Grid/lattice therapy: Consideration of small field dosimetry

Br J Radiol. 2024 Mar 29:tqae060. doi: 10.1093/bjr/tqae060. Online ahead of print.ABSTRACTSmall-field dosimetry used in special procedures such as gamma knife, Cyberknife, Tomotherapy, IMRT and VMAT has been in evolution after several radiation incidences with very significant (70%) errors due to poor understanding of the dosimetry. IAEA-TRS-483 and AAPM-TG-155 have provided comprehensive information on small-fields dosimetry in terms of code of practice and relative dosimetry. Data for various detectors and conditions have been elaborated. It turns out that with a suitable detectors dose measurement accuracy can be reasonably (±3%) achieved for 6 MV beams for fields > 1x1 cm2. For grid therapy, even though the treatment is performed with small fields created by either customized blocks, multileaf collimator (MLC) or specialized devices, it is multiple small fields that creates combined treatment. Hence understanding the dosimetry in collection of holes of small field is a separate challenge that needs to be addressed. It is more critical to understand the scattering conditions from multiple holes that form the treatment grid fields. Scattering changes the beam energy (softer) and hence dosimetry protocol needs to be properly examined for having suitable dosimetric parameters. In lieu of beam parameter unavailability in physical grid devices, MLC based forward and inverse planning is an alternative path for bulky tumors. Selection of detectors in small field measurement i...
Source: The British Journal of Radiology - Category: Radiology Authors: Source Type: research