| Part One A Primary Study on the Distribution Characteristics of 68Ga-DOTATOC in Normal Tissues and Organs of Chinese AdultsPurpose The aim of this part was to study the characteristics of distribution of 68Ga-DOTATOC in normal tissues and organs of Chinese adults.Methods This retrospective study enrolled 24 patients(13 males,11 females,median age 50.5 years old)who underwent 68Ga-DOTATOC PET/CT scan in Changhai Hospital for suspected neuroendocrine neoplasms(NENs)between February 2019 and August 2019.All enrolled patients were proven to have no evidence of NEN during a more than 6 months follow-up,or have a single lesion of NEN less than 3 cm by histopathologic examinations after PET/CT scan.Patients were injected with 68Ga-DOTATOC(62.1?173.9 MBq)intravenously,and underwent PET/CT scan 40?60 min after injection.Images of PET/CT scans were analysed by 2 experienced nuclear medicine physicians together.The maximum and mean standardized uptake values(SUVmax and SUVmean)of normal tissues and organs were measured by means of drawing regions of interesting(ROIs).One-way analysis of variance,t-test or rank sum test was used for statistical analysis according to the characteristics of data.The difference was consider statistically significant when P-value<0.05.Results(1)68Ga-DOTATOC was mainly excreted by urinary system.Except the collecting system,spleen showed the highest uptake of 68Ga-DOTATOC.Liver,adrenal gland,renal cortex,pancreatic processus uncinatus and pituitary showed relatively high uptake.Parotid gland,thyroid,pancreas(expect the processus uncinatus),the wall of gastrointestinal tract,prostate and uterus presented mild uptake,while central nervous system,blood pool in mediastinum,lung,skeletal muscle and bone presented low uptake.(2)The SUVmax and SUVmean of pancreatic processus uncinatus were 5.56±2.43 and 4.34±1.85,respectively,which were both higher than other parts of pancreas.The uptake of pancreatic tail was higher than the head,while was similar to the body.(3)Prostate showed relatively high uptake in some patients,which was usually presented as symmetrical concentration near the center of the organ.(4)There was no significant difference in major organs uptake between males and females,as well as patients under 50 years old and beyond.(5)Within the range of 40?60 min after the injection of 68Ga-DOTATOC,the patients with an interval of ?45 min between injection and PET scan presented higher SUVmax and SUVmean in mediastinal blood pool than those with an interval of>45 min(P values were 0.022 and 0.015,respectively).SUVmean of liver in patients of former group was lower than the latter(P=0.020),while there was no significant difference in SUVmax between the two groups(P=0.075).No difference was found in other organs and tissues uptake between the two groups.Conclusion The distribution of 68Ga-DOTATOC varied from tissue to tissue in Chinese adult which was similar to 68Ga-DOTATATE.Some normal tissues or organs might present relatively high uptake of the agent.It was necessary to differentiate NEN lesions from physiological focal high uptake region,especially pancreatic processus uncinatus,pituitary and liver.The mechanism and meaning of uptake of 68Ga-DOTATOC in prostate need further study.In the range of 40?60 min,68Ga-DOTATOC was gradually eliminated from blood pool,while concentrated in liver.The factors influencing the distribution of the agent need larger samples to verify.Part Two A Prospective Study on the Diagnostic Value of Combined Dual-time-point 68Ga-DOTATOC and 18F-FDG PET/CT in Neuroendocrine NeoplasmsPurpose The aim of this part was to investigate the diagnostic value of combined dual-time-point 68Ga-DOTATOC and 18F-FDG PET/CT in neuroendocrine neoplasm(NEN).Methods From February 2019 to November 2019,forty-five patients(24 males and 21 females,median age 51 years old)with suspected lesions of NEN were prospectively enrolled.All the patients underwent combined 68Ga-DOTATOC and 18F-FDG PET/CT in Changhai Hospital,or underwent 68Ga-DOTATOC PET/CT in Changhai Hospital and could provide the data of 18F-FDG PET/CT of other hospital that met the requirements of this study in ".DICOM" format.Medical histories and results of conventional imaging and laboratory examinations of all patients were collected.Images of 68Ga-DOTATOC PET/CT were analysed visually and semiquantitatively by two designed experienced nuclear medicine physicians independently,and images of 18F-FDG PET/CT were analysed by two other designed physicians in the same way.All physicians were blind to the histories of diagnoses and therapies related to NEN,the results of conventional imaging examinations and PET/CT of the other agent,as well as the interpretation of other physicians,until their respective works were completed.Maximum diameter on the cross-sectional image and SUVmax in both 68Ga-DOTATOC and 18F-FDG PET/CT(SUVG and SUVF)of every suspected lesion were measured.Then the tumor-to-background ratios in both PET/CT examinations(TBRG and TBRF),the SUVG-to-SUVF ratios(GFR)and TBRG-to-TBRF ratios(TBRR)of lesions were calculated.All findings were compared with the histopathologic diagnoses or the clinical final diagnoses based on clinical follow-ups longer than 3 months.Receiver operating characteristic(ROC)curve was drawn for every parameter,meanwhile the area under curve(AUC)and the cut-off value was calculated.Results For 68Ga-DOTATOC PET/CT,sensitivity,specificity,accuracy,positive likelihood ratio(PLR)and negative likelihood ratio(NLR)in diagnosing NEN were 77.4%,85.7%,80.0%,5.41 and 0.26 on patientwise analysis,respectively,and 87.4%,84.8%,87.1%,5.77 and 0.15 on regionwise analysis,respectively.While for 18F-FDG PET/CT,the results were 71.0%,57.1%,66.7%,1.66 and 0.51 on patientwise analysis,respectively,and 52.4%,36.4%,50.5%,0.82 and 1.31 on regionwise analysis,respectively.For combined 68Ga-DOTATOC and 18F-FDG PET/CT,the results were 93.5%,50.0%,80.0%,1.87 and 0.13 on patientwise analysis,respectively,and 94.7%,27.3%,86.7%,1.30 and 0.19 on regionwise analysis,respectively.The kappa consistency coefficient of 68Ga-DOTATOC,18F-FDG and combined PET/CT compared with histopathologic diagnoses or clinical final diagnoses were 0.58,0.27,0.48 on patientwise analysis,respectively,and 0.54,-0.50,0.26 on regionwise analysis,respectively.The AUCs of SUVG,TBRG,SUVF,TBRF,GFR,TBRR were 0.869,0.898,0.610,0.643,0.752 and 0.776,respectively,and the cut-off values were 3.525,3.900,2.425,3.515,1.850 and 4.020,respectively.Maximun diameter,SUVF and TBRF were related to the Ki-67 index of NEN.The diagnositic value of PET/CT on delayed scan was close to early scan in this study.The retention index of NEN and non-NEN lesion were-8.0%(-22.9%,9.9%)and-28.1%(-37.5%,-1.8%)on 68Ga-DOTATOC PET/CT,respectively,and 5.3%(-10.6%,40.3%)and 9.2%(-3.2%,30.6%)on 18F-FDG PET/CT,respectively.Conclusion 68Ga-DOTATOC PET/CT was better in sensitivity,specificity and accuracy,moreover,it presented the most consistent with histopathologic diagnoses or clinical final diagnoses.SUVmax and TBR of 18F-FDG PET/CT were related to the Ki-67 index of NEN which may help to select the region of pathologic examination and evaluate the risk stratification.The combination of two PET/CT took advantage of both methods and improved the sensitivity,while reduced the specificity.The improvement of TBR in delayed phase enhanced the confidence of diagnosis,moreover,RIG of NEN lesions was significantly higher than non-NEN lesions.The DTPI of combined PET/CT still need further study. |
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