Repeatability and reproducibility of prostate apparent diffusion coefficient values on a 1.5 T magnetic resonance...

Area of Science:

• Medical Physics
• Oncology
• Radiotherapy

Background:

• Integrated magnetic resonance linear accelerator (MR-Linac) systems enable adaptive radiation therapy.
• Apparent diffusion coefficient (ADC) tracking is crucial for biologically based dose adaptation.
• Prostate cancer treatment requires accurate monitoring of anatomical and physiological changes.

Purpose of the Study:

• To assess the repeatability and reproducibility of intraprostatic apparent diffusion coefficient (ADC) measurements.
• To evaluate the effectiveness of deformable image registration (DIR) in correcting for inter-fraction prostate changes.
• To establish the precision of ADC measurements for guiding adaptive radiotherapy.

Main Methods:

• 20 prostate cancer patients treated on a 1.5 T MR-Linac underwent repeat ADC measurements.
• Deformable image registration (DIR) aligned T2-weighted images and ADC maps across fractions.
• Intraclass correlation coefficients (ICC) and percent repeatability coefficient (%RC) analyzed ADC in defined regions-of-interest (ROIs).

Main Results:

• Excellent repeatability and reproducibility (ICC > 0.86) for mean and 10th percentile ADC in ROIs.
• Moderate repeatability and reproducibility (ICC > 0.542) for individual voxels.
• Low within-fraction %RC (4.2-17.9%) for mean/10th percentile ADC, higher between fractions (10.2-36.8%).

Conclusions:

• Deformable image registration (DIR) ensures excellent ADC repeatability and reproducibility in clinical ROIs.
• Voxel-level ADC tracking precision is established for biologically based adaptive radiotherapy.
• MR-Linac systems with DIR facilitate accurate ADC monitoring for personalized prostate cancer treatment.