Investigations into radiation exposure of X-ray diagnostic examinations have been carried out. Within the scope of the project different methods of constancy tests have been compared and long term analyses have been accomplished.
Developed in the 1985/1989 Radiation Protection Programme, have been compared with examination standards of a number of European countries. The resulting variation of parameters is determined. Results show with respect to different groups of organs that the conformity is reasonably good.
In general different constancy tests have been established for film development and for X-ray units. For film development the so called conventional sensitometric/densitometric methods and the visual (alternative) methods are in use. The conventional methodsall work on the same principle, but differ considerably in their effort of electronical analysis and equipment with respect to comfort and cost. However, all of the methods and devices are suitable when used carefully and critically.
The constancy of film development has been tested daily for 20 different pieces of equipment. Within an arbitrary period of 2 months (43 workdays or 860 tests) 12 serious malfunctions have been detected (1.5% of all tests).
Serious variations have been found at the so called acceptance test, when comparing our results to those indicated by the manufacturer. This final technical check of the equipment before routine use is extremely important, in order to put the equipment into a well defined condition.
Special X-ray examinations gain more and more in significance and contribute to the total population exposure because of either high specific radiation exposure or increasing frequency of the examination.
The digital subtraction angiography (DSA) has rapidly developed in the past few years. The radiation exposure drastically depends upon concentration of contrast medium, type of injection and type of equipment (pulse mode or fluoroscopic mode). Compared to conventi onal angiography the radiation dose level increases by a factor of about 2 using DSA. The average absorbed energy has been determined to be 100 mJ per examination.
Interventional radiology, ie percutaneous transluminal angiography (PSA) is becoming more and more used, too. Independent of technique (balloon, laser, rotor, lysis), all of the examinations are performed under X-ray control. The average absorbed energy for balloon dilation has been determined to be 75 mJ per examination.
Investigations about the frequency of the examinations are not available yet.
The advantages of digital luminescene mammography are believed to be lower patient exposure and the possibility of digital image processing. Basic requirement for the introduction of this method, however, is the visualisation of objects of 0.2 mm in diameter.
A comparison of 50 digital and conventional mammographic examinations using ROC analysis is in progress.