A Clinical Study Of Diffusion-weighted Imaging And Multiphase Delayed Pseudo-continuous Arterial Spin Labeling Imaging Based On FROC Model In The Differential Diagnosis Of Salivary Gland Tumors

First PartDifferentiation of salivary gland tumor using diffusion-weighted imaging with a fractional order calculus modelObjective: To evaluate the feasibility of using imaging parameters(D,β and μ)obtained from fractional order calculus(FROC)diffusion model to differentiate salivary gland tumors.Materials and methods :Fifteen-b-value(0 to 2000 sec/mm2)diffusion weighted imaging(DWI)was scanned in 62 patients with salivary gland tumors(47 benign and15 malignant).Diffusion coefficient D,fractional order parameter β(which correlates with tissue heterogeneity)and a microstructural quantity μ of the solid portion within the tumor were calculated,and compared between benign and malignant groups,or among pleomorphic adenoma(PA),Warthin’s tumor(WT),and malignant tumor(MT)groups.Performance of FROC parameters for differentiation was assessed using receiver operating characteristic analysis.Results: None of the FROC parameters exhibited significant differences between benign and malignant group(D,P=0.150;β,P=0.967;μ,P=0.693).WT showed significantly lower D(P<0.001)and β(P<0.001),while higher μ(P=0.001)than PA.Combination of D,β and μ showed optimal diagnostic performance(area under the curve,AUC,0.998).MT showed significantly lower D(P=0.001)and β(P=0.025)than PA,while no significant difference was found on μ(P=0.064).Combination of D and β showed optimal diagnostic performance(AUC,0.933).Significant difference was found on β(P=0.027)between MT and WT,while not on D(P=0.806)and μ(P=0.789).Setting a β of 0.615 as the cut-off value,optimal diagnostic performance could be obtained(AUC = 0.806).Conclusion: A non-Gaussian FROC diffusion model can serve as a noninvasive and quantitative imaging technique for differentiating salivary gland tumors.Second PartInfluence of post-label delay time on the performance of 3D pseudo-continuous arterial spin labeling magnetic resonance imaging in the characterization of parotid gland tumorsObjective: To evaluate the influence of post-label delay times(PLDs)on the performance of 3D pseudo-continuous arterial spin labeling(p CASL)magnetic resonance imaging for characterizing parotid gland tumors and to explore the optimal PLDs for the differential diagnosis.Materials and method: Fifty-eight consecutive patients with parotid gland tumors were enrolled,including 33 patients with pleomorphic adenomas(PAs),16 patients with Warthin’s tumors(WTs)and 9 patients with malignant tumors(MTs).3D p CASL were scanned for each patient five times with PLDs of 1025 ms,1525ms,2025 ms,2525ms and 3025 ms,respectively.Tumor blood flow(TBF)was calculated,and compared among different PLDs and tumor groups.Characterizing performance of TBF at different PLDs was evaluated using receiver operating characteristic analysis.Results: Along with increased PLDs,TBF tended to gradually increase within PAs(P<0.001),while TBF tended to slightly increase and then drop gradually within WTs(P=0.001).PAs showed significantly lower TBF than WTs at all 5 PLDs(P<0.05).PAs showed significantly lower TBF than MTs at 4 PLDs(P<0.05),except at 3025ms(P=0.062).WTs showed higher TBF than MTs at all 5 PLDs,however differences did not reach significance(P>0.05).Setting a TBF of 64.350 ml/100g/min at a PLD of1525 ms,or a TBF of 23.700 ml/100g/min at a PLD of 1025 ms as the cut-off values,optimal performance could be obtained for differentiating PAs from WTs(AUC=0.905)or from MTs(AUC=0.872).Conclusions: Short PLDs(1025ms or 1525ms)is suggested to be used in 3D p CASL for characterizing parotid gland tumors in clinical practice.