Benefit, terms and first steps of technical quality assurance

   Book for Physicists  »  Quality Assurance  »  Technical Quality Assurance and Safety of Diagnostic Radiology Equipment  »  Benefit, terms and first steps of technical quality assurance

Introduction

 
Nowadays dealing with quality aspects, including quality assurance is not only a custom but – sooner or later – it is forced upon all manufacturers and services, either by legislation or through competition. Within the healthcare system, radiology is the most technology-dependent discipline. That is why physical-technical aspects of quality assurance are of extraordinary importance in radiology. Quality of equipment is closely connected also with safety, therefore regulation and standards relating to safety of diagnostic radiology equipment are also outlined here.
Quality assurance (QA) may be full or partial (e.g. production QA). This paper does not deal with full quality systems of hospitals or radiology departments but solely with physical-technical quality assurance of diagnostic radiology equipment and devices for radiologic image acquisition, enhancement, assessment and displaying. This will be called hereinafter technical QA (of radiology equipment). Sometimes it is called in the literature also QA/QC or QA/C (QC = quality control).

Benefit, terms and first steps of technical quality assurance

 
It is a very important aim that diagnostic radiology equipment operates correctly during a possible longest lifetime, having optimum diagnostic imaging with minimum patient and staff doses, moreover, and safe operation. Concisely, it can be said that good equipment is a – not sufficient but – necessary condition of good radiology. It is a long, international experience that “good equipment” can be assured only by continuous technical QA. The mentioned aims can be realized only by regular professional measurement of technical parameters and – in the meantime – checking of their constancy, even with the simplest methods (i.e. the so-called routine performance testing). According to experience, it is also practical to perform QC tests independently of manufacturers and service firms. Money spent on QC is recovered many times: in higher level of diagnosis, in safety, in saving material, energy, working time of equipment, working time of staff, and especially of patient doses. Realizing it, European Union made technical QA obligatory for member states in its directive 97/43/Euratom. Costs of the tests should not be considered as expenditure imposed on the healthcare system as its benefit is much higher than its cost is.
In radiology departments, not running QA, range of doses for a given radiography examination may extend even two orders of magnitude, and proportion of repeated radiograms may reach even 17 per cent. Of course, a radiogram taken with too low dose is also useless, therefore unnecessary radiation exposure is caused not only by overexposure. In departments introducing QA, dose ranges decreased to 3 to 5 while proportion of repeated exposures to about 5 per cent.
Simply to say, the tests (regular checks, measurements, inspection and functional testing, including testing of the status of equipment, image quality, patient dose and evaluation of these parameter) are generally known as quality control (QC), while together with the so-called corrective actions and its management it is called (physical-technical) quality assurance (QA) (of the equipment).
Some spontaneous “quality assurance” has been since a long time. In radiology, it means that if a radiologist or a radiographer realized a decreased image quality, he/she tried to find its cause and tried to correct it. A further step is, when also prevention appears, e.g. change of processing chemicals after passing a given period, instead of waiting for a noticeable performance decrease.
However, it begun to be realized in the 60-ies only that an X-ray equipment can produce – with the reasonably achievable low dose – an image of appropriate quality only if its setting are accurate enough, i.e. actual values of the parameters equal to the set values, within given tolerances. As existing of this condition can be checked by measurement only, there started the initiations for performing co-called quality control measurements. In this progress the leading country was England.