This single center retrospective study was reviewed and approved by the Institutional Research Review Board. Informed written consent for every procedure was obtained in all cases from the child’s parents or legal representative. Data from 09/2017 to 09/2019 were retrospectively analyzed using dose monitoring software. We evaluated n=98 consecutive pediatric patients age< 16 years (mean 6 y; 3rd quartile 12,5 y).
Among procedures were included: Central Venous Catheter placement n=58, Retrograde Wedge Portography (RWP) n=35, Biliary catheter change/Cholangiogram n=21, Bilioplasty n=17, Percutaneous transhepatic biliary drainage placement (PTBD) n=12, Transjugular Hepatic veins flebography n=9, Hepatic arteriography/embolization n=7, Percutaneous transhepatic portography n=4, Hepatic artery angioplasty n=3, TIPS revision n=3, TIPS n=1, others (n=21). TABLE 1
All procedures were performed in a unique equipment, a monoplane flat-panel-based detector angiographic suite in posterior-anterior or oblique projection when required. Protective aprons (0.5 mm lead equivalent) were always placed under patients at pelvis level to protect the child’s gonads.
Although Image Gently campaign [4-5] recommended to perform all procedures that did not require fine image detail without anti-scatter grid, in order to have image fine detail, more complex procedures included in this study (RWP, PTBD in biliary strictures, Hepatic arteriography/embolization, Percutaneous transhepatic portography, Hepatic artery angioplasty, TIPS and TIPS revision), were all performed with anti-scatter grid left in place. The equipment table was kept as far from the source as possible (to reduce skin entry dose), and close to the image detector. The “Last Image Hold” function was used to minimize radiation exposure such as fluoroscopic images storing, tight collimation restricting the field of view only to the liver and no or minimum magnification whenever possible were used during procedures.
The fluoroscopic trajectory we decided to choose to perform procedures, among the five different trajectory available, used only 50% as threshold dose optimized to produce high contrast resolution images. In addition, because our equipment allows the choice between adult and pediatric settings for the same auto exposition trajectory, we decided to set it as “pediatric” so to adjust kV and mA down maintaining the same dose threshold and the same images characteristics. Phantom tests, performed to understand if difference can occur setting the fluoroscopy protocol as a pediatric, showed a lower Dose Area Product (DAP) (-13%) maintaining the same images characteristics. Also, 7.5 fluoroscopy frames/sec, the lowest for that equipment, with low image detail level were routinely employed. Fluoroscopy frame/rate was never modified; instead magnification and normal image detail level were used only in critical steps of some procedures.
Digital Subtraction Angiography (DSA) was used with 2 frames/sec with low image detail level. High frame rate, 4 frames/sec, were used only in critical procedures.
At our hospital, dose monitoring is integrated with the RIS and it gave us access to a summary of dose data by type of sequences, Fluoroscopy or DSA acquisitions. It allowed us filtering data by time, study description, fluoroscopy protocol chosen and patients’ age. Furthermore, the Incidence 2D Map was available indicating the value and the position of the point with the highest cumulative Air Kerma (AK). A AK dose threshold of 2 Gy was predefined by the manufacturer as “alerts” dose and, if patient exposure exceeded this predefined thresholds, a notification alerted us.
All acquisition parameters [frame rate, tube voltage (kV), tube current (mA), spectral filtration (mmCU)], DAP (given in Gy.cm2), AK (given in Gy), fluoroscopy time (FT, minutes), number of magnifications, source-to-detector distance (SID) and table vertical position (given in centimeters from the isocenter toward the focal spot) for all interventional procedures were automatically transferred during each procedures to the dose monitoring system and they could be viewed in real-time patients by patients. Statistics data such as mean, minimum and maximum were automated calculated by the software.