Susceptibility changes on preoperative acetazolamideloaded 7T MR quantitative susceptibility mapping predict post-carotid endarterectomy cerebral hyperperfusion.

Abstract

Background and purpose: Post-carotid endarterectomy (CEA) cerebral hyperperfusion (CH) can cause intracerebral hemorrhage and cognitive decline. Alterations in susceptibility in response to acetazolamide (ACZ) on 7T MRI quantitative susceptibility mapping (QSM) detects elevated CBV occurring due to impaired cerebrovascular autoregulation. We explored preoperative relative susceptibility changes on 7T MRI QSM in response to ACZ and their ability to predict CH following CEA.

Materials and methods: Sixty-three patients with uni-or bilateral cervical ICA stenosis ≥70% underwent 7T MRI at baseline and at 5, 10, 15, and 20 min after ACZ administration before surgery. The difference between the susceptibility of venous structures and surrounding brain parenchyma at each time point after ACZ administration relative to the difference at baseline (relative susceptibility difference; RSD) on QSM images was calculated in the cerebral hemisphere ipsilateral to surgery. Brain perfusion SPECT was conducted preoperatively and immediately following CEA to detect postoperative CH (≥ 100% rise in CBF postoperatively).

Results: In nine patients with postoperative CH, RSD was significantly increased at 5 or 10 min following ACZ administration (p < 0.05) but reduced at 15 and 20 min (p < 0.05). In 54 patients without postoperative CH, RSD at all four time points after ACZ administration was significantly lower than the baseline value (p < 0.05). The area under the receiver operating characteristic curve to predict postoperative CH was significantly greater in RSD₅ (0.981; 95% CI, 0.910-0.999) than in RSD₁₅ (0.872; 95% CI, 0.764-0.943) (p < 0.05) or RSD₂₀ (0.780; 95% CI, 0.658-0.874) (p < 0.01). Sensitivity, specificity, and positive and negative predictive values for RSD₅ at a cutoff near the left upper corner of the curve were 100%, 89%, 60%, and 100%, respectively. Logistic regression analysis revealed that only RSD₅ significantly predicted postoperative CH (95% CI, 455.9-4043.6; p < 0.05).

Conclusions: Changes in susceptibility on preoperative 7T MRI QSM following ACZ administration predict CH following CEA. Patients with increased RSD₅ on pre-CEA 7T MRI QSM following ACZ administration should undergo brain perfusion imaging immediately after surgery. Detection of CH on postoperative brain perfusion imaging warrants intensive blood pressure control.

Abbreviations: CEA= carotid endarterectomy; CH= cerebral hyperperfusion; OEF= oxygen extraction fraction; ACZ= acetazolamide; QSM =quantitative susceptibility mapping; 3D =three-dimensional; RSD=relative susceptibility difference; SD= standard deviation; ROC =receiver operating characteristic.