Nuclear Medicine and Molecular Imaging最新文献

Molecular imaging is an important tool for evaluating patients with prostate cancer, including those with hybrid histopathology. Although rare, mixed small neuroendocrine tumor/acinar adenocarcinoma exhibit aggressive behavior that necessitates optimal therapy. Molecular imaging has been implemented previously to assess radioligand therapy eligibility in such cases. Interestingly, the uptake of radiotracers targeting prostate-specific membrane antigen (PSMA) and somatostatin receptor may be reduced and can potentially lead to false negative readings in certain tumor types with hybrid features. Therefore, physicians should be aware of different kinds of disparities when assessing these tumor types with the aforementioned modalities.

Radiotheranostics with ¹⁷⁷Lu-PSMA have changed the treatment paradigm in patients with prostate cancer, becoming the new standard in certain settings. Terbium-161 (¹⁶¹Tb) has been recently investigated as a potential radionuclide for radiotheranostics in various types of cancer, including metastatic castration-resistant prostate cancer (mCRPC). The nuclear medicine team at King Hussein Cancer Center (KHCC) in Amman, Jordan, recently published the first-in-human SPECT/CT imaging results following a well-tolerated dose of ¹⁶¹Tb-PSMA radioligand therapy with no treatment-related adverse events, adding to the potential of radiotheranostics in prostate cancer. Two clinical trials for ¹⁶¹Tb-PSMA radioligand therapy in prostate cancer are currently underway and will provide valuable insights. This review will shed light on the expanding field of radiotheranostics in prostate cancer, which is not without challenges, and will discuss how the introduction of a new therapeutic option like ¹⁶¹Tb-PSMA may help to combat these challenges and build on the proven success of ¹⁷⁷Lu-PSMA-based radiotheranostics for the benefit of prostate cancer patients worldwide.

Purpose: Integrin α_v is a key regulator in the pathophysiology of hepatic fibrosis. In this study, we evaluated the potential utility of an integrin α_vβ₃ positron emission tomography (PET) radiotracer, ¹⁸F-labeled cyclic arginine-glycine-aspartic acid penta-peptide ([¹⁸F]F-FPP-RGD₂), for detecting hepatic integrin α_v and function in nonalcoholic steatohepatitis (NASH) model rats using integrin α_v siRNA.

Methods: NASH model rats were produced by feeding a choline-deficient, low-methionine, high-fat diet for 8 weeks. PET/computerized tomography imaging and quantification of integrin α_v protein, serum aspartate aminotransferase, and alanine aminotransferase were performed 1 week after single intravenous injection of integrin α_v siRNA.

Results: Integrin α_v siRNA (0.1 and 0.5 mg/kg) dose-dependently decreased hepatic integrin α_v protein concentrations in control and NASH model rats. The hepatic mean standard uptake value of [¹⁸F]F-FPP-RGD₂ was decreased dose-dependently by integrin α_v siRNA. The mean standard uptake value was positively correlated with integrin α_v protein levels in control and NASH model rats. Serum aspartate aminotransferase and alanine aminotransferase concentrations were also decreased by siRNA injection and correlated with liver integrin α_v protein expression levels in NASH model rats.

Conclusion: This study suggests that [¹⁸F]F-FPP-RGD₂ PET imaging is a promising radiotracer for monitoring hepatic integrin α_v protein levels and hepatic function in NASH pathology.

Neuroendocrine tumors (NETs) up to 80% may have metastatic disease to lymph nodes, liver, and bones upon diagnosis due to their indolent course and benign nature. However, metastasis to the breast from gastropancreatic-neuroendocrine tumors (GEP-NETs) is unusual and rarely reported. Furthermore, such metastases may mimic a primary breast carcinoma clinically and radiologically. This case report illustrates an unusual presentation of metastasis to the right breast in addition to liver, pancreas, and lymph nodal metastases in a patient with ileal NET who was operated upon 5 years back. The metastases were detected by somatostatin receptor-based imaging and post-therapy scan which was confirmed by cytology and immunocytochemistry.

Purpose: In PET/CT imaging, the activity of the ¹⁸F-FDG activity is injected either based on patient body weight (BW) or body mass index (BMI). The purpose of this study was to optimise BMI-based whole body ¹⁸F-FDG PET images obtained from overweight and obese patients and assess their image quality, quantitative value and radiation dose in comparison to BW-based images.

Methods: The NEMA-IEC-body phantom was scanned using the mCT 128-slice scanner. The spheres and background were filed with F-18 activity. Spheres-to-background ratio was 4:1. Data was reconstructed using the OSEM-TOF-PSF routine reconstruction. The optimization was performed by varying number of iterations and subsets, filter's size and type, and matrix size. The optimized reconstruction was applied to 17 patients' datasets. The optimized BMI-, routine BMI- and the BW-based images were compared visually and using contrast-to-noise ratio (CNR) and standardized uptake values (SUV) measurements.

Results: The visual assessment of the optimized phantom images showed better image quality and contrast-recovery-coefficients (CRCs) values compared to the routine reconstruction. Using patient data, the optimized BMI-based images provided better image quality compared to BW-based images in 87.5% of the overweight cases and 66.7% for obese cases. The optimized BMI-based images resulted in more than 50% reduction of radiation dose. No significant differences were found between the three series of images in SUV measurements.

Conclusion: The optimized BMI-based approach using 1 iteration, 21 subsets, and 3 mm Hamming filter improves image quality, reduces radiation dose, and provides, at least, similar quantification compared to the BW-based approach for overweight and obese patients.

Prostate-specific membrane antigen (PSMA) is a type II transmembrane glycoprotein and is expressed in multiple solid malignant neoplasms. We presented a case of a prostate cancer patient who went through Tc-99 m PSMA SPECT, and multifocal increased radiotracer uptake in the thyroid gland was demonstrated. Despite negative FNA results for malignancy, post-operative histopathologic examination illustrated papillary thyroid carcinoma.

Purpose: This study is to use a simple algorithm based on patient's age to reduce the overall biological detriment associated with PET/CT.

Materials and methods: A total of 421 consecutive patients (mean age 64 ± 14 years) undergoing PET for various clinical indications were enrolled. For each scan, effective dose (ED in mSv) and additional cancer risk (ACR) were computed both in a reference condition (REF) and after applying an original algorithm (ALGO). The ALGO modified the mean dose of FDG and the PET scan time parameters; indeed, a lower dose and a longer scan time were reported in the younger, while a higher dose and a shorter scan time in the older patients. Moreover, patients were classified by age bracket (18-29, 30-60, and 61-90 years).

Results: The ED was 4.57 ± 0.92 mSv in the REF condition. The ACR were 0.020 ± 0.016 and 0.0187 ± 0.013, respectively, in REF and ALGO. The ACR for the REF and ALGO conditions were significantly reduced in males and females, although it was more evident in the latter gender (all p < 0.0001). Finally, the ACR significantly reduced from the REF condition to ALGO in all three age brackets (all p < 0.0001).

Conclusion: Implementation of ALGO protocols in PET can reduce the overall ACR, mainly in young and female patients.

Purpose: ¹²³I-metaiodobenzylguanidine (MIBG) cardiac scintigraphy was a useful imaging modality for the diagnosis of Parkinson's disease, but its diagnostic performances were variably reported. This retrospective study compared the diagnostic performances and investigated the optimal imaging protocol of ¹²³I-MIBG cardiac scintigraphy at various imaging time points in patients suspected of Parkinson's disease in clinical practice.

Methods: In patients suspected of Parkinson's disease, clinical records, autonomic function tests, and ¹²³I-MIBG cardiac scintigraphy were retrospectively reviewed. Semi-quantitative parameters such as heart-to-mediastinum ratio (HMR) and washout rate (WR) were calculated and compared at 15 min, 1 h, 2 h, 3 h, and 4 h post-injection (p.i.). of ¹²³I-MIBG cardiac scintigraphy. Group A consisted of Parkinson's disease (PD), Parkinson's disease dementia (PDD), and dementia with Lewy body (DLB), and group B consisted of non-Parkinson's diseases such as multiple system atrophy (MSA), progressive supranuclear palsy (PSP), drug-induced parkinsonism (DIP), essential tremor (ET), Parkinson-plus syndrome (PPS), and unspecified secondary parkinsonism (NA). The diagnostic performances of HMR and WR were compared for differentiation of group A from group B, and their clinical usefulness and optimal imaging time points were explored.

Results: Seventy-eight patients were included in group A (67 PD, 7 PDD, 4 DLB), and 18 patients were included in group B (5 MSA, 3 PSP, 2 DIP, 2 ET, 1 PPS, and 1 NA). Sensitivity, specificity, accuracy, positive predictive value (PPV), and negative predictive value of HMR and WR were maximized at 4 h p.i., (82.1%, 85.7%, 82.6%, 97.0%, and 46.2%; cutoff threshold < 1.717; area under curve 0.8086) and at the time interval between 1 and 4 h p.i. (65.4%, 85.7%, 68.5%, 96.2%, and 30.8%; cutoff threshold > 24.1%; area under curve 0.8246), respectively, and PPVs of both HMR and WR persistently showed greater than 92.7% at earlier time points and shorter time intervals.

Conclusion: This study reassured that 4-h-delayed imaging is recommended for the best diagnostic performances in ¹²³I-MIBG cardiac scintigraphy. Although it showed suboptimal diagnostic performances to differentiate PD, PDD, and DLB from non-Parkinson's diseases, it can be useful as an auxiliary measure for the differential diagnosis in usual clinical practice.

Supplementary information: The online version contains supplementary material available at 10.1007/s13139-023-00790-w.