Proton therapy dose distribution comparison between Monte Carlo and a treatment planning system for pediatric patients with ependymoma
- St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, Tennessee 38120 (United States)
Purpose: Compare dose distributions for pediatric patients with ependymoma calculated using a Monte Carlo (MC) system and a clinical treatment planning system (TPS). Methods: Plans from ten pediatric patients with ependymoma treated using double scatter proton therapy were exported from the TPS and calculated in our MC system. A field by field comparison of the distal edge (80% and 20%), distal fall off (80% to 20%), field width (50% to 50%), and penumbra (80% to 20%) were examined. In addition, the target dose for the full plan was compared. Results: For the 32 fields from the 10 patients, the average differences of distal edge at 80% and 20% on central axis between MC and TPS are -1.9 {+-} 1.7 mm (p < 0.001) and -0.6 {+-} 2.3 mm (p= 0.13), respectively. Excluding the fields that ranged out in bone or an air cavity, the 80% difference was -0.9 {+-} 1.7 mm (p= 0.09). The negative value indicates that MC was on average shallower than TPS. The average difference of the 63 field widths of the 10 patients is -0.7 {+-} 1.0 mm (p < 0.001), negative indicating on average the MC had a smaller field width. On average, the difference in the penumbra was 2.3 {+-} 2.1 mm (p < 0.001). The average of the mean clinical target volume dose differences is -1.8% (p= 0.001), negative indicating a lower dose for MC. Conclusions: Overall, the MC system and TPS gave similar results for field width, the 20% distal edge, and the target coverage. For the 80% distal edge and lateral penumbra, there was slight disagreement; however, the difference was less than 2 mm and occurred primarily in highly heterogeneous areas. These differences highlight that the TPS dose calculation cannot be automatically regarded as correct.
- OSTI ID:
- 22098940
- Journal Information:
- Medical Physics, Vol. 39, Issue 8; Other Information: (c) 2012 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-2405
- Country of Publication:
- United States
- Language:
- English
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