Diffusion-Weighted MRI for Treatment Response Assessment in Osteoblastic Metastases-A Repeatability Study

Area of Science:

• Radiology
• Oncology
• Medical Imaging

Background:

• Osteoblastic metastases pose challenges for morphologic imaging-based treatment response assessment.
• Apparent diffusion coefficient (ADC) is a potential imaging biomarker for treatment response.
• Reliability of ADC requires low measurement variance compared to differences between viable and nonviable metastases.

Purpose of the Study:

• To assess the repeatability of in vivo ADC measurements in osteoblastic metastases.
• To determine if ADC differences between viable and nonviable metastases are significant relative to measurement variability.
• To evaluate ADC as a reliable marker for treatment response in osteoblastic metastases.

Main Methods:

• Analysis of repeated in vivo ADCmedian measurements in 65 osteoblastic metastases from nine patients.
• Inclusion of phantom measurements to assess measurement repeatability.
• Utilized PSMA-PET as a surrogate for bone metastasis viability.
• Calculated repeatability coefficients and compared mean ADC values between viable and nonviable metastases.

Main Results:

• The relative repeatability coefficient (%RC) for in vivo ADCmedian measurements was 12.9% (phantom: 5.8%).
• ADCmedian values ranged from 595×10-6mm2/s to 2090×10-6mm2/s.
• Nonviable metastases exhibited 63% higher ADCmedian values compared to viable metastases (p < 0.001).

Conclusions:

• ADC measurements demonstrate a small repeatability coefficient relative to the difference between viable and nonviable metastases.
• ADC measurements meet the technical requirements for reliable treatment response evaluation in osteoblastic metastases.
• ADC is a promising imaging biomarker for monitoring treatment efficacy in bone metastases.