Improving lower-extremity artery depiction and diagnostic confidence using dual-energy technique and popliteal artery monitoring in dual-low dose CT angiography

Abstract

To assess the utility of dual-energy CT scanning (DECTs) with popliteal artery (PA) monitoring in dual low-dose (radiation and contrast) lower-extremity CT angiography (LE-CTA). 135 patients undergoing LE-CTA were prospectively included and divided into three groups of 45 each. Group-A: conventional scanning, 105 mL of contrast, abdominal aorta monitoring; Group-B: low-dose DECTs, 95 mL of contrast, AA monitoring; Group-C: low-dose DECTs, 85 mL of contrast, PA monitoring. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR), as well as their elevations at seven arteries, were evaluated. Two radiologists conducted subjective assessments of overall image quality and vascular diagnosis in three arterial segments. They also recorded the visible branch grading in the lower-knee segment (LKS). Group-C reduced contrast and effective doses by 19.04% and 12.62%, respectively, compared to Group-A (P < 0.001). Group-C had the best SNR and CNR for four LKS arteries. Regarding SNR and CNR elevations, Group-C outperformed Group-B in distal arteries beyond the PA. In the LKS, Group-C performed best for subjective overall image quality, visible branch grading, and diagnostic confidence, as well as the inter-observer diagnostic consistency, followed by Group-B and Group-A (P < 0.001). DECTs with PA monitoring provides excellent depiction of lower-extremity arteries under dual low-dose conditions.

Keywords: Computed tomography angiography; Dual energy CT; Iodine contrast; Lower extremity arteries; Radiation dose.

Fig. 1

Flowchart showing the inclusion and exclusion of patients.

Fig. 2

Comparison of quantitative indexes of different groups (a) shows the comparison of SNR values of three groups at different ROI. (b) Shows the comparison of CNR values of three groups at different ROI. (c) Shows the SNR elevation of group B and group C at different ROI. (d) Shows the CNR elevation of group B and group C at different ROI. AA: abdominal aorta, CFA: common femoral artery, PA: popliteal artery; ATA: anterior tibial artery, PTA: posterior tibial artery, FA: fibular artery, DPA: dorsalis pedis artery; SNR, signal-to-noise ratio; CNR, contrast-to-noise ratio; *P < 0.05 for comparison of groups A and B; #P < 0.05 for comparison of groups A and C; &P < 0.05 for comparison of groups B and C.

Fig. 3

Comparison of subjective image quality and diagnosis confidence of three groups in different segments. AIS: Abdominal Iliac Segment; FPS: Femoral Popliteal Segment; LKS: Lower Knee Segment.

Fig. 4

A 70-year-old male patient with a history of smoking and intermittent claudication in the right lower limb underwent routine lower limb artery CTA (abdominal aorta monitoring). (a) Show abdominal lliac segment. (b) Show femoral popliteal segment. (c) Show lower knee segment. (d) Show maximum intensity projection of peripheral arteries. The overall image quality was moderate, with insufficient contrast enhancement in the LKS region. A senior physician diagnosed no significant abnormalities in the lower limb arteries, while the junior physician had low confidence in the LKS diagnosis. Subjective scores were AIS: 4, FPS: 3, LKS: 3, with a lower limb vessel grading of 2. Diagnostic confidence levels were AIS: 3, FPS: 3, LKS: 1.

Fig. 5

A 64-year-old female patient with hypertension underwent lower extremity DE-CTA (with abdominal aorta monitoring) due to leg pain. (a) Show abdominal lliac segment. (b) Show femoral popliteal segment. (c) Show lower knee segment. (d) Show maximum intensity projection of peripheral arteries. The image quality was good with significant contrast enhancement, though the visualization of below-knee arteries was faint. The senior physician diagnosed no significant abnormalities in the lower extremity arteries, but the junior physician expressed low confidence in diagnosing the LKS region. Subjective scores were AIS: 5, FPS: 4, LKS: 4; with a below-knee arterial grading of 3. Diagnostic confidence levels were AIS: 3, FPS: 3, LKS: 2.

Fig. 6

A 51-year-old male patient with diabetes and intermittent right lower limb pain underwent DE-CTA of the lower limb arteries with popliteal artery monitoring. (a) Show abdominal lliac segment. (b) Show femoral popliteal segment. (c) Show lower knee segment. (d) Show maximum intensity projection of peripheral arteries. The image quality was excellent, with significantly enhanced contrast and clear visualization of the vessels below the knee. Both physicians diagnosed severe stenosis and occlusion of the right posterior tibial artery as indicated by the arrow. The subjective scores were AIS: 5, FPS: 5, LKS: 5, with a lower limb vessel grading of 5. The diagnostic confidence levels were AIS: 3, FPS: 3, LKS: 3.