A ZTE vs. CT Quantitative Similarities: Volumetric, First- and Higher-order Radiomics Comparisons between Zero-echo-time MRI and Conventional CT for Evaluating Metastatic Bone Lesions and Healthy Bone

Abstract

Background: Zero-Echo-Time (ZTE) MRI is an advanced imaging technique designed to capture tissues with very short transverse relaxation times—such as short-T2 materials—that quickly lose signal after excitation and are often invisible to conventional MRI. ZTE enhances bone contrast, generating images that closely approximate those of computed tomography (CT) using ray-sum rendering and inverse-logarithm rescaling. Despite promising visual similarities, previous perception-based radiological observations have lacked quantitative validation. Our group previously demonstrated that oZTEo, GE Healthcare’s implementation of ZTE MRI, provides a clinically viable alternative to conventional CT for evaluating healthy bone. In this study, we aim to quantitatively compare oZTEo and CT in assessing various metastatic bone lesions and healthy bone.
Methods: Starting in July 2025, we integrated oZTEo into our institution’s routine musculoskeletal pelvic MRI protocols, using nine GE MRI scanners (two 3 Tesla and seven 1.5 Tesla). This prospective study included two cohorts: the metastatic arm enrolled 40 patients who underwent both CT and oZTEo scans for pelvic metastases within six months, while the healthy bone arm included 40 patients with matched inclusion criteria, for a total of 80 participants. We completed manual volume-of-interest (VOI) segmentations using MIM software: healthy hips in the healthy bone arm and metastatic lesions in the metastatic arm, for both oZTEo and CT. VOI histogram analysis was performed to assess intensity distributions between oZTEo and CT, with histograms from both modalities normalized using z-score standardization. First-order and higher-order radiomic features were then computed and compared between oZTEo and CT using two one-sided paired tests for equivalence.
Results: 20 (50%) lesions were sclerotic, 15 (38%) lytic, and 5 (12%) mixed.
Sclerotic lesions: In oZTEo vs. CT, volume was 8% lower for sclerotic lesion VOIs (p = 0.0, statistically equivalent). Delta Radiomics: 96% of features were statistically equivalent (p < 0.00047). The most dissimilar radiomic features were GLSZM large-area-low-gray-level-emphasis (p = 0.0009), GLSZM zone-variance (p = 0.0007), and GLSZM large-area-emphasis (p = 0.0007). Normalized intensity histograms showed a 93% overlap.
Lytic lesions: In oZTEo vs. CT, volume was 21% higher for lytic lesion VOIs (p = 0.0069, statistically equivalent). Delta radiomics: 66% of radiomic features were statistically equivalent (p < 0.00047). The most dissimilar features were NGTDM complexity (p = 0.0052), GLZM gray-level-non-uniformity-normalized (p = 0.0026), and first-order 90th percentile (p = 0.0025). Normalized intensity histograms showed a 78% overlap.
Mixed lesions: In oZTEo vs. CT, volume was 7% lower for mixed lesion VOIs (p = 0.001, statistically equivalent). Delta Radiomics: 32% of features were statistically equivalent (p < 0.00047). The most dissimilar features included GLSZM small-area-high-gray-level-emphasis (p = 0.113), GLDM dependence-entropy (p = 0.1012), and GLRLM long-run-high-gray-level-emphasis (p = 0.0815). Normalized intensity histograms showed 95% overlap.
Healthy marrow: oZTEo VOI volume was 8% lower than in CT (p = 0.031, statistically equivalent). Delta Radiomics: 100% of radiomic features were statistically equivalent (p < 0.00047). Normalized intensity histograms showed 94% overlap.
Conclusion: This study provides objective evidence that oZTEo and CT have similar intensity distributions and comparable radiomic features, offering quantitative validation beyond visual assessment. These findings support oZTEo as a clinically viable MRI alternative to conventional CT for evaluating both healthy bone and metastatic bone lesions.