Search

I-125 permanently implanted sealed-source radiotherapy is one of the treatments for early localized prostate carcinoma. In order to choose treatment parameters such as the number of implanted sources, accurately determining the volume of the prostate is vital for this type of therapy. We compared the usefulness of transrectal ultrasound (TRUS), computed tomography (CT), and magnetic resonance imaging (MRI) for preoperative stereometry of the prostate, and we further reviewed the utility of the MRI measurement. We performed prostate stereometry with TRUS, CT, and MRI in each of 45 patients who had provided informed consent. Taking TRUS stereometry as the standard, we computed the correlation of the MRI results with TRUS, and that of the CT results with TRUS, and found that MRI had a higher correlation.

The management of apparatus for diagnostic imaging is an important job for radiological technologists. In the last 10 years we have encountered 2227 malfunctions in 3652 days. We detected 163 cases at the initial check-up, which accounted for 7.3% of total cases. By performing an initial check-up, we detected one malfunction every 21 days and were able to keep the effects of mishaps to a minimum, prevent accidents, and obtain stable-quality images.

Fluoroscopy-guided intervention of the lumbar spine, such as nerve block, plays an important role in the management of disc hernia patients. However, irradiation of operators' fingers remains a problem even with careful collimation and operation, especially when performed by non-radiologists. We compared the irradiation doses of under-table and over-table fluoroscopy systems, and we discuss the most advantageous method of reducing irradiation. The effectiveness and conditions of use of lead protection gloves were also evaluated. Skin dose was monitored using polymethyl methacrylate (PMMA) and an electronic dose meter. The skin doses of over- and under-table fluoroscopy were compared using C-arm fluoroscopy. Finger irradiation dose with 0.03 mmPb protection gloves was also measured. The under-table method reduced skin dose by 95% compared with the over-table method. Thicker PMMA resulted in a higher rate of irradiation reduction. Protection gloves reduced radiation dose by half, although this reduction was cancelled when automatic brightness control (ABC) was utilized. Under-tube fluoroscopy was superior to over-tube fluoroscopy in reducing irradiation to the fingers.

The wide radiation field for mediastinal dose distribution should be inhomogeneous with the usual simple opposed beam irradiation. The purpose of this study was to improve the dose distribution of the mediastinum using a conventional planning system with a dose-volume histogram (DVH) and the field-in-field technique. Three-dimensional (3D) dose distribution is obtained in bilateral opposed-field irradiation. An overdose area obtained from the 3D dose distribution is defined and reprojected into the irradiation field. A new reduced field is created by removing the reprojected overdose area. A 3D dose distribution is again obtained and compared with the results from first one. Procedures were repeated until each of the target volumes was within +/-5% of the prescribed dose and the irradiation volume within 107% or less of the prescribed dose. From the DVH analysis, our field-within-a-field technique resulted in a more uniform dose distribution within the conventional planning. The field-within-a-field technique involves many parameters, and an inverse planning algorithm is suitable for computation. However, with our method, the forward planning system is adequate for planning, at least in a relatively straightforward planning system such as bilateral opposed fields therapy.

In the internal coil device Mini-RT, overdense plasmas have been observed, and heating by electron Bernstein waves (EBWs) is expected. EBWs, which have no cutoff density, are electrostatic-mode waves converted from the electromagnetic mode. To examine mode conversion in Mini-RT experiments, we are attempting to investigate the propagation of waves in the electron cyclotron range of frequencies (ECRF) in overdense plasmas. We injected diagnostic microwaves (typically 1 GHz) into a plasma produced by 2.45 GHz microwaves and directly measured their characteristics by inserting various probing antennas into the plasma with an interference system. Electromagnetic field measurements revealed a long-wavelength mode in the area with lower density than the upper hybrid resonance (UHR) region. In the area with higher density than that of the UHR region, waves having the characteristics of EBWs were observed; namely, short wavelength (∼20 mm), electrostatic mode, longitudinal polarization, and backward wave mode. These results suggest that EBWs were mode converted from electromagnetic waves at the UHR.