An organ dose calculation based on measurements is described which models the total dose delivered outside a beam from 10 to 50 cm from the field edge. The dose distribution is parametrized for each beam energy as a function of depth, distance from the edge, and field size and shape. The algorithm also takes into account the organ location relative to the beam. Comparisons with measurements in an Alderson phantom using thermoluminescent dosimetry are given for various typical treatments.

Cobalt Radioisotopes↗

PubMedDate not supplied

A mathematical child phantom for the calculation of dose to the organs at risk.

In order to calculate the doses received by the organs of 530 children treated by radiation for cancer between 1945 and 1969 at the G. Roussy Institute, we have developed a computer program for organ location calculation. To calculate the location of each child's organs of interest at the time of the treatment, only two parameters are necessary; sex and height or sex and age when the height at the time of the treatment is unknown. The algorithm is based on the metric studies of growth known as auxology. Each organ is located by one point representing its center. The model has been checked on 100 healthy children.

Aging↗

PubMedDate not supplied

Fast Fourier transform convolution calculations of x-ray isodose distributions in homogeneous media.

Convolution concepts were implemented using the discrete fast Fourier transform (FFT) to model the three-dimensional dose distribution due to x-rays produced by a medical linear accelerator. Convolution kernels were employed that had been calculated by Mackie using the EGS4 Monte Carlo code. The EGS4 code was also used to estimate initially the spectrum by simulating the production, filtering, and flattening of the beam in the collimator of the linear accelerator. The continuous bremsstrahlung spectrum was modeled using five discrete energies. The more subtle field-size effects of collimator scattering on the spectrum were obtained by calculating corrections to the spectral components using a least-squares search technique. Dose distributions were obtained using FFT convolutions of the kernels for each energy with the spectrally weighted fluence distributions for that energy. The dose distributions were compared with isodose distributions measured in a water phantom. The agreement was generally found to be better than 1% on the central axis. The calculation time for a single three-dimensional beam was approximately 20 min using a VAX/750 without an array processor. Methods were explored to reduce the calculation time using similar hardware, and estimates were made of how to reduce the calculation time using a more sophisticated computer system.

Electrons↗

PubMedDate not supplied

Simulation of x-ray spectral reconstruction from transmission data by direct resolution of the numeric system AF = T.

X-ray spectral reconstruction from transmission data was investigated by direct resolution of the matrix system A*F = T using spectral algebra. Theoretical, numerical, and physical conditions were studied to obtain the physical solution of the problem. It is shown why the least-square-fitting methods may not give good results for high energy photon spectra above several MeV. The proposed method does not need a preshaped starting spectrum. Simulation studies have been made with arbitrary but realistic spectra of different shapes and maximum energies simulating the reality and using different materials as attenuator like carbon, aluminum, and even water. Conditions on the attenuator choice to obtain the physical solution of the system are given. The reconstruction method provides good results in the radiotherapy energy range despite measurement errors. The computation is quick and implementable on a personal computer with a mathematical coprocessor.

Computer Simulation↗

PubMedDate not supplied

[General Review on the Treatment of Malignant Hemopathies].

Explore the source record for details and available documents.

Antineoplastic Agents↗

PubMedDate not supplied

[Ambulatory ligation of the sapheno-femoral junction. Complement of Dr. Muller's ambulatory phlebectomy technique].

The early diagnosis of incompetence of the sapheno-femoral junction is made possible by combined ultrasonography/Doppler. Thus when the great saphenous vein is not too dilated and is not the site of severe ectasia, ligation of the junction may be sufficient to deal with malfunction of the latter. This is an outpatient procedure. Following local anesthesia (lidocaine 0.25%), a 4 cm incision is made in the inguinal fold between the femoral artery and the tendon of gracilis muscle. Dissection of the great saphenous exposes a lake distal to the collaterals of the sapheno-femoral junction and--by traction--obtains maximal exposure of the junction. A wide Weck hemoclip is used to interrupt reflux in the incompetent junction. We ligate the pudendal veins entering the femoral vein separately. This procedure neutralizes a major perforator under local anesthesia by an out-patient technique free of morbidity. Varicose veins are removed subsequently using the technique of Dr. R. Müller.

Ambulatory Surgical Procedures↗

PubMedDate not supplied

[Leber's hereditary optic neuropathy].

233 personal cases of leber's optic neuropathy have been analyzed by the authors in order to present clinical symptoms, evolution and genetic aspects. A group of 23 patients, in which 7 presented the disease and the others were asymptomatic members of families with the disease, was analyzed on evaluation of abnormalities of evoked visual responses; An other similar group, in repartition of subjects, was analyzed on frequency of cardiovascular abnormalities. The results have been analyzed and discussed about the role of predictive symptoms in diagnosis of the acute phase of the disease.

Adolescent↗

PubMedDate not supplied