Dosimetric effects of cardiac-respiratory motion on cardiac stereotactic body radiotherapy
Objective To investigate the dosimetric effects of complex cardiac-respiratory motion in cardiac stereotactic body radiotherapy(CSBRT).Methods A cardiac motion phantom was employed to simulate patient-specific cardiac-respiratory motion in 10 cases.The measured doses obtained under the phantom motion state were compared with the calculated doses in radiotherapy treatment planning for clinical patients.Moreover,18 groups of design-based cardiac-respiratory motion were simulated.The radiation doses under the phantom motion state were measured using radiochromic films and compared with those under the resting state.Results In the patient-specific cardiac-respiratory motion group,the gamma passing rate(GPR)under the 3％/2 mm standard between the measured and the calculated doses was 90.0％±7.0％.The correlation coefficient of the respiratory motion amplitude in the superior-inferior(SI)dimension with the GPR was-0.86(P=0.01).In the design-based cardiac-respiratory motion groups,the increase in the amplitude of cardiac-respiratory motion reduced the consistency between the dynamic dose and the static reference dose.Especially,the increase in the respiratory motion amplitude produced the most pronounced effect,reducing the width of the 90％isodose line in the respiratory motion direction,with a mean slope of-1.6.Additionally,the increase in the penumbra corresponds to a mean slope of 1.4.Conclusions The respiratory motion amplitude serves as a primary factor influencing the dose accuracy of CBSRT.The characteristics and dosimetric effects of cardiac-respiratory motion are patient-specific,thus necessitating the assessment of cardiac-respiratory motion characteristics before CBSRT to individualize the application of motion management techniques for enhanced treatment accuracy.
Cardiac stereotactic body radiotherapyCardiac-respiratory motionMotion phantomGamma passing rate
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