Related Experiment Video
Updated: Jun 12, 2026
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Dynamic Lung Tumor Tracking for Stereotactic Ablative Body Radiation Therapy
Published on: June 7, 2015
Improving target delineation on 4-dimensional CT scans in stage I NSCLC using a deformable registration tool
Iris E van Dam1, John R van Sörnsen de Koste, Gerard G Hanna
1Department of Radiation Oncology, VU University Medical Center, Amsterdam, The Netherlands.
Summary
Deformable registration (DR) improved internal target volume (ITV) definition for lung tumors on 4D CT scans. DR-generated ITVs were more accurate than those created using maximum intensity projections (MIP).
Area of Science:
- Radiotherapy
- Medical Imaging
- Computational Anatomy
Background:
- Accurate target definition is critical for effective stereotactic radiotherapy of lung tumors.
- Four-dimensional computed tomography (4D CT) is used to visualize tumor motion during the respiratory cycle.
- Deformable registration (DR) offers a potential method for improving target volume delineation on 4D CT scans.
Purpose of the Study:
- To evaluate the utility of deformable registration (DR) for defining internal target volumes (ITVs) in lung tumors using 4D CT.
- To compare the accuracy of DR-based ITVs with ITVs generated using maximum intensity projections (MIP).
Main Methods:
- Three clinicians contoured gross tumor volumes (GTVs) on end-inspiration 4D CT images on two separate occasions.
- GTVs were also contoured across all respiratory phases and on MIP images.
- Auto-propagation of GTVs to other phases was performed using a B-spline algorithm (VelocityAI) for DR.
- Internal target volumes (ITVs) were generated: manually contoured, MIP-optimized, DR-propagated, and DR-optimized.
- Volume overlap was quantified using Dice's Similarity Coefficients (DSCs).
Main Results:
- Intra-clinician GTV contouring showed higher reproducibility (mean DSC 0.93) than inter-clinician reproducibility (mean DSC 0.88).
- In most patients, the optimized MIP-based ITV differed from the optimized DR-based ITV.
- The DSC between the optimized DR-based ITV and the DR-propagated ITV was significantly higher than that between the optimized DR-based ITV and the optimized MIP-based ITV.
Conclusions:
- Deformable registration (DR) provides a more accurate method for generating internal target volumes (ITVs) compared to maximum intensity projection (MIP) approaches for lung tumors.
- DR-based ITVs more closely approximated a clinically optimal target volume definition.
- This study supports the use of DR for improving target delineation accuracy in lung stereotactic radiotherapy.
