Low-dose radiotherapy to the lungs using an interventional radiology C-arm fluoroscope: Monte Carlo treatment planning and dose measurements in a postmortem subject.

Objective.The goal of this study was to use Monte Carlo (MC) simulations and measurements to investigate the dosimetric suitability of an interventional radiology (IR) c-arm fluoroscope to deliver low-dose radiotherapy to the lungs.Approach.A previously-validated MC model of an IR fluoroscope was used to calculate the dose distributions in a COVID-19-infected patient, 20 non-infected patients of varying sizes, and a postmortem subject. Dose distributions for PA, AP/PA, 3-field and 4-field treatments irradiating 95% of the lungs to a 0.5 Gy dose were calculated. An algorithm was created to calculate skin entrance dose as a function of patient thickness for treatment planning purposes. Treatments were experimentally validated in a postmortem subject by using implanted dosimeters to capture organ doses.Main results.Mean doses to the left/right lungs for the COVID-19 CT data were 1.2/1.3 Gy, 0.8/0.9 Gy, 0.8/0.8 Gy and 0.6/0.6 Gy for the PA, AP/PA, 3-field, and 4-field configurations, respectively. Skin dose toxicity was the highest probability for the PA and lowest for the 4-field configuration. Dose to the heart slightly exceeded the ICRP tolerance; all other organ doses were below published tolerances. The AP/PA configuration provided the best fit for entrance skin dose as a function of patient thickness (R2 = 0.8). The average dose difference between simulation and measurement in the postmortem subject was 5%.Significance.An IR fluoroscope should be capable of delivering low-dose radiotherapy to the lungs with tolerable collateral dose to nearby organs.

Monte Carlo simulations and phantom validation of low-dose radiotherapy to the lungs using an interventional radiology C-arm fluoroscope.

PURPOSE: To use MC simulations and phantom measurements to investigate the dosimetry of a kilovoltage x-ray beam from an IR fluoroscope to deliver low-dose (0.3-1.0 Gy) radiotherapy to the lungs. MATERIALS AND METHODS: PENELOPE was used to model a 125 kV, 5.94 mm Al HVL x-ray beam produced by a fluoroscope. The model was validated through depth-dose, in-plane/cross-plane profiles and absorbed dose at 2.5-, 5.1-, 10.2- and 15.2-cm depths against the measured beam in an acrylic phantom. CT images of an anthropomorphic phantom thorax/lungs were used to simulate 0.5 Gy dose distributions for PA, AP/PA, 3-field and 4-field treatments. DVHs were generated to assess the dose to the lungs and nearby organs. Gafchromic film was used to measure doses in the phantom exposed to PA and 4-field treatments, and compared to the MC simulations. RESULTS: Depth-dose and profile results were within 3.2% and 7.8% of the MC data uncertainty, respectively, while dose gamma analysis ranged from 0.7 to 1.0. Mean dose to the lungs were 1.1-, 0.8-, 0.9-, and 0.8- Gy for the PA, AP/PA, 3-field, and 4-field after isodose normalization to cover âˆ¼ 95% of each lung volume. Skin dose toxicity was highest for the PA and lowest for the 4-field, and both arrangements successfully delivered the treatment on the phantom. However, the dose distribution for the PA was highly non-uniform and produced skin doses up to 4 Gy. The dose distribution for the 4-field produced a uniform 0.6 Gy dose throughout the lungs, with a maximum dose of 0.73 Gy. The average percent difference between experimental and Monte Carlo values were -0.1% (range -3% to +4%) for the PA treatment and 0.3% (range -10.3% to +15.2%) for the 4-field treatment. CONCLUSION: A 125 kV x-ray beam from an IR fluoroscope delivered through two or more fields can deliver an effective low-dose radiotherapy treatment to the lungs. The 4-field arrangement not only provides an effective treatment, but also significant dose sparing to healthy organs, including skin, compared to the PA treatment. Use of fluoroscopy appears to be a viable alternative to megavoltage radiation therapy equipment for delivering low-dose radiotherapy to the lungs.

SU-E-T-271: Irradiating a Single Hippocampus in a Small Rodent Using VMAT- RapidArc SRS: Preliminary Data.

PURPOSE: To develop and optimize the procedures for the precise irradiation of the hippocampal region in a rodent with minimum radiation dose to the remainder of the brain. For this purpose, VMAT-RapidArc SRS was used to irradiate one hippocampus of athymic nude (ATN) rats. Prescribed dose was verified through TLD measurements and spared brain region(s) were confirmed through immunohistochemical analysis postmortem. METHODS: Seven ATN rats, 10-12 weeks old underwent human-like radiation treatment planning followed by SRS. MRI and CT axial images of 0.8 mm thickness of the rat's skull were acquired and transferred to ECLIPSE treatment planning software where brain, right and left hippocampi were contoured. A VMAT-RapidArc plan consisting of two 3600 axial arcs and two 1200 vertex arcs irradiated the left hippocampus only to a dose of 10 Gy. Treatment was delivered using a 6 MV photon beam from a Trilogy Linac equipped with OBI. TLD measurements were performed prior to treatment using a custom made phantom that simulated the rat's brain and body. Orthogonal x-ray images taken with the OBI and co-registered to DRR images were used to adjust the rat's treatment position. One month post- irradiation, rats were sacrificed and brain dissection was performed to verify the radiation effects in the targeted and non-targeted regions. RESULTS: Percent differences between calculated and measured dose were ∼12% which was expected due to the small field sizes (<2cm) used. Immunohistochemistry analysis revealed a significant reduction in cell population in the ipsilateral hippocampus while cell populations comparable to those in a non-irradiated subject were observed in the contralateral hippocampal region. CONCLUSIONS: Present results demonstrate that precise irradiation of small volumes within a rat's brain can be achieved with human-like image-guided VMAT-RapidArc treatment. Postmortem analysis of the rat brain provides evidence of high-precision targeted radiation damage and dose sparing.

SU-E-J-108: Quantitative Analysis of Longitudinal Cognitive Impairment Due to Radiation Therapy Based on Automatic Segmentation of Hippocampus and Subcortical Structure.

PURPOSE: In this study, we developed a quantitative analysis tool based on patient's longitudinal MR images to 1) measure the radiation dose received by each subcortical structure, 2) follow the change of volume and shape of each structure longitudinally. This tool provides a systematic approach to study the radiation therapy (and subsequent chemotherapy) associated with cognitive impairments. METHODS: MRI scans of one patient taken before and after radiation therapy are demonstrated in this study. 3D Conformal radiation therapy was performed on RapidArc™. An open source MRI analysis tool, FMRIB's Integrated Registration and Segmentation Tool (FIRST), was used for segmentation. The images are registered to a standard template with expert-defined labeling for all sub-cortical structures, and the labeling of each structure is mapped back to the individual MRI space for segmentation. After the segmentation, the radiation dose map was coregistered to the MRI space to calculate the dose received by each structure. RESULTS: For the structure that is contained within the radiation zone, we can calculate the total dose based on the volumetric distribution of radiation dose. For the structure that is outside the radiation field, we can calculate the distance from the radiation zone. We have demonstrated in this work that the analysis can be done for all segmented sub-cortical structures. The change of volume before and after radiation treatment can be analyzed, and the results can be correlated with the change of cognitive performance over time. CONCLUSIONS: We presented an automated tool for efficient, quantitative and user-independent measurements of radiation dose in subcortical structures. The obtained results can be correlated with the cognitive test score and the clinical outcome to evaluate radiation and the subsequent chemotherapy induced changes in brain structures and functions.

A randomized, controlled, double-blind study of light emitting diode photomodulation for the prevention of radiation dermatitis in patients with breast cancer.

BACKGROUND AND OBJECTIVES: Radiation dermatitis occurs in a majority of patients with breast cancer who receive radiation therapy (RT), causes significant pain, and may necessitate treatment delay. Light emitting diode (LED) photomodulation has been reported to minimize radiation dermatitis. This study sought to further evaluate the efficacy of LED photomodulation in lessening radiation dermatitis. MATERIALS & METHODS: After surgery, patients with breast cancer received LED photomodulation or sham treatments in conjunction with three-dimensional conformal RT. Reactions were evaluated using standardized photographs graded according to National Cancer Institute criteria. RESULTS: In the LED treatment group (n=18), no patients had grade 0 reactions, six (33.3%) had grade 1 reactions, 12 (66.7%) had grade 2 reactions, and none had a grade 3 reaction. In the sham treatment group (n=15), one (6.6%) patient had a grade 0 reaction, four (26.7%) had grade 1 reactions, 9 (60.0%) had grade 2 reactions, and one (6.7%) had a grade 3 reaction. Two (11.1%) patients in the LED treatment group and one (6.7%) in the control group had to interrupt treatment. Differences between groups were not statistically significant. CONCLUSION: LED photomodulation did not reduce the incidence of radiation-induced skin reactions or interruptions in therapy. .

Application of Gafchromic film in the dosimetry of an intravascular brachytherapy source.

The methodology of brachytherapy source dosimetry with Gafchromic MD 55-2 film (ISP Technologies, Inc.) is examined with an emphasis on the nonlinearity of the optical density-dose relation within the dynamic dose range, the radial distance-dependent measurement uncertainty, and the format of data presentation. The specific source chosen for this study was a Checkmate (Cordis Corporation) intravascular brachytherapy system. The two-dimensional dose distribution around the source was characterized by a comprehensive analysis of measurement uncertainties. A comparative analysis of the dosimetric data from the vendor and from the scientific literature showed a substantial consistency of the information available for the Checkmate source. Our two-dimensional dosimetric data for the Checkmate source trains is presented in the form of measured along and away dose tables.

Doença dita ocupacional, doenças do trabalho

A finalidade deste artigo é pensar sobre a posição do trabalhador, em sua condição de sujeito, diante do trabalho e do empregador, uma vez que nenhum outro momento da nossa história houve tantas reclamações trabalhista, reivindicações de indenização por invalidez e pedidos de aposentadorias. A LER/Dort e o stress representam hoje a grande dor do trabalhador. A questão é investigar que sujeito é esse, que aparentemente se deixa mutilar pelo outro e que ao mesmo tempo goza com um rótulo de incapaz e até mesmo de inválido. A análise decorre de como o sujeito se constitiu, dos paradigmas da atualidade, de como pode o trabalhador conciliar desejo, demando social e forças repressoras do ego e do que de si não pode ser mostrado, necessitando vir à tona de uma outra maneira. Seja como for, não seria equivocado apontar a existência de um sujeito que necessita colocar-se em primeiro lugar diante de si próprio e, para isso, precisa encontrar um lugar de escuta para a sua dor (AU)

Measured TG-60 dosimetric parameters of the Novoste Beta-Cath 90Sr/Y source trains for intravascular brachytherapy.

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 the dosimetric characteristics of the sources at millimeter distances and provide the necessary TG-60 dosimetry parameters for mapping the dose distributions. These measurements were carried out in a Solid Water phantom where MD-55-2 Gafchromic films were placed in direct contact with a 5 French (F) catheter used for the 30 and 60-mm source trains and a 3.5 F catheter used for a thinner 40-mm source train. The dosimetric analysis was performed according to the AAPM TG-60 formalism. For the 30-mm source train, data were collected with the source axis at distances of 0.41 and 1.19 mm from the film surface, respectively, in order to investigate possible dosimetric effects due to the intrinsic off centering of the source train lumen within the 5 F catheter. Absolute dose rates at 2 mm were determined by calibrating the radiochromic film in a high energy electron beam from a radiotherapy accelerator. The dose rates at a radial distance of 2 mm were found to be within 10% of the values provided by Novoste. Radial dose functions from this study were in good agreement (< or = 10%) with a 30-mm, 90Sr/Y source train dose data generated from C. G. Soares et al. 90Sr/Y single seed data. However, larger differences were observed at distances shorter than 1 mm when compared to radial dose functions from the Novoste Monte Carlo data.

Hydroxyurea-induced oxidative damage of normal and sickle cell hemoglobins in vitro: amelioration by radical scavengers.

Hydroxyurea (HU) induces fetal hemoglobin (Hb F) production in patients with sickle cell anemia. The therapeutic dosage of HU used for Hb F induction often elicits myelosuppression, which becomes its major associated complication. We examined the effect of HU on hemoglobin modulation and the role of radical scavengers on these induced changes. In vitro exposure of human blood to various concentrations of HU at predetermined time intervals induced a progressive dose-dependent oxidation (MetHb formation) of both adult (Hb AA) and sickle (Hb SS) hemoglobins. The oxidative effect of HU on Hb SS was 3 times greater than its effect on Hb AA. Similar but less profound changes were observed in H2O2-treated samples. Hb F was, however, observed to be relatively resistant to HU-induced oxidative damage. A substantial protective effect of Hb by alpha-tocopherol, ascorbic acid, and D-mannitol was observed during pretreatment of Hb AA and Hb SS blood samples. Analyses of the hemoglobins and their globin chain components by high-performance liquid chromatography revealed a considerable protective effect by these free radical scavengers. These results indicate that the HU-induced damage of hemoglobin and their component globin chains can be reduced by radical scavengers.

Microvascular transplantation of a free omental graft to the distal extremity in dogs.

OBJECTIVE: To assess the survival of a free omental graft applied to an experimentally created wound on the distal extremity in dogs. STUDY DESIGN: A free omental graft was evaluated as a primary method of treatment for dogs with distal extremity wounds in an experimental model. ANIMALS OR SAMPLE POPULATION: Five adult intact female mixed breed dogs weighing 21.8 kg to 25.0 kg. METHODS: A free omental graft was harvested from the abdomen and transferred to a wound bed overlying the medial aspect of the tibia. A microvascular anastomosis was performed between the graft vessels and vessels at the recipient site. Daily clinical assessment of graft viability was performed. Angiography and 99mTechnetium labeled macroaggregated albumin (99mTc MAA) scintigraphic perfusion scans were performed on either day 4, 5, or 7. Postmortem collection of tissues for histopathologic analysis was performed immediately after imaging. Total operative time and graft ischemia time were evaluated for effects on graft survival. RESULTS: Two of seven grafts survived to the end of the study, three of seven grafts failed because of ischemia, and two of seven grafts failed because of self-trauma. There was no clinically significant morbidity associated with the abdominal portion of the procedure. Because of the small number of surviving grafts, the effects of operative time and graft ischemia time could not be statistically evaluated. CONCLUSIONS: Microvascular transplantation of a free omental graft can result in a viable tissue covering of a distal extremity wound, however, the failure rate is unacceptably high. CLINICAL RELEVANCE: A free omental graft may not have sufficient durability to be an acceptable wound covering by itself. Further studies combining omentum with a skin graft or other tissues may result in a clinically useful technique.

Hydroxyurea-induced denaturation of normal and sickle cell hemoglobins in vitro.

Use of hydroxyurea (HU) to treat sickle cell disease is usually associated with increments in fetal hemoglobin (Hb F) production; however, in vitro studies show that HU may also induce hemoglobin denaturation. Whole blood samples from Hb AA, Hb AS, and Hb SS patients were treated in vitro with 100, 150, 200, 250, and 300 micrograms/mL HU, incubated at 30 degrees C for up to 12 days, and analyzed by high-performance liquid chromatography (HPLC). Hb AA levels show decrements of 91 to 14% with 100 micrograms/mL and 89 to 4% with 150 micrograms/mL after 12 days; 86 to 2% with 200 micrograms/mL after 10 days; 86 to 8% with 250 and 300 micrograms/mL after 8 days. Similar treatment and incubation times for Hb AS whole blood demonstrate that HU equally degrades the A and S components of Hb AS. A comparable approach for Hb SS whole blood samples, using a 300 micrograms/mL HU treatment, showed a hemoglobin denaturing pattern that went from 93% to 1% after 12 days. Globin chain analysis of these samples by reverse-phase HPLC showed that the denaturing effects occur mostly on the beta-globin chain.

Reference ranges for hemoglobin variants by HPLC in African Americans.

High performance liquid chromatography (HPLC) demonstrated advantages over conventional procedures employed in newborn and adult hemoglobinopathy screening programs for the identification of Hb variants has promoted the need to reassess our knowledge of hemoglobin reference ranges as it relates to HPLC quantitation. In this study, the HPLC hemoglobin reference ranges derived from 200 normal African American adults are expressed as follows: Hb A mean 93.6 percent (s.d. 1.3, ranges 89.8 to 95.2), Hb A1 mean 2.0 percent (s.d. 0.6, ranges 0.8 to 5.2), Hb F mean 3.2 percent (s.d. 0.7, ranges 1.7 to 5.3) and Hb A2 mean 1.2 percent (s.d. 0.4, ranges 0.5 to 3.4); while the HPLC results for normal newborns and babies (n = 99) in the African American population fluctuates from Hb F mean 82.0 percent (s.d. 7.7, range 66.6 to 89.9) and Hb A mean 19.0 percent (s.d. 7.7, ranges 10.1 to 33.4) at 4 days to a mean of 15. percent (s.d. 4.8, range 9.3 to 22.8) for Hb F and a mean of 85.0 percent (s.d. 5.1, ranges 76.4 to 90.7) for Hb A at 300 days after birth. In case of the most common hemoglobin variants for this population, it has been shown that the A/S and A/C ratios for adults (Hb AS, Hb AC) and newborns (Hb FAS, and FAC) remained within the 1.5 (range 1.0 to 2.2) limits regardless of age group. Application of these HPLC ranges to confront other abnormalities will prove most useful during blood screening processes.

Carcinoma de nasofaringe radioterapia sola Vs. radioterapia y poliquimioterapia / Nasapharyngeal carcinoma: only radiotherapy vs. radiotherapy and polychemotherapy

Comparar el curso clínico de los grupos de pacientes tratados con radioterapia externa Vs. radioterapia externa poliquimioterapia. Diseño: Análisis retrospectivo de una serie de casos durante 30 años. Lugar: servicios de radioterapia y de cabeza y cuello en centro hospitalario de referencia nacional. Muestra: 29 pacientes con carcinoma de nasofaringe demostrado histológicamente por rinoscopia posterior y biopsia. Intervenciones: radioterapia externa área de nasofaringe y cuello inferior en 12 casos (Rt sola) y radioterapia externa más poliquimioterapia en 17 casos (Rt + Qt). Resultados: Respuesta completa (R.C.) Rt sola 50 por ciento Vs. Rt. más Qt. 70,59 por ciento p<0,001, enfermedad residual (E.R.) Rt. sola 50 por ciento Vs. Rt. más Qt. 29.4 por ciento p<0.025. Periodo libre de enfermedad residual activa (P.L.E.R.A.) Rt. sola X: 2,17 ñ 1,72 D.E. meses Vs. Rt. + Qt.x:6,2 ñ 3,42 D.E. meses p<0,05. Sobrevida libre de enfermedad a 5 años (S.L.E.) Rt. sola x: 64,83 ñ -49,99 D.E. meses Vs. Rt. + Qt. x: 30,92 +- 21,75 D.E. meses p > 0,25. Complicaciones: Mayor incidencia con Rt.+ Qt. Conclusiones: El tratamiento del carcinoma de nasofaringe con Rt. sola Vs. Rt. + Qt. mejoró la tasa de R.C. y por consiguiente disminuyó la tasa de E.R., además frenó el avance de esta última por un período de tiempo más prolongado (P.L.E.R.A.) p< 0,05 (estadísticamente significativa), es decir que logró mayor control local de la enfermedad; por el contrario el tratamiento con Rt. + Qt. no logró mejorar el P.L.E., ni las proporciones de S.L.E. y de S.G. a 5 años en comparación con la Rt. sola, además tuvo un mayor número de complicaciones, lo cual nos permite recomendar el uso del tratamiento combinado (Rt. + Qt.) en forma sistemática y rutinaria