A new fast algorithm to achieve the dose uniformity around high dose rate brachytherapy stepping source using Tikhonov regularization.

The dose optimization algorithm based on anatomical points is developed to produce rapidly uniform doses over target distances generated on the target volume edges in high-dose-rate (HDR) brachytherapy stepping source application for a treatment length of 6 cm. Monte Carlo modeling of the 60Co HDR brachytherapy source and the surrounding medium were performed using PHITS code. The source dwell times were optimized using Tikhonov regularization in order to obtain uniform dose distribution at the anatomical points located at predefined target distances. The computed dose rates at distances from 0.25 up to 20 cm away from the source were first verified with the literature data sets. Then, the simulation results of the optimization process were compared to the calculations of commercial treatment planning system (TPS) SagiPlan. As a result, the dose uniformity was observed in the isodose curves at the target distances of 10 and 15 mm of the treatment length and the prescribed dose achieved the anatomical points uniformly. The algorithm developed in the present study can be applied for achieving the dose uniformity around the brachytherapy stepping source as a quicker tool for different treatment lengths and different target distances while maintaining the high quality of the treatment plans, saving time by avoiding the manual isodose shaping and then better suitable treatment for patients.

Evidence-based therapy according to the guideline for gastric ulcers is cost-effective in Japan.

Helicobacter pylori (H. pylori) infection is a major cause of gastric ulcers (GU) and eradication of the infection controls the ulcer with no requirement for maintenance therapy. In Japan, an evidence-based guideline (GL) was first published in 2003 (1(st) version) and then again in 2007 (2(nd) version) with a minor revision under support of the Japanese Ministry of Health, Labor and Welfare (GUGLJ). Adherence to its standards is high, estimated at 80%. GU patients aged 18 or older with active ulcers at the time of diagnosis by an endoscopic examination at National Hospital Organization (NHO) hospitals of Japan were enrolled between September 2004 and April 2005. Subjective and endoscopic outcome, medical treatments and medical costs during the following nine months were analyzed, retrospectively. As a result, 935 patients and 270 doctors in charge from 62 NHO hospitals were analyzed. Among H. pylori-positive GU patients, the endoscopic recurrence rate of 24 patients with failure of eradication was 29.2%, which was significantly higher than 8.8% of 194 patients with successful eradication. Successful eradication of H. pylori resulted in significantly lower endoscopic recurrence rates for GU patients either with or without administration of non-steroidal anti-inflammatory drugs (NSAID). GUGLJ adherence scores were significantly related to the specialty or knowledge on the GUGLJ of doctors in charge, and the total medical cost consumed. These results suggest that the therapy of GU along with an evidence-based GL is essential to implement cost-effective treatment and the GI experts or the doctors that understand the GUGLJ very well should perform it.

Simulations of an accelerator-based shielding experiment using the particle and heavy-ion transport code system PHITS.

In order to estimate the biological effects of HZE particles, an accurate knowledge of the physics of interaction of HZE particles is necessary. Since the heavy ion transport problem is a complex one, there is a need for both experimental and theoretical studies to develop accurate transport models. RIST and JAERI (Japan), GSI (Germany) and Chalmers (Sweden) are therefore currently developing and bench marking the General-Purpose Particle and Heavy-Ion Transport code System (PHITS), which is based on the NMTC and MCNP for nucleon/meson and neutron transport respectively, and the JAM hadron cascade model. PHITS uses JAERI Quantum Molecular Dynamics (JQMD) and the Generalized Evaporation Model (GEM) for calculations of fission and evaporation processes, a model developed at NASA Langley for calculation of total reaction cross sections, and the SPAR model for stopping power calculations. The future development of PHITS includes better parameterization in the JQMD model used for the nucleus-nucleus reactions, and improvement of the models used for calculating total reaction cross sections, and addition of routines for calculating elastic scattering of heavy ions, and inclusion of radioactivity and burn up processes. As a part of an extensive bench marking of PHITS, we have compared energy spectra of secondary neutrons created by reactions of HZE particles with different targets, with thicknesses ranging from <1 to 200 cm. We have also compared simulated and measured spatial, fluence and depth-dose distributions from different high energy heavy ion reactions. In this paper, we report simulations of an accelerator-based shielding experiment, in which a beam of 1 GeV/n Fe-ions has passed through thin slabs of polyethylene, Al, and Pb at an acceptance angle up to 4 degrees.

A novel approach to endoscopic colorectal mucosal resection using a three-channel outer tube and multiple forceps: an experimental assessment.

BACKGROUND AND STUDY AIMS: Colorectal endoscopic mucosal resection (EMR) has limitations both anatomically and technically when it is done using the conventional snare wire method. The aim of this study was to develop a new method and instrument for colorectal EMR. METHODS: A total of 21 EMR procedures were done using ten surgical specimens. Saline was injected into the normal submucosa of freshly resected colorectal specimens to prepare a pseudotumor. EMR was performed experimentally by employing a three-channel outer tube with three forceps and a colonoscope with a needle-type precutting knife. This method was assessed in terms of safety and the size of the resected specimens. RESULTS: Perforation occurred only twice in the initial stage of this study. The size of the specimens resected by EMR was 28-39 mm (long diameter 34.8+/-3.11), by 22-28 mm (short diameter 25.8+/-2.07). CONCLUSION: This method can achieve safety and en bloc mucosal resection to the submucosal layer. This novel approach may be promising for clinical application as a new form of endoscopic surgery.