Biomedical subjects

D Fehrentz

Publications and source records attributed to D Fehrentz.

At least 37 records · Page 2Linked to original sources

PubMed1979

[An analytical method for calculation of electron dose distributions. Part II: Experimental verification and application in coplanar irradiation techniques (author's transl)].

The analytical method for calculation of electron dose distributions described in part I was experimentally verified using a 42-MeV betatron. For this, a comparison was made between the calculated and the measured dose distributions obtained with a homogeneous or inhomogeneous water or polystyrol phantom with plane or with uneven surfaces, the inhomogeneities consisting in cavities and cork intercalations. Thus, the accuracy of the algorithm and of the consideration for inhomogeneities and irregular surfaces is demonstrated, and limitations of the method's applicability are shown. Some examples of calculated dose distributions in coplanar irradiation techniques using solely electron beams or else a combined treatment with photons and electrons are exhibiting the particular bearing of electronic data processing on the treatment planning in depth therapy with electrons in the energy range above 20 MeV.

Computers↗

PubMed1979

[An analytical method to calculate electron dose distributions. Part I: Method (author's transl)].

A method for the calculation of electron dose distributions is described. The dose distributions of stationary electron beams in water are represented by formulas for depth dose curves and transverse distributions. Curved surfaces, oblique incidence of rays, and inhomogeneities are taken into account by applying the law of distance and the method of equivalent thicknesses of water layers. A detailed program is given to calculate the electron dose distributions in that plane of the central ray which is at right angle to the theoretical circle plane of a 42 MeV betatron.

Electrons↗

PubMed1976

[Consideration of large in homogeneous regions of the computation of electron dose distributions].

A simple method, suggested by Laughlin and Pohlit for calculation of dose distribution in electron beams which is considering the nonhomogeneous structure of the body, has been examined with regard to its accuracy within the energy range up to 42 MeV. Thereby, the dose distributions calculated and measured over nonhomogeneous thorax phantoms were compared. The method is based on the dose in homogeneous muscular tissue for a depth of area-weight identical to that in nonhomogeneous tissue with corrections being made according to the law of squared distances. Thus, only the loss of electron energy but not the scattering is considered. Smaller nonhomogeneous zones are completely neglected, larger ones treated as regions of equal density. The present study of the region of the lung and previous papers concerning bones [13] and cavities [11] show that the method, apart from near surface cavities, yields a satisfying exactness of the calculated dose distributions. If larger inhomogeneities - especially of the lung - are regarded, their mean tissue density, their shape, size and location ought to be known as exactly as possible.

Electrons↗

PubMed1975

[Influence of cavities on dose distribution in electron depth therapy].

The influence of body cavities on the dose distributions of electrons between 15 and 42 MeV has been studied by means of ionometric and densitometric measurements in polystyrol and cork phantoms. The results show that superelevated doses appear behind the cavities near the surface of the head and the neck caused by scattered electrons of about 10% of the maximum dose in the homogene muscle tissue, particulary by small electron energies. The dose points are spatial very limited with diameters of 1 to 2 cm. With greater depths, i.e. for electron energies of 10, 25 and 42 MeV from 2, 4 and 6 cm respectively, no more superelevated dose caused by the electron scattering appears. All the other body cavities, particulary in the lungs and in the gastrointestinal tract, have for that reason an influence on the dose distribution essentially by the electron radius increased with the cavity length. The electron scattering and the organ motions provide for an great dose equalization.

Absorptiometry, Photon↗

PubMed1973