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New Image Processing and Noise Reduction Software Reduces Radiation Dose during Complex Endovascular Procedures
Background: Radiation exposure of surgeons and patients during complex endovascular procedures(CEPs) is largely based on patient characteristics, case complexity and the interventionalist’s knowledge of good operating practice. Phillips Health Systems has introduced a new image processing system (Allura Clarity) for interventional fluoroscopes that claims to maintain image quality at lower radiation doses using noise reduction algorithms. The aim of this study is to determine whether surgeon and patient radiation dose during CEPs is decreased after the implementation of this new operating system.
Methods: Radiation dose to operators, procedure type, reference air kerma(RAK), kerma area product(KAP), the relative position of the operator to the x-ray source and patient BMI was recorded during CEPs on two Philips Allura FD 20 fluoroscopic systems: one with and without Clarity. Operator dose during CEPs was measured using optically stimulable, luminescent nanoDot(Landauer Inc) detectors placed outside the lead apron at the left upper chest position. NanoDots were read using a Microstar ii medical dosimetry system. For the CEPs in the Clarity group, radiation dose to surgeons was also measured by a personal dosimetry system(DoseAware, Philips, Healthcare), which measured H_P(10) dose equivalent at a tissue depth of 10 mm. Side by side measurements of DoseAware and nanoDots for group B allowed for cross calibration between systems. Operator effective dose was determined using a modified Niklason algorithm. Relative patient radiation exposure was inferred from RAK and KAP. System logs and radiation structured dose reports were reviewed for fenestrated endovascular aneurysm repairs(FEVARs) to identify changes in operating practice that may have affected dose(fluoroscopy times, number of acquisitions) with and without Clarity. A one sided Wilcoxon rank-sum test was used to compare groups for radiation doses, RAKs and operating practices for each procedure type. Statistical significance was determined at a P <0.05.
Results: 234 CEPs were included in the analysis; 95 performed without Clarity and 139 with Clarity. There was no difference in BMI between groups. Radiation dose to the patient and the primary and assistant operators was decreased in the Clarity group compared to the nonClarity group in all categories(Table). For all cases, the patient dose(RAK) and the primary operator dose was significantly decreased by 60% in the Clarity group. Detailed analysis of FEVARs, demonstrated that the fluoroscopy time and number of acquisitions was not significantly different between groups, however the fluoroscopy dose decreased by 50% and the fluorography dose was reduced by 65% in in the Clarity group. (P<0.05).
Conclusion: The Allura Clarity system reduces the patient and primary operator’s radiation dose by more than half during complex endovascular procedures. This feature appears to be an effective tool in lowering radiation dose while maintaining image quality.

	Without Clarity					With Clarity
Case Type	n	RAK mGy	KAP Gycm2	Eff 1 μSV	Eff 2 μSv	n	RAK mGy	KAP Gycm2	Eff 1 μSv	Eff 2 μSv
Cerebral	3	590	133*	2.2	0.2	11	240	49	1.6	0.4
Visceral	9	1580	243	6.3	5.0	18	670	121	4.8	3.8
Embolization	13	3530*	477*	16.8	9.1	8	720	173	7.7	6.4
EVAR/TEVAR	12	1110*	198	6.2*	2.9*	14	560	157	2.1	1.2
FEVAR	16	4970*	601*	21.5	13.2	25	2580	372	14.1	7.1
Fistulagram	9	80*	22	1.7	0.7	13	50	17	0.6	0.3
Lower extremity	33	410*	113*	8.4*	1.8	50	200	49	2.5	1.1
Total	95	1780*	260*	10.4*	4.6	139	750	131	4.9	2.6

* Denotes statistical significance
Eff ¹ : Effective dose, primary operator
Eff ² : Effective dose, assistant operator