Longitudinal Remote SBRT/SRS Training in Latin America: A Prospective Cohort Study.

Background: Continuing medical education in stereotactic technology are scarcely accessible in developing countries. We report the results of upscaling a longitudinal telehealth training course on stereotactic body radiation therapy (SBRT) and stereotactic radiosurgery (SRS), after successfully developing a pilot course in Latin America. Methods: Longitudinal training on SBRT and SRS was provided to radiation oncology practitioners in Peru and Colombia at no cost. The program included sixteen weekly 1-hour live conferencing sessions with interactive didactics and a cloud-based platform for case-based learning. Participant-reported confidence was measured in 16 SBRT/SRS practical domains, based on a 1-to-5 Likert scale. Pre- and post-curriculum exams were required for participation credit. Knowledge-baseline, pre- and post-curriculum surveys, overall and single professional-group confidence changes, and exam results were assessed. Results: One hundred and seventy-three radiotherapy professionals participated. An average of 56 (SD ±18) attendees per session were registered. Fifty (29.7%) participants completed the pre- and post-curriculum surveys, of which 30% were radiation oncologists (RO), 26% radiation therapists (RTT), 20% residents, 18% medical physicists and 6% neurosurgeons. Significant improvements were found across all 16 domains with overall mean +0.55 (SD ±0.17, p<0.001) Likert-scale points. Significant improvements in individual competences were most common among medical physicists, RTT and residents. Pre- and post-curriculum exams yielded a mean 16.15/30 (53.8 ± 20.3%) and 23.6/30 (78.7 ± 19.3%) correct answers (p<0.001). Conclusion: Longitudinal telehealth training is an effective method for improving confidence and knowledge on SBRT/SRS amongst professionals. Remote continuing medical education should be widely adopted in lower-middle income countries.

Dose simulations of an early 20th century kilovoltage pneumonia radiotherapy technique performed with a modern fluoroscope.

To simulate an early 20th century viral pneumonia radiotherapy treatment using modern fluoroscopy and evaluated it according to current dose guidelines. Monte Carlo was used to assess the dose distribution on an anthropomorphic phantom. Critical organs were: skin, breasts, esophagus, ribs, vertebrae, heart, thymus, and spinal cord. A 100 kVp beam with 3 mm Al HVL, 25 × 25 cm2 posterior-anterior (PA) field and 50 cm source-to-surface distance were simulated. Simulations had a resolution of 0.4 × 0.4 × 0.06 cm3 and a 6% uncertainty. Hundred percent dose was normalized to the skin surface and results were displayed in axial, coronal, and sagittal planes. Dose volume histograms were generated in MATLAB for further analysis. Prescription doses of 0.3, 0.5, and 1.0 Gy were applied to the 15% isodose for organ-dose comparison to current tolerances and potential risk of detriment. Ninety-five and ninety-seven percent of the right and left lung volumes, respectively, were well-covered by the 15% isodose line. For the 0.3, 0.5, and 1.0 Gy prescriptions, the maximum skin doses were 2.9, 4.8, and 9.6 Gy compared to a 2.0 Gy transient erythema dose threshold; left/right lung maximum doses were 1.44/1.46, 2.4/2.4, and 4.8/4.9 Gy compared to a 6.5 Gy pneumonitis and 30 Gy fibrosis thresholds; maximum heart doses were 0.5, 0.9, and 1.8 Gy compared to the 0.5 Gy ICRP-recommendation; maximum spinal cord doses were 1.4, 2.3, and 4.6 Gy compared to 7.0 Gy single fraction dose threshold. Maximum doses to other critical organs were below modern dose thresholds. A 100 kVp PA field could deliver a 0.3 Gy or 0.5 Gy dose without risk of complications. However, a 1.0 Gy dose treatment could be problematic. Critical organ doses could be further reduced if more than one treatment field is used.

Impact of High-Dose-Rate Brachytherapy Training via Telehealth in Low- and Middle-Income Countries.

PURPOSE: Our objective was to demonstrate the efficacy of a telehealth training course on high-dose-rate (HDR) brachytherapy for gynecologic cancer treatment for clinicians in low- and middle-income countries (LMICs). METHODS: A 12-week course consisting of 16 live video sessions was offered to 10 cancer centers in the Middle East, Africa, and Nepal. A total of 46 participants joined the course, and 22 participants, on average, attended each session. Radiation oncologists and medical physicists from 11 US and international institutions prepared and provided lectures for each topic covered in the course. Confidence surveys of 15 practical competencies were administered to participants before and after the course. Competencies focused on HDR commissioning, shielding, treatment planning, radiobiology, and applicators. Pre- and post-program surveys of provider confidence, measured by 5-point Likert scale, were administered and compared. RESULTS: Forty-six participants, including seven chief medical physicists, 16 senior medical physicists, five radiation oncologists, and three dosimetrists, representing nine countries attended education sessions. Reported confidence scores, both aggregate and paired, demonstrated increases in confidence in all 15 competencies. Post-curriculum score improvement was statistically significant (P < .05) for paired respondents in 11 of 15 domains. Absolute improvements were largest for confidence in applicator commissioning (2.3 to 3.8, P = .009), treatment planning system commissioning (2.2 to 3.9, P = .0055), and commissioning an HDR machine (2.2 to 4.0, P = .0031). Overall confidence in providing HDR brachytherapy services safely and teaching other providers increased from 3.1 to 3.8 and 3.0 to 3.5, respectively. CONCLUSION: A 12-week, low-cost telehealth training program on HDR brachytherapy improved confidence in treatment delivery and teaching for clinicians in 10 participating LMICs.

Impact of a SBRT/SRS longitudinal telehealth training pilot course in Latin America.

PURPOSE: To assess the impact of longitudinal telehealth training in stereotactic body radiation therapy (SBRT) and stereotactic radiosurgery (SRS) for clinicians in Latin America. MATERIALS AND METHODS: Professionals from two Peruvian centers received an initial SBRT/SRS on-site training course and subsequently received follow-up telehealth training (interventional group) or not (negative control arm). Twelve live video conference sessions were scheduled. Surveys pre- and post-curriculum measured participants' confidence in seven practical domains of SBRT/SRS, based on Likert scales of 1-5, and post-curriculum surveys assessed educators' experiences. RESULTS: Sixty-one participants were registered, with an average of 24 attendees per session. Pre- and post- surveys were completed by 22 participants. For interventional and negative-control groups, mean changes in Likert scale were satisfactory for the former and remained unmodified for the latter. CONCLUSIONS: Conducting telehealth educational programs via virtual classroom sessions could be a reliable method to augment training for SBRT and SRS.

Flattening filter free beam energy selection and its impact in multitarget intracranial stereotactic radiosurgery treatments.

Extensive work has been done on the characteristics, dosimetry, and efficacy of flattening filter free (FFF) beams in radiosurgery. However, no study has addressed the dosimetric impact of FFF beam energy selection on treatment plan quality. This study aims to present a systematic dosimetric comparison of plan quality between 10 FFF vs 6 FFF beams in intracranial stereotactic radiosurgery (SRS) treatments using volumetric modulated arc therapy (VMAT). The dosimetric evaluation is based on radiation therapy oncology group (RTOG) dose conformity (CIRTOG) and gradient (GIRTOG) indices, and irradiated normal brain tissue volume. Thirty-five VMAT-based intracranial SRS treatments to multiple brain metastases using a 2.5 mm multileaf collimator (MLC) and 10 MV FFF beam were replanned with a 6 MV FFF and same MLC. The replans incorporated the same arc arrangement, planning target volume (PTV) and organs at risk structures, PTV coverage and prescription isodose normalization. The 6 MV FFF had a sharper dose fall-off compared to the 10 MV FFF (GIRTOG-10 FFF = 4.70, GIRTOG-6 FFF = 4.56; p < 0.05) and comparable conformity index (CIRTOG-10 FFF = 1.11, CIRTOG-6 FFF = 1.10; p = 0.9). On average, the irradiated normal brain tissue volume was 11% lower with 6 MV FFF compared to 10 MV FFF (p < 0.05). However, this difference was diminished for large target volumes and increased number of targets treated. The main dosimetric improvement of a 6 MV FFF over a 10 MV FFF beam is the sharper dose fall-off which directly correlates with less normal brain tissue volume irradiation.

Defining functional changes in the brain caused by targeted stereotaxic radiosurgery.

Brain tumor patients routinely undergo cranial radiotherapy, and while beneficial, this treatment often results in debilitating cognitive dysfunction. This serious and unresolved problem has at present, no clinical recourse, and has driven our efforts to more clearly define the consequences of different brain irradiation paradigms on specific indices of cognitive performance and on the underlying cellular mechanisms believed to affect these processes. To accomplish this we have developed the capability to deliver highly focused X-ray beams to small and precisely defined volumes of the athymic rat brain, thereby providing more realistic simulations of clinical irradiation scenarios. Using this technique, termed stereotaxic radiosurgery, we evaluated the cognitive consequences of irradiation targeted to the hippocampus in one or both hemispheres of the brain, and compared that to whole brain irradiation. While whole brain irradiation was found to elicit significant deficits in novel place recognition and fear conditioning, standard platforms for quantifying hippocampal and non-hippocampal decrements, irradiation targeted to both hippocampi was only found to elicit deficits in fear conditioning. Cognitive decrements were more difficult to demonstrate in animals subjected to unilateral hippocampal ablation. Immunohistochemical staining for newly born immature (doublecortin positive) and mature (NeuN positive) neurons confirmed our capability to target irradiation to the neurogenic regions of the hippocampus. Stereotaxic radiosurgery (SRS) of the ipsilateral hemisphere reduced significantly the number of doublecortin and NeuN positive neurons by 80% and 27% respectively. Interestingly, neurogenesis on the contralateral side was upregulated in response to stereotaxic radiosurgery, where the number of doublecortin and NeuN positive neurons increased by 22% and 36% respectively. Neuroinflammation measured by immunostaining for activated microglia (ED1 positive cells) was significantly higher on the ipsilateral versus contralateral sides, as assessed throughout the various subfields of the hippocampus. These data suggest that certain cognitive decrements are linked to changes in neurogenesis, and that the unilaterally irradiated brain exhibits distinct neurogenic responses that may be regulated by regional differences in neuroinflammation. Compensatory upregulation of neurogenesis on the contralateral hemisphere may suffice to maintain cognition under certain dose limits. Our results demonstrate unique cognitive and neurogenic consequences as a result of targeted stereotaxic radiosurgery, and suggest that these irradiation paradigms elicit responses distinct from those found after exposing the whole brain to more uniform radiation fields.

The use of RapidArc volumetric-modulated arc therapy to deliver stereotactic radiosurgery and stereotactic body radiotherapy to intracranial and extracranial targets.

Twenty-three targets in 16 patients treated with stereotactic radiosurgery (SRS) or stereotactic body radiotherapy (SBRT) were analyzed in terms of dosimetric homogeneity, target conformity, organ-at-risk (OAR) sparing, monitor unit (MU) usage, and beam-on time per fraction using RapidArc volumetric-modulated arc therapy (VMAT) vs. multifield sliding-window intensity-modulated radiation therapy (IMRT). Patients underwent computed tomography simulation with site-specific immobilization. Magnetic resonance imaging fusion and optical tracking were incorporated as clinically indicated. Treatment planning was performed using Eclipse v8.6 to generate sliding-window IMRT and 1-arc and 2-arc RapidArc plans. Dosimetric parameters used for target analysis were RTOG conformity index (CI(RTOG)), homogeneity index (HI(RTOG)), inverse Paddick Conformity Index (PCI), D(mean) and D5-D95. OAR sparing was analyzed in terms of D(max) and D(mean). Treatment delivery was evaluated based on measured beam-on times delivered on a Varian Trilogy linear accelerator and recorded MU values. Dosimetric conformity, homogeneity, and OAR sparing were comparable between IMRT, 1-arc RapidArc and 2-arc RapidArc plans. Mean beam-on times ± SD for IMRT and 1-arc and 2-arc treatments were 10.5 ± 7.3, 2.6 ± 1.6, and 3.0 ± 1.1 minutes, respectively. Mean MUs were 3041, 1774, and 1676 for IMRT, 1-, and 2-arc plans, respectively. Although dosimetric conformity, homogeneity, and OAR sparing were similar between these techniques, SRS and SBRT fractions treated with RapidArc were delivered with substantially less beam-on time and fewer MUs than IMRT. The rapid delivery of SRS and SBRT with RapidArc improved workflow on the linac with these otherwise time-consuming treatments and limited the potential for intrafraction organ and patient motion, which can cause significant dosimetric errors. These clinically important advantages make image-guided RapidArc useful in the delivery of SRS and SBRT to intracranial and extracranial targets.

Stem cell transplantation strategies for the restoration of cognitive dysfunction caused by cranial radiotherapy.

Radiotherapy often provides the only clinical recourse for those afflicted with primary or metastatic brain tumors. While beneficial, cranial irradiation can induce a progressive and debilitating decline in cognition that may, in part, be caused by the depletion of neural stem cells. Given the increased survival of patients diagnosed with brain cancer, quality of life in terms of cognitive health has become an increasing concern, especially in the absence of any satisfactory long-term treatments. To address this serious health concern we have used stem cell replacement as a strategy to combat radiation-induced cognitive decline. Our model utilizes athymic nude rats subjected to cranial irradiation. The ionizing radiation is delivered as either whole brain or as a highly focused beam to the hippocampus via linear accelerator (LINAC) based stereotaxic radiosurgery. Two days following irradiation, human neural stem cells (hNSCs) were stereotaxically transplanted into the hippocampus. Rats were then assessed for changes in cognition, grafted cell survival and for the expression of differentiation-specific markers 1 and 4-months after irradiation. Our cognitive testing paradigms have demonstrated that animals engrafted with hNSCs exhibit significant improvements in cognitive function. Unbiased stereology reveals significant survival (10-40%) of the engrafted cells at 1 and 4-months after transplantation, dependent on the amount and type of cells grafted. Engrafted cells migrate extensively, differentiate along glial and neuronal lineages, and express a range of immature and mature phenotypic markers. Our data demonstrate direct cognitive benefits derived from engrafted human stem cells, suggesting that this procedure may one day afford a promising strategy for the long-term functional restoration of cognition in individuals subjected to cranial radiotherapy. To promote the dissemination of the critical procedures necessary to replicate and extend our studies, we have provided written and visual documentation of several key steps in our experimental plan, with an emphasis on stereotaxic radiosurgey and transplantation.

Dosimetric characteristics of the Novoste Beta-Cath 90Sr/Y source trains at submillimeter distances.

Measurements were performed on the 30, 40, and 60 mm 90Sr/Y beta-emitter source trains used in the Novoste Beta-Cath system to determine their dosimetric characteristics at submillimeter distances and provide the necessary TG-60 parameters for mapping their dose distributions. These measurements were carried out in a Solid Water phantom where MD55-2 Gafchromic films were placed in direct contact with a 5 French (F) catheter used for the 30 and 60 mm source trains and a 3.5F catheter used for thinner 30 and 40 mm source trains. A data set consisted of three pieces of Gafchromic film irradiated for periods of 1.5, 5, and 10 minutes, respectively. This 3-film irradiation technique provided reliable dose data at short, intermediate and long distances from a source train. Three data sets per source train were collected in this study. For the 30 mm source train with a 5F catheter, data were collected with the source axis at proximal (0.41 mm) and distal (1.19 mm) positions to the film surface in order to investigate dosimetric effects due to the off centering of the source train lumen within the catheter. Absolute doses were determined by calibrating the Gafchromic film in a high-energy electron beam from a radiotherapy accelerator. The absolute dose rates at a distance of 2 mm along the source trains transverse axis were found to be within 13.7% of the values provided by Novoste. Radial dose functions were within 13% compared to 90Sr/Y source train data constructed from Soares' 90Sr/Y single seed data and within 17% and 25% compared to Monte Carlo data by Ye et al., and Wang et al., respectively. Discrepancies of 33% and 19% were observed at short radial distances (< or = 1 mm) between the Novoste Monte Carlo and the 3.5F and 5F catheter measured data, respectively. The source off centering data showed higher dose contribution from the source train at its distal rather than proximal position. Radial dose function comparisons between the Novoste Monte Carlo and the measured data, calculated as a function of radial distance from the catheter's center showed good agreement (< or = 10%).

Búsqueda de hemoglobinas anormales en los recién nacidos en las grandes alturas / Search of abnormal hemoglobin in new borns at high altitude

Se hizo un muestreo para detectar hemoglobinas anormales en recién nacidos (RN) de tres ciudades andinas situadas en el Perú: Cerro de Pasco, Huancayo y Puno. Estas ciudades están en altitudes que fluctuan entre los 3500 a 4400 m. sobre el nivel del mar. Objetivo: Investigar la presencia, de hemoglobinas anormales en RN nativos de altura. Material y métodos: Participaron un total de 234 RN. Se obtuvieron muestras de sangre del talón que fueron inmediatamente hemolizadas y refrigeradas para luego ser analizadas mediante electroforesis de punto isoeléctrico y cromatografía líquida de alto rendimiento. resultados: Los resultados indicaron que los RN tenían perfil de hemoglonina normal (HB A/F). Conclusiones: En estas muestras, que corresponden a una evaluación piloto, no se detectó ninguna variante anormal de hemoglobina, ni hemoglobinas de migración rápida (HB H, Hb Bart's).