When panoramic radiography is not sufficient in the study of the teeth and jaw bones, CBCT can provide identical information to MSCT, with a considerable dose reduction. MSCT is, however, indicated when evaluation of soft tissue is required.

The dose distribution produced by the high-dose-rate (HDR) 192Ir source is inherently anisotropic due to self-absorption by the high-density source core, oblique filtration by the source capsule and the asymmetric geometry of the source capsule. To account for the dose distribution anisotropy of brachytherapy sources, AAPM Task Group No 43 has included a two-dimensional anisotropy function, F(r, theta), in the recommended dose calculation formalism. Gafchromic HS radiochromic film (RCF) was used to measure anisotropy function for microSelectron HDR 192Ir source (classic/old design). Measurements were carried out in a water phantom using specially fabricated PMMA cylinders at radial distances 1, 2, 3, 4 and 5 cm. The data so generated are comparable to both experimental and Monte Carlo calculated values for this source reported earlier by other authors. The RCF method described in this paper is comparatively high resolution, simple to use and is a general method, which can be applied for other brachytherapy sources as well.

In this study, two different techniques used for image-guided percutaneous transthoracic needle biopsy have been compared in terms of patient dose: computed tomography (CT) fluoroscopy (performed on a Toshiba Aquilion 64), supplied with several multidetector CT (MDCT), and cone-beam CT (CBCT) (performed on a Philips Allura Xper FD20), supplied with a few C-arm flat-panel angiographic devices. Dose data (10 patients for each technique) have been collected, and organ doses and effective dose have been evaluated using software packages enabling to simulate real acquisition geometry and X-ray exposure. As a result, higher doses were found for MDCT compared with CBCT: the effective dose is 50% higher for MDCT; ratios between mean organ doses range between 1.2 and 1.7, except for breast (0.9) and oesophagus (3.7). Even though the observed differences are not always statistically significant, the general distribution of organ doses confirms that the MDCT-guiding technique delivers higher dose than the CBCT-guided one.

The efficacy of a treatment may vary as a result of several factors. Customised radiobiological evaluation is a useful adjunct to clinical evaluation in planning equivalent treatments that satisfy all dosimetric constraints.

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