Computed tomography perfusion evaluation after extracranial-intracranial bypass surgery

Area of Science:

• Neurology
• Radiology
• Medical Imaging

Background:

• Perfusion imaging is crucial for evaluating extracranial to intracranial (EC-IC) bypass surgery outcomes.
• Altered hemodynamics and delayed contrast arrival post-surgery can affect perfusion measurements.
• Comparing different perfusion algorithms is essential for accurate postoperative assessment.

Purpose of the Study:

• To compare perfusion asymmetry using three different computed tomography perfusion (CTP) algorithms in EC-IC bypass surgery patients.
• To evaluate the impact of contrast arrival delay on perfusion measurements.
• To determine which algorithm best differentiates patients with and without new infarction.

Main Methods:

• Retrospective analysis of 22 patients undergoing CTP after EC-IC bypass surgery.
• Analysis using three algorithms: delay-sensitive (fMTT), semi-delay-sensitive (sSVD), and delay-insensitive (bSVD).
• Comparison of interhemispheric perfusion asymmetry (MTT, CBF, CBV) and correlation with new infarcts on follow-up imaging.

Main Results:

• Median interhemispheric bolus arrival time difference (ΔBAT) was 0.98s, indicating altered hemodynamics.
• Delay-insensitive algorithms yielded significantly smaller mean transit time (MTT) differences compared to delay-sensitive ones.
• Only the delay-insensitive method showed a significant difference in MTT asymmetry between patients with and without infarction (p=0.04).

Conclusions:

• Delay-sensitive algorithms overestimate MTT asymmetry in EC-IC bypass patients.
• The delay-insensitive algorithm is more effective in distinguishing between patients with and without infarction post-EC-IC bypass surgery.
• Accurate perfusion assessment in EC-IC bypass requires algorithms that account for delayed contrast arrival.