Correlation of 3T Diffusion-weighted MRI and ¹⁸F-FDG-PET/CT in Liver Metastases: SUV Versus ADC

Positron emission tomography/computed tomography (PET/CT) and magnetic resonance imaging (MRI) are widely used in the diagnosis and follow-up of liver metastases. Both modalities provide anatomical and functional information and have advantages and disadvantages. The objective of this study was to investigate the correlation between apparent diffusion coefficient (ADC) and standardized uptake value (SUV) values in metastatic liver lesions.

Abdominal magnetic resonance (MR) scans performed between April 2021 and 2024 using the 3T MR scanner were retrospectively evaluated. Thirty-three patients with liver metastases, less than one month between magnetic resonance imaging (MRI) and PET/CT, no treatment during this period, and lesions larger than 1 cm were included in the study. In each MRI scan, an index lesion was selected for ADC measurement. The radiologist and nuclear medicine specialist measured the same index lesion without the patient being informed of the results.

The mean age of the 33 patients was 59±12 years, with 17 (51%) men and 16 (49%) women. The mean size of the index lesions was 27±9 mm. In MRI, mean ADC_min: (0.54±0.2) ×10^-3mm²/s; ADC_mean: (1.02±0.2) ×10^-3mm²/s; ADC_max: (1.48±0.44) ×10^-3mm²/s; and region of interest area was calculated as 6±4.6 cm². In PET/CT, mean SUV_mean: 5.8±3.3; SUV_peak: 6.8±4.3; SUV_max: 10.7±5.6; and metabolic tumor volume: 12.1 (7.4-20.7) cm³. No statistically significant correlation was found between ADC and SUV values.

There was no correlation between ADC and SUV values in liver metastases. Prospective studies with a large patient group are needed.