MR Imaging for Differentiating Contrast Staining from Hemorrhagic Transformation after Endovascular Thrombectomy in Acute Ischemic Stroke: Phantom and Patient Study

Abstract

Background and purpose: Early differentiation of contrast staining from hemorrhagic transformation in patients with acute ischemic stroke who have undergone endovascular treatment is critical in preventing the delayed administration of antiplatelet agents. We aimed to demonstrate the usefulness of an immediate postinterventional DWI protocol including B₀ and gradient recalled-echo sequences to discriminate those 2 conditions through phantom and preliminary retrospective patient studies.

Materials and methods: On 3T MR imaging, the signal intensities of the phantom models consisting of iodinated contrast agents diluted with normal saline and arterial blood were compared using T1WI, T2WI, and gradient recalled-echo sequences. A total 17 patients (8 with hemorrhagic transformation and 9 with contrast staining; 8 men and 9 women; mean age, 72.00 ± 10.91 years; range, 52-90 years) who underwent mechanical thrombectomy for acute ischemic stroke and showed newly appearing hyperdense lesions on immediate (<24 hours) postinterventional nonenhanced CT scans were included in this study. Immediate postinterventional DWI of patients were compared.

Results: In the phantom study, iodinated contrast agents diluted with normal saline showed minimal signal drop, while those diluted with arterial blood demonstrated dark signal intensity in the T2WI and gradient recalled-echo sequences. In the patient study, all hemorrhagic transformations and none of the contrast staining demonstrated dark or low signal (<gray matter) intensities similar to those of the vessel in the B₀-DWI and gradient recalled-echo images.

Conclusions: According to our preliminary results, contrast staining might be differentiated from hemorrhagic transformation using an immediate postinterventional DWI protocol including gradient recalled-echo sequences. It might be possible to expedite establishment of postinterventional medical treatment strategy.

Fig 1.

Study design.

Fig 2.

MR signal intensity of IODNS and IODBL on T1-weighted, T2-weighted, and gradient recalled-echo images. A, Images from the phantom. B, T1-relaxation times of IODNS and IODBL at different concentrations. C, T2-relaxation times of IODNS and IODBL according to the concentration of iodinated contrast agents. Visipaque (iodixanol, 320 I mg/mL, 2.5 I mol/L, iso-osmolar) was used as the iodinated contrast agent in this phantom.

Fig 3.

Magnetic signal intensity score of hemorrhagic transformation and contrast staining on B₀, gradient recalled-echo, T2-weighted, and T1-weighted imaging. Score 1, signal intensity was similar to that of the vessel; score 2, signal intensity was lower than that of the gray matter; score 3, signal intensity was similar to that of the gray matter; and score 4, signal intensity was higher than that of the gray matter.

Fig 4.

Representative images of hemorrhagic transformation and contrast staining in 3 patients with acute ischemic stroke. First row: images of a 66-year-old man with infarction in the territory of the right middle cerebral artery. A persistent hyperdense lesion in the right lentiform nucleus, presumed to be a hemorrhagic transformation (arrow), shows dark signal intensity in the B₀, gradient recalled-echo, and T2-weighted images. In contrast, a hyperdense lesion in the right caudate nucleus, which is washed out on the follow-up nonenhanced brain CT and presumed to be contrast staining (arrowhead), demonstrates a high signal intensity in the B₀, GRE, and T2-weighted images. This patient was grouped into the hemorrhagic transformation group, and the lesion in the lentiform nucleus was analyzed. Middle row: images of a 68-year-old man with infarction in the region of the right superior cerebellar artery. A persistent hyperdense lesion in the left cerebellum, presumed to be hemorrhagic transformation (arrow), shows dark signal intensity in the B₀, GRE, and T2-weighted images. Lower row: images of an 88-year-old woman with bilateral cerebellar infarction. A hyperdense lesion in the bilateral upper cerebellum, which disappeared on CT_FU and was presumed to be contrast staining (arrowhead), demonstrates iso-signal intensity in the B₀, GRE, and T2-weighted images.