The comparison of isodose plans: radiotherapy techniques in the treatment of thyroid ophtalmopathy.

Thyroid ophthalmopathy is listed among benign disorders as the fourth indication for radiotherapy. Radiation reduces symptoms and signs of the disease in 46-93% of patients. Except for the lenses, the orbital content is resistant to the usual radiation dose of 20 Gy in 10 fractions. A number of radiotherapeutic techniques which avoid the lenses have been suggested. The testing of different techniques was performed on the same patient by using a computerized simulation of lateral alternating and crossed photon beams from a 6 MV and 18 MV linear accelerator or cobalt device. The radiation from a 6 MV linear accelerator using lateral beams angled at 5 degrees posteriori gave the best results. By this technique both lenses receive below 10% of the prescribed dose with a safety zone of 20% of the field size. Isodose distribution in clinical target volume is within the range of 10%. The described technique is recommended as it enables a successful avoidance of both lenses with a satisfactory homogeneity of dose distribution in the clinical target volume.

[Radiotherapy of lung cancer]. / Radioterapija raka pluca.

The paper is aimed at approaching radiation therapy methods to physicians of other specialties and pointing to the potential of radiation therapy in the management of lung cancer patients. With the reference to its incidence and mortality rates, lung cancer ranks among the most frequent human malignant tumors. Therapy procedures for lung cancer depend upon tumor histology type, stage of disease and patient general condition. The said parameters therefore determine the application of surgery, radiation therapy and/or chemotherapy. In general, treatment results are usually rather poor, primarily due to lung cancer being the most frequently detected only as locally advanced or metastatic disease. Alike surgery, radiotherapy is a local form of treatment aimed at achieving local tumor control. This curative or palliative form of treatment is either applied alone or in combination with other treatment modalities. Irradiation is usually delivered by high energy photon beams from a telecobalt device or linear accelerator. The success of radiation therapy complies with the irradiation dose managed to be applied to tumor or tumor bed, which depends on patients general condition and site, size and spread of tumor. Radiotherapy with curative intent is applied in stage I, II and III non-small cell lung cancer patients with surgery being primarily applied in those with stage I and II. The efficacy of surgical treatment is to be improved by a combined-modality treatment. In stage III patients, who are more frequent than others, radical radiotherapy alone or in combination with chemotherapy is applied. Results of clinical trials report patients of relatively good general condition benefiting from combined-modality therapy. Palliative radiotherapy is to be applied in patients with stage IV non-small cell lung cancer. On the other hand, in patients with small cell lung cancer chemotherapy is the primary modality treatment. When the disease is limited to the lungs, the aim of radiotherapy is to optimize local control of the primary tumor.

Local tissue air ratio in an anatomic phantom for 60Co total body irradiation.

Tissue-air ratio (TAR), as the basic dosimetric function, is not ideally applicable to all important locations in total body irradiation (TBI) dosimetry because it generally refers to central ray measurements. We therefore introduced the local TAR which depends on the specific distribution of the scattering centres around the location of interest. Local TAR measurements were performed in an anatomic water phantom, produced by a sculptor, representing a patient during TBI in the real treatment position. A comparison has been made between TAR values, defined on the beam's ray at different locations in the anatomic phantom and cubic phantoms of different size. The local TAR values in the anatomic phantom, having more realistic outer surface curvatures, are lower by a few percent in most locations. We consider these values more accurate and better applicable to TBI conditions than those obtained in cubic water phantoms, even if the volume of the phantom is adapted to the particular side of the body.