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Dosimetry for ion beam radiotherapy.

Karger, C P*; Häkel, O*; Palmans, H; Kanai, T* (2010) Dosimetry for ion beam radiotherapy. Phys. Med. Biol., 55 (21). R193-R234

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Recently, ion beam radiotherapy (including protons as well as heavier ions) gained considerable interest. Although ion beam radiotherapy requires dose prescription in terms of iso-effective dose (referring to an iso-effective photon dose), absorbed dose is still required as an operative quantity to control beam delivery, to characterize the beam dosimetrically, and to verify dose delivery. This article reviews current methods and standards to determine absorbed dose to water in ion beam radiotherapy including i) the detectors used to measure absorbed dose, ii) dosimetry under reference conditions, and iii) dosimetry under non-reference conditions. Due to the LET-dependence of the response of films and solid state detectors, dosimetric measurements are mostly based on ion chambers. While a primary standard for ion beam radiotherapy still remains to be established, ion chamber dosimetry under reference conditions is based on similar protocols as for photons and electrons although the involved uncertainty is larger than for photon beams. For non-reference conditions, dose measurements in tissue-equivalent materials may also be necessary. Regarding the atomic numbers of the composites of tissue-equivalent phantoms, special requirements have to be fulfilled for ion beams. Methods for calibrating the beam monitor depend on whether passive or active beam delivery techniques are used. QA measurements are comparable to conventional radiotherapy, however dose verification is usually single-field- rather than treatment-plan-based. Dose verification for active beam delivery techniques requires the use of multi-channel dosimetry systems to check the compliance of measured and calculated dose for a representative sample of measurement points. Although methods for ion beam dosimetry have been established, there is still room for developments. This includes the improvement of the dosimetric accuracy as well as the development of more efficient measurement techniques.

Item Type: Article
Keywords: Radiotherapy, dosimetry review, protons, heavy ions, charged particles
Subjects: Ionising Radiation
Ionising Radiation > Dosimetry
Last Modified: 02 Feb 2018 13:15
URI: http://eprintspublications.npl.co.uk/id/eprint/4778

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