Contrast media and radiation dose optimization with task-based automatic keV selection: a proof-of-concept study with photon-counting detector CT.

Objectives: To evaluate whether task-based automatic keV selection of photon-counting detector (PCD)-CT with optimizing radiation and contrast media (CM) dose yields consistent image quality in CT angiography (CTA).

Materials And Methods: PCD-CTA of the aorta was performed in six healthy minipigs across two scan sessions, with virtual monoenergetic images (VMI) reconstructed. In the first session, three protocols were conducted: the reference protocol A1 simulated standard CTA (210 mg iodine/kg CM, image quality (IQ)-level 117, non-contrast task, VMI: 70 keV); protocol A2 reduced radiation while keeping CM dose constant (210 mgI/kg, IQ-level 117, vascular task, VMI: 55 keV); and protocol A3 reduced CM dose while maintaining radiation (164 mgI/kg, IQ-level 117, non-contrast task, VMI: 55 keV). In the second session, protocols A2 and A3 were repeated as B1 and B2 to assess reproducibility, and protocol B3 further reduced the radiation dose with increased CM dose (252 mgI/kg, IQ-level 81, vascular task, VMI: 55 keV). Aortic CNR was measured; subjective assessments included contrast, noise, IQ, and visibility of intrahepatic arteries using a 4-point discrete visual scale.

Results: The median CTDIvol was 3.8 mGy (A1, A3), 2.4 mGy (A2, B1), 3.9 mGy (B2), and 1.6 mGy (B3), respectively; median CM doses were 23 mL (A1, A2, B1), 18 mL (A3, B2), and 28 mL (B3), respectively. CNR was comparable across protocols (p = 0.906-0.947). Subjective metrics indicated diagnostic image quality (scores ≥ 2) for all protocols, with A1 and A3 having higher noise (p = 0.007-0.008) and lower vascular contrast (p = 0.003-0.008). Subjective image quality (p = 0.226-0.342) and visibility of intrahepatic arteries (p = 0.604-0.873) were similar.

Conclusion: Task-based automatic keV selection enables optimization of radiation and CM dose in PCD-CTA while maintaining image quality. Protocols can be balanced to either save radiation or CM dose, depending on individual patient needs.

Key Points: Question Balancing radiation and contrast media doses in CT angiography is essential, yet the full potential of photon-counting detector (PCD)CT for dose optimization remains underexplored. Findings Task-based automatic keV selection of PCD-CT enabled a 22% contrast reduction at constant radiation or a 58% radiation dose reduction with a compensatory 20% increase in contrast media. Clinical relevance Task-based automatic keV selection of PCD-CT allows individualized dose optimization by balancing radiation exposure and contrast media volume. This approach can improve patient safety by tailoring protocols to either radiation- or contrast media reduction.