Framework to support vascular access surgery planning

Tommy Maas, MUMC, Maastricht

Patients with chronic kidney failure are dependent on renal replacement therapy. One of the treatment options is hemodialysis, which requires a vascular access. The preferred vascular access is an arteriovenous stula (AVF), where a vein is surgically connected to an artery. After the surgery, the blood ow will increase and the vessel diameters will dilate. When the flow is larger than 500 ml/min and the venous diameter is larger than 4 mm the AVF can be used for hemodialysis, this is called a matured AVF. A lot of AVFs su ffer from non-maturation (up to 50%). To reduce the
non-maturation rate, a computer model was developed during a previous international project which was able to simulate the postoperative blood flow through the AVF.

The current one year design project is part of a multicenter randomized controlled trial (RCT) to investigate the potential benefi t of including model based flow predictions in the regular decision-making process. The RCT will investigate if the non-maturation rate can be reduced by adding an advice, based on the flow predictions from the model, to the clinical decision-making.

The design project consisted of the following aims: 1) Design a frame-work which allows to perform patient speci c computer simulations in a multicenter RCT to predict the postoperative blood flow in an AVF. 2) Design and assess the feasibility of a protocol which can assess the quality of the input data of the computer model.

The designed framework used in the RCT showed to be able to simulate the direct and six week postoperative flows, the framework operates in a largely automated way and the framework allows to report the simulations results back to the participating hospitals within a time frame necessary in the RCT. The framework meets all the requirements and therefore, it is currently used in the RCT.

The quality of the input data is investigated by assessing the trueness and the precision, which are both part of the accuracy. A calibration study was designed and executed to assess the trueness error. A Gage R&R study was performed to assess the precision error, which is caused by reproducibility and repeatability variation. The calibration study was performed by a newly created calibration setup using a phantom tube with a reference diameter and flow. The setup was easy to transport, therefore calibration measurements could be performed in the di erent participating hospitals. The precision study was carried out on patients with kidney failure in one of the participating hospitals of the RCT. The measurement protocol showed to be feasible in one of the hospitals, but other hospitals have not been able
to perform the measurements yet.

In conclusion, the RCT framework was successfully implemented and the RCT should continue with the current framework, since the ecacy of the computer model needs to be assessed at the end of the study. For future applications of the model, the precision error of the input data should be assessed in (at least) one more hospital.