Evaluation of therapeutic dose linear accelerator out-of-field using different techniques radiation

Abstract

Prilikom puštanja u rad terapijskog linearnog akceleratora dozimetrijska mjerenja se rade samo u zračnom polju i ti podaci se unose u TPS (sistem za planiranje), dok dozimetrijski podaci izvan zračnog polja nisu dobro dokumentovani. Neminovno je da dijelovi tijela izvan zračnog polja budu izloženi određenoj dozi zračenja rasijanog u tijelu pacijenta, akceleratorskoj glavi, kao i u samoj prostoriji. Razvojem tehnika isporuke doze pomoću kojih imamo mnogo bolju konformalnost, ali isto tako imamo više monitorskih jedinica čime se produžava vrijeme tretmana, a samim time izloženost tijela nižim dozama zračenja. Takođe, koristimo više polja pod različitim uglovima (IMRT) ili puni luk (VMAT). Sve ovo utiče da veća zapremina normalnog tkiva bude izložena nižim dozama zračenja. Cilj ovog rada je da se procijeni vrijednost doze izvan zračnog polja za tretmanske planove (3DCRT, IMRT i VMAT) napravljenih u Eclipse 13.6 TPS (Varian Medical Systems) koja je isporučena pomoću Clinac DHX (Varian Medical Systems) linearnog akceleratora. Mjerenje je rađeno u Thorax Phantom-u (CIRS) pomoću jonizacione komore na udaljenosti od ivice polja u rasponu od 1,75–15,75 cm.When commissioning therapeutic linear accelerator dosimetric measurements are made only in the air field and these data are entered in TPS (treatment planning system), and dosimetry data out-of-field are not well documented. It is inevitable that parts of the body out-of-field to be exposed to a certain dose of the scatter radiation in the patient's body, accelerator head, as well as in the room. The development of technique delivery doses with which we have a much better conformity, but also we have more of monitor units that serve to prolong the treatment time, and thus the exposure of the body lower doses of radiation. Also, use more fields at different angles (IMRT) or full arch (VMAT). All this affects the larger volume of normal tissue is exposed to lower doses of radiation. The aim of this study is to assess the value out-of-field dose for treatment plans (3DCRT, IMRT and VMAT) made in Eclipse 13.6 TPS (Varian Medical Systems) that is delivered using CLINAC DHX (Varian Medical Systems) linear accelerator. Measurement was conducted in Thorax Phantom-in (CIRS) using ionization chamber at the distance from the edge of the field in the range of (1.75 - 15.75) cm