Postsurgical geometrical variations of tumor bed and brainstem during photon and proton therapy for pediatric tumors of the posterior fossa: dosimetric impact and predictive factors.

PURPOSE: Brainstem radionecrosis is an important issue during the irradiation of tumors of the posterior fossa. The aim of the present study is to analyze postsurgical geometrical variations of tumor bed (TB) and brainstem (BS) and their impact on dosimetry. METHODS: Retrospective collection of data from pediatric patients treated at a single institution. Availability of presurgical magnetic resonance imaging (MRI) was verified; availability of at least two postsurgical MRIs was considered a further inclusion criterion. The following metrics were analyzed: total volume, Dice similarity coefficient (DSC), and Haudsdorff distances (HD). RESULTS: Fourteen patients were available for the quantification of major postsurgical geometrical variations of TB. DSC, HD max, and HD average values were 0.47 (range: 0.08;0.76), 11.3 mm (7.7;24.5), and 2.6 mm (0.7;6.7) between the first and the second postoperative MRI, respectively. Postsurgical geometrical variations of the BS were also observed. Coverage to the TB was reduced in one patient (D95: -2.9 Gy), while D2 to the BS was increased for the majority of patients. Overall, predictive factors for significant geometrical changes were presurgical gross tumor volume (GTV) > 33 mL, hydrocephaly at diagnosis, Luschka foramen involvement, and younger age (≤ 8 years). CONCLUSION: Major volume changes were observed in this cohort, with some dosimetric impact. The use of a recent co-registration MRI is advised. The 2-3 mm HD average observed should be considered in the planning target volume/planning organ at risk volume (PTV/PRV) margin and/or robust optimization planning. Results from wider efforts are needed to verify our findings.

Experience with the Implementation of Continuous Medical Education among Mother-and-Child Healthcare Providers in Ukraine: A Case Study Based on Two International Collaboration Initiatives.

BACKGROUND: Healthcare labor market shortages due to migration, inadequate investments, and lack of continuous training are essential concerns in the Eastern European region. This article aims to describe and reflect on the experience with the implementation of continuous medical education among mother-and-child healthcare providers in Ukraine, including achievements, challenges, and barriers. We analyze this case based on two international collaboration initiatives: the Swiss-Ukrainian program in mother-and-child health that ran from 2000 to 2015, supplemented by the recent Ukrainian-Swiss project "Medical education development" in 2018-2023. METHODS: We use a case study approach as the methodology for our study. We collected data from documents (project reports reviews) and in-depth interviews with stakeholders. We apply the method of directed qualitative content analysis. RESULTS: As a result of the Swiss-Ukrainian collaborations, the knowledge and awareness of medical personnel were greatly improved. Modern clinical concepts not well understood at the outset became commonplace and were incorporated into clinical activities. Nevertheless, obstacles to the implementation and rapid uptake of changes were found in the lack of knowledge of the English language among medical doctors, the fear of changes, and the lack of openness and readiness for novel evidence-based clinical practices. However, primary healthcare practitioners in this new project seem to be more inclined to change. CONCLUSIONS: A modernized continuous medical education which is based on the values of openness, respect, dialogue, and professionalism can be implemented with the input of an international assistance program despite the resistance of the system towards change.

Investigations towards incorporation of Eu3+ and Cm3+ during ZrO2 crystallization in aqueous solution.

Nuclear energy provides a widely applied carbon-reduced energy source. Following operation, the spent nuclear fuel (SNF), containing a mixture of radiotoxic elements such as transuranics, needs to be safely disposed of. Safe storage of SNF in a deep geological repository (DGR) relies on multiple engineered and natural retention barriers to prevent environmental contamination. In this context, zirconia (ZrO2) formed on the SNF rod cladding, could be employed as an engineered barrier for immobilization of radionuclides via structural incorporation. This study investigates the incorporation of Eu3+ and Cm3+, representatives for trivalent transuranics, into zirconia by co-precipitation and crystallization in aqueous solution at 80 °C. Complementary structural and microstructural characterization has been carried out by powder X-ray diffraction (PXRD), spectrum imaging analysis based on energy-dispersive X-ray spectroscopy in scanning transmission electron microscopy mode (STEM-EDXS), and luminescence spectroscopy. The results reveal the association of the dopants with the zirconia particles and elucidate the presence of distinct bulk and superficially incorporated species. Hydrothermal aging for up to 460 days in alkaline media points to great stability of these incorporated species after initial crystallization, with no indication of phase segregation or release of Eu3+ and Cm3+ over time. These results suggest that zirconia would be a suitable technical retention barrier for mobilized trivalent actinides in a DGR.

Survey of Anesthesia, Sedation, and Non-sedation Practices for Children Undergoing Repetitive Cranial or Craniospinal Radiotherapy.

Background Children undergoing cranial or craniospinal radiotherapy may require over 30 treatments within a six-week period. Facilitating these many treatments with the patient under anesthesia presents a significant challenge, and the most preferred anesthetic methods remain unknown. The primary goal of this study was to determine the most preferred anesthetic methods and agents for children undergoing daily cranial or craniospinal radiotherapy. Methods An 83-item web-based survey was developed. An introductory email was sent to 505 physicians and child-life specialists with expertise in pediatric anesthesia and/or affiliated with pediatric radiation oncology departments. Results The response rate was 128/505 (25%) and included specialists from Africa (5, 4%), Asia (18, 14%), Australia/Oceania (5, 4%), Europe (45, 35%), North America (50, 39%), and South America (5, 4%). The 128 respondents included 91 anesthesiologists (71%), 20 physicians who were not anesthesiologists (16%), 14 child life/social education specialists (11%), one radiotherapist, one pediatric radiation nurse, and one non-specified medical professional (all = 2%). Of the 128 respondents, 95 (74%) used anesthesia or sedation to facilitate repetitive cranial or craniospinal radiotherapy. Overall, total intravenous anesthesia without intubation was preferred by 67 of 95 (71%) specialists during one or more forms of radiotherapy. During photon-based radiotherapy, total intravenous anesthesia without intubation was the preferred anesthetic method with the patient in the supine (57/84, 68%) and prone positions (25/40, 63%). Propofol was the most used anesthetic agent for both supine (73/84, 87%) and prone positions (38/40, 95%). For proton radiotherapy, total intravenous anesthesia without intubation was the most preferred anesthetic method for the supine (32/42, 76%) and prone treatment positions (11/18, 61%), and propofol was the most used anesthetic (supine: 40/43, 93%; prone: 16/18, 89%). Conclusions In this survey of 95 specialists responsible for anesthesia or sedation of children undergoing repetitive cranial or craniospinal radiotherapy, propofol-based total intravenous anesthesia without intubation was the preferred anesthetic technique.

Early Toxicities After High Dose Rate Proton Therapy in Cancer Treatments.

BACKGROUND: The conventional dose rate of radiation therapy is 0.01-0.05 Gy per second. According to preclinical studies, an increased dose rate may offer similar anti-tumoral effect while dramatically improving normal tissue protection. This study aims at evaluating the early toxicities for patients irradiated with high dose rate pulsed proton therapy (PT). MATERIALS AND METHODS: A single institution retrospective chart review was performed for patients treated with high dose rate (10 Gy per second) pulsed proton therapy, from September 2016 to April 2020. This included both benign and malignant tumors with ≥3 months follow-up, evaluated for acute (≤2 months) and subacute (>2 months) toxicity after the completion of PT. RESULTS: There were 127 patients identified, with a median follow up of 14.8 months (3-42.9 months). The median age was 55 years (1.6-89). The cohort most commonly consisted of benign disease (55.1%), cranial targets (95.1%), and were treated with surgery prior to PT (56.7%). There was a median total PT dose of 56 Gy (30-74 Gy), dose per fraction of 2 Gy (1-3 Gy), and CTV size of 47.6 ml (5.6-2,106.1 ml). Maximum acute grade ≥2 toxicity were observed in 49 (38.6%) patients, of which 8 (6.3%) experienced grade 3 toxicity. No acute grade 4 or 5 toxicity was observed. Maximum subacute grade 2, 3, and 4 toxicity were discovered in 25 (19.7%), 12 (9.4%), and 1 (0.8%) patient(s), respectively. CONCLUSION: In this cohort, utilizing high dose rate proton therapy (10 Gy per second) did not result in a major decrease in acute and subacute toxicity. Longer follow-up and comparative studies with conventional dose rate are required to evaluate whether this approach offers a toxicity benefit.