Abstract
PurposeMetabolism and water diffusion may have a relationship or an effect on each other in the same tumor. Knowledge of their relationship could expand the understanding of tumor biology and serve the field of oncologic imaging. This study aimed to evaluate the relationship between metabolism and water diffusivity in hepatic tumors using a simultaneous positron emission tomography/magnetic resonance imaging (PET/MRI) system with F-18 fluorodeoxyglucose (FDG) and to reveal the metabolic and diffusional characteristics of each type of hepatic tumor.MethodsForty-one patients (mean age 63 ± 13 years, 31 male) with hepatic tumors (18 hepatocellular carcinoma [HCC], six cholangiocarcinoma [CCC], 10 metastatic tumors, one neuroendocrine malignancy, and six benign lesions) underwent FDG PET/MRI before treatment. Maximum standard uptake (SUVmax) values from FDG PET and the apparent diffusion coefficient (ADC) from the diffusion-weighted images were obtained for the tumor and their relationships were examined. We also investigated the difference in SUVmax and ADC for each type of tumor.ResultsSUVmax showed a negative correlation with ADC (r = -0.404, p = 0.009). The median of SUVmax was 3.22 in HCC, 6.99 in CCC, 6.30 in metastatic tumors, and 1.82 in benign lesions. The median of ADC was 1.039 × 10−3 mm/s2 in HCC, 1.148 × 10−3 mm/s2 in CCC, 0.876 × 10−3 mm/s2 in metastatic tumors, and 1.323 × 10−3 mm/s2 in benign lesions. SUVmax was higher in metastatic tumors than in benign lesions (p = 0.023). Metastatic tumors had a lower ADC than CCC (p = 0.039) and benign lesions (p = 0.004). HCC had a lower ADC than benign lesions, with a suggestive trend (p = 0.06).ConclusionOur results indicate that SUVmax is negatively correlated with ADC in hepatic tumors, and each group of tumors has different metabolic and water diffusivity characteristics. Evaluation of hepatic tumors by PET/MRI could be helpful in understanding tumor characteristics.
Highlights
The liver is an important organ from the oncologic perspective
SUVmax was higher in metastatic tumors than in benign lesions (p = 0.023)
Our results indicate that SUVmax is negatively correlated with apparent diffusion coefficient (ADC) in hepatic tumors, and each group of tumors has different metabolic and water diffusivity characteristics
Summary
Primary hepatic tumors are common in the presence of underlying chronic liver diseases [1]. The liver is one of the most common organs for cancer metastasis. Up to 20% of individuals have a benign hepatic lesion, the most common being cavernous hemangioma and focal nodular hyperplasia [2]. F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET)/ CT is used routinely to diagnose and stage disease and to evaluate the response to treatment for many cancers [3,4]. Cancer cells have increased intracellular accumulation of the glucose analog FDG due to increased glucose uptake and glycolysis. Brownian motion of water molecules in tissue can be quantified by the apparent diffusion coefficient (ADC). Like the SUV from PET, the ADC has been used clinically to differentiate benign from malignant tumors [8,9] and to assess tumor aggressiveness, characterization subtype, and predict prognosis [10,11,12]
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