Search PubMed⌕ Search

Biomedical subjects

G Marinello

Publications and source records attributed to G Marinello.

50 records · Page 3Linked to original sources
PubMed1979

[Automatic calculation of the base dose in the Paris System (author's transl)].

The systematic dosimetric control after all endocurietherapy implantations considered to be in conformity with the Paris System is often made manually from tracings of the radioactive threads and a series of tables which gives the strength of the dose as a function of the distance from the thread. The authors describe a calculating programme, developed in a small Hewlett Packard calculator associated with a printing-out apparatus (without graph tracings), which can determine the strength of the base dose and the tracing of the isodoses in the central plane for all radioactive implantations belonging to the field of application of the Paris System. A schematic representation of the organization of the programme includes feeding of information in the form of Cartesian co-ordinates; the geometric determination of the points for calculating the base doses, the calculation of the strength of the base dose, the reference dose, and doses at particular points in the central plane, and finally, tracing the isodoses. Several examples are presented, after which the authors discuss the advantages as well as the limits of this method.

Brachytherapy↗
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

[Breakdown of the energy of a fixed 7 MeV electron bundle in the treatment of mycosis fungoides (author's transl)].

In order to treat patients with mycosis fungoides, the authors were led to breakdown the energy of a 7 MeV electron bundle emitted by a linear accelerator. With this aim, they sought to determine the nature, thickness and position of the decelerating which should be used to obtain adequate flow and energy of the electron bundle. They then explain the technique of total body irradiation of the patients, and in particular the way in which the functions of the bundle are effected. Finally, in order to diminish under-dosage in regions of the human body irradiated tangentially, they suggest the use of a perspex screen of variable thickness.

Electrons↗
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↗
PubMed1976

[Practical use of lithium borate in thermoluminescent dosimetry (author's transl)].

The authors recall the functional principles of thermoluminescent dosimeters: heating, apparatus for measuring the emitted light, circulation of nitrogen, reference source. They take this opportunity to stress the essential role played by the circulation of nitrogen over the dosimeters which equilibrates the temperature of the photo multiplier, reduces the emission of unwanted light, prevents the combustion of dust or other possible impurities and finally improves the reproductibility of the measurements even for high dosod for finding the optimum working conditions for the heating apparatus of the planchette in the most simple T.L.D. readers and in those where the heating apparatus of the planchette has a pre-heating phase. They then study the dosimetric properties of lithium borate incorporated in thin teflon discs (type DLB. 0.13 and 0.4). This shows itself to be very interesting for certain uses because it is a solid dosimeter which does not require annealing between two measurements. The reproductibility of the measurements obtained with this material, the stability of its response relative to the delay between radiation and reading (fading), its response relative to the absorbed dose plus the nature and the energy of the rays, are presented with the usual reservations made for this type of dosimetry. The authors conclude by citing a few applications where they have been able to achieve a satisfactory result with the aid of lithium borate.

Borates↗
PubMed1975

[Determination of the diffusion function of 25 MV x-rays in a tissue equivalent medium].

The diffusion function of 25 MV Roentgen rays in a tissue-equivalent material was determined experimentally as a function of the size of the beam and of the depth into the material. In order to characterize the beam, the attenuation of the beam in various materials was previously investigated. The results of the investigation demonstrate the important contribution of diffused radiation to the dose when using very high energy radiation.

Diffusion↗
PubMed1975

[Use of lithium fluoride in clinical dosimetry. Application to the measurement of the dose delivered to axilla by iridium 192 with endocurietherapy for carcinoma of the breast].

The aim of the work was the evaluation of the dose delivered to the axilla during endocurietherapy for carcinoma of the breast using Iridium 192. The position of the radioactive material with respect to the axillary zone differing with the patient seated or lying, the authors carried out an vivo dosimetric study using Lithium fluoride. They refer to the chief properties of Lithium fluoride which render it the dosimetric agent of choice for clinical work and give details of their experimental conditions, stressing the problems encountered in practice (response in relation to dose, mass of thermoluminescent powder to use, fading, regeneration etc.). They then describe the technique used for placing the thermoluminescent dosimeter in the axillary zone adjacent to the target volume irradiated. Results concerning 43 patients made possible the establishment of a significant correlation between the dose delivered to the axillary region and the site of implantation of the radioactive material in the breast, and show that, with identical tumour doses, this dose is little dependent upon the structure of the radioactive implant itself. They conclude that the dose delivered to the axillary region is of the order of 25% of the tumour dose if the radioactive implant is localised in the axillary tail, 10% if it is in the upper outer quadrant and negligeable if it is elsewhere.

Breast Neoplasms↗
PubMedDate not supplied

A general method to perform dose calculations along the axis of symmetrical and asymmetrical photon beams.

Many manufacturers of modern linacs provide collimators with jaws that can be set asymmetrically. In the present work, the authors propose the use of a product of four independent output factors related to the four jaws to calculate the reference dose rate of asymmetrical fields. Each of these factors is normalized to the maximum opening of the collimator. A general algorithm for symmetrical and asymmetrical fields is proposed for dose calculation. Calculations have been checked by measurements at the reference depth in a 4-MV x-ray beam.

Algorithms↗