The Role of Virtual Cystoscopy, after Multidetector Computed Tomography Imaging Reconstruction without the Use of Contrast Medium, in the Diagnosis and Evaluations of Bladder Tumors: Preliminary Study.

Introduction. Although conventional cystoscopy is considered to be the gold standard for diagnosis and follow-up of bladder tumors, it remains an invasive and costly procedure. With the advent of the multidetector CT (MDCT) scanners supported by specialized software virtual cystoscopy (VC) is possible. We assess the role of VC in diagnosing and evaluating bladder lesions. Materials and Methods. Between September 2010 and October 2011, 25 consecutive patients with cystoscopically confirmed bladder tumor underwent VC. The radiologists involved in this prospective study were blinded to the exact findings. After draining any residual urine with a catheter, the bladder was retrogradely insufflated with 200-600 cc of air. No intravenous or intravesical contrast was used. MDCT scan was performed in supine and prone positions and three-dimensional reconstruction of the urinary bladder was performed. Results. The examination was well tolerated by all patients with no complications. In total, 43 lesions were detected both with conventional cystoscopy and VC. Tumor size measured by CT ranged from 3 to 80 mm in diameter. The pathological report revealed noninvasive transitional cell carcinomas in all cases. Conclusion. VC has promising results in detecting exophytic bladder lesions. In the future it could be part of the diagnostic algorithm for bladder tumors.

Mechanical and dose delivery accuracy evaluation in radiosurgery using polymer gels.

The polymer gel-Magnetic Resonance Imaging (MRI) dosimetry technique was employed to evaluate the mechanical and dose delivery accuracy in Leksell gamma knife stereotactic radiosurgery for the treatment of multiple targets. Two different polymer gel dosimeter formulations that have been reported in the literature were prepared in-house. A plan for the treatment of four brain metastases (targets) was generated. The plan involved the delivery of four, 8 mm collimator shots using different prescription isodose lines and different prescription doses for each target, keeping the maximum dose constant for all the targets. A sample of each gel formulation was irradiated using a custom made phantom with an experimental procedure capable of testing the increased nominal mechanical accuracy of stereotactic radiosurgery. The irradiated dosimeters were evaluated using a clinical 1.5 T Philips ACS NT MR imager. Result manipulation in 3-D allowed for the determination of the mechanical accuracy in the delivery of each shot through the comparison of measured versus planned shot center coordinates. Dose delivery accuracy was also evaluated by comparison of maximum dose values measured at the center of each shot as well as dose distribution measurements, with corresponding treatment planning calculations. Polymer gel dosimetry was found capable of verifying the complete chain of radiosurgery treatment in gamma knife applications involving the irradiation of multiple targets.