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Comparison of Dose Deformable Accumulation by Using Parallel and Serial Approaches


Z Gao

Z Gao*, M Li , J Wong , Morristown Medical Center, Morristown, NJ

Presentations

MO-C-17A-10 Monday 10:15AM - 12:15PM Room: 17A

Purpose:The uncertainty of dose accumulation over multiple CT datasets with deformable fusion may have significant impact on clinical decisions. In this study, we investigate the difference of two dose summation approaches involving deformable fusion.

Methods:Five patients, four external beam and one brachytherapy(BT), were chosen for the study. The BT patient was treated with CT-based HDR. The CT image sets acquired in the image-guidance process (8-11 CTs/patient) were used to determine the dose delivered to the four external beam patients. (prostate, pelvis, lung and head&neck). For the HDR patient (cervix), five CT image sets and the corresponding BT plans were used. In total 44 CT datasets and RT dose/plans were imported into the image fusion software MiM (6.0.4) for analysis.
For each of the five clinical cases, the dose from each fraction was accumulated into the primary CT dataset by using both Parallel and Serial approaches. The dose-volume histogram (DVH) for CTV and selected organs-at-risks (OAR) were generated. The D95(CTV), OAR(mean) and OAR(max) for the four external beam cases the D90(CTV), and the max dose to bladder and rectum for the BT case were compared.

Results:For the four external beam patients, the difference in D95(CTV) were <1.2% PD between the parallel and the serial approaches. The differences of the OAR(mean) and the OAR(max ) range from 0 to 3.7% and <1% PD respectively. For the HDR patient, the dose difference for D90 is 11% PD while that of the max dose to bladder and rectum were 11.5% and 23.3% respectively.

Conclusion:For external beam treatments, the parallel and serial approaches have <5% difference probably because tumor volume and OAR have less changes from fraction to fraction. For the brachytherapy case, >10% dose difference between the two approaches was observed as significant volume changes of tumor and OAR were observed among treatment fractions.


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