Doses of radiations which use for treatment of malignant diseases

For treatment of malignant diseases use such sources of ionizing radiation which transfer a sufficient therapeutic dose to the tumour into necessary depth for its full destruction with the maximal preservation of surrounding healthy tissues, i.e. which is the basic principle radio therapy of malignant tumours.

Depending on histological structure of the tumour, its sizes and depth the arrangement use following total local doses (SCD) for all course of treatment:

· For destruction epithelial tumours SCD - 50-70 Gy;

· For adenocarcinomes - SCD 70-80 Gy;

· For sarcomas muscular and connectiv-tissual origins SCD - 80-90 Gy;

· For melanomes, osteogenetic sarcomas - SCD 100 - 120 and more Gy.

For the prevention of radio damage of tissues total doses of an radiation exposure divide into separate parts, i.e. fractions. Distinguish following concepts:

· Single basic dose (SORT) — dose which bring to the center for one session;

· Total skin (superficial) dose — a dose which bring on skin for all course of treatment;

· Single skin dose — a dose which bring on skin field for one session.

Ways of leading dose to the center and a rhythm of radiation exposure:

1. Unitary radiation exposure — the planned dose brings to a tumour for one session of an radiation exposure (a preoperative and suboperational radiation exposure).

2. Fractionation an radiation exposure — carry out fine fractions — 2-2,5 Gy every day, 5-6 sessions for a week, duration rate of radiation exposure 4-6 weeks, SCD 60-70 Gy; averages — 3,5-4 Gy, 2-3 sessions for a week (the week dose should not exceed 10 Gy), SCD 50-60 Gy; large fractions — 5-8-10 Gy for a session with an interval from several days about one week (use more often in the started cases with the palliative purpose).

3. The intensively-concentrated rate 5 and more Gy during 5-6 days every day, achievement of the total absorbed dose 30-40 Gy carried out by surgical intervention.

4. The split rate of radio therapy — is spent fine and average fractional doses for the increase of tolerance of normal tissues; occurrence of radio reaction after leading half prescribed dose temporarily for 2-4 weeks interrupt an radiation exposure and after that continue it. The split rate improves result and is not accompanied by the expressed biological effects of normal tissues. Owing to destruction of tumoural cells and improvement of blood circulation in a tumour it is marked reoxigenation cells which were in a condition of hypoxia’s and anoxia’s. Reoxygenation to a tumour promotes its increase radioaffection during the following after break of radiation exposure.

5. The continuous radiation exposure — is carried out incorporated RNP for treatment of plural metastases in a bone (radioactive phosphorus), a cancer of a thyroid gland (¹³¹ І), etc.

Дата добавления: 2015-11-16