Value Of Diffusion-Weighted Imaging And Dynamic Contrast Enhanced MRI In The Diagnosis Of Orbital Masses

BackgroundThe eye is a vital organ.Orbital structure stems from three germ layers which are theepidermal ectoderm,mesoderm and neural ectoderm.Any germ layers can generateneoplasms, the tumor of surrounding structures can spread to the orbit and the tumor ofother parts far from the orbital can be transferred.These situations result in more than100different clinical pathologies affecting the orbit.So it can be difficult to diagnose anddifferentially diagnose some orbital neoplasms and simulating lesions.The main clinicalsigns and symptoms include proptosis,decreased visual acuity,eye globe dyskinesia,diplopia and papilledema.Misdiagnosis often cause severe clinical problems.Currently,conventionl gadolinium-enhanced magnetic resonance(MR) imaging are the optimalmodalities for delineation and characterization of orbital masses.However,distinctionbetween different tumor types,malignant and benign neoplasms,or evern neoplastic andnonneopplastic lesions is frequently not possible by using either clinical criteria orconventional imaging.With the improvement and development of magnetic resonance imaging techniques,more and more studies have been providing proof to investigate the role of functionalMR imaging in the evaluation of different organs. Diffusion-weighted imaging (DWI) is anoninvasive magnetic resonance imaging (MRI) technique which could be applied to thedetection and quantification of water diffusion in vivo. Dynamic contrast-enhanced MRI(DCE-MRI) is the acquisition of sequential images during the passage of a contrast agentwithin a tissue of interest. It permits a fuller depiction of the wash-in and wash-out contrastkinetics within tumors, and thus provides insight into the nature of the bulk tissueproperties. These can be quantified and are related to vascular density and other angiogeniccharacteristics of lesions, such as the level of vascular endothelial growth factor. Thepurpose of this study was to describe the DW imaging and DCE-MRI features of malignantand benign orbital masses, to determine whether MR imaging with DW imaging andDCE-MRI can help discriminate between benign and malignant orbital masses and toidentify optimal thresholds for such discrimination. Purposes1. To assess the diffusion-weighted MR image quality with different b value and determine the optimal b value in the diagnosis of orbital masses.2. To determine whether magnetic resonance (MR) imaging with diffusion-weighted (DW) imaging can help discriminate between benign and malignant orbitalmasses and to identify optimal apparent diffusion coefficient (ADC) thresholds for suchdiscrimination.Materials and MethodsIn this prospective study,81subjects(31males and50females) were enrolled.Theyunderwent serial MR and echo-planar DW imaging examination of the orbit with b valueof400,700and1000s/mm2at1.5MR unit(GE SIGNA EXCITE). Apparent diffusioncoefficient (ADC) maps were reconstructed, and the ADC value of the orbital mass wascalculated.Mass ADC was also compared with that of normal-appearing white matter(ADC ratio). The signal-noise-ratio (SNR) of the masses and the contrast-signal-noise-ratio(CNR)between the masses and normal-appearing white matter on diffusion-weightedimaging with different b values were calculated. Analysis of one-way ANOVA test,Friedman M test and independent-sample t test were used for statistical analysis.Results1. The SNR of the orbital masses were85.10±48.90,61.46±37.00,42.92±25.53on DWI(b=400s/mm2),DWI(b=700s/mm2) and DWI(b=1000s/mm2) respectively（χ2=125.654,P=0.000）.Compared with one another,there was statistically sinificantdifference（P<0.05).2. The CNR between the masses and normal-appearing white matter were28.36±26.67,20.11±17.19,16.59±15.29on DWI(b=400s/mm2),DWI(b=700s/mm2) andDWI(b=1000s/mm2) respectively(χ2=14.519,P=0.000). Compared with one another, therewas statistically sinificant difference between DWI(b=400s/mm2) and DWI(b=700s/mm2),DWI(b=400s/mm2) and DWI(b=1000s/mm2). there was no statistically sinificantdifference between DWI(b=700s/mm2) and DWI(b=1000s/mm2).3. The orbital masses ADCs were (1.42±0.44)×10-3mm2/s,(1.25±0.43)×10-3mm2/s and (1.16±0.40)×10-3mm2/s on functional diffusion maps with b=400s/mm2,700s/mm2and1000s/mm2, respectively（χ2=120.724,P=0.000<0.05）. Compared with onanother, there was statistically sinificant difference between DWI(b=400s/mm2) and DWI(b=700s/mm2), DWI(b=400s/mm2) and DWI(b=1000s/mm2). there was no statisticallysinificant difference between DWI(b=700s/mm2) and DWI(b=1000s/mm2).4. The orbital masses ADCRs were (1.47±0.45),(1.39±0.46) and (1.37±0.46) on functional diffusion maps with b=400s/mm2,700s/mm2and1000s/mm2, respectively.Compared with one another,there was no statistically sinificant difference (P=0.305).5. The ADCs of malignant orbital masses were (1.12±0.47)×10-3mm2/s,(0.92±0.42)×10-3mm2/s and (0.87±0.40)×10-3mm2/s on functional diffusion maps withb=400s/mm2,700s/mm2and1000s/mm2respectively. Compared with one another,therewas no statistically sinificant difference（P=0.099）. The ADCs of benign orbital masseswere (1.56±0.35)×10-3mm2/s,(1.40±0.34)×10-3mm2/s and (1.30±0.32)×10-3mm2/srespectively（P<0.05）. Compared with one another, there was statistically sinificantdifference between DWI(b=400s/mm2) and DWI(b=700s/mm2),DWI (b=400s/mm2) andDWI(b=1000s/mm2). there was no statistically sinificant difference between DWI(b=700s/mm2) and DWI(b=1000s/mm2).The areas under the ROC curves at b=400,700and1000s/mm2were0.799,0.866and0.867respectively. The ADC thresholds forpredicting malignancy were1.05×10-3、0.94×10-3and0.93×10-3mm2/s respectively.Sensitivity were65%,81%and81%，specificity were94.5%,91%and85%，Positivepredictive values were85%,80%and72%，negative predict values were85%,91%and90%,accuracy were85%,87%and84%,Youden index were0.60,0.72and0.66atb=400s/mm2,700s/mm2and1000s/mm2, respectively.6. The ADCRs of malignant orbital masses were (1.21±0.48),(1.04±0.43) and(1.05±0.50) on functional diffusion maps with b=400s/mm2,700s/mm2and1000s/mm2respectively. Compared with one another,there was no statistically sinificant difference（P=0.439）. TheADCRs of benign orbital masses were (1.60±0.37),(1.55±0.39) and(1.51±0.36) respectively. Compared with one another, there was no statistically sinificantdifference（P=0.191）.The areas under the ROC curves at b=400,700and1000s/mm2were0.764,0.844and0.845respectively. The ADCR thresholds for predicting malignancy were1.34,1.06and1.22respectively.Sensitivity were73%,77%and84%，specificity were80%,89%and81%，Positive predictive values were63%,77%and68%，negative predictvalues were86%,89%and92%,accuracy were78%,85%and82%,Youden index were0.53,0.66and0.66at b=400s/mm2,700s/mm2and1000s/mm2, respectively.7. The ADC and ADCR of lymphoma were lower than other orbital masses(metastasis and non-lymphoma orbital primary neoplasm,vascular orbital mass lesion,orbital benign tumor, orbital inflammatory disease). Compared with one another, there wasstatistically sinificant difference(P<0.05). Conclusions1. The SNR of the orbital masses,CNR between the masses and normal-appearing white matter and orbital masses ADCs decreased with the increase of bvalues.Combining SNR,CNR and ADCs in diagnosing benign and malignant orbitalmasses, the study indicated that b=700s/mm2was the optimal b value in orbital massDWI.2. The mean ADC and ADCR values of malignant orbital masses were lower thanthat of benign orbital masses.Apparent diffusion coefficient value is an additionalnoninvasive imaging parameter which can be used for distinguishing benign frommalignant orbital masses and the characterization of some orbital masses. Purposes1. To determine whether magnetic resonance imaging with dynamic contrast-enhanced imaging (DCE-MRI) can help discriminate between benign and malignantorbital masses.2. To determine whether DCE-MRI parameters and ADC value (b=700s/mm2) areconsistent with pathological examination and determine the value of adding ADCvalue to dynamic curve type when distinguishing between benign and malignantorbital masses.Materials and MethodsIn this study,67subjects(23males and44females) were enrolled.They underwent DWMR imaging and dynamic contrast-enhanced MRI using3D fast spoiled gradient echosequence at1.5MR unit(GE SIGNA EXCITE). The time-signal curves were deduced andclassified according to their appearances as type I(gradual enhancement),type II(plateauenhancement) and type III(washout enhancement).The five quantitative parametersincluding Tpeak,PH, ERmax,Slope and WR were analyzed in benign and malignant orbitalmasses.ADC threshold values were selected between benign and malignant masses.Independent-sample t test and Chi-square test were used for statistical analysis.P<0.05wasconsidered to indicate a significant difference.Results 1. There were45benign and22malignant orbital masses.The distribution ofcurve types for benign masses was type Ⅰ60%(27/45),type Ⅱ31%(14/45) and type Ⅲ8%(4/45).While the distribution of curve types for malignant masses was type I9%(2/22),type Ⅱ32%(7/22) and type Ⅲ59%(13/22).The patterns of curve types between benign andmalignant masses were statistically sinificant difference (χ2=23.527,P=0.000).2. The Tpeakvalue in benign masses was (152.96±107.49)s and that in malignantmasses was (39.90±50.82)s. There was statistically sinificantdifference(Z=-3.767,p=0.000)3. The PH value in benign masses was (294.00±92.14) and that in malignantmasses was (263.28±73.95). There was no statistically sinificant difference(t=-1.362,p=0.178).4. The ERmaxvalue in benign masses was (1.42±0.46) and that in malignantmasses was (1.23±0.47). There was no statistically sinificant difference(t=-1.694,p=0.095).5. The Slope value in benign masses was (2.36±2.65)%and that in malignantmasses was (4.44±2.69)%. There was statistically sinificant difference(Z=-3.178,p=0.001).6. The WR value in benign masses was (5.26±10.55)%and that in malignantmasses was (20.81±17.57)%. There was statistically sinificant difference(Z=-3.855,p=0.000).7. The areas under the ROC curves of Tpeak, Slope and WR were0.784,0.740and0.785respectively. The thresholds for predicting malignancy were83s,2.23%and9.37%respectively.Sensitivity were95%,81%and68%，specificity were60%,64%and82%，Positive predictive values were54%,52%and65%，negative predict values were96%,87%and84%,accuracy were72%,70%and77.6%,Youden index were0.55,0.46and0.50respectively.8. For comparison of Tpeakand pathological examination, Kappa=0.463,p<0.05.For comparison of Slope and pathological examination, Kappa=0.406,p<0.05. Forcomparison of WR and pathological examination, Kappa=0.498,p<0.05. For comparison ofADC700and pathological examination, Kappa=0.699,p<0.05.9. Adding ADC value to dynamic curve type when distinguishing betweenbenign and malignant orbital masses, Sensitivity,specificity,Positive predictive value,negative predict value, accuracy and Youden index was82%,91%,82%,91%,88%and0.73 respectively.Conclusions1. DCE-MRI is useful in distinguishing orbital malignant masses frombenign masses.2. DCE-MRI parameters(Tpeak、Slope、WR) andADC value (b=700s/mm2)are consistent with pathological examination.3. The value of adding ADC value to dynamic curve type whendistinguishing between benign and malignant orbital masses has higher specificity andpositive predictive value.