Diffusion-weighted Magnetic Resonance Imaging For Evaluating The Response Of Chemotherapy In Non-small Cell Lung Cancer

Part I Lung cancer:short-term reproducibility of apparent diffusion coefficient and intravoxel incoherent motion parameters at 3TObjective To prospectively evaluate the short-term test-retest reproducibility of apparent diffusion coefficient and intravoxel incoherent motion parameters in lung cancer,and to investigate the influence of lung cancer type,size and location.Methods 50 patients（50 lesions）underwent free-breathing DWI（b=0,800 s/mm²）and IVIM（10 b-values,0-1000 s/mm²）scans twice（0.5–1 h interval）.Regions of interests（ROIs）were drawn on ADC maps and IVIM images to derive ADC value,IVIM parameters D,D*and f.Intra-and inter-observer,test–retest reproducibility were assessed with intraclass correlation coefficients（ICCs）,within coefficient-of-variations（WCVs）and Bland–Altman analysis.The effects of type,size and location of lung lesion were compared with WCVs.Results Good intra-and inter-observer agreement was shown,except D*（WCV 34.97%）.The test–retest reproducibility of D,ADC were good（ICC 0.775,0.763;WCV 11.33%,11.63%,respectively）,while D*and f was relatively poor（ICC 0.842,0.641;WCV 68.59%,36.54%,respectively）.D and ADC had decreased reproducibility in lesions﹤2cm（WCV 14.20%,16.34%,respectively）and lesions in the lower lung zone（WCV 16.52%,14.78%,respectively）.f had decreased reproducibility in central lung cancer（WCV 50.11%）and lesions﹥2cm（WCV 42.64%）.D*demonstrated generally large variations,particularly for peripheral lung cancer（WCV 84.11%）and lesions in the lower lung zone（WCV 80.84%）.Conclusions If the change in ADC,D,D*and f is less than 23%,22%,134%and 72%,respectively,it may be caused by measurement error.The type,size,and location of lung lesions are the potential factors.Part II Diffusion-weighted magnetic resonance imaging for evaluating the response of chemotherapy in non-small cell lung cancerObjective To prospectively investigate the ADC and IVIM parameters to predict and monitor early response to chemotherapy in patients with locally advanced non-small cell lungcancer（NSCLC）.Methods 26 patients with pathologically confirmed advanced NSCLC underwent chest MR imaging at Siemens 3T Verio MRI,including T1WI,T2WI,free-breathing DWI（b=0,800 s/mm²）and IVIM（10 b-values,0–1000 s/mm²）scans,before and at the end of the first cycle of chemotherapy.Three different ROIs（ROI_m,including the maximunm slice of tumors;ROI_s,on the maximunm slice but avoiding the visible cystic and necrosis parts of tumors;ROI_v,encompassing the whole volume）were drawn on ADC maps and IVIM images to derive the mean ADC values,D,D*and f respectively.The effective group and the ineffective group were divided according to RECIST 1.1.The difference of the parameters was compared with different ROIs,pretreatment and posttreatment,the effective group and the ineffective group by using paired or independent sample t test.Receiver operating characteristic（ROC）curves were generated to evaluate the value of parameters on predicting tumor response.Results No matter which ROI was selected,ADC,D and f values showed good measurement repeatability（ICC﹥0.75）,while D*was moderate to good（ICC 0.507–0.716）.There were significant differences in ADC values obtained from different ROIs（P=0.024）,while the ADC values after treatment and D,f values showed no significant differences（P=0.202–0.924）.The effective group showed significantly low preADC（ROI_v）,preD（3ROIs）and high△ADC%（3ROIs）,△D%（3ROIs）,△MD_MRI%（P=0.000–0.040）.The areas under the curve showed no significant difference when using these parametes as diagnostic index（P=0.095–1.000）.Conclusions IVIM pure diffusion parameter D including necrosis may better predict and monitor early response to chemotherapy in NSCLC patients,which is expected to become a promising biomarker for clinical treatment evaluation.ROI selection encompassing the whole volume may predict the efficacy before treatment with high specificity.When evaluating with ADC values,volumetric analysis should be preferred.