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G Gaboriaud

Publications and source records attributed to G Gaboriaud.

29 records · Page 2Linked to original sources
PubMed1981

[Present clinical status of hyperthermia associated with radiotherapy (author's transl)].

Improved techniques for inducing heat: ultrasound, microwaves, diathermy with different application modalities, capable of producing localized superficial or deep, regional or total body hyperthermia have been responsible for the multiplication of clinical trials. These studies have confirmed the tumoricidal effect of hyperthermia alone, or more especially when combined with radiotherapy, and the good tolerance of normal tissues to localized temperatures of 42 to 43.5 degrees C even in previously irradiated cases. Localized heating does not seem to increase the incidence of metastasis. Enhancement ratios and therapeutic gain with respect to normal tissues are not yet well documented. Many problems, including the heterogenicity of tissues to be heated, difficulties with temperature monitoring, and selection of appropriate sequential scheduling of radiation and hyperthermia remain unsolved and further investigations are required.

Chemotherapy, Cancer, Regional Perfusion↗
PubMed1981

[Preliminary results for a 434 MHz microwave hyperthermia applicator (author's transl)].

Laboratory tests on inert gel and gel of different compositions were conducted to determine the distribution of isothermal temperature zones. The repartition in depth and along a perpendicular plane to the applicator axis was studied as a function of different parameters: the skin cooling water temperature of the applicator, the incident microwave power, the application time, the gel composition and the antenna position. Experimental results were compared to theoretical values corresponding to a plane microwave penetrating into a tissue-equivalent medium. To take into account in vivo temperature regulation phenomena, the same measurements were made in vivo in pigs and humans and compared to in vitro results.

Animals↗
PubMedDate not supplied

[Conformal radiotherapy: principles and classification].

'Conformal radiotherapy' is the name fixed by usage and given to a new form of radiotherapy resulting from the technological improvements observed during, the last ten years. While this terminology is now widely used, no precise definition can be found in the literature. Conformal radiotherapy refers to an approach in which the dose distribution is more closely 'conformed' or adapted to the actual shape of the target volume. However, the achievement of a consensus on a more specific definition is hampered by various difficulties, namely in characterizing the degree of 'conformality'. We have therefore suggested a classification scheme be established on the basis of the tools and the procedures actually used for all steps of the process, i.e., from prescription to treatment completion. Our classification consists of four levels: schematically, at level 0, there is no conformation (rectangular fields); at level 1, a simple conformation takes place, on the basis of conventional 2D imaging; at level 2, a 3D reconstruction of the structures is used for a more accurate conformation; and level 3 includes research and advanced dynamic techniques. We have used our personal experience, contacts with colleagues and data from the literature to analyze all the steps of the planning process, and to define the tools and procedures relevant to a given level. The corresponding tables have been discussed and approved at the European level within the Dynarad concerted action. It is proposed that the term 'conformal radiotherapy' be restricted to procedures where all steps are at least at level 2.

Accreditation↗
PubMedDate not supplied

[Radiotherapy using a combination of photons and protons for locally aggressive intracranial tumors. Preliminary results of protocol CPO 94-C1].

PURPOSE: From October 1993 through July 1998, 48 assessable adult patients with non-resectable aggressive intracranial tumors were treated by a combination of high dose photon + proton therapy at the Centre de Protonthérapie d'Orsay. PATIENTS AND METHODS: Grade 1 and 4 gliomas were excluded. Patients benefited from a 3D dose calculation based on high-definition CT and MRI, a stereotactic positioning using implanted fiducial markers and a thermoplastic mask. Mean tumor dose ranged between 63 and 67 Gy delivered in five weekly sessions of 1.8 Gy in most patients, according to the histological types (doses in Co Gy Equivalent, with a mean proton-RBE of 1.1). RESULTS: With a median 18-month follow-up (range: four-58 months), local control in tumors located in the envelopes and in the skull base was 97% (33/34), and in parenchymal tumors, 43% (6/14) only. Two patients (5%) presented with a clinically severe radiation-induced necrosis (temporal lobe and chiasm). CONCLUSION: In our experience, high-dose radiation combining photons and protons is a safe and highly efficient procedure in selected malignancies of the skull base and envelopes.

Adult↗
PubMedDate not supplied

[3D automatic expansion: clinical application].

The determination of the various volumes (GTV: gross target volume, CTV: clinical target volume, PTV: planned target volume) recommended by the ICRU 50 report is a critical step in conformal treatment planning, since treatment optimisation procedures and documentation rely on accurate dose-volume histograms. The shape and the size of the CTV vary with the computer algorithm, the patient image acquisition parameters, the definition of the GTV and the margins surrounding it. The automatic expansion programs included in commercially available treatment planning system require careful validation and control before and during their routine use by the clinicians. Significant differences have been observed between 2D- and 3D-based expansions, with a usual underestimation of the PTV by 2D algorithms.

Algorithms↗
PubMedDate not supplied

[Use of a multileaf collimator for the production of intensity-modulated beams].

In external radiotherapy, the use of intensity modulated fields has been proposed for tissue and non-homogeneity compensation or for the generation of conformal dose distributions. Multileaf collimators can be employed dynamically for the modulation of the X-ray field in two dimensions. Efficient dynamic collimation became possible due to advances in computer and linear accelerator technology. It presents a number of advantages over conventional methods such as the use of compensators. We have developed a program which calculates, from a given intensity distribution, the motion of the MLC leaves as a function of monitor units, and we have applied it on a Varian linear accelerator with a 40 pair multileaf collimator. The analysis of the experimental results demonstrates the feasibility and the potential of the method.

Algorithms↗
PubMedDate not supplied

[Dosimetry of small-size photon beams].

A high performance standard radiotherapy treatment unit could be used to perform stereotactic radiosurgery. The dosimetric aspects of stereotactic irradiation with small size photon beams (energies from 5 to 25 MV produced by electron linear accelerator or gamma-rays produced by cobalt-60 treatment unit) are analyzed. The diameter of circular beams used are 5 to 40 millimeters wide at the isocenter of the treatment unit. The dosimetry of small x-ray fields is complicated by two factors: the relationship between detector size and field size dimensions, and the lack of lateral electron equilibrium. The large dose gradients outside the beam's central axis require dosimetry techniques with higher spatial resolution. To determine the best dosimetry system for measurements at the beam's small focal point, particularly for measurement of the field size dependent on output factors, several different detectors were investigated: ionization chamber, silicon diode, diamond detector, thermoluminescent dosimeter, and film. Ionization chamber, which presents a sensitive volume smaller than 0.02 cm3, is the most commonly recommended detector for field diameter above 8 mm. Current representative examples of dosimetric measurements for different x-ray energies, including percent depth dose, tissue maximum ratios, beam profiles (off axis ratios), and output factors, are presented and discussed. As well, the dosimetric characteristics of small photon beams are detailed.

Photons↗