Digital Variance Angiography as a Paradigm Shift in Carbon Dioxide Angiography

Abstract

Objectives: Our aim was to investigate the feasibility of digital variance angiography (DVA) in lower extremity CO 2 angiography and to compare the quantitative and qualitative performance of the new image processing technique with that of the current reference standard digital subtraction angiography (DSA). Materials and Methods: This prospective study enrolled 24 patients (mean age ± SD, 65.5 ± 9.2 years; 14 males, 65.1 ± 7.5 years; 10 females, 66.1 ± 11.6 years) undergoing lower-limb CO 2 angiography between December 2017 and April 2018 at 2 clinical centers: The Heart and Vascular Center (HVC) of Semmelweis University, Budapest (7 patients), and the Bács-Kiskun County Hospital (BKCH) in Kecskemét (17 patients). The interventional protocol was similar at both sites, but the image acquisition instruments and protocols were different, which allowed us to investigate DVA in different settings. For comparison, the signalto-noise ratio (SNR) of DSA and DVA images were calculated. The visual quality of DSA and DVA images were compared by independent clinical specialists using an online questionnaire. Interrater agreement was characterized by percent agreement and Fleiss kappa. The specialists also evaluated in a random and blinded manner the individual DSA and DVA images on a 5-grade scale ranging from poor (1) to outstanding (5) image quality, and the mean ± standard error of mean (SEM) was calculated. Results: A total of 4912 regions of interest were carefully selected in 110 image pairs to determine the SNRs. The ratio of SNR DVA /SNR DSA was calculated. At HVC, it ranged between 2.58 and 4.16 in the anatomical regions (abdominal, iliac, femoral, popliteal, crural, talar), and the overall median value was 3.53, whereas at BKCH the range was 2.71 to 4.92 and the overall median value was 4.52. During the visual evaluation, 120 DSA and DVA image pairs were compared. At HVC in 78%, although at BKCH in 90% of comparisons, it was judged that DVA provided higher quality images. The interrater agreement was 88% (P < 0.001) and 90% (P < 0.01), respectively. DVA images received consistently higher individual rating than DSA images, regardless of the research site and anatomical region. At HVC, the overall DSA and DVA scores (mean ± SEM) were 2.75 ± 0.12 and 3.23 ± 0.16, respectively (P < 0.05), whereas at BKCH these values were 2.49 ± 0.10 and 3.03 ± 0.09, respectively (P < 0.001). Conclusions: These data show that lower-limb CO 2 angiography DVA, regardless of the image acquisition instruments and protocols, produces higher SNR and significantly better image quality than DSA; therefore this new image processing technique might help the widespread use of CO 2 as a safer contrast agent in clinical practice.

Digital Variance Angiography in Selective Lower Limb Interventions

“…The objective CNR and subjective visual evaluation data clearly show that DVA, independent of the contrast agent used, has a quality advantage not only in nonselective but also in selective lower limb angiography settings, which corresponds to the daily routine setting in interventional procedures (14,16). The improved image quality may expedite or increase confidence in the decision making process during interventional procedures.…”

“…Previous studies (14,16) have reported that DVA provides higher quality images in nonselective lower limb angiography, where the contrast agent is injected infrarenally above the aortic bifurcation. The main aim of this study was to investigate whether this quality advantage can also be observed with different DVA algorithms (DVA1 and DVA2) in selective lower limb interventions.…”

“…Thereby, DVA enhances the moving contrast media–related signal (ie, the flow of contrast agents) and suppresses the noise, resulting in improved image quality. DVA has previously been shown to be superior to DSA in nonselective ICM lower limb interventions, in ICM studies with metal objects, and in nonselective lower limb interventions using CO 2 as the contrast agent ( 14 , 15 , 16 , 17 ). Apart from the standard DVA algorithm (DVA1), another DVA algorithm (DVA2) has recently been developed, allowing additional noise reduction.…”

Tantalum-specific contrast-to-noise ratio or conventional detector dose-driven exposure control in angiography: radiation dose and image quality evaluation in a porcine model

“…Thirdly, image postprocessing was minimised to exclude its effect on IQ. Therefore, its effect on the patient dose was not investigated, although postprocessing is an important instrument of radiation dose reduction [ 23 – 26 ]. Finally, the effect of Ta-CEC on digital angiography as compared to DEC was not evaluated due to several reasons.…”

Digital variance angiography allows about 70% decrease of DSA-related radiation exposure in lower limb X-ray angiography

“…Consequently, the contrast media-induced changes are amplified but the background noise is suppressed, and the image quality is greatly improved. In recent clinical studies DVA provided higher contrast-to-noise ratio (CNR) and better subjective image quality than conventional DSA, both with iodinated contrast media (ICM) 17 , 18 and carbon-dioxide 19 . This significant quality reserve might provide opportunity for contrast media and/or radiation dose reduction, further decreasing the risk of interventional procedures.…”