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Biomedical subjects

A Dutreix

Publications and source records attributed to A Dutreix.

At least 73 records · Page 4Linked to original sources
PubMed1983

Intercomparison of iridium-192 wire used in interstitial radiation therapy.

The results of an intercomparison which took place in 1976 when 2 sets of 192Ir wire, one English, the other French, were exchanged and their activities measured by the producers, one standardizing laboratory and two radiation therapy centres. The average differences ranged from 0.7 to 3.2 per cent. The differences in the derivation of basal dose rate as defined in the Paris system, by the two radiation therapy centres, were also investigated.

Brachytherapy↗
PubMed1982

[Oxygen enhancement ratio (OER) and therapeutic gain factor (GF) for low-dose irradiation with californium-252].

The potential benefit of the introduction of californium-252 in interstitial and intracavitary therapy is related to the greater efficiency of its neutron emission against anoxic cancer cells. In that respect, the oxygen enhancement ratio (OER) of the 252Cf emission has been determined for a continuous low dose rate irradiation. The biological system is growth inhibition in Vicia faba bean roots. A new Vicia faba "BelB" strain has been used, which better tolerates long periods (up to about 10 hours) of anoxia. In a first series of experiments, for a 252Cf (Dn + gamma) dose rate of 0.11 Gy . h-1, an OER of 1.4 +/- 0.1 was observed (the gamma contribution of D gamma to the total absorbed dose Dn + gamma was 0.35 at the position of the root tips). In a second series of experiments, in somewhat different geometrical conditions with a 252Cf (Dn + gamma) dose rate of 0.13 Gy . h-1, an OER of 1.5 +/- 0.1 was observed (D gamma/Dn + gamma = 0.42). The OER values observed for similar irradiation times, with iridium-192 gamma-rays, were 2.3 +/- 0.2 and 2.6 +/- 0.1 respectively, which leads to therapeutic gain factors (GF) of 1.6 and 1.7 respectively. These GF values are slightly lower than those previously obtained (GF = 1.8) on the same system, with d(50)-Be, p(75)-Be and 15 MeV neutron beams.

Californium↗
PubMed1982

[Relative biological effectiveness (RBE) of low-dose californium-252].

Relative biological effectiveness (RBE) of 252Cf, with respect to 192Ir, has been determined at the low dose rates commonly used in interstitial and intracavitary therapy. The biological criterion was growth reduction in Vicia faba bean roots. Two varieties of Vicia faba were used. For Vicia faba Sutton's seeds, an RBE of 5.7 to 6.6 was obtained for 252Cf Dn + gamma doses of 0.5 to 0.2 Gy respectively and at a Dn + gamma dose rate of 0.11 Gy-1. The gamma contribution D gamma/Dn + gamma at the level of the root tipes was 0.35 and the derived RBE of the neutron emission of 252Cf was then 8.2 to 9.7. For Vicia faba Be1B and in the same irradiation conditions, an RBE of 5.1 to 6.2 was obtained for the total (n + gamma) 252Cf emission and for Dn + gamma doses of 0.4 to 0.2 Gy respectively. These values lead to an RBE of 7.4 to 9.0 for the neutron emission of 252Cf. For Vicia faba BelB, but for another source arrangement (Dn + gamma dose rate of 0.13 Gy . h-1 for 252Cf), an RBE of 5.6 to 7.5 was obtained for the total (n + gamma) emission of 252Cf and for Dn + gamma doses of 0.4 to 0.1 Gy respectively. The gamma contribution (D gamma/Dn + gamma) at the level of the root tips was 0.42, and the derived RBE of the neutron emission of 252Cf was then 8.9-12.3.

Californium↗
PubMed1981

Biological and technical principles of total body irradiation for bone marrow graft conditioning.

The aims of total body irradiation, namely immunologic suppression of the hematopoietic tissues and eventually eradication of leukemia, require a large dose which may cause detrimental effects on healthy tissues. The main problem is raised by the interstitial pneumonitis and a relative protection of the lung is advisable. A partial reduction of the dose to the lung may cause an important increase of the number of surviving cells in the cell population the irradiation is aiming aiming at. Technical problems are raised to keep this increase to an acceptable value. A relative protection of the critical tissues can be achieved by a convenient time distribution of the dose, since the repair of sublethal injuries taking place between the sessions of a fractionated irradiation or during the course of low dose rate irradiation is larger for intestine, lung..., than for bone marrow and probably leukemic cells. Animal experiments have provided radiobiological data for estimating the therapeutic benefit related to the fraction number or to the dose rate.

Bone Marrow↗
PubMed1979

Total body irradiation in bone marrow transplantation. Hôpital Saint-Louis results.

Total body irradiation was used in 22 patients as part of their conditionning regimen for bone marrow transplantation. Nine patients with acute leukemia received 1 000 cGy TBI in addition with chemotherapy. None of them survived and the main cause of death was interstitial pneumonitis (50%). 4 patients received 1 000 cGy with a lung shielding of 500 cGy. Two patients with acute leukemia died of leukemia and sepsis, two patients had aplastic anemia, one is surviving, the other died of severe GVHD and infectious complications. Nine patients with severe aplastic anemia strongly immunized by previous blood transfusions received 800 cGy TBI with a lung shielding of 400 cGy. No rejection was observed and 7 patients (63%) are currently alive. One patient died of interstitial pneumonitis probably related to CMV infection, one of subacute necrotizing hepatitis, two of severe acute GVHD. It is concluded from this study that TBI remains the best immunosuppressive conditioning regimen even in strongly immunized patients. It may be a contributing factor of the incidence and severity of interstitial pneumonitis. A reduction of the dose ot the lung to 400-500 cGy seems to decrease the severity of this complication.

Anemia, Aplastic↗
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↗
PubMed1978

The Paris system in interstitial radiation therapy.

As a result of almost 20 years' experience using 192Ir wires in interstitial radiation therapy, a new method of dose calculation has been evolved, which is especially suitable for the techniques employed. Because this system was developed and brought into routine use in Paris, it was called the Paris System. Its basic principles are outlined in this report and the manner in which it is used in clinical practise is explained.

Breast Neoplasms↗
PubMed1978

[Present day development of the Paris System. First part: coplanar patterns and those called "in squares" (author's transl)].

The Paris System is a previsional dosimetric system which facilitates the work of curietherapists working with iridium 192 wires. Introduced about twelve years ago for radio-active implantations in one linear plane, this system has now become more generalized for implantations in two or more linear planes. After a brief review of the principles on which the Paris System is based, and introducing the new definitions arising from its development, the authors present the results of a systematic computerized study. The results obtained were used to establish, among others, the simple relationships between the geometric implantation data (disposition, length, number, separation... of the radioactive lines) and the dimensions of the volume treated, for the coplanar patterns and those called "in squares",

Humans↗
PubMed1977

[The practical application of computer dosimetry in gynaecological radiotherapy. 1,200 cases studied between 1968 and 1976 of the Gustave-Roussy institute (author's transl)].

Experience gained since 1970 by the study of 1,200 cases in which computerised dosimetry was used has led to the proposition of a reliable and useful method. The results are expressed per 24 hours of exposure in numerical form with regard to reference points, as well as in the form of drawn isodose curves in three different planes of reference: sagittal, frontal oblique by sources and frontal oblique passing by the plane of pelvic lymphatics. The authers recall the definition of reference points: bladder, rectum and pelvic walls. Using three typical examples, the aid provided by dosimetry is described. The concept of a "radiotherapy identity card" as a means of expressing the dose given is discussed. Comparison between dosimetric results and the results of treatment is encouraging in terms of the continued and fore general use of the method.

Cesium Radioisotopes↗
PubMed1976

[Study of the effectiveness of collection of cylindrical ionisation chambers irradiated in the pulsed radiation beams of a linear accelerator (author's transl)].

The difference of potential of supply of ionisation chambers is often inadequate to collect all the ions formed under the effects of a pulsed ray. The authors thus decided to determine the effectiveness of the collection of ions in one of the types of cylindrical ionisation chambers used most commonly at present in calibrating teleradiotherapy beams : Nuclear Enterprises chambers type 2505/3 A and 3 B. They determined essentially the value of effectiveness of the collection of ions using lithium borate, a thermoluminescent dosimeter the response of which is independent of dose up to very high flow rates. In the case of a pulsed ray emitted at constant frequency, it is easy to evaluate the dose delivered by impulsion and then compare the values obtained experimentally with those calculated using theoretical formulae such as Boag's formula. By contrast, in the case of an accelerator equipped with an electromagnetic sweep system of the beam in order to ensure a homogeneous dose of electrons, instantaneous flow doses (dose/impulsion) are difficult to evaluate by virtue of the sweep and variables from one type of energy to another. The authors thus sought an empirical method making it possible to evaluate the effectiveness of the collection of ions, knowing the energy of the incident electron beam and the dose flow indicated by the ionisation chamber receiving its usual supply tension. The results of this study as a whole show not only that it is essential to take into account the recombination of ions when ionisation chambers are used to calibrate the irradiation beams of new accelerators for medical use, but also that the effectiveness of the collection of ions is dependent upon the electronic equipment associated with the chamber.

Mathematics↗