Abstract 5297: Dual-modality imaging of hepatocellular carcinoma

Abstract

Abstract Choline compounds are linked to malignancy since elevation of the intensity of choline peak reflects increased biosynthesis of membrane phospholipids and can be a marker for cellular proliferation. Positron Emission Tomography (PET) images an injected tracer dose (nM∼pM) of [11C]-choline while Proton MR Spectroscopy (1H MRS) can characterize endogenous choline-containing compounds usually in the mM range. There have been studies on brain and prostate cancers with both imaging modalities although correlation between the results from PET and MRS is inconsistent. The transient radiolabeled choline metabolism measured by PET is different from the relative steady total choline contents measured by MRS. However, it begs the question of whether the two imaging modalities are measuring the same metabolic pathways of choline in cancer. For primary Hepatocellular Carcinoma (HCC), there have been [11C]-choline PET studies, both pre-clinical and clinical, showing focal uptake. Likewise, there have been 1H-MRS studies of choline with animals and humans showing significantly high choline levels in HCC. So far, there is no comparison study reported to link the two measurements in HCC. This study was conducted with a woodchuck model of hepatitis viral infection-induced HCC, which is regarded as a naturally occurring animal model of human HCC with similar pathology and clinical behavior. The original objective of the study was to examine the effects of animals being fed and fasted on PET scans using [11C]-choline. MRI and MRS were added and performed immediately before PET imaging. Experiments were first performed with animals at the fed state using a 4T MR scanner with a human head coil. Dynamic PET images were then generated from a nearby clinical PET/CT scanner right after, spanning 50 minutes starting from [11C]-choline injection. Time-activity curves and tracer contrast uptake between focal uptake in HCC and that in the surrounding hepatic tissues were calculated in liver regions. The same animals were scanned again four days later following the exact same procedure, except that the animals were fasted over night. The results from PET imaging with [11C]-choline showed that the dietary state of fed or fast had little impact on radio-choline uptake in HCC while the results from 1H MRS of choline found similar choline/lipids ratios in HCC regardless of whether the animal was fed or fasted. These results are very promising for correlating the two measurements although further experiments are needed to confirm that the two imaging modalities are measuring related lipid metabolic pathways in HCC involving choline. This work is supported in part by NCI grants R01 CA095307 and U24 CA110943. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5297. doi:10.1158/1538-7445.AM2011-5297