The Application Of 3T MRI In The Classification Of Diagnosing Pulmonary Nodules

Part One The application of 3T MRI in detecting pulmonary nodulesObjective: This study aimed to evaluate the visbility of different subgroups of pulmonary nodules using the 3T MRI T1 Star-VIBE,T2-HASTE,and T2-BLADE sequences in comparison with that obtained using CT.Methods: A total of 68 patients with pulmonary nodules diagnosed by CT underwent MRI examination.CT and MRI images were retrospectively analyzed.The sensitivity of the three MRI sequences to the detection of different types of pulmonary nodules(including solid nodules,partial solid nodules and ground glass nodules)was calculated,and the average diameter of the nodules was measured using CT images(slice thickness 1mm)as the gold standard.The image quality was analyzed and compared among different sequences.SPSS21.0 was used for statistical analysis.The agreement of nodule size between CT and MRI were assessed by intraclass correlation coefficient(ICC).Results: 188 pulmonary nodules in 68 patients were detected by CT,including 87 solid nodules and 101 subsolid nodules(46 partial solid nodules and 55 ground glass nodules).The mean diameter of pulmonary nodules was7.7 mm.The sensitivity of MRI was 92% for nodules ≥ 6 mm in diameter and100% for nodules > 8mm in diameter.The sequence with the highest detection rate was T2-BLADE sequence.Comparing the detection rate of different types of nodules,the sequence with the highest detection rate of solid nodules was T1 Star-VIBE sequence,and the sequence with the highest detection rate of partial solid nodules and ground glass nodules was T2-BLADE sequence.The image quality of T1 Star-VIBE sequence was better than that of T2-HASTE sequence and T2-BLADE sequence.CT and MRI sequences had strong agreement for nodule size(ICC range 0.94-0.98).Conclusion: MRI has high sensitivity in detecting nodules larger than8 mm in diameter.The T2-BLADE sequence has the highest detection sensitivity,and the image quality of the T1 Star-VIBE sequence is better than other sequences.Compared with CT,the diameter of nodules is consistent with MRI.Therefore,3T MRI has great application potential in the detection of pulmonary nodules.Part Two Evaluation in Visibility of Lung Nodules Using Magnetic Res-onance PETRA SequenceObjective: This study aimed to evaluate the visibility of different subgroups of lung nodules using the pointwise encoding time reduction with radial acquisition(PETRA)sequence on 3T magnetic resonance imaging(MRI)in comparison with that obtained using computed tomography.Methods: The appropriate detection rate was calculated for each of the different subgroups of lung nodules.The mean diameter of each detected nodule was determined.The detection rates and diameters of the lung nodules detected by MRI with the PETRA sequence were compared with those detected by computed tomography(CT).The sensitivity of detection for the different subgroups of pulmonary nodules was determined based on the location,size,type of nodules and morphologic characteristics.Agreement of nodule characteristics between CT and MRI were assessed by intraclass correlation coefficient(ICC)and Kappa test.Results: The CT scans detected 256 lung nodules,including 99 solid nodules(SNs)and 157 subsolid nodules,mean nodule diameter of pumonary nodules was 8.3 mm.For the SNs,the MRI detected 30/47 nodules of <6 mm in diameter and 52/52 nodules of ≥6 mm in diameter.For the subsolid nodules,the MRI detected 30/51 nodules of <6 mm in diameter and 102/106 nodules of≥6 mm in diameter.The PETRA sequence returned a high detection rate(84%).The detection rates of SN,ground glass nodules,and PSN were 82%,72%,and 94%,respectively.For nodules with a diameter of >6 mm,the sensitivity of the PETRA sequence reached 97%,with a higher rate for nodules located in the upper lung fields than those in the middle and lower lung fields.Strong agreement was found between the CT and PETRA results.Conclusions: The PETRA technique had high sensitivity for different type of nodule detection and enabled accurate assessment of their diameter and morphologic characteristics.It may be an effective alternative to CT as a tool for screening and follow up pulmonary nodules.Part Three The application of free-breathing Star-VIBE sequence dyna-mic enhanced MRI combined with DWI in the diagnosis of solitary pulmonary nodules(SPN)Objective: To test the performance of free-breathing Dynamic ContrastEnhanced MRI(DCE-MRI)using a radial volumetric interpolated breath-hold examination(VIBE)sequence combined with diffusion-weighted imaging(DWI)for quantitative solitary pulmonary nodule(SPN)assessment.Methods: A total of 67 SPN cases receiving routine MRI routine scans,DWI,and dynamic-enhanced MRI in our hospital from May 2017 to November 2018 were collected.These cases were divided into a malignant group and a benign group according to the characteristics of the SPNs.The quantitative DCE-MRI parameters(Ktrans,Kep,Ve)and apparent diffusion coefficient(ADC)values of the nodules were measured.Compare the difference between benign and malignant nodules and different lung cancer subtypes.Results: The Ktrans and Kep values in the malignant group were higher than those in the benign group,while the ADC values in the malignant group were lower than those in the benign group.Furthermore,the Ktrans value of adenocarcinoma was higher than that of squamous cell carcinoma and small cell carcinoma(P < 0.05).The Ve value was significantly different between non-small cell carcinoma and small cell carcinoma(P < 0.05).With an ADC value of 0.98 × 10-3 mm2/s as the threshold,the specificity and sensitivity to diagnose benign and malignant nodules was 90.6% and 80%,respectively.Conclusion: High-temporal-resolution DCE-MRI using the r-VIBE technique in combination with DWI could contribute to pulmonary nodule analysis and possibly serve as a potential alternative to distinguish malignant from benign nodules as well as differentiate different types of malignancies.