Clinical Nuclear Medicine : Recent

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Clinical Evaluation of 18F-PI-2620 as a Potent PET Radiotracer Imaging Tau Protein in Alzheimer Disease and Other Neurodegenerative Diseases Compared With 18F-THK-5351

imagePurpose
PET is a useful tool for detecting the presence and extent of brain tau accumulation. However, most first-generation tau PET tracers are limited for high off-target binding and detection of tau in non-Alzheimer disease (AD). This study evaluated potential clinical applications of 18F-PI-2620 as a novel PET tracer with a high binding affinity for tau deposition in AD and non-AD tauopathies.
Methods
Twenty-six participants diagnosed with either mild cognitive impairment, probable AD, frontotemporal dementia, or parkinsonism, as well as healthy controls underwent a 60- to 90-minute brain PET scan after 7 mci (259 MBq) injection of 18F-PI-2620. Some participants had previous PET scans using 18F-THK-5351 or 18F-FP-CIT for dopamine transporter imaging.
Results
All participants showed no increase in off-target binding in basal ganglia on 18F-PI-2620 PET images, as noted for first-generation tau tracers. Aβ+ mild cognitive impairment or AD patients showed diverse cortical 18F-PI-2620 uptake in frontotemporoparietal cortex that correlated with Mini-Mental Status Examination (ρ = −0.692, P = 0.013). Aβ+ Parkinson disease with dementia and (Aβ unknown) primary progressive aphasia patients also showed increased 18F-PI-2620 uptakes in the frontotemporoparietal cortex. Patients with parkinsonism showed increased uptakes in the pallidum compared with Aβ− healthy controls (left: 1.41 ± 0.14 vs 1.04 ± 0.13, P = 0.014; right: 1.18 ± 0.16 vs 0.95 ± 0.07, P = 0.014).
Conclusions
18F-PI-2620 PET might be a sensitive tool to detect cortical tau deposits in patients with Aβ+ AD and Aβ+ non-AD tauopathies. Furthermore, this study showed that “off-target” binding in the basal ganglia does not affect 18F-PI-2620.

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https://journals.lww.com/nuclearmed/Fulltext/2020/11000/Clinical_Evaluation_of_18F_PI_2620_as_a_Potent_PET.1.aspx

Clinical and Striatal Dopamine Transporter Predictors of Mild Behavioral Impairment in Drug-Naive Parkinson Disease

imagePurpose
Neuropsychiatric symptoms are important and frequent nonmotor features in Parkinson disease (PD). We explored mild behavioral impairment (MBI) in drug-naive patients with PD and its clinical and dopamine transporter (DAT) correlates.
Methods
We recruited 275 drug-naive patients with PD who had undergone Unified Parkinson’s Disease Rating Scale, a neuropsychological battery, Neuropsychiatric Inventory, and N-(3-[18F]fluoropropyl)-2β-carbon ethoxy-3β-(4-iodophenyl) PET within 6 months. Patients with PD were divided into groups without MBI (PD-MBI−, n = 186) and with MBI (PD-MBI+, n = 89) according to the Neuropsychiatric Inventory. We performed comparative analysis of DAT availability, cognitive function, and motor deficits between the groups.
Results
Mild behavioral impairment was found in 32.4% of PD patients at the time of diagnosis, and affective dysregulation and decreased motivation were the 2 most common neuropsychiatric domains. Dopamine transporter availability in the anterior caudate (odds ratio, 0.60; P = 0.016) and anterior putamen (odds ratio, 0.58; P = 0.008) was associated with the development of MBI in PD. PD-MBI+ group had a lower z-score in memory-related tests and Stroop color reading test than PD-MBI− group. PD-MBI+ group had a higher Unified Parkinson’s Disease Rating Scale motor score after controlling for DAT availability in the posterior putamen than PD-MBI− group (P = 0.007).
Conclusions
This study suggests that early behavioral impairment is associated with more pathological involvement in the anterior striatum, memory and frontal dysfunction, and motor deficits, which could be regarded as a different phenotype in PD.

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https://journals.lww.com/nuclearmed/Fulltext/2020/11000/Clinical_and_Striatal_Dopamine_Transporter.35.aspx

Extramedullary Myeloma of the Uterus on 18F-FDG PET/CT: A Rare Manifestation of Multiple Myeloma

imageInvolvement of the uterus by myeloma is an extremely rare manifestation of extramedullary multiple myeloma (MM), denoting a poor prognosis. Extramedullary MM occurs in 7% to 18% of newly diagnosed patients with MM, and 6% to 20% of patients can develop it later. We present a case of extramedullary MM of the uterus suspected on 18F-FDG PET/CT as a site of disease recurrence in a 47-year-old woman previously in remission. Further evaluation with pelvic MRI identified an infiltrative process involving the uterus, and subsequent tissue sampling confirmed malignant plasma cell infiltration of the uterus. This case highlights a rare site of myeloma recurrence, which can be detected by 18F-FDG PET/CT.

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https://journals.lww.com/nuclearmed/Fulltext/2020/11000/Extramedullary_Myeloma_of_the_Uterus_on_18F_FDG.9.aspx

Comparison of Contrast-Enhanced CT + CT Enterography and 68Ga-DOTANOC PET/CT in Gastroenteropancreatic Neuroendocrine Tumors

imageBackground
Increase in incidence of neuroendocrine tumors (NETs) has been attributed in part to the availability of sensitive diagnostic modalities, such as 68Ga-DOTA-peptide PET/CT. However, it suffers from problems such as obscurement of tracer-avid lesions by physiological gut activity and collapsed gut lumen. Contrast-enhanced CT and CT enterography (CTE) do not have these drawbacks.
Purpose
The aim of this study was to compare the diagnostic performances of contrast-enhanced CT + CTE and the 68Ga-DOTA-peptide PET/noncontrast CT in GEP-NETs.
Methods
Fifty-six patients (mean age, 57.8 ± 13.3 years [male:female, 1.95:1]), with histopathologically proven gastroenteropancreatic NETs, who had undergone both 68Ga-DOTANOC-PET/NCCT (60 minutes, post–IV injection of 111–185 MBq) and contrast-enhanced CT (CECT) + CTE (using 1.5–2 L isotonic mannitol solution and 1–2 mg/kg of IV contrast), were retrospectively selected. Twenty-three patients had been referred for identification of primary lesions and 33 for staging/restaging. The scans were independently evaluated by 2 blinded physicians, who documented the number and site of lesions, with reporting confidence (3 = high confidence, 2 = equivocal confidence, 1 = low confidence). Reference standard was created using clinical, biochemical, and imaging parameters (ie, uptake and contrast enhancement), along with corroboration from previous or follow-up scans. Finally, PET images coregistered to the CECT + CTE were independently evaluated for any additional benefit.
Results
The numbers of primary lesions detected by CECT + CTE and PET/CT were 69 and 57, respectively. Lesion-wise sensitivities for patients with unknown primary in CECT + CTE and PET/CT were 57.7% (95% confidence interval [CI], 39.0%–74.5%) and 71.4% (95% CI, 52.9%–84.7%), respectively. Corresponding numbers in patients who had come for staging/restaging were 73.2% (95% CI, 58.1%–84.3%) and 73.8% (95% CI, 58.9%–84.7%). Lesions missed in CECT + CTE were gastrointestinal (n = 14), lymph nodes (n = 25), mesenteric (n = 1), and pancreatic (n = 7), whereas corresponding numbers for PET/CT were 14, 5, 3, and 2. Contrast-enhanced CT + CTE showed more false-positives (n = 26) than PET/CT (n = 9). Lesions missed by CECT + CTE were smaller than detected lesions (median, 9.7 mm [interquartile range, 7.5–31.1] vs 17.7 mm [interquartile range, 12.2–30.0]; P = 0.062), and lesions missed by PET had significantly lower tumor/background (liver) SUVmax ratio (median, 1.3 [interquartile range, 0.6–3.8] vs 4.7 [interquartile range, 2.7–10.8]). The ratio of true-positives to false-positives dropped markedly, when reporting confidence in CECT + CTE was low (4/15 [for rating 1 or 2] vs 93/11 [rating 3]). Corresponding numbers for PET/CT were (40/7 [for rating 1 or 2] vs 80/2 [rating 3]). Combination of these 2 modalities would have increased the lesion-wise sensitivities in patients with unknown primaries to 89.7% (95% CI, 73.6%–96.4%) and the confidence rating of soft tissue lesions to predominantly high (134 lesions rated 3, and 10 rated 1 or 2).
Conclusions
PET/CT is a sensitive modality for staging and restaging well-differentiated NETs. Use of CECT + CTE as a complementary modality in patients with uncertain uptake or high clinical suspicion of gastroenteropancreatic NETs should be considered, as it improves the lesion detection and reporting confidence.

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https://journals.lww.com/nuclearmed/Fulltext/2020/11000/Comparison_of_Contrast_Enhanced_CT___CT.2.aspx

68Ga-FAPI and 18F-FDG PET/CT Images in a Patient With Extrapulmonary Tuberculosis Mimicking Malignant Tumor

imageExtrapulmonary tuberculosis (TB) is difficult to diagnose. Here, we report a case of extrapulmonary TB in a 68-year-old woman presented with mental fatigue, poor appetite, and weight loss. 18F-FDG PET/CT revealed elevated 18F-FDG uptake in the left inferior cervical, left supraclavicular, mediastinal, and splenic hilum lymph nodes and spleen, which were suspected of malignant tumor. To further differentiate benign and malignant diseases, 68Ga-FAPI PET/CT was performed. 68Ga-FAPI PET/CT also showed intense 68Ga-FAPI uptake in the previously mentioned FDG-avid lesions. However, biopsy of the left supraclavicular lymph node demonstrated the presence of TB.

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https://journals.lww.com/nuclearmed/Fulltext/2020/11000/68Ga_FAPI_and_18F_FDG_PET_CT_Images_in_a_Patient.6.aspx