Search

Objective: The purpose of this study was to evaluate the accuracy of breath-hold contrast-enhanced MR angiography in the assessment of renal artery stenosis and accessory renal arteries using a standard dose of gadolinium., Subjects and Methods: Thirty-eight patients suspected of having renal artery stenosis underwent MR angiography and intraarterial digital subtraction angiography, which was the method of reference. Three-dimensional gradient-echo MR subtraction angiography (TR/TE, 5.8/1.8 msec) was performed on a 1.5-T imager using a phased array body coil. Before imaging, a separate timing bolus sequence was used, administering 1.0 ml of contrast agent. Gadopentetate dimeglumine (15 ml) was injected using an MR power injector. Two observers, who were unaware of each other's interpretation and of MR findings, assessed digital subtraction angiography. Likewise, two other observers assessed MR angiography., Results: Digital subtraction angiography depicted 75 main and 17 accessory renal arteries (n = 92). All main renal arteries and 13 accessory renal arteries were identified on MR angiography. Compared with digital subtraction angiography, MR imaging correctly classified 57 of 66 arteries without a hemodynamically significant stenosis (0-49%), 22 of 22 arteries as significantly stenotic (50-99%), and four of four occluded arteries; five stenoses were overestimated. There was one false-positive finding of an accessory renal artery on MR angiography that was identified retrospectively on digital subtraction angiography. Interobserver agreement was high. Sensitivity and specificity for grading significant stenosis were 100% and 85%, respectively., Conclusion: Contrast-enhanced MR angiography, using +/-0.1 mmol/kg of gadolinium, is an accurate method in the assessment of renal artery stenosis and accessory renal arteries.

Objective: The purpose of this study was to evaluate a magnetization-prepared-rapid gradient-echo (MP-RAGE) sequence as a three-dimensional (3D) T1-weighted MR imaging technique to reveal lymph node metastases from carcinoma of the bladder and the prostate., Subjects and Methods: Using a 3D T1-weighted MP-RAGE sequence, MR images of 134 consecutive patients with prostatic carcinoma (n = 63) or urinary bladder carcinoma (n = 71) who were scheduled for radical prostatectomy or radical cystectomy were correlated with histopathologic findings after fine-needle aspiration biopsy (FNAB) (n = 6), open or laparoscopic pelvic lymph node dissection (n = 127), or autopsy (n = 1). MR imaging was used 10 times to guide FNAB in nine patients., Results: The sensitivity, specificity, accuracy, and positive predictive valve of the technique were 75%, 98%, 90%, and 94%, respectively. Thin-slice (1.2-mm) multiplanar reconstructed images correctly revealed diseased nodes in 33 patients. However, MR imaging failed to reveal microscopic metastatic deposits in normally sized nodes in 11 patients. Two other patients had enlarged nodes without metastasis. Furthermore, FNAB guided by MR imaging revealed metastases in six of nine patients., Conclusion: MR imaging with a 3D MP-RAGE sequence was accurate in revealing nodal metastases from carcinoma of the prostate and bladder. This imaging technique can be used to select patients for biopsy or laparoscopic pelvic lymph node dissection.

Objective: To evaluate the accuracy of MR imaging of the prostate with an endorectal surface coil in determining presence, localization, volume, and local stage of prostate carcinoma., Subjects and Methods: MR images of 34 patients with biopsy-proven cancer were correlated retrospectively with the histologic mappings of radical prostatectomy specimens. The volume and number of tumor lesions of MR images were calculated and compared with the surgical specimens used as the gold standard. Tumor stage based on MR imaging was compared with the pathologic stage according to the TNM classification. Predictive values were calculated separately for all lesions and for the lesions correctly localized with MR imaging., Results: MR imaging correctly depicted the location of 67% of the tumors. Twenty percent of the lesions depicted by MR imaging appeared to be false-positive errors. The tumors that were missed were located centrally and ventrally in the prostate. Tumor volume as shown by MR imaging was within a 25% range of the actual tumor volume in 10 cases, overestimated in 16 cases, and underestimated in eight cases. Histopathology showed capsular penetration in 12 of 34 patients (35%) and in 14 of 52 lesions (27%). Sensitivity, specificity, and positive predictive values were 43%, 84%, and 55%, respectively. Histologically, capsular penetration extended less than 1 mm into the periprostatic adipose tissue in seven patients. Sensitivity for capsular penetration less than 1 mm was 14%. Sensitivity for capsular penetration more than 1 mm was 71%. Accuracy for differentiating a pT2 from a pT3 tumor was 68%., Conclusion: Results from this study indicate that the accuracy of the technique was not satisfactory for predicting actual tumor volume. Tumor detection and localization was more accurate in the peripheral zone than in the central zone. Accuracy was poor for detecting capsular penetration of less than 1 mm, but accuracy was much better for penetration of more than 1 mm. Because recent reports suggest that capsular penetration of less than 1 mm does not adversely affect surgical cure, MR imaging still may be practical in the selection of patients for radical prostatectomy.

Objective: The purpose of this study was to evaluate a magnetization prepared-rapid gradient-echo (MP-RAGE) sequence as a three-dimensional T1-weighted MR imaging technique for staging urinary bladder cancer and to compare this technique with a commonly used two-dimensional T1-weighted spin-echo sequence technique., Subjects and Methods: For 28 consecutive patients with urinary bladder cancer, MR findings and staging results were compared with histopathologic findings after surgery or autopsy. MR imaging was performed at 1.5 T with a Helmholtz double-surface coil. Conventional T1-weighted spin-echo, three-dimensional MP-RAGE, T2-weighted spin-echo or turbo-spin-echo, and dynamic T1-weighted fast gradient-echo sequences were used. Signal difference-to-noise ratios and T1 contrast were calculated by use of operator-defined regions of interest., Results: The signal difference-to-noise ratios for fluid-tumor and fat-tumor were, respectively, factors of 1.6 and 2.7 better with T1-weighted spin-echo sequences. T1 contrast of fluid-tumor was a factor of 2.6 better with three-dimensional MP-RAGE sequences, resulting in better recognition of small tumors, ascites, and dilated ureters. T1 contrast for fat-tumor was a factor of 2.0 better with T1-weighted spin-echo sequences. With the MP-RAGE sequence, motion artifacts were fewer in number than those noted with the T1-weighted spin-echo sequence, and susceptibility artifacts were equal in number to those noted with the T1-weighted spin-echo sequence. Using the three-dimensional technique, we performed off-line reconstruction of 1- to 2-mm high-resolution images in every desired plane. Because of higher spatial resolution, the availability of multiplanar reconstructions, and better fluid-tumor contrast and despite lower signal difference-to-noise ratios, three-dimensional MP-RAGE images resulted in better recognition of local tumor extension (n = 11), adhesions and bowel wall invasion (n = 5), lymph node metastases (n = 2), and bone marrow metastases (n = 2). The staging accuracy for the combination of three-dimensional MP-RAGE, T2-weighted, and dynamic sequences was 93%; that for the combination of two-dimensional T1-weighted spin-echo, T2-weighted, and dynamic sequences was 78%. Nodal staging was also more accurate with MP-RAGE sequences (accuracy of 93% vs 86% for T1-weighted spin-echo sequences)., Conclusion: Compared with two-dimensional T1-weighted spin-echo imaging, three-dimensional MP-RAGE imaging resulted in a 15% improvement in staging. Our findings suggest that optimal staging of urinary bladder carcinoma requires three-dimensional imaging techniques.

In this article, the role of MR imaging in the management of carcinoma of the urinary bladder is reviewed and illustrated. The appearance of the normal urinary bladder and of bladder carcinoma on MR images is shown. Important factors for optimal MR imaging of urinary bladder carcinoma are reviewed. New developments such as three-dimensional and fast spin-echo sequences and the use of contrast agents, endorectal imaging, and phased array coils are discussed. Finally, the value of MR imaging in the staging of bladder carcinoma is described, and MR staging is compared with clinical staging, staging based on findings from intravesical sonography, and CT staging.

Twenty-four patients with carcinoma of the urinary bladder were examined with MR imaging by using both a conventional body coil and a newly designed wraparound double surface coil. All patients had T1- and two patients had T2-weighted pulse sequences with both coils. Because of the long examination times, T2-weighted sequences in all other patients were obtained by using the double surface coil only. Nine patients underwent radical cystectomy, while the other patients had deep transurethral tumor resection and a clinical follow-up of at least 1.5 years. The results of imaging with the surface coil showed a twofold improvement of spatial resolution compared with the images obtained with the body coil. The RF field homogeneity was excellent, and the field of view was sufficiently large to achieve a complete study of the pelvis and the lower abdomen in one sequence. For the T1-weighted images, the higher spatial resolution of the double surface coil resulted in a significant (p less than .10) improvement in tumor staging. The accuracies of double-surface-coil and body-coil imaging were 79% and 54%, respectively. Double-surface-coil imaging appears to provide better MR images of the urinary bladder than body-coil imaging does, resulting in more accurate staging of tumors on T1-weighted pulse sequences.