Study the Quality Assurance of Superficial Radiotherapy X-ray Machine using some Techniques

Abstract

The aim of the present paper is to investigate some factors affecting on quality assurance of superficial radiotherapy x-ray such as reproducibility of dose out put, linearity, reference, entrance and some skin cancer doses were measured for hand, face and nose. Examinations of these factors are studied using Farmer dose master connected with 0.6 cc ionization chamber which was placed on the couch inside the selected field and contacted with an applicator to avoid any air gap inside a field size and 10 exposures were made. The measurements were carried out using an operating condition such as 50kV, 90mAs, 15mA 0.10 min, 6 sec. The tolerance limit for the reproducibility is equal to 0.2% , which is lower than the tolerance limit as mentioned. in American Association of physics in Medicine, AAPM . The relative Error for entrance skin dose equals 3%. The quality assurance tests of superficial radiotherapy x-ray machine are measured and compared with the international tolerance.

Key words: Quality Assurance, Farmer dosemaster. .0.6 cc ionization chamber

Introduction

The principle goal of quality assurance of superficial x-ray machine is obtained accurately and timely assessment. The secondary goal is to maximize of radiation exposure and obtain high radiation quality. This can be assess by performance the x-ray machine by optimum operating parameters such as reproducibility of dose out put, linearity, Reference , Entrance and Exit dose measurements according to code safe of practice for use x-ray in medical diagnosis (NRL, 1994). [1].

Many associations reported work concerning quality assurance of superficial x-ray machine like , AAPM, [2,3] that describes quality assurance protocol for superficial radiotherapy x-ray equipment at the therapeutic technologist level. American Association of Medical Physicists in Medicine ~AAPM, [4] presents a new protocol, developed by the Radiation Therapy Committee Task Group 61, for reference dosimetry of low- and medium energy x rays for radiotherapy and radiobiology (40 kV(4)