CT angiography: in vitro comparison of five reconstruction methods.

OBJECTIVE: Five image reconstruction techniques have been used with CT angiography: axial (cross-sectional), maximum intensity projection (MIP), curved multiplanar reconstruction (MPR), shaded-surface display, and volume rendering. This study used a phantom to compare the accuracy of these techniques for measuring stenosis. SUBJECTS AND METHODS: A 19-vessel phantom containing various grades of concentric stenoses (0-100%) and three lengths (5, 7.5, and 10 mm) of stenoses was used for this study. Scans were obtained with a slice thickness of 2.0 mm, slice interval of 1.0 mm, pitch of 1.0, 120 kVp, 200 mA, and with the vessels oriented parallel to the z-axis and opacified with nonionic contrast material. CT angiography images were produced using five optimized techniques: axial, MIP, MPR, shaded-surface display, and volume rendering; and measurements were made with an electronic cursor in the normal lumen and mid stenosis by five separate investigators who were unaware of vessel and stenosis diameters. Each of the techniques was first optimized according to the radiology literature and our own preliminary testing. RESULTS: For vessels greater than 4 mm in diameter, axial, MIP, MPR, shaded-surface display, and volume-rendering CT angiography techniques all had a measurement error of less than 2.5%. However, axial, MIP, MPR, and shaded-surface display techniques were less accurate in estimating smaller (

Knee in early juvenile rheumatoid arthritis: MR imaging findings.

PURPOSE: To determine the magnetic resonance (MR) imaging findings in the knee in early juvenile rheumatoid arthritis. MATERIALS AND METHODS: MR imaging (1.5 T) was performed in the more symptomatic knee in 30 children with juvenile rheumatoid arthritis with a symptom duration 1 year or less. Conventional, fast spin-echo, three-dimensional gradient-echo, and gadolinium-enhanced T1-weighted images were assessed. Two radiologists independently read the images, and a third resolved disagreements. These images were compared with knee radiographs in 27 children. RESULTS: Mean maximal synovial thickness was 4.8 mm +/- 2.4 (SD). Mean synovial volume was 15.4 mL +/- 10.8. Suprapatellar joint effusions were seen in 26 (87%) of 30 knees, meniscal hypoplasia in 11 (37%) of 30 knees, and abnormal epiphyseal marrow in eight (27%) of 30 knees. Three knees had articular cartilage contour irregularity, fissures, and/or thinning. One knee had a bone erosion. Knee radiographs showed suprapatellar fullness in 78% of the knees, joint space narrowing in one knee, and no bone abnormalities. CONCLUSION: Synovial hypertrophy and joint effusions are the most frequent MR imaging findings of knees in early juvenile rheumatoid arthritis. Early in the disease, radiographically occult cartilage and bone erosions are uncommonly seen at MR imaging. The potential relationship of synovitis to cartilage abnormalities deserves further study.

Comparative assessment of CT and sonographic techniques for appendiceal imaging.

OBJECTIVE: We performed a comparative assessment of CT and sonographic techniques used to assess appendicitis. MATERIALS AND METHODS: One hundred patients with clinically suspected acute appendicitis were examined with sonography, unenhanced focused appendiceal CT, complete abdominopelvic CT using IV contrast material, focused appendiceal CT with colonic contrast material, and repeated sonography with colonic contrast material. Each sonogram was videotaped for subsequent interpretation by three radiologists and two sonographers. The mean sensitivity, specificity, positive and negative predictive values, inter- and intraobserver variability, and diagnostic confidence scores of all observers were used for comparative performance assessments. The three CT examinations were filmed and interpreted separately by four radiologists. Patient discomfort was assessed on a 10-point scale for each radiologic study. Diagnoses were confirmed by pathologic evaluation of resected appendixes or clinical follow-up for a minimum of 3 months after presentation. RESULTS: Twenty-four of the 100 patients had positive findings for acute appendicitis. Both sonographic techniques had high specificity (85-89%) and comparable accuracy (73-75%) but low sensitivity (33-35%) and inter- and intraobserver variability (kappa = 0.15-0.20 and 0.39-0.42, respectively). Unenhanced focused appendiceal CT, abdominopelvic CT, and focused appendiceal CT with colonic contrast material all significantly outperformed sonography (p <0.0001), with sensitivities of 78%, 72%, and 80%; specificities of 86%, 91%, and 87%; and accuracies of 84%, 87%, and 85%, respectively. Abdominopelvic CT gave the greatest confidence in cases with negative findings (p = 0.001), and focused appendiceal CT with colonic contrast material gave the greatest confidence for cases with positive findings (p = 0.02). In terms of inter- and intraobserver variability, focused appendiceal CT with colonic contrast material yielded the highest, and unenhanced focused appendiceal CT the lowest, agreement (interobserver kappa = 0.45 vs. 0.36 and intraobserver kappa = 0.85 vs. 0.76, respectively) (p <0.05). Colonic contrast material was unsuccessfully advanced into the cecum in 18% of patients and leaked in another 24%. Patient discomfort was greatest with focused appendiceal CT using colonic contrast material and least with unenhanced focused appendiceal CT (p <0.05). CONCLUSION: A standard abdominopelvic CT scan is recommended as the initial examination for appendicitis in adult patients. However, focused appendiceal CT with colonic contrast material material should be used as a problem-solving technique in difficult cases.

Deep venous thrombosis after percutaneous insertion of vena caval filters.

PURPOSE: A large multicenter study has recently questioned the overall clinical efficacy of vena caval filters, especially when inserted prophylactically, because of the subsequent development of deep venous thrombosis (DVT) at the insertion site. We examined the incidence of this complication with newer, smaller diameter percutaneous devices. METHODS: We reviewed our vascular surgery and interventional radiology clinical registries to identify patients in whom a femoral percutaneous vena caval filter had been placed from 1993 to 1998. This list was cross referenced with patients who had undergone lower extremity venous ultrasound scan examinations for the diagnosis of DVT in the vascular laboratory within a 60-day period before and after the insertion of the filter device. RESULTS: A total of 35 patients during this 5-year period had timely follow-up venous duplex scan studies performed. The indications for filter placement were DVT in 16 patients (46%), pulmonary embolus in 13 patients (37%), DVT and pulmonary embolus in three patients (9%), and prophylactically in three patients (9%) at high risk for thromboembolization. Of the patients with documented thromboembolic events, 91% (29 of 32) had contraindications to anticoagulation therapy, and the remaining 9% (3 of 32) represented failure of anticoagulation therapy. A Greenfield filter was used in 13 patients (37%), a Simon Nitinol filter was used in 11 patients (31%), and a VenaTech filter was used in nine patients (26%). The other two patients (6%) had a Bird's Nest filter inserted. At a mean follow-up period of 12 +/- 2 days (median, 6 days), there was a 40% (14 of 35) incidence of proximal DVT in venous segments without evidence of thrombus before filter insertion. The majority (71%; 10 of 14) occurred in the common femoral vein, with three located in the superficial femoral vein and one in the external iliac vein. The lowest incidence of DVT was seen with the Greenfield and Bird's Nest filters as compared with the smaller Simon Nitinol and VenaTech filters (20% vs 55%; P < .05). The highest incidence of thrombosis occurred in patients with pre-insertion pulmonary emboli (50%; 8 of 16) as compared with those patients with DVT (38%; 6 of 16) and prophylactic insertion (0%; 0 of 3). However, the subgroups were too small to attain statistical significance. CONCLUSION: There is a continuing and significant incidence of new DVT development ipsilateral to the percutaneous femoral insertion site of vena caval filters. The smaller diameter filters are not associated with a lower incidence of femoral thrombosis.

A national survey of practice patterns in the noninvasive diagnosis of deep venous thrombosis.

PURPOSE: Recent studies have recommended unilateral venous duplex scanning for the diagnosis of deep venous thrombosis (DVT) in patients who are unilaterally symptomatic. Vascular laboratory accreditation standards, however, imply that bilateral leg scanning should be performed. We examined whether actual practice patterns have evolved toward limited unilateral scanning in such patients. METHODS: A questionnaire was mailed to all 808 vascular laboratories in the United States that were accredited by the Intersocietal Commission for the Accreditation of Vascular Laboratories (ICAVL). To encourage candid responses, the questionnaires were numerically coded and confidentiality was assured. RESULTS: A total of 608 questionnaires (75%) were completed and returned. Most of the respondents (442; 73%) were either community-hospital or office-based laboratories, and the remaining 163 (27%) were university or affiliated-hospital laboratories. Most of the laboratories (460; 76%) had been in existence for 9 years or more, and 65% had been ICAVL-accredited in venous studies for 3 years or more. Board-certified vascular surgeons were the medical directors in 54% of the laboratories. Duplex ultrasound scanning was the diagnostic method used by 98% of the laboratories. In patients with unilateral symptoms, 75% of the laboratories did not routinely scan both legs for DVT. A large majority (75%) believe that bilateral scanning is not clinically indicated. Only 57 laboratories (14%) recalled having patients return with a DVT in the previously unscanned leg, with 93% of these laboratories reporting between one and five such patients. This observation correlated with larger volumes of venous studies performed by those laboratories (P <.05). Similarly, only 52 laboratories (12%) recalled having patients return with subsequent pulmonary emboli. Of these laboratories, only five reported proximal DVT in the previously unscanned legs of such patients. Of all these laboratories, therefore, only 1% (5 of 443) have potentially missed the diagnosis of a DVT that caused a preventable pulmonary embolus with such a policy. Among those laboratories that always perform bilateral examinations, 41% do so because of habit. Most (61%) of the laboratories that perform bilateral scanning would do unilateral scanning if it were specifically approved by ICAVL. CONCLUSION: Three quarters of the ICAVL-accredited vascular laboratories perform limited single-extremity scanning for the diagnosis of DVT in patients with unilateral symptoms. This broad clinical experience suggests that this practice is widespread in selected patients. Clinical protocols should be established to provide guidelines for local laboratory implementation.

Fibrolipoma of the median nerve: MRI.

The MRI findings of two patients with fibrolipoma of median nerve are presented. A characteristic 'cable-like' appearance of the tumour was present on T1-weighted images. Unique imaging features of these cases included extension of the lesion into the radial digital nerve of the index finger in case 1 and extraneuronal extension of a exophytic fatty mass from the median nerve into the thenar eminence in case 2.

Magnetic resonance imaging in juvenile rheumatoid arthritis.

OBJECTIVES: This study was undertaken to examine the role of magnetic resonance imaging (MRI) in the management of patients with juvenile rheumatoid arthritis (JRA). METHODS: A Medline search was performed to identify all publications pertaining to MRI in JRA. Further searches and identification of articles from bibliographies identified articles pertaining to plain radiograph imaging in JRA and MRI in adult rheumatoid arthritis. RESULTS: Studies in both children and adults have shown superiority of MRI to plain radiography in detecting synovial hypertrophy and articular cartilage abnormalities. Several studies in adults have shown a good correlation of MR images with gross anatomic as well as histological findings at arthroscopy. Biochemical changes that occur before structural changes within the joint may even be detectable with magnetic resonance spectroscopy. CONCLUSIONS: MRI holds promise for the assessment of disease progression in JRA and may be useful in serial evaluation, as in clinical trials.

Multicenter trial to evaluate vascular magnetic resonance angiography of the lower extremity. American College of Radiology Rapid Technology Assessment Group.

OBJECTIVES: To assess the value of magnetic resonance angiography (MRA) in presurgical evaluation of patients with severe lower limb atherosclerotic occlusive disease and to assess the feasibility of rapidly conducting rigorous technology assessment. DESIGN: Blinded, prospective study of consecutive patients with signs or symptoms of severe infrainguinal peripheral vascular disease who were candidates for percutaneous or surgical intervention. Using both descriptive statistics and multivariate logistic analyses, MRA was compared with contrast arteriography (CA) (the current technique) for imaging 15 arterial segments of the leg and foot. Intraoperative contrast angiography was the "gold" standard. Also studied was the effect of adding MRA to the information used in planning treatment. SETTING: Six US hospitals, one a community hospital. PATIENTS: A total of 155; 84% with either rest pain or tissue loss. RESULTS: Sensitivity in distinguishing patent segments from completely occluded segments was 83% for CA and 85% for MRA; both had 81% specificity. For distinguishing near-normal segments (suitable as bypass graft termini), CA was less sensitive than MRA (77% vs 82%), but more specific (92% vs 84%). After adjusting for same-reader effects, odds of correctly distinguishing patent segments were 1.6 times as great for MRA as for CA (P < .01); for distinguishing near-normal segments, the odds for CA were 1.5 times as great as for MRA (P < .05). The addition of MRA changed the treatment plan in 13% of patients; in 86% of these cases, the surgery actually performed indicated that the MRA-inclusive plan was superior. CONCLUSIONS: Individually, MRA and CA are approximately equivalent in diagnostic accuracy. The addition of MRA to treatment plans based only on CA and other diagnostic information clearly improves the plans. Completed in 15 months (as planned), our study demonstrates the feasibility of conducting rigorous technology assessment rapidly enough to be timely even in fields in which diagnostic and treatment techniques are rapidly changing.

MR imaging of soft-tissue masses: diagnostic efficacy and value of distinguishing between benign and malignant lesions.

OBJECTIVE: The purpose of this study was to evaluate the efficacy of MR imaging in predicting the pathologic diagnosis of soft-tissue masses, both neoplastic and nonneoplastic, and in distinguishing benign from malignant lesions. MATERIALS AND METHODS: The imaging features of 225 soft-tissue tumors (179 benign, 46 malignant) in 222 patients were analyzed. Univariate analysis of multiple individual imaging features was done, along with stepwise logistic regression analysis of combinations of imaging features, to determine how useful these are for predicting malignancy or benignity. A subjective (group consensus) analysis of each case was done prospectively, and each tumor was placed into one of three diagnostic categories: (1) benign, diagnostic of a specific entity; (2) nonspecific, most likely benign; or (3) nonspecific, most likely malignant. Results were compared with the final diagnosis established by pathologic examination (n = 184) or imaging/clinical data (n = 41). RESULTS: By quantitative analysis, no single imaging feature or combination of features could reliably be used to distinguish benign from malignant lesions. For the subjective analysis, a correct and specific benign diagnosis could be made on the basis of MR imaging findings in 100 (44%) of the 225 tumors. For the entire cohort, the sensitivity was 78%, the specificity was 89%, the positive predictive value was 65%, and the negative predictive value was 94% for a malignant diagnosis. When the diagnostic benign tumors were excluded, the specificity and negative predictive value decreased to 76% and 86%, respectively, whereas the sensitivity and positive predictive value remained the same. CONCLUSION: Many benign soft-tissue masses can be correctly and confidently diagnosed with MR imaging. The prevalence of benign lesions among soft-tissue masses accounts for the relatively high specificity and negative predictive value that can be achieved with MR imaging for tissue characterization. However, the accuracy of MR imaging declines when these characteristic benign tumors are excluded from analysis. A significant percentage of malignant lesions may appear deceptively "benign" with the currently used criteria. For lesions whose imaging appearance is nonspecific, MR imaging is not reliable for distinguishing benign from malignant tumors, and these lesions warrant biopsy in most cases.

Rheumatoid arthritis: evaluation of wrist extensor tendons with clinical examination versus MR imaging--a preliminary report.

To determine whether magnetic resonance (MR) imaging can improve assessment of the extensor tendons of the wrist and their propensity to rupture, the dorsal tendons in 23 wrists in 20 patients with rheumatoid arthritis were clinically assessed and then examined with MR imaging. Clinical and MR imaging evaluations were performed blindly and independently. The six extensor tendon compartments were assessed with MR imaging for presence of pannus, synovial effusion, and tendon involvement or rupture. Clinical scores of systemic disease, dorsal tendon sheath swelling, and risk of tendon rupture ranged from 0 to 3 in each category; the overall score was not associated with any MR imaging category. Clinical assessment of enlargement of the dorsal tendon sheath and clinical risk of rupture correlated poorly with findings on MR images. All eight wrists with clinically minimal risk of rupture had pannus, effusions, and tendon involvement on MR images; the findings were similar in the wrists with moderate (grade 2) risk of rupture. MR imaging depicts involvement of the dorsal tendon sheath and dorsal tendons that cannot be assessed with other radiologic or clinical means.

Intrinsic and extrinsic carpal ligaments: evaluation by three-dimensional Fourier transform MR imaging.

OBJECTIVE: As evaluation of the anatomic and functional integrity of intrinsic and extrinsic carpal ligaments with conventional imaging methods is difficult, we designed a study to evaluate the ability of three-dimensional Fourier transform MR imaging to show the carpal ligaments. SUBJECTS AND METHODS: We obtained coronal MR images of 15 cadaveric wrists and 15 wrists of patients, using three-dimensional volume acquisition with a gradient-recalled echo sequence and a 1.5-T magnet. The MR findings were compared with the findings on dissection in the 15 cadaveric wrists and with the surgical findings in eight patients. RESULTS: All the volar ligaments had a striated appearance on MR images, with alternating bands of low and intermediate signal intensity. No tears of the extrinsic ligaments were seen. The intrinsic scapholunate and lunotriquetral ligaments were seen as structures with more homogeneously intermediate intensity attaching to their adjacent bone through high-signal-intensity hyaline cartilage. For the cadaveric wrists, MR indications of a tear of the scapholunate ligament were true-positive in three and false-negative in three; indications of a tear of the lunotriquetral ligament were true-positive in five, false-positive in two, and false-negative in one. For the eight patients with surgical confirmation, the MR findings regarding tears were true-positive in two and true-negative in six. Neither surgery nor MR imaging showed any tears of the scapholunate ligament. CONCLUSION: Three-dimensional Fourier transform MR imaging with thin slices provides the resolution necessary to visualize the anatomic detail of the extrinsic and intrinsic ligaments of the wrist, but additional clinical experience with this technique will be required to determine its diagnostic capabilities.