Fish assemblages associated with three types of artificial reefs: density of assemblages and possible impacts on adjacent fish abundance

We evaluated the effectiveness of wooden artificial reefs (ARs) as fish habitat. Three types of ARs, made of cedar logs, broadleaf tree logs, and PVC pipes, respectively, were deployed in triplicate at 8-m depth off Maizuru, Kyoto Prefecture, Sea of Japan, in May 2004. Fish assemblages associated with each of the nine ARs were observed by using SCUBA twice a month for four years. Fish assemblages in the adjacent habitat were also monitored for two years before and four years after reef deployment. In the surveyed areas (ca. 10 m2) associated with each of the cedar, broadleaf, and PVC ARs, the average number of fish species was 4.14, 3.49, and 3.00, and the average number of individuals was 40.7, 27.9, and 20.3, respectively. The estimated biomass was also more greater when associated with the cedar ARs than with other ARs. Visual censuses of the habitat adjacent to the ARs revealed that the number of fish species and the density of individuals were not affected by the deployment of the ARs. Our results support the superiority of cedar as an AR material and indicate that deployment of wooden ARs causes no reduction of fish abundance in adjacent natural reefs

Computational modeling of beam-customization devices for heavy-charged-particle radiotherapy

A model for beam customization with collimators and a range-compensating filter based on the phase-space theory for beam transport is presented for dose distribution calculation in treatment planning of radiotherapy with protons and heavier ions. Independent handling of pencil beams in conventional pencil-beam algorithms causes unphysical collimator-height dependence in the middle of large fields, which is resolved by the framework comprised of generation, transport, collimation, regeneration, range-compensation, and edge-sharpening processes with a matrix of pencil beams. The model was verified to be consistent with measurement and analytic estimation at a submillimeter level in penumbra of individual collimators with a combinational-collimated carbon-ion beam. The model computation is fast, accurate, and readily applicable to pencil-beam algorithms in treatment planning with capability of combinational collimation to make best use of the beam-customization devices.Comment: 16 pages, 5 figure

Medical Application of Synchrotron Radiation 2007

Medical Application of Synchrotron Radiation 200

Dual-Energy X-ray CT for imaging of Organ

The 8th International Conference on Biology and Synchrotron Radiatio

Computational Modeling of Beam-Customization Devices for Heavy-Charged-Particle Radiotherapy

Purpose: This work is aimed to improve the computational model of the beam-customization devices for treatment planning of radiotherapy with heavy charged particles, where only a single collimator and a compensator have been commonly handled with inaccuracy of unphysical collimator dependence in the middle of large fields. Method and Materials: The phase-space theory is applied to the beam transport through the beam-customization devices to enable handling of multiple collimators and a compensator in any order. The theoretical model was experimentally tested with a carbon-ion beam, where two jaw and a multileaf collimators, a 3-cm PMMA half plate for a range compensator, and an 8-cm square aperture for a patient collimator were concurrently used. In the model, a matrix of pencil beams was transported through the devices and a two-dimensional in-air dose distribution on the isocenter plane was computed within ten seconds. For comparison, the penumbra sizes at the field edges formed by the effective collimators were analytically estimated and the dose profiles along four axes on the isocenter plane were experimentally measured. Results: The model computation agreed with the measurement and analytic estimation at a submillimeter level in penumbra size and reproduced the measured dose fluctuation in the middle of the field due to the range-compensator scatter. Conclusions: The model computation is fast, accurate, and readily applicable to pencil-beam algorithms in treatment planning to enable combinational collimation for the best use of beam-customization devices.AAPM Annual Meeting 200