FDG Uptake Research Articles

68Ga-PSMA PET/CT and 18F-FDG PET/CT in the diagnosis of prostatic ductal cancer

PurposesTo explore the characteristics of PSMA PET/CT and FDG PET/CT images in prostatic ductal adenocarcinoma (DA) patients. MethodsWe retrospectively enrolled prostatic DA patients with PET/CT scans at Tongji Hospital from 2018 to 2022. Patients with prostatic acinar adenocarcinoma (AA) and benign pathology (BP) were enrolled by 1:1 matching. Differences in the uptake of primary and metastatic foci on PET among the groups were analyzed. ResultsA total of 42 patients were enrolled: 14 in each group. In primary foci, the mean PSMA uptake in the DA group was lower than that in the AA group (14.2 ± 9.6 vs. 27.1 ± 14.3, P = 0.009) and greater than that in the BP group (14.2 ± 9.6 vs. 4.7 ± 1.3, P = 0.003). The AUCs of the DA-AA ROC curve and DA-BP ROC curve were 0.781 and 0.872, respectively. The median PSMA uptake of metastatic lymph nodes in the DA group was lower than that in the AA group (5.6 vs. 14.2, P = 0.033), with no significant difference in metastatic bone lesions (9.5 vs 19.1, P = 0.485). No significant difference was found in the FDG uptake of primary and metastatic foci between the DA and AA groups (P > 0.05). ConclusionProstatic DA has greater PSMA uptake than BP diseases, but lower uptake in both primary foci and metastatic lymph nodes than AA on PSMA PET/CT, aiding in the differential diagnosis of DA, AA and BP diseases. Clinicians should combine traditional imaging with PSMA PET/CT to avoid underestimating the clinical stage of DA patients.

Papillary Tumor of the Pineal Gland With Discordant FDG and FAPi Uptake

Abstract In recent years, 68Ga-FAP inhibitor has emerged as a possible substitute radiotracer to FDG for imaging of most of the tumors. Here, we report a 7-year-old girl diagnosed with recurrent papillary tumor of the pineal gland, presenting with complaints of headache and vomiting. 18F-FDG PET/CT revealed an FDG-avid enhancing lesion in the posterior part of the third ventricle. Negligible FAPI uptake was noted on the corresponding 68Ga-FAPI-46 PET/CT images, highlighting the scope of 18F-FDG PET/CT in this realm.

Abstract 4138237: Clinical Utility of T2 Mapping for the Assessment of Myocardial Inflammation in Patients With Cardiac Sarcoidosis

Introduction: 18 F-FDG PET has been used for the evaluation of active inflammatory lesions in cardiac sarcoidosis (CS), but it is burdensome for patients to perform as a routine follow-up. Late gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR) that can detect myocardial fibrosis is limited in its ability to assess active inflammation. T2 mapping has been shown to detect myocardial inflammation in myocardial diseases without radiation exposure and contrast agents (Figure). However, the ability of T2 mapping for discriminating inflammatory myocardium has not been fully clarified in patients with CS. Hypothesis: We assessed the hypothesis that T2 mapping has potential for the discrimination of inflammatory myocardium in patients with CS. Methods: Twenty-seven subjects who underwent CMR at 3T and 18 F-FDG PET to diagnose CS were enrolled. Fourteen subjects were diagnosed as CS due to LGE and myocardial FDG uptake on 18 F-FDG PET (PET-positive group). Thirteen subjects showed no myocardial FDG uptake (PET-negative group). NativeT1, T2, and extracellular volume fraction (ECV) were measured using a 16-segment model. Receiver-operating characteristic (ROC) curve analysis was performed to evaluate T1 and T2 mapping in discriminating between active and inactive inflammatory segments in the PET-positive group. Results: Mean native T1, native T2 and ECV showed no significant differences between the PET-positive and the PET-negative groups. However, maximum T2 values, which were highest ones in the 16 segments, were significantly higher in the PET-positive group than the PET-negative group (51.3 ± 7.7 ms vs 45.7 ± 3.6 ms, p = 0.014). In the PET-positive group, ROC analysis showed AUC of 0.72 in native T2, 0.61 in native T1, and 0.68 in ECV for discriminating inflammatory myocardium. The optimal cutoff value of native T2 was 45.7 ms, and the diagnostic performance had a sensitivity of 44.4 %, specificity of 93.3 % , positive predictive value of 88.1 %, and negative predictive value of 60.1 %. Conclusion: T2 mapping is a promising approach for the discrimination of inflammatory myocardium without radiation exposure and contrast agents in patients with cardiac sarcoidosis.

Optimisation of Animal Handing and Timing of 2-deoxy-2-[18F]fluoro-D-glucose PET Tumour Imaging in Mice.

In humans, 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) tumour-to-background contrast continues to increase long after a typical uptake period of 45 - 60min. Similar studies have not been performed in mice and the static imaging time point for most studies is arbitrarily set at 30 - 60min post-injection of [18F]FDG. Ideally, static PET imaging should be performed after the initial period of rapid uptake but this period has not been defined in mice, with previous dynamic studies in mice being limited to 60min. This study aimed to define the kinetics of [18F]FDG biodistribution over periods of 3 - 4h in different murine tumour models, both subcutaneous and autochthonous, and to further refine fasting and warming protocols used prior to imaging. Dynamic [18F]FDG PET-CT scans lasting 3 or 4h were performed with C57BL/6J and Balb/c nude mice bearing subcutaneous EL4 murine T-cell lymphoma and Colo205 human colorectal tumours, respectively, and with transgenic Eμ-Myc lymphoma mice. Prior to [18F]FDG injection, four combinations of different animal handling conditions were used: warming for 1h at 31°C; maintenance at room temperature (20 - 24°C), fasting for 6 - 10h and a fed state. Tumour mean standardised uptake value (SUVmean) peaked at 147 ± 48min post injection in subcutaneous tumours and 74 ± 31min in autochthonous Eμ-Myc lymphomas. The tumour-to-blood ratio (TBR) peaked at 171 ± 57 and 83 ± 33min in subcutaneous and autochthonous Eμ-Myc tumours, respectively. Fasting increased tumour [18F]FDG uptake and suppressed myocardial uptake in EL4 tumour-bearing mice. There was a good correlation between tumour SUVmean and Ki calculated using an input function (IDIF) derived from the inferior vena cava. Delayed static [18F]FDG-PET imaging (> 60min) in both autochthonous and subcutaneous tumours in improved tumour-to-background contrast and increased reproducibility.

AVE0991 ameliorates dopaminergic neuronal damage in Parkinson’s disease through HOTAIRM1/miR-223-3p/α-synuclein axis

Parkinson’s disease (PD) is a prevalent type of neurodegenerative disorder. AVE0991, a non-peptide analogue of Ang-(1–7), by which the progression of PD has been discovered to be ameliorated, but the specific mechanism whereby AVE0991 modulates the progression of PD re-mains unclear. The mice overexpressing human α-syn (A53T) were established to simulate PD pathology, and we also constructed an in vitro model of mouse dopaminergic neurons overexpressing hα-syn (A53T). The [18F] FDG-PET/CT method was employed to assess FDG uptake in human α-syn (A53T) overexpressing mice. Levels of lnc HOTAIRM1 and miR-223-3p were detected via qRT-PCR. Flow cytometry was deployed to assay cell apoptosis. Here, we found that AVE0991 improved behaviour disorders and decreased α-syn expression in the substantia nigra of mice with Parkinson’s disease. AVE0991 inhibited the apoptosis of dopaminergic neurons overexpressing hα-syn (A53T) via lncRNA HOTAIRM1. MiR-223-3p binds to HOTAIRM1 as a ceRNA and directly targets α-syn. Moreover, miR-223-3p level in peripheral blood was found negatively correlated with the α-syn. Our present study shows that the angiotensin-(1–7) analogue AVE0991 targeted at the HOTAIRM1/miR-223-3p axis to degrade α-synuclein in PD mice, and showed neuroprotection in vitro.

Predicting Malignancy in Adnexal Tumors With FAPI PET/CT and FDG PET/CT: A Case Report on a Borderline Ovarian Tumor.

A 54-year-old woman presented with a 55 × 64-mm tumor in the ovary with high [18F]FDG uptake on [18F]FDG PET/CT highly suggestive of ovarian cancer. Prior to surgery, the patient underwent [68Ga]-Ga- fibroblast activation protein inhibitor (FAPI)-46 PET/CT, which revealed low [68Ga]-Ga-FAPI-46 tumor uptake. Histopathology revealed a borderline ovarian tumor, which has low malignant potential and a 10-year survival rate greater than 93%. High [18F]FDG uptake is considered a fair predictor of malignancy in adnexal tumors. The present case demonstrates the potential superiority of [68Ga]-Ga-FAPI-46 PET/CT over [18F]-FDG PET/CT in differentiating malignant adnexal tumors from borderline ovarian tumors.

"Mini Brain" Appearance in Spinal Metastasis From Type A Thymoma Detected by 18F-FDG PET/CT.

A 66-year-old man presented with persistent dull pain in the lower back for over 7 months. An expansile lytic lesion in the L4 vertebral body showed a characteristic "mini brain" appearance on MRI, which is highly suggestive of plasmacytoma. 18F-FDG PET/CT scan revealed increased FDG uptake in the L4 lesion, with an additional finding of a mass in the anterior mediastinum that showed mild FDG uptake. Lumbar surgery and complete resection of the anterior mediastinum tumor confirmed spinal metastatic type A thymoma, which was classified as p-T1aN0M1b, stage IVb. The patient's condition improved postsurgery and chemotherapy, with long-term follow-up necessary due to recurrence risk.

Integrating molecular imaging and transcriptomic profiling in advanced HER2-positive breast cancer receiving trastuzumab emtansine (T-DM1): an analysis of the ZEPHIR clinical trial.

The ZEPHIR clinical trial evaluated the role of [89Zr]trastuzumab-PET/CT (HER2-PET/CT) and 2-[18F]fluoro-2-deoxy-D-glucose PET/CT ([18F]FDG-PET/CT) in predicting outcomes in patients with advanced HER2-positive breast cancer treated with trastuzumab emtansine (T-DM1). Here, we combined molecular/metabolic imaging and transcriptomic data to investigate the biological processes associated with [89Zr]trastuzumab and [18F]FDG uptake, and to dissect the mechanisms involved in T-DM1 resistance. RNA was extracted from metastasis biopsies obtained in the ZEPHIR trial. HER2-PET/CT and [18F]FDG-PET/CT imaging data of biopsied lesions were integrated with transcriptomic data. Lesions were compared based on the level of [89Zr]trastuzumab uptake as well as on the presence/absence of metabolic response, defined comparing baseline and on-treatment [18F]FDG-PET/CT. We analyzed matched transcriptomic and molecular/metabolic imaging data for 24 metastases. Genes and pathways involved in extracellular matrix (ECM) organization and glycosylphosphatidylinositol synthesis were enriched in lesions presenting low [89Zr]trastuzumab uptake. [18F]FDG uptake at baseline correlated with proliferation and immune-related processes. Hypoxia and ECM-related processes were enriched in lesions showing no metabolic response to T-DM1, while immune-related processes were associated with high [89Zr]trastuzumab uptake and metabolic response. Gene signatures including differentially expressed genes according to [89Zr]trastuzumab uptake and metabolic response showed predictive value in an external cohort. To our knowledge, this study represents the first correlative analysis between [89Zr]trastuzumab tumor uptake and gene expression profiling in humans. Our findings suggest a role of ECM in impairing [89Zr]trastuzumab tumor uptake and T-DM1 metabolic response in advanced HER2-positive breast cancer, highlighting the potential of molecular imaging to depict tumor microenvironment features.

A Rare Case of Signet Ring Cell Lymphoma and Review of the Literature

Signet ring cell lymphoma (SRCL) is a non-Hodgkin's lymphoma with a very rare variant. Although this morphology is frequently seen in follicular lymphoma, it can also be observed in the group of diffuse large B-cell lymphomas. A seventy-six year old woman with known diagnosis of gastric adenocarcinoma, tubular type, moderately differentiate presented with a mesenteric lymphadenopathy with high FDG uptake (SUVmax: 21.3) in PET/CT during follow-up. A tru-cut biopsy was performed for histopathological diagnosis. Diffuse infiltrative singet ring neoplastic cells showed negativity for PanCK, CK7, CK20, S100, SMA, calretinin and vimentin. The panel was then expanded to include SRCL, a rare variant of lymphoma. Additional immunohistochemical evaluation revealed positivity for CD20, CD19, PAX-5 and Bcl-2. Ki-67 proliferation index was about 80%. CD3, CD30, Myc, Bcl-6, ALK, Cyclin-D1, CD23, CD10, CD21, and MUM-1 were negative. EBER was also negative by chromogen in situ hybridization (CISH). Based on these data, diffuse large B-cell lymphoma (DLBCL) was considered. We herein reported a case of signet ring cell lymphoma discussed its clinical and morphological features with regard to the literature.

After 30 Years of Remission, Recurrence With Renal Cell Carcinoma Metastasis Mimicking Pancreatic Neuroendocrine Tumor on 18F-FDG and 68Ga-DOTATATE PET/CT.

A 75-year-old man with a previous history of left nephrectomy for clear cell renal cell carcinoma in remission was underwent 68Ga-DOTATATE PET/CT imaging for evaluation of pancreatic body lesion. It showed a mass with intense 68Ga-DOTATATE uptake in the pancreatic corpus. During the follow-up of the patient who did not want to undergo surgery, 18F-FDG PET/CT scan was performed due to the increase in the size of the mass, and mild FDG uptake was detected in the pancreatic corpus lesion, and histopathological examination was confirmed as renal cell carcinoma metastasis.

Predictive value of cardiac 18F-fluorodeoxyglucose positron emission tomography for fatal ventricular arrhythmic events in patients with cardiac sarcoidosis

Abstract Background Patients with cardiac sarcoidosis (CS) face an elevated risk of fatal ventricular arrhythmic events (FVAE), including sudden cardiac death. Late gadolinium enhancement (LGE) from contrast-enhanced cardiac magnetic resonance is used for diagnosis of CS and estimation of FVAE risk. However, its application is limited in cases with cardiac devices, renal failure or contrast agent allergies. 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) emerges as a diagnostic tool for CS, even in cases where LGE is not feasible. Purpose This study aimed to investigate the potential utility of FDG-PET in predicting FVAE in patients with CS by hypothesizing that higher or lower percent FDG uptake could predict the FVAE risk. Methods Cardiac FDG-PET data from 121 patients with CS, acquired at our university hospital between March 2008 and November 2020, were analyzed. A polar-map model was used to calculate percent uptake relative to maximal cardiac FDG uptake in each of the American Heart Association (AHA) 17 segments (Figure A). Percent uptakes of the AHA 17 segments were compared between groups with and without future FVAE. LGE information was available in 82 patients and was used to assess the presence of LGE in regions where percent FDG uptake differed between the two groups. Results Among enrolled patients (mean age 59.5 ± 10.0 years, 67.8% women), 43 experienced FVAE following FDG-PET image acquisition. The group with future FVAE had a higher history of FVAE (7.7% vs. 37.2%) and beta-blocker administration (38.5% vs. 60.5%), larger left ventricular diastolic diameter (LVDd) (49.3 ± 7.3 mm vs. 57.4 ± 9.5 mm) and lower ejection fraction (LVEF) (56.6 ± 13.6% vs. 42.0 ± 15.2%) compared to the group without it (P < 0.05 all). Percent FDG uptake in the basal interventricular septum part (segment 3) (Figure A) was lower in patients with future FVAE compared to those without it (54.4 ± 13.8% vs. 41.8 ± 15.2%, P < 0.001 corrected for multiple comparisons). Kaplan-Meier analysis with a median split of percent FDG uptake in segment 3 showed that patients with lower uptake (<49%, N= 62) had lower FVAE-free survival compared to those with higher uptake (≥49%, N = 59) (P = 0.007) (Figure B). A Cox hazard model also demonstrated an association between percent FDG uptake in segment 3 and FVAE onset (hazard ratio 0.972 [95% CI 0.951, 0.995], P = 0.015) after adjusting for previous FVAE, beta-blocker administration, LVDd and LVEF. Similarly, analysis within the subgroup with LGE in the septum (N = 58) revealed a higher risk of FVAE in the group with lower percent FDG uptake compared to those with higher uptake (P = 0.020) (Figure C(a)). However, this association was not evident in patients without LGE in the septum (N = 24) (P = 0.821) (Figure C(b)). Conclusions Reduced percent FDG uptake with LGE in the basal intraventricular septum may serve as a valuable predictor of future FVAE occurrence in patients with CS.

Heparin does not improve myocardial glucose metabolism suppression in patients with low betahydroxybutyrate level

Abstract Background/introduction Inadequate myocardial glucose metabolism suppression (GMS) can hamper diagnostic PET/CT imaging with [18F]FDG. β-hydroxybutyrate level (BHB) measurement prior to [18F]FDG injection is a newly proposed method of pre-evaluation of adequate GMS. However, more knowledge is needed, if BHB can be used to guide the preparation protocol (diet, fasting or premedication). Purpose The aim of our study was to evaluate if point-of-care measured BHB can be used to guide use of heparin premedication for cardiac [18F]FDG-PET/CT. Methods 139 patients [78 male, median age 58 (19-78) years] with clinical indication for cardiac [18F]FDG PET/CT were recruited. All patients had followed a high fat, low carbohydrate diet for one day and fasted for at least twelve hours. For the first 64 patients, BHB was measured, but it was not used to guide premedication. For the next 75 patients, iv. heparin 50 IU/kg was injected 15-20 minutes before FDG injection, if BHB was low (less than 0.35 mmol/l), whereas those with high BHB (more than 0.35 mmol/l) continued without heparin. [18F]FDG uptake pattern was evaluated visually using grades "no uptake", "focal uptake", "isolated lateral wall uptake", "basal ring", "diffuse uptake" and "focal on diffuse". "No uptake" and "focal uptake" were considered as adequate GMS. Statistical significance of the difference in uptake patterns was evaluated using the Pearson’s chi-square test. Results Median BHB was 0.4 (0.1-5.8) mmol/l. Half of the patients (76, 55 %) reached BHB higher than 0.35 mmol/l. Still, 102 patients (74 %) had adequate GMS. In high BHB group, 65 patients (86 %) had adequate GMS, whereas of those with low BHB, only 37 patients (59 %) had adequate GMS (p<0.001). In low BHB group prevalence of inadequate GMS was comparable in patients with and without heparin (42 % vs. 41 %, p=0.941) Results for the whole scale of visual distribution patterns can be seen in figure 1. Conclusion(s) Patients with high BHB have a high percentage of adequate GMS, whereas in patients with low BHB the probability of adequate GMS is significantly lower. Unfractionated heparin does not seem to improve myocardial GMS in patients with low BHB. Thus, high BHB should be pursued, and a longer diet might be needed for those with low initial BHB.

18F-FDG PET/CT in the diagnosis of infective endocarditis

Abstract Background Increased uptake of 18F-fluorodeoxyglucose (FDG) by positron-emission tomography/computed tomography (PET/CT) is one of the diagnostic criteria for prosthetic valve endocarditis (PVE). However, there is limited data on the diagnostic value of FDG PET/CT in diagnosing native valve endocarditis (NVE) and semi-quantitative parameters of FDG uptake. Purpose The objective of this retrospective study was to evaluate the accuracy of FDG PET/CT and additional value of semi-quantitative measures of FDG uptake in the detection of NVE and PVE. Methods All patients who had undergone FDG PET/CT due to suspected infective endocarditis (IE) at a single tertiary referral center between 2010 and 2020 were identified. Additional patients who underwent FDG PET/CT for detecting an infection focus were included as controls. Clinical reports were evaluated and images were analyzed for maximal standardized uptake value (SUVmax) and target to background ratio (TBR = SUVmax normalized to mean blood pool SUV) around valves. The scan was defined positive based on either clinical reading or previously proposed cut-off values for SUVmax and TBR (>4.2 and >2.1, respectively). The final diagnosis of IE was defined based on all available information in electronic medical records. Results The study cohort included 16 patients with suspected NVE (median age 58 years, 88% male), 24 patients with suspected PVE (median age 72 years, 92% male) and 37 patients who underwent FDG PET/CT for detecting an infectious focus (8 with a prosthetic valve). The final diagnosis was definite IE in 25 (14 PVE), possible IE in 7 (6 PVE), and no IE in 45 (12 with a prosthetic valve). Overall, clinical reading of FDG PET/CT identified 17 (sensitivity 68%) of definite IE with a specificity of 91% and accuracy of 83%. Compared with NVE, the sensitivity of FDG PET/CT was higher in the detection of PVE (46% vs. 86%) whereas specificity was lower (97% vs. 75%) resulting in small difference in accuracy (84% vs. 81%). In PVE, SUVmax had higher sensitivity (93%) than clinical reading, resulting in the same accuracy (81%) despite lower specificity (67%). A combination of either positive clinical reading or positive SUVmax identified all patients with PVE (sensitivity 100%). In NVE, TBR had higher sensitivity (64%) than clinical reading, but accuracy (66%) and specificity (67%) were significantly lower. Conclusions FDG PET/CT shows high sensitivity in the detection of PVE and high specificity in the detection of NVE in a real-world clinical cohort. Semi-quantitative parameters of FDG uptake can improve sensitivity of detecting PVE maintaining diagnostic accuracy. However, in NVE semi-quantitative parameters were associated with a prominent reduction in specificity.

Atypical presentation of PJP: hypercalcemia and kidney injury in an allogeneic stem cell transplant recipient

BackgroundPneumocystis jirovecii pneumonia (PJP) is an opportunistic infection that primarily affects immunocompromised individuals. Typical symptoms of PJP include the subacute onset of dyspnea, nonproductive cough, and low-grade fever. In hematology patients, particularly those who are allogeneic stem cell transplant recipients, the disease often presents with a more aggressive clinical course. While hypercalcemia has been documented as a manifestation of PJP in some solid organ transplant recipients, it has not been reported in hematology or stem cell transplant patients.Case presentationHere, we present a case of PJP in a 56-year-old male allogeneic stem cell transplant recipient, who developed hypercalcemia and renal failure during the late post-transplant period. The patient had a history of allogeneic stem cell transplantation due to acute myeloid leukemia. He presented with symptoms of fatigue and weakness. Laboratory tests revealed hypercalcemia (13.8 mg/dL) and elevated serum creatinine levels (2.3 mg/dL). The patient was hospitalized, and despite initial treatment with hydration and furosemide, the hypercalcemia persisted, leading to the administration of denosumab. During follow-up, hypoxia was detected, and a chest CT scan revealed mosaic attenuation and ground-glass opacities. Bronchoscopy was performed, and PCR testing confirmed the presence of Pneumocystis jirovecii. Other causes of hypercalcemia were ruled out, with PTH measured at 13.8 pg/mL (normal range 15–65 pg/mL), albumin at 3.71 g/dL, 1.25-dihydroxy vitamin D3 at 96 ng/dL (normal range 26–95 ng/dL), and 25-hydroxy vitamin D at 32.5 ng/mL (normal range 20–40 ng/mL). A PET-CT scan demonstrated no pathological FDG uptake, with the exception of findings suggestive of a pulmonary infection. Following treatment with trimethoprim-sulfamethoxazole and denosumab, the patient’s hypercalcemia and infection resolved.Conclusions Although rare, PJP can present with hypercalcemia and kidney injury in allogeneic stem cell transplant recipients. Early diagnosis and treatment can improve both PJP and hypercalcemia.

Hepatic Recurrence of Neuroendocrine Tumor Component in Gallbladder Cancer.

A 60-year-old man underwent an extended cholecystectomy with regional lymphadenectomy for T2N0M0 gallbladder cancer (GBC), which showed significant FDG uptake (SUVmax = 6.5). However, CT scan at 24 months postsurgery revealed multiple hepatic masses. Unlike the primary GBC, the hepatic masses showed limited FDG uptake (SUVmax = 3.7). A tumor biopsy revealed the diagnosis of a grade 3 neuroendocrine tumor. Furthermore, the hepatic masses showed significant uptake on somatostatin receptor scintigraphy. Upon reevaluation, the primary resected specimen was found to include approximately 10% of neuroendocrine tumor components. This case suggests that different FDG uptake between primary and metastatic cancer may necessitate differential diagnosis.

On the analysis of functional PET (fPET)-FDG: baseline mischaracterization can introduce artifactual metabolic (de)activations.

Functional Positron Emission Tomography (fPET) with (bolus plus) constant infusion of [18F]-fluorodeoxyglucose FDG), known as fPET-FDG, is a recently introduced technique in human neuroimaging, enabling the detection of dynamic glucose metabolism changes within a single scan. However, the statistical analysis of fPET-FDG data remains challenging because its signal and noise characteristics differ from both classic bolus-administration FDG PET and from functional Magnetic Resonance Imaging (fMRI), which together compose the primary sources of inspiration for analytical methods used by fPET-FDG researchers. In this study, we present an investigate of how inaccuracies in modeling baseline FDG uptake can introduce artifactual patterns to detrended TAC residuals, potentially introducing spurious (de)activations to general linear model (GLM) analyses. By combining simulations and empirical data from both constant infusion and bolus-plus-constant infusion protocols, we evaluate the effects of various baseline modeling methods, including polynomial detrending, regression against the global mean time-activity curve, and two analytical methods based on tissue compartment model kinetics. Our findings indicate that improper baseline removal can introduce statistically significant artifactual effects, although these effects characterized in this study (~2-8%) are generally smaller than those reported by previous literature employing robust sensory stimulation (~10-30%). We discuss potential strategies to mitigate this issue, including informed baseline modeling, optimized tracer administration protocols, and careful experimental design. These insights aim to enhance the reliability of fPET-FDG in capturing true metabolic dynamics in neuroimaging research.

Imaging Glucose Metabolism and Dopaminergic Dysfunction in Sheep (Ovis aries) Brain Using Positron Emission Tomography Imaging Reveals Abnormalities in OVT73 Huntington's Disease Sheep.

Huntington's disease (HD) is a neurodegenerative disease that causes cognitive, movement, behavioral, and sleep disturbances, which over time result in progressive disability and eventually death. Clinical translation of novel therapeutics and imaging probes could be accelerated by additional testing in well-characterized large animal models of HD. The major goal of our preliminary cross-sectional study is to demonstrate the feasibility and utility of the unique transgenic sheep model of HD (OVT73) in positron emission tomography (PET) imaging. PET imaging studies were performed in healthy merino sheep (6 year old, n = 3) and OVT73 HD sheep (5.5 year old, n = 3, and 11 year old, n = 3). Region-of-interest and brain atlas labels were defined for regional analyses by using a sheep brain template. [18F]fluorodeoxyglucose ([18F]FDG) was employed to compare the regional brain glucose metabolism and variations in FDG uptake between control and HD sheep. We also used [18F]fluoro-3,4-dihydroxyphenylalanine ([18F]FDOPA) to compare the extent of striatal dysfunction and evaluated the binding potential (BPND) in key brain regions between the groups. Compared with healthy controls and 11 year old HD sheep, the 5.5 year old HD sheep exhibited significantly increased [18F]FDG uptake in several cortical and subcortical brain regions (P < 0.05-0.01). No difference in [18F]FDG uptake was observed between healthy controls and 11 year old HD sheep. Analysis of the [18F]FDOPA BPND parametric maps revealed clusters of reduced binding potential in the 5.5 year old and 11 year old HD sheep compared to the 6 year old control sheep. In this first-of-its-kind study, we showed the usefulness and validity of HD sheep model in imaging cerebral glucose metabolism and dopamine uptake using PET imaging. The identification of discrete patterns of metabolic abnormality using [18F]FDG and decline of [18F]FDOPA uptake may provide a useful means of quantifying early HD-related changes in these models, particularly in the transition from presymptomatic to early symptomatic phases of HD.

High 18F-FDG Uptake in Phosphoglyceride Crystal Deposition Disease of the Humerus Mimicking Chondrosarcoma.

A 82-year-old man presented with left humerus pain. MRI revealed a lesion in the left humerus appearing hyperintense on T2WI and hyperintense on DWI. 18F-FDG PET/CT demonstrated high FDG uptake in the lesion. Surgical resection was performed under the preoperative diagnosis of chondrosarcoma. However, a histopathological analysis confirmed the diagnosis of phosphoglyceride crystal deposition disease (PGDD). PGDD is an extremely rare disease, and this is the first report of PGDD occurring in the humerus. Bone lesions showing high uptake of FDG are usually malignant lesions; however, it is important to consider the possibility of benign diseases such as PGDD.

18F-FDG PET/CT Findings of Isolated Renal Metastasis From Squamous Cell Lung Cancer.

We present the 18F-FDG PET/CT findings of a 64-year-old man with isolated renal metastasis. He had a history of radical surgery for squamous cell lung cancer 14 months ago, followed by chemotherapy and immunotherapy. The renal metastasis presented as a small focus of increased FDG uptake in the restaging 18F-FDG PET/CT scan, which was regarded as renal cortical tracer retention. The renal metastasis was more prominent on the second PET/CT performed 5 months later. The patient subsequently underwent radical nephrectomy, and histopathological examination confirmed the diagnosis of renal squamous cell carcinoma metastasis.

Clinical scenarios of unusual FDG uptake in muscle.

Glucose is essential for muscle function and its uptake is influenced by aerobic conditions, hormonal regulations, and exercise. 18F-Fluorodeoxyglucose (FDG), a glucose analog used in PET/CT scans, can show incidental uptake in muscles, and thus careful interpretation is required to avoid misdiagnosis. Proper patient preparation and understanding of the clinical scenarios affecting FDG uptake are crucial for accurate PET/CT interpretation, thus ensuring precise diagnoses and avoiding unnecessary interventions. This review emphasizes the need to consider patient-specific factors in evaluating incidental FDG uptake in muscle.