|Year : 2014 | Volume
| Issue : 2 | Page : 159-163
Role of GRE imaging in cerebral diseases with hemorrhage: A case series
Kamini Gupta1, Puneet Mittal2, Ranjana Gupta2, Archana Ahluwalia1
1 Department of Radiodiagnosis, Dayanand Medical College and Hospital, Ludhiana, Punjab, India
2 Department of Radiodiagnosis, Maharishi Markendeshwar Institute of Medical Sciences and Research, Mullana, Haryana, India
|Date of Web Publication||11-Aug-2014|
Department of Radiodiagnosis, Dayanand Medical College and Hospital, Ludhiana, Punjab
Source of Support: None, Conflict of Interest: None
Gradient recalled echo (GRE) T2 weighted imaging is more widely used as a standard magnetic resonance (MR) pulse sequence because of its exquisite sensitivity for detection of cerebral hemorrhages. Signal loss on GRE sequence is due to increased sensitivity of this sequence to magnetic susceptibility induced by static field inhomogeneities arising from paramagnetic blood breakdown products. T2 * signal intensity loss seen in GRE sequence is greater with longer TE, smaller flip angle, and larger magnetic field strength. The purpose of this review is to discuss the role of GRE imaging in cerebral disorders with bleed. Because of the sensitivity of this sequence to microbleeds, we describe its edge over baseline imaging sequences to provide insight in the etiology of certain diseases.
Keywords: Echo, gradient, hemorrhage, MRI
|How to cite this article:|
Gupta K, Mittal P, Gupta R, Ahluwalia A. Role of GRE imaging in cerebral diseases with hemorrhage: A case series. J Mahatma Gandhi Inst Med Sci 2014;19:159-63
|How to cite this URL:|
Gupta K, Mittal P, Gupta R, Ahluwalia A. Role of GRE imaging in cerebral diseases with hemorrhage: A case series. J Mahatma Gandhi Inst Med Sci [serial online] 2014 [cited 2020 May 27];19:159-63. Available from: http://www.jmgims.co.in/text.asp?2014/19/2/159/138445
| Introduction|| |
Conventional magnetic resonance imaging (MRI) sequences have inherent low resolution for detection of hemorrhage, which can be enhanced by addition of GRE imaging. Paramagnetic compounds such as deoxyhemoglobin, intracellular methemoglobin, and hemosiderin can produce significant signal loss on GRE sequence secondary to locally non-uniform magnetic fields, resulting in a rapid dephasing of proton spins. This effect is more marked in GRE sequence secondary to lack of the 180 degree refocusing pulse used in conventional spin echo sequences. GRE is very sensitive to the detection of blood products due to the presence of paramagnetic substances in them. We present a series of five cases, wherein we describe the importance of GRE sequence over basic MRI sequences in reaching to the correct diagnosis, confirming it, and providing clues to the etiopathogenesis.
In all cases, GRE was performed on an 18-channel, 1.5 Tesla scanner (Avanto, Siemens, Erlangen, Germany) using the following parameters:- time to repetition (TR)-760 ms, time to echo (TE)-26 ms, flip angle-20°, slice thickness-3 mm, bandwidth-80 kHz, field of view (FOV) read-230 mm, FOV phase-87.5%, base resolution-256, phase resolution-75%, and integrated parallel acquisition technique (IPAT) factor-2.
A 57-years-old male presented with sudden unconsciousness following severe headache. He was not on any anticoagulant or aspirin therapy. His routine MRI brain revealed a large area of hemorrhage in right parietal lobe. It appeared iso to hypointense on T1W [Figure 1]a] and heterogeneously hyperintense on T2W sequences [Figure 1]b]. On GRE images, it appeared markedly hypointense and showed blooming. In addition, multiple tiny microhemorrhages were seen at gray-white matter interface on GRE sequence [Figure 1]c], which were not seen on other routine fast spin echo images. Based on these findings, diagnosis of amyloid angiopathy was made, which was confirmed by subsequent biopsy.
|Figure 1: Axial T1W (a) and T2W (b) images shows poorly marginated lesion with heterogeneous mixed signal in right parietal region (arrows) Axial GRE (c) image confirms its hemorrhagic nature (black thick arrow). It also shows multiple microbleeds at gray-white matter junction (white arrows) supporting the diagnosis of amyloid angiopathy|
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A 34-years-old female came for MRI brain with chief complaint of headache for 24 hours. She was taking oral contraceptive pills for past four years. Small linear hyperintense area was seen in right frontal region on diffusion-weighted images [Figure 2]a], which was hyperintense on apparent diffusion coefficient (ADC) mapping suggesting sub-acute infarct. On GRE images, superior sagittal sinus and cortical veins in high parietal regions showed blooming [Figure 2]b]. MR venography confirmed sinus thrombosis [Figure 2]c].
|Figure 2: Axial diffusion weighted image (a) shows linear hyperintense area in right frontal region (marked with circle) with no evidence of diffusion restriction on ADC mapping (not shown) Axial GRE image (b) shows hypointense signal with blooming in superior sagittal sinus and in cortical veins in bilateral parietal regions (white arrows) TOF MRV (c) confirms venous sinus thrombosis as absence of flow-related enhancement in superior sagittal sinus (white arrow).|
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A 29-years-old female, a follow up case of choriocarcinoma, came in altered sensorium in the emergency. MRI revealed T2W hyperintense signal in right high frontoparietal region in parafalcine location [Figure 3]a]. Irregular hypointense areas were also seen at places. On T1W post-contrast images, irregular nodular and sheet-like enhancement was seen [Figure 3]b]. However, on GRE images, hypointense rim was seen around this lesion, which suggested the presence of hemorrhage [Figure 3]c]. Hemorrhagic nature of lesions further confirmed them to be metastases of choriocarcinoma.
|Figure 3: Axial T2W (a) image shows heterogeneously hyperintense lesion in right fronto-parietal region in parafalcine location (black arrow) Post-contrast T1W (b) image shows irregular nodular enhancement in anterior portion of the lesion (white arrow) Axial GRE (c) image shows large areas of peripheral blooming due to hemosiderin rim (black arrow) confirming the presence of hemorrhage, thus supporting the diagnosis of hemorrhagic choriocarcinoma metastases.|
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A 38-years-old male presented for MRI with history of mild headache off and on. MRI brain revealed a well-defined lesion in right frontal region with mixed hypo and hyperintense central signal on T1W [Figure 4]a] and T2W images and surrounding hypointense rim on T2W images [Figure 4]b] indicating blood products, which was confirmed on GRE images [Figure 4]c], which showed blooming of the lesion, thus confirming the diagnosis of cavernous angioma.
A 38-years-old male had history of mild headache off and on. His MRI brain revealed hyperintense signal in sub-cortical and deep white matter in right frontal lobe on axial T2W [Figure 5]a] and FLAIR [Figure 5]b] images. Two thin linear flow voids were also seen. On GRE images, a focal ill marginated hypointense area was seen in sub-cortical and deep white matter [Figure 5]c], which suggested a venous angioma.
|Figure 4: Axial T1W (a) and T2W (b) images show well-defined lesion with mixed hypo and hyperintense signal in right frontal region with hypointense rim (white arrows) Axial GRE (c) image shows marked blooming (black arrow), thus confirming the diagnosis of cavernous angioma.|
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|Figure 5: Axial T2W (a) and FLAIR (b) images show subtle hyperintense lesion in sub-cortical and deep white matter in right frontal lobe with linear flow voids (encircled). Axial GRE (c) at same level shows marked blooming in this entire area, suggesting bunch of medullary veins (encircled), thus confirming it to be venous angioma|
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| Discussion|| |
GRE is T2 * -based sequence, which is extremely sensitive to local magnetic field inhomogeneity and is especially useful for detection of microhemorrhages, which may be undetectable by other sequences. Microbleeds are usually defined as cerebral bleeds less than 5-10 mm in size, and they are now thought to represent microangiopathy with consequent prognostic implications. ,
Amyloid angiopathy results from accumulation of beta-amyloid in the walls of small arteries, which cause vascular fragility making them prone to repeated hemorrhage. It is an important but under-recognized cause of cerebral hemorrhage in normotensive elderly population. A definitive diagnosis requires post-mortem pathological analysis. However, a diagnosis of probable amyloid angiopathy can be made in presence of appropriate clinical picture and imaging findings. Occasionally, biopsy is performed to exclude any alterative diagnosis as was done in our case. In these cases, if pathological findings reveal amyloid angiopathy, then diagnosis of probable amyloid angiopathy with supporting pathological evidence is made. , While lobar hemorrhages can be detected on conventional imaging, GRE images help to confirm the hemorrhagic nature of the lesions and also help to detect associated microhemorrhages at gray-white matter interface, which are helpful in the diagnosis in appropriate clinical settings [Figure 1]. Also, the number of microhemorrhages correlates with underlying neurological deficit and with risk of lobar hemorrhage in the future. 
Cerebral venous thrombosis is a rare but serious condition and requires prompt diagnosis for proper management and to avoid serious complications. The signal intensity of thrombus on conventional MRI sequences depends upon the stage of hemorrhage. In acute phases, the thrombus is isointense on T1W and hypointense on T2W images, which can be easily dismissed as normal flow void on T2W images.  In this stage, GRE images are extremely helpful to demonstrate the blooming within the sinus or cortical veins, which helps to confirm the diagnosis as in our case [Figure 2b]. GRE is also useful for diagnosis of cortical venous thrombosis, which can be difficult to detect on time of flight (TOF) magnetic resonance venography (MRV).
Hemorrhagic brain metastasis can be secondary to renal cell carcinoma, malignant melanoma, choriocarcinoma, and acute leukemias.  GRE is useful in demonstrating the hemorrhagic nature of these lesions, which helps to narrow down the diagnosis. Hemorrhages are common complication of acute leukemias in children and often indicate poor prognosis. 
Cavernous angiomas represent low flow type of vascular malformations, which often have characteristic imaging features mixed signal blood products bounded by a hypointense hemosiderin rim. GRE images are useful in confirming the diagnosis and are also useful for demonstrating multifocal nature of lesions, which may be inconspicuous on other imaging sequences. On GRE, small cavernous angiomas are seen as small areas of blooming and are frequently indistinguishable from microbleeds. ,
Venous angioma of the brain consists of multiple, radially oriented, dilated medullary veins that drain into a transparenchymal venous stem. On MR images, venous angiomas characteristically have a transhemispheric flow void on both T1- and T2-weighted images.
In complicated venous angioma, associated hemorrhage, cavernous angioma, or exceptionally, non-hemorrhagic venous infarction may be seen.  GRE images can suggest the diagnosis as the characteristic pattern of radially arranged medullary veins can be seen as in our case draining into subependymal vein, thus obviating the need of angiography or contrast-enhanced MRI.
GRE sequence is made T2 * -weighted by using a low flip angle, long TE, and long TR. However, T2 * values are always shorter than the underlying T2 values. Thus, what is often considered a long TE for T2 * -weighted sequence is often much shorter than that used for T2-weighted spin echo sequences. Absence of 180 pulse and use of small flip angle also make it a fast sequence. Hence, GRE can be done in all the patients suspected of brain hemorrhage without much prolongation of scan time. 
One of the pitfalls of GRE sequence is that magnetic field inhomogeneities from susceptibility differences among tissues and materials like a tissue-air interface and due to metallic implants can cause geometric distortions, leading to signal intensity artefacts, about which one should be aware while interpreting the images. 
| Conclusion|| |
GRE MR sequence is the most sensitive for the detection of intracranial hemorrhage as compared with other MR sequences. GRE sequence must be included in the protocol of evaluation of intracranial hemorrhage, as the detection of small/chronic microbleeds with this sequence can provide a clue to the etiology of hemorrhage.
| Acknowledgement|| |
Deptt. of Neurology and Neurosurgery, Dayanand Medical College and Hospital, Ludhiana for referral of clinical cases.
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