Digital Subtraction Angiography Image Quality Research Articles

Initial Experience Using Digital Variance Angiography in Context of Prostatic Artery Embolization in Comparison with Digital Subtraction Angiography.

In previous clinical studies digital variance angiography (DVA) provided higher contrast-to-noise ratio (CNR) and better image quality in lower extremity angiography than digital subtraction angiography (DSA). Our aim was to investigate whether DVA has similar quality reserve in prostatic artery embolization (PAE). The secondary aim was to explore the potential advantages of the color-coded DVA (ccDVA) technology in PAE. This retrospective study evaluated 108 angiographic acquisitions from 30 patients (mean ± SD age 68.0 ± 8.9, range 41-87) undergoing PAE between May and October 2020. DSA and DVA images were generated from the same unsubtracted acquisition, and their CNR was calculated. Visual evaluation of DVA and DSA image quality was performed by four experienced interventional radiologists in a randomized, blinded manner. The diagnostic value of DSA and ccDVA images was also evaluated using clinically relevant criteria (visibility of small [< 2.5 mm] and large arteries [> 2.5 mm], feeding arteries and tissue blush) in a paired comparison. Data were analysed by the Wilcoxon signed rank test or the binomial test, the interrater agreement was determined by the Kendall W or Fleiss Kappa analysis. DVA provided 4.11 times higher median CNR than DSA (IQR: 1.72). The visual score of DVA images (4.40 ± 0.05) was significantly higher than that of DSA (3.39 ± 0.07, p < 0.001). The Kendall W analysis showed moderate but significant agreement (WDVA = 0.38, WDSA = 0.53). The preference of ccDVA images was significantly higher in all criteria (63-89%) with an interrater agreement of 58-79%. The Fleiss Kappa range was 0.02-0.18, significant in all criteria except large vessels. Our data show that DVA provides higher CNR and better image quality in PAE. This quality reserve might be used for dose management (reduction of radiation dose and contrast agent volume), and ccDVA technology has also a high potential to assist PAE interventions in the future.

Application of deblur technology for improving the clarity of digital subtractive angiography.

Digital subtraction angiography (DSA) is most commonly used in vessel disease examinations and treatments. We aimed to develop a novel deep learning-based method to deblur the large focal spot DSA images, so as to obtain a clearer and sharper cerebrovascular DSA image. The proposed network cascaded several residual dense blocks (RDBs), which contain dense connected layers and local residual learning. Several loss functions for image restoration were investigated. Our training set consisted of 52 paired images of angiography with more than 350,000 cropped patches. The testing set included 10 body phantoms and 80 clinical images of different types of diseases for subjective evaluation. All test images were acquired using a large focal spot, and phantom images were simultaneously acquired using a micro focal spot as ground-truth. Peak-to-noise ratio (PSNR) and structural similarity (SSIM) were determined for quantitative analysis. The deblurring results were compared with the original data, and the image quality was subjectively evaluated and graded by two clinicians. For quantitative analysis of phantom images, the average PSNR/SSIM based on the deep-learning approach (35.34/0.9566) was better than that of large focal spot images (30.64/0.9163). For subjective evaluation of 80 clinical patient images, image quality in all types of cerebrovascular diseases was also improved based on a deep-learning approach (p < 0.001). Deep learning-based focal spot deblur algorithm can efficiently improve DSA image quality for better visualization of blood vessels and lesions in the image.

Digital Variance Angiography in Selective Lower Limb Interventions

PurposeTo evaluate the potential benefits of digital variance angiography (DVA) in selective lower limb angiography and to compare the performance of 2 DVA algorithms (conventional DVA1 and the recently developed DVA2) to that of digital subtraction angiography (DSA). Materials and MethodsFrom November 2019 to May 2020, 112 iodinated contrast media (ICM) and 40 carbon dioxide (CO2) angiograms were collected from 15 and 13 peripheral artery disease patients, respectively. The DVA files were retrospectively generated from the same unsubtracted source file as DSA. The objectively calculated contrast-to-noise ratio (CNR) and the subjective visual image quality of DSA, DVA1, and DVA2 images were statistically compared using the Wilcoxon signed-rank test. The images were evaluated by 6 radiologists (R.P.T., S.V., A.M.K., S.S.A., O.E., and J.S.) from 2 centers using a 5-grade Likert scale. ResultsBoth DVA algorithms produced similar increase (at least 2-fold) in CNR values (P < .001) and significantly higher image quality scores than DSA, independent of the contrast agent used. The overall scores with ICM were 3.61 ± 0.05 for DSA, 4.30 ± 0.04 for DVA1, and 4.33 ± 0.04 for DVA2 (each P < .001 vs DSA). The scores for CO2 were 3.10 ± 0.14 for DSA, 3.63 ± 0.13 for DVA1 (P < .001 vs DSA), and 3.38 ± 0.13 for DVA2 (P < .05 vs DSA). ConclusionsDVA provides higher CNR and significantly better image quality in selective lower limb interventions irrespective of the contrast agent used. Between DVA algorithms, DVA1 is preferred because of its identical or better image quality than DVA2. DVA can potentially help the interventional decision process and its quality reserve might allow dose management (radiation/ICM reduction) in the future.

Preliminary results of DSA denoising based on a weighted low-rank approach using an advanced neurovascular replication system.

2D digital subtraction angiography (DSA) has become an important technique for interventional neuroradiology tasks, such as detection and subsequent treatment of aneurysms. In order to provide high-quality DSA images, usually undiluted contrast agent and a high X-ray dose are used. The iodinated contrast agent puts a burden on the patients' kidneys while the use of high-dose X-rays expose both patients and medical staff to a considerable amount of radiation. Unfortunately, reducing either the X-ray dose or the contrast agent concentration usually results in a sacrifice of image quality. To denoise a frame, the proposed spatiotemporal denoising method utilizes the low-rank nature of a spatially aligned temporal sequence where variation is introduced by the flow of contrast agent through a vessel tree of interest. That is, a constrained weighted rank-1 approximation of the stack comprising the frame to be denoised and its temporal neighbors is computed where the weights are used to prevent the contribution of non-similar pixels toward the low-rank approximation. The method has been evaluated using a vascular flow phantom emulating cranial arteries into which contrast agent can be manually injected (Vascular Simulations Replicator, Vascular Simulations, Stony Brook NY, USA). For the evaluation, image sequences acquired at different dose levels as well as different contrast agent concentrations have been used. Qualitative and quantitative analyses have shown that with the proposed approach, the dose and the concentration of the contrast agent could both be reduced by about 75%, while maintaining the required image quality. Most importantly, it has been observed that the DSA images obtained using the proposed method have the closest resemblance to typical DSA images, i.e., they preserve the typical image characteristics best. Using the proposed denoising approach, it is possible to improve the image quality of low-dose DSA images. This improvement could enable both a reduction in contrast agent and radiation dose when acquiring DSA images, thereby benefiting patients as well as clinicians. Since the resulting images are free from artifacts and as the inherent characteristics of the images are also preserved, the proposed method seems to be well suited for clinical images as well.

Digital Variance Angiography as a Paradigm Shift in Carbon Dioxide Angiography

Our aim was to investigate the feasibility of digital variance angiography (DVA) in lower extremity CO2 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). 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 CO2 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 signal-to-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. A total of 4912 regions of interest were carefully selected in 110 image pairs to determine the SNRs. The ratio of SNRDVA/SNRDSA 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). These data show that lower-limb CO2 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 CO2 as a safer contrast agent in clinical practice.

A Motion Artifact Reduction Method in Cerebrovascular DSA Sequence Images

Digital Subtraction Angiography (DSA) can be used for diagnosing the pathologies of vascular system including systemic vascular disease, coronary heart disease, arrhythmia, valvular disease and congenital heart disease. Previous studies have provided some image enhancement algorithms for DSA images. However, these studies are not suitable for automated processes in huge amounts of data. Furthermore, few algorithms solved the problems of image contrast corruption after artifact removal. In this paper, we propose a fully automatic method for cerebrovascular DSA sequence images artifact removal based on rigid registration and guided filter. The guided filtering method is applied to fuse the original DSA image and registered DSA image, the results of which preserve clear vessel boundary from the original DSA image and remove the artifacts by the registered procedure. The experimental evaluation with 40 DSA sequence images shows that the proposed method increases the contrast index by 24.1% for improving the quality of DSA images compared with other image enhancement methods, and can be implemented as a fully automatic procedure.

CO2−DSAの画質に対する注入速度と水流の影響について ファントムによる研究

CO2−DSAの画質に対する注入速度と水流の影響について ファントムによる研究

A new angiographic imaging platform reduces radiation exposure for patients with liver cancer treated with transarterial chemoembolization.

ObjectivesTo quantify the reduction of radiation liver cancer patients are exposed to during transarterial chemoembolization (TACE), while maintaining diagnostic image quality, using a new C-arm imaging platform.MethodsIn this prospective, HIPAA-compliant, IRB-approved, two-arm trial, 78 consecutive patients with primary or secondary liver cancer were treated with TACE on a C-arm imaging platform before and after an upgrade incorporating optimized acquisition parameters and advanced real-time image processing algorithms. Dose area product (DAP) and radiation time of each digital fluoroscopy (DF), digital subtraction angiography (DSA) and cone beam CT (CBCT) were recorded. DSA image quality was assessed by two blinded and independent readers on a four-rank scale.ResultsBoth cohorts showed no significant differences with regard to patient characteristics and tumour burden. The new system resulted in a statistically significant reduction of cumulative DAP of 66 % compared to the old platform (median 132.9 vs. 395.8 Gy cm2). Individually, DAP of DF, DSA and CBCT decreased by 52 %, 79 % and 15 % (p < 0.01, p < 0.01, p = 0.51), respectively. No statistically significant differences in DSA image quality were found between the two imaging platforms.ConclusionsThe new imaging platform significantly reduced radiation exposure for TACE procedures without increased radiation time or negative impact on DSA image quality.Key Points• The new C-arm system allowed reduction of radiation exposure by two thirds• The procedure’s course was not affected by the new platform• No decrease in DSA image quality was observed after the radiation reductionElectronic supplementary materialThe online version of this article (doi:10.1007/s00330-015-3717-0) contains supplementary material, which is available to authorized users.

Multiresolution Image Registration in Digital X-Ray Angiography with Intensity Variation Modeling

Digital subtraction angiography (DSA) is a widely used technique for visualization of vessel anatomy in diagnosis and treatment. However, due to unavoidable patient motions, both externally and internally, the subtracted angiography images often suffer from motion artifacts that adversely affect the quality of the medical diagnosis. To cope with this problem and improve the quality of DSA images, registration algorithms are often employed before subtraction. In this paper, a novel elastic registration algorithm for registration of digital X-ray angiography images, particularly for the coronary location, is proposed. This algorithm includes a multiresolution search strategy in which a global transformation is calculated iteratively based on local search in coarse and fine sub-image blocks. The local searches are accomplished in a differential multiscale framework which allows us to capture both large and small scale transformations. The local registration transformation also explicitly accounts for local variations in the image intensities which incorporated into our model as a change of local contrast and brightness. These local transformations are then smoothly interpolated using thin-plate spline interpolation function to obtain the global model. Experimental results with several clinical datasets demonstrate the effectiveness of our algorithm in motion artifact reduction.

Development of Digital Subtraction Angiography for Coronary Artery

The purpose of this research is to develop a new method of digital subtraction angiography (DSA) that can be applied to real time with reducing motion artifacts caused by heart movement and respiration. To create the mask image for DSA, the maximum pixel value at each pixel (which is the opposite pixel value to that of a vessel filled by contrast medium) was selected from the previous 14 image frames. The search area for the maximum pixel value was selected using the value of the standard deviation (SD) for each pixel from the previous 14 image frames. When the SD value in the 14 frames was greater than a threshold level, the search area of the maximum value became 1 pixel x 1 pixel x 14 frames; otherwise, 7 pixels x 7 pixels x 7 frames. The image quality of new DSA was evaluated on 20 coronary arteriogram images, including various degrees of occlusion or stenosis. The results indicated a considerable improvement in DSA image quality; thus, the coronary arteries, carotid artery, and vein were clearly enhanced.

低濃度DSA画像におけるヒストグラム変換を用いたコントラスト改善の基礎的検討

Digital subtraction angiography (DSA) is a method for increasing a contrast of blood vessels by injecting a contrast medium into the blood vessels. Iodine contrast media are widely used for the DSA study, but might cause a sever side effect for the patients having iodine contraindication disease. In the previous report, we introduced gadolinium contrast medium into the DSA study. Although the contrast of the images with gadolinium contrast medium was slightly decreased compared to that with iodine contrast medium, the image quality was well acceptable for diagnostic procedures without causing any side effect. However, there is a limitation for dosage in the gadolinium contrast medium due to the long biological half-life. Lower concentration of the contrast media decreases the image contrast. In this report, we proposed a novel image processing algorithm to improve the image quality of DSA adjusting to low concentration of contrast media. The image processing algorithm consisted of smoothing, thresholding, and histogram transformation, and signal-to-noise ratio (SNR) was further improved utilizing median filtering process: In conclusion, our novel method using low concentration of gadolinium contrast medium in the DSA study showed enough image quality and may be useful for diagnosis process.

DSAシステムにおけるビデオレベルの検討

With the progress of digital image processing technology and the development of interventional radiology (IVR), digital subtraction angiography (DSA) has become an important inspection method in angiography. The quality of DSA images and the accuracy of densitometry are affected by many factors. This study examined the relations between these factors and the intensity of the video levels output from a charge coupled device (CCD) camera. The results indicated that by selecting the optimal intensity of incident light for the CCD camera, the radiation exposure dose to patients can be reduced without impairing image quality in clinical use. The accuracy of densitometry was also improved.

Pulmonary embolism: diagnosis in 211 patients with use of selective pulmonary digital subtraction angiography with a flow-directed catheter.

To evaluate image quality, safety, and clinical validity of selective, intraarterial, pulmonary digital subtraction angiography (DSA) with use of a flow-directed, balloon-tipped catheter in patients with suspected acute pulmonary embolism (PE). Pulmonary DSA was performed in 211 patients with suspected PE. Subselective magnification series were obtained with nonionic contrast material. Clinical outcome of patients with a negative pulmonary DSA study was assessed by means of retrospective analysis of their medical records, with a minimum follow-up of 3 months. Among the 211 patients, DSA image quality was excellent in 129 (61.1%), adequate in 79 (37.4%), and poor in three (1.4%). Two angiograms (0.9%) were nondiagnostic. No complications occurred. Of 129 patients with negative DSA in whom anticoagulants were withheld, 16 died of disorders other than PE; one (0.9%, 95% confidence interval 0.0%, 4.2%) of 113 patients alive at 3 months returned after 3 weeks with possible PE. Pulmonary DSA with the flow-directed catheter is a safe procedure and provides good to excellent image quality. Anticoagulants can be withheld in patients suspected of having PE when pulmonary DSA results are negative.

Digital subtraction angiography (DSA) in renal and renovascular hypertension: diagnostic value and application in follow-up studies after PTA.

Diagnosis of renovascular hypertension is of particular interest because it is curable by vascular surgery or percutaneous transluminal angioplasty (PTA). Transvenous digital subtraction angiography (DSA) is a minimally invasive method of importance in detecting renal hypertension of different origins (pre-, intra-, postrenal). This study was carried out to assess the value of transvenous DSA in analyzing the renal arteries and renal parenchyma, in detecting renal artery stenosis, and in controlling PTA results. Our results demonstrate that image quality of transvenous DSA of the renal arteries was excellent (diagnostic in 474 of 510 cases, 93%). A large number (62%) could be analyzed following one injection of contrast medium, in 25% a second, and 6% a third injection was necessary. In follow-up studies after PTA (1 week to 24 months) patients with normalized blood pressure values (16/33) had a completely reopened arterial segment and normal parenchyma of both kidneys. In persistent or recurrent hypertension (17/33) restenosis could be detected by transvenous DSA in 2 cases and renal parenchymal lesions in 8 cases. Reversible intimal dissections observed immediately following PTA had no influence on blood pressure results. Intra-arterial DSA is recommended when renal artery stenosis is to be evaluated for PTA and when the result of balloon catheter dilatation is to be evaluated. Intra-arterial DSA is indicated to exclude stenosis following kidney transplantation and to determine perfusion of the graft (parenchyma and venous return) taking advantage of small volumes and concentrations of contrast material made possible by digital contrast enhancement.

Digital Subtraction Angiography

Digital subtraction angiography (DSA) is an alternative method for imaging the cerebral vasculature. Intravenous DSA is used primarily for evaluating the common carotid bifurcation. The superior image quality of arterial DSA makes it more suitable for studying intracranial arteriovenous malformations, aneurysms, and tumor circulation.