Challenging Hounsfield Unit cutoffs: spectral thresholding for synthetic coronary plaque phantoms on photon-counting CT

Goldmann F, Wels M, Allmendinger T, Goldmann M, Gutjahr R, Jürgens M, Neumann J, Rist L, Stierstorfer K, Sühling M, Maier A (2026)

Publication Type: Journal article

Publication year: 2026

Journal

Book Volume: 13

Article Number: 024003

Journal Issue: 2

DOI: 10.1117/1.JMI.13.2.024003

Abstract

Purpose: Assess whether photon-counting computed tomography (PCCT) improves discrimination of vulnerable coronary soft-plaque components by extending one-dimensional Hounsfield Unit (HU) thresholding to a simple, interpretable two-dimensional linear rule. Approach: We generated a synthetic cohort of N=225 coronary plaque phantoms with randomized anatomy, tissue composition (lipid-rich, fibrotic, calcified), and iodine concentrations. Ultra–high-resolution PCCT data were reconstructed into polychromatic T3D, high energy threshold, material-specific, and virtual monoenergetic images (VMIs). Voxel-wise logistic regression implemented single-image (1D) and dual-image (2D) decision rules; performance was assessed by the area under the receiver operating characteristic curve (ROC-AUC). Partial-volume behavior was quantified as correctness versus Euclidean distance to the nearest out-of-class voxel using isotonic regression with a phantom-level bootstrap. Results: Combining T3D with low-keV VMI yielded the best separation of lipid-rich and fibrous soft-plaque subtypes. A 2D linear rule on T3D + VMI50 achieved AUC=0.925 (95% CI: [0.912, 0.937]), exceeding 1D thresholding on T3D (AUC=0.850; 95% CI: [0.821, 0.875]) and on VMI50 (AUC=0.814; 95% CI: [0.780, 0.843]). Correctness increased with distance to the nearest out-of-class voxel and was ≥95% for voxels at distances D≥0.28mm (lipid-rich) and D≥0.43mm (fibrous) (lower 95% CI bounds: 0.20 and 0.41 mm). Accuracy degraded below these thresholds. Conclusions: A transparent, affine 2D threshold that combines routinely reconstructed PCCT images improves voxel-wise discrimination of lipid-rich versus fibrous plaque over conventional HU binning, yielding higher AUCs with tighter 95% confidence intervals. The derived boundary-distance guidance indicates where voxel-level decisions remain reliable, supporting interpretable, clinically pragmatic plaque assessment.

Authors with CRIS profile

Involved external institutions

Siemens Healthineers (Germany) Germany (DE)

How to cite

APA:

Goldmann, F., Wels, M., Allmendinger, T., Goldmann, M., Gutjahr, R., Jürgens, M.,... Maier, A. (2026). Challenging Hounsfield Unit cutoffs: spectral thresholding for synthetic coronary plaque phantoms on photon-counting CT. Journal of Medical Imaging, 13(2). https://doi.org/10.1117/1.JMI.13.2.024003

MLA:

Goldmann, Florian, et al. "Challenging Hounsfield Unit cutoffs: spectral thresholding for synthetic coronary plaque phantoms on photon-counting CT." Journal of Medical Imaging 13.2 (2026).

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