1. A Study of Effective Dose for Tumor in BNCT Y. Sakurai, H. Tanaka, N. Fujimoto, N. Kondo, M. Narabayashi, Y. Nakagawa, T. Watanabe, Y. Kinashi, M. Suzuki, S. Masunaga, A. Maruhashi and K. Ono Kyoto University Research Reactor Institute, Osaka, Japan In BNCT at Heavy Water Neutron Irradiation Facility of Kyoto University Reactor (KUR-HWNIF), boron dose is estimated based on the following equation: In BNCT at Heavy Water Neutron Irradiation Facility of Kyoto University Reactor (KUR-HWNIF), boron dose is estimated based on the following equation: Boron dose = C BPA × R T/B × CBE BPA × D BPA Boron dose = C BPA × R T/B × CBE BPA × D BPA + C BSH × CBE BSH × D BSH + C BSH × CBE BSH × D BSH C: boron concentration (ppm), C: boron concentration (ppm), RT/B: ratio of tumor to blood (T/B ratio) for BPA, RT/B: ratio of tumor to blood (T/B ratio) for BPA, CBE: compound biological effectiveness, CBE: compound biological effectiveness, D: physical dose per 1ppm of boron-10 (Gy/ppm). D: physical dose per 1ppm of boron-10 (Gy/ppm). The used boron concentration is for whole blood. The degree of BPA uptake for tumorous cell is expressed using T/B ratio based on whole blood. The used boron concentration is for whole blood. The degree of BPA uptake for tumorous cell is expressed using T/B ratio based on whole blood. In clinical study, T/B ratio is decided using the result by F-BPA- PET. However, BPA uptake is smaller than T/B ratio, or almost zero in some actual tumorous cells. In clinical study, T/B ratio is decided using the result by F-BPA- PET. However, BPA uptake is smaller than T/B ratio, or almost zero in some actual tumorous cells. We are reconsidering the definition of effective dose for tumors in BNCT. We are reconsidering the definition of effective dose for tumors in BNCT. INTRODUCTION Tumor dose was re-estimated for the recent BNCT clinical studies, performed at KUR-FWNIF. Tumor dose was re-estimated for the recent BNCT clinical studies, performed at KUR-FWNIF. For the boron dose for tumor due to BPA, it was assumed that the conventional dose based on T/B ratio was considered to be the sub-maximum-estimated dose, and CBE was assumed to be 3.8. For the boron dose for tumor due to BPA, it was assumed that the conventional dose based on T/B ratio was considered to be the sub-maximum-estimated dose, and CBE was assumed to be 3.8. For the minimum-estimated value, boron dose was considered to be similar to that for BSH, as BPA exists just surround the cell. CBE was assumed to be 2.5, the same for BSH. For the minimum-estimated value, boron dose was considered to be similar to that for BSH, as BPA exists just surround the cell. CBE was assumed to be 2.5, the same for BSH. At present, dose estimation is performed using boron concentration of whole blood, both for BPA and BSH. The used CBEs and T/B ratio are decided also based on boron concentration of whole blood. At present, dose estimation is performed using boron concentration of whole blood, both for BPA and BSH. The used CBEs and T/B ratio are decided also based on boron concentration of whole blood. In actual, the surrounding of cell is filled with not blood but interstitial fluid. It can be assumed that the concentration in interstitial fluid equals the concentration in plasma. In actual, the surrounding of cell is filled with not blood but interstitial fluid. It can be assumed that the concentration in interstitial fluid equals the concentration in plasma. Accordingly, boron dose for tumor was assumed to be as follows. The boron concentration for whole blood was used in maximum estimation. In minimum estimation, the boron concentration for plasma was used. Accordingly, boron dose for tumor was assumed to be as follows. The boron concentration for whole blood was used in maximum estimation. In minimum estimation, the boron concentration for plasma was used. In BNCT performed at KUR from 2012 to 2013, 39 irradiations were for head and neck tumors with BPA only, 41 irradiations for brain tumors with BPA only, and 14 irradiations for brain tumors with BPA and BSH. In BNCT performed at KUR from 2012 to 2013, 39 irradiations were for head and neck tumors with BPA only, 41 irradiations for brain tumors with BPA only, and 14 irradiations for brain tumors with BPA and BSH. In BNCT performed at KUR from 2012 to 2013, 39 irradiations were for head and neck tumors with BPA only, 41 irradiations for brain tumors with BPA only, and 14 irradiations for brain tumors with BPA and BSH. In BNCT performed at KUR from 2012 to 2013, 39 irradiations were for head and neck tumors with BPA only, 41 irradiations for brain tumors with BPA only, and 14 irradiations for brain tumors with BPA and BSH. CONCLUSION Based on the re-estimation for tumor dose, the target dose should be decided in consideration of Min.-estimated dose, for the larger T/B ratio. Based on the re-estimation for tumor dose, the target dose should be decided in consideration of Min.-estimated dose, for the larger T/B ratio. Based on the re-estimation for tumor dose, the target dose should be decided in consideration of Min.-estimated dose, for the larger T/B ratio. Based on the re-estimation for tumor dose, the target dose should be decided in consideration of Min.-estimated dose, for the larger T/B ratio. In actual, the cells with larger BPA-uptake and smaller BPA-uptake are mixed. There is thought to be an “effective dose”, between Min. and Sub- Max.-estimated doses. In actual, the cells with larger BPA-uptake and smaller BPA-uptake are mixed. There is thought to be an “effective dose”, between Min. and Sub- Max.-estimated doses. In actual, the cells with larger BPA-uptake and smaller BPA-uptake are mixed. There is thought to be an “effective dose”, between Min. and Sub- Max.-estimated doses. In actual, the cells with larger BPA-uptake and smaller BPA-uptake are mixed. There is thought to be an “effective dose”, between Min. and Sub- Max.-estimated doses. MATERIALS & METHODS RESULTS & DISCUSSIONS Figure 1 Boron distribution for sub- maximum-estimated dose. T/B ratio is decided by F-BPA-PET. CBE = 3.8. Figure 2 Boron distribution for minimum- estimated dose. BPA exists just surround the cell. CBE = 2.5 ? Figure 3 P/B ratios for the clinical studies at KUR. BPA(80 points) BPA(80 points) P/B=1.28±0.08 P/B=1.28±0.08 BSH(14 points) BSH(14 points) P/B=1.44±0.09 P/B=1.44±0.09 The minimum-estimated dose and sub-maximum-estimated dose were re- estimated for the three respective BNCT irradiations in three groups such as H&N tumors, brain tumors with BPA only, and with BPA and BSH. The minimum-estimated dose and sub-maximum-estimated dose were re- estimated for the three respective BNCT irradiations in three groups such as H&N tumors, brain tumors with BPA only, and with BPA and BSH. The minimum-estimated dose and sub-maximum-estimated dose were re- estimated for the three respective BNCT irradiations in three groups such as H&N tumors, brain tumors with BPA only, and with BPA and BSH. The minimum-estimated dose and sub-maximum-estimated dose were re- estimated for the three respective BNCT irradiations in three groups such as H&N tumors, brain tumors with BPA only, and with BPA and BSH. Figure 4 Result for Brain only with BPA. Whole: 26.0ppm, and T/B=3.0. Whole: 26.0ppm, and T/B=3.0. Plasma: 32.0ppm. P/B=1.23. Plasma: 32.0ppm. P/B=1.23. Min.-estimation is 32-34% for Sub-Max. estimation. Min.-estimation is 32-34% for Sub-Max. estimation. Table 1 Summary of the calculated results for tumor dose Comparison of the clinical effects for the similar Sub-Max doses is needed. Comparison of the clinical effects for the similar Sub-Max doses is needed. Comparison of the clinical effects for the similar Sub-Max doses is needed. Comparison of the clinical effects for the similar Sub-Max doses is needed. For the smaller-effect case, it is suspected that many cells didn’t uptake BPA. So, the effective dose is close to Min.-estimated dose. For the smaller-effect case, it is suspected that many cells didn’t uptake BPA. So, the effective dose is close to Min.-estimated dose. For the smaller-effect case, it is suspected that many cells didn’t uptake BPA. So, the effective dose is close to Min.-estimated dose. For the smaller-effect case, it is suspected that many cells didn’t uptake BPA. So, the effective dose is close to Min.-estimated dose. For the larger-effect case, the effective dose is close to Sub-Max estimation. For the larger-effect case, the effective dose is close to Sub-Max estimation. For the larger-effect case, the effective dose is close to Sub-Max estimation. For the larger-effect case, the effective dose is close to Sub-Max estimation. Curve for effective dose