In vivo dosimetry in external beam photon radiotherapy: Requirements and future directions for research, development, and clinical practice

Abstract

External beam radiotherapy with photon beams is a highly accurate treatment modality, but requires extensive quality assurance programs to confirm that radiation therapy will be or was administered appropriately. In vivo dosimetry (IVD) is an essential element of modern radiation therapy because it provides the ability to catch treatment delivery errors, assist in treatment adaptation, and record the actual dose delivered to the patient. However, for various reasons, its clinical implementation has been slow and limited. The purpose of this report is to stimulate the wider use of IVD for external beam radiotherapy, and in particular of systems using electronic portal imaging devices (EPIDs). After documenting the current IVD methods, this report provides detailed software, hardware and system requirements for in vivo EPID dosimetry systems in order to help in bridging the current vendor-user gap. The report also outlines directions for further development and research. In vivo EPID dosimetry vendors, in collaboration with users across multiple institutions, are requested to improve the understanding and reduce the uncertainties of the system and to help in the determination of optimal action limits for error detection. Finally, the report recommends that automation of all aspects of IVD is needed to help facilitate clinical adoption, including automation of image acquisition, analysis, result interpretation, and reporting/documentation. With the guidance of this report, it is hoped that widespread clinical use of IVD will be significantly accelerated.

Future directions of in vivo dosimetry for external beam radiotherapy and brachytherapy

“…The EBRT and High Dose Rate (HDR) BT reports [7] , [8] followed a unified IVD approach. Much attention was given to electronic portal imaging detector (EPID) panels for EBRT and on time resolved dosimetry for brachytherapy.…”

“…More details on which methods are included and excluded from this definition and further specific refinements for IVD for EBRT and BT are given in the two reports [7] , [8] . These also state which developments are needed to turn some methods into true IVD.…”

“…After the first ESTRO Physics Workshop, held in Glasgow in November 2017, it was decided to start a Task Group on IVD, with the aim of providing reports on the use of IVD for both EBRT and BT. This editorial gives an overview of the requirements identified by the Task Group, while more details for the individual modalities can be found in the respective reports published in this and the previous volume [7] , [8] .…”

The Effects of Ionising and Non-Ionising Electromagnetic Radiation on Extracellular Matrix Proteins

“…In contrast, energetic, ionising electromagnetic radiation (X-rays and gamma rays) can remove electrons. The undoubted importance of controlled exposure to ionising EM radiation in medical diagnostic imaging [ 4 ] and radiotherapy [ 5 , 6 ] must be balanced against side effects such as secondary cancers or tissue fibrosis [ 7 , 8 ]. Other forms of radiation, which rely on charged particles (e.g., α, β, protons), can also interact with biological systems and are clinically important (such as in proton therapy and in cosmic radiation exposure for space exploration), but being non-electromagnetic, they lie outside the scope of this review.…”

A Validation Method for EPID In Vivo Dosimetry Algorithms

“…The methodologies shown in this work are the final step of the commissioning of an EPID transit dosimetry system and can be used to validate any back-projection EPID algorithm [6,14] before clinical implementation.…”