In this article, the authors propose an image registration program of portal images and digitally reconstructed radiography (DRR) images used as simulation images for external beam radiation therapy planning. First, the center of the radiation field in a portal image taken using a computed radiograhy cassette is matched to the center of the portal image. Then scale points projected on a DRR image and the portal image are deleted, and the portal image with the radiation field is extracted. Registration of the DRR and portal images is performed using mutual information as the registration criterion. It was found that the absolute displacement misregistrations in two directions (x, y) were 1.2±0.7 mm and 0.5±0.3 mm, respectively, and rotation disagreement about the z axis 0.3±0.3°. It was concluded the proposed method was applicable to image registration of portal and DRR images in radiation therapy.

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Polymer gel dosimetry has been considered a promising technique for clinical use, but this potential has not yet been fully realized in Japan. One reason may be because the commercialized gel detector, BANG^TM gel, is expensive and it is only produced abroad. A second reason is the difficulty of controlling dose sensitivity of the gel so that it is stable under ordinary clinical conditions. In this work we introduce two types of gel detectors (MAG and PAG) which we produced in-house. First the method of fabrication of gel is presented in detail, then the dose responses of MAG and PAG for X-ray irradiation are evaluating for MRI and X-ray CT scanning. The MAG-type gel is useful in low contrast dosimetry because of the high sensitivity in its dose response (R₂). The PAG-type gel is effective for dosimetry in multiple field irradiations because its dose response (CT value) has reproducibility independent of the different irradiation conditions. Finally, we summarize the potential for clinical use of polymer gel dosimetry with these gel detectors.

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Radiotherapy institutions carry out various types of treatments such as conventional radiation treatment, stereotactic radiotherapy (SRT), intensity-modulated radiation therapy (IMRT) and image-guided radiotherapy (IGRT). According to the radiation treatment type, various kinds of quality assurance (QA) equipment are used to maintain the accurate dose delivery to a patient with accurate positioning. The aim of this report was to propose the QA equipment required at various institutional levels. The institution levels were categorized according to the radiation treatment cases. Institutions in the basic category used conventional radiotherapy techniques employing field sizes larger than 4 cm×4 cm, or they had no full-time radiation oncologist. In addition to the basic level, five other categories were defined which were based on being able to carry out total body irradiation, three-dimensional conformal radiation therapy / SRT, IMRT, and IGRT. Minimum QA equipment requirements were proposed for each level. This proposal will facilitate the purchase of QA equipment for the installation or refurbishing of a linear accelerator.

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