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T2 Gradient Echo Sequence Versus Susceptibility-Weighted Angiography Sequence in Detecting Microhemorrhages in Hypertensive Patients

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ARTÍCULO ORIGINAL Anales de Radiología México 2016 Apr;15(2):94-102. T2 gradient echo sequence versus susceptibility-weighted angiography sequence in detecting microhemorrhages in hypertensive patients. Torres-Gómez E1, Onofre-Castillo JJ2, Santana-Vela IA1, Hernández-Salazar JJ3, García-Concha A4, Martínez-Aparicio JS4, Cuituny-Romero AK1 Abstract INTRODUCTION: cerebral microhemorrhages are deposits of hemosiderin in small blood vessels produced by microangio- pathic processes and represent a risk for the development of strokes; in magnetic resonance they appear as rounded focal areas with lack of signal. OBJECTIVE: compare T2 gradient echo and SWAN (suscepti- bility-weighted angiography) magnetic resonance sequences in describing cerebral microhemorrages in hypertensive patients. MATERIAL AND METHODS: a transverse, descriptive, obser- 1Médico Especialista en Radiología e Imagen. vational study in a group of hypertensive patients admitted to 2Médico Especialista en Radiología e Imagen, Profe- Hospital Christus Muguerza Alta Especialidad de Monterrey and sor Titular y Asesor del Departamento de Radiología. 3Residente de cuarto año de Imagenología Diag- who underwent magnetic resonance. nóstica y Terapéutica. 4Residente de tercer año de Imagenología Diag- nóstica y Terapéutica. RESULTS: fifty-seven patients were included (35 men and 22 women) with mean age of 63 years. Seventeen had microhe- Departamento de Radiología e Imagen del Hospital Christus Muguerza Alta Especialidad, Hidalgo 2525, morrhages detected with susceptibility-weighted angiography Col. Obispado, C.P. 64060, Monterrey, N.L. (SWAN) sequence and 15 with T2 gradient echo sequence, the majority with lobar localization. On comparing the procedures Received: May 10, 2016 one-to-one, the SWAN showed a larger number of microhemor- Accepted: May 14, 2016 rhages. Correspondence Enrique Torres-Gómez CONCLUSION: both sequences are useful to detect the pres- [email protected] ence, localization, and degree of cerebral microhemorrhages, but the susceptibility-weighted angiography sequence proved to be This article must be quoted as Torres-Gómez E, Onofre-Castillo JJ, Santana-Vela IA, more useful in detecting the total number of microhemorrhages. Hernández-Salazar JJ, García-Concha A, Martínez- Aparicio JS et al. Secuencia T2 eco de gradiente KEYWORDS: microhemorrhages; magnetic resonance; high versus secuencia ponderada de susceptibilidad angiológica en la detección de microhemorragias en blood pressure; T2 gradient echo; susceptibility-weighted angi- pacientes hipertensos. Anales de Radiología México ography sequence 2016;15(2):94-102. 94 www.nietoeditores.com.mx Torres-Gómez E, et al. Screening of microhemorrhages in hypertensive patients INTRODUCTION transformation after an ischemic vascular event and with recurrence of spontaneous intracerebral Cerebral microhemorrhages are hemosiderin bleeds. There are also controversial results that deposits in the brain due to red blood cell leaks suggest that cerebral microhemorrhages involve in small blood vessels without any symptoms. an increased risk for bleeding complications Cerebral microbleeds are neuroimaging findings from thrombolytic therapy or the use of platelet defined as small areas with void signal on MRI agents.8 imaging as a consequence of old bleeding foci.1 They are thought to be the result of microangio- Hemosiderin deposits lead to a lack of uniformity pathic processes either from atherosclerosis or in the areas where the lesions are found, leading fibrohyalinosis or from amyloid cerebral angi- to a signal breakdown in MRI (called magnetic opathy. The main contributors of these lesions susceptibility effect) so there is a signal loss or are cardiovascular risk factors, underlying ac- low intensity areas.9 In magnetic resonance im- tive angiopathy disease mechanisms or perhaps aging, cerebral microhemorrhages are defined as changes due to aging. multiple oval or circular foci with a substantial loss of signal in T2 weighted images,10-12 mainly Previous reports have shown that the number of in echo-gradient sequences that have proven a microhemorrhages is associated to the severity of higher sensitivity for detection of old bleedings changes in the white matter and with the number compared to conventional spin-echo sequences; of lacunar infarcts, believed to happen as a result such images should always be differentiated from of small vessel disease in the brain.2 Walker et bloodflow voids and calcifications in the brain. al3 found evidence of microhemorrhages with cortical-subcortical distribution, a characteristic Concerning size, the criteria have been incon- feature in 15.5% of patients over 70 years of age. sistent and most of the studies indicate that There is substantial evidence that supports an im- microhemorrhages tend to be smaller than 5 mm portant association between microhemorrhages or, 10 mm as the upper limit.7,10 Traditionally, and hypertensive and atherosclerotic vasculopa- echo-gradient T2 weighted sequence has been thy. These lesions are found in more than 71% used for detection of microhemorrhages; howev- of individuals that present with intracerebral er, Haacke and his group13 presented a resonance hemorrhage and in 20 to 68% of patients that sequence called susceptibility weighted image are admitted with an ischemic event.2,4-6 and called it (SWI) to further improve the effect of T2 weighted sequences using detection and Talking specifically about cerebral hyperten- measurement of iron and other substances that sive angiopathy, which is caused by intimal alter the magnetic field.14 This sequence provides hyperplasia and hyalinosis in the deep cerebral information of any tissue that has a different sus- arteriolar branches as a result of hypertension, ceptibility in its surrounding structures such as it involves pathophysiologic changes that lead deoxygenated blood, hemosiderin, ferritin and to cerebral microhemorrhages, mainly in the calcium. There are multiple neurologic disorders thalamus, basal ganglia, cerebellum and pons.7 in which we can dramatically benefit from this Based on these findings, it is postulated that ce- highly sensitive method to monitor the amount rebral microhemorrhages are an important risk of iron in the brain, either as deoxyhemoglobin, factor for a subsequent intracerebral hematoma. ferritin or hemosiderin. Such sequence has the Also, microhemorrhages have been found to be peculiarity of being able to present the data with associated with a greater risk of hemorrhagic maximal or minimal projection intensity (MIP/ 95 Anales de Radiología México 2016 abril;15(2) MinIP) in a given image, to get a better assess- cooperate and whose images were suboptimal ment of the vascular tracts. for proper evaluation and interpretation. The General Electric units offer susceptibility The evaluation using the sequences mentioned weighted image (SWI) and call it susceptibility above was done at the Hospital Christus Mu- weighted angiography (SWAN), that helps to guerza Alta Especialidad, with a General Electric clearly outline the small blood vessels, micro- Healthcare MRI scanner, Signa HDx model, 3 hemorrhages and large vascular structures in the tesla, with trained radiologists having over two brain, aside from visualizing iron and calcium years experience, and obtaining the sequences deposits due to the paramagnetic properties according to the standardized protocols (Ta- already mentioned.15 ble 1). Echo-gradient T2 weighted sequences and susceptibility weighted angiography sequences Timely detection of microhemorrhages in hy- (SWAN) were obtained from all the participants, pertensive patients plays an important role in from the skull base to the convexity of both brain the prognosis and probability of ischemic event hemispheres. risk with probable hemorrhagic transformation or a new hemorrhagic vascular event in patients Table 1. MRI sequence parameters with previous events. We must know, detect, characterize and quantify microhemorrhages, so Parameter 2d Echo gradient SWAN 3D 3T the echo-gradient T2 weighted images, as well Repetition time(ms) 650 41.2 as SWAN, play a crucial role in such an assess- Echo time (ms) 15.0 24.7 ment. The objective of this study is to compare Flip angle(grados) 20 15 echo-gradient T2 weighted MRI sequences and Band width (kKz) 20.8 62.5 susceptibility weighted angiography sequence Field of vision (cm) 24 20 (SWAN) in the description of cerebral microhe- Matrix size 256 × 224 320 × 224 morrhages in hypertensive patients. Flow compensation Yes Yes Section thickness 4.0 2.0 MATERIAL AND METHODS (5 mm) Gap No No An observational, descriptive and cross-sectional Number of sections 30 62 hasta 128 study was conducted in hypertensive patients Acquisition time 3:42 3:20 who were admitted to the Hospital Christus Muguerza Alta Especialidad de Monterrey who SWAN: susceptibility-weighted angiography sequence. had an MRI of the brain with a 3 Tesla unit from March, 2014 to September, 1915. Patients di- agnosed with hypertension who would have an Classification of microhemorrhages echo-gradient T2 sequence and a susceptibility weighted angiography sequence (SWAN) were The MRI sequences were reviewed and classified included, regardless of the cause. Patients who based on the presence, location, number and had a history or suspicion of a vascular malfor- grade of microhemorrhages, defining micro- mation, brain tumor on CT or MRI, or history hemorrhages as focal areas of very low signal of previous surgery, or recent trauma were ex- intensity under 10 mm
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