ABSTRACT
Dosimeters play an important part in radiotherapy. They help establish and monitor linear accelerator (LINAC) performance by measuring calibration factors, profiles, and percent depth curves, which provide information for beam modeling used for treatment planning. Some dosimeters verify and commission brachytherapy sources by measuring air kerma strength and https://www.w3.org/1998/Math/MathML"> 2 D / 3 D https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315372655/b2ce6ef4-5376-4be5-9af3-87940a039f56/content/eq2291.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> dose distribution. And some dosimeters can be used for in vivo measurements (Mijnheer 2013, Tanderup 2013), either as part of standard patient quality assurance (QA) for certain procedures (such as total body irradiation) or to measure absorbed dose in a newly implemented technique. Despite a wide availability of dosimeters and dosimetry systems that can be utilized for in vivo measurements, there is still a lack of a commercially available system that can be used in all in vivo scenarios and across all radiotherapeutic energies in external beam radiation therapy (EBRT) and brachytherapy without performing energy-specific calibration. While 2D/3D dosimetry using an electronic portal imaging device (EPID) is a promising candidate for use in external beam radiotherapy, it cannot be practically implemented for brachytherapy procedures, especially those using low-energy sources. This means that in vivo dose verification in brachytherapy is largely limited to point-based (or array) dosimetry, provided that the location of dosimeter can be accurately known and tied back to the planned dose. To help diagnose sources of error, dose or dose-rate information as a function of treatment time is of great use, instead of a single measurement of total absorbed dose. Real-time data can provide information per individual intensity modulated radiation therapy (IMRT) segment, or volumetric modulated arc therapy arc, or a particular source dwell position. In addition, real-time dosimetry allows for quick intervention and interruption of treatment in case a gross error has been detected. This is of particular use in brachytherapy, where higher doses and fewer fractions are used compared to standard external beam fractionation.
