Magnetic Resonance Imaging of Orbital Lymphangioma with and without Gadolinium Contrast Enhancement ]. Brent Bond, MD,l Barrett G. Haik, MD,l Jeffrey L. Taveras, MD, 2 Brian A Francis, BS,l Yuji Numaguchi, MD, 3 Futoshi Mihara, MD, 3 Kundan L. Gupta, MD4
Background: Lymphangioma is a vascular tumor of the orbit with a propensity for recurrent hemorrhage. These tumors may be difficult to diagnose in young patients who present with sudden proptosis due to hemorrhage into a previously unrecognized lesion. Magnetic resonance imaging (MRI) should be ideally suited for evaluating lymphangioma due to the unique ability of MRI to characterize hemorrhage because of the paramagnetic qualities of hemoglobin. Methods: The authors performed T 1 -, T 2 -, and proton density-weighted MRI on 12 patients with orbital lymphangioma. Six patients underwent MRI with gadolinium-DTPA contrast enhancement. The MRI studies were performed using a 1.5 Tesla super-conducting magnetic resonance unit, except for 3 early studies performed with a 0.5 Tesla unit. All studies were performed with orbital surface coil imaging. Computed tomography (CT) was performed in 1 0 patients. Results: Tumor was visible on MRI in all 12 patients. Magnetic resonance imaging delineated clearly the internal structure of subacute and chronic hemorrhagic cysts, and differentiated between these tumors because of the different paramagnetic qualities of subacute hemorrhage compared to chronic hemorrhage. In two patients, MRI detected large tumor feeding vessels by the flow void phenomenon unique to MRI. Computed tomography did not detect these vessels. Gadolinium-contrasted T 1 -weighted MRI did not further delineate or characterize the tumor. Conclusion: Magnetic resonance imaging is the modality of choice for imaging orbital lymphangioma because of its unequalled differentiation of hemorrhagic cysts, and its unique ability to detect tumor feeding vessels by the flow void phenomenon. Ophthalmology 1992;99: 1318-1324
Originally received: October 13, 1991. Revision accepted: February 17, 1992.
Presented at the American Academy of Ophthalmology Annual Meeting, Anaheim, October 1991.
1 Department of Ophthalmology, Tulane University Medical Center, New Orleans.
Supported in part by unrestricted grants from the St. Giles Foundation, Brooklyn, New York, and from Research to Prevent Blindness, Inc, New York, New York. Reprint requests to Barrett G Haik, MD, Department of Ophthalmology, Tulane University Medical Center, 1430 Tulane Ave, New Orleans, LA 70112.
2
Massachusetts Eye and Ear Infirmary, Boston.
3
Department of Diagnostic Radiology, University of Maryland School of Medicine, Baltimore. 4 Department of Radiology, Tulane University Medical Center, New Orleans.
1318
Bond et al · MRI of Orbital Lymphangioma Lymphangioma is a vascular tumor of the orbit often diagnosed in the first decade of life. Accurate diagnosis is difficult in young patients who present with sudden proptosis due to hemorrhage into a previously unrecognized lesion. These tumors may cause severe cosmetic or functional abnormalities due to extensive fibrovascular proliferation or recurrent hemorrhage. Treatment often requires surgery, which may be inadequate because the tumor tends to diffusely infiltrate the orbit. In certain cases, a needle aspiration of the hemorrhagic and lymphatic cysts may adequately debulk the tumor, saving the patient from undergoing more extensive orbital surgery. Successful needle aspiration requires that hemorrhagic cysts be identified as such, and the cystic component of the tumor be delineated clearly. We performed the following imaging studies to evaluate the ability of magnetic resonance imaging (MRI) to characterize fully the hemorrhagic and cystic components of orbital lymphangioma.
Subjects and Methods Twelve patients with orbital lymphangioma underwent T 1-, Tr, and proton density-weighted MRI. Six of these patients had MRI with gadolinium-DTPA contrast enhancement. Computed tomography (CT) was performed on 10 of the 12 patients. All patients underwent complete ophthalmologic examination, including B-scan ultrasonography. Orbital lymphangioma was diagnosed by characteristic clinical appearance on examination and with imaging, and was confirmed at orbitotomy in 11 cases. All patients were studied at the ocular oncology units of the Tulane Medical Center or the New York HospitalCornell Medical Center. The CT studies were performed using a General Electric 8800 unit (Milwaukee, WI) with 1.5-mm slice thickness orbital cuts. The MRI studies were performed using a General Electric 1.5 Tesla superconducting magnetic resonance unit, except for 3 early studies
performed on a Technicare (General Electric) 0.5-Tesla magnetic resonance unit. All studies were done with orbital surface coil imaging. All images were obtained with a 256 X 128 matrix, 18-cm field of view, and 2 excitations. Slice thickness was 3 mm with a 1.5-mm slice gap. Examination planes included axial, coronal, and oblique sagittal views. T 1-weighted images were obtained with a time of repetition (TR) of 500 to 600 msec and a time of echo (TE) of 20 to 30 msec. T 2-weighted images were obtained with a TR of 1700 to 2000 msec and a TE of 70 to 120 msec. Proton density-weighted images used a TR of 1700 to 2000 msec and aTE of 20 to 30 msec. The gadolinium-DTPA contrast was injected intravenously at a dose of 0.1 mmol per kilogram of body weight, and the gadolinium-contrasted images were obtained with T 1weighted sequencing.
Results Tumor was visible in 9 of the 10 patients undergoing CT (Table 1). The images showed homogeneous masses in six patients and nonhomogeneous masses in three patients. In one patient, a small superior orbital tumor was not detected with CT. Tumor was visible with MRI in all 12 patients. In 11 of the 12 patients, tumor was visible with both T 1- and T 2-weighted images (Fig 1). The only noncontrasted magnetic resonance images in which the tumor was not visible were the proton density-weighted images of the same tumor that was not detected with CT; however, the tumor was visible in both noncontrasted T 1- and Tr weighted images (Fig 2). In noncontrasted T 1-weighted images, tumor was predominantly hypointense in eight patients and hyperintense in four patients. In T 2-weighted images, all 12 tumors were predominantly hyperintense. In proton density-weighted images, tumor was predominantly hyperintense in nine patients, hypointense in two patients,
Table 1. Computed Tomography and Magnetic Resonance Imaging of Orbital Lymphangioma Patient No.
Computed Tomography
MRI T 1 • weighted
MRITz· weighted
MRIPDW
MRI Gadolinium
1 2 3
Homogeneous Homogeneous Homogeneous Not visible Not performed Homogeneous Inhomogeneous Inhomogeneous Inhomogeneous Homogeneous Not performed Homogeneous
Hypointense Hypointense Hyperintense Hyperintense Hypointense Hyperintense Hypointense Hypointense Hyperintense Hypointense Hypointense Hypointense
Hyperintense Hyperintense Hyperintense Hyperintense Hyperintense Hyperintense Hyperintense Hyperintense Hyperintense Hyperintense Hyperintense Hyperintense
Hyperintense Hyperintense Hyperintense Not visible Hypointense Hyperintense Hyperintense Hyperintense Hyperintense Hyperintense Hyperintense Hypointense ·
Not performed Not performed Not performed Not performed Hyperintense Not performed Hypointense Not performed Hyperintense Hypointense Hyperintense Hyperintense
4 5 6
7 8 9 10 11 12 MRI
=
magnetic resonance imaging; PDW
=
proton-density weighted images; Gadolinium
=
Gadolinium contrasted T -1 weighted images.
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Volume 99, Number 8, August 1992 and not visible in one patient. In two patients, a cystic tumor was hyperintense on both T 1- and T 2-weighted images (Fig 3). In one patient, the noncontrasted T 2-weighted image showed a fluid level in a cystic tumor, with the fluid portion of the cyst being hyperintense relative to the inferior part of the cyst (Fig 4). In one patient, a long-standing retrobulbar blood cyst had a very hypointense peripheral rim with a slightly hyperintense, almost isointense center on T 1-weighted images and a hyperintense center on T rweighted images. A medial portion of this tumor was hyperintense on both T 1- and T z-Weighted images (Fig 5). In two patients, significant arterialization within the tumor was easily identified on noncontrasted images but was not visible with CT (Fig 6). Six of the 12 patients underwent gadolinium-contrasted T 1-weighted imaging in addition to noncontrasted imaging. In two patients, the tumor did not enhance with gadolinium. In the other four patients, the tumor showed contrast enhancement increasing the intensity of the tumor. In one of these four patients, tumor enhanced to a degree to make it indistinguishable from the hyperintensity of the orbital fat (Fig 7). In each of the other three patients with enhancement after gadolinium, the tumor became more difficult to accurately delineate than in noncontrasted images.
Figure 1. A, axial Trweighted (TR 600 msec, TE 20 msec) image shows hypointense tumor. B, axial T 2-weighted (TR 1700 msec, TE 70 msec) image shows hyperintense tumor. C, axial proton-density weighted (TR 1700 msec, TE 20 msec) image shows hyperintense tumor with intensity between that of T 1- and T 2-weighted images.
Figure 2. A, axial T 1-weighted (TR 600 msec, TE 20 msec) image detects small hyperintense tumor next to globe in superior orbit. B, axial CT scan fails to detect tumor.
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Bond et al · MRI of Orbital Lymphangioma
Discussion In the last several years, the popularity of MRI in ophthalmology, as well as in other specialties, has continued to grow. This is largely due to its superiority over CT in providing soft tissue detail without using ionizing radiation, and in areas surrounded by bone. 1 Magnetic resonance imaging also can produce images in multiple planar orientations without the reformatting required by CT. Magnetic resonance imaging has superior capabilities to CT in these respects because its image production is unrelated to conventional x-ray attenuation, but is dependent on electromagnetic characteristics of hydrogen nuclei. The details of magnetic resonance are complex and have been extensively reviewed in the radiology literature. 2 •3 The development of the MRI contrast agent gadolinium-DTPA has heightened the value ofMRI in fully evaluating several ophthalmic entities. The effect of the paramagnetic contrast agent is to decrease the T 1 relaxation time, thus increasing the signal intensity ofT 1-weighted images. 4 •5 Gadolinium-contrasted MRI has proven valuable in evaluating optic nerve meningioma, 6 •7 and has been shown to increase the sensitivity of MRI for detecting and delineating am elan otic choroidal melanoma. 8 Orbital lymphangioma has been extensively reviewed in the literature, but these reports were of patients who
Figure 3. A, axial T 1-weighted (TR 600 msec, TE 20 msec) image shows hyperintense cystic tumor. B, axial T 2-weighted (TR 2000 msec, TE 70 msec) image shows hyperintense cystic tumor. C, axial CT scan shows retrobulbar tumor.
Figure 4. A, axial T 2-weighted (TR 2000 msec, TE 120 msec) image shows cystic tumor with hyperintense fluid level and less hyperintense dependent portion of tumor. B, axial CT scan shows homogeneous tumor without fluid level detection.
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Ophthalmology
Volume 99, Number 8, August 1992 was one patient in whom a small superior retrobulbar tumor was not visible but was clearly identifiable on other noncontrasted images. Because of the intermediate nature of proton density weighting, between that of T 1 and T 2
Figure 5. A, axial T 1-weighted (TR 600 msec, TE 20 msec) image shows slightly hyperintense, almost isointense, hemorrhagic cyst with markedly hypointense peripheral rim in retrobulbar region with hyperintense tumor medial to globe. B, axial T 2-weighted (TR 2000 msec, TE 70 msec) image shows hyperintense cyst with hypointense rim in retrobulbar region with hyperintense tumor medial to globe.
were evaluated before the widespread availability of MRI. 9 - 12 Orbital lymphangioma should be ideally suited for evaluation by MRI. Its internal structure of multiple cystic spaces lends itself nicely to the superior soft tissue differentiation of MRI, and its tendency to recurrent hemorrhage makes lymphangioma perfectly suited for the unique capability ofMRI to determine age of hemorrhage. This ability is due to the paramagnetic properties of the iron moiety of hemoglobin. As shown in Table 2, in acute hemorrhage, the oxyhemoglobin and deoxyhemoglobin result in T 1- and Trweighted images appearing hypointense. As the hemorrhage ages and the hemoglobin degrades into methemoglobin, the magnetic resonance images become hyperintense. With further aging, as the methemoglobin degrades into hemosiderin and ferritin, the hyperintensity on T 1- and Trweighted images gradually changes to hypointensity. 1• 13 Our results show that MRI provides optimal imaging of orbital lymphangioma. In all 12 patients, tumor was visible on MRI. On proton density-weighted images, there
1322
Figure 6. A, axial T 1-weighted (TR 600 msec, TE 20 msec) image shows markedly hypointense large caliber feeding V 14 days)
MRI
=
Biochemical State of Hemorrhage Deoxyhemoglobin in intact red blood cells Methemoglobin suspension with red blood cell lysis Hemosiderin and ferritin from degradation of methemoglobin
Trweighted
T 2-weighted
Hypointense Hyperintense
Hypointense Hyperintense
Hyperintense (slowly decreasing to hypointense)
Hyperintense (slowly decreasing to hypointense)
magnetic resonance imaging.
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Ophthalmology
Volume 99, Number 8, August 1992
Table 3. MRI Signal Intensity of Lymphangioma Components Lymphangioma Component
MRI T 1• weighted
MRI T 2• weighted
Lymphatic cysts Blood cysts, subacute Feeding vessels Stroma
Hypointense Hyperintense Hypointense Isointense
Hyperintense Hyperintense Hypointense Iso intense
MRI
=
magnetic resonance imaging.
portion of the tumor most likely represents subacute hemorrhage occurring at a more recent date than the retrobulbar part of the tumor. Two patients provided examples of ways other than hemorrhage characterization by which MRI can delineate internal structure oflymphangioma. In Figure 6, the MRI studies detect extensive arterialization of these large lymphangiomas, which is not shown with CT. These noncontrasted images delineate blood vessels by the unique magnetic resonance phenomenon of flow void imaging. Vessels containing rapidly flowing blood are imaged as areas of marked hypointensity. This occurs because the flowing blood that receives the magnetic resonance radio frequency excitation pulse already has moved out of the field by the time the magnetic field signal is read by the magnetic resonance unit, thus resulting in an area of no signal. Finally, in imaging our series of patients with lymphangioma, gadolinium-contrasted magnetic resonance did not appear to add information that was not provided by noncontrasted imaging. In two of the six patients who underwent gadolinium-contrasted imaging, the tumor did not enhance. In the other four patients, the tumor did enhance with contrast. However, this did not provide additional characterization of internal structure or identification of tumor components. Furthermore, the increase in intensity actually worsened the visualization of the tumor, making it approximate the hyperintensity of the surrounding orbital fat (Fig 7). In summary, MRI currently provides unequalled characterization of internal structure, detection of tumor feeding vessels, and localization of the cystic components of lymphangioma. We believe the images presented confirm MRI as the modality of choice for imaging orbital lymphangioma.
1324
References 1. Taveras JL, Haik BG. Magnetic Resonance Imaging in Ophthalmology. In: Masters BR, ed. Noninvasive Diagnostic Techniques in Ophthalmology. New York: Springer-Verlag, 1990; chap. 3. 2. Makow LS. Magnetic resonance imaging: a brief review of image contrast. Radio! Clin North Am 1989;27:195-218. 3. Pykett JL, Newhouse JH, Buonanno FS, et al. Principles of nuclear magnetic resonance imaging. Radiology 1982;143: 157-68. 4. Weinmann HJ, Brasch RC, Press W-R, Wesby GE. Characteristics of gadolinium-DTPA complex: a potential NMR contrast agent. AJR Am J Roentgenol 1984;142:619-24. 5. Carr DH, Brown J, Bydder GM, eta!. Gadolinum-DTPA as a contrast agent in MRI: initial clinical experience in 20 patients. AJR Am J Roentgenol 1984;143:215-24. 6. Haik BG, Zimmerman R, Saint Louis L. GadoliniumDTPA enhancement of an optic nerve and chiasma! meningioma. J Clin Neuro Ophthalmol 1989;9:122-5. 7. Zimmerman CF, Schatz NJ, Glaser JS. Magnetic resonance imaging of optic nerve meningiomas: enhancement with gadolinium-DTPA. Ophthalmology 1990;97 :585-91. 8. Bond JB, Haik BG, Mihara F, Gupta KL. Magnetic resonance imaging of choroidal melanoma with and without gadolinium contrast enhancement. Ophthalmology 1991 ;98: 459-66. 9. Jones IS. Lymphangiomas of the ocular adnexa. An analysis of sixty-two cases. Am J Ophthalmol1961;51:481-509. 10. IliffWJ, Green WR. Orbital lymphangiomas. Ophthalmology 1979;86:914-29. 11. Rootman J, Hay E, Graeb D, Miller R. Orbital-adnexal lymphangiomas: a spectrum of hemodynamically isolated vascular hamartomas. Ophthalmology 1986;93: 1558-70. 12. Harris GJ, Sakol PJ, Bonavolonta G, de Conciliis C. An analysis of thirty cases of orbital lymphangioma: pathophysiologic considerations and management recommendations. Ophthalmology 1990;97: 1583-92. 13. Thulbom KR, Atlas SW. Intracranial hemorrhage. In: Atlas SW, ed. Magnetic Resonance Imaging of the Brain and Spine. New York: Raven Press, 1991;185-203. 14. Bradley WG Jr, Schmidt PG. Effect of methemoglobin formation on the MR appearance of subarachnoid hemorrhage. Radiology 1985;156:99-103.
Background: Lymphangioma is a vascular tumor of the orbit with a propensity for recurrent hemorrhage. These tumors may be difficult to diagnose in young patients who present with sudden proptosis due to hemorrhage into a previously unrecognized lesion. Magnetic resonance imaging (MRI) should be ideally suited for evaluating lymphangioma due to the unique ability of MRI to characterize hemorrhage because of the paramagnetic qualities of hemoglobin. Methods: The authors performed T 1 -, T 2 -, and proton density-weighted MRI on 12 patients with orbital lymphangioma. Six patients underwent MRI with gadolinium-DTPA contrast enhancement. The MRI studies were performed using a 1.5 Tesla super-conducting magnetic resonance unit, except for 3 early studies performed with a 0.5 Tesla unit. All studies were performed with orbital surface coil imaging. Computed tomography (CT) was performed in 1 0 patients. Results: Tumor was visible on MRI in all 12 patients. Magnetic resonance imaging delineated clearly the internal structure of subacute and chronic hemorrhagic cysts, and differentiated between these tumors because of the different paramagnetic qualities of subacute hemorrhage compared to chronic hemorrhage. In two patients, MRI detected large tumor feeding vessels by the flow void phenomenon unique to MRI. Computed tomography did not detect these vessels. Gadolinium-contrasted T 1 -weighted MRI did not further delineate or characterize the tumor. Conclusion: Magnetic resonance imaging is the modality of choice for imaging orbital lymphangioma because of its unequalled differentiation of hemorrhagic cysts, and its unique ability to detect tumor feeding vessels by the flow void phenomenon. Ophthalmology 1992;99: 1318-1324
Originally received: October 13, 1991. Revision accepted: February 17, 1992.
Presented at the American Academy of Ophthalmology Annual Meeting, Anaheim, October 1991.
1 Department of Ophthalmology, Tulane University Medical Center, New Orleans.
Supported in part by unrestricted grants from the St. Giles Foundation, Brooklyn, New York, and from Research to Prevent Blindness, Inc, New York, New York. Reprint requests to Barrett G Haik, MD, Department of Ophthalmology, Tulane University Medical Center, 1430 Tulane Ave, New Orleans, LA 70112.
2
Massachusetts Eye and Ear Infirmary, Boston.
3
Department of Diagnostic Radiology, University of Maryland School of Medicine, Baltimore. 4 Department of Radiology, Tulane University Medical Center, New Orleans.
1318
Bond et al · MRI of Orbital Lymphangioma Lymphangioma is a vascular tumor of the orbit often diagnosed in the first decade of life. Accurate diagnosis is difficult in young patients who present with sudden proptosis due to hemorrhage into a previously unrecognized lesion. These tumors may cause severe cosmetic or functional abnormalities due to extensive fibrovascular proliferation or recurrent hemorrhage. Treatment often requires surgery, which may be inadequate because the tumor tends to diffusely infiltrate the orbit. In certain cases, a needle aspiration of the hemorrhagic and lymphatic cysts may adequately debulk the tumor, saving the patient from undergoing more extensive orbital surgery. Successful needle aspiration requires that hemorrhagic cysts be identified as such, and the cystic component of the tumor be delineated clearly. We performed the following imaging studies to evaluate the ability of magnetic resonance imaging (MRI) to characterize fully the hemorrhagic and cystic components of orbital lymphangioma.
Subjects and Methods Twelve patients with orbital lymphangioma underwent T 1-, Tr, and proton density-weighted MRI. Six of these patients had MRI with gadolinium-DTPA contrast enhancement. Computed tomography (CT) was performed on 10 of the 12 patients. All patients underwent complete ophthalmologic examination, including B-scan ultrasonography. Orbital lymphangioma was diagnosed by characteristic clinical appearance on examination and with imaging, and was confirmed at orbitotomy in 11 cases. All patients were studied at the ocular oncology units of the Tulane Medical Center or the New York HospitalCornell Medical Center. The CT studies were performed using a General Electric 8800 unit (Milwaukee, WI) with 1.5-mm slice thickness orbital cuts. The MRI studies were performed using a General Electric 1.5 Tesla superconducting magnetic resonance unit, except for 3 early studies
performed on a Technicare (General Electric) 0.5-Tesla magnetic resonance unit. All studies were done with orbital surface coil imaging. All images were obtained with a 256 X 128 matrix, 18-cm field of view, and 2 excitations. Slice thickness was 3 mm with a 1.5-mm slice gap. Examination planes included axial, coronal, and oblique sagittal views. T 1-weighted images were obtained with a time of repetition (TR) of 500 to 600 msec and a time of echo (TE) of 20 to 30 msec. T 2-weighted images were obtained with a TR of 1700 to 2000 msec and a TE of 70 to 120 msec. Proton density-weighted images used a TR of 1700 to 2000 msec and aTE of 20 to 30 msec. The gadolinium-DTPA contrast was injected intravenously at a dose of 0.1 mmol per kilogram of body weight, and the gadolinium-contrasted images were obtained with T 1weighted sequencing.
Results Tumor was visible in 9 of the 10 patients undergoing CT (Table 1). The images showed homogeneous masses in six patients and nonhomogeneous masses in three patients. In one patient, a small superior orbital tumor was not detected with CT. Tumor was visible with MRI in all 12 patients. In 11 of the 12 patients, tumor was visible with both T 1- and T 2-weighted images (Fig 1). The only noncontrasted magnetic resonance images in which the tumor was not visible were the proton density-weighted images of the same tumor that was not detected with CT; however, the tumor was visible in both noncontrasted T 1- and Tr weighted images (Fig 2). In noncontrasted T 1-weighted images, tumor was predominantly hypointense in eight patients and hyperintense in four patients. In T 2-weighted images, all 12 tumors were predominantly hyperintense. In proton density-weighted images, tumor was predominantly hyperintense in nine patients, hypointense in two patients,
Table 1. Computed Tomography and Magnetic Resonance Imaging of Orbital Lymphangioma Patient No.
Computed Tomography
MRI T 1 • weighted
MRITz· weighted
MRIPDW
MRI Gadolinium
1 2 3
Homogeneous Homogeneous Homogeneous Not visible Not performed Homogeneous Inhomogeneous Inhomogeneous Inhomogeneous Homogeneous Not performed Homogeneous
Hypointense Hypointense Hyperintense Hyperintense Hypointense Hyperintense Hypointense Hypointense Hyperintense Hypointense Hypointense Hypointense
Hyperintense Hyperintense Hyperintense Hyperintense Hyperintense Hyperintense Hyperintense Hyperintense Hyperintense Hyperintense Hyperintense Hyperintense
Hyperintense Hyperintense Hyperintense Not visible Hypointense Hyperintense Hyperintense Hyperintense Hyperintense Hyperintense Hyperintense Hypointense ·
Not performed Not performed Not performed Not performed Hyperintense Not performed Hypointense Not performed Hyperintense Hypointense Hyperintense Hyperintense
4 5 6
7 8 9 10 11 12 MRI
=
magnetic resonance imaging; PDW
=
proton-density weighted images; Gadolinium
=
Gadolinium contrasted T -1 weighted images.
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Volume 99, Number 8, August 1992 and not visible in one patient. In two patients, a cystic tumor was hyperintense on both T 1- and T 2-weighted images (Fig 3). In one patient, the noncontrasted T 2-weighted image showed a fluid level in a cystic tumor, with the fluid portion of the cyst being hyperintense relative to the inferior part of the cyst (Fig 4). In one patient, a long-standing retrobulbar blood cyst had a very hypointense peripheral rim with a slightly hyperintense, almost isointense center on T 1-weighted images and a hyperintense center on T rweighted images. A medial portion of this tumor was hyperintense on both T 1- and T z-Weighted images (Fig 5). In two patients, significant arterialization within the tumor was easily identified on noncontrasted images but was not visible with CT (Fig 6). Six of the 12 patients underwent gadolinium-contrasted T 1-weighted imaging in addition to noncontrasted imaging. In two patients, the tumor did not enhance with gadolinium. In the other four patients, the tumor showed contrast enhancement increasing the intensity of the tumor. In one of these four patients, tumor enhanced to a degree to make it indistinguishable from the hyperintensity of the orbital fat (Fig 7). In each of the other three patients with enhancement after gadolinium, the tumor became more difficult to accurately delineate than in noncontrasted images.
Figure 1. A, axial Trweighted (TR 600 msec, TE 20 msec) image shows hypointense tumor. B, axial T 2-weighted (TR 1700 msec, TE 70 msec) image shows hyperintense tumor. C, axial proton-density weighted (TR 1700 msec, TE 20 msec) image shows hyperintense tumor with intensity between that of T 1- and T 2-weighted images.
Figure 2. A, axial T 1-weighted (TR 600 msec, TE 20 msec) image detects small hyperintense tumor next to globe in superior orbit. B, axial CT scan fails to detect tumor.
1320
Bond et al · MRI of Orbital Lymphangioma
Discussion In the last several years, the popularity of MRI in ophthalmology, as well as in other specialties, has continued to grow. This is largely due to its superiority over CT in providing soft tissue detail without using ionizing radiation, and in areas surrounded by bone. 1 Magnetic resonance imaging also can produce images in multiple planar orientations without the reformatting required by CT. Magnetic resonance imaging has superior capabilities to CT in these respects because its image production is unrelated to conventional x-ray attenuation, but is dependent on electromagnetic characteristics of hydrogen nuclei. The details of magnetic resonance are complex and have been extensively reviewed in the radiology literature. 2 •3 The development of the MRI contrast agent gadolinium-DTPA has heightened the value ofMRI in fully evaluating several ophthalmic entities. The effect of the paramagnetic contrast agent is to decrease the T 1 relaxation time, thus increasing the signal intensity ofT 1-weighted images. 4 •5 Gadolinium-contrasted MRI has proven valuable in evaluating optic nerve meningioma, 6 •7 and has been shown to increase the sensitivity of MRI for detecting and delineating am elan otic choroidal melanoma. 8 Orbital lymphangioma has been extensively reviewed in the literature, but these reports were of patients who
Figure 3. A, axial T 1-weighted (TR 600 msec, TE 20 msec) image shows hyperintense cystic tumor. B, axial T 2-weighted (TR 2000 msec, TE 70 msec) image shows hyperintense cystic tumor. C, axial CT scan shows retrobulbar tumor.
Figure 4. A, axial T 2-weighted (TR 2000 msec, TE 120 msec) image shows cystic tumor with hyperintense fluid level and less hyperintense dependent portion of tumor. B, axial CT scan shows homogeneous tumor without fluid level detection.
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Ophthalmology
Volume 99, Number 8, August 1992 was one patient in whom a small superior retrobulbar tumor was not visible but was clearly identifiable on other noncontrasted images. Because of the intermediate nature of proton density weighting, between that of T 1 and T 2
Figure 5. A, axial T 1-weighted (TR 600 msec, TE 20 msec) image shows slightly hyperintense, almost isointense, hemorrhagic cyst with markedly hypointense peripheral rim in retrobulbar region with hyperintense tumor medial to globe. B, axial T 2-weighted (TR 2000 msec, TE 70 msec) image shows hyperintense cyst with hypointense rim in retrobulbar region with hyperintense tumor medial to globe.
were evaluated before the widespread availability of MRI. 9 - 12 Orbital lymphangioma should be ideally suited for evaluation by MRI. Its internal structure of multiple cystic spaces lends itself nicely to the superior soft tissue differentiation of MRI, and its tendency to recurrent hemorrhage makes lymphangioma perfectly suited for the unique capability ofMRI to determine age of hemorrhage. This ability is due to the paramagnetic properties of the iron moiety of hemoglobin. As shown in Table 2, in acute hemorrhage, the oxyhemoglobin and deoxyhemoglobin result in T 1- and Trweighted images appearing hypointense. As the hemorrhage ages and the hemoglobin degrades into methemoglobin, the magnetic resonance images become hyperintense. With further aging, as the methemoglobin degrades into hemosiderin and ferritin, the hyperintensity on T 1- and Trweighted images gradually changes to hypointensity. 1• 13 Our results show that MRI provides optimal imaging of orbital lymphangioma. In all 12 patients, tumor was visible on MRI. On proton density-weighted images, there
1322
Figure 6. A, axial T 1-weighted (TR 600 msec, TE 20 msec) image shows markedly hypointense large caliber feeding V 14 days)
MRI
=
Biochemical State of Hemorrhage Deoxyhemoglobin in intact red blood cells Methemoglobin suspension with red blood cell lysis Hemosiderin and ferritin from degradation of methemoglobin
Trweighted
T 2-weighted
Hypointense Hyperintense
Hypointense Hyperintense
Hyperintense (slowly decreasing to hypointense)
Hyperintense (slowly decreasing to hypointense)
magnetic resonance imaging.
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Volume 99, Number 8, August 1992
Table 3. MRI Signal Intensity of Lymphangioma Components Lymphangioma Component
MRI T 1• weighted
MRI T 2• weighted
Lymphatic cysts Blood cysts, subacute Feeding vessels Stroma
Hypointense Hyperintense Hypointense Isointense
Hyperintense Hyperintense Hypointense Iso intense
MRI
=
magnetic resonance imaging.
portion of the tumor most likely represents subacute hemorrhage occurring at a more recent date than the retrobulbar part of the tumor. Two patients provided examples of ways other than hemorrhage characterization by which MRI can delineate internal structure oflymphangioma. In Figure 6, the MRI studies detect extensive arterialization of these large lymphangiomas, which is not shown with CT. These noncontrasted images delineate blood vessels by the unique magnetic resonance phenomenon of flow void imaging. Vessels containing rapidly flowing blood are imaged as areas of marked hypointensity. This occurs because the flowing blood that receives the magnetic resonance radio frequency excitation pulse already has moved out of the field by the time the magnetic field signal is read by the magnetic resonance unit, thus resulting in an area of no signal. Finally, in imaging our series of patients with lymphangioma, gadolinium-contrasted magnetic resonance did not appear to add information that was not provided by noncontrasted imaging. In two of the six patients who underwent gadolinium-contrasted imaging, the tumor did not enhance. In the other four patients, the tumor did enhance with contrast. However, this did not provide additional characterization of internal structure or identification of tumor components. Furthermore, the increase in intensity actually worsened the visualization of the tumor, making it approximate the hyperintensity of the surrounding orbital fat (Fig 7). In summary, MRI currently provides unequalled characterization of internal structure, detection of tumor feeding vessels, and localization of the cystic components of lymphangioma. We believe the images presented confirm MRI as the modality of choice for imaging orbital lymphangioma.
1324
References 1. Taveras JL, Haik BG. Magnetic Resonance Imaging in Ophthalmology. In: Masters BR, ed. Noninvasive Diagnostic Techniques in Ophthalmology. New York: Springer-Verlag, 1990; chap. 3. 2. Makow LS. Magnetic resonance imaging: a brief review of image contrast. Radio! Clin North Am 1989;27:195-218. 3. Pykett JL, Newhouse JH, Buonanno FS, et al. Principles of nuclear magnetic resonance imaging. Radiology 1982;143: 157-68. 4. Weinmann HJ, Brasch RC, Press W-R, Wesby GE. Characteristics of gadolinium-DTPA complex: a potential NMR contrast agent. AJR Am J Roentgenol 1984;142:619-24. 5. Carr DH, Brown J, Bydder GM, eta!. Gadolinum-DTPA as a contrast agent in MRI: initial clinical experience in 20 patients. AJR Am J Roentgenol 1984;143:215-24. 6. Haik BG, Zimmerman R, Saint Louis L. GadoliniumDTPA enhancement of an optic nerve and chiasma! meningioma. J Clin Neuro Ophthalmol 1989;9:122-5. 7. Zimmerman CF, Schatz NJ, Glaser JS. Magnetic resonance imaging of optic nerve meningiomas: enhancement with gadolinium-DTPA. Ophthalmology 1990;97 :585-91. 8. Bond JB, Haik BG, Mihara F, Gupta KL. Magnetic resonance imaging of choroidal melanoma with and without gadolinium contrast enhancement. Ophthalmology 1991 ;98: 459-66. 9. Jones IS. Lymphangiomas of the ocular adnexa. An analysis of sixty-two cases. Am J Ophthalmol1961;51:481-509. 10. IliffWJ, Green WR. Orbital lymphangiomas. Ophthalmology 1979;86:914-29. 11. Rootman J, Hay E, Graeb D, Miller R. Orbital-adnexal lymphangiomas: a spectrum of hemodynamically isolated vascular hamartomas. Ophthalmology 1986;93: 1558-70. 12. Harris GJ, Sakol PJ, Bonavolonta G, de Conciliis C. An analysis of thirty cases of orbital lymphangioma: pathophysiologic considerations and management recommendations. Ophthalmology 1990;97: 1583-92. 13. Thulbom KR, Atlas SW. Intracranial hemorrhage. In: Atlas SW, ed. Magnetic Resonance Imaging of the Brain and Spine. New York: Raven Press, 1991;185-203. 14. Bradley WG Jr, Schmidt PG. Effect of methemoglobin formation on the MR appearance of subarachnoid hemorrhage. Radiology 1985;156:99-103.
