PhD Scientific Days 2026

Health Sciences 2.

Imaging Inflammation Beyond MRI: Photon-counting CT with Iodine Mapping in Peripheral Arthritides

Name of the presenter

Horváth, Ákos

Institute/workplace of the presenter

Semmelweis Egyetem Orvosi Képalkotó Klinika

Authors

Dr. Horváth Ákos¹
1: Semmelweis Egyetem Orvosi Képalkotó Klinika

Text of the abstract

Introduction
Accurate assessment of inflammatory activity in peripheral immune-mediated arthritides is essential for differential diagnosis and treatment guidance. Contrast-enhanced MRI is the current reference standard; however, its performance may be limited by spatial resolution, restricted field of view, and susceptibility to motion artefacts. Photon-counting detector CT (PCD-CT) with iodine mapping enables high-resolution imaging and offers quantitative assessment of inflammatory changes.

Aims
To evaluate iodine maps from PCD-CT for detecting and characterising inflammatory activity compared with MRI and to assess quantitative iodine-based metrics.

Methods
10 patients prospectively underwent PCD-CT, MRI, and ultrasound of the hands and wrists within 6 hours. Synovitis, tenosynovitis, periarticular inflammation, and structure-specific involvement were assessed and graded. Quantitative parameters included synovial area, tenosynovial width, and iodine concentration. Paired MRI–iodine data were analysed for diagnostic performance, agreement, correlation, and ROC metrics. RAMRIS and PsAMRIS scores were reconstructed. MRI served as reference, while ultrasound was used supportively.

Results
Iodine maps showed high sensitivity and specificity for synovitis (89.8%, 95.7%) and tenosynovitis (89.1%, 96.0%), with excellent agreement (κ=0.91, κ=0.89). Sensitivity decreased in small joints and the fifth digit (~80% and ~65–70%). Detection rates were comparable overall. Synovial area showed strong agreement (ρ=0.89; CCC=0.96) with a small negative bias. Tenosynovial width showed strong correlation but limited agreement. Iodine concentration correlated moderately with grade (ρ≈0.5–0.6; AUC≈0.8–0.9). Iodine maps detected periarticular inflammation more frequently than MRI (30% vs 23%, p=0.002). RAMRIS and PsAMRIS scores correlated strongly between modalities (ρ≈0.91–0.97).

Conclusions
PCD-CT iodine mapping provides accurate detection of inflammatory activity with excellent agreement to MRI. Quantitative synovial assessment is robust, whereas tendon-related measures are less reliable. Increased detection of periarticular inflammation highlights its potential for differential diagnosis, while reduced sensitivity in small joints and the fifth digit warrants cautious interpretation.

Funding
This work was funded by an ESSR Research Grant.