Toward improved target conformity for two spot scanning proton therapy delivery systems using dynamic collimation.

Purpose: To quantify improvement in target conformity in brain and head and neck tumor treatments resulting from the use of a dynamic collimation system (DCS) with two spot scanning proton therapy delivery systems (universal nozzle, UN, and dedicated nozzle, DN) with median spot sizes of 5.2 and 3.2 mm over a range of energies from 100 to 230 MeV.

Pencil-beam scanning proton therapy for anal cancer: a dosimetric comparison with intensity-modulated radiotherapy.

Background: Concurrent chemoradiotherapy cures most patients with anal squamous cell carcinoma at the cost of significant treatment-related toxicities. Intensity-modulated radiotherapy (IMRT) reduces side effects compared to older techniques, but whether proton beam therapy (PBT) offers additional advantages is unclear.

Material And Methods: Eight patients treated with PBT for anal cancer were chosen for this study.

Comparison of prostate proton treatment planning technique, interfraction robustness, and analysis of single-field treatment feasibility.

Background: This study compares target coverage robustness among proton therapy plans for prostate cancer patients treated with 2 laterally opposed fields delivered daily or, alternatively, every other day as single lateral fields, using uniform scanning (US), single-field uniform dose (SFUD), pencil beam scanning (PBS) optimized for uniform target coverage only, SFUD PBS optimized for target coverage and organs at risk (OAR) sparing (SFUD-opt), and intensity modulated proton therapy (IMPT).

Methods And Materials: Ten prostate cancer patients treated with proton therapy underwent weekly verification computed tomographic (CT) scans. US, SFUD, SFUD-opt, and IMPT treatment plans were created and recalculated on weekly verification scans evaluating 2-field daily and single-field target coverage and OAR constraints.

Comparison of secondary neutron dose in proton therapy resulting from the use of a tungsten alloy MLC or a brass collimator system.

Purpose: To apply the dual ionization chamber method for mixed radiation fields to an accurate comparison of the secondary neutron dose arising from the use of a tungsten alloy multileaf collimator (MLC) as opposed to a brass collimator system for defining the shape of a therapeutic proton field.

Methods: Hydrogenous and nonhydrogenous ionization chambers were constructed with large volumes to enable measurements of absorbed doses below 10(-4) Gy in mixed radiation fields using the dual ionization chamber method for mixed-field dosimetry. Neutron dose measurements were made with a nominal 230 MeV proton beam incident on a closed tungsten alloy MLC and a solid brass block.