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Biomedical subjects

G Magrin

Publications and source records attributed to G Magrin.

4 recordsLinked to original sources

Mini-TEPCs for radiation therapy.

A mini-tissue-equivalent proportional-counter (TEPC) has been constructed to study the possibility to manufacture mini-counters without field-shaping tubes for radiation therapy. The mini-TEPC can be assembled with and without field-shaping tubes. It can be equipped with a mini-alpha source for a precise lineal energy calibration. After the positive conclusions of this study, a slim TEPC has been designed and constructed. The slim TEPC has an external diameter of only 2.7 mm. It has been tested with therapeutic proton beams and gamma ray sources.

Equipment Design↗

Nanodosimetric measurements with an avalanche confinement TEPC.

This paper illustrates a tissue-equivalent proportional counter designed to have high gas gain and good energy resolution at nanometric simulated site sizes. Microdosimetric neutron and gamma spectra were measured in dimethyl ether and in propane-based tissue-equivalent gas mixture down to 35 nm. The comparison of experimental data with the results of Monte Carlo calculations shows a satisfactory agreement.

Dose-Response Relationship, Radiation↗

Microdosimetric analysis of radiation from a clinical mammography machine using realistic breast phantoms and a miniature proportional counter.

We have measured the microdosimetric spectra of a Senographe 600T mammography machine employing an Mo target with 0.8 mm Be inherent filtration and 0.03 mm Mo added filtration, giving a half-value layer of 0.35 mm A1 at 28 kVp. In all of our measurements a large collimator producing a 24 cm x 30 cm field at 65 cm was used. Two different phantom compositions differing in the ratio of adipose to fibroglandular tissue were compared, using simulated breast material from Nuclear Associates. Spectra were taken at various depths and locations in simulated breasts of 3.4 and 5 cm thickness. The detector used was a miniature proportional counter having outer dimensions of 5 cm x 1.8 cm diameter, with a sensitive volume 0.5 mm x 0.5 mm. The small dimensions of the counter and the cavity allowed total embedding in the breast material with minimal disturbance of the photon and secondary electron spectrum. Our results show that there can be changes in the radiation quality amounting to as much as 17% (as measured by the dose mean lineal energy. yD) between breasts of different thickness, at the same relative position within the breast. There is little difference due to breast composition.

Breast↗

Preoperative autologous blood donation. Linkage of the public and private hospital sectors.

OBJECTIVE: To evaluate the safety and efficacy of a preoperative autologous blood donation (PABD) program with liberal patient exclusion criteria. DESIGN: Prospective patient accrual from September 1990 to May 1992. SETTING: A PABD program in a public tertiary care hospital linked with a specialist orthopaedic practice in a private hospital. PATIENTS: One hundred and twenty patients consecutively scheduled for orthopaedic surgery were referred for PABD. There were 77 women (median age, 63 years) and 43 men (median age, 62 years). One-third of patients were 70 or more years old. Coexistent medical disease, mainly cardiovascular, was present in 46% of patients and 3% were excluded because of coexisting morbidity. Total hip or total knee replacement was performed in a private hospital with intraoperative or postoperative blood salvage in 37% of the patients. OUTCOME MEASURES: Adverse effects of PABD, autologous blood collected and used and homologous blood transfused. RESULTS: One hundred and sixteen patients donated 267 units of autologous blood. In 70 patients undergoing total hip replacement, 78% donated three and 20% donated two units, with 95% of autologous blood being used. In 38 patients undergoing total knee replacement, 42% donated two units and 55% donated one unit, with 87% of autologous blood being transfused. Seventy-eight per cent of all patients only received autologous blood. In the remaining patients, homologous blood use was confined to two units or less in 80%. Hypotensive episodes associated with phlebotomy occurred in 3% of patients, and 13% of patients had preoperative haemoglobin levels ranging from 85-100 g/L without adverse clinical effects. CONCLUSION: A hospital-based PABD program with less strict patient exclusion criteria does not prejudice the clinical status of the donors. Its linkage to private hospitals can significantly reduce the use of homologous blood in selected elective surgery.

Adult↗