Case report: detection of multiple sporadic gastrointestinal stromal tumors by dual-time 18 F-FDG PET/CT

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors affecting the gastrointestinal tract. Typically, GISTs are solitary; however, in rare cases, they may be multiple and appear in one or more organs. Multiple GISTs can appear in familial GISTs, children, or certain tumor syndromes such as neurofibromatosis type 1, Carney syndrome, and Carney-Stratakis syndrome. However, the diagnosis of primary multiple sporadic GISTs is often more difficult than that of these diseases. Herein, we report a case of multiple primary sporadic GISTs in a 64-year-old man, affecting the abdominal cavity and retroperitoneum, as identified through dual-time point positron emission tomography (PET) with 18F-labeled fluoro-2-deoxyglucose (18F-FDG) and computed tomography (18F-FDG PET/CT). Notably, the dual-time-point PET/CT revealed the migration of masses near the lower abdomen into the abdominal cavity. Furthermore, a significant increase in radioactive uptake of the mass 3 h after 18F-FDG injection compared with that 1 h after injection may be an important cue for its diagnosis.

Nuclear medicine imaging for bone metastases assessment: what else besides bone scintigraphy in the era of personalized medicine?

Accurate detection and reliable assessment of therapeutic responses in bone metastases are imperative for guiding treatment decisions, preserving quality of life, and ultimately enhancing overall survival. Nuclear imaging has historically played a pivotal role in this realm, offering a diverse range of radiotracers and imaging modalities. While the conventional bone scan using 99mTc marked bisphosphonates has remained widely utilized, its diagnostic performance is hindered by certain limitations. Positron emission tomography, particularly when coupled with computed tomography, provides improved spatial resolution and diagnostic performance with various pathology-specific radiotracers. This review aims to evaluate the performance of different nuclear imaging modalities in clinical practice for detecting and monitoring the therapeutic responses in bone metastases of diverse origins, addressing their limitations and implications for image interpretation.

Head-to-head comparison of 68Ga-FAPI-04 PET/CT and 18F-FDG PET/CT in the evaluation of primary digestive system cancer: a systematic review and meta-analysis

Introduction

Althoug ¹⁸F-FDG positron emission tomography/computed tomography (PET/CT) is widely accepted as a diagnostic tool for detecting digestive cancers, ⁶⁸Ga-FAPI-04 PET/CT may perform better in detecting gastrointestinal malignancies at an earlier stage. This study aimed to systematically review the diagnostic performance of ⁶⁸Ga-FAPI-04 PET/CT compared with that of ¹⁸F-FDG PET/CT in primary digestive system cancers.

Methods

In this study, a comprehensive search using the PubMed, EMBASE, and Web of Science databases was performed to identify studies that met the eligibility criteria from the beginning of the databases to March 2023. The quality of the relevant studies with the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) method was assessed using the RevMan 5.3 software. Sensitivity and specificity were calculated using bivariate random-effects models, and heterogeneity was assessed with the I² statistic and meta-regression analysis using the R 4.22 software.

Results

A total of 800 publications were identified in the initial search. Finally, 15 studies comprising 383 patients were included in the analysis. The pooled sensitivity and specificity of ⁶⁸Ga-FAPI-04 PET/CT were 0.98 (95% CI, 0.94-1.00) and 0.81 (95% CI, 0.23-1.00), whereas those of ¹⁸F-FDG PET/CT were 0.73 (95% CI, 0.60-0.84) and 0.77 (95% CI, 0.52-0.95), respectively. ⁶⁸Ga-FAPI-04 PET/CT performed better for specific tumours, particularly in gastric, liver, biliary tract, and pancreatic cancers. Both imaging modalities had essentially the same diagnostic efficacy in colorectal cancer.

Conclusions

⁶⁸Ga-FAPI-04 PET/CT showed a higher diagnostic ability than ¹⁸F-FDG PET/CT in terms of diagnosing primary digestive tract cancers, especially gastric, liver, biliary tract, and pancreatic cancers. The certainty of the evidence was high due to the moderately low risk of bias and low concern regarding applicability. However, the sample size of the included studies was small and heterogeneous. More high-quality prospective studies are needed to obtain higher-quality evidence in the future.

Systematic Review Registration

The systematic review was registered in PROSPERO [CRD42023402892].

FAPI-PET/CT in Cancer Imaging: A Potential Novel Molecule of the Century

Fibroblast activation protein (FAP), a type II transmembrane serine protease, is highly expressed in more than 90% of epithelial tumors and is closely associated with various tumor invasion, metastasis, and prognosis. Using FAP as a target, various FAP inhibitors (FAPIs) have been developed, most of which have nanomolar levels of FAP affinity and high selectivity and are used for positron emission tomography (PET) imaging of different tumors. We have conducted a systematic review of the available data; summarized the biological principles of FAPIs for PET imaging, the synthesis model, and metabolic characteristics of the radiotracer; and compared the respective values of FAPIs and the current mainstream tracer ¹⁸F-Fludeoxyglucose (¹⁸F-FDG) in the clinical management of tumor and non-tumor lesions. Available research evidence indicates that FAPIs are a molecular imaging tool complementary to ¹⁸F-FDG and are expected to be the new molecule of the century with better imaging effects than ¹⁸F-FDG in a variety of cancers, including gastrointestinal tumors, liver tumors, breast tumors, and nasopharyngeal carcinoma.

Situs Inversus Totalis on 18F-FDG PET/CT: A Case Report and a Literature Review

A 62-year-old female patient with pathologically confirmed left lung small cell neuroendocrine carcinoma. The patient was referred to our positron emission tomography (PET)/CT center to look for possible metastatic diseases. After fasting for 8 h, the fasting blood glucose level of the patient was 7.1 mmol/L. The patient was intravenously injected with a 6.42 mCi (238 MBq) ¹⁸F-fluorodeoxyglucose (FDG) imaging agent. After the patient rested for 1 h, we scanned the patient with SIEMENS Biograph mCT 64 PET/CT camera. In addition to lung tumors and lymph node diseases, abnormal tracer uptake in the patient's thyroid was also found. PET/CT also showed situs inversus totalis of the patient, including the dextrocardia, liver on the left side, stomach, and spleen on the right side of the patient's body. The identification of anatomical variations and abnormalities by PET/CT imaging is very important to develop the best treatment for lung cancer.

PET/CT findings for tumors in the base of the skull: comparison of 18 F-FDG with 11 C-methionine

BACKGROUND

Positron emission tomography/computed tomography (PET/CT) using 18 F-fluorodeoxyglucose (FDG) has been used to characterize various malignancies. There are few reports regarding the use of 11 C-methionine (MET)-PET/CT to characterize tumors in the skull base.

PURPOSE

To compare MET-PET/CT with FDG-PET/CT in cases of tumors of the skull base.

MATERIAL AND METHODS

Both MET-PET/CT and FDG-PET/CT were performed in 27 patients with tumors of the skull base. In all cases, pathology was determined by surgery or biopsy. The images were visually and independently reviewed by two reviewers. For qualitative analysis, the inter-rater agreement between two reviewers was measured. For semi-quantitative evaluation, the tumor-to-normal brain uptake ratios (T/N ratios) were calculated by dividing the maximum of standardized uptake value (SUVmax) for the tumor by the SUVmax of the normal contra-lateral cerebellar hemisphere. Difference in T/N ratios between FDG-PET/CT and MET-PET/CT was analyzed for statistical significance.

RESULTS

On qualitative evaluation, the inter-rater agreement of MET-PET/CT was superior than that of FDG-PET/CT. MET uptake was interpreted as positive in every tumor by both reviewers. MET-PET/CT had a significantly higher T/N ratio than FDG-PET/CT (2.96 ± 1.25 vs. 1.02 ± 0.54, respectively; P < 0.001).

CONCLUSION

MET-PET/CT showed superior inter-rater agreement and had higher uptake for tumors at the skull base than FDG-PET/CT. The present study suggests that MET-PET/CT has superior potential for imaging of tumors of the skull base.