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

Area of Science:

• Radiology
• Medical Imaging
• Cardiovascular Imaging

Background:

• Computed tomography angiography (CTA) is crucial for diagnosing lower extremity vascular diseases.
• Optimizing radiation dose and contrast agent volume in CTA is essential for patient safety and reducing healthcare costs.
• Iterative reconstruction techniques have shown promise in improving image quality at lower radiation doses.

Purpose of the Study:

• To evaluate the efficacy of 80 kVp tube potential combined with iterative model reconstruction (IMR) for lower extremity CTA.
• To compare image quality metrics and radiation dose between standard and reduced-dose CTA protocols.
• To assess the performance of IMR versus hybrid iterative reconstruction (HIR) in lower extremity CTA.

Main Methods:

• A randomized study involving 60 patients undergoing lower extremity CTA.
• Group A (n=30) received a standard protocol (120 kVp, 180mAs, 100mL contrast, filtered back-projection).
• Group B (n=30) received reduced-dose protocols (80 kVp, 140mAs, 75mL contrast) with either HIR (P2) or IMR (P3).
• Image quality was assessed by comparing mean intravascular attenuation (MIA), noise, contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR), and subjective radiologist scores.
• Radiation dose parameters (CT volume dose index, dose-length product) were compared between groups.

Main Results:

• Protocols using 80 kVp (P2 and P3) demonstrated significantly higher MIA compared to the standard protocol (P1).
• IMR (P3) yielded significantly higher CNR and SNR than both P1 and P2.
• Interobserver agreement for image quality assessment was high across all protocols (Kappa values 0.78-0.81).
• Group B (80 kVp) exhibited significantly lower radiation doses (CTDIvol, DLP) than Group A (120 kVp).

Conclusions:

• Lower extremity CTA utilizing 80 kVp and IMR effectively reduces radiation and contrast agent requirements while maintaining diagnostic image quality.
• IMR provides superior image quality, especially for visualizing small-caliber vessels below the knee, compared to HIR.
• This optimized protocol represents a significant advancement in dose reduction strategies for lower extremity CTA.