A new Chinese standard for testing of quality control in medical proton/heavy ion beam radiotherapy equipment

With the development of social economy and radiotherapy technique,proton/heavy ion radiotherapy has been applied widely to clinical practices.At present,there are at least 29 hospitals in China at various stages of planning,construction,commissioning or clinical operation of medical proton/heavy ion beam radiotherapy equipment.Compared with common radiotherapy accelerators used in conventional external beam radiotherapy,the proton/heavy ion therapy system has more stringent requirements for quality control so as to achieve an optimum therapeutic effect.In order to protect the health rights of patients undergoing radiotherapy,to facilitate the relevant administrative supervision departments to carry out standard-based approval and routine supervision and to promote the development of related medical undertakings,the standard for testing of quality control for medical proton/heavy ion beam radiotherapy equipment is drafted to fill the gap in this regard in China and even worldwide.The standard contains five indicators and corresponding testing methods for radiological protection and safety and 16 indicators for quality control of equipment performance.The standard is a mandatory standard and is based on the relevant Chinese legal requirements for the testing of radiotherapy equipment,so all the indicators listed in the standard shall be tested.During the drafting of the standard,the opinions from hospitals that are currently using proton/heavy ion medical accelerators for radiotherapy purpose and from the related equipment manufacturers were taken into account.The draft standard was revised with reference to these opinions and the feasibility of the related quality control requirements.The official version of the standard was released on March 7,2023,and implementation is scheduled to begin on March 1,2024.

In-vivo proton range verification for reducing the risk of permanent alopecia in medulloblastoma treatment

Objective:The purpose of this work is the clinical commissioning of a recently developed in-vivo range verification system for the head treatment of pediatric medulloblastoma patients.Inaccurate beam range for such treatment could lead to either inadequate dose coverage of the target volume or excessive dose to the head skin resulting permanent alopecia.Methods:The in-vivo range verification system is designed to perform pre-treatment range verification and adjustment.An array of Si-diode detectors is to be placed on the patient immobilization mask in the exit direction of a whole-brain field;signal is analyzed,and the extracted water equivalent path length(WEPL)is compared to the expected one,revealing if a range correction is needed.The method was tested in solid water and anthropomorphic head phantom,with validation based on independent WEPL measurements.The measured WEPL were compared to those computed by the treatment planning system(TPS).Results:The accuracy for the WEPL measurements by the diode system in both solid water and anthropomorphic head phantom were on average within a millimeter from more accurate measurement by the dose-extinction technique,with the error range for the two phantoms as(0–1 mm)and(0–1.3 mm),respectively.When compared to the WEPL calculated by the treatment planning system,the measured values were on average within 1%(range 0–3%)of the beam range.The accuracy of dose measurements by the diodes in the fall-off part of the depth dose profile was validated against the reference Markus chamber.No need for further correction(due to different beam parameters and detector dose ageing effects)was found.Conclusions:The range verification workflow was successfully tested in the anthropomorphic head phantom.The performance of the in-vivo range verification system and related workflow meet the clinical requirements in terms of the needed WEPL accuracy for pretreatment range verification.