Some characterization tests for an extrapolation chamber in CT standard beams in a specific chamber depth

Maysa Costa De Castro

doi:10.15392/bjrs.v8i1a.1085

Abstract

The use of Computed Tomography (CT) for diagnostic images has been growing due to technological advances of this equipment. Therefore, there is a concern regarding the dose received by the patients undergoing this procedure, and this procedure needs to be performed with the highest precision and accuracy possible.The radiation detector used for CT beams is a pencil-type ionization chamber. However, there is no primary standard system for this kind of radiation beam. In this work a homemade extrapolation chamber was used to establish a CT primary standard [1]. This detector was tested for low-energy radiation beams and showing results within the internationally acceptable limits [2].This work had the objective to study the response stability of an extrapolation chamber, as well as obtaining the energy dependence and the angular dependence in standard CT beams of the Calibration Laboratory of IPEN (LCI).

Highlights

The use of Computed Tomography (CT) for diagnostic images has been growing due to technological advances of this equipment [1,2,3]
A homemade extrapolation chamber was tested in this work to establish a CT primary standard for calibration laboratory beams [4,5]
The extrapolation chamber tested in this work has a collecting electrode of 30 mm in diameter, the entrance window is made of aluminized polyethylene terephthalate with density of 0.84 mg/cm2, and the collecting electrode and guard ring are made of graphite; this chamber was developed at the Calibration Laboratory of Instruments / IPEN (LCI) [6]

Summary

Introduction

The use of Computed Tomography (CT) for diagnostic images has been growing due to technological advances of this equipment [1,2,3]. There is a concern regarding the dose received by the patients undergoing this procedure, because it uses higher radiation doses when compared to other fields of conventional radiology, and this procedure needs to be performed with the highest precision and accuracy possible. For the dosimetry of CT beams, the radiation detector is usually a pencil-type ionization chamber. It presents a uniform response to the incident radiation beam for all angles. There is no primary standard system for this kind of radiation beam. A homemade extrapolation chamber was tested in this work to establish a CT primary standard for calibration laboratory beams [4,5]

Objectives

Methods

Results