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The size-specific dose estimates (SSDE) have been recommended to replace the volume computed tomography dose index (CTDIvol) because it takes patient size into account. On the other hand, organ dose is thought to be a more appropriate quantity in the radiation protection field due to its correlation with radiation risk. The web-based computed tomography (CT) dose calculator WAZA-ARIv2 only offers organ doses for adults with four different body shapes and for children with five different ages. Since the American Association of Physicists in Medicine (AAPM) offers the conversion factors for SSDE and the correlation of SSDE with organ dose has been demonstrated, implementation of the conversion table might improve the accuracy of WAZA-ARIv2. This study aimed to evaluate a body mass index (BMI)-based and age-based correction method for estimation of the organ dose by using a radiophotoluminescence dosimeter (RGD), an anthropomorphic phantom, and the dose calculator WAZA-ARIv2. RGDs were individually calibrated by using an ISOVOLT TITAN-320 x-ray generator. The ratio of the SSDE conversion factors (CFSSDE) was used as the comparison index. For the BMI-based correction method, the ratio of CFSSDE values for the adult phantoms was expected to be 1.065, and the average ratio of the organ doses for the adult phantoms was 1.163 ± 0.169. For the age-based correction method, the ratio of CFSSDE value for 5- and 10-y-old pediatric phantoms was expected to be 0.889, and the ratios of the organ doses were 0.866 ± 0.024 and 0.909 ± 0.047 for the WAZA-ARIv2 dosimetry system and RGD dosimetry system, respectively. In conclusion, both evaluations of the experimental results showed the consistency between WAZA-ARIv2 and the SSDE conversion factor table. Moreover, the importance of taking the measurement position into account when applying the mass attenuation coefficient was demonstrated according to this study.

In the neutron irradiation field in boron neutron capture therapy, neutron rays and γ-rays are mixed, and it is not easy to selectively measure only neutron rays. The currently used gold activation method is expensive and not suitable for measuring the dose distribution with high spatial resolution. Therefore, there is increasing demand for a simple neutron measurement method for periodic inspections and treatment planning in boron neutron capture therapy (BNCT). Cd has a large nuclear reaction cross section solely for thermal neutrons, and converts thermal neutrons to γ-rays by the (n, γ) reaction. Therefore, in this study, we investigated a method for calculating the thermal neutron fluence by installing Cd as a neutron converter on Cr-doped Al2O3 (Al2O3:Cr), which is a thermoluminescence dosimeter, and measuring the converted γ-ray dose with the Al2O3:Cr. After a 30 min irradiation experiment using the Kyoto University research reactor, the amount of thermoluminescence (TL) increased 101-fold after installing a Cd converter compared with the case of no Cd converter. In addition, the dependence of the TL response on the irradiation time showed excellent proportionality, suggesting the possibility of selectively measuring only the thermal neutron fluence.

We propose a two-step method to converse human tissue materials from patient computed tomography (CT) images, which is required in dose reconstructions for a retrospective study of carbon-ion radiotherapy (CIRT) using Monte Carlo (MC) simulation. The first step was to assign the standard tissues of the International Commission on Radiological Protection reference phantoms according to the CT-number. The second step was to determine the mass density of each material based on the relationship between CT-number and stopping power ratio (Hounsfield unit [HU]-SPR) registered in treatment planning system (TPS). Direct implementation of the well-calibrated HU-SPR curve allows the reproduction of previous clinical treatments recorded in TPS without uncertainty due to a mismatch of the CT scanner or scanning conditions, whereas MC simulation with realistic human tissue materials can fulfill the out-of-field dose, which was missing in the record. To validate our proposed method, depth-dose distributions in the homogenous and heterogeneous phantoms irradiated by a 400 MeV/u carbon beam with an 8 cm spread-out Bragg peak (SOBP) were computed by the MC simulation in combination with the proposed methods and compared with those of TPS. Good agreement of the depth-dose distributions between the TPS and MC simulation (within a 1% discrepancy in range) was obtained for different materials. In contrast, fluence distributions of secondary particles revealed the necessity of MC simulation using realistic human tissue. The proposed material assignment method will be used for a retrospective study using previous clinical data of CIRT at the National Institute of Radiological Sciences (NIRS).

An optically read-out glass gas electron multiplier (G-GEM) detector is expected to simplify complicated quality assurance measurements for hadron therapies by imaging the dose distribution of the ...

An optically read-out glass gas electron multiplier (G-GEM) detector is expected to simplify complicated quality assurance measurements for hadron therapies by imaging the dose distribution of the incident beam. However, the effect of secondary particles from the detector itself has not been well studied. In this paper, we evaluate a design that reduces the secondary particles from the cathode of a G-GEM detector. Specifically, we assembled detectors with thin cathodes and assessed their effect on the secondary particle production in simulations and experiments. The experiments were carried out under 290 MeV/u 12C ion bombardment at the Heavy Ion Medical Accelerator in Chiba. The clinical intensity of the thin cathode detector was compared with that of a conventional thick cathode G-GEM detector. The improved chamber design reduced the dose contributions of secondary particles from the cathode without degrading the dose imaging performance.

Management of patient dose is an effective way to help optimize computed tomography (CT) scanning conditions and CT dose. Organ dose is one of the preferred quantities for radiation protection because of its correlation with radiation risk. To date, the WAZA-ARI dose calculator is the only freely available CT dose calculator also applicable for pediatric patients. However, no reports of its evaluation have appeared since the latest version of WAZA-ARI was released. In this study, to evaluate the latest version of WAZA-ARI, we measured the organ dose in a 5-y-old anthropomorphic phantom by a newly developed radiophotoluminescence glass dosimeter (RGD) dosimetry system and compared these results with the calculation results from WAZA-ARI. The newly designed RGDs have less angular dependence because of the additional filter. RGDs were individually calibrated with the ISOVOLT TITAN-320 x-ray generator. All the experimental measurements for this study were performed using a CT scanner. To consider the difference of CT output between the nominal and actual machine, the measured CTDIair was used to correct the calculation results obtained from WAZA-ARI. After the corrections using the measured CTDIair, the calculation results from WAZA-ARI were relatively lower than the measured results with a range of 8-20%, which corresponds to the dose difference caused by the difference in effective diameter. In conclusion, the calculation accuracy of WAZA-ARI is guaranteed when the normalization factor specific to each CT scanner (CTDIair) and the shape of the phantom are taken into consideration.

The use of carbon ion beams in cancer therapy (also known as hadron therapy) is steadily growing worldwide; therefore, the demand for more efficient dosimetry systems is also increasing because daily quality assurance (QA) measurements of hadron radiotherapy is one of the most complex and time consuming tasks. The aim of this study is to develop a two-dimensional dosimetry system that offers high spatial resolution, a large field of view, quick data response, and a linear dose–response relationship. We demonstrate the dose imaging performance of a novel digital dose imager using carbon ion beams for hadron therapy. The dose imager is based on a newly-developed gaseous detector, a well-type glass gas electron multiplier. The imager is successfully operated in a hadron therapy facility with clinical intensity beams for radiotherapy. It features a high spatial resolution of less than 1 mm and an almost linear dose–response relationship with no saturation and very low linear-energy-transfer dependence. Experimental results show that the dose imager has the potential to improve dosimetry accuracy for daily QA.

For neutron detection applications, we have synthesised glass phosphor materials of Ce3+-doped CaO–Al2O3–B2O3 with consisting boron in two different forms of isotopes, enriched 10B and 11B, called ...

Objectives C-C chemokine receptor type 4 (CCR4) proteins are expressed on the neoplastic cells of adult T-cell leukemia/lymphoma (ATLL). As the mutation status of CCR4 gene is reported to correlate with significant clinical information such as prognosis and response to mogamulizumab, we aimed to establish a screening method that is suitable for clinical laboratory tests. Methods In 34 patients with ATLL, CCR4 mutation analysis, high-resolution melting (HRM) analysis, fragment analysis, and direct sequencing were performed using both genomic DNA and complementary DNA (cDNA). Furthermore, 38 cases of asymptomatic carriers of human T-cell leukemia virus type 1 (HTLV-1) were screened for CCR4 mutation. Results Mutation analysis by direct sequencing of 34 ATLL clinical samples detected CCR4 mutation in four genomic DNA samples and seven cDNA samples, and two novel mutations were identified. All CCR4 mutations detected by direct sequencing were positive for HRM analysis and/or fragment analysis. CCR4 mutation was not detected in the asymptomatic carriers of HTLV-1. Conclusions CCR4 mutation screening by a combination of HRM and fragment analysis using cDNA is a simple and practical method, and it will contribute to better decision making for a therapeutic strategy, providing a rapid CCR4 mutational status to clinicians.

We fabricated neutron detection materials based on Dy3+-doped CaO–Al2O3–B2O3 glasses, including 10B-enriched (10B glass) and 11B-enriched (11B glass) glasses. The glasses were irradiated with X-rays, He ions, or neutrons, and their thermoluminescence (TL) properties were investigated. The TL properties of the 10B and 11B glasses after X-ray or He ion irradiation were similar. Meanwhile, the TL intensity of the 10B glasses was much larger than that of the 11B glasses. The TL peaks of 10B glasses were observed in the irradiation range of 109–1012 n/cm2, and the intensity increased monotonically with neutron fluence.

【目的】日本国内のCT装置の台数は世界的にも多く、日本人のCT被ばく線量は世界的に見ても高いと考えられており、実際の医療現場での撮影の状況や受ける総被ばく線量を適切に評価することが求められている．そこで本研究グループではCT撮影時の臓器被ばく線量計算システムであるWAZA-ARIの開発を行った．WAZA-ARIはWebブラウザから利用できる無料のCT撮影による被ばく線量評価システムであり、現在ユーザー数は3,000名を超え，多くの病院や研究・教育機関にて利用されている．WAZA-ARIは，患者の年齢・性別・体型，CT装置の管電圧や電流値など撮影条件に応じて各臓器の被ばく線量の情報を簡便に算出できるシステムである．より多くのユーザーに利用してもらうために，計算可能なCT装置の拡充や追加機能の研究開発を進めている． 【方法】計算可能なCT装置の拡充を行うため，CT装置メーカーや多くの病院の協力のもと，様々なCT装置から発生するX線の線量情報等を集めた．また，これまで成人に対しては4種類の体格のファントムの線量評価しかできなかったことから，より様々な体型の患者の臓器線量を評価可能とするため，BMIと臓器被ばく線量の関係を調べた． 【結果】現在，WAZA-ARIにて計算可能なCT装置は約50種類となり，国内で利用されている装置台数の70%以上をカバーできた．また，成人の線量計算時に身長・体重を入力することによりBMIに応じて臓器線量を算出するOptional Phantom機能を追加した．さらに近年，ＣＴ被ばく線量の線量指標として利用され始めているSSDE(Size-Specific Dose Estimates)を算出する機能も追加した．, 第78回日本放射線技術学会総会学術大会

To develop thermoluminescent materials for neutron detection, 10B-enriched and 11B-enriched Ca2B2O5:Dy were prepared and their thermoluminescence (TL) properties were investigated after irradiation with X-rays, He ions and thermal neutrons. The TL of these materials was induced by X-rays and He ions and sensitivities to radiation are independent of the boron isotopes in the host materials. On the contrary, the TL intensity of the 10B-enriched sample was significantly higher than that of the 11B-enriched sample after irradiation with thermal neutrons. The high sensitivity to neutrons in the TL of the 10B-enriched sample is attributed to γ-rays and charged particles generated from 10B(n, α)7Li and 10B(n, α)7Li* reactions. In the neutron fluence range of the measurements (3.0 × 105 to 108 neutrons cm−2), the TL intensities attributed to 10B(n, α)7Li and 10B(n, α)7Li* reactions against thermal neutron fluence showed good linearity. In terms of detectable fluence, the new TL materials are more sensitive to neutrons than some existing Dy-containing TL materials.

【目的】アンギオ装置は多くの病院で導入され検査や治療のために利用されているが、散乱線による術者への被曝が懸念されている。以前より防護教育の取組みとして、ヘッドマウントディスプレイ（HMD）を用いた空間線量を可視化する試みを行っており、一定の有用性があることを確認できた一方で、空間線量の表現方法の改善点が指摘された。このため、可視化だけではなく、空中の任意の場所に振動を発生させるハプティクスデバイス（HD）を組合せ、視覚と振動による空間線量のフィードバックにより改善できないかと考えた。本研究ではHMDとHDを組合せたシステムを開発し、技術的な実現性および有用性の検証を行った。 【方法】現在開発中の可視化ソフトウェアはHMDにアンギオ室を模した３Dモデルを投影することができる。これに空中HDを組合せ、HMDに投影された直接線に手指が触れた際、手に振動を伝えるプログラムを開発した。これを可視化ソフトウェアと組合せ、放射線技師を始めとする16名に使用してもらい、有用性についてアンケート形式で調査を行った。 【結果】HMDで可視化された直接線に手指が触れた時に手指に振動を与えることが確認でき、直接線の範囲をフィードバックできることを確認できた。また使用者に有用性に関するアンケートを１から３の３段階評価で行い、防護教育ソフトウェアとしての一定の有用性があることを確認できたが、可視化のみと比べると若干の減少が認められた。 【結論】空中HDを用いた空間線量のフィードバックは、術者への放射線防護への意識付けに一定の効果があることを確認することができた。しかし、振動が小さいことや振動を与える範囲が広くないなどといったデバイスに依存する改善すべき点も挙げられた。今後は、直接線のみならず散乱線による空間線量への応用、またさらに効果的な意識付けにするための方法の模索を行い、教育ツールの開発を継続して行っていく。, 第49回日本放射線技術学会秋季学術大会参加

The size-specific dose estimates (SSDE) have been recommended to replace the volume computed tomography dose index (CTDIvol) because it takes patient size into account. On the other hand, organ dose is thought to be a more appropriate quantity in the radiation protection field due to its correlation with radiation risk. The web-based computed tomography (CT) dose calculator WAZA-ARIv2 only offers organ doses for adults with four different body shapes and for children with five different ages. Since the American Association of Physicists in Medicine (AAPM) offers the conversion factors for SSDE and the correlation of SSDE with organ dose has been demonstrated, implementation of the conversion table might improve the accuracy of WAZA-ARIv2. This study aimed to evaluate a body mass index (BMI)-based and age-based correction method for estimation of the organ dose by using a radiophotoluminescence dosimeter (RGD), an anthropomorphic phantom, and the dose calculator WAZA-ARIv2. RGDs were individually calibrated by using an ISOVOLT TITAN-320 x-ray generator. The ratio of the SSDE conversion factors (CFSSDE) was used as the comparison index. For the BMI-based correction method, the ratio of CFSSDE values for the adult phantoms was expected to be 1.065, and the average ratio of the organ doses for the adult phantoms was 1.163 ± 0.169. For the age-based correction method, the ratio of CFSSDE value for 5- and 10-y-old pediatric phantoms was expected to be 0.889, and the ratios of the organ doses were 0.866 ± 0.024 and 0.909 ± 0.047 for the WAZA-ARIv2 dosimetry system and RGD dosimetry system, respectively. In conclusion, both evaluations of the experimental results showed the consistency between WAZA-ARIv2 and the SSDE conversion factor table. Moreover, the importance of taking the measurement position into account when applying the mass attenuation coefficient was demonstrated according to this study.

We fabricated neutron detection materials based on Dy3+-doped CaO–Al2O3–B2O3 glasses, including 10B-enriched (10B glass) and 11B-enriched (11B glass) glasses. The glasses were irradiated with X-rays, He ions, or neutrons, and their thermoluminescence (TL) properties were investigated. The TL properties of the 10B and 11B glasses after X-ray or He ion irradiation were similar. Meanwhile, the TL intensity of the 10B glasses was much larger than that of the 11B glasses. The TL peaks of 10B glasses were observed in the irradiation range of 109–1012 n/cm2, and the intensity increased monotonically with neutron fluence.

We fabricated neutron detection glasses, Tb3+-doped CaO­Al2O3­B2O3 glasses, including 10B-enriched (10B glass) and 11B-enriched (11B glass) glasses. The glasses were irradiated with X-rays, heavy particles, or neutrons and their thermoluminescence (TL) properties were investigated. The TL properties after X-ray or heavy particle irradiation were the same for the 10B and 11B glasses. Meanwhile, after neutron irradiation, the TL properties of the 10B and 11B glasses were significantly different. The TL intensity of the 10B glasses was higher than that of the 11B glasses, and the TL peak intensity of 10B (n, ¡) reaction had good linearity in the irradiation range of 109 ­1013 neutrons/cm2.

The development of effective therapies has enabled long-term survival for many patients with multiple myeloma (MM). However, the administration of antibody drugs, such as daratumumab, which bind to plasma cell (PC) surface proteins, may prevent PC detection by flow cytometry. We propose VS38 as an alternative antibody for CD38. VS38 recognizes cytoskeleton-linking membrane protein 63 (CLIMP-63) on the rough endoplasmic reticulum, and this protein may be expressed in secretory cells. We investigated VS38 staining in normal hematopoietic cells from five control samples, as well as PCs from 21 patients with plasma cell disorder (PCD). In normal hematopoietic cells, although VS38-stained monocytes, myeloid cells, and a subpopulation of B cells, PCs were significantly and brightly stained by VS38. There was no significant difference in VS38 staining between normal and abnormal PCs obtained from five patients with monoclonal gammopathy of undetermined significance. Furthermore, PCs in 21 PCD cases were clearly identified by VS38 in all cases, in contrast to CD38, even in daratumumab-administered patients whose CD38 epitopes on PCs were masked. These results suggest that the use of the VS38 antibody in flow cytometry contributes to PC detection, independent of therapeutic treatment.

Boron neutron capture therapy (BNCT) is an innovative cancer therapy that selectively destroys only cancer cells by utilizing the reaction between boron agents, which selectively accumulate in cancer cells, and neutron beams. However, the irradiation field in BNCT is a mixture of multiple radiation types, making accurate dose evaluation difficult. For dose evaluation in cancer tissue, which is particularly important, it is essential to discriminate between neutrons and γ-rays mixed in the BNCT irradiation field and to measure them correctly. In this paper, we introduce a new method for selective measurement of neutrons and γ-rays using a thermoluminescent phosphor, which is expected to be a promising method for improving the accuracy of dose evaluations.

【目的】アンギオ装置は多くの病院で導入され検査や治療のため利用されている。患者への侵襲性が低く負担が少ないというメリットがあるが、術中に発生する散乱線によって医師や看護師など術者への職業被ばくが懸念されており、ICRPは術者への放射線被ばくの低減のための勧告を行っている。術者の放射線防護は安定した医療の提供ために非常に重要であり、術者への防護に対する意識付けが必要である。そのためには放射線を可視化することが効果的ではないかと考え、空間線量を可視化するためのソフトウェアを開発し、有効性の確認を行った。 【方法】初めに、アンギオ装置で照射されるコーンビームおよび患者や治療室の３Dモデルを作成し、空間線量をシミュレーションした。次に、現実空間に立体的な３Dモデルを描画するヘッドマウントディスプレイ（HMD）にシミュレーションした空間線量を描画するソフトウェアを開発した。空間線量のシミュレーションには粒子・重イオン輸送計算コード（PHITS）を使用した。HMDにはMicrosoft HoloLens 2(R)を使用し、ソフトウェア開発にはUnity(R)を用いた。また、空間の位置を定めるためのArgument Reality（AR）マーカとしてVuforia(C)社が提供するライブラリを使用した。これらを用いてソフトウェアを開発し有効性を確認した。 【結果】PHITSでシミュレーションした結果をHMD上に投影することができ、技術的に空間線量を可視化できることを確認した。また、HMDのハンドトラッキング機能を用いて利用者の両手を３Dモデルとして空間線量と同時に投影することで、線量の高い場所に触れているかどうかを確かめることができ、放射線防護への意識付けに有効であることが確認できた。今後は実際の治療室をモデルにシミュレーションすることや、遮蔽板の有無による空間線量の変化が視覚的に分かるように改良を行い、教育ツールとしての有効性について引き続き検証を行っていく。, 第77回日本放射線技術学会総会学術大会

Objective. A retrospective study on secondary cancer risk on carbon ion radiotherapy (CIRT) is ongoing at the Heavy Ion Medical Accelerator in Chiba (HIMAC). The reconstruction of the whole-body patient dose distribution is the key issue in the study because dose distribution only around the planning target volume was evaluated in the treatment planning system. Approach. We therefore developed a new dose reconstruction system based on the Particle and Heavy Ion Transport code System (PHITS) coupled with the treatment plan DICOM data set by extending the functionalities of RadioTherapy package based on PHITS (RT-PHITS). In the system, the geometry of patient-specific beam devices such as the range shifter, range compensator, and collimators as well as the individual patient’s body are automatically reconstructed. Various functions useful for retrospective analysis on the CIRT are implemented in the system, such as those for separately deducing dose contributions from different secondary particles and their origins. Main results. The accuracy of the developed system was validated by comparing the dose distribution to the experimental data measured in a water tank and using a treatment plan on an anthropomorphic phantom. Significance. The extended RT-PHITS will be used in epidemiological studies based on clinical data from HIMAC.

Background Multi-parametric flow cytometry (MFC) is a helpful tool for detecting neoplastic cells in malignant lymphoma; however, lymphoma cells can be difficult to detect when characteristic immunophenotypic abnormalities are not evident. We evaluated the stainability of VS38, which is used for multiple myeloma, in normal and abnormal B cells using MFC to develop a new strategy for detecting lymphoma cells. Methods We compared the median fluorescence intensity of VS38 staining in lymphocytes from patients without hematopoietic neoplasms and in B cells from 26 patients with B cell lymphoma (BCL). To evaluate the performance of VS38 gating, we compared VS38-positive B cells with the percentages of BCL cells, and with the mutation ratios of MYD88 L265P measured by droplet digital PCR in patients with lymphoplasmacytic lymphoma (LPL)/Waldenstrom macroglobulinemia (WM). Results CD27-positive memory B cells were stained with VS38, whereas normal lymphocytes were faintly stained. Lymphoma cells were stained with VS38 in 11 of 12 patients with LPL/WM, 3 of 3 with chronic lymphocytic leukemia, 3 of 5 with mantle cell lymphoma, 2 of 4 with follicular lymphoma, and 1 of 1 with splenic marginal zone lymphoma. The percentages of VS38-positive B cells in VS38-positive BCL were equivalent to those of lymphoma cells and the mutation ratios of MYD88 L265P in LPL/WM. Conclusions VS38 identified neoplastic cells in plasma cell disorders and BCL. This might improve the accuracy of BCL diagnosis, especially in patients with LPL/WM.

For neutron detection applications, we have synthesised glass phosphor materials of Ce3+-doped CaO–Al2O3–B2O3 with consisting boron in two different forms of isotopes, enriched 10B and 11B, called 10B-glass and 11B-glass, respectively. For radiation detections, thermoluminescence (TL) properties of the glasses were investigated with X-ray, proton, and neutron irradiations. The TL properties of X-ray- and proton-irradiated 10B- and 11B-glasses were similar while the TL intensity of neutron-irradiated 10B-glass was much greater than that of 11B-glass. The TL of the 10B-glass was observed across the neutron fluence range of 107–1012 neutrons/cm2, and the intensity increased monotonically with neutron fluence.

Management of patient dose is an effective way to help optimize computed tomography (CT) scanning conditions and CT dose. Organ dose is one of the preferred quantities for radiation protection because of its correlation with radiation risk. To date, the WAZA-ARI dose calculator is the only freely available CT dose calculator also applicable for pediatric patients. However, no reports of its evaluation have appeared since the latest version of WAZA-ARI was released. In this study, to evaluate the latest version of WAZA-ARI, we measured the organ dose in a 5-y-old anthropomorphic phantom by a newly developed radiophotoluminescence glass dosimeter (RGD) dosimetry system and compared these results with the calculation results from WAZA-ARI. The newly designed RGDs have less angular dependence because of the additional filter. RGDs were individually calibrated with the ISOVOLT TITAN-320 x-ray generator. All the experimental measurements for this study were performed using a CT scanner. To consider the difference of CT output between the nominal and actual machine, the measured CTDIair was used to correct the calculation results obtained from WAZA-ARI. After the corrections using the measured CTDIair, the calculation results from WAZA-ARI were relatively lower than the measured results with a range of 8-20%, which corresponds to the dose difference caused by the difference in effective diameter. In conclusion, the calculation accuracy of WAZA-ARI is guaranteed when the normalization factor specific to each CT scanner (CTDIair) and the shape of the phantom are taken into consideration.

The use of carbon ion beams in cancer therapy (also known as hadron therapy) is steadily growing worldwide; therefore, the demand for more efficient dosimetry systems is also increasing because daily quality assurance (QA) measurements of hadron radiotherapy is one of the most complex and time consuming tasks. The aim of this study is to develop a two-dimensional dosimetry system that offers high spatial resolution, a large field of view, quick data response, and a linear dose–response relationship. We demonstrate the dose imaging performance of a novel digital dose imager using carbon ion beams for hadron therapy. The dose imager is based on a newly-developed gaseous detector, a well-type glass gas electron multiplier. The imager is successfully operated in a hadron therapy facility with clinical intensity beams for radiotherapy. It features a high spatial resolution of less than 1 mm and an almost linear dose–response relationship with no saturation and very low linear-energy-transfer dependence. Experimental results show that the dose imager has the potential to improve dosimetry accuracy for daily QA.

A new method to measure low intensity neutrons such as secondary neutrons generated in radiotherapy has been developed. In the proposed method, thermal neutron flux is determined by measuring the conversion electrons from 134m Cs generated in a CsI(Tl) scintillator irradiated by neutrons. Because the generated 134m Cs is contained in the scintillator as internal sources, the emitted conversion electrons fully stop in the scintillator and counted with high efficiency. The thermal neutron flux in the neutron radiography facility of the Kindai University's research reactor, UTR-KINKI, was measured by the proposed method. The cadmium difference method was used to separate the contributions of thermal and epi-thermal neutrons. The result was in good agreement with the one obtained by the conventional gold foil activation method. It was concluded that the proposed method is useful for the measurement of thermal neutron flux.

We fabricated 10B-enriched (10B ceramics) and 11B-enriched (11B ceramics) Ca2B2O5:Tb ceramics as thermoluminescence (TL) materials for neutron detection applications. The TL properties of the ceramics after X-ray irradiation, particle beam irradiation, and neutron irradiation were investigated. The TL properties of the 10B ceramics and 11B ceramics after X-ray irradiation were similar, whereas the neutron-induced TL intensity of the 10B ceramics was significantly higher than that of the 11B ceramics. The different TL properties of these ceramics are due to the α-rays, Li ions, and γ-rays generated during the 10B(n, α)7Li reaction. The lower limit of neutron detection by the ceramics was less than 2 × 107 neutrons cm−2, which was lower than those of several previously reported TL materials. Therefore, these ceramics can be applied as TL dosimetry materials for neutron detection.

To accurately estimate an actual dose during radiotherapy treatment, dosimeters are required to be inserted into the affected region in a patient's body. Therefore, we are developing a small size dosimeter consisting of optical fibers and optically stimulated luminescence (OSL) elements. We fabricated two types of small size dosimeters using Eu:BaFBr and Ce:CaF2. We measured the Bragg peak of high energy carbon ions in a water equivalent material. OSL materials showed the quenching effect when irradiated by high linear energy transfer (LET) particles. The sensitivity of Eu:BaFBr and Ce:CaF2 monotonically decreased with different coefficients. The ratio of the signal intensity of these two OSL materials can uniquely determine the sensitivity of each OSL material. We corrected the quenching effect of the OSL dosimeters in the spread out Bragg peak with this relationship.

Two-dimensional (2-D) thermoluminescence (TL) slab dosimeters based on Al2O3:Cr have been recently developed. They have high solidity, spatial resolution, repeatability and linearity, and they can be immersed in water. In the present work, their clinical applicability for quality assurance (QA) testing of the CyberKnife® robotic radiosurgery system was investigated. Those TL slabs were irradiated with 6 MV X-rays and were read out using a 2-D TL reader equipped with a large hot plate and a complementary metal-oxide-semiconductor (CMOS) camera. A comparison was made with the results obtained using radiochromic films (RCFs), which are typically used as 2-D dosimeters. It was found that those TL slabs provided sufficient precision for geometric QA tests and dose-distribution verification. Although the energy dependence for Al2O3:Cr TL slabs was larger than that for tissue-equivalent thermoluminescence dosimeters (TLDs), this had little effect in robotic radiosurgery. Thus, the results demonstrated that those TL slabs can act as replacements for RCFs for QA of robotic radiosurgery.