Study of catheter designs and drug mixing processes using 2D steady numerical simulations

The effectiveness of substance delivery through catheters is an important i ssue in interventional radiology, especially for infusion therapies where t he pharmacokinetic advantage of local intra-arterial drug administration ha s been firmly established. in principle, the procedure is used to provide a ppropriate local concentrations while maintaining low systemic values so as to minimise the global effect and toxicity of the intervention. However, p oor drug mixing may produce excessive local concentrations potentially dama ging for the surrounding tissues and may lead to unsuccessful therapies. Th ese phenomena have been observed in the infusion therapies of liver cancers through the hepatic artery and with brain tumour therapies through the car otid artery. Many aspects of the drug delivery methodology have been explor ed in order to determine the infusion conditions that would provide optimal mixing: the catheter tip design is considered one of the most important ch aracteristics to be investigated for this purpose. Interestingly, it turns out that angiographic procedures could also benefit from this, because bett er mixing properties are associated with designs that provide potentially l ess harmful flow conditions such as jets, whipping and recoil of the cathet er on the vascular wall. A 2D steady numerical model is proposed, to simula te the main physical processes occurring during catheter substance infusion . blood dynamics is taken into account with the Navier-Stokes equations and substance dispersion by the flowing blood with the advection-diffusion equ ation. The model is used to evaluate mixing properties of certain catheter designs in different flow conditions. in particular, two types of side hole catheter are compared in the context of water bath injection and in the co ntext of vessel injection. The simulations suggest that the improved mixing reported with water bath experiments would not be maintained in the clinic al context of arterial circulation.