Objective To propose a novel method based on three-dimensional depthwise separable convolution network(3D DSN)for the separation of PET images with dual tracers of 18F-FDG and 18F-FAPI.Methods A total of 120 pairs of 18F-FDG and 18F-FAPI PET images of the same patient scanned separately at different time points were collected,and the dual-tracer PET image was generated through simulation.After the image registration of PET images of two tracers for ensuring spatial position matching,the registered PET images were forward-projected to generate sinogram data,and the sinogram data of two tracers were accumulated to obtain mixed sinogram data.Subsequently,the dual-tracer PET image was reconstructed using maximum likelihood expectation maximization and input into a 3D DSN based network for image separation,thereby obtaining PET images of two single tracers.Results Compared with 3D CNN method,the proposed method increased the structure similarity index measure(SSIM)of the separated 18F-FDG images to the real 18F-FDG images by 0.87%,increased the peak signal-to-noise ratio(PSNR)by 11.8%,and reduced the normalized root mean square error(NRMSE)by 52%.The SSIM of the separated 18F-FAPI images to the real 18F-FAPI images increased by 1.1%,PSNR increased by 17.0%,and NRMSE decreased by 51%.Conclusion The proposed method can be effectively applied to simultaneous PET imaging with dual PET tracers,reducing the number of scans and costs in time and money,and providing clinical doctors more accurate and abundant diagnostic information.

Nanobodies(Nb)have become novel probes for PET imaging instead of traditional antibodies,which have broad application prospects due to advantages of small molecular weight,strong stability and permeability,passing through the blood-brain barrier and low immunogenicity.The research progresses of structural characteristics of Nb,labeling methods of positron isotopes and application of labeled products in PET imaging were reviewed in this article.

Objective To propose a novel method based on three-dimensional depthwise separable convolution network(3D DSN)for the separation of PET images with dual tracers of 18F-FDG and 18F-FAPI.Methods A total of 120 pairs of 18F-FDG and 18F-FAPI PET images of the same patient scanned separately at different time points were collected,and the dual-tracer PET image was generated through simulation.After the image registration of PET images of two tracers for ensuring spatial position matching,the registered PET images were forward-projected to generate sinogram data,and the sinogram data of two tracers were accumulated to obtain mixed sinogram data.Subsequently,the dual-tracer PET image was reconstructed using maximum likelihood expectation maximization and input into a 3D DSN based network for image separation,thereby obtaining PET images of two single tracers.Results Compared with 3D CNN method,the proposed method increased the structure similarity index measure(SSIM)of the separated 18F-FDG images to the real 18F-FDG images by 0.87%,increased the peak signal-to-noise ratio(PSNR)by 11.8%,and reduced the normalized root mean square error(NRMSE)by 52%.The SSIM of the separated 18F-FAPI images to the real 18F-FAPI images increased by 1.1%,PSNR increased by 17.0%,and NRMSE decreased by 51%.Conclusion The proposed method can be effectively applied to simultaneous PET imaging with dual PET tracers,reducing the number of scans and costs in time and money,and providing clinical doctors more accurate and abundant diagnostic information.

Nanobodies(Nb)have become novel probes for PET imaging instead of traditional antibodies,which have broad application prospects due to advantages of small molecular weight,strong stability and permeability,passing through the blood-brain barrier and low immunogenicity.The research progresses of structural characteristics of Nb,labeling methods of positron isotopes and application of labeled products in PET imaging were reviewed in this article.

Objective:To explore the relationship between 18F-fibroblast activation protein inhibitor (FAPI)-42 SUV max of primary gastric cancer and clinicopathological factors of patients. Methods:Fifty-one patients (31males, 20 females, age: 51(47, 65) years) with gastric cancer who underwent 18F-FAPI-42 PET/CT before surgical resection in Nanfang Hospital, Southern Medical University from February 2022 to January 2023 were analyzed retrospectively. The clinicopathological factors that might affect tumor SUV max (including gender, age, tumor location, pathological type, histological grade, Lauren classification, vascular and(or) neural invasion, programmed cell death-ligand 1 (PD-L1) expression, pathologic(p)T stage, pN stage and pTNM stage) were evaluated by the univariate analysis (Mann-Whitney U test or Kruskal-Wallis rank sum test) and multivariate analysis (multiple linear regression analysis). Results:The sensitivity of 18F-FAPI-42 PET/CT in the diagnosis of patients with primary gastric cancer was 82.35% (42/51). The diagnostic sensitivities for early gastric cancer (T1) and locally advanced gastric cancer (T2-T4) were 59.09%(13/22) and 100%(29/29), respectively. The SUV max of primary lesion was 4.90(1.71, 12.51). The univariate analysis showed that SUV max of primary gastric cancer was related to tumor location ( z=-2.00, P=0.046), pT stage ( H=36.94, P<0.001), pN stage ( z=-3.89, P<0.001), pTNM stage ( H=31.49, P<0.001) and vascular and(or) nerve invasion ( z=-5.22, P<0.001), but not related to pathological type, histological grade, Lauren typing, and PD-L1 expression ( z values: from -1.78 to -0.09, all P>0.05). pT stage was found to be a significant independent factor for SUV max in primary gastric lesion by multivariate analysis ( t=2.52, P=0.015). Conclusions:The 18F-FAPI-42 SUV max of primary tumor was related to tumor location, pT stage, pN stage, pTNM stage, and vascular and(or) nerve invasion; pT stage is an independent factor affecting tumor SUV max. The ability of 18F-FAPI-42 PET/CT to detect gastric cancer is mainly affected by pT stage.

In recent years, fibroblast activation protein (FAP) has emerged as an attractive target for the diagnosis and radiotherapy of cancers using FAP-specific radioligands. Herein, we aimed to design a novel ¹⁸F-labeled FAP tracer ([¹⁸F]AlF-P-FAPI) for FAP imaging and evaluated its potential for clinical application. The [¹⁸F]AlF-P-FAPI novel tracer was prepared in an automated manner within 42 min with a non-decay corrected radiochemical yield of 32 ± 6% (n = 8). Among A549-FAP cells, [¹⁸F]AlF-P-FAPI demonstrated specific uptake, rapid internalization, and low cellular efflux. Compared to the patent tracer [¹⁸F]FAPI-42, [¹⁸F]AlF-P-FAPI exhibited lower levels of cellular efflux in the A549-FAP cells and higher stability in vivo. Micro-PET imaging in the A549-FAP tumor model indicated higher specific tumor uptake of [¹⁸F]AlF-P-FAPI (7.0 ± 1.0% ID/g) compared to patent tracers [¹⁸F]FAPI-42 (3.2 ± 0.6% ID/g) and [⁶⁸Ga]Ga-FAPI-04 (2.7 ± 0.5% ID/g). Furthermore, in an initial diagnostic application in a patient with nasopharyngeal cancer, [¹⁸F]AlF-P-FAPI and [¹⁸F]FDG PET/CT showed comparable results for both primary tumors and lymph node metastases. These results suggest that [¹⁸F]AlF-P-FAPI can be conveniently prepared, with promising characteristics in the preclinical evaluation. The feasibility of FAP imaging was demonstrated using PET studies.

Low targeting efficiency limits the applications of nanoparticles in cancer therapy. The fact that mesenchymal stem cells (MSC) trapped in the lung after systemic infusion is a disadvantage for cell therapy purposes. Here, we utilized MSC as lung cancer-targeted drug delivery vehicles by loading nanoparticles (NP) with anti-cancer drug. MSC showed a higher drug intake capacity than fibroblasts. In addition, MSC showed predominant lung trapping in both rabbit and monkey. IR-780 dye, a fluorescent probe used to represent docetaxel (DTX) in NP, delivered MSC accumulated in the lung. Both MSC/A549 cell experiments and MSC/lung cancer experiments validated the intercellular transportation of NP between MSC and cancer cells. assays showed that the MSC/NP/DTX drug delivery system exerted primary tumor inhibition efficiency similar to that of a NP/DTX drug system. Collectively, the MSC/NP drug delivery system is promising for lung-targeted drug delivery for the treatment of lung cancer and other lung-related diseases.

Objective:To investigate the effects of dexmedetomidine on perioperative cardiac adverse events in elderly patients with coronary heart disease.Methods:Sixty elderly patients,who were diagnosed as coronary heart disease and underwent gastric cancer operation,were randomly divided into 2 groups (n=30):the dexmedetomidine group (Dex group) and the control group.In the Dex group,dexmedetomidine was administered intravenously at 0.5 μtg/(kg.h) after a bolus infusion at 0.5 μg/kg for 10 min before anesthesia induction.In the control group,equal volume of normal saline was infused instead of dexmedetomidine.The 2 groups received the same anesthesia treatment.The venous bloods were collected at the preoperative 0 h and postoperative 24 h.The concentrations of cardiac troponin (cTnⅠ),N-terminal pro-brain natriuretic peptide (NT-proBNP) and hypersensitive C-reactive protein (hs-CRP) were determined.The ECG was monitored at the above time and the postoperative incidence of cardiac adverse events was recorded.Results:The levels of cTnⅠ,NT-proBNP and hs-CRP in serum were elevated in the 2 groups after the operation.Compared with the control group,the levels of cTnⅠ,NT-proBNP and hs-CRP were significantly decreased in the Dex group (P＜0.05).Compared with the control group,the incidence ofbradycardia were significantly increased,while the myocardial ischemia and tachycardia were significantly decreased in the Dex group during the operation (P＜0.05);the incidence of silent myocardial ischemia and arrhythmia was significantly reduced at 3 days after operation in the Dex group (P＜0.05).Conclusion:Dexmedetomidine could decrease the incidence of cardiac adverse events in elderly patients with coronary heart disease.

Objective To establish a diagnostic model based on 18F-FDG PET/CT and clinical data and assess its diagnostic potency for characterizing SPN.Methods From November 2004 to May 2014,164 patients with SPN who underwent 18F-FDG PET/CT scan were retrospectively analyzed.The patients'clinical factors (age,gender,history of smoking and history of malignancy),information on CT (diameter,location and spiculated edge of the lesion) and metabolic information on PET imaging were collected to establish a diagnostic model by using the binary logistic regression.Then,the optimal operating point (OOP)of the established model was set.The diagnostic potencies of the established model and PET were assessed by ROC curve.Results Malignancy was diagnosed in 104 of 164 SPN patients.The rest 60 patients had benign diseases.The factors of age,spiculation(0:no spiculation,1:obvious spiculation) and metabolic information(0:≤ mediastinal blood pool,1:＞mediastinal blood pool) were demonstrated to be useful for the establishment of the model (x2 =5.486,16.240,33.855,all P＜0.05).However,the factors of gender,history of smoking,the diameter and location of lesions showed no influence for the model (x2 =2.452,0.453,0.127,0.390,all P＞0.05) and rejected from the model established.The history of malignancy was excluded from statistical analysis because there were only 2 patients with history of malignancy.The established model was as follows:P=1/(1+e-Z),z=-5.512+0.061xage+2.208xspiculation+3.767×metabolic increase.The ROC AUC of the established model and PET using two-point scoring scale (TPSS) for charactering SPN were 0.92(95％ CI:0.87-0.96)and 0.80(95％ CI:0.73-0.86).The model had higher diagnostic efficacy compared with TPSS (z=4.369,P＜0.05).When P=0.796 7 was set as an OOP,the diagnostic sensitivities of the model and PET for charactering SPN were 91.3％ (95/104) and 94.2％ (98/104) respectively,and no significant difference was found between them (x2 =0.800,P＞0.05).However,significant difference was found between the diagnostic specificities of them (80.0％ (48/60) vs 65.0％ (39/60);x2 =7.111,P＜0.05).Conclusions A new diagnostic model for characterizing SPN based on the information from 18FFDG PET,thin-section CT and clinical data is successfully established.Its sensitivity for diagnosis of lung cancer is high,and its specificity is superior to PET using with TPSS.This model has a potential value for clinical application.

Objective We propose a method using total variation (TV) regularization in deconvolution for partial volume correction in PET imaging. In the degraded image model, we used TV regularization procedure in Van Cittert (VC) and Richardson-Lucy (RL) deconvolution algorithms. These methods were tested in simulated NCAT images and images of NEMA NU4-2008 IQ phantom and tumor-bearing mouse scanned by Simens Invoen microPET. The simulated experiment and tumor-bearing mouse experiment showed that the algorithms using TV regularization provided superior qualitative and quantitative appearance compared with traditional VC and RL algorithms. When the mean intensity of the tumor increased by (10 ± 1.8)%, the SD increase percentage was decreased from 49.98%to 14.26%and from 42.76%to 4.70%, suggesting the efficiency of the proposed algorithms for reducing PVEs in PET.