Diffuse Uptake Research Articles

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.

Diffusely Increased FDG Uptake of the Kidney Caused by Severe Renal Artery Stenosis.

Renal artery stenosis can result in renovascular hypertension and ischemic nephropathy. We describe FDG PET/CT and delayed abdominal FDG PET/MRI findings in a kidney associated with severe renal artery stenosis resulting from renal artery invasion in retroperitoneal alveolar echinococcosis. The renal parenchyma showed diffusely increased activity on both FDG PET/CT and delayed FDG PET/MRI. There was no activity in the renal collecting system on FDG PET/CT and focal urine activity in the renal calyces on delayed FDG PET/MRI. This case indicates that renal artery stenosis should be included in the differential diagnosis of diffuse renal parenchymal FDG uptake.

Superscan Pattern on Bone Scintigraphy: A Comprehensive Review

Background/Objectives: The superscan pattern is a characteristic finding on bone scintigraphy, associated with a variety of metabolic bone diseases, malignancies, and other conditions. This pattern is characterized by a diffuse and intense uptake of radiotracer throughout the entire skeleton. Despite being a relatively rare finding, the superscan pattern can have significant clinical implications. Methods: This comprehensive review summarizes the available literature on the superscan pattern, focusing on its pathophysiology, clinical significance, and differential diagnoses. Relevant studies and case reports were analyzed to outline the diagnostic challenges associated with the interpretation of bone scintigraphy featuring the superscan pattern. Results: The literature highlights the clinical significance of the superscan pattern in various metabolic and oncologic conditions. Misinterpretation of this pattern can lead to diagnostic challenges, especially in distinguishing it from other pathologic conditions. Differential diagnosis remains crucial in the accurate interpretation and subsequent management of patients with this finding. Conclusions: This review provides a comprehensive overview of the superscan pattern on bone scintigraphy, aiming to assist clinicians in recognizing and managing this rare yet clinically important finding.

7699 Unanticipated Harmony: PD-L1 Inhibitor Treatment for Urothelial Cancer Resolving Graves' Disease in a Patient - A Case of Immune Modulation Surprises

Abstract Disclosure: K. Tiwari: None. C.A. Resta: None. Introduction: Programmed death ligand 1(PD-L1) inhibitors constitute a class of immune checkpoint inhibitors (ICI) employed in treating various cancers. Thyroid-related immune-related adverse events (irAEs), such as hypothyroidism, are found to be in 3.9% of patients with PD L1 treatments. This case explores a unique scenario where a patient with pre-existing Graves' disease, undergoing PD-L1 inhibitor therapy for cancer, experienced an unexpected sequence of events leading to the default treatment of Graves' disease and subsequent progression to hypothyroidism. Case Presentation: A 59-year-old male, who had been effectively managed on methimazole for Graves' disease over two years and had chosen not to pursue definitive therapy for the condition, presented with tremors and a bilaterally enlarged thyroid gland during treatment for urothelial carcinoma. Laboratory findings included a TSH of 0.03 mIU/L (nl 0.40-4.50 mIU/L), fT4 of 3.4 ng/dL (nl 0.8-1.8 ng/dl), and tT3 of 284ng/dl (nl 76-181 ng/dl). The patient had recently started treatment with Avelumab, a PD-L1 inhibitor, as maintenance therapy following 4 cycles of gemcitabine/cisplatin cycles. Concerned about worsening Graves' disease, the methimazole dose was increased, and follow-up labs were performed after three weeks. These results showed low-normal fT4 of 0.8 ng/dL, TSH of 1.01 mIU/L(N), and low T3 of 58 ng/dL. TSI was mildly elevated at 168%. Due to rapidly changing thyroid function tests and suspicion of thyroiditis, methimazole was stopped. A PET scan a week later indicated diffuse thyroid uptake consistent with thyroiditis. Repeat labs 10 days later revealed a TSH of 67.36 mIU/L(H) and fT4 of 0.4 ng/dL(L), indicative of overt primary hypothyroidism. The patient exhibited symptoms including fatigue, constipation, and cold intolerance. The patient was initiated on levothyroxine therapy to address overt primary hypothyroidism, likely secondary to destructive thyroiditis from ICI. Discussion: Thyroid irAEs are typically incidentally discovered during routine monitoring of ICI treatment. It includes thyrotoxicosis, subclinical hypothyroidism, and overt hypothyroidism. These events commonly occur in patients lacking pre-existing thyroid conditions. In contrast, our patient, with a history of Graves' disease, experienced resolution of Graves' disease following treatment with PD-L1 inhibitor use with subsequent progression to hypothyroidism. Conclusion: This case emphasizes the importance of recognizing atypical presentations of thyroid irAEs in individuals with pre-existing thyroid disorders undergoing ICI treatment. Presentation: 6/3/2024

8477 Medullary Thyroid Carcinoma Masquerading as a Cold Nodule in a Patient With Graves' Disease

Abstract Disclosure: T. Umashree: None. K.J. Farooqui: None. A. Mithal: None. Background: Only a handful of cases of MTC have been reported in the setting of Graves’ disease. Clinical Case: A 38 year old lady presented with symptoms of significant weight loss and palpitations for past six months. Thyromegaly was present, with non tender left lobe enlargement of about 3x3 cm. On further probing it was found that her father had been operated for thyroid cancer 22 years ago, the type of which patient was not aware of. TFTs reflected a thyroxtoxic state (TSH -<0.01mIU/mL [0.34-5.6] FT4 - 3.38 ng/dL [0.58-1.64] FT3 - 8.46 pg/mL [2.6-4.2]) and TRAb was positive (8.74 IU/L [<1.22]). USG neck revealed a hypoechoic lesion of 18x18x13 mm in left lobe thyroid with internal calcifications, with multiple bilateral non-significant lymph nodes. Technetium99 (Tc99) scan showed an enlarged left lobe, with diffuse thyroid uptake at 20 minutes of 4%, and a well-defined photopenic area in left lobe, corresponding to the nodule seen on USG. FNAC of the nodule was suggestive of Hürthle cell neoplasm and patient underwent left hemithyroidectomy. Surprisingly, HPE was consistent with medullary thyroid cancer. Serum calcitonin was raised at 148 pg/mL (N<4.8 for females) and plasma free metanephrines and normetanephrine were normal. F-18 DOPA PET CT showed uptake in residual right lobe of thyroid only, no other abnormal uptake was seen. She underwent completion thyroidectomy with central compartment clearance and is now under regular follow up. Genetic analysis showed RET gene mutation of Cys634Ser, which is heterozygous for MTC. Cold nodules in Graves’ disease should be viewed with suspicion, and while PTC and FTC have been reported more commonly, MTC is extremely rare in this setting. A calcitonin washout of the FNAC may have prevented this patient from undergoing two surgeries. Moreover, Hürthle cell change can also occur in C-cells of the thyroid, not just the follicular cells. Lastly, given the history of thyroid cancer in her father, index of suspicion of MTC should have been higher in this patient. Conclusion: Cold nodules in Graves’ Disease may be malignant, and should always be examined by FNAC. Though MTC is rare, it is not unknown in Grave’s disease. Presentation: 6/3/2024

8769 A Case of Metastatic and Catecholamine Producing Bilateral Pheochromocytoma in a Patient with RET Gene Mutation

Abstract Disclosure: R.A. Mayers: None. A. Szafran-Swietlik: None. RET mutation, observed in multiple endocrine neoplasia type 2 syndromes, is implicated in the development of pheochromocytomas of the kinase signaling cluster. Such tumors have lower metastatic risk and adrenergic production compared to the ones from the other clusters. We present a case of a metastatic, bilateral, small and biochemically active pheochromocytoma .This is the case of a 27-year-old man diagnosed with MEN 2A. He underwent total thyroidectomy due to medullary thyroid carcinoma at 2 years old. He was deemed cured and started on levothyroxine replacement. Since then, his plasma metanephrines by liquid chromatography-mass spectrometry and urine metanephrines done in a yearly basis as screening, were always within range of normality. Over the years, he developed substance abuse disorder with use of Kratom and methamphetamines and was admitted in a rehabilitation center multiple times in the last three years. During this time, the patient was reported to be slightly tachycardiac which was initially attributed to the use of substances. On the last year, an echocardiogram done as evaluation of his tachycardia showed an ejection fraction of 35%. Later, his annual metanephrine levels were markedly elevated (free metanephrine: 137 pg/mL and free normetanephrine : 157 pg/mL, normal ranges reported as less than 57 pg/mL and less than 148 pg/mL respectively). Abdominal tomography showed a right adrenal nodule of 1.2 cm and a left adrenal nodule of 1.6 cm, both with more than 10 Hounsfield Units. A Metaiodobenzylguanidine scan revealed a left adrenal nodule of 1.8 cm with diffuse radiotracer uptake, a right adrenal nodule of 1.2 cm with radiotracer activity and 3 subtle areas of focally increased radiotracer activity in the liver, two in left hepatic lobe and other in posterior right upper lobe. He underwent bilateral adrenalectomy with cortical sparring. Pathology results evidenced a left adrenal with a unifocal mass of 1.8 cm and a right adrenal with a mass of 1.2 cm , both without lymphovascular, capsular, local invasion or necrosis, a mitotic rate of 1-2 without atypical mitosis, not encapsulated with clean margins and positive for synaptophysin , chromogranin and S100 stains. An additional mass of 0.7 cm on the right adrenal gland was described with similar characteristics to the described before except for the involvement of the surgical margins. Currently on the literature there are different opinions regarding screening approach for pheochromocytomas in the presence of RET mutations. There are not strong recommendations regarding the use of imaging as a screening tool in this group of patients. It is important to consider that there are cases, as the one described in this report, that might present metastatic disease even with the presence of small pheochromocytomas that belong to the cluster of kinase signaling. Presentation: 6/3/2024

9336 Bone Pain Caused By Computer Cleaners Huffing

Abstract Disclosure: M. Sokrab: None. V.S. Rao: None. P. Shah: None. J.L. Shaker: None. A 47 year-old woman was evaluated 2/2024 for bone pain especially in the forearms and lower legs. The symptoms were worse since about 4/2023. Initial evaluation 11/2023 revealed elevated alkaline phosphatase levels and markers of bone remodeling (P1NP 396 ug/dl, normal; 20-101 and C-telopeptide 4389, normal; 177-1015. The plasma fluoride level was 17.1 mcmol/L (normal; < 4.1). There was no history of excess exposure to fluoride from dental products. She did not drink powdered iced tea or use green tea capsules. There was no industrial fluoride exposure and she consumed city water. She used inhaled fluticasone twice weekly but was not taking other fluoride containing medications, particularly voriconazole. She reported huffing computer cleaner containing difluoroethane between mid 2023 and early 2024. On examination, she had diffuse skeletal tenderness especially over her forearms and lower legs. Lab data revealed calcium 9.2 mg/dl (normal, 8.6-10.2), albumin 4 g/dl, phosphorus 3.6 mg/dl (normal, 2.5-4.5), creatinine 1.08 mg/dl (normal, 0.5-1.1), ionized calcium 1.33 mmol/l (normal, 1.18-1.33), pH normalized ionized calcium 1.25 mmol/l (normal, 1.18-1.33), PTH 126 pg/ml (normal, 15-72), 25(OH)vitamin D 29.5 ng/ml (normal, 20-50), and alkaline phosphatase 287 u/l (normal, 40-120) with a predominant elevation of the bone isoenzyme. The bone specific alkaline phosphatase was 93.4 mcg/l (normal, 7.0-22.4). The SPEP revealed a biclonal IgG Kappa monoclonal protein too small to quantify. The repeat fluoride level was 1.2 mg/l (normal, <0.05). Imaging included diffuse uptake on bone scan as well as periostitis/periosteal thickening involving legs, arms, and hands. There was axial osteosclerosis. Our patient appears to have skeletal fluorosis. Although the time-line of reported huffing and symptoms is not completely consistent, we could find no other exposure to fluoride and speculate she may have been huffing before she recalls. Skeletal fluorosis (SF) is endemic in some countries generally related to drinking water or tea that is high in fluoride, In the US, SF is caused by abnormal use of fluoride-containing dental products, excessive consumption of powdered iced tea containing fluoride, chronic use of the antifungal agent voriconazole and now more often huffing abuse of computer cleaners containing difluoroethane. The number of reported cases of huffing-related SF appears to be increasing and greater awareness of this problem is needed. Presentation: 6/1/2024

Diffuse Uptake of 68Ga-Pentixafor in the Breasts During the Ovulatory Phase in a Patient With SAPHO Syndrome.

We report a case of a woman with SAPHO syndrome who exhibited increased tracer uptake in the sternal angle on a 99mTc-MDP bone scan. This patient was enrolled in a 68Ga-pentixafor PET/CT trial for inflammatory diseases. The PET/CT showed no abnormal tracer uptake in the sternal angle. Unexpectedly, diffuse uptake of 68Ga-pentixafor was observed in both breasts, which might be due to hormonal stimulation because the woman underwent the 68Ga-pentixafor PET/CT scan during the ovulatory phase.

Incremental prognostic value of 18F-FDG myocardial ischemic memory imaging for major adverse cardiovascular events in patients with suspected unstable angina

BackgroundThe additional prognostic value of 18F-FDG PET myocardial ischemic memory imaging for patients with suspected unstable angina (UA) is not well established. This study aimed to determine whether 18F-FDG PET imaging provides incremental prognostic information for predicting major adverse cardiac events (MACE) compared to clinical risk factors, GRACE score, and coronary artery calcium score (CACS) in suspected UA patients. MethodsIn this post-hoc analysis of a prospective study, 265 suspected UA patients (62.3% male, mean age 65.0±9.4 years) were enrolled. 18F-FDG positive was defined as focal or focal on diffuse uptake patterns. MACE included cardiovascular death, acute myocardial infarction, heart failure, rehospitalization for UA, and stroke. Multivariable Cox regression was used to identify predictors of MACE, and the incremental prognostic value of 18F-FDG PET imaging was assessed using C-index, net reclassification improvement (NRI), and integrated discrimination improvement (IDI). ResultsOver a median follow-up of 25 months, 51 patients (19.2%) experienced MACE. 18F-FDG positive (HR=3.220, 95% CI: 1.630-6.360, P<0.001) , as well as 18F-FDG standardized uptake ratio (SUR) (HR=1.330, 95%CI: 1.131-1.564, P=0.0006) and Extent (HR=1.045, 95%CI: 1.028-1.062, P<0.0001), were independent predictors of MACE. The addition of 18F-FDG PET imaging significantly improved risk stratification beyond clinical factors, the GRACE score, and CACS, with improved C-index (0.769 vs 0.688, P=0.045), NRI (0.324, P=0.020), and IDI (0.055, P=0.027). Conclusion18F-FDG PET myocardial ischemic memory imaging significantly improves prognostic assessment for suspected UA patients, providing valuable additional risk stratification beyond clinical risk factors, GRACE score, and CACS.

Prognostic significance of diffuse increased fluorine-18-fluorodeoxyglucose (18F-FDG) uptake within the reticuloendothelial system in lymphoma patients.

As constituents of the reticuloendothelial system, the spleen and bone marrow (BM) have been recognized as integral components of the systemic inflammatory response in cancer contexts, thereby serving as predictive indicators for assessing cancer prognosis. Fluorine-18-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET)/computed tomography (CT) has attained widespread utilization for staging, assessing treatment response, and prognostication in lymphoma patients. Several investigations have proposed that focal increased 18F-FDG uptake in the BM or spleen may correlate with malignant involvement in lymphoma. However, scant data exist regarding the implications of diffuse BM and splenic uptake. This study aimed to explore the relationships between metabolic parameters of the spleen and BM on 18F-FDG PET/CT and inflammatory markers, and to assess their prognostic value in patients with lymphoma. A retrospective analysis was conducted on 118 patients newly diagnosed with malignant lymphoma, who underwent 18F-FDG PET/CT and exhibited diffuse increased splenic or BM uptake in 18F-FDG PET/CT imaging. The mean standardized uptake value (SUV) of the spleen, BM, and liver was calculated. The association between metabolic variables and systemic inflammatory markers was investigated, and the prognostic significance of clinicopathological and PET parameters was assessed using overall survival (OS) and progression-free survival (PFS). A statistically significant correlation was found between the spleen-to-liver SUV ratio (SLR) and inflammatory markers such as C-reactive protein (r=0.264, P=0.007) and platelet-to-lymphocyte ratio (r=0.227, P=0.021). No significant correlation was observed between BM-to-liver SUV ratio (BLR) and hematologic parameters, while concordance analysis revealed a fair agreement between BLR and bone marrow biopsy (BMB) (Cohen's Kappa-κ =0.271, P=0.002). In patients with aggressive non-Hodgkin lymphoma, both SLR [P=0.017, HR 2.715, 95% confidence interval (CI): 0.875-8.428] and BLR (P=0.044, HR 0.795, 95% CI: 0.348-1.813) were significantly linked to OS, while SLR (P=0.019, HR 2.223, 95% CI: 1.139-4.342) emerged as a significant prognostic factor for PFS. This study highlighted that diffuse increased splenic 18F-FDG uptake in lymphoma patients was closely associated with inflammation, whereas diffuse BM uptake was likely attributable to BM infiltration rather than inflammatory changes. Furthermore, both parameters held promise as prognostic indicators for patients with aggressive lymphoma.

Regional variation in technetium pyrophosphate (PYP) uptake in transthyretin cardiac amyloidosis (ATTR-CA) and concomitant myocardial infarction: A case series

- Diffuse and patchy myocardial uptake of Tc-99m PYP is well established in cases of ATTR-CA. - Chronic myocardial infarction leads to regional myocardial thinning and lack of vascular supply can present as regional sparing 'cold spot' on Tc-99m PYP imaging. - The absence of Tc-99m PYP uptake in vascular regions should raise the possibility of underlying scar.

Significance of incidental thyroid 18 F-fluorocholine uptake in patients with hyperparathyroidism imaged for localizing hyperfunctioning parathyroid glands.

18 F-fluorocholine PET/CT is considered the imaging gold standard for detection of hyperfunctioning parathyroid glands . However, increased uptake might also occur in the thyroid gland. The aim of our study was to assess the incidence and significance of 18 F-fluorocholine uptake in the thyroid gland in patients with hyperparathyroidism. This retrospective study includes 195 consecutive patients with hyperparathyroidism, who underwent 18 F-fluorocholine PET/CT, for detection of hyperfunctioning parathyroid glands. PET/CT images were reviewed by two nuclear medicine physicians for the presence of focal or diffuse thyroid uptake. PET/CT results were compared with laboratory parameters, ultrasonography, EU-TIRADS classification in the presence of thyroid nodules, cytology, and final histology. 25 patients (13%) showed 18 F-fluorocholine uptake in the thyroid gland: focal thyroid uptake (FTU) in 7 patients (4%), diffuse thyroid uptake (DTU) in 8 patients (4%), and combined uptake (FTU + DTU) in 10 patients (5%), with a total of 20 active thyroid nodules. There was no correlation between EU-TIRADS classification and PET parameters. One highly 18 F-fluorocholine active thyroid nodule and one isoactive thyroid nodule turned out to be papillary thyroid cancers in the final histology; 50% of the patients with DTU had Hashimoto's thyroiditis. Incidental 18 F-fluorocholine uptake in the thyroid gland was observed in 13% of patients. As reported for 18 F-FDG, focal 18 F-fluorocholine uptake might represent thyroid cancer and should be evaluated with ultrasound and, if indicated, with fine-needle aspiration cytology. Diffuse 18 F-fluorocholine uptake most likely represents multinodular goiter or Hashimoto's thyroiditis.

International Benchmark for Total Metabolic Tumor Volume Measurement in Baseline 18F-FDG PET/CT of Lymphoma Patients: A Milestone Toward Clinical Implementation.

Total metabolic tumor volume (TMTV) is prognostic in lymphoma. However, cutoff values for risk stratification vary markedly, according to the tumor delineation method used. We aimed to create a standardized TMTV benchmark datasetallowing TMTV to be tested and applied as a reproducible biomarker. Methods: Sixty baseline 18F-FDG PET/CT scans were identified with a range of disease distributions (20 follicular, 20 Hodgkin, and 20 diffuse large B-cell lymphoma). TMTV was measured by 12 nuclear medicine experts, each analyzing 20 cases split across subtypes, with each case processed by 3-4 readers. LIFEx or ACCURATE software was chosen according to reader preference. Analysis was performed stepwise: TMTV1 with automated preselection of lesions using an SUV of at least 4 and a volume of at least 3 cm3 with single-click removal of physiologic uptake; TMTV2 with additional removal of reactive bone marrow and spleen with single clicks; TMTV3 with manual editing to remove other physiologic uptake, if required; and TMTV4 with optional addition of lesions using mouse clicks with an SUV of at least 4 (no volume threshold). Results: The final TMTV (TMTV4) ranged from 8 to 2,288 cm3, showing excellent agreement among all readers in 87% of cases (52/60) with a difference of less than 10% or less than 10 cm3 In 70% of the cases, TMTV4 equaled TMTV1, requiring no additional reader interaction. Differences in the TMTV4 were exclusively related to reader interpretation of lesion inclusion or physiologic high-uptake region removal, not to the choice of software. For 5 cases, large TMTV differences (>25%) were due to disagreement about inclusion of diffuse splenic uptake. Conclusion: The proposed segmentation method enabled highly reproducible TMTV measurements, with minimal reader interaction in 70% of the patients. The inclusion or exclusion of diffuse splenic uptake requires definition of specific criteria according to lymphoma subtype. The publicly available proposed benchmark allows comparison of study results and could serve as a reference to test improvements using other segmentation approaches.

Relationship of Ketosis With Myocardial Glucose Uptake Among Patients Undergoing FDG PET/CT for Evaluation of Cardiac Sarcoidosis.

Fluorine-18 fluorodeoxyglucose (FDG) with positron emission tomography (PET) is the standard for detecting myocardial inflammation in cardiac sarcoidosis, requiring preparation with the ketogenic diet (KD) to achieve myocardial glucose suppression. Despite this, incomplete myocardial glucose suppression remains a significant issue, and strategies to reduce myocardial glucose uptake (MGU) and identify incomplete myocardial glucose suppression are required. This study sought to understand the relationship between point-of-care beta-hydroxybutyrate (BHB) and different patterns of MGU and between KD and fasting duration with MGU in patients undergoing evaluation for cardiac sarcoidosis. We prospectively included 471 outpatients who underwent FDG-PET for cardiac sarcoidosis evaluation, followed the KD for 1 (n=100), 2 (n=29), and ≥3 days (n=342), fasted for at least 12 hours, and had BHB levels measured immediately before FDG injection. Images were classified as (1) no MGU (negative), (2) focal/multifocal (positive), (3) diffuse (nondiagnostic), or (4) nonspecific uptake (NS-MGU). Cardiac FDG-PET scans were interpreted as the following: 376 (79.83%) negative; 61 (12.95%) positive; 14 (2.97%) diffuse; and 20 (4.25%) NS-MGU. There was a strong negative relationship between BHB levels and MGU (P<0.0001). BHB levels increased significantly with KD duration (P<0.0001) and fasting time (P=0.0067). The combined rate of diffuse, NS-MGU, and positive scans (34%, 28%, 16%) decreased inversely with KD duration (1, 2, and ≥3 days, respectively). However, MGU was not different across different fasting times (P=0.6). Blood glucose levels were not associated with MGU (P=0.17) and only weakly associated with BHB levels (R2=0.03; P<0.001). We observed a strong inverse relationship between ketosis and patterns of MGU. Longer KD and fasting durations are associated with higher ketosis. However, only KD duration was associated with lower rates of MGU. Measurement of BHB levels before FDG-PET using point-of-care testing is feasible and may facilitate the management of patients referred for myocardial inflammation.

Clinical use of [18F]fluoro-ethyl-L-tyrosine PET co-registered with MRI for localizing prolactinoma remnants

PurposeTo assess the utility of [18F]fluoroethyl-L-tyrosine PET co-registered with magnetic resonance imaging ([18F]FET-PET/MRICR) in patients with difficult-to-localize prolactinoma to inform clinical decision-making and (surgical) treatment planning.MethodsRetrospective cohort study of 17 consecutive patients with prolactinoma undergoing [18F]FET-PET/MRICR between October 2020 and September 2022 for either (1) additional information in case of difficult-to-visualize remnants after prior transsphenoidal surgery (TSS), or pharmacological treatment, or (2) radiological diagnosis in absence of a (clear) adenoma on diagnostic/post-treatment conventional MRI.Results[18F]FET-PET/MRICR identified a lesion in 14/17 patients, yet failed to identify active lesions in 2 patients with negative conventional MRI despite prolactin > 7.5 times upper limit of normal. [18F]FET-PET/MRICR results were inconclusive in 1 patient due to diffuse tracer uptake 10 weeks post-surgery. [18F]FET-PET/MRICR was completely concordant with a suspected lesion on conventional MRI in 10/17 patients, and partially concordant in 3/17 patients. New foci were identified in 4/17 patients. The [18F]FET-PET/MRICR conclusions influenced clinical shared decision-making in 15/17 patients, of whom 7 patients underwent TSS and 8 refrained from TSS. One patient underwent TSS despite negative [18F]FET-PET/MRICR, and one patient underwent additional imaging. Intraoperative findings corresponded with [18F]FET-PET/MRICR in 5/8 patients, and immunohistochemistry was positive in 5/8 patients. The treatment goal was achieved in 7/8 patients, and remission was achieved in 5/7 patients in whom total resection was considered feasible.Conclusion[18F]FET-PET/MRICR can be of added value in the preoperative decision-making process for selected patients with difficult-to-localize prolactinoma (remnants), or patients lacking a substrate on conventional MRI.

FDG altered biodistribution in white adipose tissue, a rare entity: case report and review of the literature

PurposeAltered 18F-fluorodeoxyglucose (FDG) biodistribution due to patient factors such as exercise and inadequate fasting are well established causes of limited diagnostic efficacy. In addition, medications such as G-CSF are known to affect uptake of FDG by bone marrow and spleen. In this study, we present a case of increased white adipose uptake in a pediatric lymphoma patient who recently received high dose dexamethasone and review the relevant literature regarding this rare and poorly understood pattern of altered FDG biodistribution.MethodsA 14-year-old male patient diagnosed with B-cell lymphoblastic lymphoma underwent FDG-PET/CT for restaging shortly after completing an induction chemotherapy regimen. Images revealed diffuse FDG uptake localizing to white adipose tissue, attributed to the 29-day course of dexamethasone which was completed two days prior. A diagnostically adequate study with relative normalization of FDG biodistribution was obtained seven days later.ResultsIn our review of the literature, diffuse FDG uptake by white fat is a rare occurrence and has only been reported by a few case reports and early observational studies. In addition to patients receiving corticosteroids, other cases of medication-induced adipose remodeling such as patients receiving highly active antiretroviral therapy have been documented with similar patterns of increased white adipose tissue activity.ConclusionCorticosteroid-induced white fat uptake of FDG is a rare phenomenon that can limit diagnostic accuracy of FDG-PET/CT and necessitate repeat imaging. Current evidence suggests that a wait period of at least one week after discontinuation of corticosteroids is sufficient to allow for decreased white fat uptake and increased diagnostic accuracy.

Imaging and clinical characteristics of incidental abnormal thyroid uptake on PSMA PET/CT.

e18077 Background: To investigate the incidence, features, and clinical characteristics of unexpected prostate-specific membrane antigen (PSMA) uptake within the thyroid gland of patients with prostate cancer (PCa) who underwent F-18 DCFPyL PSMA PET/CT. Methods: We retrospectively reviewed a cohort of 1148 PCa patients who underwent PSMA PET/CT at our institution between 11/2021 - 09/2023. Scans with abnormal thyroid uptake were identified. Clinical data included patient demographics, PCa history, Gleason score, prostate specific antigen (PSA), ultrasonography (US), fine needle aspirate (FNA) / thyroidectomy, histopathology, and history of neck radiation or prior malignancy. Each scan was further analyzed with lesion-specific iso-contour method (42% cutoff) to obtain PET parameters (most prominent nodule SUVmax, SUVmean, PSMA volume, tumor lesion PSMA, contralateral gland SUVmax, SUVmax-nodule / SUVmax-contralateral gland ratio, most prominent PCa lesion SUVmax), PCa tumor distribution, and tumor volume. CT-related variables (nodule number, dominant nodule size, short/long axis ratio, CT-HU, integral total value) were also collected. Pearson's chi-square testing and Kruskal-Wallis testing was performed for categorical and nonparametric data respectively. Receiver operating characteristic (ROC) curves with area under curve (AUC) value were determined using IBM SPSS (version 29.0). Results: Of the 1148 PSMA PET/CTs, 60 (5.2%) had abnormal thyroid uptake (nodular: 58, diffuse: 2). Diffuse uptake was found to represent thyroiditis in both patients. 43 (56.7%) had an US, 20 (33%) were biopsied (11 benign, 5 indeterminate, 4 malignant), and 5 (8.3%) pursued thyroidectomy (3 malignant, 2 benign). 22 patients (36.7%) had histopathology data and 5 malignancies (2 PCa, 1 CLL, 2 primary thyroid) were identified. Nodule size was larger in those who had an US relative to those who did not. Among those with US data, no significant differences in clinical or histopathological parameters were seen. SUVmax (p: 0.01; AUC: 0.876, 95%CI: 0.731-1.0) and SUVmean (p:0.01; AUC: 0.871, 95%CI: 0.722-1.0) were higher in the malignant group. Nodule SUVmax/contralateral gland SUVmax ratio showed borderline significance (p = 0.05). Conclusions: Incidental PSMA PET uptake in the thyroid gland is seen in approximately 5% of patients. Focal uptake should prompt consideration of US and FNA due to the possibility of prostate cancer metastasis and thyroid cancer. SUVmax/mean is higher in malignant lesions.

Exploring the role of the combination of FDG-PET plus whole body MRI for staging patients with high-risk smoldering myeloma: A prospective trial.

7569 Background: According to IMWG criteria, Smoldering Multiple Myeloma (SMM) is an asymptomatic stage characterized by M-spike &lt; 3 g/dl serum and/or bone marrow plasma cells infiltration between 10-59% in absence of myeloma-defining events and organ damage. In SMM setting, it is really important to differntiate high risk SMM (HR-SMM), in which treatment could be available thanks to clinical trials. 2016 IMWG criteria state that detection of bone lesions is mandatory for diagnosis of multiple myeloma and essential for diagnosis of SMM. It is really important to clarify in SMM the best imaging analysis in order to perform a correct diagnosis, and particularly it is necessary to define if the combination of FDG-PET/TC and WB-MRI could improve the assessment of lytic lesions and so the discrimination between high risk SMM and symptomatic MM. Methods: In our Institution we conducted a prospective trial, based on integrated new generation imaging, aiming to improve patients’ stadiation and to define its prognostic implications. From January 2021 to January 2024, we performed a prospective trial enrolling 26 consecutive newly diagnosed high risk SMM, according to IMWG, in which WB-MRI was performed according to MY-RADS criteria in combination with FDG PET-CT (median age 56; range 36-85). Results: Our comparison between WB-MRI and FDG PET-CT, showed a discordance between the two imaging modalities in 4/26 (15%) cases. In particular, in 3/26 (12%) cases WB-MRI showed bone lesions that have lead to symptomatic MM diagnosis according to IMWG criteria, while PET-CT was negative. In one case, PET-CT showed a diffuse uptake, not diagnostic for MM, while WB-MRI was negative. WB-MRI showed a 100% of accuracy in detecting SMM and MM. Therefore, WB-MRI has lead to a modification of the prognosis and treatment approach (observation in SMM vs treatment in symptomatic MM) in 3/26 patients (11%) (i.e. Figure 1, with DWI of C2 lesion). Furthermore, in 5/23 (22%) cases of confirmed SMM WB-MRI showed a slight diffuse alteration pattern of bone marrow without any overt lytic bone lesion, which could be a potential prognostic evidence. Conclusions: Our results support a fundamental role of WB-MRI in combination with FDG PET/CT in the stadiation of patients with newly diagnosed high risk SMM, which could modify prognosis and treatment, improving the differentiation with symptomatic MM. In particular, combination of WB-MRI plus FDG PET/CT could be more accurate in the detection of bone lesions than FDG PET/CT alone, being able to anticipate symptomatic MM diagnosis and consequently its treatment. Moreover, a diffuse pattern of marrow involvement could be detected in some HR-SMM patients without any overt lytic lesions: it is questionable if this group of patients is associated with a rapid progression in lytic lesions and so in symptomatic MM diagnosis. Prospective data on evolution of these patients are pending.

Incidental visualization of right ventricle on F-18 FDG PET/CT as an early indicator of heart failure

A 55 year hypertensive man presented with shortness of breath, productive cough and loss of weight. To rule out underlying malignancy, he underwent F-18 FDG PET/CT which showed bronchiectatic changes and tree-in bud nodules in bilateral lung fields with no definitive of evidence of metabolically active disease to suggest malignancy. There was no organomegaly and pulmonary to aorta ratio was also normal (0.73). However, diffuse FDG uptake was seen in the right ventricle which is uncommon due to less muscular mass in comparison to the left ventricle. The serum NT- pro BNP was raised to 265 pg/ml (upper limit less than 125 pg/ml) confirming heart failure.

Diffused Pulmonary Uptake of Tc-99m Methylene Diphosphonate Bone Scan in Patient with Prostate Cancer without Blood Test and Correlative/Cross-Sectional Imaging Abnormalities: A Case Report

Introduction: Bone scan using Tc-99m methylene diphosphonate (MDP) is a commonly used procedure for evaluating bone metastasis in cancer patients. Extra-osseous pulmonary uptake in bone scans is mostly an incidental finding and occurs in a multitude of disorders. Clinicians should be alert to any findings on clinical or complementary diagnostic tools. We presented a case of prostate cancer male patients who demonstrated diffuse pulmonary uptake on Tc-99m MDP bone scan without any blood test and correlative/cross-sectional imaging abnormality Case Presentation: An 80-year-old male with adenocarcinoma of the prostate with a Gleason score of 6 (3+3). The PSA level was 0.009. The patient had a history of recurrent atrial fibrillation (AF), postural dizziness, HTN, Gout, and chronic renal failure, but all of these comorbidities were under control. The patient underwent a bone scan to annually check for the presence of bone metastases. Three hours after administering 740 MBq Tc-99m MDP intravenously. The reports didn’t show any increased uptake that would indicate metastases in the bones. Instead, diffuse bilateral pulmonary uptake and a mild increase in cardiac uptake were present. On the same day, a computed tomography (CT) scan of the thorax revealed 3 micro-nodules in the right upper lung that were described as benign lesions, and a chest X-ray confirmed normal results. The patient’s laboratory results were within normal range, and there were no clinical lung symptoms or complaints. Considering the patient history of persistent AF, chronic renal failure, and a complaint of postural dizziness, the bone scan finding may indicate involvement of amyloidosis. The relationship between amyloidosis and cancer was also widely noted. Conclusions: Tc-99m MDP may play a role in evaluating amyloidosis involvement in an uncommon place such as the lungs. Future research should focus on analyzing diagnostic options in the patient’s condition in this situation. Keywords: cancer, diffused pulmonary uptake, amyloidosis, bone scan