273. Ottimizzazione dei protocolli in angiografia

Abstract

Purpose In reducing dose in angiography, one of the chance one has is knowing the impact of each parameter or operational mode within a protocol in order to make the right balance between dose and image quality. Methods PMMA plates of dimensions 25 cm × 25 cm, and different thicknesses in order to get a total thickness of 20 cm. At the middle, we put a Leeds TOR 18-FG test object, positioned at the isocenter of the machine. A ionization camera (RadCal) in contact with the PMMA plates was used to measure entrance air dose simultaneously with image acquisition. We evaluated: high contrast spatial resolution (bar-patterns), SNR in the second circle calculated as: SNR = ( BG - ROI ) ( STD BG 2 + STD ROI 2 ) 2 where: BG and Roi are the mean value of the pixel in the region of interest located in the background and in the second circle respectively, and STD BG and STD ROI are the relative standard deviation, and finally the figure of merit (FOM): FOM = SNR 2 ED where ED stands for entrance dose [1] . Results we uzed this method to evaluate two different angiogranphic systems: A and B. In the first one we compared different automatic exposure preferences both for fluoroscopy and fluorography, in the second one we compared low dose protocols to normal dose ones both in cardiac imaging and in DSA body. Conclusions For A: in fluoroscopy RDL + mode is the best in terms of SNR and FOM respect to RDLstd and IQstd; in fluorography there is only the IQstd mode, but the low detail setting has a FOM that is comparable to normal detail setting, at half the dose. For B: Card low dose protocols have the best FOM values, especially using a FOV of 32. In the case of DSAbody low dose the dose more then half the dose obtained with the standard protocol, but the SNR is not degraded and the FOM is even higher.