Search Results (9)

Background: [⁶⁸Ga]Ga-FAPI PET/CT demonstrates high sensitivity for tumor detection but limited specificity because benign fibro-inflammatory conditions may also show tracer uptake. Dual-time-point imaging has been proposed to improve lesion characterization by assessing temporal changes in uptake. This study evaluated whether delayed imaging provides incremental diagnostic value over standard early imaging. Methods: This retrospective lesion-based study evaluated dual-time-point [⁶⁸Ga]Ga-FAPI PET/CT imaging. SUVmax, maximal tumor-to-background ratio (TBRmax), metabolic tumor volume (MTV), and total lesion uptake (TLU) were measured on early and delayed scans. Diagnostic performance for differentiating malignant from benign uptake findings was assessed using receiver operating characteristic analysis. Results: A total of 123 patients underwent dual-time-point imaging at approximately 26 and 65 min post-injection. Overall, 620 [⁶⁸Ga]Ga-FAPI uptake findings were analyzed, including 307 malignant uptake findings and 313 benign findings. SUVmax decreased significantly over time in both malignant and benign uptake findings, with a greater decline in benign findings (%ΔSUVmax −7.7% vs. −3.6%, p = 0.0045). TBRmax increased modestly in malignant uptake findings, while MTV and TLU remained largely stable. SUVmax and TBRmax were significantly higher in malignant uptake at both imaging time points; however, diagnostic performance remained moderate (AUCs of 0.65–0.69) due to substantial overlap between lesion types. Delayed imaging did not improve diagnostic accuracy compared with early imaging, and delta parameters demonstrated poor performance (AUC ~0.5). Similar findings were observed across tumor subgroups. Conclusions: In this lesion-based retrospective cohort, delayed dual-time-point [⁶⁸Ga]Ga-FAPI PET/CT did not demonstrate meaningful incremental diagnostic value over early imaging. A standard early acquisition appears adequate for routine practice, although lesion interpretation remains dependent on clinical, morphologic, and, when needed, histopathologic correlation. Full article

Background/Objectives: 18F-fluorocholine is a positron emission tomography (PET) tracer earlier found to be a marker of macrophage content in carotid plaques. We aimed to assess the feasibility of 18F-choline PET-MRI to non-invasively localize vulnerable coronary plaques, using optical coherence tomography (OCT) as a reference standard. Methods: Patients with recent myocardial infarction who were scheduled for a secondary angiography of a non-culprit vessel underwent 18F-fluorocholine coronary PET-MRI. Subsequently, OCT was performed during the secondary angiography. Maximum target-to-background (TBRmax) values of 18F-fluorocholine uptake were determined in two vessel sections that contained either vulnerable or stable plaques as defined by OCT. The OCT-based definition of a vulnerable plaque was a fibrous cap thickness < 70 µm. To enhance the detectability of coronary plaques using PET, three different motion-correction strategies were used: multigate respiratory gating motion correction (MRG-MOCO), extended MR-based motion correction (eMR-MOCO), and extended MR-based motion correction with ECG gating (eMR-MOCO-ECG). Results: Fifteen patients were included in this study. One patient needed to be excluded due to extravasation of the tracer. In another patient, no region with only a stable plaque could be identified. TBRmax values were as follows for three different reconstructions in vulnerable versus stable plaques: MRG-MOCO: mean TBRmax 1.45 vs. 1.35, p = 0.52 (n = 13); eMR-MOCO: mean TBRmax 1.47 vs. 1.27, p = 0.26 (n = 11); eMR-MOCO-ECG: mean TBRmax 1.49 vs. 1.26, p = 0.21 (n = 11). Conclusions: 18F-fluorocholine uptake in vulnerable atherosclerotic plaques in coronary arteries was not significantly different from uptake in stable plaques, even though advanced motion-correction methods were applied. That may be caused by multiple factors, such as small coronary plaque size, tracer biology, or remaining cardiac motion. Full article

Background: Amino acid tracer positron emission tomography–magnetic resonance imaging (PET-MRI) was shown to be superior to MRI alone for evaluating central nervous system (CNS) tumours in adults. This study aimed to investigate the utility of amino acid PET-MRI in children with CNS tumours. Methods: We reviewed the amino acid PET-MRI findings of children with suspected or confirmed CNS neoplasms managed in a territory-wide referral centre in Hong Kong from 2022 to 2025. Maximal standardized uptake values (SUVmax) were captured, and tumour-to-background SUVmax ratios (TBRmax) were measured with reference to adjacent or contralateral normal brain structures. Comparisons were made among patients with clinical high-grade and low-grade/non-neoplastic lesions. Results: Thirty-seven patients were included, with 63 PET-MRIs performed. PET-MRI was performed as part of initial diagnostics in 41% of the cases, for response assessment in 48%, and evaluation of residual/relapsed disease in 11%. High-grade lesions had a significantly higher SUVmax and TBRmax compared to low-grade/non-malignant lesions (median SUVmax 3.7 vs. 1.6, p = 0.00006; median TBRmax 2.06 vs. 0.91, p = 0.00002). Optimal SUVmax and TBRmax cut-offs by ROC analysis were 2.38 and 1.62, respectively. Similar performance was reproduced by focusing on the subset of patients with suspected CNS germ cell tumours (CNS-GCT). The impact of amino acid PET availability is considerable, as clinical management was modified in 65% of patients. Conclusions: Our study demonstrates the performance and clinical utility of amino acid PET-MRI in the management of children with CNS pathologies. Amino acid PET-MRI contributes to the diagnosis, monitoring, and treatment guidance of these patients, providing crucial information for decision-making. Full article

Introduction: There is a pressing demand for the development of cancer-specific diagnostic imaging tools, particularly for staging of pancreatic-, gastric- or cholangiocarcinoma, as current diagnostic imaging techniques, including CT, MRI and PET using FDG, are not fully adequate. The novel PET-tracer “FAPI” has the potential to visualize even small tumour deposits employing the tumour-specific expression of fibroblast-activating protein (FAP) in malignant cells. Methods: We performed a systematic review to select studies investigating the use of FAPI PET for staging pancreatic-, gastric- and cholangiocarcinoma (PROSPERO CRD42022329512). Patient-wise and lesion-wise comparisons were performed for primary tumour (T), lymph nodes (N), organ metastases (M) and peritoneal carcinomatosis (PC). Maximum standardized uptake values (SUVmax) and tumour-to-background ratios (TBR) were compared between PET using FAPI versus FDG (if reported). Results: Ten articles met the inclusion criteria. In all studies, FAPI PET showed superiority over FDG-PET/CT/MRI for the detection of T, N, M and PC, both in the patient-wise and in lesion-wise comparisons (when performed). Additionally, higher SUVmax and TBRmax values were reported for use of FAPI compared to FDG. Conclusions: The positive results of this review warrant prospective clinical studies to investigate the accuracy and clinical value of FAPI PET for diagnosing and staging patients with pancreatic-, gastric- and cholangiocarcinoma. Full article

The purpose of this study was to assess organ dosimetry and clinical use of [¹²⁴I]I-NM404, a radiotheranostic alkylphosphocholine (APC) analog, for accurate detection and characterization of a wide variety of solid primary and metastatic malignancies anywhere in the body. Methods: Patterns of [¹²⁴I]I-NM404 uptake were quantitatively analyzed and qualitatively compared with [¹⁸F]FDG PET/CT in 14 patients (median age, 61.5 years; 7 males, 7 females) with refractory metastatic cancer who were enrolled in one of two Phase I imaging studies. Primary cancer types included bronchogenic (n = 7), colorectal (n = 1), prostate (n = 1), triple-negative breast (n = 1), head and neck (n = 2), pancreatic (n = 1) carcinoma, and melanoma (n = 1). Patients were administered [¹²⁴I]I-NM404 and imaged via PET/CT at 1–2, 4–6, 24, and 48 h and at 5–10 days post injection, from top of the skull to mid-thigh. Volumes of interest were drawn over lungs, heart, liver, kidneys, and whole body for dosimetry estimation using OLINDA 1.1 Representative metastatic index lesions were chosen when applicable for each case with active sites of disease to calculate maximum and mean tumor-to-background ratios (TBRmax, TBRmean), using the adjacent normal organ parenchyma as background when possible. Results: Administrations of [¹²⁴I]-NM404 were safe and well-tolerated. The organs with the highest estimated absorbed dose (mean ± SD) were the lungs (1.74 ± 0.39 mSv/MBq), heart wall (1.52 ± 0.29 mSv/MBq), liver (1.28 ± 0.21 mSv/MBq) and kidneys (1.09 ± 0.20 mSv/MBq). The effective dose was 0.77 ± 0.05 mSv/MBq. Preferential uptake within metastatic foci was observed with all cancer subtypes, TBRmax ranged from 1.95 to 15.36 and TBRmean ranged from 1.63 to 6.63. Robust sensitive imaging of lesions was enhanced by delayed timing (2–6 days after single injection of [¹²⁴I]I-NM404, respectively) due to persistent tumor retention coupled with progressive washout of background activity. NM404 uptake was evident in pulmonary, nodal, skeletal, CNS, and other metastatic sites of disease. Radiation related injury or necrosis were NM404 negative, whereas certain small number of metastatic brain lesions were false negative for NM404. Conclusions: In addition to being well tolerated, selective tumor uptake of NM404 with prolonged retention was demonstrated within a broad spectrum of highly treated metastatic cancers. Full article

The 18 kDa translocator protein (TSPO) is increasingly recognized as an interesting target for the imaging of glioblastoma (GBM). Here, we investigated TSPO PET imaging and autoradiography in the frequently used GL261 glioblastoma mouse model and aimed to generate insights into the temporal evolution of TSPO radioligand uptake in glioblastoma in a preclinical setting. We performed a longitudinal [¹⁸F]GE-180 PET imaging study from day 4 to 14 post inoculation in the orthotopic syngeneic GL261 GBM mouse model (n = 21 GBM mice, n = 3 sham mice). Contrast-enhanced computed tomography (CT) was performed at the day of the final PET scan (±1 day). [¹⁸F]GE-180 autoradiography was performed on day 7, 11 and 14 (ex vivo: n = 13 GBM mice, n = 1 sham mouse; in vitro: n = 21 GBM mice; n = 2 sham mice). Brain sections were also used for hematoxylin and eosin (H&E) staining and TSPO immunohistochemistry. [¹⁸F]GE-180 uptake in PET was elevated at the site of inoculation in GBM mice as compared to sham mice at day 11 and later (at day 14, TBR_max +27% compared to sham mice, p = 0.001). In GBM mice, [¹⁸F]GE-180 uptake continuously increased over time, e.g., at day 11, mean TBR_max +16% compared to day 4, p = 0.011. [¹⁸F]GE-180 uptake as depicted by PET was in all mice co-localized with contrast-enhancement in CT and tissue-based findings. [¹⁸F]GE-180 ex vivo and in vitro autoradiography showed highly congruent tracer distribution (r = 0.99, n = 13, p < 0.001). In conclusion, [¹⁸F]GE-180 PET imaging facilitates non-invasive in vivo monitoring of TSPO expression in the GL261 GBM mouse model. [¹⁸F]GE-180 in vitro autoradiography is a convenient surrogate for ex vivo autoradiography, allowing for straightforward identification of suitable models and scan time-points on previously generated tissue sections. Full article

Currently, a reliable diagnostic test for differentiating pseudoprogression from early tumor progression is lacking. We explored the potential of O-(2-[¹⁸F]fluoroethyl)-L-tyrosine (FET) positron emission tomography (PET) radiomics for this clinically important task. Thirty-four patients (isocitrate dehydrogenase (IDH)-wildtype glioblastoma, 94%) with progressive magnetic resonance imaging (MRI) changes according to the Response Assessment in Neuro-Oncology (RANO) criteria within the first 12 weeks after completing temozolomide chemoradiation underwent a dynamic FET PET scan. Static and dynamic FET PET parameters were calculated. For radiomics analysis, the number of datasets was increased to 102 using data augmentation. After randomly assigning patients to a training and test dataset, 944 features were calculated on unfiltered and filtered images. The number of features for model generation was limited to four to avoid data overfitting. Eighteen patients were diagnosed with early tumor progression, and 16 patients had pseudoprogression. The FET PET radiomics model correctly diagnosed pseudoprogression in all test cohort patients (sensitivity, 100%; negative predictive value, 100%). In contrast, the diagnostic performance of the best FET PET parameter (TBR_max) was lower (sensitivity, 81%; negative predictive value, 80%). The results suggest that FET PET radiomics helps diagnose patients with pseudoprogression with a high diagnostic performance. Given the clinical significance, further studies are warranted. Full article

Pseudoprogression (PSP) detection in glioblastoma remains challenging and has important clinical implications. We investigated the potential of machine learning (ML) in improving the performance of PET using O-(2-[¹⁸F]-fluoroethyl)-L-tyrosine (FET) for differentiation of tumor progression from PSP in IDH-wildtype glioblastoma. We retrospectively evaluated the PET data of patients with newly diagnosed IDH-wildtype glioblastoma following chemoradiation. Contrast-enhanced MRI suspected PSP/TP and all patients underwent subsequently an additional dynamic FET-PET scan. The modified Response Assessment in Neuro-Oncology (RANO) criteria served to diagnose PSP. We trained a Linear Discriminant Analysis (LDA)-based classifier using FET-PET derived features on a hold-out validation set. The results of the ML model were compared with a conventional FET-PET analysis using the receiver-operating-characteristic (ROC) curve. Of the 44 patients included in this preliminary study, 14 patients were diagnosed with PSP. The mean (TBRmean) and maximum tumor-to-brain ratios (TBRmax) were significantly higher in the TP group as compared to the PSP group (p = 0.014 and p = 0.033, respectively). The area under the ROC curve (AUC) for TBRmax and TBRmean was 0.68 and 0.74, respectively. Using the LDA-based algorithm, the AUC (0.93) was significantly higher than the AUC for TBRmax. This preliminary study shows that in IDH-wildtype glioblastoma, ML-based PSP detection leads to better diagnostic performance. Full article

This study aimed to explore the correlation between imaging patterns and clinical features in patients with smoldering multiple myeloma (SMM) who simultaneously underwent 18F-FDG, 11C-Methionine, and 68Ga-Pentixafor positron emission tomography/computed tomography (PET/CT). We retrieved and analyzed clinical characteristics and PET imaging data of 10 patients with SMM. We found a significant correlation between bone marrow (BM) plasma cell (PC) infiltration and mean standardized uptake values (SUV_mean) of lumbar vertebrae L2-L4 on 11C-Methionine PET/CT scans (r = 0.676, p = 0.031) and 68Ga-Pentixafor PET/CT scans (r = 0.839, p = 0.002). However, there was no significant correlation between BM involvement and SUV_mean of lumbar vertebrae L2-L4 on 18F-FDG PET/CT scans (r = 0.558, p = 0.093). Similarly, mean target-to-background ratios (TBR_mean) of lumbar vertebrae L2-L4 also correlated with bone marrow plasma cell (BMPC) infiltration in 11C-Methionine PET/CT (r = 0.789, p = 0.007) and 68Ga-Pentixafor PET/CT (r = 0.724, p = 0.018) PET/CT. In contrast, we did not observe a significant correlation between BMPC infiltration rate and TBR_mean in 18F-FDG PET/CT (r = 0.355, p = 0.313). Additionally, on 11C-Methionine PET/CT scans, we found a significant correlation between BMPC infiltration and TBR_max of lumbar vertebrae L2-L4 (r = 0.642, p = 0.045). In conclusion, 11C-Methionine and 68Ga-Pentixafor PET/CT demonstrate higher sensitivity than 18F-FDG PET/CT in detecting BM involvement in SMM. Full article