# CBCT Image Superimposition for Longitudinal Monitoring of Mandibular Cyst Healing: A Technical Note

## TL;DR

This study shows how to track healing of jaw cysts using 3D imaging by aligning scans over time, improving accuracy and consistency.

## Contribution

A novel method for longitudinal monitoring of mandibular cyst healing using CBCT superimposition and semi-automatic segmentation.

## Key findings

- Lesion volume decreased by 26.0% from baseline to 6-month follow-up.
- Spatial subtraction analysis confirmed the magnitude and spatial distribution of bone healing.
- The method provides objective and anatomically precise monitoring of cyst regression.

## Abstract

To evaluate the effectiveness of spatial superimposition of cone‐beam computed tomography (CBCT) scans acquired at baseline and 6‐month follow‐up for monitoring bone healing in mandibular cystic lesions, aiming to reduce variability in conventional volumetric comparisons and enhance accuracy, reproducibility, and spatial fidelity of radiographic assessments.

Two CBCT scans of a single patient (baseline, T0; follow‐up, T1) were imported into 3D Slicer v5.8.0. The mandible was isolated by manually cropping a region of interest, and the cystic lesion was segmented semi‐automatically using the Grow from Seeds tool. A rigid six‐degree‐of‐freedom registration aligned T1 to T0; the resulting transformation matrix was applied to the T1 segmentation to enable direct voxel‐wise comparison. Lesion volumes were measured, and spatial subtraction analysis quantified the resorbed area.

Lesion volume decreased from 1841.64 mm3 at T0 to 1362.62 mm3 at T1, corresponding to an absolute reduction of 479.02 mm3 (26.0%). The subtraction mask accurately localized regressed voxels, confirming both the magnitude and spatial distribution of bone healing.

Potential limitations related to CBCT artifacts and the need for operator‐dependent manual steps should be considered when interpreting the results. Overall, CBCT superimposition with semi‐automatic segmentation provides an objective, consistent, and anatomically precise approach for monitoring mandibular cyst regression and may represent a useful tool to support conservative management strategies.