Can Photon-Counting CT be an Alternative to MRI for Assessing Liver Fat Fraction?

Emerging research suggests significant agreement between photon-counting computed tomography (PCCT) and magnetic resonance imaging (MRI) with respect to hepatic fat fraction quantification.

In a new prospective study, recently published in Radiology, researchers compared contrast-enhanced PCCT fat quantification to MRI proton density fat fraction (PDFF) in 125 participants, liver biopsy in 27 participants, and controlled attenuation parameter (CAP) measurements derived from transient elastography in 26 participants. The 178-participsant cohort was comprised of people with known or suspected liver disease, according to the study.

The researchers found a 91 percent intraclass correlation coefficient (ICC) between PCCT and MRI PDFF for liver fat fraction assessment. They also noted a 92 percent ICC between the imaging modalities for participants without fibrosis and an 84 percent ICC for participants with fibrosis.

“PCCT-based assessment of liver steatosis showed excellent agreement with the clinical reference standard for noninvasive assessment of liver fat fraction, MRI PDFF, without evidence of systematic deviation between the two modalities. Notably, even the presence of a fibrotic liver parenchymal structure did not appear to impact the accuracy of the PCCT measurement method,” wrote lead study author Tatjana Dell, M.D., who is affiliated with the Department of Diagnostic and Interventional Radiology and Quantitative Imaging Lab Bonn at the University Hospital Bonn in Bonn, Germany, and colleagues.

Employing a 4.8 percent threshold for PCCT discrimination of steatosis, the researchers pointed out that PCCT offered similar sensitivity (81 percent) to MRI PDFF (86 percent).

The study authors noted a number of benefits with PCCT in comparison to MRI in this patient population.

“PCCT offers potential advantages over MRI, including faster scan times and high patient acceptance. Additionally, breathing artifacts are encountered less frequently on PCCT scans than on MRI scans. Patients with pacemakers and other implants can undergo PCCT without concern,” said Dell and colleagues.

While PCCT’s lower specificity for steatosis in contrast to MRI (71 percent vs. 83 percent) curtails the use of PCCT for primary screening of steatosis, the researchers emphasized ancillary detection benefit during routine CT exams.

“The additional information could help clinicians identify patients with steatosis at an early stage, depending on risk stratification,” added Dell and colleagues.

(Editor’s note: For related content, see “New Study Identifies Key Computed Tomography Findings for Post-Op Recurrence of Pancreatic Cancer,” “Abdominal CT Study Shows 20 Percent Reduction in Iodine Contrast with Photon Counting CT” and “Can Photon-Counting CT Facilitate a Viable Alternative to MRI for Liver Fat Quantification in Patients with MASLD?”)

Beyond the inherent limitations of a single-center study, the researchers conceded a small number of participants in the cohort with advanced steatosis and that all PCCT exams were performed with a single scanner. They also noted the high proportion of fibrosis in the biopsy group may have affected the study results.