar to the Hill-Sachs defect of the humerus.

Inferior vena cava obstruction presenting as an abdominal mass.

Obstruction of the inferior vena cava (IVC) was observed as an abdominal mass on the plain radiograph in an asymptomatic patient. The obstruction had developed immediately below the renal veins, and markedly dilated varices were present. The appearance differed from that of the usual congenital caval variants and may have been the result of caval thrombosis in utero.

Congenital generalized fibromatosis. Case report and literature review.

A typical case of congenital generalized fibromatosis (CGF) is presented and the literature on this entity is reviewed. CGF is a rare condition which is probably heritable. It is manifested in infancy. Because of the unusual biological behavior of the fibromata, two clinical courses occur--death, if vital viscera are involved, or regression of the lesions and survival without significant disability. Including the present example, 63 cases have been reported.

Gas contrast guided needle biopsy of the head of the pancreas.

Localization of the pancreatic head for biopsy under fluoroscopy was accomplished using carbon dioxide-producing pills. This technique proved useful when other modalities were unsuccessful. Gas can be a useful contrast agent for localization, has no side effects, and causes little interference with further procedures. A case report is presented.