Dose Prescription to Isodose Lines in Static Multi-Beam Stereotactic Body Radiotherapy for Lung Tumors: Which Line Is Optimal?

This study investigated the appropriate dose prescription method in static multi-beam stereotactic body radiotherapy for lung tumors. Static multi-beam stereotactic body radiotherapy is a mainstream treatment in Japan. Based on the hypothesis that dose prescription to lower isodose lines may improve planning target volume dose coverage and decrease doses to organs at risk, we investigated changes in dose-volume histograms with prescription to various isodose lines for planning target volume in static multi-beam stereotactic body radiotherapy. In all treatment plans, 45 Gy in 4 fractions were prescribed to 95% of the planning target volume. By adjusting the leaf margins of each beam, various prescription isodose lines encompassing 95% volume of the planning target volume were generated. The prescription isodose lines investigated were 40, 50, 60, 70, 80 and 90% lines relative to the maximum dose of each planning target volume. The conformity index, homogeneity index, mean lung dose, and V5-V40 of the lung were evaluated. The dose was calculated by the adaptive convolve algorithm. The conformity index was lowest in the 70% or 80% isodose plan. The mean lung doses and V10-V40 of the lung decreased steeply from the 90% to the 70% isodose plan, and was lowest in the 60% and 70% isodose plans. These indices increased in the 40% and 50% isodose plans. The optimal stereotactic body radiotherapy plans appeared to be dose prescription to the 60% or 70% isodose line. Further investigation is warranted to clarify the advantage of using this method clinically.

A Hydrogen-Free Approach for Activating an Fe Catalyst Using Trace Amounts of Noble Metals and Confinement into Nanoparticles.

Metallic iron (Fe) represents an exceptionally active catalyst, as shown in its use in the Haber-Bosch process to dissociate nitrogen molecules; however, the ease of corrosion by oxidation limits its usage. Hence, in most applications using metallic Fe catalysts, hydrogen is a necessary reactant. We report a novel hydrogen-free approach to fabricating reduced, highly active, and corrosion-resistive Fe-based catalysts using trace levels of noble metals (NMs) such as Ir, Rh, and Pt confined in the nanoparticle (NP). X-ray photoelectron spectroscopy (XPS) revealed that as little as ∼0.3 atom % was sufficient to induce the reduction of Fe. Extensive XPS analysis showed that the reduced NM atoms segregated to the NP surface and reduced the surrounding Fe atoms. We demonstrated the catalytic activity of the nanoparticles by the efficient synthesis of submillimeter tall, vertically aligned, and mainly double-walled carbon nanotube arrays using a completely hydrogen-free chemical vapor deposition process.

Occurrence and disease burden of respiratory syncytial virus and other respiratory pathogens in adults aged ≥65 years in community: A prospective cohort study in Japan.

BACKGROUND: The frequency and clinical profile of respiratory syncytial virus (RSV)-acute respiratory disease (ARD) in older adults in Japan has not been well-characterized. METHODS: This was a multicenter prospective observational cohort study to evaluate the occurrence rate of ARD in 1000 older adult participants (≥65 years) for 52 weeks during the 2019 to 2020 season. A multiplex polymerase chain reaction panel was used for pathogen detection in nasopharyngeal swab from participants diagnosed with ARD. Symptoms and impact of ARD was assessed using the Respiratory Infection Intensity and Impact Questionnaire (RiiQ™). The study was registered at UMIN (https://www.umin.ac.jp/ctr/): UMIN000037891. RESULTS: RSV-ARD was detected in 24/1000 (2.4%) participants and RSV-lower respiratory tract disease in 8/1000 (0.8%) participants. The median duration of RSV-ARD was 18 days. All 24 participants had utilized the medical services of outpatient visits and only 1 (4.2%) participant was hospitalized for RSV-ARD. The most common viruses other than RSV that caused ARD (detected in >10 participants) were human rhinovirus/enterovirus, parainfluenza 3, coronavirus OC43, human metapneumovirus, and influenza A/H1. The most frequent symptoms of RSV-ARD were cough, sore throat, nasal congestion, and expectoration. CONCLUSIONS: RSV was reported as a major pathogen for respiratory infections in older adults in Japan.

Feasibility of transrectal and transperineal fiducial marker placement for prostate cancer before proton therapy.

BACKGROUND: To compare the feasibility of transrectal and transperineal fiducial marker placement for prostate cancer before proton therapy. MATERIALS AND METHODS: From 2013 to 2015, the first 40 prostate cancer patients that were scheduled for proton therapy underwent transrectal fiducial marker placement, and the next 40 patients underwent transperineal fiducial marker placement (the first series). Technical and clinical success and pain scores were evaluated. In the second series (n = 280), the transrectal or transperineal approach was selected depending on the presence/absence of comorbidities, such as blood coagulation abnormalities. Seven patients refused to undergo the procedure. Thus, the total number of patients across both series was 353 (262 and 91 underwent the transrectal and transperineal approach, respectively). Technical and clinical success, complications, marker migration and the distance between the two markers were evaluated. RESULTS: In the first series, the technical and clinical success rates were 100% in both groups. The transrectal group exhibited lower pain scores than the transperineal group. The overall technical success rates of the transrectal and transperineal groups were 100% (262/262) and 99% (90/91), respectively (P > 0.05). The overall clinical success rate was 100% in both groups, and there were no major complications in either group. The migration rates of the two groups did not differ significantly. The mean distance between the two markers was 25.6 ± 7.1 mm (mean ± standard deviation) in the transrectal group and 31.9 ± 5.2 mm in the transperineal group (P < 0.05). CONCLUSION: Both the transrectal and transperineal fiducial marker placement methods are feasible and safe.

Proton therapy for non-squamous cell carcinoma of the head and neck: planning comparison and toxicity.

To investigate optimal treatment planning using proton beams for non-squamous cell carcinoma of the head and neck (NSCHN), the dose distributions of plans involving pencil beam scanning (PBS) with or without a patient-specific aperture system (PSAS), passive-scattering proton therapy (PSPT) and X-ray intensity-modulated radiotherapy (IMRT) were compared. As clinical results, toxicities of PBS with PSAS, including changes in quality of life, were reported. Between April 2014 and August 2016, a total of 30 patients were treated using PBS with PSAS. In 20 patients selected at random, the dose distributions of PBS with or without the PSAS, PSPT and IMRT plans were compared. Neutron exposure by proton therapy was calculated using a Monte Carlo simulation. Toxicities were scored according to CTCAE ver. 4.0. Patients completed EORTC quality of life survey forms (QLQ-C30 and QLQ-HN35) before and 0-12 months after proton therapy. The 95% conformity number of PBS with the PSAS plan was the best, and significant differences were detected among the four plans (P < 0.05, Bonferroni tests). Neutron generation by PSAS was ~1.1-fold higher, but was within an acceptable level. No grade 3 or higher acute dermatitis was observed. Pain, appetite loss and increased weight loss were more likely at the end of treatment, but recovered by the 3 month follow-up and returned to the pretreatment level at the 12 month follow-up. PBS with PSAS reduced the penumbra and improved dose conformity in the planning target volume. PBS with PSAS was tolerated well for NSCHN.

Effects of audio coaching and visual feedback on the stability of respiration during radiotherapy.

PURPOSE: The aim of this study is to compare the respiration-stabilizing abilities of audio coaching (AC) and AC with visual feedback (VF) with that of free breathing (FB). MATERIALS AND METHODS: Ten healthy volunteers were told to breathe in FB, under AC and under AC + VF in random order. The standard deviation (SD) values of the respiratory cycle, the amplitude, the lowest points (exhalation), and the highest points (inhalation) of respiratory wave were used as indices of respiratory stability. RESULTS: Compared with FB, the AC method significantly improved respiratory cycle stability (p = 0.001). The AC + VF method improved the stability of the respiratory cycle, the amplitude and the lowest point of respiratory wave (all p < 0.001). In analyses of each subject's data, compared with FB, the AC method significantly improved the respiratory cycle stability in five subjects, and the AC + VF method improved the stability of the respiratory cycle, the amplitude and the lowest point of respiratory wave in 4, 5, and 4 subjects, respectively. In two cases, coaching did not improve respiratory stability. CONCLUSION: The AC + VF method had the most beneficial effects on respiratory stability. However, coaching is not necessarily effective in all cases. Therefore, the most suitable method should be chosen on an individual basis.

Spot Scanning and Passive Scattering Proton Therapy: Relative Biological Effectiveness and Oxygen Enhancement Ratio in Cultured Cells.

PURPOSE: To determine the relative biological effectiveness (RBE), oxygen enhancement ratio (OER), and contribution of the indirect effect of spot scanning proton beams, passive scattering proton beams, or both in cultured cells in comparison with clinically used photons. METHODS AND MATERIALS: The RBE of passive scattering proton beams at the center of the spread-out Bragg peak (SOBP) was determined from dose-survival curves in 4 cell lines using 6-MV X rays as controls. Survival of 2 cell lines after spot scanning and passive scattering proton irradiation was then compared. Biological effects at the distal end region of the SOBP were also investigated. The OER of passive scattering proton beams and 6 MX X rays were investigated in 2 cell lines. The RBE and OER values were estimated at a 10% cell survival level. The maximum degree of protection of radiation effects by dimethyl sulfoxide was determined to estimate the contribution of the indirect effect against DNA damage. All experiments comparing protons and X rays were made under the same biological conditions. RESULTS: The RBE values of passive scattering proton beams in the 4 cell lines examined were 1.01 to 1.22 (average, 1.14) and were almost identical to those of spot scanning beams. Biological effects increased at the distal end of the SOBP. In the 2 cell lines examined, the OER was 2.74 (95% confidence interval, 2.56-2.80) and 3.08 (2.84-3.11), respectively, for X rays, and 2.39 (2.38-2.43) and 2.72 (2.69-2.75), respectively, for protons (P<.05 for both cells between X rays and protons). The maximum degree of protection was significantly higher for X rays than for proton beams (P<.05). CONCLUSIONS: The RBE values of spot scanning and passive scattering proton beams were almost identical. The OER was lower for protons than for X rays. The lower contribution of the indirect effect may partly account for the lower OER of protons.

A phenomenological model for selective growth of semiconducting single-walled carbon nanotubes based on catalyst deactivation.

A method for the selective semiconducting single-walled carbon nanotube (SWCNT) growth over a continuous range from 67% to 98%, within the diameter range of 0.8-1.2 nm, by the use of a "catalyst conditioning process" prior to growth is reported. Continuous control revealed an inverse relationship between the selectivity and the yield as evidenced by a 1000-times difference in yield between the highest selectivity and non-selectivity. Further, these results show that the selectivity is highly sensitive to the presence of a precise concentration of oxidative and reductive gases (i.e. water and hydrogen), and the highest selectivity occurred along the border between the conditions suitable for high yield and no-growth. Through these results, a phenomenological model has been constructed to explain the inverse relationship between yield and selectivity based on catalyst deactivation. We believe our model to be general, as the fundamental mechanisms limiting selective semiconducting SWCNT growth are common to the previous reports of limited yield.