Redefining the target early during treatment. Can we visualize regional differences within the target volume using...

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.