The Value Of MRI In Differential Diagnosis Of Brain Metastases From Small Cell Lung Cancer And Primary Lymphoma Of The Brain

Objective:The MRI manifestations of small cell lung cancer(SCLC)brain metastases and primary brain lymphoma(PLB)were analyzed to explore their MRI imaging features and the value of MRI in the differential diagnosis of the two.Materials and Methods:From January 2015 to December 2020,32 cases of brain metastases from SCLC and 37 cases of PLB scanned by plain and enhanced MRI of the head in our hospital were collected,and 17 cases of brain metastases from SCLC and 15 cases of PLB that examined by PWI in the same period were selected and their MRI manifestations were retrospectively analyzed.These included lesion morphology,number,location,degree of peritumoral edema,T1 WI and T2 WI signal characteristics of tumor parenchyma,enhancement characteristics(including mode and degree),and diffusion characteristics of tumor parenchyma and peritumoral edema.The ROC curve analysis was also performed on the r ADC values of tumor parenchyma in SCLC brain metastases and PLB.Meanwhile,the perfusion of 17 cases of SCLC brain metastases and 15 cases of PLB were analyzed and compared,including r CBV values and temporal signal intensity curve(TSIC)characteristics.Statistical software SPSS version 26.0 was used for analysis,and independent sample t-test was used between groups,and chi-square test or nonparametric rank sum test was used for counting data,and P < 0.05 was considered statistically significant.Results:1.Tumor morphology: brain metastases from SCLC often show round or quasi-round shape(204 cases,89.47%),and PLB often shows irregular shape(59 cases,58.42%).There is significant difference in tumor morphology between brain metastases from SCLC and PLB(P < 0.01).2.Number of tumors: SCLC brain metastases are common with multiple tumors(22 cases,68.75%)and PLB are common with single tumors(21 cases,56.76%),and there is a statistically significant difference in the number of tumors between the two(P=0.034).3.Distribution of tumor sites: The frontal lobe(71,31.14%)is the most common site of brain metastases from SCLC.Compared with brain metastases from SCLC,PLB is more likely to occur in basal ganglia and corpus callosum(36,35.64%),and there is a significant statistical difference between them(P < 0.01).4.Peritumoral edema degree: According to the grade of peritumoral edema,the number of 0-3 grade edema in 32 cases of brain metastases from SCLC was 2 cases,14 cases,5 cases and 11 cases;The number of 0-3 grade edema in 37 PLB lesions was 1case,7 cases,18 cases and 11 cases,there was no statistical difference between them(P=2.222).5.Analysis of tumor parenchymal signal: Plain scan of brain metastases from SCLC and PLB mostly showed low or slightly low signal shadow in T1 WI and high or slightly high signal shadow in T2 WI,while patients with hemorrhage show mixed T1 WI and T2 WI signals,and there is no statistical difference between them(p=0.067,p=0.092).6.Features of tumor enhancement:(1)Brain metastases from SCLC showed circular or uneven enhancement(82 cases,35.96%,80 cases,35.09%),and PLB showed uniform enhancement(85 cases,84.16%).There was a significant difference between them(P < 0.01).(2)Both brain metastases from SCLC and PLB were significantly enhanced,and there was no significant difference between them(p=1.171).7.Characteristics of tumor diffusion:(1)The r ADC value in the parenchyma of brain metastases from SCLC was higher than that of PLB(0.74±0.12,0.63±0.12),there was a significant difference between them(P < 0.01).When the threshold of r ADC value in tumor parenchyma was set at 0.665,the sensitivity and specificity of r ADC value in differentiating SCLC BMs from PLB were 66.8% and 67.6%.(2)The r ADC value of periumoral edema in brain metastases from SCLC and PLB was 2.46±1.13 and2.83±1.11,and the difference was not statistically significant(P =0.180).8.Characteristics of tumor perfusion:(1)17 cases of brain metastases from SCLC showed high perfusion,and 15 cases of PLB showed low perfusion.The r CBV value of tumor parenchyma was 6.08±1.31 and 1.44±0.35,and the difference was statistically significant(P < 0.01).(2)TSIC showed that after contrast agent inflow,the decrease rate of brain metastases from SCLC was significantly higher than that in PLB,the tumor parenchyma of 17 patients with brain metastases from SCLC was still below the baseline level after the first contrast treatment.In 15 cases of PLB tumor parenchyma,the signal enhancement returned to the baseline level after the first contrast treatment.Conclusion:1.The shape,number,location and enhancement method of the lesion can be used to distinguish SCLC brain metastases from PLB,tumor parenchymal T1 WI and T2 WI signals,the degree of tumor enhancement,and the degree of periumoral edema cannot be used to distinguish SCLC brain metastases from PLB.2.Limitation of tumor parenchymal diffusion can be used to distinguish brain metastases from SCLC from PLB,while restricted diffusion of peritumoral edema cannot be used to distinguish SCLC brain metastases from PLB.3.PWI is a supplement to the conventional sequence.Brain metastases from SCLC show high perfusion while PLB shows significantly low perfusion.The TSIC characteristics of the two are different,and PWI can be used to differentiate brain metastases from SCLC from PLB in clinical practice.