Integrated framework for quantitative T2-weighted MRI analysis following prostate cancer radiotherapy

Area of Science:

• Medical Imaging
• Radiotherapy Research
• Quantitative MRI Analysis

Background:

• Longitudinal T2-weighted MRI (T2w) analysis in prostate cancer radiotherapy (RT) is challenging due to data acquisition variations.
• Accurate quantitative assessment of RT-induced changes requires robust image registration and intensity harmonization.

Purpose of the Study:

• To develop and validate a framework for quantitative analysis of longitudinal T2w MRIs following prostate cancer radiotherapy.
• To automate the detection of prostate, peripheral zone (PZ), and gross tumor volume (GTV) using deformable image registration.
• To harmonize T2w signal intensity across longitudinal scans for consistent quantitative measurements.

Main Methods:

• The REgistration and HARMonization (REHARM) framework was developed, incorporating deformable image registration and T2w signal-intensity harmonization.
• REHARM was applied to T2w data from a clinical trial (107 MRI exams, 23 patients) with pre- and post-RT scans.
• Image registration accuracy was assessed using DICE coefficients, and intensity normalization via histogram intersection. Longitudinal consistency was evaluated using repeatability coefficients and Pearson correlation.

Main Results:

• The REHARM framework significantly improved histogram intersections for prostate, PZ, and GTV.
• Automated contouring demonstrated superior repeatability in T2w intensity estimation compared to manual contours (r=0.9, p<0.0001 for GTV).
• Significant changes in T2w values pre- and post-RT were observed, indicating measurable radiation effects.

Conclusions:

• The developed REHARM methodology automates longitudinal MRI analysis, reducing acquisition-related variations and enhancing consistency.
• Quantitative characterization of RT-induced T2w changes provides new insights into radiation effects.
• This framework enables the development of prediction models for RT response in prostate cancer.