Levels and names of tests

 
According to the literature, there is an approximate international consensus in categorization and names of QC tests. Generally, three different levels of test are distinguished.
1. Acceptance test (in German: Abnahmeprüfung): a detailed performance assessment, to be performed before putting the equipment into use. It demands special measuring instrumentation and special expertise (i.e. physicist or engineer). In must be clearly distinguished from the commissioning (handing the equipment over to the user) which is performed by the installing company, in presence of the purchaser. (In principle, however, it is possible that some results of the latter – in case of appropriate regulation and presence of independent external experts – may be accepted also as parts of the acceptance testing.) The main aim of acceptance testing is checking the compliance of the equipment with the contract and/or manufacturer’s specifications (and local regulations, if applicable). Its other aim is determining of the so-called base levels for further QA, i.e. initiating a QA programme, for assuring long, safe and optimum performance of equipment. Acceptance test is therefore a single testing.
2. Status test (in German: Zustandsprüfung): further full performance testing. It is required according to the local regulation, in Hungary yearly and after major servicing (it may mean e.g. change of the X-ray tube, X-ray image intensifier or DR detector). In case of mammographic equipment in most countries the frequency is twice a year. In Hungary, it is task of independent accredited testing organizations. Main aim of status test is determination of changes of parameters, so it is basically repeating of all measurements made during the acceptance test. In other words, status test is a full performance measurement equivalent to an acceptance test. Nevertheless, some simplifications are possible, e.g. checking of documents and measurement of leakage radiation or tabletop attenuation can be omitted (if these parts were not changed). Its need for measuring instrumentation and expertise equals to that of acceptance testing.
3. Constancy test (in German: Konstanzprüfung): simpler daily, weekly or monthly checks, to be performed by the licensees (users) themselves, aim of which is checking constancy of the performance.
There are some countries where terms used in a little bit different manner but dividing into three levels is essentially the same. So in Great Britain, status testing and constancy testing together is called “routine performance testing” and within it two grades are distinguished, according to the differences in needed frequency, instrumentation and expertise. In Germany, status test is also called “acceptance test” and it is obligatory in every five years, while instrumentation and expertise level of yearly constancy tests is also very high.

In description of the tests frequently used terms are remedial level and suspension level. Remedial level means a difference from the expected (so-called base) value which is a reason for a correction, to be made by an authorized expert but it is not high enough to be a reason for prompt suspension of the use. Suspension level means a deviation which is absolutely unacceptable and gives a reason for prompt suspension of the use of the equipment. After servicing and adjustment constancy test shall be performed immediately. If this test shows a deviation exceeding the suspension level again, discarding of the equipment is to be considered. Results of all tests shall be documented and stored in a retrievable manner, for further possibility of comparison.