Sub-nanometric High-Entropy Alloy Cluster: Hydrogen Spillover Driven Synthesis on CeO2 and Structural Reversibility.

High-entropy alloy (HEA) nanoparticles (NPs) have attracted significant attention as promising catalysts owing to the various unique synergistic effects originating from the nanometer-scale, near-equimolar mixing of five or more components to produce single-phase solid solutions. However, the study of sub-nanometer HEA clusters having sizes of less than 1 nm remains incomplete despite the possibility of novel functions related to borderline molecular states with discrete quantum energy levels. The present work demonstrates the synthesis of CeO2 nanorods (CeO2-NRs) on which sub-nanometer CoNiCuZnPd HEA clusters were formed with the aid of a pronounced hydrogen spillover effect on readily reducible CeO2 (110) facets. The CoNiCuZnPd HEA sub-nanoclusters exhibited higher activity during the reduction of NO by H2 even at low temperatures compared with the corresponding monometallic catalysts. These clusters also showed a unique structural reversibility in response to repeated exposure to oxidative/reductive conditions, based on the sacrificial oxidation of the non-noble metals. Both experimental and theoretical analyses established that multielement mixing in quantum-sized regions endowed the HEA clusters with entirely novel catalytic properties.

Interfractional Rectal Displacement Requiring Repeated Precaution Did Not Correlate to Biochemical Control and Rectal Toxicity in Patients with Prostate Cancer Treated with Image-guided Intensity-modulated Radiation Therapy.

AIM: To investigate the correlation between frequency of action level of interfractional rectal displacement requiring repeated precaution in patients with prostate cancer and late toxicity from image-guided intensity-modulated radiation therapy (IG-IMRT) using helical tomotherapy. PATIENTS AND METHODS: We examined 264 patients who underwent IG-IMRT during 2007-2011. Megavoltage computed tomographic (MVCT) images were acquired before radiation therapy and was examined with soft-tissue matching by comparing treatment planning images within 9,345 fractions. Displacement of the anterior rectal region larger than 5 mm, requiring repeated precaution, was defined as the level of rectal displacement requiring action (ARD). RESULTS: ARD was identified in 815 (7.7%) out of 9,345 fractions and at least once in 82% (216/264) of patients. The highest incidence of ARD (11%) was found during the initial week of treatment (first five and next five fractions), after which the incidence decreased to 6% (p<0.0001). Patients with lean body (lower body mass index (BMI) tended to have a higher incidence of ARD. We identified 16 (6%) cases of gastrointestinal toxicity and 12 (4.5%) genitourinary toxicities as a late adverse reaction (3 months or later after IG-IMRT). There was no correlation between ARD and late toxicity. Prostate-specific antigen (PSA) control was also similar (p=0.12) between those with ARD (96% at 5 year) and those without ARD (88%). CONCLUSION: ARD occurred predominantly in lean patients, during the initial week of treatment and became less likely over time. ARD was not correlated to late toxicity and PSA control, therefore, IG-IMRT technique was able to adequately control error due to interfractional prostate and rectal motion.

Frequency and predisposing factors for interfractional rectal displacement requiring repeated precaution in prostate cancer patients treated with image-guided intensity-modulated radiation therapy.

AIM: To investigate the frequency and characteristics of interfractional rectal displacement in patients with prostate cancer treated with image-guided intensity-modulated radiation therapy (IG-IMRT) using helical tomotherapy. PATIENTS AND METHODS: Data for a total of 256 patients were analyzed. Megavoltage computed tomography (MVCT) images were acquired before radiation therapy and interfractional rectal displacement was assessed with soft-tissue matching by comparing treatment planning images within 9,445 fractions. Anterior rectal region displacement larger than 5 mm, requiring repeated precaution, was defined as the action level of rectal displacement (ARD). RESULTS: ARD was identified in 676 (7.2%) out of 9,445 fractions and at least once in 75% (190/256) of patients. Univariate analysis identified three predisposing factors for ARD: body mass index (BMI), rectal volume and prostate volume. Multivariate logistic regression analysis revealed that lower BMI and large rectal volume were statistically significant predictors of ARD. The highest incidence of ARD (13.6% and 9.1%) was found during the initial two weeks of treatment (first five and next five fractions), after which the incidence decreased to 5.96% (p<0.0001). CONCLUSION: ARD was identified in 7.9% of fractions and in 74.8% of patients and was most likely to occur in patients with a low BMI and/or large rectal volume. ARD occurred predominantly during the initial two weeks of treatment and became less likely over time.

Analysis of intrafractional organ motion by megavoltage computed tomography in patients with lung cancer treated with image-guided stereotactic body radiotherapy using helical tomotherapy.

AIM: To analyze intrafractional organ motion in patients with lung cancer treated with image-guided stereotactic body radiotherapy using helical tomotherapy (SBRT-HT). PATIENTS AND METHODS: Data from 25 patients with lung cancer who received 50 Gy/5 fractions of SBRT-HT were analyzed. Slow-scan megavoltage computed tomography (MVCT) images were acquired before (pre-MVCT) and after (post-MVCT) each fraction. We analyzed the imaging quality of the 124 post-MVCT images to identify tumor contours using low-density settings. Next we examined tumor contour deviations from the planning target volume (PTV) in post-MVCT images for intrafractional tumor displacement. RESULTS: Image quality was determined as good in 111/124 images from 22 patients (92%). None of the upper lung tumor images were of poor quality (74 images in 15 patients), whereas lower lung tumors yielded 14 poor-quality images out of the 50 images (3/10 patients). The difference in image quality between upper and lower lung tumors was statistically significant (p<0.01), especially when accompanied by interstitial lung shadows. Deviations in tumor position in post-MVCT images were analyzed in 110 images from 23 patients and revealed 99 images (90%) with tumor contours confined to PTV. In upper lung tumors, 4/74 images in 15 patients (5.4%) showed tumor contour deviations outside PTV. Lower lung tumors showed a higher rate of deviation with 7/36 images in 8 patients (19.4%) showing tumor contour deviations outside PTV (p<0.05). The maximum deviation was 1 mm for upper lung tumors and 2 mm for lower lung tumors. CONCLUSION: Upper lung tumors are good candidates for MVCT image-guided SBRT-HT. However, lower lung tumors, especially those adjacent to the diaphragm or pleura, can be difficult to assess, warranting precise dose delivery by MVCT image-guided SBRT-HT.

Potential risk of alpha-glucosidase inhibitor administration in prostate cancer external radiotherapy by exceptional rectal gas production: a case report.

INTRODUCTION: Radiotherapy is a standard treatment for prostate cancer, and image-guided radiotherapy is increasingly being used to aid precision of dose delivery to targeted tissues. However, precision during radiotherapy cannot be maintained when unexpected intrafraction organ motion occurs. CASE PRESENTATION: We report our experience of internal organ motion caused by persistent gas production in a patient taking an alpha-glucosidase inhibitor. A 68-year-old Japanese man with prostate cancer visited our institution for treatment with helical tomotherapy. He suffered from diabetes mellitus and took an alpha-glucosidase inhibitor. Routine treatment planning computed tomography showed a large volume of rectal gas; an enema was given to void the rectum. Subsequent treatment planning computed tomography again showed a large volume of gas. After exercise (walking) to remove the intestinal gas, a third scan was performed as a test scan without tight fixation, which showed a sufficiently empty rectum for planning. However, after only a few minutes, treatment planning computed tomography again showed extreme accumulation of gas. Therefore, we postponed treatment planning computed tomography and consulted his doctor to suspend the alpha-glucosidase inhibitor, which was the expected cause of his persistent gas. Four days after the alpha-glucosidase inhibitor regimen was suspended, we took a fourth treatment planning computed tomography and made a treatment plan without gas accumulation. Thereafter, the absence of rectal gas accumulation was confirmed using daily megavolt computed tomography before treatment, and the patient received 37 fractions of intensity-modified radiotherapy at 74 Gy without rectal gas complications. In this case study, the alpha-glucosidase inhibitor induced the accumulation of intestinal gas, which may have caused unexpected organ motion, untoward reactions, and insufficient doses to clinical targets. CONCLUSIONS: We suggest that patients who are taking an alpha-glucosidase inhibitor for diabetes should discontinue use of that particular medicine prior to beginning radiotherapy.

Analysis of intrafractional organ motion for patients with prostate cancer using soft tissue matching image-guided intensity-modulated radiation therapy by helical tomotherapy.

AIM: To analyze an intrafractional organ motion for patients with prostate cancer using soft tissue matching by megavolt computed tomography (MVCT) images during the course of image-guided intensity-modulated radiotherapy (IGRT-IMRT) using helical tomotherapy. PATIENTS AND METHODS: Data from a total of 10 patients with prostate cancer who received IGRT-IMRT were analyzed, and MVCT images were acquired before and after radiation therapy. Intra-fractional movement and PTV margins for soft tissue matching were calculated by comparing treatment planning images with 740 MVCT images for right-left (RL), superior-inferior (SI), and anteroposterior (AP) dimensions. A total of 74 Gy/37 fractions were administered. A margin to compensate for these variations was calculated using the van Herk's equation. RESULTS: The intrafractional motion was 0.03 (-1.3 to 1.4) ±0.39 mm in the RL dimension, 0.08 (-1.8 to 0.28) ±0.73 mm in the SI dimension, and 0.52 (-1.8 to 1.8) ±0.63 mm in the AP dimension. The required PTV margin was 0.60 mm, 1.10 mm, and 0.78 mm in the RL, SI, and AP dimensions, respectively. Only one patient exhibited a deviation greater than 5 mm only once in 37 fractions (1/370=0.2%) caused by anal contraction. CONCLUSION: The PTV margin in soft tissue matching IGRT-IMRT by helical tomotherapy for a patient with prostate cancer was 3 mm or less, and our tentative PTV margin of 3-5 mm is sufficient for most patients, if adequate instruction for avoiding anal contraction is given.

Assessment of planning target volume margin for a small number of vertebral metastatic lesions using image-guided intensity-modulated radiation therapy by helical tomotherapy.

AIM: To evaluate an appropriate planning target volume (PTV) margin in for one to three vertebral metastases using megavolt computed tomography (MVCT) images during the course of image-guided and stereotactic intensity-modulated radiotherapy (IGRT-IMRT) by use of helical tomotherapy. PATIENTS AND METHODS: A total of 25 lesions in 24 patients with vertebral metastases who received IGRT-IMRT were analyzed. MVCT images were acquired before and after radiation therapy. Intra-fractional movement and PTV margin were calculated by comparing treatment planning images and these 310 MVCT images for right-left (RL), superior-inferior (SI), and anteroposterior (AP) dimensions. Five patients were treated by 35 Gy/5 fractions, 17 by 30 Gy/5 fractions, one by 25 Gy/5 fractions, and one by 60 Gy/30 fractions. A margin to compensate for these variations was calculated with the formula of vanHerk's equation. RESULTS: The intra-fractional motion was 0.02 (-1.3 to 1.4) ± 0.34 mm in the RL direction, -0.09 (-1.8 to 0.28) ± 0.44 mm in the SI direction, and 0.20 (-1.8 to 1.8) ± 0.36 mm in the AP direction. The required PTV margin was 0.98 mm in the RL direction, 0.69 mm in the SI direction, and 1.26 mm in the AP direction. No patient showed a deviation greater than 2 mm. CONCLUSION: The PTV margin in hypofractionated IGRT-IMRT, using helical tomotherapy for a few vertebral metastases, was 2 mm or less and our tentative PTV margin of 5 mm was sufficient and reducible.

Comparison of calculated dose by helical tomotherapy treatment planning machine and measured dose of radiophotoluminescence glass dosimeter in lung lesions using Rando Phantom.

AIM: To examine the compatibility of the measured and calculated dose for the treatment of lung lesions by helical tomotherapy. MATERIALS AND METHODS: The administered dose was measured a total of 55 times at 22 points with a radiophotoluminescence glass dosimeter (RPLGD) inserted in the position of an anthropomorphic Rando Phantom. Two Gy were prescribed and calculated with a tomotherapy planning machine for a 3-cm diameter spherical planning target volume (PTV) created in the lung area. Compatibility (measured dose/calculated dose and σ value=(D(meas)-D(calc))/D(prescribed)) × 100 (%)) was analyzed according to dosimeter location. RESULTS: Deviations between measured and calculated doses for the lung lesion were within 4% for planning target volume, indicating that adequate dose delivery to the PTV was achievable. On the other hand, we found dose deviations up to 15% for the lower prescribed dose range (64% or less) for the measured dose/calculated comparison and a 6% deviation according to the σ value in or near inhomogeneous tissue. CONCLUSION: Although the measured dose satisfied the clinical requirement in almost all areas including PTV, we should note that there may be discrepancies between expected calculated dose and irradiated dose in or near inhomogeneous area.