Upper-extremity venography: CO2 versus iodinated contrast material.

PURPOSE: To determine prospectively the diagnostic performance of CO(2) venography, by using conventional venography with iodinated contrast material as the reference standard, for the preoperative evaluation of upper-limb and central veins before creation of fistulas for hemodialysis access. MATERIALS AND METHODS: The study was approved by the institutional review board, and informed consent was obtained from all patients. Twenty-two patients underwent comparative CO(2) and conventional venography of upper-extremity and central veins. Two independent observers evaluated the opacification of the veins and grade of stenosis, if present. Interobserver agreements were estimated with the Cohen kappa coefficient. Calculations of sensitivity, specificity, and accuracy were used for intertechnique observations. RESULTS: For CO(2) venography, global interobserver agreement was good, with a kappa value of 0.90 (range, 0.71-1.00; 95% confidence interval: 0.84, 0.95). A kappa value of 0.96 (range, 0.86-1.00; 95% confidence interval: 0.93, 0.99) was calculated for global interobserver agreement for conventional venography. The sensitivity, specificity, and accuracy of CO(2) venography for all vein segments were 97%, 85%, and 95%, respectively. CONCLUSION: CO(2) venography had a sensitivity of 97% and a specificity of 85% in the assessment of upper-limb and central vein patency and stenosis, with conventional venography used as the reference standard.

Clinical validation of high-resolution fast spin-echo MR colonography after colon distention with air.

To evaluate the feasibility of MR colonography (MRC) with air using two-dimensional (2D) T1-weighted fast spin-echo (T1wFSE) in patients scheduled for conventional colonoscopy (CC) after classic bowel preparation, and assess the ability of the technique to detect colonic lesions. The distention was sufficient for diagnosis, and the technique provided adequate delineation of the wall in the majority of segments. Residual fluid obscured the wall in different segments, especially in the ascending and descending colon (supine position) and in the cecum, transverse, and sigmoid colon (prone position). These findings were consistent with CT colonography. MRC visualized three lesions, missed one lesion >10 mm, visualized none of four lesions <5 mm, and yielded one false-positive lesion (5-10 mm). Missed lesions can be due to inconsistency in the slice positions between consecutive breath-holds, which is inherent to the multishot technique. Residual fluid may have obscured the smaller lesions. The shortcomings of the technique are limited coverage and signal drop-off at the borders of the field of view (FOV). Before multishot 2D T1wFSE colonography can become a valid screening method, improved patient preparation and a more practical technique are needed.

Combined T1-T2 mapping of human femoro-tibial cartilage with turbo-mixed imaging at 1.5T.

PURPOSE: To evaluate the influence of Gd-DTPA on cartilage T2 mapping using turbo-mixed (tMIX) imaging, and to show the possible usefulness of the tMIX technique for simultaneously acquiring T1 and T2 information in cartilage. MATERIALS AND METHODS: Twenty volunteers underwent MRI of the knee using the tMIX sequence before and after gadolinium administration. T1 and T2 maps were calculated. The mean T1 was determined on the pre- and postcontrast T1 maps. T2 relaxation values before and after gadolinium administration were statistically analyzed. RESULTS: The obtained relaxation values are in correspondence with previously published data. The mean T1 before gadolinium administration was 449 msec +/- 34.2 msec (SD), and after gadolinium administration it was 357 msec +/- 55.8 msec (SD). The postcontrast T1 relaxation range was 221.5-572.8 msec. The mean T2 of the precontrast T2 maps was 34.2 msec +/- 3.1 msec (SD), and the mean T2 of the postcontrast T2 maps was 32.5 msec +/- 3.1 msec (SD). These are statistically significant different values. A correction for the postcontrast T2 values, using a back-calculation algorithm, yielded a 98% correlation with the precontrast T2 values. CONCLUSION: The absolute difference of pre- and postcontrast T2 is very small and is ruled out using the back-calculation algorithm. Combined T1-T2 tMIX cartilage mapping is a valuable alternative for separate T1 and T2 cartilage mapping.

T2 mapping of human femorotibial cartilage with turbo mixed MR imaging at 1.5 T: feasibility.

The feasibility of a high-spatial-resolution technique for mapping T1 and T2 in articular cartilage in the human knee was evaluated. The technique, turbo mixed magnetic resonance (MR) imaging, is based on a pulse sequence in which inversion-recovery and spin-echo measurements are interleaved. The sequence was first validated in a phantom experiment in which T1 and T2 values obtained with an accepted spectroscopic technique were correlated with those obtained by using a clinical magnetic resonance imager with the turbo mixed technique. T2 maps were obtained with turbo mixed imaging in 25 volunteers (17 men, eight women; mean age, 30.8 years; range, 23-45 years). A high correlation (r = 0.99) was found between T1 and T2 values obtained at spectroscopy and those obtained at turbo mixed imaging. Relative differences in the range of cartilage relaxation times between the two techniques were less than 20%. Turbo mixed imaging in human volunteers showed T2 cartilage relaxation times that corresponded with previously published data. Turbo mixed imaging, thus, is feasible for T2 mapping of cartilage.

High-spatial-resolution 3D balanced turbo field-echo technique for MR angiography of the renal arteries: initial experience.

PURPOSE: To compare a multislab balanced turbo field-echo magnetic resonance (MR) angiographic technique, without the use of a contrast agent, with digital subtraction angiography (DSA) for imaging of the renal arteries. MATERIALS AND METHODS: Twenty-five randomly selected patients (eight women and 17 men; age range, 27-88 years; mean age, 72 years) suspected of having renal artery stenosis underwent both DSA and balanced turbo field-echo MR angiography. A consensus result was obtained among three radiologists in evaluation of main renal arteries on balanced turbo field-echo images and DSA images. Sensitivity, specificity, and negative and positive predictive values of the balanced turbo field-echo technique were calculated, and receiver operating characteristic analysis was performed for depiction of hemodynamically significant stenosis. Cohen kappa analysis was used to assess agreement between the two imaging methods in grading of stenoses and depiction of significant stenosis. Accessory renal arteries also were evaluated. RESULTS: Fifty main renal arteries and 11 accessory arteries were fully depicted with DSA. DSA depicted 11 stenotic lesions in the main renal arteries. In comparison, balanced turbo field-echo MR angiography enabled visualization of 46 of 50 main renal arteries to their first branching points and depicted 10 of 11 accessory arteries. Sensitivity, specificity, negative predictive value, and positive predictive value of this technique for depiction of significant stenosis were 100% (four of four), 98% (41 of 42), 100% (41 of 41), and 80% (four of five), respectively. The area under the receiver operating characteristic curve was 0.988. kappa was 0.782 for grading of stenoses and 0.877 for depiction of significant stenosis. CONCLUSION: Multislab balanced turbo field-echo imaging has potential as an MR angiography technique for depiction of normal and diseased renal arteries.