Lower Extremity Computed Tomography Angiography Research Articles

Ultra-low radiation dose CT angiography of the lower extremity using the iterative model reconstruction (IMR) algorithm

To investigate the image quality of lower-extremity computed tomography (CT) angiography (CTA) with ultra-low radiation dose using the iterative model reconstruction (IMR) algorithm. Lower-extremity CTA was acquired using a 256-multidetector CT system from 90 patients assigned into three groups: (1) the routine dose (RD) group: 120 kVp, automatic tube current modulation (ACTM) with an image quality index of 12, and filtered back projection (FBP); (2) the low-dose (LD) group: 80 kVp, ACTM with an image quality index of 1, and IMR; and (3) the ultra-low dose (ULD) group: 80 kVp, 20 mAs, and IMR. CT attenuation, image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) of the lower-extremity arteries were calculated. Subjective image quality of lower-extremity segments was assessed. Effective radiation dose was recorded. The radiation dose was reduced by 91.4% and 67.3% in the ULD group (0.15±0.02 mSv) compared to the RD group (1.86±0.51 mSv) and the LD group (0.49±0.08 mSv; both p<0.05). Higher CT attenuation, SNR, CNR, and lower image noise were obtained in the ULD group and the LD group compared to the RD group (all p<0.05). Better subjective image quality in lower leg segments was obtained in the ULD group and the LD group compared to the RD group (all p<0.05). No difference was found between the ULD and LD groups in both objective and subjective image quality (all p>0.05). By using IMR during lower-extremity CTA, the radiation dose is reduced by up to 91.4% without compromising image quality.

A Description of the Vascular Anatomy of the Tensor Fascia Lata Perforator Flap Using Computed Tomography Angiography.

The perforator anatomy of the tensor fascia lata (TFL) flap has been studied using cadaver dissection; however, exact descriptions of location, size, and origin of perforator vessels using preoperative imaging modalities remain limited. The aims of this study are to describe TFL perforator anatomy using high-resolution computed tomography angiography (CTA) and to correlate these findings with landmarks for the anterolateral thigh flap to facilitate flap planning. We identified 33 patients who previously underwent bilateral lower extremity CTAs for preoperative planning of free-flap reconstruction. The images were retrospectively reviewed, and the TFL perforator number, size, type, location, and overall pedicle origin and length were recorded. Thirty-three patients and 59 thighs were included in the study. There was an average of 2.5 perforators per TFL. All perforators arose from the ascending branch of the lateral circumflex femoral artery with an average pedicle length of 8.3 cm (range, 6.0-11.2 cm). Sixty-six percent of perforators were septocutaneous and 34% were musculocutaneous. The average perforator size as measured on CTA was 3 mm. The average perforator location was 10.1 cm inferior and 8.5 cm lateral to the line drawn from the anterior superior iliac spine to the superolateral patella. To our knowledge, this is the first study to characterize the vascular anatomy of the TFL perforator flap using high-resolution CTA and correlate this with well-established landmarks used in the planning for other thigh-based flaps. We believe data will facilitate flap design and dissection; potentially shortening operating room times, limiting exploratory incisions used to confirm the presence of thigh based perforators, and improving overall outcomes for patients.

Lower extremity CT angiography at 80 kVp using iterative model reconstruction.

To evaluate the use of 80 kVp and iterative model reconstruction (IMR) in lower extremity computed tomography angiography (CTA). Sixty patients were randomly assigned to Group A or Group B (both n=30) to further undergo CTA. Group A received Protocol 1 (P1) with 120 kVp, 180mAs, and 100mL of contrast agent with filtered back-projection (FBP). Group B received Protocol 2 (P2) and Protocol 3 (P3) with 80 kVp, 140mAs and 75mL of contrast agent with hybrid iterative reconstruction (P2) and IMR (P3). Mean intravascular attenuation (MIA), image noise, contrast-to-noise ratio (CNR), and signal-to-noise ratio (SNR) were compared. Radiologists assessed image quality on a 5-point scale, and radiation was compared between both groups. Group A had 9 men and 21 women (mean age, 68.2±9.3 years [range: 53-85 years]), and Group B had 20 men and 10 women (mean age, 64.8±10.4 years [range: 37-81 years]). The MIA of P2 and P3 were significantly larger than that of P1 (P<0.01). The CNR and SNR of P3 were significantly higher than those of P1 and P2 (P<0.01). The interobserver agreement had Kappa values of 0.78, 0.77, and 0.81 for P1, P2, P3, respectively. The mean CT volume dose index and dose-length product of Group B were lower than those of Group A (P<0.01). Lower extremity CTA using 80 kVp and IMR is useful for lower radiation and contrast agent dose while preserving image quality. IMR can also provide better image quality for small-caliber vessels below the knee than HIR.

Clinical evaluation of covered stents in the treatment of superficial femoral artery pseudoaneurysm in drug abusers.

The present study aimed to investigate the technical feasibility and initial clinical outcomes of a covered stent for the endovascular treatment of superficial femoral artery (SFA) pseudoaneurysm in drug abusers. A total of 29 drug abuse patients with SFA pseudoaneurysm, as confirmed by color Doppler sonography, were enrolled to the present study between January 2012 and May 2014. All patients were treated percutaneously by implantation of a covered stent. Physical examination and lower extremity computed tomography angiography were performed at 1 and 9 months postoperation. Furthermore, the ankle-brachial index (ABI) of all patients was measured. The results indicated that placement of the covered stent was technically successful in all 29 patients. All of the ruptured pseudoaneurysms were successfully sealed with no cases of intraprocedural mortality. In addition, all patients' conditions improved rapidly; active hemorrhage subsidence and vascular bruit disappearance were immediately detected following implantation of the covered stent. During the follow-up period, pain was markedly alleviated and pulsatile mass was decreased as time increased. No complaints or complications were documented. A total of 9 months postoperation, pain and pulsatile mass were not detected. The patency rate of the stent was 100%, and no migration, occlusion or infection was detected. In addition, the ABI was significantly improved, from 0.52±0.09 to 0.97±0.37 (P<0.01). In conclusion, the placement of a covered stent may be considered a promising approach to provide an effective, safe and minimally invasive option for the treatment of SFA pseudoaneurysm in drug abusers.

Lower extremity computed tomography angiography can help predict technical success of endovascular revascularization in the superficial femoral and popliteal artery

ObjectivePreprocedural computed tomography angiography (CTA) assists in evaluating vascular morphology and disease distribution and in treatment planning for patients with lower extremity peripheral artery disease (PAD). The aim of the study was to determine the predictive value of radiographic findings on CTA and technical success of endovascular revascularization of occlusions in the superficial femoral artery-popliteal (SFA-pop) region. MethodsMedical records and available imaging studies were reviewed for patients undergoing endovascular intervention for PAD between January 2013 and December 2015 at a single academic institution. Radiologists reviewed preoperative CTA scans of patients with occlusions in the SFA-pop region. Radiographic criteria previously used to evaluate chronic occlusions in the coronary arteries were used. Technical success, defined as restoration of inline flow through the SFA-pop region with <30% stenosis at the end of the procedure, and intraoperative details were evaluated. ResultsFrom 2013 to 2015, there were 407 patients who underwent 540 endovascular procedures for PAD. Preprocedural CTA scans were performed in 217 patients (53.3%), and 84 occlusions in the SFA-pop region were diagnosed. Ten occlusions were excluded as no endovascular attempt to cross the lesion was made because of extensive disease or concomitant iliac intervention. Of the remaining 74 occlusions in the SFA-pop region, 59 were successfully treated (80%) and 15 were unsuccessfully crossed (20%). The indications for revascularization were claudication in 57% of patients and critical limb ischemia in the remaining patients. TransAtlantic Inter-Society Consensus A, B, and C occlusions were treated with 87% success, whereas D occlusions were treated with 68% success (P = .047). There were nine occlusions with 100% vessel calcification that was associated with technical failure (P = .014). Longer lengths of occlusion were also associated with technical failure (P = .042). Multiple occlusions (P = .55), negative remodeling (P = .69), vessel runoff (P = .56), and percentage of vessel calcification (P = .059) were not associated with failure. On multivariable analysis, 100% calcification remained the only significant predictor of technical failure (odds ratio, 9.0; 95% confidence interval, 1.8-45.8; P = .008). ConclusionsAnalysis of preoperative CTA shows 100% calcification as the best predictor of technical failure of endovascular revascularization of occlusions in the SFA-pop region. Further studies are needed to determine the cost-effectiveness of obtaining preoperative CTA for lower extremity PAD.

Accuracy of Noncontrast Quiescent-Interval Single-Shot Lower Extremity MR Angiography Versus CT Angiography for Diagnosis of Peripheral Artery Disease: Comparison With Digital Subtraction Angiography

ObjectivesThis study sought to evaluate the image quality and diagnostic accuracy of noncontrast quiescent-interval single-shot (QISS) magnetic resonance angiography (MRA) versus iodine-contrast computed tomography angiography (CTA) in patients with peripheral artery disease (PAD), with invasive digital subtraction angiography (DSA) as the reference standard. BackgroundQISS is a recently introduced noncontrast MRA technique. Although the diagnostic accuracy of QISS is reportedly similar to that of contrast-enhanced MRA, its performance compared with contrast-enhanced CTA, the most frequently used noninvasive modality for evaluation of PAD, is unknown. MethodsThirty patients (66 ± 7 years of age) with PAD underwent lower extremity CTA with third-generation dual-source dual-energy CT and 1.5-T MRA using a prototype noncontrast QISS sequence. DSA was performed within 50 days. The abdominal aorta and lower extremity run-off were imaged. Eighteen arterial segments were analyzed. Subjective image quality (3-point Likert scale) and stenosis (5-point grading) were evaluated by 2 observers and compared using the Mann–Whitney U and chi-square tests, respectively. Sensitivity and specificity of MRA and CTA for >50% stenosis detection were compared using the McNemar-test. ResultsOf 540 segments, 15 (2.8%) and 42 (7.8%) inconclusive segments were excluded from MRA and CTA analysis, respectively (p = 0.0006). The DSA results were available for 410 of the remaining segments. Overall subjective image quality was rated similarly with QISS-MRA (2.52 [95% confidence interval: 2.46 to 2.57]) and CTA (2.49 [95% confidence interval: 2.43 to 2.55]; p = 0.5062). The sensitivity and specificity of MRA for >50% stenosis were 84.9% and 97.2%, respectively, similar to those of CTA (87.3% and 95.4%, respectively). Interobserver agreement for stenosis detection was excellent for MRA (κ > 0.81) and CTA (κ > 0.81). ConclusionsNoncontrast QISS-MRA provides high diagnostic accuracy compared with DSA, while being less prone to image artifacts than CTA. QISS better visualizes heavily calcified segments with impaired flow. QISS-MRA obviates the need for contrast administration in PAD patients.

Lower Extremity Computed Tomography Angiography Can Predict Technical Success of Endovascular Revascularization in the Superficial Femoral and Popliteal Arteries

Lower Extremity Computed Tomography Angiography Can Predict Technical Success of Endovascular Revascularization in the Superficial Femoral and Popliteal Arteries

Semiquantitative assessment of tibial artery calcification by computed tomography angiography and its ability to predict infrapopliteal angioplasty outcomes

Tibial artery calcification (TAC) is associated with increased risk of amputation and mortality in peripheral artery disease. We sought to investigate whether the severity of TAC based on semiquantitative analysis of computed tomography angiography (CTA) can predict outcomes of endovascular therapy in patients with critical limb ischemia. We reviewed medical records of 124 patients who underwent lower extremity CTA before intervention. Based on CTA, TAC severity was categorized into three groups: minimal calcification (MC; n= 43), intermediate calcification (IC;n= 36), or extensive calcification (EC; n= 45). Immediate and late outcomes of infrapopliteal interventions were compared, and predictors of the outcomes were investigated. The categorized severity of target TAC correlated with the log-transformed TAC score (r= 0.873; P< .001). The EC group was younger and had more diabetes and chronic kidney disease compared with the MC or IC group (all P< .001). The technical success was lower in the EC group (71.1%) than in the MC (95.3%) or IC (91.7%) group (P= .001). The survival free of unplanned amputations at 2years was significantly lower in the EC group (58.9%) than in the MC (79.0%) or IC (95.3%) group (P< .001). Extensive TAC was an independent predictor of technical success (hazard ratio, 0.02; 95%confidence interval, 0.00-0.45; P= .014) and unplanned amputation (hazard ratio, 9.90; 95% confidence interval, 2.05-47.75; P= .004). The categorized severity of TAC by semiquantitative analysis of CTA correlated with TAC score, and extensive TAC was associated with a lower technical success rate of angioplasty and an increased incidence of unplanned amputation.

Improved Image Quality and Decreased Radiation Dose of Lower Extremity Computed Tomography Angiography Using Low-Tube-Voltage and Adaptive Iterative Reconstruction.

The aim of the study was to investigate the feasibility of low-tube-voltage computed tomography (CT) in combination with 3-dimensional adaptive iterative dose reduction (AIDR-3D) algorithm in lower extremity CT angiography. The CT data of the 120-kV group (n = 30) were reconstructed with filtered back projection (FBP) algorithm. The CT data of the 100-kV group (n = 30) were reconstructed with FBP as well as AIDR-3D algorithms. The 100-kV group showed significantly lower dose-length product than the 120-kV group (P < 0.05). In comparison with the 120-kV and FBP protocol, the 100-kV and FBP protocol showed significantly increased vascular density and noise (P < 0.05). However, in the 100-kV group, images reconstructed with AIDR-3D showed significantly lower noise and significantly higher signal-to-noise ratio and contrast-to-noise ratio than FBP (P < 0.05). Low-tube-voltage (100 kV) 320-row CT in combination with AIDR-3D reconstruction can significantly improve the image quality and reduce radiation dose of lower extremity CT angiography.

Bilateral popliteal artery entrapment syndrome in a young man

A 33-year-old man with no significant medical history presented with exercise-induced right calf discomfort progressing to the right foot and calf numbness. Popliteal, dorsal pedal, and posterior tibial pulses were absent on the right, with no swelling, ulceration, or tenderness. Lower extremity computed tomography angiography 1 day after presentation revealed luminal compromise of the left popliteal artery (A), occlusion of the distal right superficial femoral and popliteal arteries, and short-segment stenosis present in the left popliteal artery. Magnetic resonance imagining of the right knee (B) revealed an anomalous tendinous slip arising from the medial head of the gastrocnemius, causing focal narrowing of the artery.

Novel registration-based framework for CT angiography in lower legs

Proper subtraction and visualization of contrast-enhanced blood vessels in lower extremities using computed tomography angiography (CTA) is based on precise masking of all non-contrasted structures in the area, and it is the main prerequisite for correct diagnosis and decision on treatment for peripheral arterial occlusive disease (PAOD). Because of possible motion of patients during the CTA examination, precise elimination of non-contrasted tissues, including bones, calcifications, and soft tissue, is still very challenging for lower legs, that is, from knees to toes. We propose novel registration-based framework for detection and correction of the motion in lower legs, which typically occurs between and during CTA pre-contrast and post-contrast acquisitions. Within the framework, two registration cores are proposed as alternatives, and resulting CTA subtraction images are compared with Advanced Vessel Analysis considered one of the reference commercial tools among clinical applications for CTA of lower extremities. The CTA subtraction images of 55 patients examined for PAOD are evaluated visually by four expert observers on the Philips Extended Brilliance Workspace using four criteria assessing the overall robustness of tested methods. According to the complex evaluation, the proposed framework enabled valuable improvements of CTA examination of lower legs.

Computed tomography angiography-based evaluation of great saphenous vein conduit for lower extremity bypass

Lower extremity computed tomography angiography (CTA) is frequently used for anatomic assessment of lower extremity peripheral arterial disease. When lower extremity bypass is planned, duplex ultrasound (DUS) is routinely obtained to evaluate the great saphenous vein (GSV) for use as conduit. Although GSV can be visualized on CTA images, diameter assessment is not routinely included in formal study interpretation. We hypothesized that CTA images could be used to measure GSV diameters and that CTA-based diameters would correlate with measurements obtained using DUS. Consecutive patients undergoing lower extremity arterial bypass who were evaluated preoperatively with both CTA and DUS vein mapping were identified at a single hospital. Minimum above- and below-knee GSV diameters were measured from electronically archived CTA images by two independent observers. CTAs were performed using standard arterial phase protocol without additional venous phase imaging. Between-observer reproducibility of CTA-based diameter measurements was evaluated using intraclass correlation coefficients. Correlation between CTA and DUS-based GSV diameters was evaluated with Spearman correlation coefficients. CTA diameter cut-points for identification of adequate GSV bypass conduit, defined as DUS-based minimum GSV diameter≥3 mm, were determined using receiver-operating characteristic curves. Sixty-three lower extremities were evaluated in 36 patients. In the absence of previous surgical removal, GSV was visible on all CTAs reviewed. No instances of GSV thrombosis were identified on DUS. Minimum DUS-based above-knee GSV diameter was 2.9±0.1 mm (range, 1.4-4.6 mm), and mean below-knee diameter was 2.6±0.1 mm (range, 1.3-4.0 mm). When GSV was visible and exceeded the minimum diameter threshold for CTA measurement, correlation between CTA- and DUS-based diameters was both positive and highly significant (ρ=0.595; P<.0001). CTA-based diameters also had excellent reliability between observers (r [95% CI]: 0.88 [0.85-0.91]). For identification of adequate bypass conduit using CTA, above-knee GSV diameter≥3.9 mm was 67% sensitive and 73% specific; below-knee GSV diameter≥3.0 mm was 75% sensitive and 84% specific. CTA-based GSV diameter measurements have good reproducibility and highly significant correlation with DUS-based diameters. CTA-based GSV diameter is a specific but relatively insensitive indicator of adequate bypass conduit. When CTA-based diameters indicate inadequate GSV bypass conduit, confirmatory DUS vein mapping is warranted. Confirmatory DUS vein mapping may be unnecessary when adequate vein diameter is identified on CTA.

CTA-Based Anatomic Evaluation of Saphenous Vein Bypass Conduit: Utility and Correlation With Duplex Ultrasound

Lower extremity Computed Tomography Angiography (CTA) is frequently utilized for anatomic assessment of peripheral arterial disease. In patients requiring lower extremity bypass, duplex ultrasound (DUS) is routinely obtained to evaluated great saphenous vein (GSV) for use as conduit. GSV is visible on CTA images but not routinely assessed or included in study interpretation. We hypothesized that CTA images could be used to measure GSV diameters, and that these diameters would correlate with DUS measurements.

The Value of Dual-Energy Bone Removal in Maximum Intensity Projections of Lower Extremity Computed Tomography Angiography

Dual-energy computed tomography (CT) makes it possible to remove bones and intraluminal plaques from angiography datasets on the basis of spectral differentiation separating iodine from calcium. The objective of this study was to evaluate the feasibility and efficiency of this technique by comparing maximum intensity projections (MIP) created with different bone removal techniques: (a) dual-energy bone removal (DEBR); (b) purely software-based bone removal without manual corrections (SBBR - MC); and (c) manually corrected software-based bone removal (SBBR + MC). A further aim was to evaluate the dual-energy-based plaque removal tool. Fifty-one patients underwent dual-energy CT angiography of the lower-extremity arteries on a dual-source CT scanner. CT parameters were tube potentials, 140 and 80 kVp; exposure, 80 and 340 mAs/rot; and collimation, 14 x 1.2 mm. Bolus tracking was used in the descending aorta for timing (Ultravist 370). Bones were removed from the datasets using the 3 techniques and MIP datasets were generated. Two experienced radiologists assessed image quality ((1) correct removal of bones and preservation of vessels without artificial truncation, stenoses or occlusions of arteries; (2) minor errors with residual bone in the dataset or removal of side branches; (3) significant errors impeding diagnostic evaluation), number of vessel segmentation errors, and number of nonremoved bones. Additionally, time for MIP-generation was measured. The plaque removal tool was applied to DEBR MIPs and the outcome was rated as positive, neutral, or negative. DEBR showed better image quality than SBBR (P < 0.05; median image quality DEBR: 1; SBBR - MC: 3; SBBR + MC: 2). Less vessel segmentation errors occurred in DEBR (P < 0.05; median DEBR: 0; SBBR - MC: 5; SBBR + MC: 1). The number of nonremoved bones was not significantly different between DEBR and SBBR + MC, but significantly higher in SBBR - MC (median DEBR: 1; SBBR - MC: 2; SBBR + MC: 0). Time for generation of MIPs was lowest for SBBR - MC (P < 0.05), but also DEBR was significantly faster than manually corrected SBBR (DEBR: 160 +/- 16 seconds; SBBR - MC: 95 +/- 12 seconds; SBBR + MC: 373 +/- 69 seconds). The plaque removal tool lead to an improvement of image quality of the MIPs and a better depiction of the residual lumen in 43%. DEBR provides significant advantages, even over manually corrected SBBR. As it works completely automatically, it can effectively help to cope with the data load of CT angiography exams. Furthermore, it enables the removal of intraluminal plaques, which provides a benefit for the estimation of the residual lumen.

CT Angiography of Peripheral Arterial Occlusive Disease

Lower extremity computed tomography angiography (CTA) is an effective, noninvasive, and robust imaging modality that is being used increasingly to evaluate patients with peripheral arterial occlusive disease (PAOD). It is important for vascular and interventional radiologists, and vascular surgeons to be familiar with the strengths and limitations, diagnostic accuracy, and practical application of lower extremity CTA. In this article, we review the technical principles of image acquisition, visualization techniques to effectively interpret the large volumetric datasets generated, and the current practical application of lower extremity CTA with respect to PAOD.