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Biomedical subjects

A Bridier

Publications and source records attributed to A Bridier.

14 recordsLinked to original sources
PubMed1992

Influence of shielding blocks on the output of photon beams as a function of energy and type of treatment unit.

The influence of field-defining shielding blocks on the output of a cobalt unit and of seven different accelerators (one with dual energy output) has been investigated. The quality indices range from 0.57 (cobalt-60) to 0.79. The loss in output due to shielding blocks has been calculated taking into account loss in phantom scatter only. Comparison with experimental results shows that the calculation algorithm is correct in most of the clinical conditions. However, for quality indices of 0.70 and higher, for blocks close to the central beam axis, an overestimation of the output by the algorithm has been found. The maximum deviation observed is about 5% for the highest energy and for block positions corresponding to those applied, e.g. for inverted Y-fields with narrow lumbo-aortic block spacing.

Algorithms↗
PubMed1990

Dosimetry for total body irradiation.

Basic dosimetry as well as patient dosimetry are considered. The following items concerning the basic beam dosimetry are discussed: dosimetry calibration, phantom material, beam quality and depth dose measurements in TBI conditions. Dose to the patient should be specified to the midplane of the abdomen but dose to the lung should be estimated for each patient. In vivo, dosimetry is strongly recommended for determination of dose homogeneity, as well as to check patient position, reproducibility of treatment and instabilities in dose rate during TBI. Many physical problems are associated with in vivo dosimetry. All influences on the detector response have to be considered and the detectors must be calibrated for TBI conditions.

Absorption↗
PubMed1987

Prospective comparison of ultrasound and computed tomography in the evaluation of the size of the uterus: can these methods be used for intracavitary treatment planning of carcinoma of the uterus?

A prospective evaluation of computed tomography and ultrasound was performed on 34 patients with Stage I and II endometrial carcinoma. All patients underwent immediate surgery following intracavitary treatment directed to vaginal mucosa. Pathologic measurements of the uterus were compared to those obtained by imaging technologies. The results of the study suggest that all but height measurements were rather accurately determined by both ultrasound and CT scan. However ultrasound was significantly better in determining the size of the cervix. Therefore ultrasound measurements could be used routinely for intracavitary treatment planning in endocervical carcinoma and endometrial carcinoma.

Brachytherapy↗
PubMed1986

On the use of a quality index to specify high energy photon beams.

It is important to specify the beam quality in a simple and nonambiguous way in order on one hand to make comparisons easier between treatments performed in various hospitals, or at different times in the same hospital and on the other hand to facilitate the choice of numerical values for factors like restricted mass-collision stopping-power ratios and perturbation correction factors used in the conversion of ionization measurements into absorbed dose. We have adopted for high-energy photon beam specification a quality index (I) defined by the ratio (I20/I10) of ionizations measured with a constant source-detector distance for a reference field size 10 X 10 cm2. We have found that this quality index is independent of the source detector distance. On the other hand, the apparent linear attenuation coefficient measured on the exponential part of the tissue-maximum ratio curve can be calculated for any field size from the value of I for most high energy photon beams. In order to check the validity of the quality index for other linacs from other manufacturers, we have compared our results to published data related to various photon beams in a wide energy range: 2.5 to 45 MV.

Humans↗
PubMed1986

A comparison of build-up and depth dose characteristics of different photon beams for the treatment of Hodgkin's disease.

Measurements have been performed of build-up and depth-dose characteristics of photon beams under Hodgkin's disease treatment conditions as applied in two hospitals (AVL, Amsterdam and IGR, Villejuif). Although different types of accelerators, photon energies, field sizes and SSD are employed, similar dose distributions along the beam axis have been obtained in both centers. In order to explain this unexpected good agreement, the influence of the geometrical conditions of irradiation on the build-up and depth-dose distribution has been studied in detail for five photon beams (8 MV-25 MV) of three types of accelerators.

Evaluation Studies as Topic↗
PubMed1986

Biologic and anatomic problems of lung shielding in whole-body irradiation.

Lung shielding by lead blocks for reducing the dose to the lungs in whole-body irradiation results in relative protection of the leukemia cell population. The consequence is acceptable if the dose reduction is moderate (from 10 to 8 Gy) and if the shielded volume amounts to a small fraction (5%) of the body weight. The suggestion was made that certain limits should be put on the extent of shielding, so that the shielded lung fraction represents only 60% of the total lung volume.

Humans↗
PubMed1983

[Scanography].

Explore the source record for details and available documents.

Brain↗
PubMed1979

Total body irradiation techniques and dosimetry.

Irradiation techniques and dosimetric methods used for total body irradiation (TBI) performed at Institut Gustave Roussy (Villejuif) are presented. TBI are performed in a 5,6 MV X-ray beam produced by a linear accelerator Neptune. The patient, lying laterally on a couch at 4.20 m from the target, is irradiated by a horizontal beam with a mean nominal dose rate at the abdomen mid-plane of about 9 cGy per minute. The procedure used for TBI consists of three parts in order to deliver 8 Gy in the whole body except for lungs which are protected with a lead screen during a part of irradiation and receive a dose of 4 Gy. We have preferred using "in vivo" measurements methods rather than calculations to determine the doses at different points of the patients. Two kinds of detectors are placed on the patient's skin all along the total body irradiation : two sets of five Therados semi conductors probes permit to control the irradiation and lithium fluoride thermoluminescent dosimeters are used like reference detectors. The dosimetric results obtained during the TBI performed at IGR are discussed.

Abdomen↗
PubMed1977

Whole cutaneous irradiation in mycosis fungoides with 55KV x-rays. Technical study.

The authors describe a technique for a whole cutaneous superficial irradiation of mycosis fungoides by means of a fixed 55 KV X-Rays generator and a moving couche. Results of the dosimetric study are compared with thoses obtained with Lithium fluoride. Since 1964, twenty five patients have been treated. The results appear to be equivalent to those obtained with electrons. The technical problems of each methods are discussed.

Humans↗
PubMedDate not supplied

[Preliminary dosimetry study of the Orsay synchrocyclotron proton beam with a view to applying it therapeutically].

Using proton beams for treatment of malignant tumors of the eye allows high dose irradiation of the tumor volume with negligible irradiation of the surrounding critical structures. Actually, the clinical results reported from the Boston or Villigen groups which have experience of such a technique, are impressive. In France, it is planned to use soon 200 MeV proton beams from the Orsay synchrocyclotron 20 km from Paris. Therefore, a feasibility study has been conducted during year 1988, consisting of a dosimetric analysis of the characteristics of the Orsay proton beams. It was concluded that only simple modifications were necessary to make the beam clinically available for protontherapy and more specifically for treatment of uveal melanomas.

Animals↗