Article Figures & Data
Figures
- Fig 1.
Patient 1. Frontal reformats of serial DW trace images.
A, Status at admission: complete filling of the abscess cavity by hyperintense material. Hyperintensity was mainly due to true diffusion weighting effect (see Fig 2A, -B).
B, Status 3 weeks later: appearance of two components with a sharply delineating interface. Hyperintensity at the time was mainly due to T2-weighted shine-through effect (see Fig 2C, -D).
C, Status 5 weeks later: further decrease in size of the hyperintense component after stereotactic drainage. The patient had clinically recovered at the time.
- Fig 2.
Patient 1. T2-weighted shine-through effect in the hyperintense component.
A and B, Status at admission. A, Frontal reformat of the T2-W image of the echo-planar imaging (EPI)–spin-echo (SE)–DW sequence with b factor = 0. Left frontal parenchyma displayed hyperintensity. Inferior area (double-ball arrowhead) seemed very slightly brighter than the superior one (arrow). B, Similar image after application of the diffusion-sensitizing gradients at b factor = 1000 s/mm2. The inferior area became hypointense and corresponded to vasogenic interstitial edema with mean ADC values at 1480 mm2/s. Superior area remained hyperintense because of prominent diffusion-weighting effect with a mean ADC at 650. Mean ADC was 780 in the contralateral normal brain tissue.
C and D, Status at 3 weeks. C, Frontal reformat of the T2-weighted image of the EPI-SE-DW sequence (b = 0). Left frontal parenchyma is still hyperintense, with little change when compared with panel A, except for more perceptible hyperintensity within superior areas (arrows) when compared to inferior areas (double-ball arrowhead). D, Similar image after application of the diffusion-sensitizing gradients at b = 1000. Inferior area of vasogenic edema displayed similar hypointensity as on admission (see panel B). A sharply delineated interface has appeared within the superior area separating a very hypointense upper area (black arrow) in which mean ADC value was measured at 2320 and a lower one (white arrow) with persistent hyperintensity in which mean ADC value was 1130. The upper area corresponded to fluid supernatant and the lower area to shrinking purulent core in which fibrinolysis has decreased the restriction to the water diffusion within pus when compared with the initial status (see panel B). The T2-weighted shine-through effect was thus far mainly responsible for hyperintensity in this subarea, and not the true diffusion weighting effect.
- Fig 3.
Patient 2.
A–C, Initial MR examination at admission. A, Postcontrast T1-weighted image shows a left-sided ring-like lesion with central cystic necrosis and enhanced peripheral margins. B, DW trace image shows sharply delineated central hypointensity and peripheral hyperintensity of the lesion. The pattern is up to now undescribed in pyogenic abscesses. C, ADC-mapped image shows strongly increased ADC values within the center of the lesion (mean, 2320) and moderately increased ones within the peripheral ring (mean, 1210). Mean ADC value in normal contra lateral mirror area was 830.
D–F, Serial follow-up DW images after stereotactic drainage and during consolidation antibiotic treatment. D, Lesion pattern has inverted when compared with the pretherapeutic status (Fig 2B): central area has now become hyperintense and peripheral one has become hypointense. E and F, Shrinkage of the central hyperintense component over time is obvious.
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