Visual and whole-body quantitative analyses of 68 Ga-DOTATATE PET/CT for prognosis of outcome after PRRT with 177Lu-DOTATATE.

BACKGROUND: Somatostatin receptors (SSTR) represent an ideal target for nuclear theranostics applications in neuroendocrine tumors (NET). Studies suggest that high uptake on SSTR-PET is associated with response to SSTR peptide receptor radionuclide therapy (PRRT). The purpose of this study was to evaluate the role of baseline whole-body (WB) 68 Ga-DOTATATE PET/CT (SSTR-PET) quantitative parameters, and the presence of NET lesions without uptake on SSTR-PET, as outcome prognosticator in patients with NET treated with PRRT. METHODS: Patients with NET who underwent at least 4 177Lu-DOTATATE PRRT cycles between 07/2016 and 03/2021 were included in this retrospective analysis if they fulfilled the following inclusion criteria: SSTR-PET within 6 months of 1st PRRT cycle, follow-up CT and/or MRI performed > 6 months after the 4th cycle of PRRT. The SSTR-PET analysis consisted of a visual and a quantitative analysis done independently by two board-certified physicians. The visual analysis assessed the presence of NET lesions visible on the SSTR-PET co-registered CT. The quantitative analysis consisted in contouring all SSTR-avid lesions on SSTR-PET and extracting WB quantitative parameters: SUVmean (WB-SUVmean), SUVmax of the lesion with highest uptake (H-SUVmax), and tumor volume (WB-TV). WB-SSTR-PET parameters and the presence of SSTR-PET-negative lesions were correlated to radiologic response (assessed by RECIST 1.1 criteria) and progression-free survival (PFS). Fisher's exact test, Mann-Whitney's U test and Kaplan-Meier curves with Cox-regression analysis were used for the statistical analysis. RESULTS: Forty patients (F/M: 21/19; 34/40 with gastro-entero-pancreatic (GEP) NET, 6/40 with non-GEP NET) were included in the analysis. The median follow-up period after the 4th PRRT cycle was 25.7 months (range 15.2-59.1). Fourteen/40 (35%) patients showed radiologic response (RECIST PR). PFS event was observed in 17/40 (42.5%) patients. Thirteen/40 (32.5%) patients had SSTR-PET-negative lesions at baseline. Higher WB-SUVmean and H-SUVmax were associated with better response (p = 0.015 and 0.005, respectively). The presence of SSTR-PET-negative lesions and lower WB-SUVmean were associated with shorter PFS (p = 0.026 and 0.008, respectively). CONCLUSION: Visual and quantitative analyses of baseline SSTR-PET can yield valuable information to prognosticate outcomes after 177Lu-DOTATATE PRRT.

Comparison of Low-Energy and Medium-Energy Collimators for Thyroid Scintigraphy with 123I.

CE credit: For CE credit, you can access the test for this article, as well as additional JNMT CE tests, online at https://www.snmmilearningcenter.org Complete the test online no later than March 2025. Your online test will be scored immediately. You may make 3 attempts to pass the test and must answer 75% of the questions correctly to receive Continuing Education Hour (CEH) credit. Credit amounts can be found in the SNMMI Learning Center Activity. SNMMI members will have their CEH credit added to their VOICE transcript automatically; nonmembers will be able to print out a CE certificate upon successfully completing the test. The online test is free to SNMMI members; nonmembers must pay $15.00 by credit card when logging onto the website to take the test.123I thyroid scintigraphy can be performed with either a low-energy or a medium-energy (ME) collimator. The high-energy photon emissions from 123I cause septal penetration with scattered photons, which deteriorate image quality. The aim of this study was to evaluate the impact of collimator choice on 123I thyroid scintigraphy in clinical practice. Methods: Forty-seven patients who underwent thyroid planar scintigraphy with both a low-energy, high-resolution (LEHR) collimator and a ME collimator were prospectively recruited using the same imaging protocol. Image quality, collimator sensitivity, and estimation of thyroid size were assessed between LEHR and ME collimators and were compared with thyroid ultrasonography as the gold standard. Results: Images acquired with the ME collimator demonstrated reduced scattered background noise, improved thyroid-to-background contrast, and increased sensitivity in the thyroid gland compared with images acquired by the LEHR collimator. Manual measurement of the thyroid length is more accurate using the ME collimator. Automatic estimation of the thyroid area using the same thyroid threshold is larger in ME collimator images than in LEHR collimator images. Conclusion: Compared with the LEHR collimator, the ME collimator generates cleaner 123I thyroid scintigraphy images with less background noise and has higher collimator sensitivity for thyroid imaging. Different thyroid thresholds should be used to estimate the thyroid area and volume between low and ME collimators.

A 3-Year-Old Girl With Recent Onset of Seizures and Asymmetric Hypermetabolic Activity on 18F-FDG PET/CT.

ABSTRACT: A 3-year-old, previously healthy girl started having clusters of seizures, not responsive to multiple antiepileptic medications. High-dose prednisone and intravenous immunoglobulin could partially control the seizures. Lumbar puncture and CT were normal. An MRI showed right hemispheric injury and atrophy compatible with clinical suspicion of Rasmussen encephalitis. Neurological 18F-FDG PET/CT demonstrated asymmetric hypermetabolic activity in the right frontal and parietal lobes compatible with active inflammation. The patient underwent a right functional hemispherectomy, which confirmed clinical suspicion of Rasmussen encephalitis. During the follow-up, the patient has continued to take phenobarbital and levetiracetam (Keppra), with no recurrence of seizures.

18F-Sodium fluoride uptake is associated with severity of atherosclerotic stenosis in stable ischemic heart disease.

BACKGROUND: Increased uptake of 18F-Sodium fluoride (18F-NaF) PET has potential to identify atherosclerotic plaques that are vulnerable to rupture. Whether 18F-NaF PET can evaluate the significance of atherosclerotic plaque in patients with stable coronary artery disease is less clear. We evaluated 18F-NaF PET uptake in coronary arteries in patients without acute coronary artery syndrome to determine the association of 18F-NaF signal uptake with severity of coronary stenosis. METHODS AND RESULTS: We retrospectively identified 114 patients who received both regadenoson stress 82Rb myocardial perfusion PET and 18F-NaF PET study with an average interval of 5 months. Out of this cohort, forty-one patients underwent invasive coronary angiography. In a patient-based analysis, patients with ischemic regadenoson stress 82Rb PET had significantly higher coronary 18F-NaF uptake than patients with normal myocardial perfusion (P < .01). Among the 41 patients who underwent coronary angiography, per-vessel 18F-NaF uptake in both obstructive and nonobstructive coronary arteries was significantly higher than in normal coronary arteries (P < .05) regardless of the severity of coronary calcification. There was poor correlation between calcification and 18F-NaF uptake in coronary arteries (r = 0.41) CONCLUSION: Coronary arterial 18F-NaF uptake is associated with coronary stenosis severity in patients with stable coronary artery disease. 18F-NaF PET studies may be useful for characterizing coronary atherosclerotic plaques.

Incidental Detection of Elastofibroma Dorsi With 68Ga-FAPI-46 and 18F-FDG PET/CT in a Patient With Esophageal Cancer.

ABSTRACT: A 71-year-old man underwent 18F-FDG and 68Ga-FAPI-46 PET/CT for initial staging prior to surgery of a squamous cell carcinoma of the lower esophagus under the prospective study NCT04147494. Both scans showed increased uptake in the mid and distal esophagus without evidence of metastatic disease. A soft tissue right infrascapular mass with mild 18F-FDG and moderate 68Ga-FAPI-46 uptake was incidentally found. The patient underwent robotic-assisted Ivor-Lewis esophagectomy and excision of the right infrascapular mass. Histopathology of the right chest wall mass confirmed the diagnosis of elastofibroma.