Objective Magnetic resonance simulator(MR Sim)is a novel type of simulation equipment utilized in radiotherapy.Acceptance testing is an essential quality assurance procedure prior to the clinical use of the MR Sim.The report provides the detailed procedures and result analysis of acceptance testing for an MR Sim.Methods The acceptance testing scheme was developed following the recently published AAPM TG284 report and the NCC/T-RT 002-2023 guidelines.Quality control equipments such as ACR(American College of Radiology)large phantom and geometric distortion measurement phantom were used for evaluating various aspects of the MR Sim,including the effectiveness of shielding,the functionality of imaging system,the image quality,the performance of radio frequency coils,the geometric accuracy of large field imaging,the precision of external laser markings,the couch movement accuracy,and the image transmission accuracy.Results The shielding effectiveness at a frequency of 150 MHz exhibited an average value of 105 dB.All of 8 image quality indices,namely geometric accuracy,slice position accuracy,slice thickness accuracy,image uniformity,artifact ratio,signal-to-noise ratio,high-contrast spatial resolution,and low-contrast resolution,fell within recommended tolerances.The maximum geometric distortion observed across a 25 cm field of view was less than 2 mm.The errors in external laser markings and couch movement accuracy were both less than 1 mm.The couch levelness was less than 1°.Both radio frequency coils and image transmission passed the required tests.Conclusion MR Sim is high-precision and complex.To ensure its precise application in radiotherapy,the acceptance testing for an MR Sim should be meticulously designed and executed following the established guidelines and accounting for its unique performance characteristics.

Prolonged total treatment time due to radiotherapy interruptions is detrimental to local tumor control.There are multiple causes that contribute to the occurrence of interruption events during radiotherapy,including public holidays,machine breakdown and maintenance,and radiotherapy complications.If treatment interruption events are unavoidable during radiotherapy,compensatory approaches should be taken to minimize the effects of radiotherapy interruptions on tumor control.Herein the study provides a summary on the causes and influence of radiotherapy interruptions,the ideas of interruption compensation,and the biological models of radiotherapy interruption compensation,such as nominal standard dose,cumulative radiation effect,time-dose fractionation factors,biologically effective dose models,etc.Additionally,the compensatory calculation for radiotherapy interruption in nasopharyngeal carcinoma is taken as an example to provide a reference for the quantitative compensation calculation for radiotherapy interruption in clinic.

Prolonged total treatment time due to radiotherapy interruptions is detrimental to local tumor control.There are multiple causes that contribute to the occurrence of interruption events during radiotherapy,including public holidays,machine breakdown and maintenance,and radiotherapy complications.If treatment interruption events are unavoidable during radiotherapy,compensatory approaches should be taken to minimize the effects of radiotherapy interruptions on tumor control.Herein the study provides a summary on the causes and influence of radiotherapy interruptions,the ideas of interruption compensation,and the biological models of radiotherapy interruption compensation,such as nominal standard dose,cumulative radiation effect,time-dose fractionation factors,biologically effective dose models,etc.Additionally,the compensatory calculation for radiotherapy interruption in nasopharyngeal carcinoma is taken as an example to provide a reference for the quantitative compensation calculation for radiotherapy interruption in clinic.