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Biomedical subjects

E Briot

Publications and source records attributed to E Briot.

At least 19 recordsLinked to original sources
PubMed2003

[Optimisation in brachytherapy].

Advances in technology have initiated a process of redefinition of planning and evaluation of brachytherapy. The new approach involves conformal positioning of a source configuration for which the treatment isodose contour is adapted to the shape of the target volume which is defined by 3D dimensional imaging. A good implant aims for a balance between good coverage of the target volume, a high dose uniformity inside the target volume and a steep dose fall-off outside the target volume. Computer hardware and software is now available to obtain a high level of sophistication, for instance in treatment planning. In addition, new after loading equipment became available allowing a large variety in source placement in the catheters. To facilitate optimisation procedures, new parameters for the judgement of the quality of the implant have been suggested.

Brachytherapy↗
PubMed2003

[Brachytherapy in cervix cancers: development of techniques and concepts].

Brachytherapy plays an important role in the treatment of patients with cervical carcinoma. Technical modalities have evolved during the last years and have benefited from imaging modalities development, specially MRI. Imaging modalities contribute to a better knowledge of tumoral extension and critical organs. Ultrasound during brachytherapy has led to the almost complete eradication of uterine perforation. In the future, a more systematic use of systems allowing optimization may induce a better dose distribution in the tumor as well as in the critical organs. Recent data provided information in favor of a better analysis in the relative role of dose-rate, total dose and treated volume and their influence on the local control and complication incidence. Concomitant radiochemotherapy represents a standard in the treatment of patients with tumoral size exceeding 4 cm. Some questions still remain: is concomitant chemotherapy of benefit during brachytherapy? Is there any place for complementary surgery, specially in patients with complete response after external irradiation with concomitant chemotherapy and brachytherapy? In order to answer the former question, a phase III randomized trial is going to start, with the Fédération Nationale des Centres de Lutte Contre le Cancer as a promoter.

Antineoplastic Agents↗
PubMed2002

[Recommendations for quality control in curietherapy].

Brachytherapy consists of sealed radioactive source implantation. The diversity in the nature of radioelements, in their energy and activity requires strict implantation and utilization rules. These rules include radioactive source physical parameters check, after-loading machine and treatment planning system quality assurance and safe and reproducible dosimetric systems. Patient and medical workers information guarantee radioprotection and prevention of accidental exposures.

Brachytherapy↗
PubMed2000

High-dose-rate brachytherapy as sole modality for early-stage endobronchial carcinoma.

PURPOSE: To evaluate exclusive high-dose-rate brachytherapy for localized early-stage non-small-cell bronchial carcinoma; to develop new insights in treatment-catheter positioning and tumor-volume assessment by computed tomography (CT) scan. METHODS AND MATERIALS: Between 1992 and 1996, 34 patients with non-small-cell bronchial carcinoma were treated by brachytherapy alone. All patients were medically inoperable and had contraindications for external beam irradiation. The treatment protocol was six sessions of 5 Gy over 6 weeks. The treatment catheter was placed under fiberoscopy and was positioned with the help of spacer catheters or with a surrounding plastic tube; CT scan was performed in 50% of the cases to measure the spacing between the applicator and the bronchial wall. Dose prescription was individually based on clinical and radiologic evaluation of tumor volume. RESULTS: Local disease failure occurred in 5 patients (15%). With a median follow-up of 2 years, the local control rate was 85% and the survival rate 78%. No acute toxicity was found, except one pneumothorax. CONCLUSION: Brachytherapy alone can give an optimal therapeutic ratio in small endobronchial carcinomas without radiation-induced morbidity. Such results are achieved after careful tumor volume evaluation and individualized treatment catheter positioning.

Adult↗
PubMed2000

Regional cerebral blood volume response to hypocapnia using susceptibility contrast MRI.

We used steady-state susceptibility contrast MRI to evaluate the regional cerebral blood volume (rCBV) response to hypocapnia in anesthetised rats. The rCBV was determined in the dorsoparietal neocortex, the corpus striatum, the cerebellum, as well as blood volume in extracerebral tissue (group 1). In addition, we used laser-Doppler flow (LDF) measurements in the left dorsoparietal neocortex (group 2), to correlate changes in CBV and in cerebral blood flow. Baseline values, expressed as a percentage of blood volume in each voxel, were higher in the brain regions than in extracerebral tissue. Hypocapnia (P(a)CO(2) approximately 25 mmHg) resulted in a significant decrease in CBV in the cerebellum (-17 +/- 9%), in the corpus striatum (-15 +/- 6%) and in the neocortex (-12 +/- 7%), compared to the normocapnic CBV values (group 1). These changes were in good agreement with the values obtained using alternative techniques. No significant changes in blood volume were found in extracerebral tissue. The CBV changes were reversed during the recovery period. In the left dorsoparietal neocortex, the reduction in LDF (group 2) induced by hypocapnia (-21 +/- 8%) was in accordance with the values predicted by the Poiseuille's law. We conclude that rCBV changes during CO(2) manipulation can be accurately measured by susceptibility contrast MRI. Abbreviations used: ANOVA analysis of variance CBF cerebral blood flow CBV cerebral blood volume CPMG Carr-Purcell-Meiboom-Gill FiO(2) fractional inspired oxygen ICP intracranial pressure LDF laser-Doppler flow MABP mean arterial blood pressure MRI magnetic resonance imaging MTT mean transit time PaCO(2) arterial partial pressure of carbon dioxide PaO(2) arterial partial pressure of oxygen PET positron emission tomography rCBV regional cerebral blood volume SPECT single-photon emission computed tomography

Analysis of Variance↗
PubMed2000

Prospective randomized comparison of single-dose versus hyperfractionated total-body irradiation in patients with hematologic malignancies.

PURPOSE: Fractionated total-body irradiation (HTBI) is considered to induce less toxicity to normal tissues and probably has the same efficacy as single-dose total-body irradiation (STBI) in patients with acute myeloid leukemia. We decided to determine whether this concept can be applied to a large number of patients with various hematologic malignancies using two dissimilar fractionation schedules. PATIENTS AND METHODS: Between December 1986 and October 1994, 160 patients with various hematologic malignancies were randomized to receive either a 10-Gy dose of STBI or 14.85-Gy dose of HTBI. RESULTS: One hundred forty-seven patients were assessable. The 8-year overall survival rate and cause-specific survival rate in the STBI group was 38% and 63.5%, respectively. Overall survival rate and cause-specific survival rate in the HTBI group was 45% and 77%, respectively. The incidence of interstitial pneumonitis was similar in both groups. However, the incidence of veno-occlusive disease (VOD) of the liver was significantly higher in the STBI group. In the multivariate analysis with overall survival as the end point, the female sex was an independent favorable prognostic factor. On the other hand, when cause-specific survival was considered as the end point, the multivariate analysis demonstrated that sex and TBI were independent prognostic factors. CONCLUSION: The efficacy of HTBI is probably higher than that of STBI. Both regimens induce similar toxicity with the exception of VOD of the liver, the incidence of which is significantly more pronounced in the STBI group.

Adolescent↗
PubMed1997

Dosimetric comparison of an integrated multileaf-collimator versus a conventional collimator.

The dosimetric characteristics of both a conventional GE collimator (CC) and a GE multileaf collimator (MLC) are compared for different photon beam energies. The integrated GE MLC consists of 32 pairs of tungsten leaves, replacing the lower pair of jaws of the conventional collimator. Measurements were performed with the conventional collimator before this collimator was replaced by the MLC. All parts of the accelerator except the collimator remained the same. Leakage and transmission measurements show good agreement with the manufacturer's specification, stating a leakage between leaves of less than 1% for all energies and a transmission through leaves of less than 0.5%. The dosimetric characteristics of both collimators are very similar for square and rectangular fields. No significant change in beam quality, beam attenuation and depth of maximum dose could be detected within the measurement accuracy. The MLC output ratio variation is smaller than the one measured with the CC. The penumbra difference in the Y direction is less than 0.5 mm at a depth of 5 cm in phantom; in the X direction the penumbra is 1 mm larger for the MLC due to the rounded leaf fronts. As the two leaf banks replace the lower pair of collimator jaws the distance from the collimator end to the isocentre is similar for the two collimators, therefore the MLC does not reduce the flexibility of the treatment unit. For symmetrical and regular collimator settings the MLC can be treated as the CC.

Biophysical Phenomena↗
PubMed1996

The use of diode dosimetry in quality improvement of patient care in radiation therapy.

The purpose of this work is to improve the quality of patient care in radiation therapy by implementing a comprehensive quality assurance (QA) program aiming to enhance patient in vivo dosimetry on a routine basis. The characteristics of two commercially available semi-conductor diode dosimetry systems were evaluated. The diodes were calibrated relative to an ionization chamber-electrometer system with calibrations traceable to the National Institute of Standards and Technology (NIST). Correction factors of clinical relevance were quantified to convert the diode readings into patient dose. The results of dose measurements on 6 patients undergoing external beam radiation therapy for carcinoma of the prostate on three different therapy units are presented. Field shaping during treatments was accomplished either by multileaf collimation or by cerrobend blocking. A deviation of less than +/-4% between the measured and prescribed patient doses was observed. The results indicate that the diodes exhibit excellent linearity, dose reproducibility, minimal anisotropy, and can be used with confidence for patient dose verification. Furthermore, diodes render real time verification of dose delivered to patients.

Calibration↗
PubMed1995

[Prediction of respiratory complications after surgery of the abdominal aorta].

The most frequent type of complication in patients undergoing aortic surgery is respiratory. Preoperative lung function (PFT) and arterial blood gas measurement (ABG) are often carried out to assess the risk more precisely. The aim of the present retrospective study was to determine which value of lung function test could identify patients who developed such complications. "Receiver Operating Characteristic" (ROC) curves and the area beneath the curve for the diagnosis of respiratory complications were calculated for each variable of PFT and ABG. The greatest Youden index for each variable was chosen as indicative pulmonary function criterion of increased risk of pulmonary complications. One hundred and ninety-five patients (age: 65 +/- 10 years) were included. Respiratory complications occurred in 15% of patients. Respiratory complications increased from 12% if the vital capacity (VC) was > or = 77% of the predicted value to 35% if the VC was < 77% (P = 0.002), and from 10% if the FEV1 was > 76% to 34% if the FEV1 was > or = 76% (P = 0.0005). A decreased PaO2 or increased PaCO2 was not correlated with an increased incidence of respiratory complications. Length of stay in ICU or in hospital were increased when VC or FEV1 were low. Frequency of pulmonary complications was 9% in patients without PFT abnormalities, 16% in patients with either diminished VC or FEV1 and 35% in patients with both lowered VC and FEV1. However, all the areas under the ROC curves were < 0.7 and the sensitivity of the different variables was low. It is concluded that routine preoperative PFT and ABG cannot predict respiratory complications after abdominal aortic surgery.

Aged↗
PubMed1995

[Conformal radiation therapy. Fédération nationale des centres de lutte contre le cancer (FNCLCC)].

The authors present the summary of a workshop of a group of radiation oncologists and radiation physicists on three dimensional treatment planning and conformal radiation therapy with multileaf collimator. It appears that this technic must be considered as experimental and that it cannot be promoted in all radiotherapy departments without scientific and clinical evaluation.

Evaluation Studies as Topic↗
PubMed1994

Consequences of two different doses to the lungs during a single dose of total body irradiation: results of a randomized study on 85 patients.

PURPOSE: To evaluate the incidence of lung complications and leukemia recurrences after two different doses to the lungs during total body irradiation. METHODS AND MATERIALS: Seventy-nine patients with acute leukemia (AML or ALL) in first complete remission or chronic myeloid leukemia in the chronic phase, five patients with high grade lymphoma, and one with chronic lymphocytic leukemia were entered in the study. They were given a single dose of total body irradiation (10 Gy over 4 h) with two different doses to the lungs (6 Gy or 8 Gy) prior to bone marrow transplantation. The median dose rate was 0.04 Gy/min. The median follow-up for both groups of patients was 24 months. RESULTS: The actuarial 5-year overall survival rate was similar in both groups, 59% and 43% for patients given 8 Gy and 6 Gy to the lungs, respectively. The lung complication rate was similar in the two groups (28% vs. 22% for the 8 Gy and 6 Gy group, respectively). The actuarial leukemia recurrence rate was significantly higher in the group of patients given 6 Gy to the lungs (25%) vs. 0% in the 8 Gy group. Interestingly, all recurrences occurred in the group of patients who were given 6 Gy to the lungs, who had acute leukemia, and no chronic graft vs. host disease (GVHD). CONCLUSIONS: Although the number of patients was not very large and the follow-up relatively short, these findings suggest that a lower dose to the lungs could lead to an increased incidence of leukemia recurrences due to a lower dose to the thoracic wall or to lower incidence of chronic GVHD.

Adolescent↗
PubMed1993

Radiotherapy after ovarian transposition: ovarian function and fertility preservation.

The outcome of ovarian function preservation and fertility after ovarian transposition was examined in women treated for cancer. Of 134 patients, 126 were treated with radiotherapy and 72 with chemotherapy. In a multivariate analysis, three factors appeared to be prognostic of ovarian castration: the age over 25, MOPP chemotherapy and a total dose to the ovaries higher than 5 Gy. The incidence of birth was lower in the general population but no abnormality was observed.

Adolescent↗
PubMed1993

Class I and II HLA typing after a 10 Gy-4 hour therapeutic total body irradiation.

Class I and II HLA typing was investigated before and at various intervals after a 10 Gy total body irradiation delivered over 4 h, prior to allogeneic bone marrow graft for various hematological malignancies, in 14 patients. A reliable class I HLA typing appeared to be possible in almost all cases 6-8 hours after the start of irradiation but was only possible in 5 patients after 24 h. Preliminary results with class II antigens might suggest a more marked "fragility" of this antigen class after irradiation. These results encourage the drawing of blood samples for HLA grouping as soon as possible after accidental whole-body irradiation.

Accidents↗
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↗
PubMed1990

The source-skin distance measuring bridge: a method to avoid radiation teleangiectasia in the skin after interstitial therapy for breast cancer.

Inappropriate positioning of interstitial Iridium 192 implants, used as booster dose in the breast conserving treatment of mammary cancer, may cause disturbing teleangiectasia of the breast skin, when high radiation doses are delivered on the dermal blood vessels. Based on the localization of the vascular plexuses in human breast skin, and on the dose distribution around different types of interstitial implants, a method is described to avoid overlap between the high dose area of the implant and the blood vessels in the skin. The latter are demonstrated to run within the first 5 mm under the epiderm. For source lengths varying from 5 to 8 cm, simple mathematical relations exist between the maximal security margin (MSM) and intersource distance (E) for single plane implants (MSM = 0.4 (E + 1)), double plane square implants (MSM = 0.4 E) and double plane triangular implants (MSM = 0.4 (E - 1)). We developed a device to measure precisely the distance between the radioactive wires and the overlying skin, along the whole source trajectory. Using this method, the occurrence of teleangiectasia in the breast skin after interstitial implants with Ir 192 may be significantly reduced.

Brachytherapy↗
PubMed1990

[Malignant non-Hodgkin's lymphoma of the conjunctiva. Apropos of 14 cases treated at the Institut Gustave-Roussy].

Non-Hodgkin lymphomas (NHL) of the conjunctiva are rare. Radiotherapy is usually considered to be the choice of treatment in such situations. Reported here are 14 cases of conjunctival NHL, treated at the Institut Gustave-Roussy from 1981 to 1988. Mean age of the patients was 53 years. The series comprised 7 stages of IE, 4 stages of IIE and 3 stages of III. Histological types were mostly "low-grade" according to the Working Formulation (9 cases out of 14). The irradiation technique took advantage of a customized facial lead mask and of a direct anterior electron beam. A small cylindrical lead block, hanging some millimetres above the eye, shielded the cornea and the lens. Local control was achieved for 17 eyes treated (out of 19 irradiated), with a follow-up ranging from 5 to 90 months. The 2 relapses occurred in the same patient, and could be treated by a second line irradiation of the same type. Immediate tolerance was good. Late sequelae were rare and actually included 4 cases of cataract which clearly could not be entirely attributable to the treatment. In conclusion, this sophisticated technique appears to be efficient and non-toxic, since it was able to achieve an almost 100% local control rate, together with a very low percentage of late complications.

Adult↗