Résumé
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.
Résumé
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.