PSD has been obtained using a Radiation Dose Index Monitoring (RDIM) software NEXO[DOSE]^® (Bracco Injeneering SA, Lausanne, Switzerland), which permitted to manage patient and dosimetric data retrospectively [5] and provide a tool for estimate PSD and skin dose map for angiographic procedures. To estimate the PSD, the software uses exposure parameters (primary and secondary angles, source to isocentre distance, kV, KAP, air-kerma, additional filters) taken from the Radiation Dose Structured Report (RDSR) and other information specific to each angiographic system (the attenuation of the table and the correction factor for reported KAP values). The tool had been previously validated on geometrical phantom and patients, using Gafchromic^® films measurements.

NEXO[DOSE]^® also allowed us to easily obtain the distribution of procedures and identify the most critical ones from a dosimetric point of view.

The interventional radiological procedures with the highest exposures have been considered (Fig. 2): uterine fibroid embolisation (UFE), prostatic artery embolisation (PAE), transarterial chemoembolization (TACE), transjugular intrahepatic portosystemic shunt (TIPS) and endovascular aneurysm repair with endoprosthesis (EVAR). All these interventional radiological procedures were performed in three angiographic rooms with two Philips Integris Allura FD20 and a Siemens Artis zeego. In the period between January 2016 and May 2019, we retrospectively analysed the exposures and skin dose values of 500 exams, using NEXO[DOSE]^®. For each procedure, KAP, K_a,r and PSD values were collected. 

A regression analysis has been performed to investigate the correlation between the estimated PSD and K_a,r or KAP (Fig. 3-5).

PSD and KAP are weakly correlated: therefore, it is difficult to find a correct procedure-specific trigger level for the KAP. The dose index K_a,r better correlates with the PSD so it could be used to define trigger levels.