The results demonstrate how important it is for the appropriate corrections to be applied to give consistent and accurate measurements for a range of detectors in small beam geometry. The results further demonstrate that depending on the choice of detectors, there is a potential for large errors when effects such as volume averaging, perturbation and differences in material properties of detectors are not taken into account. As the commissioning of small fields for clinical treatment has to rely on accurate dose measurements, the authors recommend the use of detectors that require relatively little correction, such as unshielded diodes, diamond detectors or microchambers, and solid state detectors such as alanine, TLD, Al2O3:C, or scintillators.

A prototype of a new dose-verification system has been developed to facilitate prevention and identification of dose delivery errors in remotely afterloaded brachytherapy. The system allows for automatic online in vivo dosimetry directly in the tumor region using small passive detector probes that fit into applicators such as standard needles or catheters. The system measures the absorbed dose rate ͑0.1 s time resolution͒ and total absorbed dose on the basis of radioluminescence ͑RL͒ and optically stimulated luminescence ͑OSL͒ from aluminum oxide crystals attached to optical fiber cables ͑1 mm outer diameter͒. The system was tested in the range from 0 to 4 Gy using a solidwater phantom, a Varian GammaMed Plus 192 Ir PDR afterloader, and dosimetry probes inserted into stainless-steel brachytherapy needles. The calibrated system was found to be linear in the tested dose range. The reproducibility ͑one standard deviation͒ for RL and OSL measurements was 1.3%. The measured depth-dose profiles agreed well with the theoretical expectations computed with the EGSNRC Monte Carlo code, suggesting that the energy dependence for the dosimeter probes ͑relative to water͒ is less than 6% for source-to-probe distances in the range of 2-50 mm. Under certain conditions, the RL signal could be greatly disturbed by the so-called stem signal ͑i.e., unwanted light generated in the fiber cable upon irradiation͒. The OSL signal is not subject to this source of error. The tested system appears to be adequate for in vivo brachytherapy dosimetry.

No abstract

(2009) Medical reference dosimetry using EPR measurements of alanine: Development of an improved method for clinical dose levels., Acta Oncologica, 48:2, 216-222,

No abstract