Application Value Of ¹⁸F-FDG PET/CT Imaging In Clinical Evaluation Of Lymphoma

Objective:To study the distribution of lesions in various tissues and organs involved in lymphom.To analyze the evaluation value of ¹⁸F-FDG PET/CT on bone marrow infiltration.To compare the invasion and metabolic values of different pathological types of lymphoma,and to analyze the correlation between the clinical pathological indexes of lymphoma and the metabolic indexes of ¹⁸F-FDG PET/CT.To explore the accuracy of standardized uptake value（SUV）of ¹⁸F-FDG PET/CT in the diagnosis of invasive lymphoma,and the value of total metabolic tumor volume（TMTV）and total lesion glycolysis（TLG）in the evaluation of high-load lymphoma.Methods:It was a retrospective study.¹⁸F-FDG PET/CT images data,metabolic indexes and related clinical data of 44 lymphoma patients during 2017.10 to 2019.11were analyzed.Comprehensively understand the lesions distribution characteristics of lymphoma.The evaluation value of ¹⁸F-FDG PET/CT on bone marrow infiltration was analyzed.The differences of metabolic indexes（including:average standardized uptake value（SUVAvg）,maximum standardized uptake value（SUVmax）,total metabolic tumor volume（TMTV）,total lesion glycolysis（TLG））and invasion between lymphoma of different pathological classification were compared.The correlation between the metabolic indexes of ¹⁸F-FDG PET/CT and the clinical pathological indexes（including:gender,age,B group,clinical staging,risk stratification,bone marrow infiltration,primary lesion（extranode/intranode）,lesion resection,grade malignancy,and tumor burden）were explored.ROC wase drawn to obtain the optimal cut-off value of SUV in aggressive lymphoma,and calculate the diagnostic efficacy.Besides,the diagnostic value of TMTV and TLG for high-load lymphoma was analyzed by ROC.Results:（1）Intranode involving rates accounted for 79.87%（738/924）,and was significantly higher than extranode involving rates.The highest incidence of intranode was in the neck.（2）There were 186 extranodal lesions（both primary and non-primary）,among which 156 cases（83.87%）were DLBCL.Bone/bone marrow invasion was the highest in extranodal involvement（104/186,55.91%）,and was significantly higher than other extranodal organs.（3）The incidence of DLBCL,MALT-L and FL lesions was higher in intranode than extranode,and intranode involvement was more common in the neck,mediastinum,abdomen and iliac blood vessels,and the highest extranode involving rates was DLBCL（156/451,34.59%）.（4）PENL accounted for 47.73%（21/44）,gastrointestinal was the most frequent involved sites.The common pathological type of PENL was DLBCL（61.90%,13/21）,and accounted for 54.17%（13/24）of similar type.The most common of PENL in similar type is MALT-L（100%,6/6）,and accounted for 28.57%（6/21）of PENL.The clinical staging are mainly advanced-stage（15/21,71.43%）.Those with systemic symptoms accounted for 30%（3/10）of the total cases with systemic symptoms,and those with bone marrow infiltration accounted for50%（3/6）of the total cases of bone marrow infiltration.（5）Bone marrow infiltration was confirmed by bone marrow examination in 6 patients（13.64%）,and the detection rate was lower than the reported level.¹⁸F-FDG PET/CT indicated that bone marrow-positive cases,the false positive rate,false negative rate,sensitivity and specificity were 7.89%,66.67%,33.33%and 92.11%,respectively,compared with those who underwent bone marrow examination.（6）In different pathological subtypes of lymphoma,the SUV（Avg,max）was the highest in DLBCL,followed by PTCL or NK/T cell lymphoma,and the lowest was MCL.The level of SUV was consistent with the grade malignancy,and there was a statistical difference between some subtypes（P<0.05）.The highest of TMTV and TLG is DLBCL,and the lowest is MALT-L,and there was statistical difference between DLBCL and MALT-L（both P<0.05）,there was no statistical difference between DLBCL and FL,and between MALT-L and FL（P>0.05）.（7）SUV（Avg,Max）were correlated with age,clinical staging,risk stratification,bone marrow infiltration,lesion resection,grade malignancy（all P<0.05）,but was not correlated with gender,B group,primary lesion（extranode/intranode）,and tumor burden（all P>0.05）.TMTV was correlated with lesion resection,risk stratification,grade malignancy,and tumor burden（all P<0.05）,but was not correlated with gender,age,B group,clinical staging,bone marrow infiltration,and primary lesion（extranode/intranode）（all P>0.05）.TLG was correlated with age,lesion resection,grade malignancy,and tumor burden（all P<0.05）,but was not correlated with gender,B group,clinical staging,bone marrow infiltration,primary lesions（intranode extranode）,and risk stratification（all P>0.05）.Spearman rank correlation analysis showed that SUV（Avg,Max）were significantly positively correlated with the grade malignancy（r=0.576,0.591,both P<0.001）,TMTV was significantly positively correlated with tumor burden（r=0.528,P<0.001）,and other factors such as age,clinical staging and risk stratification were low-level or weakly correlated.（8）Aggressive lymphoma was more likely when SUVAvg was greater than 3.78（sensitivity 80%,specificity 54%）or SUVmax was greater than 8.40（sensitivity 83%,specificity 60%）.SUVmax under the ROC was greater than SUVAvg,and both SUVAvg and SUVmax were significant for the diagnosis of aggressive lymphoma（P<0.001）,and SUVmax was more valuable than SUVAvg.Although the SUV of aggressive lymphoma was greater than that of indolent lymphoma（P<0.001）,there was overlap between the values,and there was no clear cut-off value to determine whether aggressive or indolent.（9）Both TMTV and TLG had significant significance in determining the high tumor burden（P<0.05）.When the TMTV was greater than 285.46 cm3（sensitivity 65%,specificity 85%）and TLG was greater than 2079.16（sensitivity 65%,specificity 83%）,the tumor load could be considered to be high.The area TMTV under ROC was greater than TLG.TMTV has higher diagnostic efficiency than TLG in the diagnosis of high tumor load.Conclusion:（1）¹⁸F-FDG PET/CT can comprehensively and intuitively understand the general distribution of lymphoma lesions.It has a high specificity for whole-body bone marrow assessment and can be used as an important examination method to assist clinical bone marrow biopsy.（2）Through its uptake of ¹⁸F-FDG,it can help clinicians to distinguish aggressive and indolent lymphoma.（3）SUV（Avg,Max）,TMTV,TLG were correlated with a number of clinical indicators,among which SUV（Avg,Max）were significantly positively correlated with the grade malignancy,TMTV was significantly positively correlated with tumor burden,and other factors such as age,clinical staging and risk stratification were low-level or weakly correlated.（4）When SUVmax was greater than 8.40,the possibility of aggressive lymphoma was higher and was more valuable than SUVAvg.（5）Both TMTV and TLG can be used to determine the high tumor load,and the diagnostic efficiency of TMTV is better than TLG and has higher specificity.When TMTV was greater than 285.46 cm3 and TLG was greater than2079.16,higher tumor load can be considered.