Related Experiment Video
Updated: Sep 19, 2025
Longitudinal Micro-Computed Tomography Image Analysis for User-Defined Region of Interest in Critical-Sized Bone Defects
Published on: June 24, 2025
Optimizing region of interest size and placement for clinical opportunistic CT trabecular bone Hounsfield unit
Janelle N Sobecki1, Diane Krueger2, Perry J Pickhardt3
1Department of Obstetrics & Gynecology, Division of Gynecologic Oncology, University of Wisconsin-Madison School of Medicine and Public Health, 600 Highland Ave, Madison, WI, 53792, H4/656, USA. janelle.sobecki@wisc.edu.
Purpose:
No formal guidance exists regarding optimal opportunistic computed tomography (CT) region of interest (ROI) size or placement to clinically obtain bone Hounsfield unit (HU) data. Using clinical CT scans, this study evaluated ROI size/placement and assessed HU reproducibility.
Methods:
Three non-radiologists independently identified the L1 and L4 vertebral body centroid and then placed varying size circular ROIs on axial and sagittal images of 30 clinical CT scans. A 200-mm2 ROI location was varied left to right, anterior to posterior, and cranial to caudal. Intra- and inter-observer reliability was determined using intraclass correlation coefficients (ICC). ROI size and axial/sagittal HU comparison was performed by ANOVA and t-test. Precision of 200-mm2 axial and sagittal ROIs was assessed in a second cohort of 30 patients with two scans obtained within 16 days.
Results:
Vertebral body centroid placement was nearly identical between readers (ICC > 0.99). Intra- and inter-observer reliability was excellent for all ROI sizes on both projections (ICC > 0.95). Statistically, but not clinically, significant differences, less than 8 HU, were present between various sized ROIs at L1, with no difference at L4. Axial HU was generally higher than sagittal for all ROI sizes at L1 and L4 by ~ 5-12 HU. In the precision cohort, L1 and L4 HU %CV was 4.8-7.9% yielding least significant change values of 10-16 HU.
Conclusions:
Non-radiologists can reliably identify the vertebral body centroid and measure HU. For clinical use, we recommend a 200-mm2 circular ROI placed at the vertebral body centroid on L1 axial imaging.
