Diffusion Weighted MR Imaging: Evaluation Of Pulmonary Lesions

Part Ⅰ Differential Diagnosis of MR Diffusion Weighted Imaging inPeripheral Lung LesionsObjective: To evaluate diffusion-weighted MR imaging in differentialdiagnosis of peripheral lung lesions by using ADC values with different bvalues.Methods: Diffusion-weighted imaging was performed with a SiemensAvanto1.5-T MR scanner （TR/TE：6800ms/70ms,FOV300×430mm，3mm-thick,1mm spacing, body phased-array coil）in40cases（12women,28men, mean age,59years）that had diagnosised to be peripheral lung lesionsby CT scan or chest X-ray. Observe the signal intensity of the lung lesionson DW images, which was classified of hypointensity or hyperintensity incomparison with the signal intensity of adjacent muscle. ADC of each lunglesions was calculated from DW MR images obtained with different bvalues（b=0,600,800and1000sec/mm²）. ADC values of lung leisions werecompared between benign lesions and malignant lesions,histopathologictypes,different differentiation degree of lung lesions.The diagnostic ability ofADC values with different b values in differentiating between well-differentiated adenocarcinoma and poorly-differentiated lung cancer wascalculated according to ROC curve,and an optimal threshold value of ADCwas chosen.Area under ROC value,sensitivity,specificity for differentialdiagnosis of lung lesions were evaluated.Results:In all40cases，there are10cases of benign lesions,9cases ofsquamous cell carcinoma，5cases of small cell carcinoma,16cases ofadenocarcinoma（6cases of well-differentiated adenocarcinoma,10cases ofpoorly-differentiated adenocarcinoma and4cases of moderately-differentiatedadenocarcinoma）.The majority of well-differentiated adenocarcinoma and benign lesions were low or isointensity.signal intesity. Squamous cellcarcinoma,small cell carcinoma and moderately and poorly adenocarcinomawere high signal intensity in Diffusion weighted imaging.ADC values of the benign lesions in different b values （b=0,600,800,1000s/mm²）were significantly higher than that of malignant cancer,ADCvalues for SCLC were significantly lower than that for NSCLC. The ADCvalues of well-differentiated adenocarcinoma and benign lesions weresignificantly higher than that of other poorly-differentiated cancer.By ROCcurve analyzing,the area under ROC value with b value of800s/mm²was thelargest, has the highest diagnostic ability of ADCs in differentiating betweenlung lesions.Conclusion:ADC values and signal intensity for DWI are helpful todifferentiate between malignant lung lesions and benigns.ADC values may behelpful to indicate the different differentiated degree of tumor.PartⅡ Diffusion-weighted magnetic resonance imaging in differentiation ofpostobstructive consolidation from centrallungcarcinomaObjective：To evaluate diffusion-weighted MR imaging and ADCvalues in differentiation diagnosis of central lung cancer from postobstructiveatelectasis by using ADC value with different b values.Methods:T1-weighted,T2-weighted and Diffusion-weighted imaging wasperformed with a Siemens Avanto1.5-T MR scanner（TR/TE：6800ms/70ms,FOV300×430mm，3mm-thick，1mm spacing，body phased-array coil）in48cases （14women,34men; mean age,59years; age range,34-81years）that had diagnosised to be central lung cancer with atelectasis.Makecomparison of signal intensity between lung cancer and atelectasis indifferent MR sequences. The ADC values of lung cancer and atelectasis withdifferent b values（b=0，600,800and1000sec/mm²） was calculated.Thesignal intensity ratio（SIR）of cancer and atelectasis were calculated withdifferent b values.Find the best b value to differentiating central lung andatelectasis. The diagnostic ability of ADC values in differentiating betweencentral lung and atelectasis was calculated according to ROC curve,and an optimal threshold value of ADC was chosen.Area under ROC value,sensitivity,specificity for differential diagnosis were evaluated.Results:In all48cases，there are27cases of squamous cell carcinoma，9cases of small cell carcinoma，5cases of adenocarcinoma and7casesdiagnosed cancer， but no specific pathological type.25cases can bedistinguished on T2WI，the signal intensity of cancer was lower than that ofatelectasis on T2WI Images.DWI can distinguish81%central lung cancer from atelectasis in allcases，shows the lung cancer was notable hyperintense,the signal intensity ofcancer was higher than that of atelectasis on DW images. T2WI can onlydistinguish52%cases,the signal intesensity of cancer was lower than that ofatelectasis on T2WI.The differentiation ablity of DWI was superior to that ofT2WI.The ADC value of malignant masses was significantly lower than thatof atelectasis.ADC values obtained from each b value can differentiate cancerfrom atelectasis，and SIR on DW images was significantly higher than SIR onT2WI.SIR with b value of1000s/mm²was the largest，the mean ADC valuefor the central lungcarcinoma was（1.10±0.16）×10^-3mm²/s, and forconsolidation was （2.02±0.24）×10^-3mm²/s.By ROC curve analyzing,theoptimal threshold value of ADC was1.64x10-3mm²/s.Conclusions: ADC values of central lung cancer was lower thanaccompanying consolidations. The differentiation ability of DWI was superiorto that of T2WI.DW images and ADC values was useful for differentiatingcentral lung cancer and postobstructive atelectasis.