Seminomas complicating undescended intraabdominal testes in patients with prior negative findings from surgical exploration.

OBJECTIVE: This paper describes the clinical and imaging characteristics of seminoma complicating intraabdominal testes in three patients who had a history of negative findings from surgical exploration of the inguinal canal and scrotum. CONCLUSION: Because inguinal surgery for cryptorchidism may fail to disclose intraabdominal testes, surgery that has negative findings should be followed up by a close examination of the abdomen. Seminomas arising from an intraabdominal testis can be large and asymptomatic or may simulate other diseases. Torsion may occur and occasionally appear as acute abdomen. The imaging features can be nonspecific, and the history of cryptorchidism may not be provided. Awareness of the clinical and imaging features of neoplasms involving undescended intraabdominal testes is important for appropriate diagnosis and therapy.

Contrast magnetic resonance imaging in the assessment of myocardial viability in patients with stable coronary artery disease and left ventricular dysfunction.

BACKGROUND: The utility of contrast MRI for assessing myocardial viability in stable coronary artery disease (CAD) with left ventricular dysfunction is uncertain. We therefore performed cine and contrast MRI in 24 stable patients with CAD and regional contractile abnormalities and compared MRI findings with rest-redistribution 201Tl imaging and dobutamine echocardiography. METHODS AND RESULTS: Delayed MRI contrast enhancement patterns were examined from 3 to 15 minutes after injection of 0.1 mmol/kg IV gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA). Comparable MRI and 201Tl basal and midventricular short-axis images were subdivided into 6 segments. Segments judged nonviable by quantitative and qualitative assessment of 201Tl scans showed persistent, systematically greater MRI contrast signal intensity than segments judged viable (P

Using triphasic helical CT to detect focal hepatic lesions in patients with neoplasms.

OBJECTIVE: Our purpose was to determine the value of triphasic helical CT (unenhanced, hepatic arterial, and portal venous phases) in the detection and characterization of focal hepatic lesions due to hepatomas or metastases. MATERIALS AND METHODS: One hundred two patients with known or suspected hepatomas or liver metastases underwent triphasic CT. The number and conspicuity of lesions were evaluated on each phase. RESULTS: Five hundred eighty-four lesions were detected in 102 patients. Patients with hypovascular malignancies had more lesions detected on the portal venous phase with increased conspicuity than on the other phases. Patients with hypervascular malignancies had lesions best detected on the hepatic arterial phase, which revealed small lesions that were not seen on the other phases in seven (21%) of the 33 patients with hypervascular metastases and hepatomas. No lesions were detected on the unenhanced phase that were not seen on the other phases. However, arterial phase images introduced new diagnostic dilemmas because not all lesions seen on the arterial phase alone were caused by hepatomas or metastases, even in patients with known malignancies; several lesions represented benign abnormalities that included focal nodular hyperplasia. CONCLUSION: The unenhanced phase is not routinely necessary for the detection of metastases or hepatomas. Hypovascular malignancies are best evaluated during the portal venous phase. Small lesions due to hypervascular metastases and hepatomas are best evaluated and may be detected only during the hepatic arterial phase, which should be used routinely in these patients. New dilemmas may develop from the increased sensitivity of the hepatic arterial phase for lesions. However, the hepatic arterial phase is of limited value with hypovascular malignancies.

Theoretical basis for sodium and potassium MRI of the human heart at 1.5 T.

Knowledge of the extent and location of viable tissue is important to clinical diagnosis. In principle, sodium (23Na) and potassium (39K) MRI could noninvasively provide information about tissue viability. In practice, imaging of these nuclei is difficult because, compared with water protons (1H), 23Na and 39K have lower MR sensitivities (9.2 and 0.051%, respectively), and lower in vivo concentrations (ca. 1000-fold). On the other hand, the relatively short T1 relaxation times of 23Na and 39K (ca. 30 and 10 ms, respectively) suggest that optimized imaging pulse sequences may in part alleviate the weak signal of these nuclei. In this study, numerical simulations of high-speed imaging sequences were developed and used to maximize 23Na and 39K image signal-to-noise ratio (SNR) per unit time within the constraints of existing gradient hardware. The simulation demonstrated that decreasing receiver bandwidth at the expense of echo time (TE) results in a substantial increase in 23Na and 39K image SNR/time despite the short T2 and T2* of these nuclei. Referenced to the available 1H signal on existing 1.5 T scanners, the simulation suggested that it should be possible to acquire three-dimensional 23Na images of the human heart with 7 x 7 x 7 mm resolution and 39K images with 26 x 26 x 26 mm resolution in 30 min. Experimentally in humans at 1.5 T, three-dimensional 23Na images of the heart were acquired in 15 min with 6 x 6 x 12 mm resolution and signal-to-noise ratios of 11 and 7 in the left ventricular cavity and myocardium, respectively, which is very similar to the predicted result. The results demonstrate that by choosing imaging pulse sequence parameters that fully exploit the short relaxation times of 23Na and 39K, potassium MRI is improved but remains impractical, whereas sodium MRI improves to the point where 23Na imaging of the human heart may be clinically feasible on existing 1.5 T scanners.

Using MR imaging to diagnose partial tears of the anterior cruciate ligament: value of axial images.

OBJECTIVE: The purpose of this study was to determine the usefulness of axial MR imaging for diagnosing partial anterior cruciate ligament (ACL) tears and to determine if patients could be categorized as having stable or unstable partial ACL tears on the basis of criteria of axial MR imaging. MATERIALS AND METHODS: We reviewed 238 patients who, over a 2-year period, underwent both MR imaging of the knee and arthroscopic evaluation of the ACL. According to arthroscopic examination, these patients had 143 normal ACLs, 67 complete ACL tears, and 28 partial tears. The 28 partial tears included 20 stable tears (no ACL deficiency) and eight unstable partial tears having ACL deficiency or requiring ACL reconstructive surgery. The axial MR images were retrospectively reviewed by two interpreters who were unaware of the arthroscopic findings, and decisions were reached by consensus. The ACL was classified according to its axial configuration and continuity. RESULTS: By axial MR imaging criteria, we found 109 elliptical ACLs, 45 attenuated ACLs, three ACLs with increased intrasubstance signal intensity, six isolated ACL bundle signs, 19 ACLs that could not be visualized, and 56 cloudlike mass signs. Arthroscopically normal ACLs and stable partial tears were difficult to distinguish reliably on axial MR images. Unstable partial ACL tears could not be distinguished from complete ACL tears. However, using axial MR imaging, our observers were able to segregate stable ACLs (normal ligaments and stable partial tears) from unstable ACLs (unstable partial tears and complete tears) with 100% sensitivity and 96% specificity. CONCLUSION: Axial MR imaging of the ACL may provide important diagnostic information for patients who have ACL injury. On axial MR images, stable ACLs were elliptical, attenuated, or showed as areas of increased intrasubstance signal intensity. At arthroscopy, attenuated ACLs represented normal ACLs (76%) and stable partial tears (24%). On axial MR images, the configurations that indicated unstable ligaments were isolated ACL bundle, nonvisualized ACL, and cloudlike mass.

MR imaging of the adult elbow.

Magnetic resonance (MR) imaging can provide important diagnostic information in the evaluation of the adult elbow. Optimal imaging technique should include the use of proper positioning, surface coils, and appropriate sequences and imaging planes as indicated by the suspected abnormalities. A familiarity with the anatomy of the normal elbow is crucial to identifying pathologic entities correctly and avoiding diagnostic pitfalls. Disruption of the collateral ligaments can best be demonstrated with thin-section coronal gradient-echo MR images. Injuries to the flexor and extensor muscle groups, biceps muscles, and triceps muscles require T2-weighted or short-inversion-time inversion recovery (STIR) MR images in the long and short axes of the affected muscle. The evaluation of osteochondral lesions and intraarticular bodies is optimized with T1-weighted and STIR MR images. Synovial processes usually necessitate the intravenous administration of gadopentetate dimeglumine to distinguish joint fluid from pannus. The contents of the cubital tunnel are best visualized on axial T1-weighted and STIR MR images. Masses arising in or near the elbow should be imaged with multiple sequences in at least two planes, and involvement of adjacent vital structures should be carefully evaluated.

MR imaging of sports injuries in the adult elbow: a tailored approach.

With an understanding of the normal anatomy of the elbow and a pertinent clinical history, MR imaging of the elbow need not be a source of fear and confusion for the MR radiologist. Because positioning and scan planning are not as straightforward as they are with other joints such as the knee or shoulder, these processes can be time-consuming. The position in which the patient is optimally scanned is inherently uncomfortable. In a busy MR center with rigorous time constraints, these factors and patient fatigue can limit the time available to acquire images. Thus, a tailored approach to designing a scanning protocol for the elbow is warranted. The preceding discussion attempts to address a streamlined approach to MR imaging of the more common pathologic processes occurring around the elbow. The sequences we have described may require some modification on different imaging systems to take into account variations in field strength and to account for disparity in hardware and software parameters of different vendors. In combination with the information provided in the clinical history, the guidelines we provide should serve as a general template upon which the practicing radiologist can base his or her approach to MR imaging of the elbow.

MR imaging of the rotator cuff mechanism: comparison of spin-echo and turbo spin-echo sequences.

OBJECTIVE: Although well documented in other MR imaging applications, the value of turbo spin-echo sequences in evaluating the shoulder has not been addressed. This study was designed to directly compare matched spin-echo and turbo spin-echo sequences in the MR imaging evaluation of the rotator cuff. MATERIALS AND METHODS: Using otherwise matched double-echo sequences of equal time duration, we performed 123 paired spin-echo (TR/TE, 200/25,75; one excitation) and turbo spin-echo (3500-5000/22,90; two excitations) sequences in the paracoronal and/or parasagittal plane of the shoulders of 76 patients referred to our institution for possible rotator cuff tear. The sequences were retrospectively analyzed for cuff signal and morphology, fluid conspicuity, coracoacromial arch morphology, and bone marrow signal abnormalities. Surgical and nonsurgical clinical results were correlated when available. RESULTS: We found 100% diagnostic correlation between spin-echo and turbo spin-echo sequences for rotator cuff integrity. Surgical data were available for 26 patients, and clinical follow-up for another 37. For complete rotator cuff tear in the surgical subpopulation, sensitivity was 89%, specificity was 94%, and diagnostic accuracy was 24 of 26 (92%). We found no diagnostically significant difference between the two imaging sequences for fluid conspicuity, coracoacromial morphology, or marrow signal. Signal-to-noise ratios were superior in the turbo spin-echo sequences. CONCLUSION: Turbo spin-echo sequences are an accurate and efficient tool in the MR imaging evaluation of the rotator cuff. Potential benefits include time saving, increased spatial resolution, and improved signal-to-noise ratio.

Pancreaticobiliary manifestations of AIDS.

The pancreas and the biliary tract are frequent sites of infectious, Inflammatory, and neoplastic disease in patients with HIV infection. However, the symptoms of pancreaticobiliary involvement may be relatively mild so that the prevalence of these disorders is probably underestimated. An appreciation of the imaging findings of HIV-associated pancreaticobiliary disorders is important because involvement of these organs may be the only criterion that establishes the diagnosis of AIDS (Table 1).

MR imaging of the posterior cruciate ligament: normal, abnormal, and associated injury patterns.

The posterior cruciate ligament (PCL) of the knee has received little attention in the radiology literature, but its importance in knee stability has come under close scrutiny in recent years. Unrepaired injury of the PCL can lead to chronic instability and early joint degeneration. Three major mechanisms of trauma that involves the PCL are posterior displacement of the tibia in a flexed knee, hyperextension, and rotation combined with an adduction or abduction force. The spectrum of PCL injuries includes partial tear or intrasubstance injury, complete ligamentous rupture, and avulsion of the PCL insertion site on the posterior tibia. Associated injuries include injury of other ligaments, meniscal tear, bone injury, and joint effusion. PCL rupture is easily identified with magnetic resonance (MR) imaging by using simple signal intensity and structural characteristics. Because clinical and arthroscopic assessment of the PCL can be difficult, MR imaging can be valuable for evaluating the acutely injured knee when operative repair of the PCL is being considered.

CT diagnosis of acute appendicitis: imaging findings.

Acute appendicitis, at times, is a difficult clinical diagnosis. CT can play a valuable role in selected patients with suspected appendicitis; the CT diagnosis of acute appendicitis has high positive and negative predictive values, 96% and 95%, respectively [1]. In this essay, we review the normal CT anatomy of the appendix and the right lower quadrant and illustrate the CT signs of appendicitis and important differential diagnostic entities. The CT appearance of complications of acute appendicitis is also presented, as are issues concerning examination technique and patient preparation.

MR imaging appearance of the extensor mechanism of the knee: functional anatomy and injury patterns.

Trauma to the extensor mechanism of the knee, a common clinical problem, can be accurately evaluated with magnetic resonance (MR) imaging. The extensor mechanism consists of the quadriceps muscle and tendon, patella, patellar tendon, and patellar retinacula. Injuries of these structures can be classified into partial and complete tears. Acute injuries are associated with edema, hemorrhage, and fluid collections; chronic injuries often demonstrate redundancy, atrophy, and retraction of the affected structures. MR imaging is useful in differentiating partial and complete tears and in evaluating tissue edema and hemorrhage. It also allows detection of unsuspected nondisplaced patellar fractures and chronic conditions due to repetitive trauma. Transient dislocation of the patella is an often clinically unsuspected entity for which MR imaging can serve an important diagnostic role. A detailed understanding of the functional and anatomic relationships of the extensor mechanism can greatly assist in interpretation of MR images of the traumatized knee.

Magnetic resonance imaging of the meniscus. Advanced concepts.

Magnetic resonance imaging plays a valuable role in the evaluation of the full range of meniscal pathology including the primary diagnosis of meniscal tear, the detection of recurrent tear after resection or repair, and the demonstration of associated injuries and complications. The accuracy of MR imaging in meniscal diagnosis is dependent on the appropriate choice of MR imaging pulse sequences, imaging parameters, and diagnostic criteria. The importance of small details such as protocol parameters and image photography should not be underestimated. The role of new techniques including fast imaging sequences, three-dimensional imaging, and MR arthrography in improving meniscal diagnostic performance is under investigation and appears promising.

MR imaging of hip disorders.

Magnetic resonance (MR) imaging has been applied to the study of a variety of hip disorders, principally the evaluation of avascular necrosis. The authors reviewed their experience with MR imaging of a variety of pediatric and adult hip diseases. Attention to the details of the imaging technique is essential for maximizing the diagnostic potential of MR imaging in the work-up of hip disease. Specific protocols that incorporate surface coil imaging, oblique imaging planes, and alternative pulse sequences are the foundation of successful hip studies. Gradient-echo imaging is essential for evaluating cartilaginous disorders, particularly in pediatric patients. For patients to benefit from the diagnostic capabilities of MR imaging, an appreciation of the unique information it provides must be communicated to referring physicians. In addition, an awareness of the atypical and unique MR appearances of certain hip disorders is necessary for accurate interpretation.

Distal biceps tendon injury: MR imaging diagnosis.

PURPOSE: To review the authors' experience with magnetic resonance (MR) imaging of patients with suspected injury of the distal biceps tendon. MATERIALS AND METHODS: Twenty-one patients with clinically suspected injury of the distal biceps tendon were evaluated with MR imaging. Surgical correlation was performed in 15 patients, and long-term clinical follow-up was performed in the remaining six cases. RESULTS: Twelve complete biceps tears, four partial tears, one brachialis rupture, and one ganglion were identified. Axial MR images were more valuable than sagittal images in accurately grading distal biceps tendon injury preoperatively. There was 100% agreement between MR imaging and surgical findings. MR imaging findings led to changes in clinical treatment plans in eight patients (38%). CONCLUSION: MR imaging is useful in the evaluation of patients with suspected distal biceps tendon injury. In particular, axial MR images of the distal biceps insertion are important for accurate grading of the injury.

Evaluation of loose bodies in the elbow with MR imaging.

The evaluation of loose bodies in the elbow is usually done by means of clinical examination, radiography, and postarthrographic computed tomography (CT). The authors review their experience with magnetic resonance (MR) imaging in place of post-arthrographic CT for the evaluation of loose bodies in the elbow. The prospective interpretation of MR studies of the elbow in 20 patients was compared with arthroscopic findings. All elbows were imaged in multiple planes with thin sections, surface coils, and combinations of T1, T2, and proton-density weighting. The sensitivity for showing loose bodies with MR imaging was 100%, and the specificity was 67%. Because this was a nonblinded study, the results are biased and caution must be used when extrapolating these results to the general population. In this limited experience, MR imaging has reliably shown loose bodies in the elbow, and in the authors' institutions has replaced postarthrographic CT for that purpose.

Posterior cruciate ligament injury: MR imaging diagnosis and patterns of injury.

PURPOSE: To illustrate the variety of posterior cruciate ligament (PCL) injuries and assess the type and frequency of associated knee injuries. MATERIALS AND METHODS: In a retrospective review of 1,950 magnetic resonance (MR) examinations of the knee, 47 patients with MR imaging findings of PCL injury were identified. In 24 patients, the findings on MR images were correlated with athroscopic findings (n = 14) or findings at physical examination (n = 10). Patterns of associated injuries were described and tabulated. RESULTS: Twenty-one patients (45%) had complete PCL tears; 22 patients (47%), partial tears; and four patients (9%), bone avulsion. Associated injuries were seen in 34 patients (72%). Patterns of injuries differed from those seen in anterior cruciate ligament injury and correlated with the mechanism of trauma. CONCLUSION: MR imaging proved accurate in assessment of the PCL in patients with clinical correlation and demonstrated patterns of associated injury that may affect management strategy.