Honors College Thesis

Volumetric-modulated arc radiotherapy for pancreatic malignancies : Dosimetric comparison with helical TomoTherapy

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  • Purpose: To compare target dose conformality and OAR sparing afforded by VMAT and HT for pancreatic cancer. Materials and Methods: A retrospective planning study was performed in 18 patients. Total treatment dose was 59.4Gy. OAR and PTV mean doses, conformity indices, isodose volumes, and integral doses were compared. The relationship between tumor volume, patient circumference, and these variables was also evaluated. Results: Mean doses to the left kidney (p<.001), right kidney (p<.001), and liver (p<.001) were smaller with VMAT. The mean dose to the PTV was smaller with HT (p=.002). The large field VMAT resulted in a smaller CI percent deviation from 1.0 (p=.025). There was no significant difference for the boost plan (p=.092). Integral dose was significantly lower with VMAT (p<.001). Integral dose was lower for smaller tumor volumes and patent circumferences with both techniques. Conclusion: There appears to be an advantage in using VMAT over HT in reducing radiation doses to the liver and kidneys, in obtaining tighter isodose volumes, and in obtaining a lower integral dose. VMAT may provide superior conformity indices for larger doses, but the techniques are comparable for low doses. Smaller tumor volume and patient circumference result in lower integral doses with both techniques.
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