掲載種別：研究論文（学術雑誌）  

DOI： 10.3390/tomography9010009

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掲載種別：研究論文（学術雑誌）   出版者・発行元：{VM} Media {SP}. zo.o {VM} Group {SK}  

DOI： 10.5603/rpor.a2022.0067

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1007/s12194-022-00655-5

PubMed

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担当区分：筆頭著者,　責任著者   掲載種別：研究論文（学術雑誌）   出版者・発行元：British Institute of Radiology  

Objective:

We evaluated the radiobiological effect of the irradiation time with the interruption time of stereotactic radiosurgery (SRS) using CyberKnife^® (CK) systemfor brain metastases.

Methods:

We used the DICOM data and irradiation log file of the 10 patients with brain metastases from non–small-cell lung cancer (NSCLC) who underwent brain SRS. We defined the treatment time as the sum of the dose–delivery time and the interruption time during irradiations, and we used a microdosimetric kinetic model (MKM) to evaluate the radiobiological effects of the treatment time. The biological parameters, i.e. α₀, β₀, and the DNA repair constant rate (a + c), were acquired from NCI-H460 cell for the MKM. We calculated the radiobiological dose for the gross tumor volume (GTV_bio) to evaluate the treatment time’s effect compared with no treatment time as a reference. The D95 (%) and the Radiation Therapy Oncology Group conformity index (RCI) and Paddick conformity index (PCI) were calculated as dosimetric indices. We used several DNA repair constant rates (a + c) (0.46, 1.0, and 2.0) to assess the radiobiological effect by varying the DNA repair date (a + c) values.

Results:

The mean values of D95 (%), RCI, and PCI for GTV_bio were 98.8%, 0.90, and 0.80, respectively, and decreased with increasing treatment time. The mean values of D95 (%), RCI, and PCI of GTV_bio at 2.0 (a+c) value were 94.9%, 0.71, and 0.49, respectively.

Conclusion:

The radiobiological effect of the treatment time on tumors was accurately evaluated with brain SRS using CK.

Advances in knowledge:

There has been no published investigation of the radiobiological impact of the longer treatment time with multiple interruptions of SRS using a CK on the target dose distribution in a comparison with the use of a linac. Radiobiological dose assessment that takes into account treatment time in the physical dose in this study may allow more accurate dose assessment in SRS for metastatic brain tumors using CK.

DOI： 10.1259/bjro.20220013

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記述言語：日本語   出版者・発行元：公益社団法人 日本医学物理学会  

DOI： 10.11323/jjmp.41.4_195

CiNii Article

CiNii Books

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1002/acm2.13322

PubMed

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その他リンク： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/acm2.13322

担当区分：筆頭著者,　責任著者   掲載種別：研究論文（学術雑誌）   出版者・発行元：Springer Science and Business Media {LLC}  

DOI： 10.1007/s12194-020-00602-2

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その他リンク： http://link.springer.com/article/10.1007/s12194-020-00602-2/fulltext.html

担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：British Institute of Radiology  

Objectives:

We evaluated the radiobiological effectiveness based on the yields of DNA double-strand breaks (DSBs) of field induction with flattening filter (FF) and FF-free (FFF) photon beams.

Methods:

We used the particle and heavy ion transport system (PHITS) and a water equivalent phantom (30 × 30 × 30 cm³) to calculate the physical qualities of the dose-mean lineal energy (y_D) with 6 MV FF and FFF. The relative biological effectiveness based on the yields of DNA-DSBs (RBE_DSB) was calculated for standard radiation such as 220 kVp X-rays by using the estimating yields of SSBs and DSBs. The measurement points used to calculate the in-field y_D and RBE_DSB were located at a depth of 3, 5, and 10 cm in the water equivalent phantom on the central axis. Measurement points at 6, 8, and 10 cm in the lateral direction of each of the three depths from the central axis were set to calculate the out-of-field y_D and RBE_DSB.

Results:

The RBE_DSB of FFF in-field was 1.7% higher than FF at each measurement depth. The RBE_DSB of FFF out-of-field was 1.9 to 6.4% higher than FF at each depth measurement point. As the distance to out-of-field increased, the RBE_DSB of FFF rose higher than those of FF. FFF has a larger RBE_DSB than FF based on the yields of DNA-DSBs as the distance to out-of-field increased.

Conclusions:

The out-of-field radiobiological effect of FFF could thus be greater than that of FF since the spreading of the radiation dose out-of-field with FFF could be a concern compared to the FF.

Advances in knowledge:

The RBE_DSB of FFF of out-of-field might be larger than FF.

DOI： 10.1259/bjro.20200072

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掲載種別：研究論文（学術雑誌）  

DOI： 10.1002/mp.14699

PubMed

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その他リンク： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/mp.14699

掲載種別：研究論文（学術雑誌）   出版者・発行元：Wiley  

<h4>Objectives</h4>To evaluate the effect of interruption in radiotherapy due to machine failure in patients and medical institutions using machine failure risk analysis (MFRA).<h4>Material and methods</h4>The risk of machine failure during treatment is assigned to three scores (biological effect, B; occurrence, O; and cost of labor and repair parts, C) for each type of machine failure. The biological patient risk (BPR) and the economic institution risk (EIR) are calculated as the product of B and O ( B×O ) and C and O ( C×O ), respectively. The MFRA is performed in two linear accelerators (linacs).<h4>Result</h4>The multileaf collimator (MLC) fault has the highest BPR and second highest EIR. In particular, TrueBeam has a higher BPR and EIR for MLC failures. The total EIR in TrueBeam was significantly higher than that in Clinac iX. The minor interlock had the second highest BPR, whereas a smaller EIR. Meanwhile, the EIR for the LaserGuard fault was the highest, and that for the monitor chamber fault was the second highest. These machine failures occurred in TrueBeam. The BPR and EIR should be evaluated for each linac. Further, the sensitivity of the BPR, it decreased with higher T1/2 and α/β values. No relative difference is observed in the BPR for each machine failure when T1/2 and α/β were varied.<h4>Conclusion</h4>The risk faced by patients and institutions in machine failure may be reduced using MFRA.<h4>Advances in knowledge</h4>For clinical radiotherapy, interruption can occur from unscheduled downtime with machine failures. Interruption causes sublethal damage repair. The current study evaluated the effect of interruption in radiotherapy owing to machine failure on patients and medical institutions using a new method, that is, machine failure risk analysis.

DOI： 10.1002/acm2.13126

PubMed

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その他リンク： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/acm2.13126

担当区分：筆頭著者,　責任著者   掲載種別：研究論文（学術雑誌）  

DOI： 10.1002/acm2.13110

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その他リンク： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/acm2.13110

担当区分：筆頭著者,　責任著者   掲載種別：研究論文（学術雑誌）  

DOI： 10.1002/acm2.13081

PubMed

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その他リンク： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/acm2.13081

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.3390/cancers12102955

PubMed

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掲載種別：研究論文（学術雑誌）   出版者・発行元：British Institute of Radiology  

Objective:

To evaluate the biological effectiveness of dose associated with interruption time; and propose the dose compensation method based on biological effectiveness when an interruption occurs during photon radiation therapy.

Methods:

The lineal energy distribution for human salivary gland tumor was calculated by Monte Carlo simulation using a photon beam. The biological dose (D_bio) was estimated using the microdosimetric kinetic model. The dose compensating factor with the physical dose for the difference of the D_bio with and without interruption (Δ) was derived. The interruption time (τ) was varied to 0.1, 0.2, 0.3, 0.4, 0.5, 1, 2, 3, 4, 5, 10, 20, 30, 40, 50, 75, and 120 min. The dose per fraction and dose rate varied from 2 to 8 Gy and 0.1 to 24 Gy/min, respectively.

Results:

The maximum Δ with 1 Gy/min occurred when the interruption occurred at half the dose. The Δ with 1 Gy/min at half of the dose was over 3% for τ &gt;= 20 min for 2 Gy, τ = 10 min for 5 Gy, and τ = 10 min for 8 Gy. The maximum difference of the Δ due to the dose rate was within 3% for 2 and 5 Gy, and achieving values of 4.0% for 8 Gy. The dose compensating factor was larger with a high dose per fraction and high-dose rate beams.

Conclusion:

A loss of biological effectiveness occurs due to interruption. Our proposal method could correct for the unexpected decrease of the biological effectiveness caused by interruption time.

Advances in knowledge:

For photon radiotherapy, the interruption causes the sublethal damage repair. The current study proposed the dose compensation method for the decrease of the biological effect by the interruption.

DOI： 10.1259/bjr.20200125

PubMed

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

PURPOSE: To investigate the dosimetric impact between the anisotropic analytical algorithm (AAA) and the Acuros XB (AXB) algorithm in volumetric-modulated arc therapy (VMAT) plans for high-grade glioma (HGG). METHODS: We used a heterogeneous phantom to quantify the agreement between the measured and calculated doses from the AAA and from the AXB. We then analyzed 14 patients with HGG treated by VMAT, using the AAA. We newly created AXB plans for each corresponding AAA plan under the following conditions: (1) re-calculation for the same number of monitor units with an identical beam and leaf setup, and (2) re-optimization under the same conditions of dose constraints. The dose coverage for the planning target volume (PTV) was evaluated by dividing the coverage into the skull, air, and soft-tissue regions. RESULTS: Compared to the results obtained with the AAA, the AXB results were in good agreement with the measured profiles. The dose differences in the PTV between the AAA and re-calculated AXB plans were large in the skull region contained in the target. The dose difference in the PTV in both types of plan was significantly correlated with the volume of the skull contained in the target (r = 0.71, p = 0.0042). A re-optimized AXB plan's dose difference was lower vs. the re-calculated AXB plan's. CONCLUSIONS: We observed dose differences between the AAA and AXB plans, in particular in the cases in which the skull region of the target was large. Considering the phantom measurement results, the AXB algorithm should be used in VMAT plans for HGG.

DOI： 10.1016/j.ejmp.2020.04.007

PubMed

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記述言語：英語   出版者・発行元：(公社)日本放射線技術学会  

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記述言語：日本語   出版者・発行元：日本定位放射線治療学会  

複数の脳転移に対する単一アイソセンタVMAT(SIVMAT)の患者セットアップの並進誤差が線量の不確かさに及ぼす影響を評価した。治療計画装置上において、30×30×30cm3の仮想水等価ファントム上で、二つの模擬腫瘍肉眼腫瘍体積(GTV)を作成した。並進誤差が増加するにつれて、各GTVと計画標的体積(PTV)の線量カバレッジは低下し、GTVとPTVの直径が小さい場合、線量カバレッジはより低下した。各GTVおよびPTVの線量カバレッジは、GTVおよびPTVの体積が小さいほど、並進誤差が大きくなるにつれて低下した。GTVの直径が0.5cm、1.0cm、1.5cm、2.0cmの場合、至適PTVマージンはそれぞれ8.6mm、6.1mm、3.6mm、1.0mmであった。また、GTVの体積が1.0cm3、5.0cm3、10.0cm3、14.0cm3の場合、至適PTVマージンはそれぞれ7.0mm、3.4mm、1.8mm、1.0mmであった。1.0mm PTVマージンを設定した場合、PTV線量カバレッジの低下率5%以内を満たすためには、2.0cm以上の直径または14.0cm3以上の体積をもつGTVが必要であった。

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier {BV}  

Background:Previously, the physical dose-enhancement factor (DphysEF) enhancement was introduced. However, the dose enhancement considering the biological effectiveness was not shown. Purpose:The aim of the current study was to evaluate the biological dose-enhancement factor (DbioEF) by the dose rate and to compare the DphysEF and the DbioEF in Lipiodol for liver Stereotactic Body Radiation Therapy (SBRT). Materials and methods:Flattening-filter-free (FFF) 6-MV (6MVX) and 10MVX beams were delivered by TrueBeam. A virtual inhomogeneity phantom and a liver SBRT patient-treatment plan were used. The DphysEF and lineal energy distribution ( y ) distribution was calculated from Monte Carlo simulations. Using a microdosimetric-kinetic (MK) model that is estimated based on the linear-quadratic formula for Lipiodol using human liver hepatocellular cells (HepG2), the biological dose and biological dose enhancement factor (DbioEF) were calculated. The dose rate in the simulation was changed from 0.1 to 24 Gy/min. Results:The DbioEF (DR:2Gy/min) and DphysEF with 10MVX FFF beam were 23.2% and 19.1% at maximum and 12.8% and 11.1% on average in the Lipiodol. In the comparison of the DbioEF between 0.1-24 Gy/min, the DbioEF was 21.2% and 11.1% with 0.1 Gy/min for 6MVX and 10 MVX, respectively. The DbioEF was larger than DEF for the 6MVX and 10MVX FFF beams. In clinical cases with the 10MVX FFF beam, the DbioEF and DphysEF in the Lipiodol region can increase the in-tumor dose by approximately 11% and 10%, respectively, without increasing the dose to normal tissue. Conclusions:The lower-energy and higher-dose-rate beams were contributed to the biological dose. The Lipiodol caused the enhancement of the physical dose and biological effectiveness. Advances in knowledge:The biological dose enhancement (DbioEF) should be considered in the high-density material such as the Lipiodol.

DOI： 10.1016/j.rpor.2019.10.006

PubMed

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記述言語：英語   出版者・発行元：(公社)日本放射線技術学会  

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担当区分：筆頭著者,　責任著者   掲載種別：研究論文（学術雑誌）   出版者・発行元：Public Library of Science ({PLoS})  

DOI： 10.1371/journal.pone.0206673

PubMed

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1093/jrr/rry041

Web of Science

PubMed

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

We examine the contrast agent Lipiodol effect on the relative biological effectiveness (RBE) values for flattening filter free (FFF) and flattening filter (FF) beams of 6 MV-Xray (6 MVX) and 10 MVX.Lipiodol was placed at 5 cm depth in water. According to the microdosimetric kinetic model, the RBE values for killing the human liver hepatocellular cells were calculated from dose and lineal energy (yd(y)) from Monte Carlo simulations. RBE200kVX and RBECo were defined as the ratios of dose using reference radiation (200 kVX, Co-ɤ) to the dose of test radiation (FFF and FF beams for 6 MV and 10 MV) to produce the same biological effects. The dose enhancement RBE (RBEDE) was defined as the ratios of a dose without Lipiodol to with Lipiodol using to produce the same biological effects. The dose needed to achieve 10% (D10%) and 1% cell survival (D1%) was evaluated by cell surviving fraction (SF) formula.The deviation of mean y‾D values with and without Lipiodol were 3.9-4.8% for 6 MVX and 3.5-3.6% for 10 MVX. The RBE200kVX and RBECo with Lipiodol were larger than that without Lipiodol. The RBEDE was larger for FFF beam than for FF beam. The deviation of RBEDE for FFF and FF beams of 6 MVX was larger than that of 10 MVX.The presence of Lipiodol seemed to locally increase the absorbed dose and to also cause an enhancement of the relative biological effectiveness.

DOI： 10.1016/j.ejmp.2018.01.018

PubMed

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掲載種別：研究論文（学術雑誌）  

DOI： 10.1177/1010428317705033

PubMed

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その他リンク： http://journals.sagepub.com/doi/full-xml/10.1177/1010428317705033

開催年月日： 2023年10月

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