Comparing proton treatment plans of pediatric brain tumors in two pencil beam scanning nozzles with different spot sizes.

Comparing proton treatment plans of pediatric brain tumors in two pencil beam scanning nozzles with different spot sizes. J Appl Clin Med Phys. 2015;16(6):5389 Authors: Kralik JC, Xi L, Solberg TD, Simone Ii CB, Lin L Abstract Target coverage and organ-at-risk sparing were compared for 22 pediatric patients with primary brain tumors treated using two distinct nozzles in pencil beam scanning (PBS) proton therapy. Consecutive patients treated at our institution using a PBS-dedicated nozzle (DN) were replanned using a universal nozzle (UN) beam model and the original DN plan objectives. Various cranial sites were treated among the patients to prescription doses ranging from 45 to 54 Gy. Organs at risk (OARs) evaluated were patient-dependent; 15 unique OARs were analyzed, all of which were assessed in at least 10 patients. Clinical target volume (CTV) coverage and organ sparing were compared for the two nozzles using dose-volume histogram data. Statistical analysis using a confidence-interval approach demonstrates that CTV coverage is equivalent for UN and DN plans within ± 5% equivalence bounds. In contrast, average mean and maximum doses are significantly higher for nearly all 15 OARs in the UN plans. The average median increase over all OARs and patients is approximately 1.7 Gy, with an increase in the 25%-75% of 1.0-2.3 Gy; the median increase to the pituitary gland, temporal lobes, eyes and cochleas are 1.8, 1.7, 0.7, and 2.7 Gy, r...
Source: Journal of Applied Clinical Medical Physics - Category: Physics Authors: Tags: J Appl Clin Med Phys Source Type: research