(2026) Hennes | Low-dose and low-contrast PCCT angiography of the aorta maintains diagnostic IQ

Daniel Stromer

Dedicated photon-counting CT protocols enabled up to 40% radiation dose reduction and 33% iodine reduction while maintaining diagnostic image quality for thoracoabdominal aortic CTA.

Even the combined low-dose/low-contrast (LD/LC) protocol provided objective and subjective image quality comparable to third-generation energy-integrating CT despite simultaneously reducing both radiation and contrast dose.

Low-dose PCCT achieved higher contrast-to-noise ratio (CNR) than EID-CT despite substantially lower radiation exposure, highlighting the dose-efficiency advantage of photon-counting technology.

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Figure 4. Representative image quality of the CT protocols. CT angiography in different patients with comparable body mass index generated with EID-CT (A) and PCD-CT with reduced radiation dose (B), reduced contrast agent dose (C) and a combination of both (D)

Source: Hennes JL, Krompaß K, Huflage H, et al. Retrospective assessment of low-dose and low-contrast agent protocols for photon-counting CT angiography of the aorta. International Journal of Cardiovascular Imaging. 2026. doi:10.1007/s10554-026-03757-y.

Protocol

LD = low dose

LC= low contrast

Detail	Value
Scanner	NAEOTOM Alpha (PCD-CT); comparator: SOMATOM Force (EID-CT)
Scan area	Thoracoabdominal aortic CTA
Scan mode	ECG-triggered high-pitch spiral
Acquisition mode	Quantum Plus
Scan direction	Cranio-caudal
Tube voltage [kV]	120
Effective mAs [mAs]	IQ-dependent
IQ level	IQ64 (standard & LC); IQ42 (LD & LD/LC)
Dose modulation	Automatic exposure control
CTDIvol [mGy]	Standard PCCT: 4.5 ± 0.7 • LC: 4.8 ± 1.0 • LD: 3.3 ± 0.8 • LD/LC: 2.8 ± 0.8 • EID-CT: 5.3 ± 0.4
Rotation time [s]	0.25
Pitch	3.2
Matrix	512 × 512 or 768 × 768 (PCCT, FOV-dependent); 512 × 512 (EID-CT)
Field of view [mm]	368 × 368 (adjusted to patient size)
Slice collimation [mm]	PCCT: 144 × 0.4 EID-CT: 192 × 0.6 (effective)
Slice width [mm]	3.0
Reconstruction increment [mm]	3.0
Reconstruction kernel	Bv36
Iterative reconstruction	QIR 3 (PCCT); ADMIRE 3 (EID-CT)
Virtual monoenergetic images	55 keV
Contrast agent	Imeron 350 mg I/mL
Contrast volume	Standard/LD: 60 mL • LC/LD-LC: 40 mL
Flow rate	3.5 mL/s (60 mL protocols); 2.5 mL/s (40 mL protocols)
Iodine dose	Standard/LD: 21 g • LC/LD-LC: 14 g
Bolus tracking	ROI in descending thoracic aorta, 100 HU threshold, 7 s delay
Saline chaser	30 mL (standard/LD); 20 mL (LC/LD-LC)

Key Results

Parameter	Main finding
Radiation dose	Low dose reduced CTDIvol by ~40% vs EID-CT (3.3 vs 5.3 mGy)
Combined protocol	Low dose/Low contrast maintained diagnostic image quality despite simultaneous 40% radiation and 33% iodine reduction
CNR	LD achieved significantly higher CNR than EID-CT (33.5 vs 25.1)
Low-contrast protocol	LC maintained CNR comparable to EID-CT despite one-third less iodine
Subjective image quality	LC rated superior to EID-CT; LD and LD/LC comparable to EID-CT
Clinical implication	Patient-adapted low-dose and low-contrast PCCT protocols can substantially reduce radiation and iodine exposure without compromising diagnostic performance.