Changes in perfusion-weighted magnetic resonance imaging after carotid angioplasty with stent

Abstract

Carotid artery stenosis due to arteriosclerosis increases the risk of cerebral ischemia via embolic phenomena or reduced blood flow. The changes in cerebral perfusion that may occur after treatment are not clearly understood. This study evaluated the changes in cerebral microcirculation following carotid angioplasty with stenting (CAS) under cerebral protection with filters using ultrafast gradient echo (GRE) perfusion weighted imaging (PWI) with magnetic resonance imaging (MRI). Prospectively, 21 cervical carotid stenosis patients, mean age 69.95 years, underwent MRI 12 h before and 72 h after CAS. PWI parameters were collected for statistical analysis: cerebral blood volume (CBV), mean transit time (MTT) and time to peak (TTP). Statistical analysis was applied to absolute parameters and to values normalized against those from the contralateral parenchyma. The main finding of this study was improved hemodynamics for the normalized data after CAS, shown by reduced MTT (p<0.001) and TTP (p=0.019) in the territory fed by the middle cerebral artery ipsilateral to the CAS. Absolute data showed increased blood volume in the cerebral hemispheres after CAS, which was more accentuated on the stent side (p=0.016) than the contralateral side (p=0.029). Early improvements in cerebral perfusion, mainly seen in the normalized data, were clearly demonstrated in the timing parameters - TTP & MTT - after CAS.

Figure 1

Example of ROI placement in a 54-year-old man with right carotid artery stenosis estimated at 70% by DSA. Initially the ROI representative of the right MCA (A) was traced manually (area traced in purple), followed by a central line of symmetry and the area mirrored on the left hemisphere (area drawn in green). The timing graph (B) shows the TTP curve (purple) for the area representing the right MCA with a delay compared to the green curve representing the left MCA. The PWI map in TTP (C) demonstrates the evident timing delay in the purple demarked area.

Figure 2

Angiography and perfusion data from a 75-year-old woman with severe right carotid artery stenosis by digital angiography (A). PWI before CAS: CBV of the right MCA territory is 4% less than contralateral value (B), MTT shows a 3% delay (C) and TTP a 3% delay (D). Angiography after angioplasty with stent showing the absence of residual stenosis (E). PWI after CAS in the same axial section revealing improvement in all three perfusion parameters by MRI: right side CBV is 5% higher than contralateral value (F), MTT 1% quicker (G), and TTP without delay (H).