Repeatability of diffusion-weighted imaging in rectal cancer.

Area of Science:

• Radiology
• Oncology
• Medical Imaging

Background:

• Serial diffusion-weighted MRI (DW-MRI) using apparent diffusion coefficient (ADC) measurements is crucial for evaluating rectal cancer response to neoadjuvant therapy.
• Distinguishing true therapy-related changes from measurement variability is essential for accurate response assessment.

Purpose of the Study:

• To determine the repeatability of DW-MRI measurements of rectal tumor ADC.
• To quantify measurement variations in ADC to improve rectal cancer response evaluation.

Main Methods:

• 18 rectal cancer patients underwent daily 1.5T MR imaging over five days, including two identical DW-MRI sequences.
• Repeatability and intraobserver variation of tumor ADC measurements were analyzed using Bland-Altman plots.
• Repeatability coefficient was calculated as the 95% range of ADC values from identical DWI measurements, expressed as a percentage of the mean ADC.

Main Results:

• The mean tumor ADC value was 1.15 × 10(-3) mm(2)/s.
• The repeatability coefficient for ADC measurements was 9.8%.
• Intraobserver repeatability for ADC measurements was 4.7%.

Conclusions:

• A repeatability coefficient of 9.8% must be considered in serial DW-MRI for rectal cancer response evaluation.
• This coefficient accounts for variations introduced by observer judgment, patient factors, and MR spectrometer performance.
• Accurate interpretation of ADC changes requires accounting for these inherent measurement variations.