Semmelweis University Budapest, Heart and Vascular Center, Hungary
Purpose: Digital Variance Angiography (DVA) is a novel, patented X-ray image processing method visualizing contrast motion by calculating the variance of each pixel intensity in a recorded series of images. The image processing algorithm is built in a software that is able to generate DVA images from raw X-ray image series. Our aim was to determine the potential benefits of DVA in peripheral endovascular interventions.
Material and Methods: Three observational prospective studies enrolled 96 patients undergoing lower limb X-ray angiography due to symptomatic peripheral arterial disease. A subgroup of 24 patients received carbon-dioxide (CO2) as contrast medium and a subgroup of 30 patients (XR) were examined with normal (1.2 µGy/frame) and 70% reduced (0.36 microGy/frame) X-ray dose protocols. We compared the signal-to-noise ratios (SNRs) of Digital Subtraction Angiography (DSA) and DVA image pairs. Visual quality comparisons were also performed by vascular specialists using a 5-grade Likert scale. Interrater agreement was characterized by percent agreement and Fleiss’ kappa.
Results: DVA provided 3.3 times (median) higher SNR than DSA on angiograms obtained using iodinated contrast medium (ICM). The ratio was 3.0 times (median) higher in the images of the CO2 subgroup. In 69% of the ICM group comparisons it was judged that DVA provided higher quality images than DSA. Fleiss' kappa was 0.17 (p<0.001). DVA was preferred over DSA in 85% of paired image comparisons in the CO2 subgroup. Fleiss’ kappa was 0.27 (p<0.001). In the XR group, the SNR of reduced-dose DVA (rdDVA) images were consistently higher (2.7-3.1-fold) than the corresponding normal-dose DSA (ndDSA) images. rdDVA images had significantly higher Likert-score than the corresponding ndDSA images (E: 3.90±0.07 vs 3.56±0.08, p<0.05; R: 3.60±0.08 vs 3.29±0.09, p<0.05) but there was no difference between ndDSA and rdDVA (3.56±0.08 vs 3.60±0.08) scores.
Conclusions: In conclusion, DVA provides significantly higher image quality than DSA while performing catheter angiography with ICM or CO2. The higher image quality makes CO2 angiography and endovascular therapy more feasible for patients with renal insufficiency and iodine allergy. DVA also allows a very substantial (70%) X-ray dose reduction in lower limb angiography without affecting the quality and diagnostic value of angiograms.