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Biomedical subjects

M Heintz

Publications and source records attributed to M Heintz.

7 recordsLinked to original sources
PubMed1999

Fluorescence 125I eye applicator.

A new approach to optimize curative eye plaque brachytherapy is presented. The application of ophthalmic plaques is a common therapy modality for small and medium sized intraocular tumors. At Essen University Hospital eye applicators with photon emitting 125I seeds are used for the treatment of tumors with a thickness from 5 to 10 mm. Our clinical experiences indicate that the dose distributions of these applicators-used so far worldwide-are not optimal. A steeper dose falloff would meet the radiobiological requirements better, to provide the eradication of all tumor cells as well as sufficient occlusion of tumor supplying blood vessels. Our investigations for eye plaque optimization are based both on measurements and Monte Carlo simulation. For fast dosimetric measurements we have built a computer controlled device which allows reading out, directly and simultaneously, 16 1 mm3 scintillators. For the numerical simulations of the dose distribution of 125I eye plaques we have adapted a Monte Carlo program originally developed to calculate the synchrotron radiation in particle physics. We have investigated the influence of geometrical as well as physical eye plaque parameters on the dose distribution: Shielding of the primary radiation, penumbra modification, and energy conversion by exploiting fluorescence x-radiation have been considered. New types of fluorescence eye applicators have been designed which are more suitable for the prevention of radiopathic effects on structures at risk.

Brachytherapy↗
PubMed1996

Direct reading measurement of absorbed dose with plastic scintillators--the general concept and applications to ophthalmic plaque dosimetry.

We have developed dosemeters based on plastic scintillators for a variety of applications in radiation therapy. The dosemeters consist basically of a tissue-substituting scintillator probe, an optical fiber light guide, and a photomultiplier tube. The background light generated in the light guide can be compensated by a simultaneous measurement of the light from a blind fiber. Plastic scintillator dosemeters combine several advantageous properties which render them superior to other dosemeter types for many applications: minimal disturbance of the radiation field because of the homogeneous detector volume and the approximate water equivalence; no dependence on temperature and pressure (under standard clinical conditions) and angle of radiation incidence; no high voltage in the probe; high spatial resolution due to small detector volumes; direct reading of absorbed doses; and a large dynamical range. The high spatial resolution together with direct reading make these detectors suitable for real-time 3-D dosimetry using multi-channel detector systems. Such a system has been developed for eye plaque dosimetry and successfully employed for dosimetric treatment optimization. The plaque optimization can be performed by dosimetric measurements for the individual patient ("dosimetric treatment planning"). The time consumption for this procedure is less than for a physically correct computer-based therapy planning, e.g., by means of a Monte Carlo simulation.

Biophysical Phenomena↗
PubMed1996

Surgery in ovarian cancer: the concept of cytoreductive surgery.

Critical analysis of the collected evidence on cytoreductive surgery suggests a median survival benefit of 9-12 months in combination with platinum-based chemotherapy. Recently, a randomized study on the value of secondary cytoreduction showed a median survival benefit of 6 months for those with small residual disease after the second operation. Primary cytoreduction is feasible in approximately 70% of patients, with an acceptable level of morbidity. The reported evidence justifies a serious attempt at cytoreductive surgery at the first operation by an experienced gynaecological oncologist.

Carcinoma↗
PubMed1979

[Antenatal diagnosis of the sex of the fetus by diagnostic ultrasound (echography) (author's transl)].

The authors present the results they obtained in diagnosing fetal sex in utero by the use of real-time echography. They also have reviewed the other different techniques for the diagnosis and their fallibility. The prediction of fetal sex is possible in 90 p. 100 of echographies carried out routinely. When a very careful well codified technique is used the method becomes highly reliable. In a successive series of 103 pregnancies fetal sex was diagnosed correctly in every case. The authors point out that they diagnose female sex through positive echographic finding and not by a process of exclusion of the male organs.

Amniotic Fluid↗