Study Of Magnetic Resonance Imaging In Orbital Neoplasms And Simulating Lesions

Imaging plays a vital role in the diagnosis and management of orbital neoplasmsand simulating lesions because it provides adequate information for the diagnosis andnecessary evidences for the treatment planning of orbital lesions.However,it can bedifficult to diagnose and differentially diagnose some orbital neoplasms andsimulating lesions.Therefore,our aim is to evaluate the value of static and dynamicgadopentetate dimeglumine-enhanced magnetic resonance (MR)imaging combinedwith nonenhanced MR imaging in the diagnosis and differential diagnosis of orbitalneoplasms and simulating lesions.The study is composed of three parts.Part 1 Orbital Masses in Adult Patients:Value of MagneticResonance Imaging in Prediction of MalignancyObjective:To prospectively evaluate static and dynamic gadopentetatedimeglumine-enhanced magnetic resonance (MR)imaging combined withnonenhanced MR imaging in differentiation of benign from malignant soft-tissuelesions in the orbit and to evaluate which MR imaging parameters are most predictiveof malignancy.Materials and methods:One hundred and two consecutive adult patients including51 male patients with mean age of 46 years and 51 female patients with mean age of54 years with a soft-tissue mass in the orbit underwent nonenhanced,static anddynamic gadopentetate dimeglumine-enhanced MR imaging.Diagnosis was based onhistologic findings in surgical specimens.The sensitivity and specificity of threemodels were compared,including combination of nonenhanced MR imaging,staticand dynamic enhancement MR imaging,combination of nonenhanced MR imagingand static enhancement MR imaging,and nonenhanced MR imaging alone.MRimaging parameters of benign and malignant soft-tissue lesions in the orbit wereevaluated correlated with histologic findings.Multivariate logistic regression analysiswas used to identify the best combination of MR imaging parameters that might bepredictive of malignancy.For subjective MR imaging diagnosis obtained withfive-point confidence rating scale,the sensitivity and specificity of combination ofnonenhanced MR imaging,static and dynamic enhancement MR imaging, combination of nonenhanced MR imaging and static enhancement MR imaging,andnonenhanced MR imaging alone were prospectively evaluated.Results:Benign lesions were demonstrated in 60 patients,and malignant lesions in42 patients.For both observers,location,shape,and margin of the lesion,moldingorbital structures,homogeneity on T₁-weighted imaging,signal intensity onT₂-weighted imaging,homogeneity on T₂-weighted imaging,pattern of enhancement,and a washout type time-signal intensity curve (TIC)were significantly differentbetween benign lesions and malignant lesions (p＜0.05).Multivariate logisticregression analysis identified the most discriminating MR imaging parameters wereisointensity on T₂-weighted imaging and a washout type TIC for both observers.Multivariate logistic regression analysis also revealed combination of nonenhancedMR imaging,static and dynamic enhancement MR imaging in prediction ofmalignancy with a sensitivity of 83.3% and a specificity of 88.3%,was significantlysuperior to nonenhanced MR imaging parameters combined with staticcontrast-enhanced MR imaging with a sensitivity of 78.6% and a specificity of 88.3%,and to nonenhanced MR imaging alone with a sensitivity of 78.6% and a specificityof 86.7%.For subjective MR imaging diagnosis obtained with five-point confidencerating scale,sensitivity and specificity of combination of nonenhanced MR imaging,static and dynamic enhancement MR imaging being 97.6% and 71.7%,respectively,were significantly higher than those of nonenhanced MR imaging parameterscombined with static contrast-enhanced MR imaging (sensitivity and specificity was81% and 58.3%,respectively),and nonenhanced MR imaging alone(sensitivity andspecificity was 81% and 58.3%,respectively)(p＜0.05).Conelusion:Static and dynamic gadopentetate dimeglumine--enhanced MR imagingcombined with nonenhanced MR imaging improved differentiation between benignand malignant neoplasms and simulation lesions in the orbit in adult patients.Anirregularly ill-defined mass,molding around orbital structures,isointensity onT₂-weighted imaging,or a washout type TIC was suggestive of malignant lesions,whereas a regularly well-defined mass,hypointensity on T₂-weighted imaging,peripheral enhancement,or persistent type TIC was indicative of benign lesions.Part two Value of Magnetic Resonance Imaging in the Differentiation of Orbital Cavernous Hemangiomas andSchwannomasObjective:To compare magnetic resonance (MR)imaging features of orbitalcavernous hemangiomas and schwannomas and evaluate MR imaging features in thedifferential diagnosis of the two lesions.Materials and methods:Nonenhanced,static and dynamic gadopentetatedimeglumine-enhanced MR imaging scanning was performed in forty-three patientswith orbital cavernous hemangiomas and sixteen patients with orbital schwannomasconfirmed by pathology from June of 2004 to January of 2009.MR imaging findingsof orbital cavernous hemangiomas and schwannomas were analysed retrospectivelyand compared.Results:There was significant difference between orbital cavernoushemangiomas and schwannomas in several MRI features including location,shape,signal intensity and homogeneity on T₁-weighted and T₂-weighted images,initialenhancement extent and enhancement pattern after contrast administration,time-signal intensity curve type,and relative contrast index of the lesion (p＜0.05).Conclusion:MR imaging features of orbital cavernous hemangiomas andschwannomas were different,which might contribute to differentiation of them.Enhancement of one point,two points or one portion in the early phase after contrastadministration and progressive filling of contrast media into the lesion could bereliable features in distinguishing between them.Part three Magnetic Resonance Imaging Findings of CavernousLymphangiomas in the OrbitObjective:MR imaging findings of cavernous lymphangiomas in the orbit wereevaluated.Methods:MR imaging findings including dynamic enhancement MR imagingscanning in 34 cases consisting of 30 females and 4 males with cavernouslymphangiomas in the orbit confirmed by histopathology were analyzedretrospectively.MR imaging findings of cavernous lymphangiomas were comparedwith those of cavernous hemangiomas as control.Results:Cavernous lymphangiomas were identified in the left orbit in 17 cases (50%) and in the right orbit in 17 cases (50%).A mass was observed in the intraconal spacein 20 cases (58.8%)and in the extraconal space in 14 cases (41.2%).The anteriororbit was involved in 25 cases (73.5%),the posterior orbit in 6 cases (17.7%),andboth the anterior orbit and posterior orbit in 3 cases (8.8%).MRI revealed an ovoidmass in 31 cases (91.2%)and a round mass in 3 cases (8.8%).The mass wasisointense on T₁WI and hyperintense on T₂WI in 34 cases (100%).Thirty-twopatients (94.1%)showed"progressive enhancement"pattern and two patients (5.9%)showed inhomogeneous enhancement on dynamic contrast enhancement MR imagingscanning.The time-signal intensity curve in 24 patients (70.6%)was characterized asa washout curve,the time-signal intensity curve in 8 patients (23.5%)wascharacterized as a plateau-shaped curve,and the time-signal intensity curve in 2patients (5.9%)was characterized as persistent.Compared with cavernoushemangiomas,cavernous lymphangiomas more frequently located in the extraconalspace (p=0.03)and occurred in female patients (p=0.03).Conclusion:MR imaging findings of orbital cavemous lymphangiomas are sosimilar to those of cavemous hemangiomas that it is difficult to differentiate thempreoperatively.However,cavernous lymphangioma should be included in the list ofthe diagnosis and differential diagnosis of an ovoid mass in the orbit demonstratingidentical T₁ and long T₂ signal intensity and'progressive enhancement'on dynamicenhancement MR imaging scanning.