Analysis of DVH variations based on interquartile range among IMRT plans / 中华放射医学与防护杂志

ABSTRACT

Objective To study the dose volume histogram ( DVH ) difference of target and organs at risk in intensity-modulated radiation therapy ( IMRT ) planning of cervical cancer based on the interquartile range. Methods A total of 22 cervical cancer patients′ IMRT plans were retrospectively analyzed. Five groups of DVH curves of PTV and OARs ( bladder, rectum, left and right femoral heads) were derived from the Pinnacle3 planning system. The mean DVH curves and interquartile range of volume ( IQRvol ) as a function of dose were calculated from each group′s DVH curve. Results The maximum volume variation for PTV reached at IQRvol(54. 03 Gy) =6. 95%, the volume of the target reached by the prescription dose was ( 96. 43 ± 1. 63 )%. The maximum volume variation for bladder reached at IQRvol (17. 24 Gy) = 14. 62%. V40 and V30 for bladder were ( 32. 79 ± 7. 06 )% and ( 56. 47 ± 9. 94 )%, respectively. Rectal DVH showed the largest difference at 35. 92 Gy, with the quartile of 19. 94%, the V40 and V30 for rectum were (30. 17 ± 10. 80)% and (58. 16 ± 11. 99)%, respectively. The difference in the bladder and the rectum was statistically significant (z = -6. 59, P < 0. 05). The maximum volume variation of left femoral head reached at IQRvol(16. 06 Gy) =31. 47%. The maximum volume variation of right femoral head was reached at IQRvol (17. 47 Gy) =32. 82%. There was no significant difference in IQRvol between right and left femoral head (P>0. 05). Conclusions Quartile range curve of DVHs can be used to analyze the deviations of DVH curves of PTV and OARs, and provide guidance for automatic planning optimization parameter setting.