Radiation therapy (RT) in general requires a treatment period of 5 to 7 weeks. Tumor shrinkage in response to RT and weight loss due to radiationinduced mucositis may impact on the dose distribution in both target and organ at risk in patients Abstract : The treatment period over which radiation therapy is administered extends over several weeks. Since tumor shrinkage in response to radiation therapy and weight loss due to radiation-induced mucositis may impact on the dose distribution in both target and organ at risk in patients with head and neck cancer, the anatomical changes of tumor and neck volumes during this period should be taken into consideration. We investigated the anatomical changes that occurred in the target and normal structure of the neck during radiation therapy for pharyngeal cancer, and evaluated the necessity of an adaptive strategy. Ten patients with pharyngeal cancer who underwent radical chemoradiation therapy using 3-dimensional conformal radiation therapy RT ( ORIGINAL Changes

The aim of this study was to quantify the effect of multi-leaf collimators (MLCs) with different leaf widths on the planning of intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT). Toward this objective, dose transmission through a high-definition 120-leaf MLC (HD120MLC) and 120-leaf Millennium MLC (M120MLC) was investigated, using it with a test case and clinical case studies. In test case, studies with IMRT and VMAT plans, the difference in MLC leaf width had a limited effect on planning target volumes (PTVs). Organs at risk (OARs) were more affected by a reduction in dose transmission through the MLC than by a reduction in MLC leaf width. The results of the test case studies and clinical case studies were mostly similar. In the latter, the different MLCs had no effect on the PTV regardless of the treatment method; however, the HD120MLC plans achieved dose reductions to OARs similar to or larger than the dose reduction of the M120MLC plans. The similar results of the test case and clinical case studies showed that despite a limitation of the irradiation field size, the HD120MLC plans were superior.

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Purpose: The aim of this study to evaluate influence of rectal gas on dose distribution during prostate VMAT. Methods: Our subjects were 10 patients who have received VMAT for prostate cancer at our hospital. In this study, we made four types of VMAT plan. The angles of rotation were as follows: clockwise from 181–179° and 179–181° (Full arc), clockwise from 200–160° and counter‐clockwise from 160–200° (Partial arc1), clockwise from 220‐ 140° and counter‐clockwise from 140–220° (Partial arc2), clockwise from 240–120° and counter‐clockwise from 120–240° (Partial arc3). The rectal contour used for the reference treatment plan each had 5% or less rectal gas. In order to evaluate the effects of the rectal gas on the dose distribution, we created a rectal contour for assessment separate from the contour used for the reference treatment plans. In the contour for evaluation, the Hounsfield unit (HU) value of the gas was assigned for the total volume of the rectal contour. A HU value of −950 was adopted for simulating the rectal gas. The 3DVH version 2.2 was used for evaluation, and evaluation was performed based on the concordance rate between the contour being evaluated and that of the reference treatment plans. The dose difference (DD), distance to agreement (DTA), and gamma analysis (GA) were used to obtain the concordance rate. The contours being evaluated were CTV, PTV, rectum and bladder. Results: The results of DD, DTA, and GA showed that the rectum, the CTV and rectum had the lowest concordance rates. Irrespective of DD, DTA, or GA, the treatment plan based on full arc had a higher concordance rate. Conclusion: With respect to the effect of rectal gas on the dose distribution in prostate VMAT, it was shown that full arc might be the least susceptible.

Field investigation of a tidal river was carried out in order to understand environmental structure at the Doi river flowing in Sakai, Osaka. On the basis of the distribution of velocity, salinity, dissolved oxygen, and so on, responsible mechanism of degraded environment was presumed. As one of possible restoration method, horizontal ejection of fresh water with rich dissoved oxygen just above the bottom was proposed. Impact assessment of the ejection was also presented with experimental results by using the particle image velocimetry.