Acquisition matters - how do scan parameters affect apparent diffusion coefficient estimates in pediatric...

Area of Science:

• Radiology
• Oncology
• Medical Imaging

Background:

• Apparent diffusion coefficient (ADC) from diffusion-weighted imaging (DWI) shows promise as a biomarker for pediatric rhabdomyosarcoma treatment response.
• Multicenter studies are necessary due to the rarity of this cancer, but introduce variability in imaging acquisition parameters.

Purpose of the Study:

• To assess how varying acquisition parameters influence ADC estimates in a multicenter rhabdomyosarcoma patient dataset.
• To identify critical parameters affecting ADC measurements in pediatric rhabdomyosarcoma.

Main Methods:

• Analysis of 195 scans from 114 pediatric and adolescent rhabdomyosarcoma patients across 22 centers.
• Evaluation of the impact of voxel size, b-values, and echo time on tumor ADC values.
• Specific investigation into the effect of the highest b-value on a subset of scans.

Main Results:

• Significant variability in acquisition parameters was observed across the cohort and individual centers.
• No single parameter significantly affected cross-sectional ADC estimates when corrected for multiple comparisons.
• A decrease in the highest b-value reduced ADC by 2.8% per 100 s mm⁻²; differing b-values between baseline and follow-up scans altered longitudinal ADC (P<0.05).

Conclusions:

• Despite wide variations in acquisition parameters, cross-sectional tumor ADC did not show significant differences.
• Changes in the highest b-value between baseline and follow-up scans can impact longitudinal ADC estimates.
• Maintaining a constant highest b-value is recommended for consistent longitudinal ADC assessment in rhabdomyosarcoma studies.