Superficial temporal artery and middle cerebral artery (STA-MCA) bypass surgery is an effective method to enhance cerebral blood flow (CBF) in ischemic patients. However, the effectiveness of various bypass techniques varies with the diversity of Circle of Willis (CoW) structures. This study aims to develop a physiologically realistic hemodynamic model to optimize STA-MCA bypass planning for cerebral ischemia patients with different CoW structures. This study developed a 0D-1D geometric multi-scale haemodynamic model that coupled the stenosis model and the cerebral autoregulation model. Based on this model, nine CoW structural models before and after end-to-side (E-S) and side-to-side (S-S) bypass were constructed, and their haemodynamic properties were calculated to evaluate the efficacy of different bypass methods in different CoW structures. The validity of the model and results was verified by clinical data. For the mRACA1, mRACA1-fRPCA1, and mACoA CoW structures, there was a risk of hyperperfusion (13.96%, 12.81%, and -2.64%) after E-S bypass but not S-S bypass. In the mACoA-mLPCoA structure, both bypass techniques posed hyperperfusion risk (112.41% and 30.57%). Other CoW structures showed that E-S bypass could restore CBF without the risk of hyperperfusion. The model's predictions were within 5% of clinical data. The mRACA1, mRACA1-fRPCA1, and mACoA structures were suitable for S-S bypass
the mACoA-mLPCoA structure was not suitable for bypass, and other CoW structures favored E-S bypass. The developed model can effectively simulate the cerebral hemodynamic environment and predict the risk of hyperperfusion, offering valuable insights for personalized bypass planning in cerebral ischemia patients.