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Redefining the target early during treatment. Can we visualize regional differences within the target volume using
Maarten Lambrecht1, Hans Van Herck2, Frederik De Keyzer3
1Department of Radiation Oncology, Leuvens Kankerinstituut, University Hospitals Leuven, Campus Gasthuisberg, Belgium.
Purpose:
In head and neck cancer, diffusion weighted MRI (DWI) can predict response early during treatment. Treatment-induced changes and DWI-specific artifacts hinder an accurate registration between apparent diffusion coefficient (ADC) maps. The aim of the study was to develop a registration tool which calculates and visualizes regional changes in ADC.
Methods:
Twenty patients with stage IV HNC treated with primary radiotherapy received an MRI including DWI before and early during treatment. Markers were manually placed at anatomical landmarks on the different modalities at both time points. A registration method, consisting of a fully automatic rigid and nonrigid registration and two semi-automatic thin-plate spline (TPS) warps was developed and applied to the image sets. After each registration step the mean registration errors were calculated and ΔADC was compared between good and poor responders.
Results:
Adding the TPS warps significantly reduced the registration error (in mm, 6.3 ± 6.2 vs 3.2 ± 3.3 mm, p<0.001). After the marker based registration the median ΔADC in poor responders was significantly lower than in good responders (7% vs. 21%; p<0.001).
Conclusions:
This registration method allowed for a significant reduction of the mean registration error. Furthermore the voxel-wise calculation of the ΔADC early during radiotherapy allowed for a visualization of the regional differences of ΔADC within the tumor.
Insights
A new registration tool accurately visualizes regional changes in apparent diffusion coefficient (ADC) maps during head and neck cancer radiotherapy. This method improves early prediction of treatment response by reducing registration errors.
Area of Science:
- Radiology
- Oncology
- Medical Imaging
Background:
- Diffusion-weighted MRI (DWI) aids in early prediction of treatment response in head and neck cancer (HNC).
- Accurate registration of apparent diffusion coefficient (ADC) maps is challenging due to treatment-induced changes and DWI artifacts.
- Regional ADC changes can provide valuable insights into treatment efficacy.
Purpose of the Study:
- To develop and evaluate a novel registration tool for calculating and visualizing regional ADC changes.
- To improve the accuracy of ADC map registration in HNC patients undergoing radiotherapy.
- To correlate early ADC changes with treatment response.
Main Methods:
- Twenty stage IV HNC patients undergoing radiotherapy had MRI with DWI before and during treatment.
- A registration method combining automatic rigid/nonrigid and semi-automatic thin-plate spline (TPS) warps was developed.
- Mean registration errors were calculated, and changes in ADC (ΔADC) were compared between good and poor responders.
Main Results:
- The TPS warps significantly reduced mean registration error from 6.3 ± 6.2 mm to 3.2 ± 3.3 mm (p<0.001).
- After registration, the median ΔADC was significantly lower in poor responders (7%) compared to good responders (21%) (p<0.001).
Conclusions:
- The developed registration method significantly reduces mean registration error in ADC maps.
- Voxel-wise calculation of ΔADC enables visualization of regional differences within the tumor.
- This tool facilitates early assessment and prediction of radiotherapy response in head and neck cancer.
