Have CT and MR Angiography Replaced Catheter Angiography in Diagnosing Peripheral Arterial Disease?

Evaluation of Computerized Tomography Utilization in Comparison to Digital Subtraction Angiography in Patients with Peripheral Arterial Disease

BACKGROUND

Perform literature review to analyze current practices in imaging patient with peripheral arterial disease (PAD) and examine patterns in our practice in order to assess whether a lower extremity computed tomography angiography (CTA) in addition to digital subtraction angiography enhanced the assessment of vessel calcification, percentage of stenosis, and affected outcomes in patients with PAD.

METHODS

The study included patients who underwent lower extremity imaging and were followed up to 12 months. This population was divided into cases who had both an angiogram and CTA performed within 30 days (n = 20), and controls who underwent angiography only (n = 19). Baseline characteristics, imaging results, and clinical outcomes were analyzed.

RESULTS

Thirty-nine patients met study criteria (mean age was 58.4 years, 69.2% were males, and 33.3% had diabetes). Patients mostly presented with tissue loss/rest pain (10.3%), claudication (15.4%), acute limb (10.3%), and trauma (15.4%). We have not observed any statistically significant differences in various examined blood vessels when their features (e.g., vessel diameter, stenosis, calcifications) were assessed by CTA combined with angiography versus angiography alone. The exceptions were external iliac artery, superficial femoral artery and dorsalis pedis vessels. In external iliac artery percentage of stenosis was 1.11% as determined by computed tomography (CT) scan versus 30% by angiography (P = 0.009). For superficial femoral artery stenosis, the percentage determined by CT was 48.68% vs. 81.41% by angiography, and observed difference between 2 modalities was statistically significant (P = 0.025). For dorsalis pedis percentage of stenosis detected by CT scan was 60.63% vs. 22.73% by angiography, and the differences in findings by these modalities were statistically significant (P = 0.039). The most frequent perioperative complication was cardiac-related (35.5%). Nineteen patients were readmitted and 8 had reinterventions within 12 months.

CONCLUSIONS

Both imaging modalities yielded similar results for assessing vessel calcification and percentage of stenosis regardless of anatomic vessel location. Overall, utilization of CTA in addition to angiography for large vessels above the knee (e.g., iliac artery, superficial femoral artery) and below the knee for dorsalis pedis provided more detailed information on the properties of these vessels. Therefore, during preoperative assessments, CTA may be helpful in addition to angiography for planning surgical and endovascular interventions for symptomatic PAD treatment in larger vessels.

Application opportunity of Doppler ultrasound combined with CT angiography in diabetic lower extremity arterial disease and the analysis of the risk factors

Objective

This study examined the potential of combining Doppler ultrasound (DUS) and CT angiography (CTA) for early detection and intervention of lower extremity arterial disease (LEAD) in diabetes.Concurrently, risk factors influencing LEAD progression were analyzed.

Methods

106 Type-2 diabetes patients with LEAD, having undergone DUS and CTA, were divided into four stages according to Fontaine stage. Results of DUS and CTA were compared across stages and potential risk factors were analyzed.

Results

Positive detection rates of LEAD differed between DUS and CTA for Fontaine stages I and II (P < 0.05), with no significant difference for stages III and IV (P > 0.05). CTA identified subgroups with mild to moderate stenosis and severe stenosis or occlusion, with positive rates on DUS of 17.95% and 89.9% respectively. Hypertension was found as an independent risk factor affecting LEAD progression.

Conclusion

CTA should be performed early for LEAD in diabetes patients at Fontaine stages I and II, regardless of DUS results. For diabetes patients with LEAD, stringent blood pressure control is crucial to delay disease progression.

Low-iodine 40-keV virtual monoenergetic CT angiography of the lower extremities

Introduction

To evaluate a reduced iodine volume protocol for lower extremity CT angiography (CTA) using dual-energy CT (DECT).

Methods

This retrospective study included consecutive patients who underwent lower extremity CTA from June to December 2022. A 10 ml 1:1 mixed test bolus was performed, followed by a 40 ml full bolus at a 2.5/s injection rate, using 400 mg/ml iodine contrast media. Conventional and 40 keV virtual monoenergetic images (VMI) were reconstructed. For both reconstructions, five main artery segments were assessed with a 3-point image quality score as well as quantitative attenuation, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) measurements with diagnostic quality thresholds (respectively >150 HU and >3).

Results

Forty patients were included in the study (mean age 68 ± 12 yo). 200 artery segments were assessed. Median qualitative image scores were 3 [IQR, 3, 3] for both reconstructions. 40 keV VMI upgraded qualitative scores for 51 (26%) of patients, including 9 (5%) from nondiagnostic to diagnostic quality. 40 keV VMI obtained attenuation and CNR diagnostic quality for respectively 100% and 100% of segments, compared with 96% and 98% for conventional images (p < 0.001). Distal artery segments showed the most differences between 40 keV VMI and conventional images.

Conclusion

A low-iodine lower extremity CTA protocol is feasible, with 40 keV virtual monoenergetic spectral reconstruction enabling maintained diagnostic image quality at the distal artery segments.

Digital Subtraction Angiography (DSA) Technical and Diagnostic Aspects in the Study of Lower Limb Arteries

Cardiovascular diseases represent one of the most frequent diseases worldwide; among these, lower limb ischemia is a threatening condition, which can lead to permanent disability if not promptly and correctly diagnosed and treated. A patient’s clinical evaluation and diagnostic imaging (e.g., color-Doppler ultrasound, computed tomography angiography (CTA), and magnetic resonance imaging (MRI)) are mandatory to carefully assess arterial lesion extension and severity. Digital subtraction angiography (DSA) is a minimally invasive technique that represents the gold standard for percutaneous revascularization treatment of symptomatic patients who are refractory to medical management. However, when dealing with patients with lower limb terminal ischemia, the correct interpretation of diagnostic DSA findings is mandatory for treatment re-planning and to effectively evaluate post-treatment results and complications. The purpose of this review is to provide interventional radiologists and endovascular practitioners with an up-to-date practical guide to diagnostic angiography of the lower limbs, which is mandatory to address correct treatment decisions and post-treatment evaluation.

Simultaneous vessel segmentation and unenhanced prediction using self-supervised dual-task learning in 3D CTA (SVSUP)

BACKGROUND AND OBJECTIVE

The vessel segmentation in CT angiography (CTA) provides an important basis for automatic diagnosis and hemodynamics analysis. Virtual unenhanced (VU) CT images obtained by dual-energy CT can assist clinical diagnosis and reduce radiation dose by obviating true unenhanced imaging (UECT). However, accurate segmentation of all vessels in the head-neck CTA (HNCTA) remains a challenge, and VU images are currently not available from conventional single-energy CT imaging.

METHODS

In this paper, we proposed a self-supervised dual-task deep learning strategy to fully automatically segment all vessels and predict unenhanced CT images from single-energy HNCTA based on a developed iterative residual-sharing scheme. The underlying idea was to use the correlation between the two tasks to improve task performance while avoiding manual annotation for model training.

RESULTS

The feasibility of the strategy was verified using the data of 24 patients. For vessel segmentation task, the proposed model achieves a significantly higher average Dice coefficient (84.83%, P-values 10^-3 in paired t-test) than the state-of-the-art segmentation model, vanilla VNet (78.94%), and several popular 3D vessel segmentation models, including Hessian-matrix based filter (62.59%), optically-oriented flux (66.33%), spherical flux model (66.91%), and deep vessel net (66.47%). For the unenhanced prediction task, the average ROI-based error compared to the UECT in the artery tissue is 6.1±4.5 HU, similar to previously reported 6.4±5.1 HU for VU reconstruction.

CONCLUSIONS

Results show that the proposed dual-task framework can effectively improve the accuracy of vessel segmentation in HNCTA, and it is feasible to predict the unenhanced image from single-energy CTA, providing a potential new approach for radiation dose saving. Moreover, to our best knowledge, this is the first reported annotation-free deep learning-based full-image vessel segmentation for HNCTA.

Approaches to Peripheral Artery Disease in Diabetes: Are There Any Differences?

Peripheral artery disease (PAD) increases the risk of diabetes, while diabetes increases the risk of PAD, and certain symptoms in each disease increase the risk of contracting the other. This review aims to shed light on this harmful interplay between the two disorders, with an emphasis on the phenotype of a patient with both diabetes and PAD, and whether treatment should be individualized in this high-risk population. In addition, current guideline recommendations for the treatment of PAD were analyzed, in an attempt to establish the differences and evidence gaps across a population suffering from these two interconnected disorders.

Lower extremity CT angiography in peripheral arterial disease: from the established approach to evolving technical developments

With the advent of multidetector computed tomography (CT), CT angiography (CTA) has gained widespread popularity for noninvasive imaging of the arterial vasculature. Peripheral extremity CTA can nowadays be performed rapidly with high spatial resolution and a decreased amount of both intravenous contrast and radiation exposure. In patients with peripheral artery disease (PAD), this technique can be used to delineate the bilateral lower extremity arterial tree and to determine the amount of atherosclerotic disease while differentiating between acute and chronic changes. This article provides an overview of several imaging techniques for PAD, specifically discusses the use of peripheral extremity CTA in patients with PAD, clinical indications, established technical considerations and novel technical developments, and the effect of postprocessing imaging techniques and structured reporting.

The feasibility of low iodine dynamic CT angiography with test bolus for evaluation of lower extremity peripheral artery disease

OBJECTIVE

This study aims to determine if low iodine dynamic computed tomography angiography performed after a fixed delay or test bolus acquisition demonstrates high concordance with clinical computed tomography angiography (using a routine amount of iodinated contrast) to display lower extremity peripheral arterial disease.

METHODS

After informed consent, low iodine dynamic computed tomography angiography examination (using either a fixed delay or test bolus) using 50 ml of iodine contrast media was performed. A subsequent clinical computed tomography angiography using standard iodine dose (115 or 145 ml) served as the reference standard. A vascular radiologist reviewed dynamic and clinical computed tomography angiography images to categorize the lumen into "not opacified", "<50% stenosis", " 50 ̶70% stenosis", ">70% stenosis", and "occluded" for seven arterial segments in each lower extremity. Concordance between low iodine dynamic computed tomography angiography and the routine iodine reference standard was calculated. The clinical utility of 4D volume-rendered images was also evaluated.

RESULTS

Sixty-eight patients (average age 66.1 ± 12.3 years, male; female = 49: 19) were enrolled, with 34 patients each undergoing low iodine dynamic computed tomography angiography using fixed delay and test bolus techniques, respectively. One patient assigned to the test bolus group did not undergo low iodine computed tomography angiography due to unavailable delayed time. The fixed delay was 13 s, with test bolus acquisition resulting in a mean variable delay prior to image acquisition of 19.5 s (range; 8-32 s). Run-off to the ankle was observed using low iodine dynamic computed tomography angiography following fixed delay and test bolus acquisition in 76.4% (26/34) and 100% (33/33) of patients, respectively (p = 0.005). Considering extremities with run-off to the ankle and without severe artifact, the concordance rate between low iodine dynamic computed tomography angiography and the routine iodine reference standard was 86.8% (310/357) using fixed delay and 97.9% (425/434) using test bolus (p < 0.001). 4D volume-rendered images using fixed delay and test bolus demonstrated asymmetric flow in 57.7% (15/26) and 58.1% (18/31) (p = 0.978) of patients, and collateral blood flow in 11.5% (3/26) and 22.6% (7/31) of patients (p = 0.319), respectively.

CONCLUSION

Low iodine dynamic computed tomography angiography with test bolus acquisition has a high concordance with routine peripheral computed tomography angiography performed with standard iodine dose, resulting in improved run-off to the ankle compared to dynamic computed tomography angiography performed after a fixed delay. This method is useful for minimizing iodine dose in patients at risk for contrast-induced nephropathy. 4D volume-rendered computed tomography angiography images provide useful dynamic information.

Changing National Medicare Utilization of Catheter, Computed Tomography, and Magnetic Resonance Extremity Angiography: A Specialty-focused 16-Year Analysis

To assess changing utilization of extremity angiography from 2001 to 2016, focusing on modalities and provider specialties. Medicare PSPS Master Files from 2001-2016 and POSPUF from 2016 were used to determine overall and specialty utilization of diagnostic catheter angiography (DCA), CT angiography (CTA), and MR angiography (MRA). From 2001 to 2016, extremity angiography increased from 1107 to 1590 extremities imaged per 100,000 beneficiaries, with rapid expansion of CTA (22 in 2001 to 619 in 2009; plateau of 645 in 2016), but declines in DCA (1039 to 914) and MRA (45 to 30). Over time, extremity angiography shifted from 94% DCA, 4% MRA, and 2% CTA to 58% DCA, 41% CTA, and 2% MRA. For radiologists, extremity angiography increased slightly (741 to 767) with increases in CTA (20 to 595) and large decreases in DCA (681 to 145), with MRA remaining low (40 to 27). Extremity angiography increased for cardiologists (197 to 349) and vascular surgeons (87 to 351), both overwhelmingly performing DCA. Radiologists' share of all extremity angiography shifted from 67% to 48%, with interventionalists (47%), generalists (43%), and abdominal radiologists (7.4%) providing most radiologist services in 2016. Throughout, radiologists were the dominant providers of CTA (89% to 92%) and MRA (89% to 90%). Extremity angiography utilization in Medicare beneficiaries increased nearly 50% from 2001 to 2016, largely related to CTA performed by radiologists. Of radiologists, interventionalists and generalists together render most services. Cardiologists and surgeons assumed a large share of DCA previously performed by radiologists.

Fibrosis imaging: Current concepts and future directions

Fibrosis plays an important role in many different pathologies. It results from tissue injury, chronic inflammation, autoimmune reactions and genetic alterations, and it is characterized by the excessive deposition of extracellular matrix components. Biopsies are routinely employed for fibrosis diagnosis, but they suffer from several drawbacks, including their invasive nature, sampling variability and limited spatial information. To overcome these limitations, multiple different imaging tools and technologies have been evaluated over the years, including X-ray imaging, computed tomography (CT), ultrasound (US), magnetic resonance imaging (MRI), positron emission tomography (PET) and single-photon emission computed tomography (SPECT). These modalities can provide anatomical, functional and molecular imaging information which is useful for fibrosis diagnosis and staging, and they may also hold potential for the longitudinal assessment of therapy responses. Here, we summarize the use of non-invasive imaging techniques for monitoring fibrosis in systemic autoimmune diseases, in parenchymal organs (such as liver, kidney, lung and heart), and in desmoplastic cancers. We also discuss how imaging biomarkers can be integrated in (pre-) clinical research to individualize and improve anti-fibrotic therapies.

Noninvasive Physiologic Vascular Studies: A Guide to Diagnosing Peripheral Arterial Disease

Noninvasive physiologic vascular studies play an important role in the diagnosis and characterization in peripheral arterial disease (PAD) of the lower extremity. These studies evaluate the physiologic parameters of blood flow through segmental arterial pressures, Doppler waveforms, and pulse volume recordings. Collectively, they comprise a powerful toolset for defining the functionality of the arterial system, localizing the site of disease, and providing prognostic data. This technology has been widely adopted by diverse medical specialty practitioners, including radiologists, surgeons, cardiologists, and primary care providers. The use of these studies increased substantially between 2000 and 2010. Although they do not employ imaging, they remain a critical component for a comprehensive radiologic vascular laboratory. A strong presence of radiology in the diagnosis of PAD adds value in that radiologists have shifted to noninvasive alternatives to diagnostic catheter angiography (DCA), such as computed tomography (CT) and magnetic resonance (MR) angiography, which provide a more efficient, less-expensive, and lower-risk alternative. Other specialties have increased the use of DCA during the same period. The authors provide a review of the relevant anatomy and physiology of PAD as well as the associated clinical implications. In addition, guidelines for interpreting the ankle-brachial index, segmental pressures, Doppler waveforms, and pulse volume recordings are reviewed as well as potential limitations of these studies. Noninvasive physiologic vascular studies are provided here for review with associated correlating angiographic, CT, and/or MR findings covering the segmental distribution of PAD as well as select nonatherosclerotic diagnoses. ^©RSNA, 2016.

Reducing Variability in Orthogonal Reformatted Image Quality Associated With Axial Long-z-Axis CT Angiography

OBJECTIVE

The objective of our study was to reduce variation in image quality of orthogonal reformatted images generated from long-z-axis CT angiography (CTA) studies of the upper and lower extremities.

SUBJECTS AND METHODS

Upper and lower extremity CTA studies were targeted at a single health care system. A correctly performed CTA examination was defined as one that met the following three criteria: Sagittal and coronal reformats were obtained, a high-resolution matrix greater than 512 × 512 was used, and reformatted images were available in a distance-measurable format. Baseline data were collected from February 1, 2014, through September 30, 2014. Corrective actions were implemented during three consecutive plan-do-check-act (PDCA) cycles from October 1, 2014, through July 31, 2015, that addressed human, technical, and systematic variations. A 3-month maintenance period followed in which no intervention was performed. Longitudinal data were analyzed monthly using a statistical process control chart (p-chart).

RESULTS

The total number of long-z-axis extremity CTA studies analyzed was as follows: 351 CTA studies were analyzed at baseline, 94 at the first PDCA cycle, 92 at the second PDCA cycle, 114 at the third PDCA cycle, and 138 during the maintenance period. The monthly rate of correctly performed studies ranged from 7% to 51% (mean, 38% ± 13% [SD]) during the baseline period, 32-59% (mean, 46% ± 14%) during the first PDCA cycle, 40-81% (mean, 61% ± 21%) during the second PDCA cycle, and 80-82% (mean, 81% ± 0.9%) during the third PDCA cycle. The monthly rate improved to 90-91% (mean, 91% ± 0.5%) during the maintenance period. The upper and lower control limits of the p-chart were upshifted after the second and third PDCA cycles. Correcting systematic and technical variations led to the greatest improvements in reformat accuracy.

CONCLUSION

Obtaining consistently and correctly reformatted images from long-z-axis CTA studies is achievable using iterative PDCA cycles.

Optimized Protocol for Fast CT Angiography of Lower Limbs Using 160-Row Detector

OBJECTIVE

We proposed and tested a novel acquisition protocol for optimizing a fast computed tomography angiography using a 160-row detector scanner using a longer contrast injection time coupled with multiphasic rate of injection.

METHODS

A prospective randomized study was performed to compare image quality, contrast enhancement, and radiation dose in 2 groups (a fast acquisition and a widely accepted slow acquisition).

RESULTS

There was no difference between groups regarding image quality, noise, and diagnostic performance, but we evidenced a trend to higher radiation dose for the fast acquisition protocol.

CONCLUSIONS

An optimized protocol for performing a fast acquisition computed tomography angiography of lower limbs is feasible, has sufficient diagnostic quality, and can be used in selected patients who would benefit from a short-time scan.

Medicare Utilization of CT Angiography from 2001 through 2014: Continued Growth by Radiologists

PURPOSE

To examine changes in utilization of computed tomography (CT) angiography nationally and changing relative specialty roles in examination interpretation.

MATERIALS AND METHODS

Service-specific claims data for region-specific CT angiography examinations were identified using Medicare Physician Supplier Procedure Summary Master Files from 2001 through 2014. Longitudinal national utilization rates were calculated using annual Medicare enrollment data for 2001-2013. Procedure volumes by specialty group and site of service were analyzed.

RESULTS

Total annual claims for CT angiography for Medicare fee for service beneficiaries increased from 64,846 to 1,709,088 (compound annual growth rate [CAGR] 29%) between 2001 and 2014. Per 1,000 beneficiaries, overall CT angiography utilization increased annually from 2.1 in 2001 to 47.6 in 2013. Overall interpretation market share increased 4% (91%-95%) for radiology. Cardiology increased from 1% in 2001 to 6% in 2007 but decreased annually to 2% in 2014. Vascular surgery market share remained < 1% throughout the study period. Growth of CT angiography in the emergency department (ED) outpaced all other sites of service, increasing from 11% to 28% (CAGR 38%). The chest was the dominant body region imaged with CT angiography, increasing from 36,984 to 914,086 (CAGR 28%).

CONCLUSIONS

Utilization of CT angiography in the Medicare population increased markedly for 2001-2014, particularly in the ED, with radiologists remaining dominant providers. The chest is the most common body region imaged with CT angiography.

Vascular Ultrasound and Noninvasive Physiological Testing for Peripheral Arterial Disease: Are These Tests Being Overused?

PURPOSE

To examine recent trends in the use of duplex ultrasound and noninvasive physiologic tests (NPTs) for determining the presence of peripheral arterial disease (PAD).

METHODS

Medicare Part B databases for 2001-2013 were used. The two Current Procedural Terminology, version four codes for duplex ultrasound of lower-extremity arteries, and the three codes for NPTs of extremity arteries were selected. Procedure volumes of both types of examinations were determined, and utilization rates per 100,000 beneficiaries were calculated. Medicare specialty codes were used to determine what proportions were performed by the major specialty groups involved in these examinations: surgeons, cardiologists, radiologists, and primary care physicians (PCPs).

RESULTS

Between 2001 and 2010 (the peak year), the total utilization rates per 100,000 of duplex ultrasound and NPTs increased by 94% and 84%, respectively. During the ensuing three years, small declines occurred in both. In 2013, utilization rates of both types of tests were far higher than they had been in 2001 (88% higher for duplex ultrasound; 63% higher for NPTs). From 2001 to 2013, use of duplex ultrasound increased 235% among cardiologists, 90% among surgeons, 76% among radiologists, and 53% among PCPs. Utilization rates of NPTs among surgeons were already high in 2001 and increased an additional 23% by 2013. The NPT utilization rates increased 180% among PCPs, 179% among cardiologists, and 61% among radiologists.

CONCLUSIONS

During a period when little growth occurred in the incidence of PAD, sharp growth occurred in testing for the disease.