Study Of Diffusion Weighted MRI In Evaluating The Response To Chemotherapy Of Lung Cancer

Objective:To determine reasonable b values in diffusion weighted imaging of lung cancer with1.5T MR. Assess the value of diffusion weighted imaging (DWI) in monitoring therapy effect of chemotherapy in patients with lung cancer, to provide a reliable basis for judging prognosis and protocol making.Materials and methods:The prospective study included30patients with lung cancer undergoing chemotherapy. MRI was examined before chemotherapy (the first time point),after the first cycle of chemotherapy(the second time point),including conventional T1、T2weighted imaging, conventional DWI(b=0s/mm2、500s/mm2600s/mm2、800s/mm2、1000s/mm2).All patients were confirmed by pre-treatment histopathological.11lesions were diagnosed as squamous cell carcinoma,9lesions were diagnosed as adenocarcinoma,8lesions were diagnosed as small cell carcinoma, and2lesions were Non-small cell carcinoma. By comparing RECIST, all lesions were divided into the groups of effective and invalid. The transverse maximum diameter, and apparent diffusion coefficient (ADC) was recorded and their changed values were measured, and then we had the tumor shrinkage rate and ADC rate of change.Paired-Samples T test were applied in comparison of parameters including the transverse maximum diameter, and ADC before chemotherapy and after the first cycle of chemotherapy. Spearman’s rank correlation coefficient was applied in evaluating correlation between the tumor shrinkage rate and ADC rate of change. Independent-samples T test were applied in comparison between effective group and invalid group, also the tumor shrinkage rate and ADC rate of change after first cycle.Receiver operating characteristic curve (ROC) was drawn to compare the accuracies of the evaluations for effective group.Results:The images of DW1and ADC of30patients were all captured clearly, and ADC values of ROI were measured.As b values increasing from500s/mm2to1000s/mm2,SNR of lung tissue decreased gradually. When b value was500s/mm2,the ADC value was highest,and then decreased gradually,but the reference rang of ADC value was not stable.There was no statistical difference in transverse maximum diameter (6.11±2.00cm,6.51±2.04cm, t=-0.537, p=0.596) between the effective group and invalid group before chemotherapy. There was no statistical difference in transverse maximum diameter (4.76±2.24cm,5.73±1.88cm, t=-1.283, p=0.210) between the effective group and invalid group after the first cycle of chemotherapy. There was no statistical difference in tumor maximum diameter shrinkage rate[(0.20±0.16)×100%(0.12±0.08)×100%, t=1.705, p=0.099] between the effective group and invalid group after the first cycle of chemotherapy.When b value was600s/mm2,ADCmean after the first cycle [(1.66±0.38)×10-3mm2/s] were significantly higher than the values before chemotherapy [(1.40±0.35)×10-3mm2/s]. There was significant difference in effective group between the before chemotherapy and after the first cycle of chemotherapy(t=-9.313,p=0.000,p <0.05).ADCmean after the first cycle [(1.45±0.31)×10-3mm2/s] were higer than the values before chemotherapy [(1.42±0.40)×10-3mm2/s]. There was no statistical difference in invalid group between the before chemotherapy and after the first cycle of chemotherapy(t=1.515,p=0.137) The ADC rate of change was (0.17±0.12) x100%after the first cycle in effective group.It was (0.07±0.06) x100%in invalid group. There was statistical difference between the effective group and invalid group after the first cycle of chemotherapy.The ADC rate of change was correlated positively with the tumor maximum diameter shrinkage rate(r=0.536, p<0.05) in effective group. The ADC rate of change was correlated positively with the tumor maximum diameter shrinkage rate(r=0.429, p <0.05) in invalid group.We compared areas under curve (AUC) of ADC values, ADC rate of change and tumor maximum diameter shrinkage rate for diagnosing as effective treatment by ROC. ADC rate of change had the best diagnostic capability among aforesaid parameters. Sensitivity and specificity of the diagnosis for effective group is85.7%and72.9%, as ADC rate of change more than8.5%.Conclusion:b value (600s/mm2) is the best parameter for DWI imging of lung cancer in this study.ADC which is measured from DWI could be used to assess early response to chemotherapy in lung cancer lesion, ADCmean could predict effective or invalid after the first cycle chemotherapy. Chemotherapeutic efficacy can be diagnosed by measuring the change in the parameters of morphology and functional imaging after the first cycle of chemotherapy. In addition, the ADC rate of change is the best parameter for predicting drug effect.