Dose ratio proton radiography using the proximal side of the Bragg peak

Purpose: In recent years there has been a movement towards single-detector proton radiography, due to its potential ease of implementation within the clinical environment. One such single-detector technique is the dose ratio method, in which the dose maps from two pristine Bragg peaks are recorded beyond the patient. To date, this has only been investigated on the distal side of the lower energy Bragg peak, due to the sharp fall-off. We investigate the limits and applicability of the dose ratio method on the proximal side of the lower energy Bragg peak, which has the potential to allow a much wider range of water-equivalent thicknesses (WET) to be imaged. Comparisons are made with the use of the distal side of the Bragg peak. Methods: Using the analytical approximation for the Bragg peak we generated theoretical dose ratio curves for a range of energy pairs, and then determined how an uncertainty in the dose ratio would translate to a spread in the WET estimate. By defining this spread as the accuracy one could achieve in the WET estimate, we were able to generate look-up graphs of the range on the proximal side of the Bragg peak that one could reliably use. These were dependent on the energy pair, noise level in the dose ratio image and the required accuracy in the WET. Using these look-up graphs we investigated the applicability of the technique for a range of patient treatment sites. We validated the theoretical approach with experimental measurements using a complementary metal oxide semiconductor active pixel sensor (CMOS APS), by imaging a small sapphire sphere in a high energy proton beam. Results: Provided the noise level in the dose ratio image was 1% or less, a larger spread of WETs could be imaged using the proximal side of the Bragg peak (max 5.31 cm) compared to the distal side (max 2.42 cm). In simulation it was found that, for a pediatric brain, it is possible to use the technique to image a region with a square field equivalent size of 7.6 cm2, for a required accuracy in the WET of 3 mm and a 1% noise level in the dose ratio image. The technique showed limited applicability for other patient sites. The CMOS APS demonstrated a good accuracy, with a root-mean-square-error of 1.6 mm WET. The noise in the measured images was found to be σ =1.2% (standard deviation) and theoretical predictions with a 1.96σ noise level showed good agreement with the measured errors. Conclusions: After validating the theoretical approach with measurements, we have shown that the use of the proximal side of the Bragg peak when performing dose ratio imaging is feasible, and allows for a wider dynamic range than when using the distal side. The dynamic range available increases as the demand on the accuracy of the WET decreases. The technique can only be applied to clinical sites with small maximum WETs such as for pediatric brains

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Bacillus nattoがCandida albicansとC.stellatoideaに対してはその発育を阻止するが,他のCandida種の発育は阻止しない抗真菌物質を菌体外に産生することを確認した。B.nattoの培養上澄より活性炭の添加と限外ろ過(分子量 10,000)処理により粗抗カンジダ物質(ACS)を得た。粗ACSは供試したC.albicans154株の全株の発育を阻止したが,C.tropicalisの全株(5株)は発育が阻止されないことをペーパーディスク法により確認した。この方法により,粗ACSはこの2種のカンジダを明確に分別できることが判明した。粗ACSのC.albicansに対するMICは400μg/mlであったが,C.tropicalisは12,800μg/mlでも発育は阻止されなかった。-20℃に保存した粗ACSと4℃又は-20℃に保存した粗ACS溶液は初期の活性を8週間保持した。粗ACSのC.albicansに対する作用は主に静菌的であり,また弱く殺菌的にも作用した。この結果は粗ACSで処理したC.albicansの形態変化とも一致した。粗ACS含有サブロー寒天平板上のC.albicansの形態は,初めに一部の菌体が膨化し,次いで破壊される像が観察された。また,粗ACS含有液体培地中におけるC.albicansの形態は破壊され遊離した細胞質様物質が菌体周囲に存在し,多くの菌体はグラム陰性に染色された。以上の成績から,より簡単で迅速かつ正確なC.albicansの同定が,このペーパーディスク法と他の同定法とを併用することによって成し得ることが示唆された。Bacillus natto produced antifungal substance extracelluraly which inhibited the growth of Candida albicans and C. stellatoidea, but did not inhibit the growth of other Candida species. This antifungal substance was obtained from the culture filtrate by a procedure including the addition of active carbon and molecular filtration (MW 10,000), and this substance was designated as crude Anti-Candida substance (ACS). By paper disk method with crude ACS, the inhibitory zone was detected in all strains of C. albicans but not detected in any strains of C. tropicalis. A clear distinguishment between these two species was obtained by this method. MIC of crude ACS against C. albicans was 400 μg/ml but C. tropicalis growth was not inhibited at 12,800 μg/ml of crude ACS. Crude ACS which was stored at -20℃ and crude ACS solution which was stored at 4℃ or -20℃ retained its original inhibitory activity for 8 weeks. The action of crude ACS against C. albicans was mainly bacteriostatic and weakly bacteriocidal. This result was also identical with the morphological aspect of C. albicans treated with crude ACS. Regarding the morphological aspects of C. albicans on crude ACS-Sabouraud\u27s dextrose agar plate some organisms were swollen at first, and as a secondary step these were destroyed. In conclusion, this study suggests that a more easy, rapid, and exact identification of C. albicans can be done by the utilization this paper disk method in parallel with other identification methods

The NMR Spectroscopic Evaluation of Immobility of a Crowd of Porphyrin Rings Combined with Dendritic Poly(L-lysine)s

Since the dendritic poly(L-lysine)s combining eight to thirty-two free base-porphyrins showed split circular dichroism at the Soret band in toluene/N,N-dimethylformamide (9/1, v/v), the immobility of porphyrin rings was evaluated by 1H NMR measurements in terms of the peak width at half-height and spin-lattice relaxation time