Heterogeneous Uptake of 68 Ga-DOTATATE and 18 F-FDG in Initial Diagnosed Neuroendocrine Tumors Patients : Which Patients Are Suitable for Dual-Tracer PET Imaging?

PURPOSE: This study was designed to assess the uptake heterogeneity in neuroendocrine tumor (NET) patients at initial diagnosis with dual-tracer PET imaging and the staging changes and prognostic value it brings to explore the indication of the use of dual-tracer PET. METHODS: Fifty-one newly diagnosed patients with pathologically confirmed NET who underwent 18 F-FDG and 68 Ga-DOTATATE PET imaging between January 2020 and September 2022 were enrolled. Dual-tracer uptake patterns were classified into 3 groups: A. 68 Ga-DOTATATE positive and 18 F-FDG negative, B. 68 Ga-DOTATATE positive and 18 F-FDG positive, and C. 68 Ga-DOTATATE negative and 18 F-FDG positive. Descriptive statistics were used to evaluate the heterogeneity of dual-tracer uptake patterns among different grading (G) groups, between primary and metastatic lesions, and staging changes. Moreover, dual-tracer uptake patterns, grade, age, sex, and stage were compared with progression-free survival (PFS) by Cox regression. RESULTS: In the different G groups, none of the patients with dual-tracer uptake pattern A had grade 3 histology, but 57% of patients with grade 1 disease had FDG avidity (25% of them resulting in dual-tracer uptake pattern C). Patients with no metastasis were well differentiated, but one of them presented with dual-tracer uptake pattern C. Different uptake patterns were also observed between primary and metastatic lesions, particularly 44% of patients with dual-tracer uptake pattern A of primary with FDG avidity of metastases. Moreover, 9 (17.6%) had new lesions detected by additional 18 F-FDG PET imaging, and 3 of them (5.9%) had clinical stage changed accordingly. The Cox regression test showed that the dual-tracer uptake patterns were significantly correlated with PFS by univariate and multivariate analyses ( P = 0.026 and 0.039, respectively), whereas the grade and stage did not correlate with survival (all P >0.05). CONCLUSION: The current study has proven the uptake heterogeneity of the NET at initial diagnosis and demonstrated the staging and prognostic value of dual-tracer PET imaging. Our preliminary results have confirmed the importance of dual-tracer imaging modalities and concluded that dual-tracer PET imaging could be considered as prognostic tool for all patients with an initial diagnosis of NET.

[The Application Value of True Whole-body PET/CT Scanning Protocol in Patients of Extranodal NK/T Cell Lymphoma].

OBJECTIVE: To assess the staging, restaging, and treatment strategy determination of extranodal NK/T cell lymphoma (ENKT) by PET/CT real body (true whole-body, TWB) imaging, which is superior to PET/CT limitation of the whole body (limited whole-body, LWB, from skull vertex to upper thighs) by adding 'distal lower extremity' images. METHODS: TWB 18F-FDG PET/CT studies performed for staging and follow-up of ENKTL patients between January 2012 and September 2017 were retrospectively reviewed. Patients in staging group received TWB PET/CT evaluation for staging at the first diagnosis. In follow-up group, patients received follow-up evalution with TWB PET/CT and progressive disease (PD) in the LWB range with or without clinical diagnosis or suspicion before follow-up examination, and then divided into four subgroups: staging (+) PD (－), staging (+) PD (+), staging (－) PD (－), staging (－) PD (+). Then the percentage of unexpected ENKTL lesions found at the distal extremity (outside the LWB range) (P1), and the percentage of changes in the staging, restaging/outcome evaluation (P2) in each group were recorded. RESULTS: Among the 225 patients in the staging group, 200 (88.9%) had tumors confined to LWB, while P1 was 11.1% (25 cases) and P2 was 0.4% (1 case). In the follow-up group, the P1 in staging (+) PD (－)( n=85), staging (+) PD (+)( n=4), staging (－) PD (－)( n=43), staging (－) PD (+) goups ( n=15) were 1.2%, 75.0%, 0%, 26.7%, and P2 were 1.2%, 0%, 0%, 13.3%, respectively. In the follow-up group, regardless of whether the TWB PET/CT examination was performed at the initial diagnosis stage, P1 in PD (－) group and PD (+) group was 0.8 vs. 36.8% ( P<0.000 1), and P2 was 0.8% vs. 10.5% ( P<0.000 1). CONCLUSION: It is not recommended that the TWB PET/CT imaging from the top of the head to the bottom of the foot use for the first diagnosis of ENKTL patients. And for follow-up patients with no clinical evidence of tumor progression or with evidence of tumor progression but whose lesions were limited to LWB at the initial diagnosis of TWB PET/CT staging, LWB PET/CT from the top of the head to the middle of the thigh is recommended for routine follow-up. For ENKTL patients, TWB PET/CT was not performed at the initial stage of diagnosis to detect the condition of lower limbs. If the evidence of tumor progression in the LWB range appeared before the follow-up examination, TWB PET/CT was recommended for the follow-up evaluation to evaluate the systemic tumor involvement.

Double contrast-enhanced ultrasonography of a small intestinal neuroendocrine tumor: a case report of a recommendable imaging modality.

A 57-year-old male presenting with spontaneously relieved abdominal cramp and distension was admitted to the West China Hospital. The diagnosis remained unclear after colonoscopy and computed tomography. Double contrast-enhanced ultrasonography was then performed and a neoplasm in the small intestine was suspected, supported by a thin-section computed tomography and positron emission tomography/computed tomography. This was confirmed pathologically after surgery to be a small intestinal G1 neuroendocrine tumor. Surgery was performed to remove approximately 25 cm of small bowel and a 3-cm solid mass located in the mesentery. The patient had a complete recovery and was tumor-free at the final follow-up. Small intestinal tumors including neuroendocrine tumors have always posed a diagnostic challenge. This case indicated that double contrast-enhanced ultrasonography is feasible in detection of small intestinal neuroendocrine tumors, and it may be an advisable approach assisting diagnosis of small intestinal tumors.

Gastric 99mTc-Methylene Diphosphonate Accumulation in a Patient With Primary Upper Gastrointestinal Tract Melanoma.

Unexpected extraosseous uptake is common on Tc-methylene diphosphonate bone scintigraphy, but accumulation by primary upper gastrointestinal tract malignant melanoma is rarely reported. The present case is a 58-year-old woman with a 10-day history of diffuse bone pain and weakness. Her bone scintigraphy showed unexpected diffuse gastric tracer uptake. Subsequent gastroscopy revealed a number of hyperpigmented lesions in the stomach and duodenal bulb. Malignant melanoma was confirmed by histopathology and immunohistochemistry. Because extensive physical examination failed to identify any other site of ocular and cutaneous melanoma, a diagnosis of primary upper gastrointestinal tract malignant melanoma was established.

[Development of a predicting model to estimate the probability of malignancy of solitary pulmonary nodules].

OBJECTIVE: To evaluate the role of (18)F-FDG PET/CT in characterizating solitary pulmonary nodule (SPN) and bone lesions. METHODS: 105 patients with a SPN smaller than 30 mm in axial diameter were recruited for this study. PET/CT images were obtained 60 min after intravenous injection of (18)F-FDG. Logistic regression analysis was performed to identify clinical predictors of SPN malignancy including age, sex, smoking history, malignant history, family history, symptoms, size, location, CT appearances, (18)F-FDG uptake, and to develop a clinical prediction model to estimate the probability of malignancy in the patients with SPN. The model fit was evaluated and the area under curve (AUC) of receiver operating characteristic (ROC) was used to evaluate the power of the model. RESULTS: The logistic regression analysis indicated that male, a positive smoking history, older age, larger nodule diameter, nodule with specula and nodule with high (18)F-FDG uptake were more likely to have malignant SPN. The clinical prediction model is described by the following equation: Logit(P) = -8.722 + 2.448 (gender) + 2.023(smoking) + 0. 851(age) + 1.057 (diameter) + 2.432 (spiculation) + 1.502 (FDG uptake). The AUC of the model was 0.892 (95% confidence interval 0.817 - 0.941). The prediction model had high accuracy in predicting malignant SPN, with 90.2%, 84.1 % and 87.6% sensitivity, specificity and accuracy respectively when the cut off value was set at 0.67. CONCLUSION: The prediction model is valid in predicting the probability of malignant SPN.

Recognition of fibrous dysplasia of bone mimicking skeletal metastasis on 18F-FDG PET/CT imaging.

PURPOSE: Fibrous dysplasia of bone (FDB) reveals intense 18F-FDG uptake mimicking metastases on 18F-FDG PET/CT. We reviewed sites of FDB revealed by 18F-FDG PET/CT imaging to allow identification of this abnormality. MATERIALS AND METHODS: Eleven patients (7 male, 4 female, aged 16-78 years) were evaluated after 55 MBq (0.15 mCi)/kg 18F-FDG utilizing a 16-slice multiple detector CT (MDCT) whole-body PET scanner, with LOR algorithm 3D reconstruction. One- and 2-h imaging was performed in 9 patients. Standard uptake value (SUV) for each lesion, on early and delayed imaging, was calculated. Lesions were confirmed in 6 patients by biopsy. The PET images correlated with MDCT to establish the imaging characteristics. RESULTS: Solitary lesions were found in 4 patients, two lesions in 1 patient, and in 6 patients there were multiple bone lesions. The SUV(early) ranged from 1.23 to 9.64 with an average of 3.76 ± 2.40. The SUV(delayed) ranged from 1.76 to 11.42 with an average of 4.51 ± 3.07. The SUV(delayed) decreased or increased slightly (-31% to 5%) in 6 of our patients, and increased significantly (11% to 39%) in 3. There was a negative correlation between SUVs and age, as well as the number of affected bones. CONCLUSIONS: In our study, FDB had wide skeletal distribution with variability of 18F-FDG uptake and CT appearance. SUV in the delayed stage was seen to either decrease or increase on dual-time 18F-FDG PET scanning. It is very important to recognize the characteristics of this skeletal dysplasia to allow differentiation from skeletal metastasis.

[Differentiation of malignant and benign superficial lymph nodes by dual time point 18F-FDG PET].

OBJECTIVE: To evaluate the value of dual time point 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) in differentiating malignant and benign superficial lymph nodes. METHODS: Sixty-eight patients with ninety superficial lymph nodes were examined. Whole body 18F-FDG PET imaging was performed one hour (early) after FDG injection and repeated one hour (delayed) later but only for the interesting areas. The maximum standardized uptake value (SUVmax) was determined for each of the node on both early and delayed images (SUV early and SUV delayed, respectively). Retention index (RI) was then calculated. The cutoff values of SUV early, SUV delayed and RI were determined by receiver operating characteristic (ROC) analyses. The efficacy of each parameter was also analyzed by ROC analyses. RESULTS: The histopathology examinations confirmed 51 malignant nodes and 39 benign nodes. The SUV early (x +/- s) for benign nodes and malignant nodes were 3.26 +/- 1.62 and 8.04 +/- 5.56, respectively (P=0.000). The SUV delayed for benign nodes and malignant nodes were 3.93 +/- 2.11 and 9.82 +/- 6.29, respectively (P=0.000). The RI for benign nodes and malignant nodes were 19.1 +/- 22.5 and 24.8 +/- 18.8, respectively (P=0.191). The cutoff values of SUV early, SUV delayed and RI were 4.3, 4.8 and 18, respectively. The cutoff values of SUV early, SUV delayed and RI produced a sensitivity of 71%, 78% and 63%, a specificity of 87%, 85% and 46%, and an accuracy of 78%, 80% and 57%, respectively. The ROC analyses illustrated that the diagnostic efficacy of SUV early, SUV delayed was higher than RI (P<0.001). However, there was no difference in diagnostic efficacy between SUV early, and SUV delayed (P=0.409). CONCLUSION: Dual-time point 18F-FDG PET does differentiate benign and malignant superficial lymph nodes effectively.

[SPECT/CT fusion imaging for the diagnosis of benign and malignant lesions in bones].

OBJECTIVE: The aim of the study was to evaluate the value of the single photon emission computed tomography/computed tomography (SPECT/CT) fusion imaging in the diagnosis of benign and malignant lesions in bones. METHODS: One hundred and forty one bone lesions of 125 cancer patients, for whom the natures of the lesions were not able to be determined by the 99Tc(m)-MDP whole-body bone scan, were examined by the SPECT, CT and SPECT/CT fusion imaging simultaneously. All of the images were blindly interpreted independently by two experienced nuclear medicine physicians. The natures of the lesions were eventually confirmed by MRI, pathology or follow-up diagnosis six months later. RESULTS: The diagnostic sensitivity of SPECT, SPECT+CT and SPECT/CT for the 141 bone lesions was 82.5%, 93.7%, and 98.4% respectively. The specificity was 66.7%, 80.8%, and 93.6% respectively. The accuracy was 73.8%, 86.5%, and 95.7% respectively. The specificity and accuracy of SPECT/CT for diagnosing bone lesions were significantly higher than those of SPECT and SPECT+CT (P<0.05). CONCLUSION: SPECT/CT can effectively differentiate benign and malignant bone lesions.