Details

Autor(en) / Beteiligte

• Titt, Uwe
• Mirkovic, Dragan
• Sawakuchi, Gabriel O
• Perles, Luis A
• Newhauser, Wayne D
• Taddei, Phillip J
• Mohan, Radhe

Titel

Adjustment of the lateral and longitudinal size of scanned proton beam spots using a pre-absorber to optimize penumbrae and delivery efficiency

Ist Teil von

• Physics in medicine & biology, 2010-12, Vol.55 (23), p.7097-7106

Ort / Verlag

England: IOP Publishing

Erscheinungsjahr

2010

Quelle

MEDLINE

Beschreibungen/Notizen

• In scanned-beam proton therapy, the beam spot properties, such as the lateral and longitudinal size and the minimum achievable range, are influenced by beam optics, scattering media and drift spaces in the treatment unit. Currently available spot scanning systems offer few options for adjusting these properties. We investigated a method for adjusting the lateral and longitudinal spot size that utilizes downstream plastic pre-absorbers located near a water phantom. The spot size adjustment was characterized using Monte Carlo simulations of a modified commercial scanned-beam treatment head. Our results revealed that the pre-absorbers can be used to reduce the lateral full width at half maximum (FWHM) of dose spots in water by up to 14 mm, and to increase the longitudinal extent from about 1 mm to 5 mm at residual ranges of 4 cm and less. A large factor in manipulating the lateral spot sizes is the drift space between the pre-absorber and the water phantom. Increasing the drift space from 0 cm to 15 cm leads to an increase in the lateral FWHM from 2.15 cm to 2.87 cm, at a water-equivalent depth of 1 cm. These findings suggest that this spot adjustment method may improve the quality of spot-scanned proton treatments.