Patient setup verification procedure for a portal image in a computed radiography system with a high-resolution liquid-crystal display monitor.

In our conventional visual inspection for setup verification, we have routinely used a console monitor of a CR system and a monitor of a treatment-planning system (i.e., the separate-monitor method) in order to avoid the need for CR portal-film generation. However, the separate-monitor method provided insufficient precision in detecting setup errors. We devised a setup verification procedure that uses a high-resolution liquid-crystal display monitor (i.e., the single-monitor method). Our objective in the present study was to evaluate the precision of the single-monitor method. These two methods were compared in terms of the precision of visual inspection. The single-monitor method was significantly superior to the separate-monitor method in sensitivity and in the magnitude of the discrepancy that could not be detected. The single-monitor method provides higher precision in visual inspection than does the separate-monitor method, and is a useful verification procedure.

Monitoring of respiratory movement of the diaphragm for gated radiotherapy.

PURPOSE: In order to obtain a respiratory signal for gated radiotherapy, diaphragm movement was monitored. MATERIALS AND METHODS: To obtain the diaphragm signal, an image brightness stabilizer for fluoroscopy of an X-ray simulator was used. The image brightness stabilizer output electric current in response to image brightness, which changed with diaphragm movement. The electric current was recorded as the diaphragm signal and compared with the abdominal wall signal, which was obtained by monitoring the height of the abdominal wall using a laser displacement sensor. RESULTS: A regular diaphragm signal was obtained in all of nine patients. At 70% expiration of the abdominal wall signal, the diaphragm signal ranged from 35% to 70% expiration (median, 55%). At 30% inspiration of the abdominal wall signal, the diaphragm signal ranged from 10% to 30% inspiration (median, 20%). CONCLUSION: A regular diaphragm signal could be conveniently obtained utilizing an image brightness stabilizer. The diaphragm signal tended to be delayed in comparison with the abdominal wall signal.

Verification imaging using a computed radiography system for high-energy electron beam therapy.

PURPOSE: The aim of this study was to examine a method to more conveniently acquire verification images. A computed radiography (CR) system was employed using a photostimulable phosphor plate and diagnostic cassette used for taking diagnostic X-ray photographs. MATERIALS AND METHODS: Verification images were acquired using the diagnostic cassette and therapy cassette. Image processing parameters were adjusted to improve the image quality. Verification images were printed using optimum parameters, and 10 radiation technicians visually evaluated the images. The sign test was used, and image quality was evaluated using a two-sided test at a 5% level of significance. To assess its clinical value, a radiation oncologist evaluated patient verification images. RESULTS: Verification image quality was improved by the adjustment of image processing parameters. As a result of the image quality evaluation, there were no significant differences between the two types of cassette (p>0.05). In most of the clinical cases (98%), the verification images were useful. CONCLUSION: We found that good quality verification images were acquired by a CR system with a diagnostic cassette. This system is suitable for practical use to acquire daily verification images, and it is considered useful for maintaining quality assurance (QA) in high-energy electron beam therapy.