A retrospective study of 68Ga-FAPI PET/CT in differentiating the nature of pulmonary lesions.

Purpose: This study aimed to investigate the characteristics of various pulmonary lesions as revealed by 68Ga-FAPI PET/CT and to determine the utility of 68Ga-FAPI PET/CT in distinguishing the nature of these pulmonary lesions. Methods: A retrospective analysis was conducted on 99 patients with pulmonary lesions, who were categorized into three distinct groups: primary lung tumors (G1), metastatic lung tumors (G2), and benign lesions (G3). Each participant underwent a 68Ga-FAPI PET/CT scan. Among these groups, variables such as the Tumor/Background Ratio (TBR), Maximum Standardized Uptake Value (SUVmax), and the true positive rate of the lesions were compared. Furthermore, the FAPI uptake in nodular-like pulmonary lesions (d<3cm) and those with irregular borders was evaluated across the groups. A correlation analysis sought to understand the relationship between FAPI uptake in primary and pulmonary metastatic lesions. Results: The study's participants were composed of 52 males and 47 females, with an average age of 56.8 ± 13.2 years. A higher uptake and detection rate for pulmonary lesions were exhibited by Group G1 compared to the other groups (SUVmax [G1 vs. G2 vs. G3: 9.1 ± 4.1 vs. 6.1 ± 4.1 vs. 5.3 ± 5.8], P<0.05; TBR [G1 vs. G2 vs. G3: 6.2 ± 2.4 vs. 4.1 ± 2.2 vs. 3.2 ± 2.7], P<0.01; true positive rate 95.1% vs. 88% vs. 75.6%]. In nodular-like lung lesions smaller than 3 cm, G1 showed a significantly higher FAPI uptake compared to G2 and G3 (SUVmax [G1 vs. G2 vs. G3: 8.8 ± 4.3 vs. 5.2 ± 3.2 vs. 4.9 ± 6.1], P<0.01; TBR [G1 vs. G2 vs. G3: 5.7 ± 2.7 vs. 3.7 ± 2.1 vs. 3.3 ± 4.4], P<0.05). Both G1 and G2 demonstrated significantly elevated FAPI agent activity in irregular-bordered pulmonary lesions when compared to G3 (SUVmax [G1 vs. G2 vs. G3: 10.9 ± 3.3 vs. 8.5 ± 2.7 vs. 4.6 ± 2.7], P<0.01; TBR [G1 vs. G2 vs. G3: 7.2 ± 2.1 vs. 6.4 ± 1.3 vs. 3.2 ± 2.4], P<0.01). A positive correlation was identified between the level of 68Ga-FAPI uptake in primary lesions and the uptake in pulmonary metastatic lesions within G2 (r=0.856, P<0.05). Conclusion: 68Ga-FAPI PET/CT imaging proves to be of significant value in the evaluation of pulmonary lesions, offering distinctive insights into their nature.

Clinical Value of 68Ga-Pentixafor PET/CT in Subtype Diagnosis of Primary Aldosteronism Patients with Adrenal Micronodules.

Our objective was to investigate the clinical value of 68Ga-pentixafor PET/CT in subtype diagnosis of primary aldosteronism (PA) patients with adrenal micronodules less than 1 cm in diameter and compare it with the routine clinical methods. Methods: We used prospective enrollment of PA patients with adrenal micronodules identified by adrenal CT scans to undergo 68Ga-pentixafor PET/CT. Patients were divided into surgically eligible and ineligible groups based on surgical pathology and postoperative follow-up or adrenal venous sampling (AVS) results. Patient management was discussed by a multidisciplinary team. The semiquantitative parameters of PET/CT included SUVmax for adrenal lesion and SUV ratios for lesion to liver and lesion to normal adrenal gland. Results: In total, 123 PA patients with adrenal micronodules were examined using 68Ga-pentixafor PET/CT, and 104 patients who underwent surgery or successful AVS were included in the analysis (48 ± 10 y old). The sensitivity, specificity, and accuracy of visual analysis using 68Ga-pentixafor PET/CT to identify surgically eligible patients were 90.2%, 72.7%, and 86.5%, respectively, which were significantly higher than those of adrenal CT (73.1%, 53.8%, and 68.3%, respectively) and yielded consistent results in different CT morphologic or age subgroups. In 36 patients who had both AVS and 68Ga-pentixafor PET/CT, the tests showed a 66.7% concordance rate. However, PET/CT was significantly more concordant with surgical outcomes than was AVS in 17 patients who underwent adrenalectomy (82.4% vs. 68.86%). Among the 183 adrenal micronodules included in the study, the semiquantitative diagnostic thresholds for 92 lesions eligible for surgical treatment were an SUVmax of at least 4.55, an SUV ratio of at least 2.17 for lesion to liver, and an SUV ratio of at least 1.90 for lesion to normal adrenal gland. All patients benefited from surgical removal of 68Ga-pentixafor-avid microlesions. Conclusion: In PA patients with adrenal micronodules, 68Ga-pentixafor PET/CT demonstrated promising diagnostic accuracy in classification and appeared to perform better than adrenal CT. Furthermore, there was also a suggestion of some potential in predicting postoperative efficacy compared with AVS, although these observations require further investigation and verification in larger cohorts.

Musculoskeletal pitfalls in 68Ga-PSMA PET/CT.

Prostate-specific membrane antigen (PSMA) is a transmembrane protein expressed in normal prostate cells and overexpressed in prostate cancer. Consequently, it is an important tool in the evaluation of prostate cancer, including the staging of high-risk patients and the assessment of biochemical recurrence. Despite the "specific" designation, benign musculoskeletal conditions, such as fractures, osteodegenerative changes, and fibrous dysplasia, can also show PSMA uptake, which can lead to misinterpretation of the imaging findings. Therefore, radiologists must be aware of these potential pitfalls, understand their causes, and fully analyze their morphologic features on unfused computed tomography (CT) and magnetic resonance imaging scans to correctly interpret the examination. In this pictorial essay, we review the basic characteristics of the 68Ga-PSMA positron-emission tomography/CT (PET/CT) radiotracer, discuss potential causes of false-positive findings on 68Ga-PSMA PET/CT in the musculoskeletal system, and illustrate the corresponding imaging findings.

O antígeno de membrana próstata específico (PSMA) é uma proteína transmembrana que apresenta expressão em células prostáticas normais e superexpressão em neoplasia da próstata. Dessa forma, é uma importante ferramenta na avaliação da neoplasia prostática, de utilidade no estadiamento de pacientes de alto risco e na análise de recorrência bioquímica. Apesar do termo "específico", condições musculoesqueléticas benignas podem demonstrar captação de PSMA, como fraturas, alterações osteodegenerativas e displasia fibrosa, podendo levar a uma avaliação equivocada dos achados de imagem. Assim, o radiologista deve conhecer esses potenciais pitfalls, compreender suas causas e analisar as características morfológicas nas imagens não fundidas de TC e RM para interpretar corretamente o exame. Neste ensaio iconográfico, revisaremos as características básicas do radiofármaco 68Ga-PSMA PET/CT, discutiremos possíveis causas de resultados falso-positivos na 68Ga-PSMA PET/CT no sistema musculoesquelético e ilustraremos os achados de imagem correspondentes.

Musculoskeletal pitfalls in 68Ga-PSMA PET/CT / Pitfalls do sistema musculoesquelético na PET/CT com 68Ga-PSMA

Abstract Prostate-specific membrane antigen (PSMA) is a transmembrane protein expressed in normal prostate cells and overexpressed in prostate cancer. Consequently, it is an important tool in the evaluation of prostate cancer, including the staging of high-risk patients and the assessment of biochemical recurrence. Despite the "specific" designation, benign musculoskeletal conditions, such as fractures, osteodegenerative changes, and fibrous dysplasia, can also show PSMA uptake, which can lead to misinterpretation of the imaging findings. Therefore, radiologists must be aware of these potential pitfalls, understand their causes, and fully analyze their morphologic features on unfused computed tomography (CT) and magnetic resonance imaging scans to correctly interpret the examination. In this pictorial essay, we review the basic characteristics of the 68Ga-PSMA positron-emission tomography/CT (PET/CT) radiotracer, discuss potential causes of false-positive findings on 68Ga-PSMA PET/CT in the musculoskeletal system, and illustrate the corresponding imaging findings.

Resumo O antígeno de membrana próstata específico (PSMA) é uma proteína transmembrana que apresenta expressão em células prostáticas normais e superexpressão em neoplasia da próstata. Dessa forma, é uma importante ferramenta na avaliação da neoplasia prostática, de utilidade no estadiamento de pacientes de alto risco e na análise de recorrência bioquímica. Apesar do termo "específico", condições musculoesqueléticas benignas podem demonstrar captação de PSMA, como fraturas, alterações osteodegenerativas e displasia fibrosa, podendo levar a uma avaliação equivocada dos achados de imagem. Assim, o radiologista deve conhecer esses potenciais pitfalls, compreender suas causas e analisar as características morfológicas nas imagens não fundidas de TC e RM para interpretar corretamente o exame. Neste ensaio iconográfico, revisaremos as características básicas do radiofármaco 68Ga-PSMA PET/CT, discutiremos possíveis causas de resultados falso-positivos na 68Ga-PSMA PET/CT no sistema musculoesquelético e ilustraremos os achados de imagem correspondentes.

68Ga production with cyclotron solid target and automated synthesis of 68Ga labeled drugs / 中华核医学与分子影像杂志

Objective:To produce 68Ga and automatically synthesize 68Ga-labeled drugs based on low-energy medical cyclotron solid target system. Methods:68Zn was electroplated on the surface of the target by electrodeposition. According to the principle of 68Zn(p, n) 68Ga nuclear reaction, 68Zn was irradiated by the 10 MeV medical cyclotron solid target system (30 μA, 30 min) to produce 68Ga, and the activity, nuclear purity, half-life and content of metal impurities of purified product were determined. 68Ga-prostate specific membrane antigen (PSMA)-11 and 68Ga-1, 4, 7, 10-tetraazacyclododecane-1, 4, 7, 10-tetraacetic acid- D-Phe1-Tyr3-Thr8-octreotide (DOTATATE) were synthesized automatically using 68Ga respectively, and the quality control analyses of drug properties, concentration, pH, radiochemical purity, sterility and bacterial endotoxin were carried out. Results:The electroplating mass of 68Zn was (43.71±0.87) mg ( n=35), the yield of 68Ga after irradiation was (10.96±0.67) GBq ( n=35), and the measured half-life was (67.64±0.06) min ( n=7). Only 511 keV energy peak was detected by the gamma spectrometer. After purification, (6.85±0.12) GBq ( n=35) of pure 68Ga was obtained, and the purification efficiency was (62.46±0.96)% (non-attenuated correction, n=35). The metal impurity contents of Zn and Fe were (0.18±0.06) and (1.25±0.43) μg/GBq ( n=5), which met the requirements of European Pharmacopoeia. Three batches of 68Ga-PSMA-11 and 68Ga-DOTATATE were automatically synthesized, with the yield, concentration and radiochemical purity of (3.54±0.14) and (2.74±0.20) GBq, (294.97±11.58) and (228.17±16.32) GBq/L, (99.73±0.11)% and (99.45±0.25)%, respectively. Both sterility and bacterial endotoxin were qualified. Conclusion:High-yield and qualified nuclide 68Ga and 68Ga-labeled drugs are successfully prepared through the low-energy medical cyclotron solid target system and the automated purification and synthesis module, which provide a strong guarantee for clinical practice.

Study of 68Ga-NODAGA-RGD PET/CT in predicting short-term efficacy of tyrosine kinase inhibitor in the treatment of distant metastatic differentiated thyroid cancer / 中华核医学与分子影像杂志

Objective:To investigate the clinical application of 68Ga-cyclo( L-arginylglycyl- L-α-aspartyl- D-tyrosyl-N6-(((4, 7-bis(carboxymethyl)-1, 4, 7-triazonan-1-yl)acetyl))- L-lysyl) (NODAGA-RGD) PET/CT to evaluate short-term efficacy of tyrosine kinase inhibitor (TKI) in distant metastatic differentiated thyroid cancer (dmDTC). Methods:From October 2019 to March 2023, 13 dmDTC patients (5 males, 8 females; age: 68(65, 69) years) from Nanjing First Hospital were retrospectively enrolled, of which 9 were clinically confirmed as radioactive iodine-refractory differentiated thyroid cancer (RAIR-DTC) and 4 were dmDTC without radioactive iodine treatment. All patients underwent 68Ga-NODAGA-RGD PET/CT to assess neovascularization of the target lesions (TL), and the SUV max and target background ratio (T/B) were recorded. After 3 months of TKI treatment (anrotinib ( n=9) or apatinib ( n=4)), change rates of the maximum diameter of TL and thyroglobulin (Tg) were measured. The correlation of SUV max, T/B and the change rate of the maximum diameter of TL were analyzed by Spearman rank correlation analysis. ROC curve analysis was performed for the effectiveness of the T/B and TKI therapy, and the difference of the remission rate of lesions was analyzed by Fisher exact test. Results:In 13 patients, 36 TL were measured by 68Ga-NODAGA-RGD PET/CT with SUV max of 5.44(3.43, 7.56) and T/B of 5.25(4.50, 7.23). The change rate of the maximum diameter of TL was -30%(-39%, -21%) and the change rate of Tg was -68%(-96%, -52%). T/B was negatively correlated with the change rate of the maximum diameter of TL after TKI therapy ( rs=-0.46, P=0.005), while SUV max was not correlated with the change rate of the maximum diameter of TL ( rs=0.03, P=0.883). ROC curve analysis showed that the optimal cut-off value for T/B was 4.95, with the AUC of 0.698, the sensitivity of 87.5%, and the specificity of 60.0%. Compared to lesions with T/B<4.95, those with T/B≥4.95 showed higher remission rate (2/14 vs 63.6%(14/22); P=0.006). After 3 months of TKI treatment, the disease control rate was 12/13. Conclusion:68Ga-NODAGA-RGD PET/CT can effectively reflect tumor neovascularization, predict efficacy of TKI therapy, and provide powerful imaging evidence for TKI therapy in dmDTC.

Development of radiolabeled tetramer that targeting fibroblast activation protein and theranostic research in tumor xenografts / 中华核医学与分子影像杂志

Objective:To develop a tetramer probe targeting fibroblast activation protein (FAP), named 1, 4, 7, 10-tetraazacyclododecane-1, 4, 7, 10-tetraacetic acid (DOTA)-4P(FAP inhibitor (FAPI)) 4, evaluate its biodistribution and PET image in FAP-positive-tumor bearing nude mice, and explore its feasibility as a novel radio-regent for treatment of FAP-positive tumor. Methods:FAP tetramer probe was constructed on the FAPI-46 motif with four mini-polyethylene glycol (PEG)(PEG 3) spacers between the four FAPI motifs, denoted as 4P(FAPI) 4. DOTA was used as the chelator for radiolabeling with 68Ga and 177Lu. The FAP binding characteristics were test by in vitro cell competitive binding experiment. Small-animal PET, in vivo biodistribution, and radionuclide targeting therapy were performed in HT-1080-FAP tumor bearing nude mice ( n=39). Independent-sample t test was performed to analyze tumor uptake data, and two-factor repeated measures analysis of variance was utilized to compare tumor volume data in radioactive isotope therapy. Results:Cell experiment showed that FAPI-tetramer and FAPI-monomer had similar half maximal inhibitory concentration values (3.29 and 2.15 nmol/L). 68Ga/ 177Lu radiolabeled FAPI-tetramer had better tumor uptake and retention than FAPI-monomer in small-animal PET and in vivo biodistribution experiment, with the tumor uptake for 177Lu-DOTA-4P(FAPI) 4 and 177Lu-FAPI-46 at 48 h of (18.72±1.32) vs (2.72±1.20) percentage activity of injection dose per gram of tissue (%ID/g) ( t=15.55, P<0.001). 177Lu-DOTA-4P(FAPI) 4 group showed best anti-tumor efficacy compared with 177Lu-FAPI-46 and control group in radionuclide targeting therapy. On the 2nd day after the start of treatment, the tumor volume in the tetramer treatment group was significantly smaller than that in the control group (mean difference 67.19 mm 3, P=0.049); on the 14th day after the start of treatment, the tumor volume in the tetramer treatment group was significantly smaller than that in the monomer treatment group (mean difference 414.33 mm 3, P=0.005). Conclusion:FAPI-tetramer can improve tumor uptake and retention ability compared with FAPI-46, and 177Lu-DOTA-4P(FAPI) 4 can be a promising radio-agent for FAP-positive tumor therapy.

Diagnostic and prognostic value of 68Ga-FAPI PET for malignant tumors of the liver and biliary tract / 中华核医学与分子影像杂志

Objective:To investigate the diagnostic and prognostic value of 68Ga-fibroblast activation protein inhibitor (FAPI) PET for hepatobiliary malignancies. Methods:From July 2020 to February 2023, 33 patients (23 males, 10 females; age (55.4±13.5) years) with suspected or confirmed liver or biliary tract malignancies who underwent 68Ga-FAPI PET in Union Hospital, Tongji Medical College, Huazhong University of Science and Technology were retrospectively analyzed. PET images were evaluated by 3 experienced nuclear medicine physicians, and the results of biopsy or postoperative pathology, clinical and imaging follow-up were used as the gold standard. One-way analysis of variance and least significant difference t test were used to compare the differences among groups. Survival analysis was performed using Kaplan-Meier curves and the log-rank test. Results:Of 33 patients, 14 performed PET for initial diagnosis and staging, and 19 for restaging. There were 14 patients with hepatocellular carcinoma (HCC), 13 patients with cholangiocarcinoma (CCA), and 6 patients with gallbladder carcinoma (GBC). The primary tumor of HCC, CCA and GBC all showed significant 68Ga-FAPI uptake, with no statistically significant difference in SUV max among groups ( F=1.58, P=0.250). The sensitivities of 68Ga-FAPI PET for initial diagnosis and restaging of hepatobiliary malignancies were 14/14 and 15/15, respectively. Compared with conventional imaging, 68Ga-FAPI PET changed the diagnosis and staging in 29.2%(7/24) patients. The treatment strategy was changed in 30.3%(10/33) patients with malignant tumors due to 68Ga-FAPI PET findings. Follow-up showed 22 cases survived and 11 cases died, with the overall survival of 355.56(80.00, 516.97) d, and 1- and 2-year survival rates were 68.2% and 57.9%, respectively. Semi-quantitative 68Ga-FAPI PET parameters such as SUV max, target-liver ratio (TLR), and target-blood ratio (TBR) had no significant prognostic value, but the prognosis of the group without distant metastases diagnosed by 68Ga-FAPI PET was significantly better than that of the group with distant metastasis ( P=0.032). Conclusion:68Ga-FAPI PET has high sensitivity for the diagnosis of hepatobiliary malignancies, which can help guide treatment decisions and prognosis evaluation.

Application value of 68Ga-PSMA-11 PET/CT in newly diagnosed prostatic cancer patients / 中华核医学与分子影像杂志

Objective:To explore the value of 68Ga-prostate specific membrane antigen (PSMA)-11 PET/CT in newly diagnosed prostate cancer patients with different risk stratifications, and to compare the performance of this modality with conventional imaging in detecting metastases. Methods:From June 2019 to July 2020, the clinical and imaging data of 60 patients (age range: 44-88 years, median age 69 years) who underwent 68Ga-PSMA-11 PET/CT imaging in Fudan University Shanghai Cancer Center were retrospectively analyzed. Spearman rank correlation analysis was used to explore the correlation of SUV max in primary foci with prostate specific antigen (PSA) and Gleason score (GS). Based on the D′Amico risk stratification (PSA>20 μg/L and ≤20 μg/L, GS>7 and ≤7), the detection rates of 68Ga-PSMA-11 PET/CT for metastases were evaluated by χ2 test, and the differences of SUV max were analyzed by Mann-Whitney U test. Patients were divided into high-risk (PSA>20 μg/L and GS>7), medium-risk (PSA>20 μg/L and GS≤7, or PSA≤20 μg/L and GS>7), and low-risk (PSA<20 μg/L and GS<7) groups according to PSA levels and GS. Compared with conventional imaging (bone imaging, CT or MRI), the ability of 68Ga-PSMA-11 PET/CT to detect metastatic tumors, and the utility to change the prostate cancer stage were evaluated by Fisher′s exact test. Results:High uptake of 68Ga-PSMA-11 was observed in primary lesions of 60 patients, and SUV max was positively correlated with GS or PSA ( rs values: 0.42, 0.38; P values: 0.001, 0.002). The detection rates of lymph node and bone metastases in the group with PSA>20 μg/L were 11/18 and 13/18, respectively, which were higher than those in the group with PSA≤20 μg/L (28.57%(12/42) and 35.71%(15/42); χ2 values: 6.56, 7.56, P values: 0.010, 0.006. However, there was no statistical significance in the SUV max of these lesions( z values: -1.04, -0.96; P values: 0.299, 0.337). There was a statistical difference in the detection rates of lymph node and bone metastases between the group with GS>7 and the group with GS≤7 (lymph node: 54.05%(20/37) vs 13.04%(3/23), χ2=10.09, P=0.001; bone metastases: 59.46%(22/37) vs 26.09%(6/23), χ2=8.19, P=0.004), as well as the SUV max of bone metastases( z=-2.02, P=0.044). In the high-risk group, 68Ga-PSMA-11 PET/CT had the higher detection rate of metastases than conventional imaging (16/17 vs 10/17; P=0.039) and it changed 25.0%(15/60) of the patients′ staging. Conclusions:PSA and GS affect the detection rate of 68Ga-PSMA-11 PET/CT. In patients with high-risk prostate cancer, 68Ga-PSMA-11 PET/CT is superior to conventional imaging in detecting metastases. When PSA>20 μg/L and GS>7, it is better to use 68Ga-PSMA-11 PET/CT in prostate cancer staging.

PET/CT and PET/MRI in neuroendocrine neoplasms.

Advanced molecular imaging has come to play an integral role in the management of gastro-entero-pancreatic neuroendocrine neoplasms (GEP-NENs). Somatostatin receptor (SSTR) PET has now emerged as the reference standard for the evaluation of NENs and is particularly critical in the context of peptide receptor radionuclide therapy (PRRT) eligibility. SSTR PET/MRI with liver-specific contrast agent has a strong potential for one-stop-shop multiparametric evaluation of GEP-NENs. 18F-FDG is a complementary radiotracer to SSTR, especially in the context of high-grade neuroendocrine neoplasms. Knowledge gaps in quantitative evaluation of molecular imaging studies and their role in assessment of response to PRRT and combination therapies are active research areas. Novel radiotracers have the potential to overcome existing limitations in the molecular imaging of GEP-NENs. The purpose of this article is to provide an overview of the current trends, pitfalls, and recent advancements of molecular imaging for GEP-NENs.

Study on the relation of the radiochemical purity and in vivo imaging effect of 68Ga-DOTATATE injection / 中华核医学与分子影像杂志

Objective:To explore the relation of the radiochemical purity and in vivo imaging effect of 68Ga-1, 4, 7, 10-tetraazacyclododecane-1, 4, 7, 10-tetraacetic acid (DOTA)- D-phe1-Tyr3-Thr8-octreotide (TATE) injection. Methods:High performance liquid chromatography (HPLC) and thin-layer chromatography (TLC) methods were established to determine 68Ga-DOTATATE, 68Ga 3+ , 68Ga in colloidal form and 68Ga-DOTA- D-Phe1-Tyr3-Thr8-dethreonine-octreotide (heptapeptide) and to study the influence of precursor purity on radiochemical purity of labelled products. The uptake of 68Ga-DOTATATE injection with different radiochemical purities was investigated in nude mice bearing AR42J cells by microPET imaging and the tumor target/non-target (T/NT) value was calculated. One-way analysis of variance and Pearson correlation analysis were used to analyze the data. Results:The contents of 68Ga 3+ and 68Ga in colloidal form were not related with precursor purity ( r values: 0.385, 0.497, P values: 0.306, 0.137), while the content of 68Ga-DOTA-heptapeptide was positively related with the purity of DOTA-heptapeptide ( r=0.957, P<0.001). The radiochemical purities of 68Ga-DOTATATE injection were (87.0±2.3)%, (86.8±0.8)% and (94.0±3.1)% when the DOTATATE purities were 90.9%, 91.6% and 99.2%, respectively. The results of microPET imaging showed that the tumor uptake was positively related with the radiochemical purity of 68Ga-DOTATATE injection ( r=0.828, P<0.001), and the T/NT values of 68Ga-DOTATATE injection with radiochemical purities of 95.7%, 85.8%, 84.5% and 79.9% were 21.25±8.84, 8.50±1.51, 11.38±1.65 and 6.01±0.99, respectively ( F=11.48, P=0.001). Conclusion:The radiochemical purity of 68Ga-DOTATATE injection is impacted by the purity of labelled precursor and manufacturing processes and is related with the imaging effect in vivo.

SPECT/CT imaging of PD-L1 expression in non-small cell lung cancer based on 99Tc m labeled anti-PD-L1 nanoantibodies / 中华核医学与分子影像杂志

Objective:To explore the value of SPECT/CT imaging on programmed death receptor 1 ligand (PD-L1) expression in patients with non-small cell lung cancer (NSCLC) based on 99Tc m labeled anti-PD-L1 nanoantibodies (NM-01). Methods:From January 2019 to March 2020, a total of 14 patients (11 males, 3 females; age: (61.9±11.0) years) with pathologically confirmed NSCLC in Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine were prospectively enrolled. NM-01 were labeled with 99Tc m, and patients were recruited for SPECT/CT imaging 2 h after injection with 99Tc m-NM-01((359.1±68.0) MBq). The differences of SUV max in primary and metastatic lesions between PD-L1 positive and negative patients were compared by independent sample t test. The correlation between the SUV max and PD-L1 expression of primary lesions was analyzed by Pearson correlation analysis. Results:Of 14 patients, 6 were PD-L1 positive and 8 were PD-L1 negative. 99Tc m-NM-01 showed obviously increased uptake in kidneys and liver, while mildly increased uptake in spleen and bone marrow. The SUV max of primary lesions was 4.69±1.88 and the SUV max of metastatic lesions was 2.04±1.32. The SUV max of primary lesions in PD-L1 positive patients was significantly higher than that of PD-L1 negative patients (5.99±1.99 vs 3.72±1.10; t=5.98, P=0.039). There was no significant difference in the SUV max of metastatic lesions between PD-L1 positive and negative patients (1.66±1.03 vs 2.35±1.46; t=-1.77, P=0.084). The SUV max of primary lesions was positively correlated with PD-L1 expression ( r=0.648, P=0.042). Conclusion:99Tc m-NM-01 can demonstrate the expression of PD-L1 in primary and metastatic lesions in NSCLC.

Pretargeted immunoPET imaging with epidermal growth factor receptor monoclonal antibody in mouse models / 中华核医学与分子影像杂志

Objective:To explore the feasibility of pretargeting technique for immunoPET with epidermal growth factor receptor (EGFR) monoclonal antibody in EGFR positive/negative tumor bearing mice.Methods:Cetuximab- Trans-cyclooctene (TCO)was obtained by modifying Cetuximab with TCO- N-hydroxysuccinimide (NHS). 2, 2′-((6-amino-1-(4, 7-bis-(carboxymethyl)-1, 4, 7-triazonan-1-yl)hexan-2-yl)azanediyl)-diacetic acid (L-NETA)was used as a chelating agent to prepare the radioligand 68Ga-L-NETA-tetrazine (Tz), then the labeling rate and in vitro stability of the product were determined. Human basal breast cancer cells MDA-MB-468 (EGFR+ ) and MDA-MB-231 (EGFR-) were cultured in vitro. In vitro experiments were performed to explore the specificity of the probe and the feasibility of pretargeting technique. Nude mice (Balb/c-nu) bearing xenografts of the above two cell lines were established. Cetuximab-TCO (50 μg) was injected into the tumor-bearing mice in advance, then 68Ga-L-NETA-Tz was injected at different time points (48, 36, 24 and 12 h), and pretargeting was realized through " click chemistry" . Small-animal PET imaging and biodistribution were performed to evaluate pharmacokinetic properties and specificity of the probe. The one-way analysis of variance was used to compare the data. Results:The 68Ga-L-NETA-Tz molecular probe was successfully prepared with the labeling yield >95%, and the radiochemical purity was >95% after 2 h. Cetuximab-TCO and 68Ga-L-NETA-Tz were added to MDA-MB-468 cells successively, and the cell uptake rate reached (0.69±0.04)% at 1 h, which demonstrated the feasibility of the pretargeting technique. PET imaging and biodistribution results showed that the best imaging results were obtained in 36 h pre-injection group, in which the tumor uptake was the highest ((0.77±0.05) percentage activity of injection dose per gram of tissue (%ID/g), 1 h) and the tumor/muscle ratio was optimal (4.67±0.46); the tumor uptake in the blocking group, the group without injecting Cetuximab-TCO, and the MDA-MB-231 group were significantly lower ((0.35±0.01), (0.39±0.05), (0.45±0.10) %ID/g; F=15.50, P=0.002). Conclusions:EGFR targeted immunoPET imaging is successfully performed in mouse models of breast cancer by injecting Cetuximab-TCO and 68Ga-L-NETA-Tz successively. It provides an effective method for immunoPET imaging of monoclonal antibodies.

Site-specific labelling and biological evaluation of PD-L1 targeted single-domain antibody / 中华核医学与分子影像杂志

Objective:To synthesize a novel site-specifically labelled probe 68Ga-1, 4, 7, 10-tetraazacyclododecane-1, 4, 7, 10-tetraacetic acid (DOTA)-Cys-Asp-Val (CDV)-Nb109 and explore its potential for detection of the programmed cell death ligand 1 (PD-L1) expression level in different tumors. Methods:Firstly, CDV was inserted into the tail of the sequence of Nb109 by genetic engineering. Then the precursor DOTA-CDV-Nb109 was prepared by mixing the maleimide-DOTA and the single-domain antibody CDV-Nb109 (amount of substance ratio 1∶1) via the maleimide-cysteine site-specific coupling strategy. Subsequently, the DOTA-CDV-Nb109 was labeled with 68Ga and purified by PD-10 column. Human melanoma A375, human PD-L1 transfected melanoma A375-hPD-L1 and human glioma U87 tumor-bearing mice models were established, and the diagnostic value of 68Ga-DOTA-CDV-Nb109 was evaluated by stability assay, cellular uptake, and microPET imaging. One-way analysis of variance and the least significant difference t test were used to analyze the data. Results:The probe 68Ga-DOTA-CDV-Nb109 was obtained with the radiochemical yield of (69.79±4.69)%, radiochemical purity more than 97%, and molar activity of (12.85±1.51) GBq/μmol. 68Ga-DOTA-CDV-Nb109 had strong binding affinity for A375-hPD-L1 with the dissociation constant ( Kd) of (66.43±17.89) nmol/L. The uptake of 68Ga-DOTA-CDV-Nb109 in A375-hPD-L1 and U87 cells were (3.17±0.15) percentage of the added radioactivity dose (%AD) and (2.08±0.03) %AD respectively, which were significantly higher than that in A375 cells ((1.21±0.14) %AD; F=82.87, t values: 15.23, 9.98, P values: <0.001, 0.003). The tumor uptake of the probe in A375-hPD-L1 ((5.21±0.35) percentage of injected dose per ml (%ID/ml)) and U87 tumor-bearing mice ((3.44±0.69) %ID/ml) were significantly higher than that in A375 tumor-bearing mice ((2.17±0.36) %ID/ml; F=249.72, t values: 35.70, 3.43, both P<0.001). Conclusion:The site-specifically labelled probe 68Ga-DOTA-CDV-Nb109, which can non-invasively and dynamically monitor the change of PD-L1 expression level in different tumors and help screen patients who can benefit from PD-L1 immune checkpoint blocking therapy, is successfully synthesized with high radiochemical purity.

Kinetic metrics of 68Ga-FAPI-04 in patients with pancreatic cancer identified by total-body PET/CT dynamic imaging / 中华核医学与分子影像杂志

Objective:To investigate the kinetic metrics of 68Ga-fibroblast activation protein inhibitor (FAPI)-04 in pancreatic cancers and normal organs by using total-body PET dynamic imaging. Methods:From December 2020 to December 2021, 68Ga-FAPI-04 total-body PET/CT dynamic imaging were performed on 6 pancreatic cancer patients (3 males, 3 females, median age 55.5 years) in Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University. Images were respectively analyzed. Manual delineations of volume of interests (VOIs) on multiple normal organs and pathological lesions were performed and time-to-activity curves (TACs) were generated. A reversible two-tissue compartment model (2TCM) was fitted for each tissue TAC. Rate constants including K1, k2, k3 and k4, and the total volume of distribution ( Vt) were obtained and compared by tissue types. Wilcoxon rank sum test and Spearman correlation analysis were used for data analysis. Results:Kinetic metrics varied significantly among normal organs and pancreatic cancer lesions ( z values: 2.00-1 240.00, all P<0.05). The highest K1 among lesions was observed in primary tumor (0.30 min -1), which was observed in the spleen (1.42 min -1) among normal organs. The highest k2 among lesions was observed in peritoneal metastases (0.24 min -1), which was observed in the spleen (2.59 min -1) among normal organs. Primary tumor showed the highest k3 of 0.17 min -1 among lesions, and the pancreas had the highest k3 of 0.16 min -1 among normal organs. Primary tumor had the highest k4 of 0.03 min -1 among lesions, and the heart, lungs, parotid glands had high k4(0.06 min -1) among normal organs. Vt were higher in pathological lesions compared to normal organs, with the highest in primary tumor (13.78 ml/cm 3). There were correlations between Vt in lesions and SUV mean( rs=0.86, P<0.001) or SUV max ( rs=0.77, P<0.001). Conclusion:The rate constants including K1, k2, k3 and k4, and Vt of 68Ga-FAPI-04 vary among normal organs and lesions.

68Ga-DOTA-VAP molecular probe targeted glucose-regulated protein 78 for specific microPET/CT imaging of tumors / 中华核医学与分子影像杂志

Objective:To evaluate the specificity of 68Ga-1, 4, 7, 10-tetraazacyclododecane-1, 4, 7, 10-tetraacetic acid (DOTA)-Ser-Asn-Thr-Arg-Val-Ala-Pro (SNTRVAP, VAP) molecular probe targeting glucose-regulated protein 78(GRP78) in vivo and in vitro and the feasibility of 68Ga-DOTA-VAP microPET/CT imaging in the diagnosis of GRP78-positive tumors. Methods:68Ga-DOTA-VAP was prepared by the combination of bifunctional chelating agent DOTA and VAP, followed by 68Ga labeling. Western blotting experiment was perfomed to detect the expression of GRP78 in U87MG, BxPC-3, and 293T cell lines, at the same time, cold polypeptide blocked experiments were conducted to verify the specific binding of 68Ga-DOTA-VAP to cells. U87MG and BxPC-3 subcutaneous transplantation tumor mouse models were established and the biodistribution of 68Ga-DOTA-VAP were explored in vivo. The imaging effect of 68Ga-DOTA-VAP in GRP78-positive tumor-bearing mouse models was evaluated by microPET/CT. Independent-sample t test, one-way analysis of variance and Dunnett t test were used for data analysis. Results:68Ga-DOTA-VAP was easily prepared with labeling yield and radiochemical purity >98%. It had good stability in vitro, and its radiochemical purity was still (98.27±0.22)% after 2 h. GRP78 was highly expressed in U87MG and BxPC-3 cells, but lowly expressed in 293T cells ((0.78±0.02), (0.53±0.05) and (0.36±0.03), F=102.22, P<0.001; t values: 0.43, 0.18, both P<0.01). The uptake of 68Ga-DOTA-VAP in U87MG cells was higher than that in BxPC-3 cells (5 154.00±216.70 vs 4 344.00±60.88; t=3.10, P=0.027). Excessive unlabeled VAP polypeptide could significantly reduce the uptake of 68Ga-DOTA-VAP both in U87MG and BxPC-3 cells (3 324.00±54.14, 3 270.00±131.10; t values: 8.19, 7.43, both P<0.01). The uptake of 68Ga-DOTA-VAP in U87MG tumor tissue was higher than that in BxPC-3 tumor tissue ((1.98±0.20) vs (1.30±0.08) percentage activity of injection dose per gram of tissue (%ID/g); t=5.48, P=0.005), while co-injection of excessive unlabeled VAP polypeptide significantly reduced the uptake in U87MG and BxPC-3 tumors ((0.99±0.02) and (0.62±0.05) %ID/g; t values: 8.32, 12.25, both P<0.05). MicroPET/CT imaging showed that 68Ga-DOTA-VAP could clearly display U87MG and BxPC-3 tumors, and U87MG had a better imaging effect. The tumors could not be clearly visualized after co-injection of excessive VAP polypeptide. Conclusion:68Ga-DOTA-VAP molecular probe binds with GRP78 specifically and can reflect the expression level of GRP78 in vivo, which may be a promising probe for the specific imaging diagnosis of GRP78-positive tumors.

Effect of different β values combined with partial volume effect correction on the semi-quantitative accuracy and image quality of 68Ga-PSMA PET/CT / 中华核医学与分子影像杂志

Objective:To compare the effect of different β values on the semi-quantitative accuracy and image quality of 68Ga-prostate specific membrane antigen (PSMA) PET/CT imaging after partial volume effect correction (PVC). Methods:In the model experiment, image reconstruction was carried out based on block sequential regularized expectation maximization algorithm (BSREMA) with the range of β values from 100 to 1 000. Recovery coefficient (RC), contrast recovery (CR) and background variability (BV) were measured to evaluate semi-quantitative accuracy and image quality. In the clinical study, image data of 21 prostate cancer patients (age 45-78 years) who underwent 68Ga-PSMA PET/CT examination in the First Hospital of Shanxi Medical University from March 2019 to February 2020 were retrospectively collected. A total of 29 abdominal imaging positive lymph nodes were divided into the small lymph node group (diameter <10 mm; n=12) and the large lymph node group (10 mm≤diameter≤30 mm; n=17). SUV parameters including SUV max, SUV mean and peak of SUV (SUV peak) and the influence of different β values on the SUV parameters were evaluated. The signal to noise ratio (SNR) and subjective scores were used to evaluate image quality. Independent-sample t test, Kappa test and Pearson correlation analysis were used to analyze data. Results:The model experiment showed that CR, RC and BV decreased with the increase of β values. The image quality, image clarity, lesion significance, and total image scores given by nuclear medicine physicians showed strong consistency ( Kappa values: 0.65-0.87, P values: 0.026-0.043). The small lymph node group had the highest score (13 and 14) with β value of 600, while the large lymph node group had the highest score (13 and 14) with β value of 700. SNR of the two groups increased steadily within β values from 100 to 600 ( t values: 2.49-8.99, P values: 0.023-0.038). When the β value was higher than 600, SNR of the small lymph node group reached a plateau ( t values: 1.28-2.00, P values: 0.072-0.098), while the SNR of the large lymph node group continued to increase ( t values: 2.98-4.63, P values: 0.012-0.029). Before PVC, there were significant negative correlations between SUV parameters and β values ( r values: from -0.94 to -0.64, P values: 0.039-0.046). After PVC, it was found that SUV mean and SUV max still had significant negative correlation with β values ( r values: from -0.78 to -0.68, P values: 0.035-0.042), while the SUV peak showed no significant correlation with β values ( r values: -0.22, -0.28, P values: 0.069, 0.126). Conclusions:Based on subjective scores and semi-quantitative indicators, 68Ga-PSMA PET/CT is superior to select β values of 600 and 700 for image reconstruction based on BSREMA. The SUV peak of small lesions is stable after PVC and the clinical value should be explored in further.

Synthesis and biological evaluation of 68Ga-NODAGA-GE11 / 中华核医学与分子影像杂志

Objective:To prepare 68Ga-2-(4, 7-bis(carboxymethyl)-1, 4, 7-triazonan-1-yl)pentanedioic acid (NODAGA)-YHWYGYTPQNVI (GE11) and evaluate its feasibility of PET imaging for pancreatic cancer. Methods:GE11 peptide was conjugated with NODAGA and then labeled with 68Ga. The labeling yield, radiochemical purity, hydrophilicity, stability and specificity in vitro were determined. Human pancreatic cancer BxPC3 nude mice models ( n=9) were established. MicroPET imaging was then obtained after 30 and 90 min, and mice were sacrificed at 90 min to acquire the radioactivity distribution of main organs and tumors. Pair t test was used to analyze the data. Results:The labeling yield was (73.5±5.4)% and radiochemical purity was more than 98%. After incubation 120 min in mouse serum at 37 ℃, radiochemical purity was more than 92%. The uptake was specific in BxPC3 cell lines. MicroPET images showed that 68Ga-NODAGA-GE11 could accumulate quickly in tumor. Value of tumor uptake was significantly higher than that of normal pancreas at 90 min ((1.38±0.25) vs (0.49±0.07) %ID/g; t=12.67, P<0.05), and the radio-uptake of blood, muscle and bone was lower than that of tumor. Conclusions:68Ga-NODAGA-GE11 is easy to be prepared with high radiochemical purity and good stability, and can specifically target BxPC3 xenograft tumor. However, due to the high uptake in the kidneys and liver, the value of 68Ga-NODAGA-GE11 in PET imaging for pancreatic tumor needs further study.

Comparison of 68Ga-PSMA PET/CT and 18F-FDG PET/CT for preoperative TNM staging of patients with prostate cancer / 中华核医学与分子影像杂志

Objective:To compare the diagnostic efficacy of 68Ga-prostate specific membrane antigen (PSMA)-11 PET/CT and 18F-fluorodeoxyglucose (FDG) PET/CT in TNM staging before radical prostatectomy. Methods:From July 2018 to December 2019, a total of 67 patients ((67.5±6.8) years) with prostate cancer diagnosed pathologically by radical surgery in Renji Hospital, School of Medicine, Shanghai Jiao Tong University were retrospectively enrolled. All patients underwent 68Ga-PSMA-11 PET/CT and 18F-FDG PET/CT whole-body scans before surgery. Results of PET/CT were compared with pathological diagnosis after surgery to compare the diagnostic efficiencies of 68Ga-PSMA-11 PET/CT and 18F-FDG PET/CT for preoperative TNM staging ( χ2 test). The differences of the maximum standardized uptake value (SUV max) in primary lesions between 2 imaging methods were compared by Mann-Whitney U test. Patients were divided into low-risk, intermediate-risk and high-risk for stratified analysis. Results:Among 67 patients, 9 were with low-risk, 19 were with intermediate-risk, 39 were with high-risk. For T staging, 59 (88.06%, 59/67) patients showed positive results by 68Ga-PSMA-11 PET/CT imaging, with median SUV max of 13.80(7.30, 22.40) for 67 patients; 31(46.27%, 31/67) patients showed positive results in 18F-FDG PET/CT imaging, with median SUV max of 4.00(3.10, 5.60) ( U=62, P<0.05). Stratifed analysis showed that the detection rate of 68Ga-PSMA-11 PET/CT was higher than that of 18F-FDG PET/CT in intermediate-risk patients (17/19 vs 6/19; χ2=4.920, P<0.05). Among 67 patients, 10 were diagnosed as N1 stage based on the pathological results. The sensitivities, specificities, accuracies, positive predictive values and negative predictive values of 68Ga-PSMA-11 PET/CT and 18F-FDG PET/CT for detecting positive regional lymph nodes were 6/10, 87.72%(50/57), 83.58%(56/67), 6/13, 92.59%(50/54) and 4/10, 89.47%(51/57), 82.09%(55/67), 4/10, 89.47%(51/57), respectively. 68Ga-PSMA-11 PET/CT detected 15 patients (22.39%, 15/67) with M1 stage, and 18F-FDG PET/CT identified 9 patients (13.43%, 9/67; χ2=35.436, P<0.05). Conclusions:As for T staging, the detection rate of 68Ga-PSMA-11 PET/CT in the intermediate-risk group is better than 18F-FDG PET/CT. In N and M staging, the detection rates of 68Ga-PSMA-11 PET/CT are higher than those of 18F-FDG PET/CT.

Synthesis and evaluation of 68Ga-labeled ODAP-PSMA targeting probe / 中华核医学与分子影像杂志

Objective:To synthesize a 68Ga-labeled oxalyldiaminopropionic acid (ODAP)-urea based prostate specific membrane antigen (PSMA) targeting probe, and evaluate its properties in vitro and in vivo. Methods:Ligand P151 was synthesized by solid-phase synthesis and its Ki value was determined. The ligand P151 was added into the mixture of 68GaCl 3 and NaOAc solution and was reacted at 95 ℃ for 10 min. The labeling yield and in vitro stability of 68Ga-P151 were determined by high performance liquid chromatography (HPLC). The lipid-water partition coefficient (log P) and cell binding ability were determined. The biodistribution of 68Ga-P151 in normal KM mice was determined. MicroPET imaging of 68Ga-P151 was carried out in prostate cancer 22Rv1 tumor-bearing mice and compared with 68Ga-PSMA 617. Independent sample t test was used to analyze the data. Results:P151 was successfully synthesized with the Ki of 0.58 nmol/L, the labeling yield more than 95% and the radiochemical purity more than 95%. After placement in saline or human serum albumin (HSA) solution at 37 ℃ for 2 h, the radiochemical purity of 68Ga-P151 was still more than 95%, indicating a good stability in vitro. The lipid-water partition coefficient (log P) of 68Ga-P151 was -2.65±0.17, indicating a good hydrophilicity. 68Ga-P151 specifically bound to PSMA in prostate cancer LNCaP cells with the uptake value of (0.83±0.04) percentage injection activity (%IA)/10 5 cells. Biodistribution of normal mice showed that 68Ga-P151 was mainly excreted through kidneys and other organs showed low uptake. MicroPET imaging of tumor-bearing mice showed the maximum standardized uptake value (SUV max: 0.79±0.23 vs 0.54±0.05; t=2.12), tumor/kidney ratio (2.04±0.65 vs 1.88±0.33; t=0.44) and tumor/muscle ratio (12.83±5.18 vs 6.95±1.63; t=2.17) between 68Ga-P151 and 68Ga-PSMA 617 were not significantly different (all P>0.05). Conclusions:68Ga-P151 can be prepared simply and labeled in high yield and show improved pharmacokinetic properties in vivo. The imaging of 68Ga-P151 on PSMA positive tumor is comparable to that of 68Ga-PSMA 617, making it a potential radiopharmaceutical for the diagnosis of prostate cancer.