An experimental study on using a diagnostic computed radiography system as a quality assurance tool in radiotherapy

Abstract

The advent of improved digital imaging modalities in diagnostic and therapy is fast making conventional films a nonexistent entity. However, several radiotherapy centers still persist with film for performing quality assurance (QA) tests. This paper investigates the feasibility of using a diagnostic computed radiography (CR) system as a QA tool in radiotherapy. QA tests such as light field congruence, field size verification, determination of radiation isocentre size, multileaf collimator (MLC) check and determination of isocentric shift for stereotactic radiosurgery (SRS) were performed and compared with film. The maximum variation observed between CR and film was 0.4 mm for field size verification, -0.13 mm for the radiation isocentre size check, 0.77 for MLC check and -0.1 mm for isocentric shift using the Winston Lutz test tool for SRS QA. From these results obtained with the CR it is concluded that a diagnostic CR system can be an excellent cost-effective digital alternative to therapy film as a tool for QA in radiotherapy.

Isocenter verification for linac‐based stereotactic radiation therapy: review of principles and techniques

“…In addition, it is not possible to modify the properties of film images to improve contrast. ( 23 ) Dust or marks on the film can lead to spikes in images. ( 40 ) The film results for Winston‐Lutz test are not quantitative, ( 26 , 52 , 59 ) and are based on manual evaluations ( 24 , 34 ) and visual inspection — which makes them highly dependent on the skills of the observer.…”

“…EPIDs have many advantages over films such as the ability to re‐use, to provide digital images, to permit easy and quick data transfer, and to archive. ( 23 , 37 , 52 , 58 ) The digital format of EPID images enables contrast enhancement ( 65 ) which is very helpful in image analysis. It is important to note that EPIDs are currently included in the structure of modern linear accelerators and require no time‐consuming setup.…”

“…The shifts in isocenter were manually determined on the magnified images. ( 23 ) The accuracy of the method could be affected by the uncertainty in the position of micro‐MLC leaves.…”

“…( 4 , 10 , 23 ) There are several sources of uncertainty in stereotactic treatment systems such as errors in patient positioning, target localization, and dose delivery. ( 20 , 24 ) It is practically impossible to achieve perfect alignment mainly due to the presence of several geometric errors in the system.…”

A simple quality assurance test tool for the visual verification of light and radiation field congruent using electronic portal images device and computed radiography

“…Also with the drive toward film-less and chartless radiation therapy environment, there is a need to develop ways to carry out this important QA check. To this effect, there have been proposed techniques to use computed radiography (CR) system [8,9], photodiodes [10], diodes arrays and electronic portal imaging devices (EPIDS). So far, several test tools and appropriate software have been developed to quantitatively study light and radiation field congruence using EPIDS [4-6,11].…”