A quantitative investigation at dose to tissue when using physical constraints versus biological based constraints in pancreatic carcinoma patients

Introduction The purpose of this study was to compare dose to organs at risk as well as PTV coverage. Physical objectives, biological objectives, and a combination of the two were utilized to compare which technique provided the best coverage of the PTV while also preserving the greatest amount of healthy tissue. Methods Each randomly selected patient had three separate plans created for them. The first plan used only physical based constraints in the form of upper objectives. The second plan used only biological based constraints in the form of gEUD objectives. The third plan used a combination of both upper and gEUD based objectives. Results Results indicate there was a difference to plan quality when using both uppers and gEUD based objectives. In regard to organs at risk, a physical upper constraint of 0% of the organ volume receiving a maximum dose, as well as a gEUD constraint with an alpha value of 1 provided the most optimal plans. A low priority value on the gEUD (60-70) in conjunction with the upper value provided a gentle, yet effective way to control dose to nearby organs at risk without resulting in suboptimal dose to planning target volume. Conclusion A combination of upper values and gEUD objectives provided lowest dose to organs at risk while maintaining a desired dose to PTV coverage. For further success, it was recommended that the organs at risk be cropped out of the PTV in order do provide the lowest dose as reasonably achievable in that organ, while not influencing coverage of the PTV itself