IPEM Topical Report: an evidence and risk assessment based analysis of the efficacy of tube and generator quality assurance tests on general x-ray units

Abstract

This work aims to assess the efficacy of x-ray quality assurance tests undertaken on fluoroscopy units in the UK. Information was gathered on the results of dosimetry and safety tests recommended by the reports of the Institute of Physics and Engineering in Medicine, and those additionally undertaken by medical physics departments. The assessment of efficacy considers the frequency with which a test result breaches the remedial level or other relevant threshold where applicable. The third quartile of those results exceeding the remedial level or threshold is used to estimate the severity of such a breach in terms of potential impact on patient dose and image quality. A risk assessment approach is then used to recommend to what degree, if any, the test should be included in an ongoing test regimen. Data was analysed from 468 testing sessions to 336 unique fluoroscopy units throughout the UK. Across all tests, the rate with which the remedial level was exceeded varied from 0-29.5%, with severity ranging from little or none to major degradation to image quality or significant increase on population dose. Where possible, the data has also been used to produce representative ranges for the results of dosimetric tests. These could be useful as an up to date comparator for those sites considering the purchase of or commissioning new equipment. Overall the results indicate a wide range for the efficacy of those tests undertaken at present; this can be used to review local test protocols and to inform future changes to national guidance in the UK. The results also highlight some tests where measurement technique varies significantly throughout the UK, making any valid comparison difficult. This may indicate a need for further guidance on how best to undertake these tests.

AAPM Task Group Report 272: Comprehensive acceptance testing and evaluation of fluoroscopy imaging systems

“…On an annual basis, a reduced number of physical parameters may be evaluated in addition to the parameters that must be assessed to meet regulations, such as the alignment and congruence of the radiation field and the image receptor. Two Institute of Physics and Engineering in Medicine Topical Reports discuss the parameters to be evaluated and the suggested frequency of assessments in further detail 41,42 …”

“…Two Institute of Physics and Engineering in Medicine Topical Reports discuss the parameters to be evaluated and the suggested frequency of assessments in further detail. 41,42 The total time required to perform the acceptance tests described in this document will vary substantially depending on the modality. For the most intensive testing procedures on the most complex units (e.g., cardiovascular and visceral interventional units), the physicist should plan for 12-16 h of testing per imaging plane.…”

Radiographic and fluoroscopic X‐ray systems: Quality control of the X‐ray tube and automatic exposure control using theoretical spectra to determine air kerma and dose to a homogenous phantom

“…An unintentional increase in the dose may occur due to changes in AEC during equipment servicing or because of dose creep resulting from nonoptimal use of AEC 6,7 . However, dose increase due to X‐ray system errors that lead to discrepancies between the nominal and true values of the exposure parameters are rare 8 . The dose to the image detector and the dose‐area product (DAP) are often measured for QC purposes.…”

“… 6 , 7 However, dose increase due to X‐ray system errors that lead to discrepancies between the nominal and true values of the exposure parameters are rare. 8 The dose to the image detector and the dose‐area product (DAP) are often measured for QC purposes. The DAP is also used in national reference values and must therefore be as accurate as possible.…”

The influence of patient size on the overall uncertainty in radiographic dose audit

“…This is easily managed when ionisation chambers are used but is difficult to achieve when dose data is captured using kerma area product (KAP) meters, as is usually the case in Western Europe. IEC standards (IEC 2020) recommend that the overall uncertainty associated with field class KAP meter measurements in radiography should below 25% but errors in excess of this have been reported (Honey et al 2018).…”