Time-of-flight MR arteriography of below-knee arteries with maximum-intensity-projection reconstruction: is interpretation of the axial source images helpful?

OBJECTIVE: We evaluated the extent to which detailed review of axial source images enhances the interpretation of projectional reconstructions of two-dimensional time-of-flight MR arteriograms of the tibial vessels. SUBJECTS AND METHODS: Thirty-one patients (34 limbs) with limb-threatening ischemia underwent two-dimensional time-of-flight imaging and contrast-enhanced angiography of the below-knee arteries. Maximum-intensity-projection (MIP) reconstructions of the MR arteriograms were independently interpreted by three observers. The studies were then reinterpreted after detailed review of the axial source images. A consensus reading of each study was performed as well. The observers commented on the patency of 816 vascular segments and graded the extent of disease for 272 vessels. Interobserver agreement and correlation with contrast-enhanced angiography were determined. RESULTS: On average, the addition of axial images altered the observers' interpretation of MR arteriograms in 13% of segments for patency and in 18% of vessels for grading of disease severity. For determining the patency of vascular segments, mean interobserver agreement was 0.79 without and 0.80 with axial image interpretation, and mean agreement with contrast-enhanced angiography improved from 0.69 to 0.72 with the addition of axial images. When evaluating the extent of disease, correlation between observers improved for all combinations of observers with the addition of axial images, and correlation with contrast-enhanced angiography improved for two of three observers. Based on the consensus interpretation of the MR arteriograms, review of axial images was found to improve agreement with contrast-enhanced angiography in 34 vascular segments. In addition, axial image review correctly altered the number of stenoses identified in 12 vessels. When consensus interpretation identified a vessel as patent without significant stenosis on the MIP images, the MIP-based interpretation was found to be correct in all cases. CONCLUSION: Review of axial source images provides limited benefit to interpretation of MR arteriograms of the distal lower extremity in patients with peripheral vascular disease. Although selective review of axial source images may be appropriate, axial images can improve interpretation when MIP images are complicated by the presence of patient motion, difficult anatomy, or artifacts. Axial image review may also be appropriate when a significant stenosis is identified on the MIP images.

Pearls and pitfalls in the diagnosis of ureterolithiasis with unenhanced helical CT.

Several signs to assist interpretation of unenhanced helical computed tomographic (CT) scans obtained for suspected ureterolithiasis have been described. Because signs such as perinephric stranding are not always readily apparent, a methodical approach to interpretation of CT studies is important in determining the presence or absence of ureterolithiasis. Evaluation of the poles of the kidneys is helpful in detecting subtle stranding of the perinephric fat. Inspection of the intrarenal collecting system within the poles of the kidneys is helpful in identifying subtle collecting system dilatation and can help prevent mistaking an extrarenal pelvis for hydronephrosis. Careful inspection of the ureter throughout its course is the most reliable method of distinguishing between ureteral stones and phleboliths. However, when the ureter cannot be followed antegrade, the pelvic portion can often be identified in a retrograde fashion. When secondary signs of obstruction are present but no stone is present, differential diagnostic considerations include a recently passed stone, pyelonephritis, urinary tract obstruction unrelated to stone disease, and protease inhibitor deposition disease.

The role of infrapopliteal MR angiography in patients undergoing optimal contrast angiography for chronic limb-threatening ischemia.

PURPOSE: To determine the benefit of infrapopliteal magnetic resonance angiography (MRA) in patients with chronic limb-threatening ischemia who have undergone optimal contrast angiography (CA). PATIENTS AND METHODS: Thirty-four patients (37 limbs) with limb-threatening chronic lower extremity ischemia underwent MRA and CA of the symptomatic extremity. Selective, vasodilator-enhanced digital subtraction angiography of the infrapopliteal vessels was possible for 34 limbs. Two vascular surgeons retrospectively formulated treatment plans based on CA. They then formulated treatment plans based on CA and MRA together. RESULTS: CA clearly visualized 495 of 888 vascular segments as patent, while MRA clearly visualized 412 of 888 segments. Treatment plans differed for at least one of two surgeons in eight limbs, but MRA would possibly have improved clinical outcome in only one. The amount of inflow disease did not appear to influence segment visualization or treatment planning. In eight of 11 limbs that eventually required below- or above-knee amputation, CA clearly visualized more vascular segments than MRA. One patient developed renal insufficiency after CA. CONCLUSION: Most patients undergoing optimal CA for chronic limb-threatening ischemia will not benefit from the addition of MRA. However, MRA should be considered when CA is suboptimal and when it is necessary to conserve contrast material.