For a convention general radiography room and automatic processor outline a quality assurance programme. Justify your choice of tests to be carried out
...d within the contract are met. The tests that are carried out by members of the QA team within the radiography department are described as routine or monitoring tests and are carried out designated intervals within the imaging department normally every 1-2 months. They are done to detect significant changes in performance of the machinery during use and to ensure the equipment is safe to use. Within any imaging department the QA team may have numerous monitoring/routine tests which have to be carried out each month, all of which having to meet performance guidelines, consisting of two levels. The remedial level, which is the level of performance at which remedial action needs to be taken, in this case equipment can continue to be used but certain restrictions may need to be placed. The second level is the suspension level this shows that the machine is seriously under performance and the equipment has to be withdrawn from clinical use immediately. In a general x-ray room many parameters have to be inspected, which include the radiographic x-ray tube tests and the radiographic table and bucky tests. I shall firstly examine the tests performed on the main x-ray tube within the room; there are three main tests that can be carried out, one of which being the beam quality test. The half-value layer (HVL) test and checks of kVp accuracy and reproducibility can assess beam quality. The "half-value" layer or HVL as it is known is the most frequent used factor for describing both the penetrating ability and the penetration through specific objects. It thickness of an attenuator normally aluminium required to reduce an initial, un-attenuated exposure to one-half of its original value. Following regulations for diagnostic x-ray equipment, minimum acceptable half-value layers at the noted kVp values are kVp: mm Al: 50 1.2 80 2.3 120 3.2 If a half-value layer is measured than a value less than the above value would indicate that the x-ray beam is too “soft” therefore there are too many non-productive low-energy photons present. KVp accuracy and reproducibility can be measured most easily using a kVp meter. A kVp meter works on the principle that the intensity of a x-ray spectrum drops with added filtration. A typical kVp meter contains built-in filters which may be in the form copper) with a diode or ion chamber-based detector. The ratio of the unfiltered and filtered output difference is proportional to the kVp. Following guidelines any results for kVp should be within +/- 5% of the set kVp. Kvp should be replicated according to the following tolerance (max measured value –min measured value) should be less than (+/-5% of the average measured value). Assessment of focal spot size is another quality assurance test that should be carried out on radiographic equipment, a small focal spot size is used to obtain x-ray images with the minimum amount of blur. In using a small focal spot it tends to concentrate heat and gives a load on the focal spot area. If the quantity of heat delivered during an individual exposure exceeds the track capacity, the anode surface may melt, therefore it is necessary to measure the focal spot size and compare it with the original focal spot size with the machine. Another test that can be carried out on the main x-ray tube is radiation output The mR/mAs relationship should be linear and acceptable, the kVp is measured by the kV meter and must be within the acceptable range this being + 10% of kVp indicated by the machine. As a result the exposure dose must be within acceptable limits. Within the general radiographic imaging room there are other pieces of equipment that must undergo quality insurance tests these include the table bucky and the wall mounted bucky, both of which undergo the same or similar tests and therefore I shall look at them as one piece of equipment. The first parameter that I shall look in testing the bucky equipment is beam alignment and collimator accuracy. To perform this certain type of test a beam alignment test tool is used, this device provides a simple means of determining, if the x-ray beam is perpendicular to the image receptor and centred with respect to the light field. The test is performed as if an improper central ray alignment is present the radiographic image that is produced will be distorted. Another test, which can be carried out on this equipment x-ray/light field bucky alignment, this test is carried out to ensure that the x-ray beam is centred to the bucky. These two tests would be carried out regularly between 1-2 months, and are describes as the basic tests required for quality assurance testing as they are quick and easy to perform and no expertise is needed. It is essential to obtain consistent good quality radiographs this is only possible by ensuring automatic processors function to a set standard. Film/processor quality assurance can be performed quickly and easily and should be carried out every day on the processor that is used, preferably at the beginning of each day. Quality assurance tests are carried out o the processors, to ensure that the processor is operating at peak performance and optimum temperature and also to identify any possible problems so that corrective action may be taken ensuring that the processor remains at peak performance. An effective film/ processor QC program will evaluate several "control" variables, which include film speed, film contrast, film base and fog, developer temperature, dryer temperature, developer pH. Film speed, contrast, and base and fog can be assessed by film sensitometry. A sensitometer is used to produce a sensitomeric filmstrip with a series of up to 21 densities ranging from 0.2 to 3. Film sensitometry involves exposing a controlled film supply to a controlled, graduated light source using a device called a sensitometer. The sensitometer is used in to the specific film type to establish a series of steps that can be measured each day after the test film is processed. These measurements are made using a device that measures film density, a densitometer. Densomiters automatically read the relative density of the various steps on the film by measuring the quantity of light passing through the film, the more light that passes through the film the lower the resultant density. The results, which are found, are plotted on graph and compared to a characteristic curve from a trouble-shooting chart. If the graph produced form the results is obviously different to the normal characteristic curve...