Superiority of black-blood computed tomography over conventional computed tomography angiography in the identification of soft plaques: a prospective study

Abstract

Background: Carotid computed tomography angiography (CTA) has limited diagnostic value in evaluating the vulnerability of soft plaques. This study compared conventional CTA and black-blood computed tomography (BBCT) in terms of image quality and the ability to diagnose carotid soft plaques.

Methods: Patients who underwent carotid CTA and magnetic resonance (MR) vessel wall examination were included in this prospective study. The image quality of plaques was evaluated through objective evaluation [CT values, image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) based on CTA and BBCT] and subjective evaluation. Plaque burden was assessed with the normalized wall index (NWI) in CTA, BBCT, and MR images, as was the remodeling index (RI). The number of soft plaques in CTA, BBCT, and MR images was recorded. The sensitivity, specificity, and accuracy of an NWI higher than 0.56 and an RI higher than 1.0 from CTA and BBCT images in assessing the vulnerability of soft plaques were calculated with MR vessel wall images as a reference standard.

Results: A total of 37 patients comprising 53 soft plaques (25 males and 12 females) were analyzed. The average CT values, SNR, and CNR of soft plaques in BBCT were significantly higher compared to those in CTA (BBCT: 65.38±21.34, 16.31±7.69, 6.47±4.97; CTA: 45.58±14.09, 7.16±3.15, 4.45±2.83; all P values <0.05). The image noise in BBCT was significantly lower than that in CTA (BBCT: 10.73±3.75; CTA: 15.52±6.59; P<0.05), while the subjective image score of BBCT (3.04±0.51) was significantly higher than that of CTA (2.32±0.61) (P<0.001). The sensitivity and specificity of an NWI higher than 0.56 with BBCT were 0.98 and 0.86, respectively, which were superior to those with CTA at 0.83 and 0.57, respectively. Meanwhile, the sensitivity and specificity of an RI higher than 1.0 with BBCT were 0.86 and 0.95, respectively, which were superior to those with CTA at 0.71 and 0.85, respectively. The sensitivity and specificity of BBCT in diagnosing vulnerable plaques were 0.90 and 0.93, respectively, while those of CTA were 0.62 and 0.79, respectively. The area under the receiver operating characteristic curve of BBCT for diagnosing vulnerable plaques was 0.91 (95% CI: 0.803-0.973) while that for CTA was 0.70 (95% CI: 0.559-0.819; P<0.001).

Conclusions: Compared to conventional CTA, BBCT provides improved image quality and diagnostic performance in assessing carotid soft plaques.

Keywords: Vulnerable carotid plaque; black-blood computed tomography (BBCT); computed tomography angiography (CTA); magnetic resonance (MR); vessel wall.

Figure 1

Flowchart of patient inclusion. MR, magnetic resonance.

Figure 2

The subjective image quality scoring for CTA, BBCT, and MR vessel wall images. (A-C) Subjective scoring of CTA images ranging from 2 to 4 points. (D-F) Subjective scoring of BBCT images ranging from 2 to 4 points. (G-I) Subjective scoring of MR vessel wall images ranging from 2 to 4 points. The white arrows indicate soft plaques. BBCT, black-blood computed tomography; CTA, computed tomography angiography; MR, magnetic resonance.

Figure 3

The measurement of LA and TVA in CTA, BBCT, and MR vessel wall images. Measurement of LA and TVA in (A) CTA, (B) BBCT, and (C) MR vessel wall images. The green circles indicate the LA and vessel area. BBCT, black-blood computed tomography; CTA, computed tomography angiography; LA, lumen area; TVA, total vessel area; MR, magnetic resonance.

Figure 4

The measurement of the reference vessel area and TVA in CTA, BBCT, and MR vessel wall images. Measurement of the reference vessel area and TVA in (A,D) CTA, (B,E) BBCT, and (C,F) MR vessel wall. The green circles indicate (A-C) the reference vessel area and (D-F) the TVA. BBCT, black-blood computed tomography; CTA, computed tomography angiography; MR, magnetic resonance; TVA, total vessel area.

Figure 5

The ROC curve of NWI higher than 0.56 for CTA and BBCT images. The area under the ROC curve for BBCT images (green) was significantly greater than that for CTA images (purple), indicating better diagnostic accuracy. BBCT, black-blood computed tomography; CTA, computed tomography angiography; NWI, normalized wall index; ROC, receiver operating characteristic.

Figure 6

The ROC curve of PR for CTA and BBCT images. The area under the ROC curve for BBCT images (green) was significantly greater than that for CTA images (purple), indicating better diagnostic accuracy. BBCT, black-blood computed tomography; CTA, computed tomography angiography; PR, positive remodeling; ROC, receiver operating characteristic.

Figure 7

The diagnostic performance of LRNC and fibrous plaques in (A,D) CTA, (B,E) BBCT, and (C,F) MR vessel wall images. Display of different plaque components (white arrows) in BBCT images demonstrated high consistency with MR images as compared to CTA images. BBCT, black-blood computed tomography; CTA, computed tomography angiography; LRNC, lipid-rich necrotic core; MR, magnetic resonance.

Figure 8

The ROC curve for diagnosing vulnerable soft plaques from CTA and BBCT images. The area under the ROC curve for BBCT images (green) was higher than that for CTA images (purple), indicating the use of BBCT provided better diagnostic accuracy. BBCT, black-blood computed tomography; CTA, computed tomography angiography; ROC, receiver operating characteristic.