Article Figures & Data
Figures
- Fig 1.
Microbleed or calcification? A, GRE magnitude image shows a dark spot in the left frontal white matter. B, GRE phase images of the corresponding lesion reveal various phase patterns from the cranial-to-caudal direction. These appear totally dark at the upper and lower border sections; however, a mixed dark and bright pattern is visible in the center section. The heterogeneous phase pattern hinders interpretation of whether the lesion is a microbleed or calcification.
- Fig 2.
Axial phase patterns of GRE dark spots. The 6 axial phase patterns include the following: pattern 1, totally black; pattern 2, totally white; pattern 3, black circle with white core; pattern 4, white circle with black core; pattern 5, heterogeneously black; and pattern 6, heterogeneously white. Lesions with phase patterns 1, 3, and 5 were interpreted as paramagnetic microbleeds in which >50% of the area is dark. Lesions with phase patterns 2, 4, and 6 were interpreted as diamagnetic calcifications in which >50% of the area appeared bright.
- Fig 3.
Phase patterns of calcifications and microbleeds <2.5 mm in diameter. A, A small dark spot (arrow) attached to the left distal vertebral artery is shown in the GRE magnitude image. It is totally white at the central with border slices in the axial phase image, which suggest a diamagnetic lesion. CT confirms this as arterial wall calcification. B, A small dark spot (arrow) located at the left frontal subcortical white matter in the GRE magnitude image. It is totally dark at the central with border slices of the axial phase image, which suggest a paramagnetic lesion. Coronal phase imaging reveals a black dipole with a pair of faint bright side wings. The bright side wings are the faint, peripheral, bright rim around the dark lesion in the axial central phase image. CT reveals no corresponding lesion and confirms it to be a microbleed.
- Fig 4.
Phase patterns of calcifications and microbleeds of >2.5 mm in diameter. A, A dark nodule (arrow) in the pineal region is displayed in the GRE magnitude image. It is heterogeneously black in the axial central phase image, whereas it is totally white in the axial border phase image. The inconsistent finding of the axial phase pattern hinders differentiation between a calcification and microbleed. Coronal phase imaging displays a white dipole more clearly, with a black core and side wings (arrow). QSM indicates a dark spot (arrow) at the corresponding site, which indicates a diamagnetic lesion. CT confirms it to be a pineal calcification. B, A dark nodule (arrow) at the right temporal subcortical white matter is presented in the GRE magnitude image. It is heterogeneously white in the axial central phase image, whereas it is totally black in the axial border phase images. The inconsistent finding hinders differentiation between a calcification and microbleed. Coronal phase imaging reveals a black dipole with a white core and side wings (arrow), and QSM indicates a bright spot (arrow) at the corresponding site, which suggests a paramagnetic lesion. CT confirms this to be a microbleed.
- Fig 5.
Correlation between the diameter and susceptibility of lesions. A, A strong positive correlation is observed between the diameter and susceptibility of lesions in CMBs (r = 0.72, P < .001). B, A strong negative correlation is observed between the diameter and susceptibility of lesions in calcifications (r = −0.824, P = .003).
- Fig 6.
2D simulation of the local phase shift around lesions smaller and larger than 2.5 mm in diameter. The simulation was based on Equations 1 and 2. The phase shift is represented in the radians, and phase aliasing occurs when the phase shift exceeds +π or –π radians. The parameters are the same as those in our clinical setting: B0, 3T; TE, 25 ms; and gyromagnetic ratio, 42.58 × 106 Hz/T. The relative susceptibility (Δχ) and diameter (D) of the lesion are the mean values of the lesions in each group in our study. In lesions <2.5 mm in diameter, the simulated phase image reveals a black dipole with white side wings in the paramagnetic lesion (A) and a white dipole with black side wings in the diamagnetic lesion (B). In lesions >2.5 mm in diameter, the relative susceptibility is higher and the diameter is larger, which causes a larger phase shift that exceeds the aliasing threshold within the lesion. This results in a black dipole with a white core from phase aliasing, the white side wings in the paramagnetic lesion (C), and a white dipole with a black core and black side wings in the diamagnetic lesion (D).
- Fig 7.
Serial changes in the axial phase pattern in paramagnetic and diamagnetic dipoles. A, A diamagnetic dipole, which represents a pineal calcification, is displayed in the coronal phase image (left) and magnified image (middle). The white dipole with a black core and side wings in the coronal phase image explains serial changes in the axial phase patterns (right upper images) in the corresponding 5 levels: 1, totally white; 2, white circle with black core; 3, heterogeneously black (epicenter); 4, white circle with black core; and 5, totally white (lower border). The phase shift diagram (right lower images) crossing the center of the lesion reveals that when the positive phase shift is large enough to exceed π radians, it aliases toward −π radians and appears to be partially dark in the phase images near the central slices (2, 3, and 4 of the right lower images). B, A paramagnetic black dipole, which represents a microbleed in the white matter of the right cerebral hemisphere, presents the opposite pattern in the coronal and axial phase images and phase shift diagrams. C, A paramagnetic black dipole larger than that in B shows an alternating “black in white” core in the coronal phase (middle) and axial phase images (2, 3, and 4 of the right upper images). The phase shift diagram indicates that when the negative phase shift is large enough to exceed −π radians, it aliases toward +π radians (2 and 4 of the right lower images), and if the phase shift exceeds +π radians after the first aliasing, it aliases backward by −π radians (3 of the right lower images), which causes the alternating black in white core pattern in the center of the black dipole.
Tables
- Table 1:
Phase patterns of cerebral microbleeds and intracranial calcifications at the border and central slices
Phase Pattern Microbleeds (n = 128) Calcifications (n = 62) All sizes <2.5 mm ≥2.5 mm All sizes <2.5 mm ≥2.5 mm Border phase pattern 1) Totally black 128 74 54 1 1 0 2) Totally white 0 0 0 61 25 36 3) Black circle with white core 0 0 0 0 0 0 4) White circle with black core 0 0 0 0 0 0 5) Heterogeneously black 0 0 0 0 0 0 6) Heterogeneously white 0 0 0 0 0 0 Central phase pattern 1) Totally black 80 73 7 2 1 1 2) Totally white 0 0 0 27 25 2 3) Black circle with white core 10 0 10 0 0 0 4) White circle with black core 3 0 3 9 0 9 5) Heterogeneously black 17 1 16 11 0 11 6) Heterogeneously white 18 0 18 13 0 13 - Table 2:
Diagnostic accuracy of the border and central phase patterns and QSM for identifying calcification
Lesion Diameter All Lesions (n = 190) Lesions with QSM (n = 46) Border Phase Central Phase P Value Border Phase QSM P Value SEN (%) SPE (%) SEN (%) SPE (%) SEN SPE SEN (%) SPE (%) SEN (%) SPE (%) SEN SPE All sizes (n = 190) 98.4 100 79.0 83.6 .002 <.001 100 100 100 100 1 1 <2.5 mm (n = 100) 96.2 100 96.2 100 1 1 100 100 100 100 1 1 ≥2.5 mm (n = 90) 100 100 66.7 61.1 .002 <.001 100 100 100 100 1 1 Note:—SEN indicates sensitivity; SPE, specificity; QSM, quantitative susceptibility mapping.
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