Journal of Nuclear Medicine最新文献

Kirsten rat sarcoma (KRAS) mutations are an important marker for tumor-targeted therapy. In this study, we sought to develop a KRAS^G12C oncoprotein-targeted PET tracer and to evaluate its translational potential for noninvasive imaging of the KRAS^G12C mutation in non-small cell lung cancer (NSCLC) and colorectal cancer (CRC) patients. Methods: [¹⁸F]PFPMD was synthesized on the basis of AMG510 (sotorasib) by attaching a polyethylene glycol chain to the quinazolinone structure. The binding selectivity and imaging potential of [¹⁸F]PFPMD were verified by cellular uptake, internalization, and blocking (H358: KRAS^G12C mutation; A549: non-KRAS^G12C mutation) studies, as well as by a small-animal PET/CT imaging study on tumor-bearing mice. Five healthy volunteers were enrolled to assess the safety, biodistribution, and dosimetry of [¹⁸F]PFPMD. Subsequently, 14 NSCLC or CRC patients with or without the KRAS^G12C mutation underwent [¹⁸F]PFPMD and [¹⁸F]FDG PET/CT imaging. The SUV_max of tumor uptake of [¹⁸F]PFPMD was measured and compared between patients with and without the KRAS^G12C mutation. Results: [¹⁸F]PFPMD was obtained with a high radiochemical yield, radiochemical purity, and stability. The protein-binding assay showed that [¹⁸F]PFPMD selectively binds to the KRAS^G12C protein. [¹⁸F]PFPMD uptake was significantly higher in H358 than in A549 and was decreased by pretreatment with AMG510 (H358 vs. A549: 3.22% ± 0.28% vs. 2.50% ± 0.25%, P < 0.05; block: 2.06% ± 0.13%, P < 0.01). Similar results were observed in tumor-bearing mice on PET imaging (H358 vs. A549: 3.93% ± 0.24% vs. 2.47% ± 0.26% injected dose/g, P < 0.01; block: 2.89% ± 0.29% injected dose/g; P < 0.05). [¹⁸F]PFPMD was safe in humans and was excreted primarily by the gallbladder and intestines. The whole-body effective dose was comparable to that of [¹⁸F]FDG. The accumulation of [¹⁸F]PFPMD in KRAS^G12C mutation tumors was significantly higher than that in non-KRAS^G12C mutation tumors (SUV_max: 3.73 ± 0.58 vs. 2.39 ± 0.22, P < 0.01) in NSCLC and CRC patients. Conclusion: [¹⁸F]PFPMD is a safe and promising PET tracer for noninvasive screening of the KRAS^G12C mutation status in NSCLC and CRC patients.

The development of artificial intelligence (AI) within nuclear imaging involves several ethically fraught components at different stages of the machine learning pipeline, including during data collection, model training and validation, and clinical use. Drawing on the traditional principles of medical and research ethics, and highlighting the need to ensure health justice, the AI task force of the Society of Nuclear Medicine and Molecular Imaging has identified 4 major ethical risks: privacy of data subjects, data quality and model efficacy, fairness toward marginalized populations, and transparency of clinical performance. We provide preliminary recommendations to developers of AI-driven medical devices for mitigating the impact of these risks on patients and populations.

Since the development of fibroblast activation protein-targeted radiopharmaceuticals, ⁶⁸Ga-fibroblast activation protein inhibitor (FAPI) PET/CT has been found to be suitable for detecting primary and metastatic lesions in many types of tumors. However, there is currently a lack of reliable data regarding the clinical impact of this family of probes. To address this gap, the present study aimed to analyze the clinical impact of ⁶⁸Ga-FAPI PET/CT by examining a large cohort of patients with various tumors. Methods: In total, 226 patients (137 male and 89 female) were included in this retrospective analysis. Pancreatic cancer and head and neck cancers were the most common tumor types in this cohort. TNM stage and oncologic management were initially determined with gold standard imaging, and these results were compared with ⁶⁸Ga-FAPI PET/CT. Changes were classified as major and minor. Results: For 42% of all patients, TNM stage was changed by ⁶⁸Ga-FAPI PET/CT results. Most of these changes resulted in upstaging. A change in clinical management occurred in 117 of 226 patients. Although a major change in management occurred in only 12% of patients, there was a significant improvement in the ability to accurately plan radiation therapy. In general, the highest clinical impact of ⁶⁸Ga-FAPI PET/CT imaging was found in patients with lung cancer, pancreatic cancer, and head and neck tumors. Conclusion: ⁶⁸Ga-FAPI PET/CT is a promising imaging probe that has a significant impact on TNM stage and clinical management. ⁶⁸Ga-FAPI PET/CT promises to be a crucial new technology that will improve on conventional radiologic imaging methods such as contrast-enhanced CT and contrast-enhanced MRI typically acquired for cancer staging.

²⁰³Pb is a surrogate imaging match for ²¹²Pb. This elementally matched pair is emerging as a suitable pair for imaging and targeted radionuclide therapy in cancer care. Because of the half-life (51.9 h) and low-energy γ-rays emitted, ²⁰³Pb is suitable for the development of diagnostic radiopharmaceuticals. The aim of this work was to optimize the production and separation of high-specific-activity ²⁰³Pb using electroplated thallium targets. We further investigated the radiochemistry optimization using a suitable chelator, tetraazacyclododecane-1,4,7-triacetic acid (DO3A), and targeting vector, VMT-α-NET (lead-specific chelator conjugated to tyr3-octreotide via a polyethylene glycol linker). Methods: Targets were prepared by electroplating of natural or enriched (²⁰⁵Tl) thallium metal. Scanning electron microscopy was performed to determine the structure and elemental composition of electroplated targets. Targets were irradiated with 24-MeV protons with varying current and beam time to investigate target durability. ²⁰³Pb was purified from the thallium target material using an extraction resin (lead resin) column followed by a second column using a weak cation-exchange resin to elute the lead isotope as [²⁰³Pb]PbCl₂ Inductively coupled plasma mass spectrometry studies were used to further characterize the separation for trace metal contaminants. Radiolabeling efficiency was also investigated for DO3A chelator and VMT-α-NET (a peptide-based targeting conjugate). Results: Electroplated targets were prepared at a high plating density of 76-114 mg/cm² using a plating time of 5 h. A reproducible separation method was established with a final elution in HCl (400 μL, 1 M) suitable for radiolabeling. Greater than 90% recovery yields were achieved, with an average specific activity of 37.7 ± 5.4 GBq/μmol (1.1 ± 0.1 Ci/μmol). Conclusion: An efficient electroplating method was developed to prepare thallium targets suitable for cyclotron irradiation. A simple and fast separation method was developed for routine ²⁰³Pb production with high recovery yields and purity.

A single-institution prospective pilot clinical trial was performed to demonstrate the feasibility of combining [¹⁷⁷Lu]Lu-PSMA-617 radiopharmaceutical therapy (RPT) with stereotactic body radiotherapy (SBRT) for the treatment of oligometastatic castration-sensitive prostate cancer. Methods: Six patients with 9 prostate-specific membrane antigen (PSMA)-positive oligometastases received 2 cycles of [¹⁷⁷Lu]Lu-PSMA-617 RPT followed by SBRT. After the first intravenous infusion of [¹⁷⁷Lu]Lu-PSMA-617 (7.46 ± 0.15 GBq), patients underwent SPECT/CT at 3.2 ± 0.5, 23.9 ± 0.4, and 87.4 ± 12.0 h. Voxel-based dosimetry was performed with calibration factors (11.7 counts per second/MBq) and recovery coefficients derived from in-house phantom experiments. Lesions were segmented on baseline PSMA PET/CT (50% SUV_max). After a second cycle of [¹⁷⁷Lu]Lu-PSMA-617 (44 ± 3 d; 7.50 ± 0.10 GBq) and an interim PSMA PET/CT scan, SBRT (27 Gy in 3 fractions) was delivered to all PSMA-avid oligometastatic sites, followed by post-PSMA PET/CT. RPT and SBRT voxelwise dose maps were scaled (α/β = 3 Gy; repair half-time, 1.5 h) to calculate the biologically effective dose (BED). Results: All patients completed the combination therapy without complications. No grade 3+ toxicities were noted. The median of the lesion SUV_max as measured on PSMA PET was 16.8 (interquartile range [IQR], 11.6) (baseline), 6.2 (IQR, 2.7) (interim), and 2.9 (IQR, 1.4) (post). PET-derived lesion volumes were 0.4-1.7 cm³ The median lesion-absorbed dose (AD) from the first cycle of [¹⁷⁷Lu]Lu-PSMA-617 RPT (AD_RPT) was 27.7 Gy (range, 8.3-58.2 Gy; corresponding to 3.7 Gy/GBq, range, 1.1-7.7 Gy/GBq), whereas the median lesion AD from SBRT was 28.1 Gy (range, 26.7-28.8 Gy). Spearman rank correlation, ρ, was 0.90 between the baseline lesion PET SUV_max and SPECT SUV_max (P = 0.005), 0.74 (P = 0.046) between the baseline PET SUV_max and the lesion AD_RPT, and -0.81 (P = 0.022) between the lesion AD_RPT and the percent change in PET SUV_max (baseline to interim). The median for the lesion BED from RPT and SBRT was 159 Gy (range, 124-219 Gy). ρ between the BED from RPT and SBRT and the percent change in PET SUV_max (baseline to post) was -0.88 (P = 0.007). Two cycles of [¹⁷⁷Lu]Lu-PSMA-617 RPT contributed approximately 40% to the maximum BED from RPT and SBRT. Conclusion: Lesional dosimetry in patients with oligometastatic castration-sensitive prostate cancer undergoing [¹⁷⁷Lu]Lu-PSMA-617 RPT followed by SBRT is feasible. Combined RPT and SBRT may provide an efficient method to maximize the delivery of meaningful doses to oligometastatic disease while addressing potential microscopic disease reservoirs and limiting the dose exposure to normal tissues.

Molecular markers are of increasing importance for classifying, treating, and determining the prognosis for central nervous system tumors. Isocitrate dehydrogenase (IDH) is a critical regulator of glucose and amino acid metabolism. Our objective was to investigate metabolic reprogramming of glioma using compartmental uptake (CU) characteristics in O-(2-¹⁸F-fluoroethyl)-l-tyrosine (FET) PET and to evaluate its diagnostic potential for IDH genotyping. Methods: Between 2017 and 2022, patients with confirmed glioma were preoperatively investigated using static ¹⁸F-FET PET. Metabolic tumor volume (MTV), MTV for 60%-100% uptake (MTV₆₀), and T2-weighted and contrast-enhancing lesion volumes were automatically segmented using U-Net neural architecture and isocontouring. Volume intersections were determined using the Dice coefficient. Uptake characteristics were determined for metabolically defined compartments (central [80%-100%] and peripheral [60%-75%] areas of ¹⁸F-FET uptake). CU ratio was defined as the fraction between the peripheral and central compartments. Mean target-to-background ratio was calculated. Comparisons were performed using parametric and nonparametric tests. Receiver-operating-characteristic curves, regression, and correlation were used for statistical analysis. Results: In total, 52 participants (male, 27, female, 25; mean age ± SD, 51 ± 16 y) were evaluated. MTV₆₀ was greater and distinct from contrast-enhancing lesion volume (P = 0.046). IDH-mutated tumors presented a greater volumetric CU ratio and SUV CU ratio than IDH wild-type tumors (P < 0.05). Volumetric CU ratio determined IDH genotype with excellent diagnostic performance (area under the curve [AUC], 0.88; P < 0.001) at more than 5.49 (sensitivity, 86%, specificity, 90%), because IDH-mutated tumors presented a greater peripheral metabolic compartment than IDH wild-type tumors (P = 0.045). MTV₆₀ and MTV were not suitable for IDH classification (P > 0.05). SUV CU ratio (AUC, 0.72; P = 0.005) and target-to-background ratio (AUC, 0.68; P = 0.016) achieved modest diagnostic performance-inferior to the volumetric CU ratio. Furthermore, the classification of loss of heterozygosity of chromosomes 1p and 19q (AUC, 0.75; P = 0.019), MGMT promoter methylation (AUC, 0.70; P = 0.011), and ATRX loss (AUC, 0.73; P = 0.004) by amino acid PET was evaluated. Conclusion: We proposed parametric ¹⁸F-FET PET as a noninvasive metabolic biomarker for the evaluation of CU characteristics, which differentiated IDH genotype with excellent diagnostic performance, establishing a critical association between spatial metabolic heterogeneity, mitochondrial tricarboxylic acid cycle, and genomic features with critical implications for clinical management and the diagnostic workup of patients with central nervous system cancer.