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図書 |
図書
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早川岳英
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論文(リポジトリ) |
論文(リポジトリ)
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笹本, 龍太 ; 宇都宮, 悟 ; 早川, 岳英
概要:
放射線治療の呼吸同期照射において，同期信号の発生からビームオン・オフまでには遅延時間（time\ndelay）がある．今回，time delayの計測に適した動体ファントムの運動パターンと，新潟大学医歯学総合病院の呼吸同期照射システムにおけ
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るtime delayを明らかにすることを目的として検討を行った．動体ファントムの運動波形はサイン波形と等速波形とし，運動幅は30 mmとした．ラジオクロミックフィルムを動体ファントムに乗せ，直径4 mm coneで連続照射を行ったところ，フィルム上の照射陰影はサイン波形で31.7±0.2mm，等速波形で30.4±0.1 mmであり，等速波形の方が実際の運動幅に近く，測定精度が高かった．次に等速波形を用いた10-40%位相の同期照射を行い，照射陰影の長さを理論値と比較したところ，time delayはビームオンで0.11±0.01秒，ビームオフで0.07±0.00秒であった．<br />In respiratory gated radiotherapy, there are time delays between the target entering the gated region and treatment beam on, and between the target exiting the gated region and treatment beam off. The aim of this study was to clarify the appropriate motion profile of motion phantom for measuring the time delays, and to measure the beam on and beam off time delays in respiratory gated radiotherapy system at Niigata University Medical and Dental Hospital. We irradiated radiochromic films on the motion phantom using 4 mm diameter cone without gating. As a motion profile for the motion phantom (motion width: 30.0 mm), a sinusoidal profile and a constant velocity profile ware used. Measured length of the exposure streaks on the films were more accurate with the constant velocity profile than those with the sinusoidal profile (30.4±0.1 mm vs. 31.7±0.2 mm). Then we used the constant velocity profile for gating irradiation with a gating phase range of 10-40%, and compared the exposure streak length with a theoretical value. The calculated beam on time delay was 0.11±0.01 sec, and the beam off time delay was 0.07±0.00 sec.
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論文(リポジトリ) |
論文(リポジトリ)
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内山, 美枝子 ; 坂井, さゆり ; 田中, 美央 ; 奥山, 晶子 ; 早川, 岳英
概要:
看護学専攻３年次対象の『がん看護論』では「がん患者体験演習」を実施している。本演習の学習成果と課題を見出すことを目的に，平成23年度から平成26年度の演習上による学生の記載内容と自由記載からの集計および質的分析をした。結果，学生は，演習でが
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ん患者の立場からあきらめるものについては『形のある大切なもの』，『大切な人』，『大切な活動』，『形のない大切なこと』を選択し，発症時期や告知の時期では『大切な活動』，『形のある大切なもの』を優先的に選択していた。この選択は調査年度が変わっても同じ傾向であった。自由記載の分析結果では，【取捨選択をするという困難さの体感】，【がん患者が体験する喪失感の共有】，【人・ものの存在意義に対するあらたな認識】，【がん患者の支援方法を再考察する機会】の４カテゴリーが抽出された。これらから，本演習での学生の学習成果は一定しており，がん患者の生活と治療を模擬体験し，支援方法を考える機会になったと考えられた。<br />“Practical Training in Caring for Cancer Patients” is offered in “Cancer Nursing Theory Course”, which is intended for juniors majoring in nursing. For the purpose of finding learning achievements and issues of this training program, we compiled and performed a qualitative analysis of student notes and free comments made during the program between 2011 and 2014. As a result, the students put themselves in cancer patients’ position during the program and at onset or notification of the disease preferentially gave up “important activities” and “important things that are tangible” from “important things that are tangible,” “important people,” “important activities,” and “important things that are intangible.” This choice tended to be the same for all the academic years. An analysis of the student comments identified four categories: “experience of difficulty in making a choice,” “sharing of the sense of loss that cancer patients experience,” “renewed awareness of the significance of existence of humans and things,” and “opportunity to reconsider ways to support cancer patients.” These data revealed that the students’learning achievements of this training program were constant, and the students simulated the lives and therapies of cancer patients, making the experience an opportunity to consider ways to support these patients.
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論文(リポジトリ) |
論文(リポジトリ)
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早川, 岳英 ; 山田, 巧 ; 坂井, 裕則 ; 笹本, 龍太 ; 石川, 玉樹 ; 吉田, 泰久
概要:
X線治療の計算によるMU独立検証で等価正方形照射野（等価正方形辺）は，検証の精度に影響するため重要である．等価正方形辺は深さやエネルギーに依存しないと仮定されている．しかし，先行研究で線形加速器Clinac-iX（Varian社製）の矩形照
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射野で求めたファントム散乱係数S_pの測定値と，同じ矩形照射野を等価正方形辺に変換して求めたS_pの推定値の差は深さによって変わる深さ依存があり，その仮定は有効ではなかった．また，Day法やA/P法に比べARC法の等価正方形辺はその深さ依存が小さいことも報告された．本研究は，Clinac-iXとガントリヘッドの構造が異なる線形加速器Synergy（Elekta社製）で，同じ方法によりS_pの測定値と推定値の差を調べた．その結果，Synergyでも深さ依存が見られ，ARC法がDay法やA/P法に比べて小さく，S_pの推定精度が良いことが示された．<br />In X-ray therapy, equivalent square field (side of equivalent square field) is important because it influences the accuracy of monitor unit (MU) independent verification by calculation. It is assumed that equivalent square field does not depend on depth and X-ray energy. However, in Clinac-iX (manufactured by Varian Co.) linear accelerator of previous research, the difference between measured value of S_p obtained by measuring rectangular field and estimated value of S_p obtained from equivalent square field of same rectangular field indicated depth dependency that varied with depth, and it was suggested that the assumption was not valid. And it was reported that the depth dependency in side of equivalent square of ARC method was smaller than Day method and A/P method. In this study, using Synergy (manufactured by Elekta Co.) that was linear accelerator with different structure in the gantry head of Clinac-iX investigated the difference between measured value and estimated value of S_p by the same method of previous research. As result, the depth dependency was found also in Synergy, and it was shown that side of equivalent square of ARC method was smaller than Day method and A/P method, and the estimation accuracy of S_p was better.
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学位論文(リポジトリ) |
学位
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早川, 岳英
概要:
The purpose of this study, improving the calculation accuracy of the system to be used for independent monitor unit (MU)
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verification of the safety check in clinical radiotherapy using X-ray of linear accelerator (linac). Current, treatment planning systems (RTPS) is used for calculate the MU value and to predict the internal dose from computed tomography (CT) images. And it has a problem due to the accidents caused by the abnormal MU value in operation by the user's misunderstanding of high performance RTPS. Therefore, RTPS's MU is necessary to confirm in independent verification, that is to check for tolerance between RTPS's MU and independent verification MU. This paper is focused on method of manual calculation of independent verification, we investigated the output factor estimation of parameters required to MU calculation. The output factor is a function of the change in dose for a field size of the linac. At the simple rectangle field, the area perimeter ratio (Area/Perimeter;A/P) method can convert the radiation field into dose equivalent square field, and the A/P method can be estimated accurately the output factor at arbitrary rectangular field. However, A/P method can not accurately estimate the output factor at the multileaf collimator (MLC) with irregular field in clinical. Thus, the output factor is represented by total scatter factor (S_<c,p>), it adopted a method by multiplying the collimator scatter factor (S_c) and the phantom scatter factor (S_p). First, We proposed the approximation model considering the physical properties of each of S_c and S_p. S_c is depend on the width X and height Y of the radiation field, thus we proposed the approximation model with the variables X and Y. S_p is depend on distance of the center and edge of the radiation field (equal to the radius), thus we proposed the approximation model with a variable radius. Second, the measured values of S_c and S_p at the rectangle field was measured in phantom, then the model parameters will be determined by least-squares curve fitting. As a result, the approximation model fit is good with measurements of S_c, it was found that the approximation model with variables X and Y, S_c value of arbitary rectangular field may be accurately estimated. Also, the approximation model fit is good with measurements of S_p, it was found that the approximation model with a variable radius, S_p value of arbitary rectangular field may be accurately estimated. Finally, the proposed method compares the measured and estimated values of S_c and S_p in with the MLC irregular field in the phantom. And the accuracy of the proposed method was confirmed in clinical irregular field. In this paper, we investigated estimation of the output factor in the calculation of the independent MU verification in clinical radiotherapy using X-ray. We proposed the approximation model of the collimator scatter factor (S_c) and the phantom scatter factor (S_p), and confirmed those proposed method was useful. It can expect improvement of the calculation accuracy when the clinical system of independent MU verification including the method of this study.<br />本研究の目的は,リニアックX線治療の線量単位であるモニターユニット(MU)値の安全確認に使用する独立検証システムの計算精度向上である.現在は,CT画像から線量を予測して治療計画装置(RTPS)でMU値を計算するが,RTPSの高性能化伴い誤った認識と操作ミスが原因の異常なMU値による誤照射事故が問題となっている.そのため,RTPSとは独立した別手段でもMU値を計算し,両者のMU値が許容誤差内か確認することで安全性を確保する独立検証が必要になっている.本論文は,独立検証の一方法の手計算による検証に着目し,そのMU値計算に必要なパラメータの出力係数の推定法を検討した.出力係数はリニアックの照射野サイズに対する線量変化を表す関数で,単純な矩形照射野の照射では,面積周囲長比(Area/Perimeter)から線量等価な正方形照射野に換算するA/P法により,任意の矩形照射野の出力係数を正確に推定できる.しかし,臨床的なマルチリーフコリメータ(MLC)を使った不整形照射野の照射では,A/P法によると出力係数を正確に推定できない.そのため,出力係数を全散乱係数S_<c,p>で表し,それをコリメータ散乱係数S_cとファントム散乱係散S_pに分ける方法を採用した.まず,S_cとS_pのそれぞれの物理的特性を考慮した近似モデルを提案した.S_cは照射野の幅Xと高さYに依存するため,XとYを変数とする近似モデルを作成した.S_pは照射野中心から辺縁までの距離(半径)に依存するため,半径rを変数とする近似モデルを作成した.次に,ファントムで測定した矩形照射野のS_cとS_pの測定値に,最小2乗法でカーブフィットさせてモデルパラメータを求めた.その結果,S_cの測定値と近似モデルのフィットは良好で,XとYを変数として任意の矩形照射野のS_cを正確に推定できることが分かった.また,S_pの測定値と近似モデルのフィットは良好で,rを変数として任意の矩形照射野のS_pを正確に推定できることが分かった.最後に,ファントムで測定したMLCを使った不整形照射野におけるS_cとS_pの測定値と提案法による推定値とを比較し,臨床的な不整形照射野において提案法の正確さを確認した.本論文では,リニアックX線治療のMU値独立検証の計算に必要な出力係数の推定に関し,コリメータ散乱係数S_cおよびファントム散乱係数S_pの近似モデルを提案し,それぞれのモデルによる推定法の有用性を確認した.本方法を臨床のMU値独立検証システムに組み込むと,計算精度の向上が期待できる.<br />新潟大学大学院自然科学研究科<br />平成24年3月23日<br />新大院博（工）甲第381号
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