Influence of random setup error on dose distribution / 中华放射肿瘤学杂志

ABSTRACT

Objective To investigate the influence of random setup error on dose distribution in radiotherapy and determine the margin from ITV to PTV. Methods A random sample approach was used to simulate the fields position in target coordinate system. Cumulative effect of random setup error was the sum of dose distributions of all individual treatment fractions. Study of 100 cumulative effects might get shift sizes of 90%dose point position. Margins from ITV to PTV caused by random setup error were choosen by 95% probability. Spearman's correlation was used to analyze the influence of each factor. Results The average shift sizes of 90%dose point position was 0.62,1.84,3.13,4.78,6.34 and 8.03 mm if random setup error was 1,2,3,4,5 and 6 mm,respectively. Univariate analysis showed the size of margin was associated only by the size of random setup elror. Conclusions Margin of ITV to PTV is 1.2 times random setup error for head-and-neck cancer and 1.5 times for thoracic and abdominal cancer. Field size, energy and target depth. unlike random setup error, have no relation with the size of the margin.