A brachytherapy photon radiation quality index Q(BT) for probe-type dosimetry
2016 (English)In: Physica medica (Testo stampato), ISSN 1120-1797, E-ISSN 1724-191X, Vol. 32, no 6, 741-748 p.Article in journal (Refereed) PublishedText
Introduction: In photon brachytherapy (BT), experimental dosimetry is needed to verify treatment plans if planning algorithms neglect varying attenuation, absorption or scattering conditions. The detectors response is energy dependent, including the detector material to water dose ratio and the intrinsic mechanisms. The local mean photon energy E(r) must be known or another equivalent energy quality parameter used. We propose the brachytherapy photon radiation quality index Q(BT) ((E) over bar), to characterize the photon radiation quality in view of measurements of distributions of the absorbed dose to water, D-w, around BT sources. Materials and methods: While the external photon beam radiotherapy (EBRT) radiation quality index Q(EBRT) ((E) over bar) = TPR1020((E) over bar) is not applicable to BT, the authors have applied a novel energy dependent parameter, called brachytherapy photon radiation quality index, defined as Q(BT) ((E) over bar) = D-prim(r = 2 cm; theta(0) = 90 degrees)/D-prim(r(0) = 1 cm; theta(0) = 90 degrees), utilizing precise primary absorbed dose data, D-prim, from source reference databases, without additional MC-calculations. Results and discussion: For BT photon sources used clinically, Q(BT) ((E) over bar) enables to determine the effective mean linear attenuation coefficient (mu) over bar (E) and thus the effective energy of the primary photons E-prim(eff)(r(0), theta(0)) at the TG-43 reference position P-ref (r(0) = 1 cm; theta(0) = 90 degrees) being close to the mean total photon energy (E) over bar (tot)(r(0), theta(0)). If one has calibrated detectors, published (E) over bar (tot)(r) and the BT radiation quality correction factor k(Q, Q0)(BT) ((E) over bar, r, theta) for different BT radiation qualities Q and Q(0), the detectors response can be determined and D-w(r, theta) measured in the vicinity of BT photon sources. Conclusions: This novel brachytherapy photon radiation quality index Q(BT) characterizes sufficiently accurate and precise the primary photon` s penetration probability and scattering potential. (C) 2016 Published by Elsevier Ltd on behalf of Associazione Italiana di Fisica Medica.
Place, publisher, year, edition, pages
ELSEVIER SCI LTD , 2016. Vol. 32, no 6, 741-748 p.
Photon brachytherapy radiation quality index; Absorbed dose to water; Detector response; Effective energy
Radiology, Nuclear Medicine and Medical Imaging
IdentifiersURN: urn:nbn:se:liu:diva-130072DOI: 10.1016/j.ejmp.2016.03.008ISI: 000377373600001PubMedID: 27237583OAI: oai:DiVA.org:liu-130072DiVA: diva2:946977