Our study demonstrates that the AlluraClarity technology upgrade enables a radiation dose reduction up to one third in patients during AVS compared to the precursor technology Allura Xper without compromising image quality.
It is conceivable that the main reason for a significant reduction of radiation dose after the upgrade using AlluraClarity results from the additional filters of aluminum and copper during DSA and a reduced focal spot size during fluoroscopy. By changing system parameters AlluraClarity renders over 500 different acquisition settings with respect to the particular area of interest. Various studies have already demonstrated the potential in radiation dose reduction using AlluraClarity during intracranial angiography, cardiac angiography, iliac angiography or abdominal angiography (16–19). Apparently, procedural settings during cerebral interventions focus more on the pixel shift feature during steady conditions, as thoracic and especially abdominal settings emphasis more on the motion control feature in order to reduce breathing artifacts (20).
Previous studies of abdominal interventions such as transarterial chemoembolization (TACE) and transjugular intrahepatic portosystemic shunt (TIPS) using AlluraClarity abdominal settings reported dose reduction of > 50% (19, 21). We observed a lower dose reduction of only 28% using the identical AlluraClarity abdominal settings during AVS.
The most important reason for less dose reduction during AVS might be due to its different anatomic region and the complexity of intervention. The most challenging part of AVS remains the reliable cannulation of the right adrenal vein (RAV) (10). Identifying the RAV-ostium from the IVC with 1–2 mm diameters requires increased contrast of the vessel edges and therefore increased radiation dose because of increased fluoroscopy time during the search of the RAV-ostium.
Furthermore, AlluraClarity provides three different levels of fluoroscopy-setups at the operator’s console ranging from low and medium to high dose settings. These changes can be applied differently for each fluoroscopy-run and might change due to individual preferences from operator to operator (Table 2). Unfortunately, these specific individual sub-settings are currently not monitored by the vendors dose reports and could not be tracked retrospectively. The default settings contain the low dose profile, which can be increased individually.
The relative increase in contrast agent used by 10% for additional DSA- or fluoroscopy runs may be caused by the verification of correct catheter placement before and after sampling (Table 3). Our results show a significant radiation dose saving potential after the upgrade to AlluraClarity with a mean DAP decreasing from 235.1 to 170.1 Gy*cm2. Recently the SPARTACUS multicenter trial released comparable mean AVS procedure doses from the identical fluoroscopy system AlluraClarity of 147 (1.1–1186) Gy*cm2 (11).
The main limitation of our study is the variety of different operators involved over 4 years due to its retrospective nature. Although AVS is to be considered as a highly standardized procedure, operators at different skill levels use their personal workflow of intervention during AVS. Evidently, identical and matched operators should have performed the interventions for both groups of patients before and after the technology upgrade. For this study we used our standard AVS-protocol. Busser et al. could already demonstrate potential dose reduction and reduced DSA-runs via intraprocedural CBCT image registration guidance improving the detection of adrenal vein ostia (14). However, this new feature of image registration is currently not practiced at our angiography suite and therefore has not been included in our routine AVS-protocol yet. Further studies should also include CBCT image registration for further radiation dose reductions.
The image quality assessment is a further limitation of the study. Image quality and vessel contrast depend not only from the angiographic system, but also from the applied flow rate during injection and amount of injected contrast agent for each series. We believe that these incongruences regarding procedure workflow apply to both groups and do not result in a systemic bias. Although the image quality assessment had been adopted from well-established previous studies, it remains a subjective tool. However, the image-assessment results demonstrate a good inter-observer-agreement concerning AlluraClarity (k = 0.77) and Allura Xper (k = 0.75).
In summary, we have shown that the new angiographic noise reduction imaging technology significantly decreases the radiation dose during adrenal vein sampling without compromising image quality or increasing fluoroscopy time or contrast volume.