Evaluation of benign vs malignant hepatic lesions with positron emission tomography

A dual-tracer approach using [11C]CH and [18F]FDG in HCC clinical decision making

BACKGROUND

Early detection of recurrent or progressive HCC remains the strongest prognostic factor for survival. Dual tracer PET/CT imaging with [11C]CH and [18F]FDG can further increase detection rates as both tracers entail different metabolic pathways involved in HCC development. We investigated dual-tracer PET/CT in clinical decision making in patients suspected of recurrent or progressive HCC. All HCC patients who underwent both [11C]CH and [18F]FDG PET/CT in our institute from February 2018 to December 2021 were included. Both tracer PET/CT were within 4 weeks of each other with at least 6-month follow-up. Patients underwent dual tracer PET/CT because of unexplained and suspicious CT/MRI or sudden rise of serum tumour markers. A detected lesion was considered critical when the finding had prognostic consequences leading to treatment changes.

RESULTS

Nineteen patients who underwent [11C]CH and [18F]FDG PET/CT were included of which all but six patients were previously treated for HCC. Dual-tracer critical finding detection rate was 95%, with [18F]FDG 68%, and [11C]CH 84%. Intrahepatic HCC recurrence finding rate was 65% for both tracers. [18F]FDG found more ablation site recurrences (4/5) compared to [11C]CH (2/5). Only [11C]CH found two needle tract metastases. Both tracers found 75% of the positive lymph nodes. Two new primary tumours were found, one by [18F]FDG and both by [11C]CH.

CONCLUSIONS

Our study favours a dual-tracer approach in HCC staging in high-risk patients or when conventional imaging is non-conclusive.

Optimized 18F-FDG PET-CT Method to Improve Accuracy of Diagnosis of Metastatic Cancer

The diagnosis of cancer by FDG PET-CT is often inaccurate owing to subjectivity of interpretation. We compared the accuracy of a novel normalized (standardized) method of interpretation with conventional non-normalized SUV. Patients (n = 393) with various malignancies were studied with FDG PET/CT to determine the presence or absence of cancer. Target lesions were assessed by two methods: (1) conventional SUV_max (conSUV_max) and (2) a novel method that combined multiple factors to optimize SUV (optSUVmax), including the patient's normal liver SUV_max, a liver constant (k) derived from a review of the literature, and use of site-specific thresholds for malignancy. The two methods were compared to pathology findings in 154 patients being evaluated for mediastinal and/or hilar lymph node (MHLNs) metastases, 143 evaluated for extra-thoracic lymph node (ETLNs) metastases, and 96 evaluated for liver metastases. OptSUV_max was superior to conSUV_max for all patient groups. For MHLNs, sensitivity was 83.8% vs. 80.7% and specificity 88.7% vs. 9.6%, respectively; for ETLNs, sensitivity was 92.1% vs. 77.8% and specificity 80.1% vs. 27.6%, respectively; and for lesions in the liver parenchyma, sensitivity was 96.1% vs. 82.3% and specificity 88.8% vs. 23.0%, respectively. Optimized SUV_max increased diagnostic accuracy of FDG PET-CT for cancer when compared with conventional SUV_max interpretation.

Update on PET Radiopharmaceuticals for Imaging Hepatocellular Carcinoma

Numerous positron emission tomography (PET) targets for detection and staging of hepatocellular cancer have been developed in recent years. Hepatocellular carcinomas (HCCs) are clinically and pathologically heterogeneous tumours with a high tendency to be aggressive and unresponsive to chemotherapy. Early detection is essential, and the need for an adequate imaging biomarker, which can overcome some of the limitations of conventional radiological imaging, is persistent. Flourine-18 (18F) flourodeoxyglucose (FDG), the most widely used PET radiopharmaceutical, has proven disappointing as a possible staple in the evaluation of HCC. This disappointment had led to experimentation with carious radiotracers, such as the choline derivatives, acetate, and prostate-specific membrane antigen, which appear to complement and/or enhance the role of FDG. In this study, we look at the various PET radiopharmaceuticals that have been used for imaging HCC and the particular pathways that they target in HCC and liver cancers.

Can PSMA-Targeting Radiopharmaceuticals Be Useful for Detecting Hepatocellular Carcinoma Using Positron Emission Tomography? An Updated Systematic Review and Meta-Analysis

BACKGROUND

Several studies proposed the use of positron emission tomography (PET) with Prostate-Specific Membrane Antigen (PSMA)-targeting radiopharmaceuticals in hepatocellular carcinoma (HCC). Our aim is to calculate the detection rate (DR) of this examination in HCC with a meta-analysis.

METHODS

A comprehensive literature search of studies on the DR of PET/CT or PET/MRI with PSMA-targeting radiopharmaceuticals in HCC was performed. Original articles evaluating these imaging examinations both in newly diagnosed HCC patients and HCC patients with disease relapse were included. Pooled DR including 95% confidence intervals (95% CI) was calculated. Statistical heterogeneity was also assessed using the I2 test.

RESULTS

The meta-analysis of six selected studies (126 patients) provided a DR of 85.9% for PET imaging with PSMA-targeting radiopharmaceuticals in the diagnosis of HCC. Moderate statistical heterogeneity among the included studies was found (I2 = 56%).

CONCLUSIONS

The quantitative data provided demonstrate the high DR of PET/CT or PET/MRI with PSMA-targeting radiopharmaceuticals for HCC lesion detection. However, more studies are needed to confirm the promising role of PSMA-targeted PET in HCC.

Artificial Intelligence in the Diagnosis of Hepatocellular Carcinoma: A Systematic Review

Hepatocellular carcinoma ranks fifth amongst the most common malignancies and is the third most common cause of cancer-related death globally. Artificial Intelligence is a rapidly growing field of interest. Following the PRISMA reporting guidelines, we conducted a systematic review to retrieve articles reporting the application of AI in HCC detection and characterization. A total of 27 articles were included and analyzed with our composite score for the evaluation of the quality of the publications. The contingency table reported a statistically significant constant improvement over the years of the total quality score (p = 0.004). Different AI methods have been adopted in the included articles correlated with 19 articles studying CT (41.30%), 20 studying US (43.47%), and 7 studying MRI (15.21%). No article has discussed the use of artificial intelligence in PET and X-ray technology. Our systematic approach has shown that previous works in HCC detection and characterization have assessed the comparability of conventional interpretation with machine learning using US, CT, and MRI. The distribution of the imaging techniques in our analysis reflects the usefulness and evolution of medical imaging for the diagnosis of HCC. Moreover, our results highlight an imminent need for data sharing in collaborative data repositories to minimize unnecessary repetition and wastage of resources.

Intrapatient variability of 18F-FDG uptake in normal tissues

Objectives

To investigate the effect of serum glucose level and other confounding factors on the variability of maximum standardized uptake value (SUVmax) in normal tissues within the same patient on two separate occasions and to suggest an ideal reference tissue.

Materials and Methods

We retrospectively reviewed 334 18F-FDG PET/CT scans of 167 cancer patients including 38 diabetics. All patients had two studies, on average 152 ± 68 days apart. Ten matched volumes of interest were drawn on the brain, right tonsil, blood pool, heart, lung, liver, spleen, bone marrow, fat, and iliopsoas muscle opposite third lumber vertebra away from any pathological 18F-FDG uptake to calculate SUVmax.

Results

SUVmax of the lungs and heart were significantly different in the two studies (P = 0.003 and P = 0.024 respectively). Only the brain uptake showed a significant moderate negative correlation with the level of blood glucose in diabetic patients (r = −0.537, P = 0.001) in the first study, while the SUVmax of other tissues showed negligible or weak correlation with the level of blood glucose in both studies.

The liver showed significant moderate positive correlation with body mass index (BMI) in both studies (r = .416, P = <0.001 versus r = 0.453, P = <0.001, respectively), and blood pool activity showed significant moderate positive correlation with BMI in the first study only (r = 0.414, P = <0.001). The liver and blood pool activities showed significant moderate negative correlation with 18F-FDG uptake time in first study only (r = −0.405, P-value = <0.001; and r = −0.409, P-value = <0.001, respectively).

In the multivariate analysis, the liver showed a consistent effect of the injected 18F-FDG dose and uptake duration on its SUVmax on the two occasions. In comparison, spleen and muscle showed consistent effect only of the injected dose on the two occasions.

Conclusion

The liver, muscle, and splenic activities showed satisfactory test/retest stability and can be used as reference activities. The spleen and muscle appear to be more optimal reference than the liver, as it is only associated with the injected dose of 18F-FDG.

18F-FDG PET/CT image findings of a dog with adrenocortical carcinoma

Background

In human medicine, 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) has been used to differentiate between benign and malignant adrenal tumors and to identify metastases. However, canine adrenocortical carcinomas identified by 18F-FDG PET/computed tomography (CT) have not been reported.

Case presentation

A 13-year-old, castrated male, Cocker Spaniel dog with severe systolic hypertension exhibited an adrenal mass approximately 3.6 cm in diameter on ultrasonography. There was no evidence of pulmonary metastasis or vascular invasion on thoracic radiography and abdominal ultrasonography, respectively. 18F-FDG PET/CT was performed to identify the characteristics of the adrenal mass and the state of metastasis. One hour after injection of 5.46 MBq/kg 18F-FDG intravenously, the peripheral region of the adrenal mass visually revealed an increased 18F-FDG uptake, which was higher than that of the liver, and the central region of the mass exhibited necrosis. The maximal standardized uptake value (SUV) of the adrenal mass was 3.24; and relative SUV, calculated by dividing the maximal SUV of the adrenal tumor by the mean SUV of the normal liver, was 5.23. Adrenocortical carcinoma was tentatively diagnosed and surgical adrenalectomy was performed. Histopathologic examination of the resected adrenal mass revealed the characteristics of an adrenocortical carcinoma. After adrenalectomy, systolic blood pressure reduced to below 150 mmHg without any medication.

Conclusion

This is the first case report of 18F-FDG PET/CT findings in a dog with suspected adrenocortical carcinoma and may provide valuable diagnostic information for adrenocortical carcinoma in dogs.

Cavernous Hemangioma: A Potential Pitfall at Delayed 18F-FDG PET/CT Scan

ABSTRACT

We report the case of a 72-year-old woman who underwent neoadjuvant chemotherapy, right quadrantectomy (invasive ductal carcinoma, G3, pT2pN1pMx), and adjuvant radiotherapy. Two years later, a follow-up CT revealed a hepatic nodule of approximately 1 cm suspected for metastasis. 18F-FDG PET/CT was performed for restaging. Standard total-body 18F-FDG PET/CT acquisition showed no abnormal 18F-FDG uptake in the hepatic nodule. A delayed 18F-FDG PET/CT acquisition of upper abdomen was performed at 180 minutes postradiopharmaceutical injection and showed increased 18F-FDG uptake in the hepatic nodule. After nodule resection, the histological examination proved a cavernous hemangioma.

Characteristics of 18F-FDG and 18F-FDOPA PET in an 8-year-old neutered male Yorkshire Terrier dog with glioma: long-term chemotherapy using hydroxyurea plus imatinib with prednisolone and immunoreactivity for PDGFR-β and LAT1

An 8-year-old neutered male Yorkshire Terrier dog presented with head pressing, vestibular ataxia, neck tenderness, and no oculocephalic reflex. A demarcated lesion in the pons was identified on MRI. The patient was tentatively diagnosed with a glioma and was treated with hydroxyurea plus imatinib and prednisolone. After 30 days of therapeutic treatment, the patient showed a clear improvement in neurological signs, which lasted for 1117 days. On day 569 after the initiation of treatment, ¹⁸F-fluorodeoxyglucose (FDG)-positron emission tomography (PET) was performed with no significant findings on visual analysis. The average and maximal standardized uptake values (SUVs) were 1.92 and 2.29, respectively. The tumor-to-normal-tissue (T/N) ratio was 0.97. The first evidence of clinical deterioration was noticed on day 1147. On day 1155, 3,4-dihydroxy-6-[¹⁸F]-fluoro-l-phenylalanine (¹⁸F-FDOPA)-PET was performed. High uptake of ¹⁸F-FDOPA was observed in the intracranial lesion. The mean and maximal SUVs of the tumor were 1.59 and 2.29, respectively. The T/N ratio was 2.22. The patient was euthanized on day 1155 and histopathologic evaluations confirmed glioma (astrocytoma). This case shows that chemotherapy with hydroxyurea plus imatinib may be considered in the treatment of canine glioma. Furthermore, this is the first case describing the application of ¹⁸F-FDG and ¹⁸F-FDOPA in a dog with glioma.

Extrahepatic metastases from hepatocellular carcinoma: multimodality image evaluation

The most prevalent primary malignancy of the liver is hepatocellular carcinoma (HCC); its poor prognosis is mainly related to intrahepatic recurrence and extrahepatic metastases. However, survival from HCC has improved due to better control of the primary tumor, the development of newer treatment modalities, including liver transplant, together with advances in imaging techniques. Therefore, the significance of patient management as corresponds with distant metastases has increased; since the proper evaluation and detection of extrahepatic metastases is crucial to optimize potential therapy for patients. Conventional imaging like CT, MRI play crucial rule in patient's diagnosis and qualifying for a certain type of therapy. More recently, a molecular imaging tool with radiolabeled deoxyglucose and fluorocholine has proved its promising value as a complementary tool to conventional studies. In this review, the frequent sites of metastases and HCC spread are discussed as well as the imaging findings as seen by both conventional imaging techniques and by molecular imaging tools, namely 18F-Choline PET/CT, and FDG PET. The implications of guiding treatment planning have also been discussed.

18F-FDG PET/CT of hepatocellular adenoma subtypes and review of literature

INTRODUCTION

This study evaluates 18F-FDG PET/CT imaging characteristics of pathologically proven hepatocellular adenoma (HCA) subtypes.

METHODS

This is a retrospective review of an institutional database (2011-2017) for subjects with a pathologic diagnosis of hepatic adenomas established within 6 months of a pre-treatment 18F-FDG PET/CT exam. An expert pathological review by a hepatopathologist was performed to confirm diagnosis and subtype HCA. A review of the 18F-FDG PET/CT exams was performed by two board-certified nuclear radiologists in consensus. Corresponding demographic and clinical data were obtained by electronic chart review.

RESULTS

Nine subjects were identified. An HCA subtype was established in seven subjects (4 HNF1A-mutated and 3 Inflammatory). The mean HCA lesion size was 2.8 cm (range 0.6-6.2, SD 2.0) with a mean SUVmax of 5.9 (range 2.1-18.9, SD 5.1). The SUV values of HNF1A-mutated HCA were significantly higher than inflammatory HCA: lesion SUVmax (5.3 ± 1.48 vs. 2.8 ± 0.59, p < 0.033), lesion-to-liver SUVmax ratio (1.4 ± 0.22 vs. 0.8 ± 0.21, p = 0.031), lesion SUVmean (3.6 ± 0.37 vs. 2.0 ± 0.46, p = 0.0086).

CONCLUSION

HNF1A-mutated HCA may have greater SUV values than inflammatory HCA on 18F-FDG PET/CT exams. However, there are contradictory data in the literature and further investigation is warranted.

18-F Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography of a Large Inflammatory-Hepatocellular Adenoma

We report a case of an 81-year-old male evaluated for a liver space-occupying lesion. US-guided biopsy and immunohistochemistry were suggestive of hepatocellular adenoma (HCA)-inflammatory (with telangiectasia). Serial 18-F fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography scans revealed a heterogeneously enhancing hypermetabolic mass in the right lobe of the liver, remaining stable for a span of 3 years. This case highlights that benign rare tumors of the liver such as HCA can be intensely FDG avid and that uptake cannot conclude its malignant transformation.

Prognostic Value of Metabolic Imaging Data of 11C-choline PET/CT in Patients Undergoing Hepatectomy for Hepatocellular Carcinoma

Simple Summary

Few data are available for the use of ¹¹C-choline positron emission tomography/computed tomography (PET/CT) in patients with hepatocellular carcinoma (HCC). The aim of the study was to analyze the clinical impact of this metabolic imaging in patients with HCC candidates for hepatectomy. Seven parameters were recorded for PET/CT in 60 patients. The Cox regression for overall survival (OS) showed that Barcelona stages (p = 0.003) and metabolic tumor volume (MTV) (p = 0.026) were the only factors independently associated with OS and furthermore, curve analysis revealed MTV ability in predicting OS. Patients with MTV ≥ 380 had worse OS (p = 0.015). The use of ¹¹C-choline PET/CT allows for better prognostic refinement in patients undergoing hepatectomy for HCC: integration of such metabolic modality into HCC staging system should be considered.

Abstract

¹¹C-choline positron emission tomography/computed tomography (PET/CT) has been used for patients with some types of tumors, but few data are available for hepatocellular carcinoma (HCC). We queried our prospective database for patients with HCC staged with ¹¹C-choline PET/CT to assess the clinical impact of this imaging modality. Seven parameters were recorded: maximum standardized uptake value (SUVmax), mean standardized uptake value (SUVmean), liver standardized uptake value (SUVliver), metabolic tumor volume (MTV), photopenic area, metabolic tumor burden (MTB = MTVxSUVmean), and SUVratio (SUVmax/SUVliver). Analysis was performed to identify parameters that could be predictors of overall survival (OS). Sixty patients were analyzed: fourteen (23%) were in stage 0-A, 37 (62%) in stage B, and 9 (15%) in stage C of the Barcelona classification. The Cox regression for OS showed that Barcelona stages (HR = 2.94; 95%CI = 1.41–4.51; p = 0.003) and MTV (HR = 2.11; 95%CI = 1.51–3.45; p = 0.026) were the only factors independently associated with OS. Receiver operating characteristics curve analysis revealed MTV ability in discriminating survival (area under the curve (AUC) = 0.77; 95%CI = 0.57–097; p < 0.001: patients with MTV ≥ 380 had worse OS (p = 0.015)). The use of ¹¹C-choline PET/CT allows for better prognostic refinement in patients undergoing hepatectomy for HCC. Incorporation of such modality into HCC staging system should be considered.

Case Report: Long-Term Chemotherapy With Hydroxyurea and Prednisolone in a Cat With a Meningioma: Correlation of FDG Uptake and Tumor Grade Assessed by Histopathology and Expression of Ki-67 and p53

A 15.5-year-old, neutered, male, domestic shorthair cat was presented with neurologic dysfunctions. At presentation, an obtunded mental status and vestibular ataxia were identified. On neurologic examination, postural reactions were decreased-to-absent in all four limbs, and pupillary light reflexes showed bilaterally delayed results. Magnetic resonance imaging was performed, and a demarcated lesion was identified in the third ventricle. The cat was tentatively diagnosed with a brain tumor, which was suspected to be a meningioma. The cat was treated with hydroxyurea and prednisolone. Mental status was considered more alert, and ataxia improved following treatment. On the 106th day after the commencement of treatment, a ¹⁸F-fluorodeoxyglucose (FDG)-positron emission tomography (PET) scan was performed. On the PET images, a hypermetabolic region was found in the lesion. The average standardized uptake value of FDG was 2.47, and the tumor-to-normal-tissue ratio was 1.25. The cat died 408 days following the commencement of treatment, and a grade 1 meningioma was confirmed by postmortem histopathology. Immunohistochemistry for Ki-67 and p53 was performed. The labeling indices of Ki-67 and p53 were 2.56 and 0%, respectively. This case shows that chemotherapy with hydroxyurea and prednisolone may be considered in the treatment of feline meningiomas. Furthermore, this is the first case describing the application of FDG-PET to visualize a naturally occurring meningioma in a cat.

Tumor heterogeneity for differentiation between liver tumors and normal liver tissue in 18F-FDG PET/CT

AIM

 Malignancies show higher spatial heterogeneity than normal tissue. We investigated, if textural parameters from FDG PET describing the heterogeneity function as tool to differentiate between tumor and normal liver tissue.

METHODS

 FDG PET/CT scans of 80 patients with liver metastases and 80 patients with results negative upper abdominal organs were analyzed. Metastases and normal liver tissue were analyzed drawing up to three VOIs with a diameter of 25 mm in healthy liver tissue of the tumoral affected and results negative liver, whilst up to 3 metastases per patient were delineated. Within these VOIs 30 different textural parameters were calculated as well as SUV. The parameters were compared in terms of intra-patient and inter-patient variability (2-sided t test). ROC analysis was performed to analyze predictive power and cut-off values.

RESULTS

 28 textural parameters differentiated healthy and pathological tissue (p < 0.05) with high sensitivity and specificity. SUV showed ability to differentiate but with a lower significance. 15 textural parameters as well as SUV showed a significant variation between healthy tissues out of tumour infested and negative livers. Mean intra- and inter-patient variability of metastases were found comparable or lower for 6 of the textural features than the ones of SUV. They also showed good values of mean intra- and inter-patient variability of VOIs drawn in liver tissue of patients with metastases and of results negative ones.

CONCLUSION

 Heterogeneity parameters assessed in FDG PET are promising to classify tissue and differentiate malignant lesions usable for more personalized treatment planning, therapy response evaluation and precise delineation of tumors for target volume determination as part of radiation therapy planning.

Radiolabelled PSMA PET/CT or PET/MRI in hepatocellular carcinoma (HCC): a systematic review

Introduction

Radiolabelled prostate-specific membrane antigen PSMA-based PET/CT or PET/MRI is a whole-body imaging technique usually performed for the detection of prostate cancer lesions. PSMA has been also demonstrated to be expressed by the neovasculature of many other solid tumors. The aim of this review is to evaluate the possible diagnostic role of radiolabelled PSMA PET/CT or PET/MRI in patients with hepatocellular carcinoma, by summarizing the available literature data.

Methods

A wide literature search of the PubMed/MEDLINE, Scopus, Embase and Cochrane library databases was made to find relevant published articles about the diagnostic performance of radiolabelled PSMA binding agents in PET/CT or PET/MRI imaging of patients with hepatocellular carcinoma.

Results

Ten case reports and three studies showed that hepatocellular carcinoma is PSMA-avid.

Conclusion

Radiolabelled PSMA imaging seems to be useful in analyzing hepatocellular carcinoma. Further studies enrolling a wider population are needed to clarify the real clinical and diagnostic role of radiolabelled PSMA in this setting.

Comparison of PET imaging of activated fibroblasts and 18F-FDG for diagnosis of primary hepatic tumours: a prospective pilot study

PURPOSE

This study aimed to compare the performance of ⁶⁸Ga-labelled fibroblast activating protein inhibitor (FAPI) PET and ¹⁸F-FDG PET for imaging of hepatic tumours.

METHODS

We prospectively assessed 20 patients with suspected intrahepatic lesions. Tumour radiological features, pathology, or follow-up examinations were assessed as ground truth in correlation with PET scans. Semiquantitative analysis was additionally performed by measuring the standardised uptake value (SUV). Tumour-to-liver background ratios (TBR) were calculated and compared between ⁶⁸Ga-FAPI PET and ¹⁸F-FDG PET. FAPI expression was assessed by immunochemistry in samples obtained from 7 patients with hepatocellular carcinomas (HCC)/intrahepatic cholangiocarcinoma (ICC) or granulomas.

RESULTS

Primary intrahepatic tumours, including 16 HCC in 14 patients and 4 ICC in 3 patients with extrahepatic metastases, were determined by histology (n = 14) and clinical examinations (n = 3). Based on visual analysis, 17 patients presented elevated ⁶⁸Ga-FAPI uptake (sensitivity: 100%, specificity: 100%), while 7 patients presented ¹⁸F-FDG avid tumours (sensitivity: 58.8%, specificity: 100%). ⁶⁸Ga-FAPI PET/CT identified 17 extrahepatic metastases vs. 13 in ¹⁸F-FDG PET/CT in 2 ICC patients. Three benign liver nodules in three patients showed negligible uptake in dual-PET scans. The SUV_{max_HCC} = 8.47 ± 4.06 and TBR_{max_HCC} = 7.13 ± 5.52, and SUV_{max_ICC} = 14.14 ± 2.20 TBR_{max_ICC} = 26.46 ± 4.94 in ⁶⁸Ga-FAPI-04 PET/CT were significantly higher than the ¹⁸F-FDG uptake presenting SUV_{max_HCC} = 4.86 ± 3.58 and TBR_{max_HCC} = 2.39 ± 2.21, and SUV_{max_ICC} = 9.19 ± 3.60 and TBR_{max_ICC} = 2.39 ± 2.21 (all p values < 0.05). ICC patients showed higher levels of FAPI uptake in the primary hepatic lesions compared to extrahepatic metastases, TBR_{max_ICC} = 15.18 ± 5.80 (p = 0.04).

CONCLUSIONS

⁶⁸Ga-FAPI PET-CT has superior potential in the detection of primary hepatic malignancy compared to ¹⁸F-FDG.

FDG-PET/CT imaging findings of hepatic tumors and tumor-like lesions based on molecular background

The usefulness of whole-body 18-fluoro-2-deoxyglucose (FDG)-fluorodeoxyglucose positron emission (PET)/computed tomography (CT) is established for assessment of disease staging, detection of early disease recurrence, therapeutic evaluation, and predicting prognosis in various malignancies; and for evaluating the spread of inflammation. However, the role of FDG-PET/CT for the liver is limited because CT and magnetic resonance imaging (MRI) can provide an accurate diagnosis of most tumors. In addition, in other potentially useful roles there are several pitfalls in the interpretation of FDG uptake in PET/CT imaging. Accurate evaluation demands knowledge of the FDG uptake of each lesion, including potential negative and positive uptakes, and requires an understanding of the underlying background of the molecular mechanisms. The degree of FDG uptake is dependent on cellular metabolic rate and the expression of glucose transporter, hexokinase, and glucose-6-phosphatase, which in turn are closely affected by biological characteristics such as pathological category (e.g., adenocarcinoma, squamous cell carcinoma, small cell cancer, transitional cell cancer, neuroendocrine tumor, sarcoma, lymphoma), tumor differentiation, histological behavior (e.g., solid, cystic, mucinous), and intratumoral alterations (e.g., necrosis, degeneration, hemorrhage). Correlation with the CT and MRI findings, which also precisely depict the pathological findings, is important to avoid misdiagnosis.

Emerging role of 18F-fluorodeoxyglucose positron emission tomography for guiding management of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of major causes of cancer mortality worldwide. For decades, ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) has been widely used for staging, predicting prognosis, and detecting cancer recurrence in various types of malignant diseases. Due to low sensitivity of FDG PET for detecting intrahepatic HCC lesions, the clinical value of FDG PET in HCC patients has been limited. However, recent studies with diverse analytic methods have shown that FDG PET has promising role in aiding management of HCC patients. In this review, we will discuss the clinical role of FDG PET for staging, predicting prognosis, and evaluating treatment response in HCC. Further, we will focus on recent clinical studies regarding implication of volumetric FDG PET parameters, the significance of FDG uptake in HCC for selecting treatment and predicting treatment response, and the use of radiomics of FDG PET in HCC.

Joint Consensus Statement of the Indian National Association for Study of the Liver and Indian Radiological and Imaging Association for the Diagnosis and Imaging of Hepatocellular Carcinoma Incorporating Liver Imaging Reporting and Data System

Hepatocellular carcinoma (HCC) is the 6th most common cancer and the second most common cause of cancer-related mortality worldwide. There are currently no universally accepted practice guidelines for the diagnosis of HCC on imaging owing to the regional differences in epidemiology, target population, diagnostic imaging modalities, and staging and transplant eligibility. Currently available regional and national guidelines include those from the American Association for the Study of Liver Disease (AASLD), the European Association for the Study of the Liver (EASL), the Asian Pacific Association for the Study of the Liver, the Japan Society of Hepatology, the Korean Liver Cancer Study Group, Hong Kong, and the National Comprehensive Cancer Network in the United States. India with its large population and a diverse health infrastructure faces challenges unique to its population in diagnosing HCC. Recently, American Association have introduced a Liver Imaging Reporting and Data System (LIRADS, version 2017, 2018) as an attempt to standardize the acquisition, interpretation, and reporting of liver lesions on imaging and hence improve the coherence between radiologists and clinicians and provide guidance for the management of HCC. The aim of the present consensus was to find a common ground in reporting and interpreting liver lesions pertaining to HCC on imaging keeping LIRADSv2018 in mind.

Evidence-based management of incidental focal uptake of fluorodeoxyglucose on PET-CT

Focal incidental uptake, with or without CT abnormalities, is a common finding on fluorodeoxyglucose PET/CT and evidence-based management for this type of uptake is lacking. This article reviews the evidence on focal incidental uptake including the incidence of malignancy, differential diagnosis and imaging criteria which can be used to further characterize it. The article focusses on PET rather than CT criteria. The strength of the evidence base is highly variable ranging from systematic reviews and meta-analyses to a virtual absence of evidence. Caution needs to be used when using standardized uptake values (SUVs) reported in other studies due to interpatient and institution observed variation in SUVs. There is sufficient evidence to permit specific suggestions on how to interpret the foci and recommend further management in the: pituitary (investigate when SUVmax >4.1), thyroid (investigate all), breast (investigate all), lung parenchyma (if focus of fluorodeoxyglucose without a CT nodule, no further investigations), colon (investigate all foci with SUVmax >5.9, urgently if SUVmax >11.4), adrenals (criteria depend on if patient has cancer) and prostate gland (investigate in males aged >50 years or >40 years if peripheral uptake or patient has other risk factors). There is some evidence to guide further management for the parotid gland, naso-orophaynx, oesophagus, pancreas, uterus and ovaries. There is insufficient evidence to guide management for the liver, spleen, kidneys, gallbladder, testis and bone, for these organs patient characteristics and other guidelines will likely be of more use in determining further management.

Inflammatory and Ischemic Post Liver Transplant Complications Mimic Malignancy on 18F-FDG PET/CT

A 65-year-old male patient with a one year history of liver transplantation was referred for an ¹⁸F-fluoro-2-deoxy-D-glucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) to rule out post transplant lymphoproliferative disease. Multiple foci of intense abnormal ¹⁸F-FDG uptake were seen in the transplanted liver which were concerning for malignancy. Explantation of the liver approximately 1 month following the PET/CT revealed multiple inflammatory and ischemic changes including large bile duct necrosis, acute cholangitis, bile duct obstruction changes and periportal fibrosis, with no evidence of malignancy. We present the ¹⁸F-FDG PET/CT image findings of this case.

Perfusion CT and PET with 18F-FDG and 18F-FCh in the complex diagnosis of hepatocellular carcinoma

Background

The purpose of the study to evaluate possibilities of CT-perfusion and PET methods with 18F-FDG and 18F-fluorocholine in the complex diagnosis of hepatocellular carcinoma. The study included the results of PET/CT with 18F-FDG, 18F-FCh and CT-perfusion of the liver in 18 patients with histologically confirmed diagnosis of hepatocellular carcinoma (HCC). Depending on the degree of tumor differentiation, all patients were divided into 3 groups - patients with highly differentiated (6 patients), moderately differentiated (4 patients), and low-differentiated HCC (8 patients).

Results

Average values of maxSUV in the group of patients with highly differentiated HCC in PET/CT with 18F-FDG and 18F- fluorocholine in a solid component of tumor reached 3.51 and 18.24, respectively; in patients with moderately differentiated HCC - 3.91 and 12.32, respectively; in patients with low-differentiated HCC - 9.58 and 9.70, respectively. Average values of CT perfusion imaging in a solid component of the tumor in the group of patients with highly differentiated HCC were the following: BF - 55,33 ml/100 ml/min, BV - 13,71 ml/100 ml, ALP - 52,41 ml/100 ml/min, PVP - 10.81 ml/100 ml/min (p ≤ 0,05), in the group of patients with moderately differentiated HCC: BF - 52,78 ml/100 m /min, BV - 12,23 ml/100 ml, ALP - 47,26 ml/100 ml/min, PVP - 9,10 ml/100 ml/min (p ≤ 0.05), in the solid component of low-differentiated HCC: BF - 46,96 ml/100 ml/min, BV - 9,49 ml/100 ml, ALP - 40.54 ml/100 ml/min, PVP - 7,66 ml/100 ml/min (p ≤ 0,05).

Conclusions

The diagnostic capabilities of the complex of PET/CT techniques with 18F-FDG and 18F-FCh and CT perfusion in a single-scan mode for hepatocellular carcinoma were evaluated for the first time. The obtained data allow to assume that the integrated use of PET with 18F-FDG and 18F-FCh and CT perfusion in a single scan improves the differential diagnostic possibilities of PET/CT diagnostics, which can find application in planning and prognosis of the disease. Due to the small number of patients further study of the problem is required.

The uptake exploration of 68Ga-labeled NGR in well-differentiated hepatocellular carcinoma xenografts: Indication for the new clinical translational of a tracer based on NGR

18F-FDG has low uptake and poor diagnostic efficiency in hepatocellular carcinoma (HCC), particularly in well-differentiated HCC. The NGR peptide selectively targets CD13, which is overexpressed in many types of tumor cells as well as neovasculature cells. In the present study, we aimed to evaluate the feasibility of utilizing 68Ga-NGR to image CD13-positive well-differentiated HCC xenografts. The in vitro cellular uptake, in vivo micro-PET/CT imaging and biodistribution studies of 68Ga-NGR and 18F-FDG were quantitatively compared in SMMC-7721-based well‑differentiated HCC xenografts. The human fibrosarcoma (HT-1080) and human colorectal adenocarcinoma (HT-29) xenografts were respectively used as positive and negative reference groups for CD13. The expression of CD13 was qualitatively verified by immunofluorescence staining and immunohistostaining studies. The expression levels of CD13 and glucose-6-phosphatase (G6Pase) were semi-quantitatively analyzed by western blotting. The in vitro SMMC-7721 cellular uptake of 68Ga‑NGR was significantly higher than that of 18F-FDG (1.23±0.11 vs. 0.515±0.14%; P<0.01). The in vivo micro-PET/CT imaging results revealed that the uptake of 68Ga-NGR in SMMC-7721-derived tumors was 2.17±0.21% ID/g (percentage of injected dose per gram of tissue), which was higher compared to that of 18F-FDG (0.73±0.26% ID/g; P<0.01); however, the tumor/liver ratio of 68Ga-NGR was 2-fold higher than that of 18F-FDG. We concluded that the uptake of 68Ga-NGR was significantly higher both in vitro and in vivo than 18F-FDG in the well‑differentiated HCC xenografts and therefore, it is promising for further clinical translation in well-differentiated HCC PET/CT diagnosis.

Evaluation of 99mTc-3PRGD2 integrin receptor imaging in hepatocellular carcinoma tumour-bearing mice: comparison with 18F-FDG metabolic imaging

Objective

Our study was designed to explore the utility of ^99mTc-HYNIC-PEG₄-E[PEG₄-c(RGDfK)]₂ (^99mTc-3PRGD₂) for the detection of hepatocellular carcinoma (HCC) and specifically to compare the diagnostic performance of ^99mTc-3PRGD₂ integrin receptor imaging and 2-18-fluoro-2-deoxy-d-glucose (¹⁸F-FDG) metabolic imaging in a nude mouse model.

Methods

^99mTc-3PRGD₂ was synthesized using a HYNIC-3PRGD₂ lyophilized kit with ^99mTcO₄ labelling. The nude mouse animal model was established by subcutaneously injecting 5 × 10⁷/ml HepG2 cells into the shoulder flank of each mouse. Biodistribution studies were performed at 0.5, 1, 2 and 4 h after intravenous administration of 0.37 MBq of ^99mTc-3PRGD₂. Immunohistochemistry was performed to evaluate the expression level of integrin αvβ3 in the HCC tissues. Dynamic imaging was performed using list-mode after the administration of 55.5 MBq of ^99mTc-3PRGD₂, to reconstruct the multiphase images and acquire the best initial scan time. At 8, 12, 16, 20 and 24 days after inoculation with HepG2 cells, 55.5 MBq of ^99mTc-3PRGD₂ and 37 MBq of ¹⁸F-FDG were injected successively into the nude mouse model, subsequently, simultaneous SPECT/PET imaging was performed to calculate the tumour volume and tumour uptake of ^99mTc-3PRGD₂ and ¹⁸F-FDG.

Results

The biodistribution study first validated that the tumour uptake of ^99mTc-3PRGD₂ at the different time points was higher than that of all the other organs tested in the experiment, except for the kidney. Integrin αvβ3 expressed highly in early stage HCC and declined for further necrosis of the tumour tissue. Subcutaneous tumours were visualized clearly with excellent contrast under ^99mTc-3PRGD₂ SPECT/CT imaging, and the multiphase imaging comparison showed the tumours were prominent at 0.5 h, suggesting that the best initial scan time is 0.5 h post-injection. The comparison of the imaging results of the two methods showed that ^99mTc-3PRGD₂ integrin receptor imaging was more sensitive than ¹⁸F-FDG metabolic imaging for the detection of early stage HCC, meanwhile the tumour uptake of ^99mTc-3PRGD₂ was consistently higher than that of ¹⁸F-FDG. However, as tumour necrosis further increased in HCC tissues, the uptake of ¹⁸F-FDG was higher than that of ^99mTc-3PRGD₂.

Conclusion

Our study demonstrated that ^99mTc-3PRGD₂ is a valuable tumour molecular probe for the detection of early stage HCC compared with ¹⁸F-FDG, meriting further investigation of ^99mTc-3PRGD₂ as a novel SPECT tracer for tumour imaging.

Fructose-1,6-Bisphosphatase 1 Reduces 18F FDG Uptake in Hepatocellular Carcinoma

Purpose To determine whether fructose 1,6-bisphosphatase 1 (FBP1) expression is associated with fluorine 18 (¹⁸F) fluorodeoxyglucose (FDG) accumulation in patients with hepatocellular carcinoma (HCC) and to investigate how FBP1 expression and ¹⁸F FDG uptake are related to tumor differentiation grade and metabolism and whether the molecular mechanism involves hypoxia-inducible factor 1-α (HIF1A) transcriptional activity. Materials and Methods This retrospective study was approved by the institutional review board with informed consent. Eighty-five patients with HCC underwent ¹⁸F FDG combined positron emission tomography and computed tomography (PET/CT). The relationship between maximum standardized uptake (SUV_max) and expression of FBP1, glucose transporter 1 (GLUT1), and hexokinase 2 (HK2) was analyzed with immunohistochemical analysis. In vitro FBP1 overexpression in HCC cells was used to examine the role of FBP1 in tumor metabolism, and its effect on HIF1A transcriptional activity was investigated with quantitative polymerase chain reaction and luciferase reporter assay. Spearman rank correlation was applied to determine the association between FBP1 expression and SUV_max. Results There was an inverse relationship between FBP1 expression and SUV_max (P = .003). SUV_max was higher in patients with poorly differentiated HCC (mean, 6.7 ± 3.6 [standard deviation]) than in those with well- (mean, 2.6 ± 0.7, P < .001) or moderately (mean, 4.1 ± 2.3, P < .001) differentiated HCC. FBP1 expression was significantly lower in patients with poorly differentiated HCC (mean, 0.6 ± 0.2) than in those with well- (mean, 1.4 ± 0.6, P = .006) or moderately (mean, 1.2 ± 0.2, P = .007) differentiated HCC. FBP1 overexpression in HCC cells led to a significant decrease in GLUT1 expression (P = .034), ¹⁸F FDG uptake (P = .023), and HIF1A transcriptional activity (P = .001). Conclusion SUV_max in patients with HCC is inversely associated with FBP1 expression, and FBP1 may inhibit ¹⁸F FDG uptake via the HIF1A pathway. SUV_max is higher in patients with poorly differentiated HCC than in those with well- or moderately differentiated HCC, which could be the result of lower FBP1 expression in the former. ^© RSNA, 2017.

Low Utility of Fluorodeoxyglucose-Positron Emission Tomography/Computed Tomography for Detecting Hepatocellular Carcinoma in Patients Before Liver Transplantation

OBJECTIVES

Our program routinely used fluorodeoxyglucose-positron emission tomography/computed tomography as part of the liver transplant evaluation of patients with hepatocellular carcinoma. The aim of this study was to evaluate the role of this imaging modality in the pretransplant work-up.

MATERIALS AND METHODS

This was a retrospective chart review of our liver transplant database from January 2011 to December 2014 for all patients with hepatocellular carcinoma who underwent a liver transplant. Collected data included age, sex, cause of liver disease, imaging modality, fluorodeoxyglucose-positron emission tomography/computed tomography results, explant tissue analysis, type of transplant, and transplant outcome.

RESULTS

During the study period, 275 liver transplants were performed. Fifty-three patients had hepatocellular carcinoma; 41 underwent fluorodeoxyglucose-positron emission tomography/computed tomography. Twenty-nine patients underwent living-donor liver transplant, and 12 patients underwent deceased-donor liver transplant. One of the 41 patients with negative FDG-imaging results had no evidence of hepatocellular carcinoma in the explant and was excluded from the study. The patients' average age was 58 years (range, 22-72 y), and 28 patients were men. The cause of liver disease was hepatitis C virus in 24 patients, cryptogenic cirrhosis in 12 patients, and hepatitis B virus in 5 patients. One patient had no hepatocellular carcinoma on explants and was excluded from the study. Twenty-five patients had hepatocellular carcinoma that met the Milan criteria, 7 were within the UCSF (University of California, San Francisco) criteria, and 8 exceeded the UCSF criteria. Of the 40 patients, 11 had positive fluorodeoxyglucose-positron emission tomography/computed tomography results (27.5%) with evidence of hepatocellular carcinoma in the explant; the remaining 29 patients (72.5%) had negative results. The fluorodeoxyglucose-positron emission tomography/computed tomography results were positive in 16% (4 of 21) of patients who met the Milan criteria, 28% (2 of 7) of patients who met the UCSF criteria and 62% (5 of 8) of patients who exceeded the UCSF criteria.

CONCLUSIONS

Fluorodeoxyglucose-positron emission tomography/computed tomography has a low degree of use in patients with hepatocellular carcinoma that falls within the Milan criteria and should not be routinely used as part of the liver transplant work-up.

Fat-Containing Hypermetabolic Masses on FDG PET/CT: A Spectrum of Benign and Malignant Conditions

OBJECTIVE

This article focuses on identifying the imaging appearances of hypermetabolic fatty masses and masslike lesions on PET/CT and understanding the diagnostic challenges radiologists may face while interpreting findings of these lesions on PET/CT. This article provides an approach to aid in the diagnosis of these lesions and the appropriate management of patients.

CONCLUSION

Both malignant and benign fat-containing masses and masslike lesions can show hypermetabolic activity on PET/CT. Although the differential diagnosis is broad, clinical history, anatomic location, and knowledge of anatomic variants and imaging features can help radiologists avoid misinterpretation of benign fatty lesions as malignancy.

Rate of Distant Metastases on 18F-FDG PET/CT at Initial Staging of Breast Cancer: Comparison of Women Younger and Older Than 40 Years

Women who have breast cancer and are younger than 40 y have a poorer outcome than older women. A higher rate of undetected metastases at the time of diagnosis in younger women has been proposed to account for this difference. Our main objective was to test this hypothesis by comparing the distant metastasis rate (DMR) on initial ¹⁸F-FDG PET/CT in a group of breast cancer patients younger than 40 y (<40 y group) with that in a group of breast cancer patients older than 40 y (≥40 y group). An assessment of associations between distant metastases and tumor characteristics was a second objective of the present study.

METHODS

A retrospective single-institution study was performed on women who had breast cancer and no prior malignancy, who were asymptomatic for metastatic lesions on initial clinical examination, and who had initial ¹⁸F-FDG PET/CT within 3 mo after pathologic breast cancer diagnosis and before initial treatment. On the basis of these criteria, data for 2 groups of women differing only in age (<40 y and ≥40 y) were extracted from the hospital information system of Curie Institute-Paris. ¹⁸F-FDG PET/CT examinations were reviewed, and the DMR was recorded for each clinical stage subgroup (stages I-III).

RESULTS

For each group (<40 y and ≥40 y), 107 patients were included, with the same number of patients in each clinical stage subgroup (12 stage I patients, 32 stage IIA patients, 30 stage IIB patients, and 33 stage III patients). The ages of the patients (mean ± SD) were 34.5 ± 4.0 y (<40 y group) and 56.0 ± 10.7 y (≥40 y group). No significant difference in DMRs was observed between the <40 y group and the ≥40 y group (DMRs, 21% and 22%, respectively; P = 1). The DMRs in patients not selected for age were 8% for stage I, 11% for stage IIA, 15% for stage IIB, and 44% for stage III.

CONCLUSION

The DMR was not significantly higher in younger breast cancer patients (<40 y) than in older breast cancer patients (≥40 y), ruling out the assumption that undetected metastases at diagnosis explain the poorer outcome of younger women. However, our results highlight the high yield of ¹⁸F-FDG PET/CT for initial breast cancer staging, even in stage II patients, whatever their age.

Hepatocyte nuclear factor 1α-inactivated hepatocellular adenomas exhibit high (18)F-fludeoxyglucose uptake associated with glucose-6-phosphate transporter inactivation

OBJECTIVE

This immunohistochemical study aimed to elucidate the molecular mechanism underlying the increased fluorine-18 fludeoxyglucose (FDG) uptake in hepatocyte nuclear factor 1α (HNF1α)-inactivated hepatocellular adenomas (H-HCAs).

METHODS

Three resected H-HCAs were studied using FDG positron emission tomography. Each maximum standardized uptake value (SUVmax) was determined. Resected samples were subjected to immunohistochemical staining for the following glucose metabolism-related proteins: glucose transporter 1 (GLUT1) and glucose transporter 2 (GLUT2), indicative of uptake and transport of glucose into cellular cytoplasm; hexokinase 2 (HK2) and hexokinase 4 (HK4), glucose phosphorylation; glucose-6-phosphate transporter 1 (G6PT1), uptake and transport of glucose-6-phosphate into endoplasmic reticulum; and glucose-6-phosphatase (G6Pase), dephosphorylation.

RESULTS

All three H-HCAs exhibited increased FDG intake, with an average SUVmax of 6.6 (range: 5.2-8.2). No sample expressed GLUT1 and HK2; all the samples exhibited equivalent GLUT2 and HK4 expression, equivalent or slightly increased G6Pase expression and significantly decreased G6PT1 expression relative to the non-neoplastic hepatocytes of background liver.

CONCLUSION

The increased FDG uptake observed in H-HCAs is associated with GLUT2 and HK4 expression and G6PT1 inactivation.

ADVANCES IN KNOWLEDGE

H-HCA exhibits a high FDG uptake owing to the inactivation of G6PT1, which is transcriptionally regulated by HNF1α.

Approach to the Solitary Liver Lesion: Imaging and When to Biopsy

The characterization and management of focal liver lesions is a commonly encountered problem in radiology. While the imaging findings will often be diagnostic, in equivocal cases the decision of how to proceed may be challenging. The primary modalities for liver lesion characterization are multiphase contrast-enhanced computed tomography and magnetic resonance imaging. Most lesions have typical imaging features, and when taken in conjunction with patient demographics and biochemistry the diagnosis can usually be made. Ancillary imaging modalities such as contrast-enhanced ultrasound and hepatobiliary specific contrast agents are also useful. Cirrhotic livers present a challenge due to the spectrum of benign, dysplastic, and malignant nodules that can occur. The report should include information necessary for accurate staging, and published standardized reporting guidelines should be taken into consideration. A decision to proceed to biopsy should be made only after multidisciplinary review of the case. If biopsy is required, fine needle aspiration is usually sufficient, though core needle biopsy may be required in certain circumstances.

An investigation of the relation between tumor-to-liver ratio (TLR) and tumor-to-blood standard uptake ratio (SUR) in oncological FDG PET

Background

The standardized uptake value (SUV) is the nearly exclusive means for quantitative evaluation of clinical [18F-]fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) whole body investigations. However, the SUV methodology has well-known shortcomings. In this context, it has been recognized that at least part of the problems can be eliminated if tumor SUV is normalized to the SUV of a reference region in the liver (tumor-to-liver [TLR] ratio). In recent publications, we have systematically investigated the tumor-to-blood SUV ratio (SUR) for normalization of tumor SUVs which in our view offers principal advantages in comparison to TLR. The aim of this study was a comprehensive comparison of TLR and SUR in terms of quantification of tumor lesions.

Methods

18F-FDG PET/CT was performed in 424 patients (557 scans) with different tumor entities prior to radio(chemo)therapy. In the PET images, SUV_max of the primary tumor was determined. SUV_liver was calculated in the inferior right lobe of the liver. SUV_blood was determined by manually delineating the aorta in the low-dose CT. TLR and SUR were computed and scan time corrected to 60 min p.i. (TLR_tc and SUR_tc). Correlation analysis was performed for SUV_liver vs. SUV_blood, TLR vs. SUR, SUV_liver/SUV_blood vs. SUV_blood,SUR_tc/TLR vs. SUR_tc, and SUR_tc/TLR_tc vs. SUR_tc. Variability of the respective ratios was assessed via histogram analysis. The prognostic value of TLR and TLR_tc for distant metastases-free survival (DM) was investigated with univariate Cox regression in a homogeneous subgroup (N = 130) and compared to previously published results for SUV and SUR_tc.

Results

Correlation analysis revealed a linear correlation of SUV_liver vs. SUV_blood (R ²=0.83) and of TLR vs. SUR_tc (R²=0.92). The SUV_liver/SUV_blood ratio (mean ± s.d.) was 1.47 ± 0.18. For the SUR_tc/TLR ratio, we obtained 1.14 ± 0.21 and for the SUR_tc/TLR_tc ratio 1.38 ± 0.17. Survival analysis revealed TLR and TLR_tc as significant prognostic factors for DM (hazard ratio [HR] = 3.3 and HR = 3, respectively). Both hazard ratios are lower than that of SUR_tc (HR = 4.1) although this reduction does not reach statistical significance for the given limited group size. HRs of TLR and SUR_tc are both significantly higher than HR of SUV (HR = 2.2).

Conclusions

Suitability of the liver as surrogate of arterial tracer supply for SUV normalization via TLR computation is limited. Further studies in sufficiently large patient groups are required to better characterize the relative performance of SUV, TLR, and SUR in different settings.

PET-avid hepatocellular adenomas: incidental findings associated with HNF1-α mutated lesions

BACKGROUND

Hepatocellular adenoma (HCA) is the second most common benign liver neoplasm and occurs predominantly in women in their reproductive years. Positron emission tomography (PET) using [18F] fluorodeoxyglucose (FDG) is commonly used in cancer staging, surveillance and evaluation of treatment response. PET-avid HCA are rare and can be falsely interpreted as malignancies.

METHODS

A retrospective review of four institutions' database was performed to identify the PET-avid HCAs with clinico-pathological correlation.

RESULTS

Nine patients with histological proven PET-avid HCA was identified. Eight out of 9 patients were female with a median age at diagnosis of 44 years. All patients' tumors with available histological subtyping (8/8) were HNF1-α mutated and had no inflammatory changes; 6 out the 9 lesions had prominent (>50%) steatotic changes.

CONCLUSION

Hepatocellular adenomas, specifically the HNF1-α subtype, can cause false-positive PET findings when seeking to identify malignancy. Concomitantly, PET-CT may have the potential to identify the HCA histopathologic variant with the lowest malignant and hemorrhagic potential.

Diagnostic and therapeutic management of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is an increasing health problem, representing the second cause of cancer-related mortality worldwide. The major risk factor for HCC is cirrhosis. In developing countries, viral hepatitis represent the major risk factor, whereas in developed countries, the epidemic of obesity, diabetes and nonalcoholic steatohepatitis contribute to the observed increase in HCC incidence. Cirrhotic patients are recommended to undergo HCC surveillance by abdominal ultrasounds at 6-mo intervals. The current diagnostic algorithms for HCC rely on typical radiological hallmarks in dynamic contrast-enhanced imaging, while the use of α-fetoprotein as an independent tool for HCC surveillance is not recommended by current guidelines due to its low sensitivity and specificity. Early diagnosis is crucial for curative treatments. Surgical resection, radiofrequency ablation and liver transplantation are considered the cornerstones of curative therapy, while for patients with more advanced HCC recommended options include sorafenib and trans-arterial chemo-embolization. A multidisciplinary team, consisting of hepatologists, surgeons, radiologists, oncologists and pathologists, is fundamental for a correct management. In this paper, we review the diagnostic and therapeutic management of HCC, with a focus on the most recent evidences and recommendations from guidelines.

PET-avid hepatocellular adenomas: incidental findings associated with HNF1-α mutated lesions

BACKGROUND

Hepatocellular adenoma (HCA) is the second most common benign liver neoplasm and occurs predominantly in women in their reproductive years. Positron-emission tomography (PET) using [18F] fluorodeoxyglucose (FDG) is commonly used in cancer staging, surveillance and evaluation of the treatment response. PET-avid HCA is rare and can be falsely interpreted as malignancies.

METHODS

A retrospective review of four institutions' database was performed to identify the PET-avid HCAs with clinico-pathological correlation.

RESULTS

Nine patients with histological proven PET-avid HCA was identified. Eight out of nine patients were female with a median age at diagnosis of 44 years. All patients' tumours with available histological subtyping (8/8) were HNF1-α mutated and had no inflammatory changes; six out the nine lesions had prominent (>50%) steatotic changes.

CONCLUSION

Hepatocellular adenomas, specifically the HNF1-α subtype, can cause false-positive PET findings when seeking to identify malignancy. Concomitantly, PET-CT may have the potential to identify the HCA histopathological variant with the lowest malignant and haemorrhagic potential.

FDG PET/CT in the liver: lesions mimicking malignancies

PURPOSE

18F-fluorodeoxyglucose (FDG) PET/CT is invaluable in managing liver lesions, in particular in the evaluation of suspected liver metastases. It is both sensitive and specific in detecting liver metastases from a wide range of primary cancers, and may change clinical management, most commonly by detecting additional lesions and decreasing the number of futile surgeries. However, some benign lesions may also show increased metabolic activity which can lead to false positive PET findings. We describe some of these lesions and their imaging characteristics that may help in differentiating them from malignant metastases.

METHODS

e reviewed all whole body FDG PET/CT studies performed over a 5-year period in our institution, and identified those with focal liver lesions showing increased FDG uptake for which histological results were available.

RESULTS

majority of lesions showing increased metabolic activity were due to malignant disease, such as metastases or primary liver tumours. However, we also found increased FDG uptake in non-neoplastic lesions such as Cryptococcosis, abscesses, and secondary inflammation from cholecystitis. Increased metabolic activity was also seen in some benign neoplasms such as hepatic adenomas and hemangioendotheliomas.

CONCLUSION

DG PET/CT is currently the most sensitive non-invasive imaging modality for the detection of hepatic metastases, particularly from the gastrointestinal tract. False positive results are rare, and have been described mainly in abscesses. However, other lesions can also show increased metabolic activity, and failure to differentiate these from metastases may result in inappropriate treatment.

The emerging role of positron emission tomography in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a leading cause of cancer mortality worldwide. HCC a heterogeneous disease occurring on the background of cirrhosis. The presence of cirrhosis limits the sensitivity of conventional imaging modalities in differentiating HCC from surrounding cirrhotic parenchyma. Positron emission tomography (PET) using ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) is widely used for assessing a variety of malignancies, however, has poor sensitivity in the evaluation of HCC. This has led to the investigation of other radiotracers such as ¹¹C-acetate and ¹¹C-choline, with improved sensitivity in terms of detection and therapeutic response. In this review, we discuss the emerging field of PET imaging for the detection, staging and assessment of treatment response in HCC. In particular we discuss the role of ¹⁸F-FDG-PET in imaging hepatocellular cancer, the limitations of this PET tracer and emerging novel PET tracers being investigated that exploit key metabolic processes including fatty acid and lipid synthesis, choline kinase activity and gene expression.

Kinetic analysis of dynamic (11)C-acetate PET/CT imaging as a potential method for differentiation of hepatocellular carcinoma and benign liver lesions

Objective: The kinetic analysis of ¹¹C-acetate PET provides more information than routine one time-point static imaging. This study aims to investigate the potential of dynamic ¹¹C-acetate hepatic PET imaging to improve the diagnosis of hepatocellular carcinoma (HCC) and benign liver lesions by using compartmental kinetic modeling and discriminant analysis.

Methods: Twenty-two patients were enrolled in this study, 6 cases were with well-differentiated HCCs, 7 with poorly-differentiated HCCs and 9 with benign pathologies. Following the CT scan, all patients underwent ¹¹C-acetate dynamic PET imaging. A three-compartment irreversible dual-input model was applied to the lesion time activity curves (TACs) to estimate the kinetic rate constants K₁-k₃, vascular fraction (VB) and the coefficient α representing the relative hepatic artery (HA) contribution to the hepatic blood supply on lesions and non-lesion liver tissue. The parameter Ki (=K₁×k₃/(k₂ + k₃)) was calculated to evaluate the local hepatic metabolic rate of acetate (LHMAct). The lesions were further classified by discriminant analysis with all the above parameters.

Results: K₁ and lesion to non-lesion standardized uptake value (SUV) ratio (T/L) were found to be the parameters best characterizing the differences among well-differentiated HCC, poorly-differentiated HCC and benign lesions in stepwise discriminant analysis. With discriminant functions consisting of these two parameters, the accuracy of lesion prediction was 87.5% for well-differentiated HCC, 50% for poorly-differentiated HCC and 66.7% for benign lesions. The classification was much better than that with SUV and T/L, where the corresponding classification accuracy of the three kinds of lesions was 57.1%, 33.3% and 44.4%.

Conclusion: ¹¹C-acetate kinetic parameter K₁ could improve the identification of HCC from benign lesions in combination with T/L in discriminant analysis. The discriminant analysis using static and kinetic parameters appears to be a very helpful method for clinical liver masses diagnosis and staging.

Rare solitary focal tuberculous involvement of liver masquerading as hepatic metastasis on FDG PET/CT in a case of fibular round cell tumor

Finding of focal 18F-fluoro-deoxyglucose (FDG) uptake in liver on FDG positron emission tomography/computed tomography (FDG PET/CT) in a known case of malignancy is often considered to be metastases. We report a similar finding on FDG PET/CT in a case of Ewing's sarcoma of thigh, which turned out to be of tuberculous etiology, an unusual cause of false positive FDG uptake in the liver.