Detection of carotid artery stenosis: a comparison between 2 unenhanced MRAs and dual-source CTA

Clinical Application of Dark-blood Imaging in Head and Neck CT Angiography: Effect on Image Quality and Plaque Visibility

RATIONALE AND OBJECTIVES

The aim of this study was to explore the potential of a newly developed dark-blood imaging technique to improve image quality and plaque visibility in head and neck computed tomography (CT) angiography.

MATERIALS AND METHODS

Patients who underwent triphasic head and neck CT angiography scans from August 2021 to March 2023 were retrospectively enrolled (mean age 67.23 ± 10.81 [SD] years, range 43-85 years, 64.7% male). The CT protocol consists of pre-contrast, arterial and delayed phases. Dark-blood images were postprocessed with the contrast-enhancement boost (CE-boost) technique. The quantitative assessment involved evaluating the CT value, image noise, contrast-to-noise ratio (CNR), and signal-to-noise ratio (SNR) of calcified plaque and non-calcified plaque. The plaque CNR relative to the vessel lumen (CNRplaque-lumen), vessel wall (CNRplaque-wall), and adjacent muscle (CNRplaque-muscle) was respectively calculated. Two experienced radiologists independently evaluated the CT images (5, best; 1, worst) by four characteristics including calcified plaque visibility, non-calcified plaque visibility, diagnostic confidence, and overall image quality. Inter-rater variability was also evaluated. The artery stenosis rate and plaque burden on dark-blood images were measured and compared with arterial phases. The intraclass correlation coefficient (ICC) was used for consistency analysis. The diagnostic accuracy of dark-blood images for the stenosis rate was evaluated by the area under the curve (AUC).

RESULTS

A total of 43 patients with 54 calcified plaques and 34 non-calcified plaques were assessed in this study. When compared with pre-contrast and delayed phase, dark-blood images yielded significantly higher CNRplaque-lumen and CNRplaque-muscle of calcified (219.79 ± 159.20 and 181.23 ± 112.12, respectively) and non-calcified (30.30 ± 29.11 and 6.28 ± 4.75, respectively) plaques (all p < 0.001). Calcified plaque SNR of dark-blood showed equal or slightly lower than other phases (p > 0.05 or p = 0.02). A major increase was observed in the non-calcified plaque SNR of dark-blood compared to the arterial phase (5.56 ± 3.71 vs. 4.23 ± 3.56, p = 0.02), although there were no apparent differences compared to pre-contrast and delayed phases (p > 0.05). In subjective analyzes, the calcified plaque visibility (4.99 ± 0.07), non-calcified plaque visibility (4.62 ± 0.48), overall image quality (4.81 ± 0.34), and diagnostic confidence (4.74 ± 0.36) in dark-blood images dominated the highest scores (p < 0.001). The subjective scores of radiologists exhibited good consistency (all kappa value>0.7). The dark-blood image and the arterial phase image exhibited good consistency in identifying the stenosis rate (p < 0.001). In the evaluation of plaque burden, the interobserver agreement for dark-blood images was higher compared to arterial phase images (ICC = 0.870 vs. 0.729).

CONCLUSIONS

Compared to conventional triphasic head and neck CT angiography, the CE-boost derived dark-blood imaging demonstrated a significant improvement in image quality and visibility for both calcified and non-calcified plaque assessment.

Treatment of the Carotid In-stent Restenosis: A Systematic Review

Background and Purpose: In-stent restenosis (ISR) after carotid artery stent (CAS) is not uncommon. We aimed to evaluate therapeutic options for ISR after CAS. Methods: We searched PubMed and EMBASE until November 2, 2020 for studies including the treatment for ISR after CAS. Results: In total, 35 studies, covering 1,374 procedures in 1,359 patients, were included in this review. Most cases (66.3%) were treated with repeat CAS (rCAS), followed by percutaneous transluminal angioplasty (PTA) (17.5%), carotid endarterectomy (CEA) (14.3%), carotid artery bypass (1.5%), and external beam radiotherapy (0.4%). The rates of stroke & TIA within the postoperative period were similar in three groups (PTA 1.1%, rCAS 1.1%, CEA 1.5%). CEA (2.5%) was associated with a slightly higher rate of postoperative death than rCAS (0.7%, P = 0.046). Furthermore, the rate of long-term stroke & TIA in PTA was 5.7%, significantly higher than rCAS (1.8%, P = 0.036). PTA (27.8%) was also associated with a significantly higher recurrent restenosis rate than rCAS (8.2%, P = 0.002) and CEA (1.6%, P < 0.001). The long-term stroke & TIA and recurrent restenosis rates showed no significant difference between rCAS and CEA. Conclusions: rCAS is the most common treatment for ISR, with low postoperative risk and low long-term risk. CEA is an important alternative for rCAS. PTA may be less recommended due to the relatively high long-term risks of stroke & TIA and recurrent restenosis.

Utility of Dual-Layer Spectral-Detector CTA to Characterize Carotid Atherosclerotic Plaque Components: An Imaging-Histopathology Comparison in Patients Undergoing Endarterectomy

Background: The composition of non-calcified portions of carotid atherosclerotic plaque represents an important marker of plaque vulnerability and ischemia risk. Objective: To assess the utility of dual-layer spectral-detector CTA (DLCTA) parameters for carotid plaque component characterization, using histologic results from carotid endarterectomy (CEA) as reference. Methods: Seven patients (5 male, 2 female; 61.6±8.5 years old) with carotid plaque awaiting CEA were prospectively enrolled and underwent preoperative supra-aortic DLCTA. A neuroradiologist and pathologist performed joint slice-by-slice review of histologic slices of resected plaques and CTA images. ROIs were placed on non-calcified components [lipid-rich necrotic core (LRNC), intraplaque hemorrhage (IPH), fibrous tissue, loose matrix (LM)] on CTA images in comparison with corresponding histologic slices using anatomic landmarks. For each ROI, attenuation was recorded for polyenergetic images (CTPI) and virtual monoenergetic images with keV ranging from 40-140 (CT40-140keV); attenuation spectrum curve slope was calculated; and Z-effective value (representing effective atomic number) was recorded. DLCTA parameters were compared among plaque components. Results: Seven plaques with a total of 65 slices and 364 ROIs (159 fibrous tissue, 96 LRNC, 86 loose matrix, 23 IPH) were analyzed. All parameters (CTPI, CT40-140keV, slope from 40 to 140 keV, Z-effective value) showed significant differences between LRNC and the other components (all p<.001). For example, mean CTPI was 37.1±15.1 HU for LRNC, 58.4±21.6 HU for IPH, 69.7±20.5 HU for fibrous tissue, and 69.6±19.6 HU for loose matrix; mean CT40keV was 28.1±36.7 HU for LRNC, 87.5±48.9 HU for IPH, 106.3±47.5 HU for fibrous tissue, and 102.6±48.0 HU for loose matrix. AUC for differentiating LRNC from other components was highest (0.945) for CT40kev and decreased with higher keV; AUC for CTPI was 0.908. CT40kev also had highest accuracy (90.4%); at cutoff of 55.7 HU, CT40kev had 88.5% sensitivity and 90.9% specificity. For differentiating IPH from fibrous tissue and loose matrix, AUC was highest at 0.652 for CTPI and 0.645 for CT40kev. Conclusion: DLCTA showed strong performance in differentiating LRNC from other non-calcified plaque components; CT40kev had highest accuracy, outperforming conventional polyenergetic images. Clinical Impact: DLCTA parameters may help characterize carotid plaque composition as a marker of vulnerable plaque and ischemia risk.

Plaque burden assessment and attenuation measurement of carotid atherosclerotic plaque using virtual monoenergetic images in comparison to conventional polyenergetic images from dual-layer spectral detector CT

PURPOSE

To compare virtual monoenergetic images (VMIs) with conventional polyenergetic images (PI) of Dual-layer spectral detector CT angiography (DLCTA) in plaque burden assessment and attenuation measurement of carotid atherosclerotic plaques.

METHODS

Supra-aortic DLCTA imaging of thirty patients (8 female, mean ages 63.1 ± 7.5 years) were respectively reviewed. Lumen area, wall area, and calcified area of plaques were outlined and recorded. Normalized wall index (NWI) was calculated for plaque burden and compared between PI and different VMIs. The attenuation of the non-calcified, calcified area of the plaques, sternocleidomastoid muscle (SCM), as well as Z effective values were measured and compared.

RESULTS

Fifty carotid plaques (27 left, 23 right) of thirty patients were analyzed. The average values of lumen, wall, calcified areas and NWI on PI were 34.50 ± 20.57mm², 47.61 ± 19.94 mm², 5.25 mm² (1.35- 51.86 mm²), and 0.59 ± 0.16 respectively. No significant difference was found in the lumen area (p = 0.314), wall area (p = 0.600), and NWI (p = 0.980) between different VMIs and PI. A significant difference was found in the calcified area between VMIs and PI (p = 0.009). Attenuations of non-calcified and calcified components in carotid plaques were comparable to PI for 50-120 keV (all: p > 0.05) and 60-120 keVs (all p > 0.05), respectively. Z Effective values for non-calcified, calcified and SCM were 7.67 ± 0.42, 11.70 ± 1.22, and 7.45 ± 0.12, respectively.

CONCLUSIONS

Carotid plaque burden assessment was comparable between PI and VMIs at 40-120 keVs. Attenuations of non-calcified components in carotid plaques were comparable to PI for 50-120 keV VMIs of DLCTA. VMIs might provide more information on carotid plaque features.

CT-pathologic correlation of non-calcified atherosclerotic arterial plaques: a study using carotid endarterectomy specimens

OBJECTIVE

Pathologic features of atherosclerotic plaques on CT are not established. We compared CT values among pathologically confirmed plaque constituents and evaluated their ability to distinguish plaque constituents.

METHODS

50 histopathological images of carotid endarterectomy samples from 10 males and 2 females (age 54-74 years, average 65.9 years) were examined. We compared pre-operative CT [pre-contrast (CT-P), early post-contrast phase (CT-E), delayed post-contrast phase (CT-D)] of lipid-rich necrotic core (NC) and fibrous tissue (F) plaque components with pathological images. The ability of features to differentiate plaque components using several discrimination techniques were compared.

RESULTS

CT values of NC and F were 36 ± 13, 45 ± 11 (mean ± standard deviation, Hounsfield unit, HU), 41 ± 17, 69 ± 18, and 44 ± 16, 70 ± 13 in CT-P (p < 0.01), CT-E (p < 0.0001), and CT-D (p < 0.0001), respectively. The threshold, sensitivity, and accuracy for distinguishing NC from F were 44 HU, 74%, and 68%; 55 HU, 85%, and 85%; and 63 HU, 92%, and 84% in CTP, CT-E, and CT-D, respectively. CT-P had lower accuracy than CT-E and CT-D (both p < 0.05), but CT-E and CT-D were similar. CT-E and CT-D yielded 90 and 91% sensitivity and accuracy, respectively in linear discrimination analysis.

CONCLUSION

In both pre- and post-contrast CT, CT values were lower in NC than F. Although values overlapped, using two-phase post-contrast CTs improved discrimination ability.

ADVANCES IN KNOWLEDGE

Our findings may help to establish computer-aided diagnosis of vulnerable atherosclerotic plaques in future.

3D Black-Blood Luminal Angiography Derived from High-Resolution MR Vessel Wall Imaging in Detecting MCA Stenosis: A Preliminary Study

BACKGROUND AND PURPOSE

3D high-resolution vessel wall imaging is increasingly used for intracranial arterial diseases. This study compared the diagnostic performance of black-blood luminal angiography derived from 3D vessel wall imaging with source images of vessel wall imaging and TOF-MRA in detecting middle cerebral artery stenosis.

MATERIALS AND METHODS

Sixty-two patients with suspected MCA atherosclerosis underwent TOF-MRA, vessel wall imaging, and CTA. Intracranial black-blood luminal angiography was created from source images of vessel wall imaging using minimum intensity projection. The degree and length of MCA stenosis were measured on source images of vessel wall imaging, TOF-MRA, and black-blood luminal angiography and compared using CTA as a reference standard.

RESULTS

The image quality of black-blood luminal angiography was diagnostic in most patients. The intra- and interobserver agreement for both stenosis degree and length measurements was excellent for black-blood luminal angiography. It was comparable with that of source images of vessel wall imaging in grading stenosis. Compared with TOF-MRA, black-blood luminal angiography showed significantly higher sensitivity for the detection of severe stenosis (89.3% versus 64.3%, P = .039) and higher specificity for the detection of occlusion (95.4% versus 84.6%, P = .039). Lesion length estimated on source images of vessel wall imaging was significantly greater than that measured by CTA and black-blood luminal angiography (P < .001 and P = .010).

CONCLUSIONS

Black-blood luminal angiography is better than TOF-MRA in detecting severe stenosis and occlusion of the MCA. Compared with source images of vessel wall imaging, it is more accurate in evaluating stenosis length. Black-blood luminal angiography can be produced as a derivative from vessel wall imaging and implemented as an adjunct to vessel wall imaging and TOF-MRA without extra acquisition time.

Imaging Carotid Atherosclerosis Plaque Ulceration: Comparison of Advanced Imaging Modalities and Recent Developments

Atherosclerosis remains the leading cause of long-term mortality and morbidity worldwide, despite remarkable advancement in its management. Vulnerable atherosclerotic plaques are principally responsible for thromboembolic events in various arterial territories such as carotid, coronary, and lower limb vessels. Carotid plaque ulceration is one of the key features associated with plaque vulnerability and is considered a notable indicator of previous plaque rupture and possible future cerebrovascular events. Multiple imaging modalities have been used to assess the degree of carotid plaque ulceration for diagnostic and research purposes. Early diagnosis and management of carotid artery disease could prevent further cerebrovascular events. In this review, we highlight the merits and limitations of various imaging techniques for identifying plaque ulceration.

Principles and Clinical Application of Dual-energy Computed Tomography in the Evaluation of Cerebrovascular Disease

Dual-energy computed tomography (DECT) simultaneously acquires images at two X-ray energy levels, at both high- and low-peak voltages (kVp). The material attenuation difference obtained from the two X-ray energies can be processed by software to analyze material decomposition and to create additional image datasets, namely, virtual noncontrast, virtual contrast also known as iodine overlay, and bone/calcium subtraction images. DECT has a vast array of clinical applications in imaging cerebrovascular diseases, which includes: (1) Identification of active extravasation of iodinated contrast in various types of intracranial hemorrhage; (2) differentiation between hemorrhagic transformation and iodine staining in acute ischemic stroke following diagnostic and/or therapeutic catheter angiography; (3) identification of culprit lesions in intra-axial hemorrhage; (4) calcium subtraction from atheromatous plaque for the assessment of plaque morphology and improved quantification of luminal stenosis; (5) bone subtraction to improve the depiction of vascular anatomy with more clarity, especially at the skull base; (6) metal artifact reduction utilizing virtual monoenergetic reconstructions for improved luminal assessment postaneurysm coiling or clipping. We discuss the physical principles of DECT and review the clinical applications of DECT for the evaluation of cerebrovascular diseases.

Carotid and vertebral artery stenosis evaluated by contrast-enhanced MR angiography in nasopharyngeal carcinoma patients after radiotherapy: a prospective cohort study

OBJECTIVE

To investigate the incidence of carotid artery (CA) and vertebral artery (VA) stenosis by contrast-enhanced MR angiography (CE-MRA) in patients with nasopharyngeal carcinoma (NPC) after radiotherapy.

METHODS

72 patients with NPC after radiotherapy more than 3 years ago were recruited as irradiation group to investigate the incidence and degree of CA and VA stenosis by CE-MRA. The results were compared with those of the control group, which comprised 50 newly diagnosed patients with NPC who had not received radiotherapy.

RESULTS

There was a higher incidence of CA and VA stenosis in the irradiation group than in the control group in terms of patient number as well as vessel involvement. The incidence of significant (>50%) CA and VA stenosis, except for the basilar artery, was also higher in the irradiation group than in the control group. The most commonly detected stenosis in the irradiation group was found in the internal CA (ICA) and VA, followed by the external CA and common CA (CCA). CCA and/or ICA (CCA/ICA) stenosis was present in 67 (93.1%) of 72 patients, with 27 (37.5%) patients having significant CCA/ICA stenosis. The statistical analysis demonstrated that age at receiving CE-MRA scanning and time interval from radiotherapy were the independent predictors of significant CCA/ICA stenosis.

CONCLUSION

The CE-MRA scanning results showed that the incidence of stenosis seems to exist in a wider range of CAs and VAs in the patients with NPC after radiotherapy than in the patients who had not received radiotherapy, and the incidence of significant CCA/ICA stenosis is higher in patients with older age and longer interval from radiotherapy.

ADVANCES IN KNOWLEDGE

Radiation-induced CA and VA stenosis exists widely in patients with NPC after radiotherapy, and its prevalence is more common in patients with older age and longer interval from radiotherapy.