Diffusion-Weighted Image in Correlation with T2 Sequence as an Imaging Biomarker for Urinary Bladder Cancer

Abstract
Background: Recent functional diagnostic imaging tech-niques have emphasized the role and importance of MRI in pelvic organs imaging. Functional imaging by means of Diffusion-Weighted Magnetic Resonance Imaging (DW-MRI) and ADC value are now considered an essential part of the standard imaging protocols for evaluation of the pelvic organs.
DWI depends on the fact that water molecules can diffuse freely in low cellular tissues, while increased cellularity restricts its diffusion, a phenomenon called 'Brownian motion'. Therefore, in cases of malignant lesions which have high cellularity, water diffusion is restricted and appear as bight lesions, in contrary to most benign tumors which have low cellularity.
Aim of Study: To assess the diagnostic value of DWI in correlation with T2WI for preoperative urinary bladder tumor T-staging.
Patients and Methods: This is a prospective study that included twenty-six patients with hematuria and suspicious urinary bladder mass lesion on ultrasonography, age ranged from 54 to 70 years old, 22 patients were male while 4 were female. The patients were referred from the Urology Clinics, Ain Shams University, before cystoscopy and initial biopsy confirmation. MRI examination with DWI and T2WI was performed at the Radiology Department of Ain Shams Uni-versity Hospital in a period of 6 months from January to June 2018.
Results: In this study, 24 patients were confirmed to have urinary bladder cancer while one patient had nonspecific inflammatory reaction and another patient had infiltrating prostatic cancer. Regarding the detection of urinary bladder carcinoma the overall sensitivity, specificity, and accuracy using T2 images alone were 71.8, 73.2 and 72.4%, respectively, using DWI alone were 87.8, 87.8 and 88%, respectively and by using T2 plus DWI images were 87.8, 95.5 and 91.6%, respectively. The ADC value of 0.8 X 10–3mm2/sec was found to be a cut off value for differentiating low grade tumors (grade I-II) from high grade tumors (grade III) with sensitivity, specificity and accuracy of 71, 55.5 and 65% respectively.
Conclusion: DWI has several advantages that can provide information regarding the lesion's size, number, location, local staging. The estimation of ADC value helps to predict the tumor nature and grade. The sensitivity and accuracy of DWI is higher when correlated with T2WI, which greatly help in guiding the surgeons performing conventional cystoscopy.