Patient doses and dosimetric evaluations in interventional cardiology

Interventional cardiological examinations may be associated with excessive radiation exposures which may cause skin injuries and higher probabilities of stochastic effects. Dose–area product (DAP) and skin doses of 325 patients were measured using alternative dosimetric techniques for different cardiological examinations. Data were collected from five different systems with the involvement of 11 cardiologists. All these dosimetric information has been collected separately for each of 10 projections together with the exposure parameters of X-ray systems. Mean DAP values measured with a transparent ion chamber were 49.1Gycm2, 66.8Gycm2, 106.9Gycm2 and 124.7Gycm2, respectively, for coronary angiography (CA), percutaneous transluminal coronary angioplasty (PTCA) or stent (PT-SI), coronary angiography and/or PTCA and/or stent (CA-PT-SI), and ablation examinations. Radiochromic films, thermoluminescent dosimeters (TLD) and point measurement of air kerma (AK) were carried out for skin dose assessments. Skin doses of 23 patients measured with radiochromic films were found to be between 2Gy and 6Gy. Although the complexity of the procedures was the major reason for these excessive doses, considerable contributions of high X-ray output of some fluoroscopy units were also noticed.

In addition to the direct measurement of DAP, alternative DAP values were also determined from the skin dose measurement techniques; exposed areas were summed on digitized radiochromic films in one technique, The product of AK reading with X-ray field size measured at the patient entrance using slow X-ray films was taken as another DAP.

Good correlations were found among the DAP results and also between the entrance skin doses calculated from AK measurements and direct DAP readings (R2=0.91). A trigger DAP value of 130Gycm2 for the 2Gy of skin doses was derived from this relationship.

Collection of dosimetric data for each projection was also investigated regarding a possible standardization of clinical techniques; in the case of coronary angiography examinations LAO 45 and RAO 30 were found as the dominant projections which may also simplify the dosimetric technique.