Noriko Kotoura

Development of a Three-dimensional Surgical Navigation System with Magnetic Resonance Angiography and a Three-dimensional Printer for Robot-assisted Radical Prostatectomy

We sought to develop a surgical navigation system using magnetic resonance angiography (MRA) and a three-dimensional (3D) printer for robot-assisted radical prostatectomy (RARP). Six patients with pathologically proven localized prostate cancer were prospectively enrolled in this study. Prostate magnetic resonance imaging (MRI), consisting of T2-weighted sampling perfection with application-optimized contrasts using different flip-angle evolutions (SPACE) and true fast imaging with steady-state precession (true FISP), reconstructed by volume rendering, was followed by dynamic contrast-enhanced MRA performed with a volumetric interpolated breath-hold examination (VIBE) during intravenous bolus injection of gadobutrol. Images of arterial and venous phases were acquired over approximately 210 seconds. Selected images were sent to a workstation for generation of 3D volume-rendered images and standard triangulated language (STL) files for 3D print construction. The neurovascular bundles (NVBs) were found in sequence on non-contrast images. Accessory pudendal arteries (APAs) were found in all cases in the arterial phase of contrast enhancement but were ill-defined on non-contrast enhanced MRA. Dynamic contrast-enhanced MRA helped to detect APAs, suggesting that this 3D system using MRI will be useful in RARP.

Evaluation of local look diffusion tensor imaging for magnetic resonance tractography of the periprostatic neurovascular bundle

The purpose of this study was to compare diffusion tensor imaging using the local look technique and sensitivity encoding for tractography of the periprostatic neurovascular bundle. We compared the surrounding tissues of the prostate in eight healthy volunteers. The results of tractography in terms of the numbers of fibers and the fractional anisotropy map were evaluated. Distortion was evaluated using the dice similarity coefficient between isotropic diffusion images created from diffusion tensor images and T2-weighted images. The number of lines in tractography was significantly greater in diffusion tensor imaging using the local look technique (p < 0.001). Although there was no difference in image distortion of the prostate between methods, an artifact appeared in the center of the diffusion tensor image using sensitivity encoding. In conclusion, diffusion tensor imaging using the local look technique was superior to that using sensitivity encoding for tractography of the periprostatic neurovascular bundle.

The Measurement of X-ray Fluoroscopy Input-output Characteristics in Angiography System

PURPOSE Determination of X-ray fluoroscopy radiation dose and contrast with angiographic system automatically depending on the objects, and to control setting manually, which is difficult for the measurement of characteristics. Therefore, we examined the method to adjust the conditions of fluoroscopy and measured the input-output characteristics. METHOD To adjust and fix the condition of fluoroscopy, the exposure adjustment area at the center of the irradiation field was moved to the left side and attached the copper plates to regulate the exposure dose. The area to measure the digital value was selected at the center of the irradiation field, and the dosimeter was placed at the right side of the area, which was selected to measure the digital value. To regulate the entrance dose progressively, the acryl plates were inserted into the irradiation field except for the exposure adjustment area. We obtained a characteristic curve from the measured dose and the digital value. Difference of lookup table (LUT), dose dependency, and tube voltage dependency were checked by the digital characteristic curves. RESULT Each LUT showed different curves, but they all saturated with 4095, which is the maximum value of 12 bits. Dose dependency was measured as an increase in the permitted dose level with an increase in the setting dose. Tube voltage dependency improved with the tube voltage rises. Each characteristic curve became same by converting the relative exposure dose. As a result, measuring the shape of LUT would be possible. CONCLUSION The method is useful for measuring the characteristic curve with the X-ray fluoroscopy of angiographic system.