Purpose:In the absence of a collimation system the lateral penumbra of spot scanning (SS) dose distributions delivered by low energy proton beams is highly dependent on the spot size. For current commercial equipment, spot size increases with decreasing proton energy thereby reducing the benefit of the SS technique. This paper presents a dynamic collimation system (DCS) for sharpening the lateral penumbra of proton therapy dose distributions delivered by SS. Methods: The collimation system presented here exploits the property that a proton pencil beam used for SS requires collimation only when it is near the target edge, enabling the use of trimmers that are in motion at times when the pencil beam is away from the target edge. The device consists of two pairs of parallel nickel trimmer blades of 2 cm thickness and dimensions of 2 cm × 18 cm in the beam's eye view. The two pairs of trimmer blades are rotated 90• relative to each other to form a rectangular shape. Each trimmer blade is capable of rapid motion in the direction perpendicular to the central beam axis by means of a linear motor, with maximum velocity and acceleration of 2.5 m/s and 19.6 m/s 2 , respectively. The blades travel on curved tracks to match the divergence of the proton source. An algorithm for selecting blade positions is developed to minimize the dose delivered outside of the target, and treatment plans are created both with and without the DCS. Results: The snout of the DCS has outer dimensions of 22.6 × 22.6 cm 2 and is capable of delivering a minimum treatment field size of 15 × 15 cm 2 . Using currently available components, the constructed system would weigh less than 20 kg. For irregularly shaped fields, the use of the DCS reduces the mean dose outside of a 2D target of 46.6 cm 2 by approximately 40% as compared to an identical plan without collimation. The use of the DCS increased treatment time by 1-3 s per energy layer. Conclusions:The spread of the lateral penumbra of low-energy SS proton treatments may be greatly reduced with the use of this system at the cost of only a small penalty in delivery time.

Objectives This study aimed at examining the effect of the nutrition education program on adolescents' knowledge, attitudes and behaviour in relation to nutrition in rural China. Methods A cluster-randomised intervention trial design was employed. Two middle schools were randomly selected and assigned to the school conducting nutrition education (NE school), or to the Control school, in Mi Yun County, Beijing. From each school 65 seventh-grade students were randomly selected to participate in the study. Nutrition-related knowledge, attitudes and behaviour were measured at pre-and post-intervention surveys with the same instrument. The nutrition education lasted for 6 months. Results After the intervention, more students in NE school knew the main function of dairy products and vegetables, which micronutrient is rich in dairy products and beans, and in meat, and the symptom of food poisoning, than those in Control school. The rate of students who thought nutrition is very important to health, and foods with an expired date should be thrown away in NE school was higher than that in Control school (93.8 vs. 80.3 and 92.3 vs. 78.7 %, respectively). The rate of students who ate vegetables and breakfast everyday in NE school was higher than that in Control school (96.9 vs. 80.3, and 89.2 vs. 75.4 %, respectively). (p \ 0.05). Conclusions This nutrition education programme is effective in improving adolescents' knowledge, attitudes, and behaviour in relation to nutrition; therefore, the nutrition education with interactive and innovative intervention components is strongly recommended for future nutrition promotion programmes for adolescents.

No abstract

The ability of the DCS to provide collimation to each energy layer yielded better conformity in comparison to fixed aperture plans.

For treating peripheral brain lesions--where proton therapy would be expected to have the greatest depth-dose advantage over photon therapy--the lateral penumbra strongly impacts the SS plan quality relative to photon techniques: proton beamlet sigma at patient surface must be small (<7.1 mm for three-beam single-field optimized SS plans) in order to achieve comparable or smaller brain necrosis NTCP relative to photon radiosurgery techniques. Achieving such small in-air sigma values at low energy (<70 MeV) is a major technological challenge in commercially available proton therapy systems.