الفهرس 
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Abstract
The aim of this study was to evaluate the role of the multiparametric MRI combining the conventional MR imaging techniques (including the T1-WI, T2-WI and the high resolution T2W-MRI) and the functional MR imaging techniques (including the DW-MRI and the DCE-MRI) in the characterization and local staging of urinary bladder carcinoma.
Fifty patients with a presumed diagnosis of bladder carcinomas were included in this prospective study. Imaging was performed with a 1.5 T MRI scanner with 18-channel and phased array pelvic coil. Pelvic MRI was performed for all patients in the supine position. The entire pelvis was imaged from the aortic bifurcation to the inferior margin of the pubic symphysis.
Confirmation of the findings was done by histopathological data obtained either from cystoscopy and biopsy, TURBT or radical cystectomy. Histolopathological staging and grading was performed. The histopathological results of tumors stages and grades were used as the reference gold standard. Histopathologic staging was conformed to the updated TNM system of the International Union against Cancer. Histopathologic grading also conformed to the World Health Organization two-tiered classification system for bladder cancer grading.
Each magnetic resonance image set were interpreted and the tumors were assigned a T stage on a stage-by-stage basis. The DW-MRI and the DCE-MRI were interpreted referred to the T1-W and the T2-W image sets. The combined multiparametric MRI data were interpreted and the final local T stages of the tumors were assigned.
The accuracy of the high resolution T2W-MRI, the DW-MRI, the DCE-MRI, the combined image sets and the combined multiparametric MRI in the local T staging of bladder carcinomas were evaluated using the histopathological findings as the reference gold standard. The data were regrouped to evaluate the accuracy of each imaging set, the combined image sets and the multiparametric-MRI in distinguishing nonmuscle invasive from muscle invasive tumors and organ-confined from non-organ-confined tumors.
The presence of the preserved submucosal linear enhancement detected in the DCE-MRI and the positive inchworm sign detected in the DW-MRI were only identified in superficial non-muscle invasive carcinomas helping in their differentiation from the muscle invasive lesions.
The diagnostic accuracy in local staging of urinary bladder carcinoma increased from 52% in the high resolution T2W-MRI to 74% in the DCE-MRI and to 82% in the DW-MRI and to be the highest 88% in the combined multiparametric-MRI assessment.
The diagnostic accuracy of the multiparametric MRI assessment (88%) was superior to the DW-MRI (82%), to the DCE-MRI (74%) and to the high resolution T2W-MRI (52%) in differentiating the nonmuscle invasive from the muscle invasive tumors and in differentiating the organ-confined from the non-organ-confined tumors respectively.
The extent of agreement between the multiparametric MRI and the histopathological staging of the examined cases (κ=0.782) were greater than the DW-MRI (κ=0.679) and than the DCE-MRI (κ=0.566) and the high resolution T2W-MRI (κ=0.274); denoting the higher diagnostic performance and accuracy of the combined multiparametric MRI assessment than the other image sets.
Overstaging was reduced from 48% using the high resolution T2W-MRI, to 26% using the DCE-MRI, to 18% using the DW-MRI and only to 12% using the combined multiparametric-MRI assessment. No understaging was detected in the study.
DW-MRI was very accurate in the detection of urinary bladder carcinomas with all the lesions showed restriction and hyperintense signals in the high b value (b1000) images. The ADC values measured in urinary bladder carcinomas (mean=0.87±0.26×10-3mm2/s) were significantly lower when compared with that of the normal bladder wall (mean=1.57±0.17×10-3mm2/s) and when compared with that of urine (mean=2.93±0.25×10-3mm2/s). The ADC values were also significantly lower in high grade carcinomas (mean=0.722±0.13×10-3mm2/s) than in low grade carcinomas (mean=1.22±0.09×10-3mm2/s).This allowed accurate detection and grading of the urinary bladder neoplastic lesions.
Receiver operating characteristic curve (ROC) analysis was performed and a cut-off ADC value of ≤1.36×10-3mm2/s was found to be the best differentiating urinary bladder carcinoma from the normal bladder wall. A cut-off ADC value of ≤1.012×10-3mm2/s was also found to be the best differentiating the high grade from the low grade carcinomas. So, the DW-MRI helped in the accurate prediction of the tumor histological grades.
The study also showed restriction and significant low ADC values of the involved metastatic local and regional lymph nodes with their mean ADC values = 0.81± 0.15×10-3mm2/s. This was adding in the adequate detection, characterization and in the local staging of the metastatic lymph nodes.
The DCE-MRI constructed time-intensity curves were also obtained from the from the urinary bladder carcinomas, evaluated and graded according to their patterns of enhancement into grade 1, grade 2 and grade 3 curves. There is a significant correlation was found between the grades of the DCE-MRI time-intensity curves and their corresponding histopathological grades, helping in predicting the histological grades of the urinary bladder tumors.
When multiple urinary bladder tumors detected; the multiparametric MRI was accurate in the identification of the different tumors stages and grades seen in carcinomas. It helped in the identification of the higher stages and grades lesions. So before cystoscopy and histopathological sampling, more accurate predictions can be made about the malignant potential of urinary bladder lesions reducing the sampling error and directing the surgeon to the lesions of more concern.
So; the multiparametric MRI assessment showed its greater accuracy and increased diagnostic performance in the detection of the neoplastic lesions and in the adequate determination of the local T stages and the histological grades of the urinary bladder cancers than the single image sets. It also predicted the nature and stages of the local lymph nodes and exhibited high diagnostic performance.