Stroke is the third-most cause of death in developed countries. A new promising treatment method in case of an ischemic stroke is selective intracarotid blood cooling combined with mechanical artery recanalization. However, the control of the treatment requires invasive or MRI-assisted measurement of cerebral temperature. An auspicious alternative is the use of computational modeling. In this work, we extended an existing 1D hemodynamics model including the characteristics of the anterior, middle and posterior cerebral artery. Furthermore, seven ipsilateral anastomoses were additionally integrated for each hemisphere. A potential stenosis was placed into the M1 segment of the middle cerebral artery, due to the highest risk of occlusion there. The extended model was evaluated for various degrees of collateralization (“poor”, “partial” and “good”) and degrees of stenosis (0%, 50%, 75% and 99.9%). Moreover, cerebral autoregulation was considered in the model. The higher the degree of collateralization and the degree of stenosis, the higher was the blood flow through the collaterals. Hence, a patient with a good collateralization could compensate a higher degree of occlusion and potentially has a better outcome after an ischemic stroke. For a 99.9% stenosis, an increased summed mean blood flow through the collaterals of +97.7% was predicted in case of good collateralization. Consequently, the blood supply via the terminal branches of the middle cerebral artery could be compensated up to 44.4% to the physiological blood flow. In combination with a temperature model, our model of the cerebral collateral circulation can be used for tailored temperature prediction for patients to be treated with selective therapeutic hypothermia.
In Western countries, stroke is the third-most cause of death; 35- 55% of the survivors experience permanent disability. Mild therapeutic hypothermia (TH) showed neuroprotective effect in patients returning from cardiac arrest and is therefore assumed to decrease stroke induced cerebral damage. Recently, an intracarotid cooling sheath was developed to induce local TH in the penumbra using the cooling effect of cerebral blood flow via collaterals. Computational modeling provides unique opportunities to predict the resulting cerebral temperature without invasive procedures. In this work, we generated a simplified brain model to establish a cerebral temperature calculation using Pennes’ bio-heat equation and a 1D hemodynamics model of the cranial artery tree. In this context, we performed an extensive literature research to assign the terminal segments of the latter to the corresponding perfused tissue. Using the intracarotid cooling method, we simulated the treatment with TH for different degrees of stenosis in the middle cerebral artery (MCA) and analyzed the resulting temperature spatialtemporal distributions of the brain and the systemic body considering the influence of the collaterals on the effect of cooling.
Y. Lutz, R. Daschner, L. Krames, A. Loewe, O. Dössel, and G. Cattaneo. Estimating Local Therapeutic Hypothermia in Case of Ischemic Stroke Using a 1D Hemodynamics Model and an Energetic Temperature Model. In 41st Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), pp. 3983-3986, 2019
In Western countries, stroke is the third-most widespread cause of death. 80% of all strokes are ischemic and show a mortality rate of about 25%. Furthermore, 35-55% of affected patients retain a permanent disability. Therapeutic hypothermia (TH) could decrease inflammatory processes and the stroke-induced cerebral damage. Currently, the standard technique to induce TH is cooling of the whole body, which can cause several side effects. A novel cooling sheath uses intra-carotid blood cooling to induce local TH. Unfortunately, the control of the temporal and spatial cerebral temperature course requires invasive temperature measurements. Computational modeling could be used to predict the resulting temperature courses instead. In this work, a detailed 1D hemodynamics model of the cerebral arterial system was coupled with an energetic temperature model. For physiological conditions, 50% and 100% M1-stenoses, the temperatures in the supply area of the middle cerebral artery (MCA) and of the systemic body was analyzed. A 2K temperature decrease was reached within 10min of cooling for physiological conditions and 50% stenosis. For 100% stenosis, a significant lower cooling effect was observed, resulting in a maximum cerebral temperature decrease of 0.7K after 30min of cooling. A significant influence of collateral flow rates on the cooling effect was observed. However, regardless of the stenosis degree, the temperature decrease was strongest within the first 20min of cooling, which demonstrates the fast and effective impact of intra-carotid blood cooling.
Student Theses (1)
L. Krames. Modelling of the Human Cerebral Collateral Circulation Evaluation of the Impact on the Cerebral Pathophysiology in Case of Ischaemic Stroke. Institute of Biomedical Engineering, Karlsruhe Institute of Technology (KIT). Bachelorarbeit. 2018
In western countries, stroke is the third-most widespread cause of death. 87% of all strokes are ischaemic strokes. A common treatment in case of an ischaemic stroke is therapeutic hypothermia. It is expected to prevent an inflammation of the undersupplied tissue and is usually caused by surface cooling of the whole body. This leads to side effects such as cardiac arrhymias. A new promising treatment method is selective intracarotid blood cooling combined with a mechanical artery recanalisation. This approach requires a detailed knowledge of the cerebral circulation and a precise resolution of the brain temperature. An auspicious solution is the usage of a computational model. In this work, we extended an existing haemodynamics model, including the characteristics of the anterior, middle and posterior cerebral arteries using the transmission-line approach. In case of an ischaemic stroke, the collaterals are an important part of the cerebral circulation. Therefore, seven end-to-end anastomoses between the three main cerebral arteries were additionally considered for each hemisphere. The underlying stenosis was integrated into the M1 segment of the middle cerebral artery, due to the highest risk of occlusion. The extended model was evaluated in a physiological as well as in a pathophysiological case. Under healthy conditions the resulting flow in the extended model corresponded to the flow of the initial model. The flow through the collaterals barely existed, which is in accordance to the literature. For the pathophysiologial case, the degree of collateralisation and the degree of stenosis were varied, respectively. The different degrees of collateralisation were divided into "poor", "partial" and "good" and were realised by different values of anastomoses radii. For a 100% stenosis, a significantly high blood flow of 1.2528cm3/s through the collaterals in case of a "good" collateralisation could be shown. Therefore, the blood supply into the terminal branches of the middle cerebral artery could almost by half (48.18%) be compensated. The higher the degree of collateralisation was the higher the blood supply of the terminal branches of the MCA. Hence, a patient with a "good" collateralisation can compensate a higher degree of occlusion and potentially has a better outcome after an ischaemic stroke. In this work, 50%, 75% and 100% stenoses were compared with one another. The higher the degree of stenosis was the higher was the flow through the collaterals. In combination with a temperature model, the introduced model of the cerebral collateral circulation can be used to monitor hypothermal patients who suffered from an ischaemic stroke. The monitoring shall examine the blood and brain temperature in every part of the brain and in case of a deviation of the intended temperature the degree of hypothermia shall be modified.