Visualization of cerebral microbleeds with dual‐echo T2*‐weighted magnetic resonance imaging at 7.0 T

Abstract

Purpose: To assess the visualization of cerebral microbleeds with dual echo T2*-weighted imaging at 7.0 T magnetic resonance imaging (MRI). Materials and Methods:Ten consecutive participants (eight men, two women, mean age 54 6 12 years) with vascular disease or risk factors from the second manifestations of arterial disease (SMART) study were included. Dual-echo T2*-weighted scans (echo time: 2.5/15.0 msec) were made for all participants at 7.0 T MRI. The number of visible microbleeds and the diameter of the microbleeds were recorded on minimal intensity projection images of both echoes. Results:The first echo image shows dark microbleeds against a homogeneous, more hyperintense signal of the brain tissue without contrast for veins and basal ganglia. In eight patients microbleeds were observed, with a total of 104 microbleeds. Of these, 88 (84.6%) were visible on the first and 102 (98.0%) on the second echo. The mean diameter of the microbleeds was 1.24 mm for the first echo and 2.34 mm for the second echo.Conclusion: T2*-weighted imaging at two echo times at 7.0 T combines the advantages of the first and second echo. Microbleeds visible on the first echo show large contrast with the surrounding tissue, even in the presence of paramagnetic ferritin. The second echo enables visualization of smaller microbleeds than the first echo.

Cerebral Microbleeds on MR Imaging: Comparison between 1.5 and 7T

“…The use of the TE1 image at 7T is helpful to distinguish microbleeds from deoxyhemoglobin in veins and ferritin in the basal ganglia, whereas microbleeds can be missed by overlap of veins or the hypointense appearance of ferritin-containing basal ganglia on the 1.5T scan or on the TE2 of the 7T scan. 25 Previous studies comparing the detection of microbleeds at 3T and 1.5T found significantly more microbleeds at 3T. In addition, the microbleed conspicuity improved at 3T.…”

“…Recently, we showed that the TE1 image provides a good contrast of the dark microbleeds against a homogeneous, more hyperintense signal intensity of the brain tissue and that 85% of all microbleeds are visible on the TE1 image. 25 If a microbleed is visible on the TE1 image and also shows a blooming effect on the TE2, it is more easily classified Fig 2. A, On this 1.5T scan, a hypointense lesion (arrow ) is visible that is not a typical well-defined, round-shaped lesion as in the definition of a microbleed. This lesion was not scored as a microbleed on the 1.5T scan.…”

“…The use of a dual-echo sequence at 7T has been shown to combine the benefits of a short TE and a long TE for the visualization of microbleeds in one sequence. 25 It has not been established whether the use of a dual-echo sequence at 7T increases the number of detected microbleeds compared with the commonly used single-echo T2*-weighted imaging at lower field strengths. The purpose of our study was to compare the visualization of microbleeds with T2*-weighted imaging at 1.5T with dual-echo T2*-weighted imaging at 7T and assess the reliability of the detection of microbleeds with the 2 field strengths.…”

Visual Cerebral Microbleed Detection on 7T MR Imaging: Reliability and Effects of Image Processing

“…1 On 7T dual-echo T2*-weighted MR imaging, for example, up to 3 times as many microbleeds can be detected than on 1.5T MR images. 2 However, susceptibility effects of other structures also complicate microbleed detection at higher field strengths.…”

“…2 However, susceptibility effects of other structures also complicate microbleed detection at higher field strengths. 1 We sought to determine mIP processing conditions with an optimal balance between accuracy and rating time and to determine intra-and interrater agreement for these processing conditions on 7T MR imaging.…”