Utility of diffusion-weighted MRI in the diagnosis of bladder carcinoma.

BACKGROUND

The purposes of our study were to investigate the feasibility of diffusion-weighted imaging in the detection of malignant bladder tumors, with comparison to the high-resolution thin-section fast spin-echo (FSE) T2-weighted MRI, and also to compare the apparent diffusion coefficient (ADC) values of the bladder tumors with the surrounding structures.

MATERIAL AND METHODS

Fifty-three consecutive patients consisting of 44 males and 9 females who presented with a bladder mass were prospectively enrolled in this study. Mean age was 62.53 ± 12.03 (age range, 33-86 years). These patients were evaluated by high-resolution thin-section FSE T2-weighted and diffusion-weighted MRI for the detection of bladder masses. Following MRI, within 2 weeks, all patients were subjected to either surgery or cystoscopic biopsy, and the obtained histopathological proofs were used as the reference standard. Furthermore, ADC values of the bladder tumors, urine, the normal bladder wall, the central and peripheral zones of the prostate, the seminal vesicule, and the uterus outer myometrium were also calculated. ADC values of the bladder carcinomas and the related surrounding structures were compared as to whether a statistically significant difference was present or not.

RESULTS

In a total of 47 patients, consisting of 39 males and 8 females, bladder carcinomas were clearly shown as having conspicuous high and intermediate signal intensity masses, relative to the surrounding structures on diffusion-weighted and T2-weighted images, respectively. An 89% sensitivity and a 100% positive predictive value were obtained for both FSE T2-weighted and diffusion-weighted MRI in the diagnosis of bladder carcinoma. Mean ADC values and standard deviations of the bladder tumors and the surrounding structures were as follows: bladder carcinomas (n=47): 1.28 ± 0.31, normal bladder wall (n=47): 1.98 ± 0.41, urine (n=47): 3.12 ± 0.24, seminal vesicle (n=39): 1.82 ± 0.33, peripheral zone of prostate (n=39): 1.80 ± 0.29, central zone of prostate (n=39): 1.55 ± 0.33, and uterus outer myometrium (n=8): 1.53 ± 0.19. It can be clearly seen that the mean ADC values of the bladder carcinomas were significantly lower than the surrounding structures (P<.05).

CONCLUSION

High-resolution thin-section FSE T2 and diffusion-weighted MRI show high diagnostic performance and are comparable in the detection of bladder tumors. Diffusion-weighted MRI provides high quality images of the malignant bladder tumors against a suppressed background signal. Diffusion-weighted MRI using ADC measurements may be useful in the evaluation of tumor invasion to the adjacent organs.