(2024) Lin | PCCT enables protocol-independent liver fat quantification

Daniel Stromer

PCCT-derived fat fraction (CTFF) showed excellent agreement with MRI proton density fat fraction (PDFF), supporting quantitative liver fat assessment using standardized PCCT attenuation values.

A single conversion formula—MRI PDFF (%) = −0.58 × CT (HU) + 43.1—remained accurate across 90, 120, and 140 kVp and both standard- and low-dose protocols.

Accuracy was maintained across different BMI and steatosis levels, while validation in patients with MASLD showed an ICC of 0.96 and a mean bias of only −0.2%, supporting PCCT as a potential tool for opportunistic liver fat quantification.

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Figure 2. Liver fat content measurement with photon-counting detector (PCD) CT and MRI-based proton density fat fraction (PDFF). Three regions of interest (circles) were delineated in the peripheral areas of the left, right anterior, and right posterior lobes of the liver. (A) Representative axial unenhanced 120-kVp standard-dose CT image (left) and corresponding MRI scan (right) in a 33-year-old man (body mass index, 26.2) diagnosed with metabolic dysfunction–associated steatotic liver disease (MASLD) in the asymptomatic cohort. (B) Representative axial unenhanced 120-kVp low-dose CT image (left) and corresponding MRI scan (right) in a 69-year-old woman (body mass index, 24.6) in the MASLD cohort. Body mass index was calculated as weight in kilograms divided by height in meters squared. FF = fat fraction.

Protocol

Detail	Value
Scanner	NAEOTOM Alpha
Software	VA50
Scan area	Entire liver and spleen
Scan mode	Spiral
Acquisition mode	QunatumPlus
Tube voltage [kV]	90, 120, 140
Effective mAs [mAs]	CARE Dose4D automatic
IQ level	90 (low dose), 145 (standard dose)
Dose modulation	CARE Dose4D
Rotation time [s]	0.25
Pitch	0.8
Detector slice collimation	144 × 0.4 mm
Slice thickness [mm]	1.0
Reconstruction increment [mm]	0.7
Reconstruction kernel	Br40
Iterative reconstruction	QIR 3
Reconstruction	70-keV virtual monoenergetic images
Contrast agent	None
Postprocessing	syngo.via MM Reading, VB60
Reference standard	MRI PDFF

Key Results

Parameter	Main finding
Conversion formula	MRI PDFF (%) = −0.58 × CT (HU) + 43.1
Asymptomatic validation	ICC 0.94; mean bias 0.04% ± 2.3
Protocol robustness	ICC 0.93–0.94 across 90–140 kVp; 0.95 low dose and 0.93 standard dose
CTFF error	Not significantly influenced by tube voltage, radiation dose, steatosis, or BMI
MASLD validation	ICC 0.96; mean bias −0.2% ± 2.1
Clinical implication	Standardized PCCT attenuation may enable protocol-independent quantitative and opportunistic liver fat assessment

Source:
Lin H, Xu X, Deng R, et al. Photon-counting Detector CT for Liver Fat Quantification: Validation across Protocols in Metabolic Dysfunction–associated Steatotic Liver Disease. Radiology. 2024;312(3). doi:10.1148/radiol.240038.