Radiobiologia, radiotherapia最新文献

Routine testing of diagnostic radiology equipment performance has shown that more than 10% of equipment has not been properly setup. It also identifies equipment which is deteriorating in use as well as faults which need immediate correction. There is little doubt it is cost-effective and has also been shown to be effective in reducing the collective dose to the population from diagnostic radiology.

Resulting from the declared palliative aim and from time economic and tumor affecting high dosed single fraction meanwhile a hypofractionated irradiation rhythm was applied to more than 500 patients with lung carcinoma and 5 x 5 Gy were given in daily succession if possible. A hospitalization was necessary in a third of the patients. In spite of histology (NSCLC: 46%, SCLC: 35%) a mean survival of 12 months was attained, in which the fate is determined for 75% of the patients within the first year after therapy. Detrimental effects were not provoked by the applied irradiation mode.

In a period of almost 6 years three various therapeutic methods of inoperable oesophagus carcinoma were applied. The best survival was attained by a combination of irradiation with 5-FU-infusions and bleomycin. The mean survival was 8 months, contrary to 4 months by a combination irradiation/5-FU-infusions and 5 months by unique radiotherapy. Further analyses to radio-chemotherapy of inoperable oesophagus carcinoma are desirable with that to improve the survival of these tumors further on.

In a review the cardiac attendant reactions in tumor irradiation in thoracal area are represented by means of papers and experiences of our own. It is shown that the heart reacts differently on ionizing rays and in special cases it can become a critical organ for radiotherapy. The diagnostic practice and the phenomenon of pericardiac and myocardiac reactions are described in detail. Complications on coronary vessel system are not frequent but because of their clinical consequence always they have to take into consideration. Cardiac radioreactions can be transient or harmless but rarely can lead to vitally threatening situations. Therefore it is referred to symptoms, diagnostic proving and possible or necessary therapeutic measures. Because significant curative therapeutic results can be attained by radiotherapy in thoracal area and the chances for curing increase for many patients, a slight risk is justifiable for side-effects on healthy adjoining tissue. On the other hand undesirable side reactions can influence the life-quality of the tumor cured patients. Therefore a radiotherapy in intrathoracal tumors with the aim of healing without complications has to take into consideration the sensibility of heart in addition to those of lung and spinal marrow. Beside permanent development of physical-technical suppositions these biological aspects have a substantial influence on optimizing irradiation in thoracal area. Finally it is tried to formulate really existing possibilities reducing a risk for cardiac side-effects and to refer to prospective interesting problems.

The Relative Biological Effectiveness (RBE) of radiation with different LET has to be recognized in the planning of radiation therapy especially if one type of radiation should be replaced by another type or if both should be used within the same irradiation course. In radiation therapy it is suitable to consider the RBE in connection with dose dependent cell survival rates. These rates can be described by means of corresponding mathematical models. A simple way to calculate the RBE on the basis of the modern LQ-model is demonstrated. In that procedure the alpha/beta-ratios which are known at least approximatively for many organs and tissues can be used. The proposed method is demonstrated for the human skin and lung. For these organs we obtained RBE ranges from 3.4 to 1.2 and from 3.8 to 0.8, respectively, considering increasing doses. Thereby, for the lung it can be observed that the dose dependency of the RBE for small doses is especially strong. The obtained results are in good coincidence with experiences in clinical practice.

The record and verify system (EPS) answers the control and recording of carrying out irradiation. Connection between accelerator and personal computer is done by a process calculator. The EPS-programme runs at a personal computer and is written in TURBO-Pascal. A first realization will be done at linear accelerator NEPTUN 10p.

Dose distributions of a combination from telecobalt-arc-therapy and afterloading-therapy for radiation therapy of gynecological cancers were calculated, using a computer program developed in our institute. Taking as a basis CT-scans the bone structures were taken into consideration like inhomogeneities. Conclusions about the individual dose on sensitive organs into the irradiated area like bladder and rectum become possible. The influence of changing parameters such like distance of axis of arc-therapy can be shown clearly.

Proof of shielding and forming by absorbers was done in water phantom dosimetrically. Alterations of isodose course were measured in dependence of primary energy, as well as of thickness and density of the absorber materials. Piacryl or aluminium are not suitable for forming of irregular electron fields. They only effect a reduction of therapeutic range. For primary energies of 10.0 less than or equal to MeV less than or equal to E0- less than or equal to 20.0 MeV lead rubber and wood metal are to recommended in a thickness of less than or equal to 10 mm or less than or equal to 8 mm respectively.

The possibility is investigated to use shielded vaginal applicators for "line-shaped" 192Ir-sources to irradiate cervical carcinoma. Using segment-shaped absorbers of heavy metal the dose can be reduced in ventro-dorsal direction in area of rectum and bladder with irradiation of cervical carcinoma up to a factor of 2 in dependence of rectum and bladder position. Selecting a suitable source position and source standing time a dose reduction can be realized in cranial direction up to two centimetres from the portio.

To increase the quality of radiotherapy a verify and record system (VPS) was developed for teletherapy equipments, that takes control of manually adjusted irradiation parameters and of recording all relevant data of radiotherapy. The VPS can be adapted to special wishes of the user and it lends itself to application on different irradiation equipments. In the represented paper especially the extent of efficiency of the system is shown which is characterized by high operating comfort, flexible reacting to exceptional cases and by high date and operating security. The testing phase on an accelerator model has been brought to a close, actually the system is installed to an electron linear accelerator "Neptun 10p" and led to clinical trial.