PO-03-063 A POLYACRYLAMIDE (PAA) GEL PHANTOM FOR STUDYING CATHETER ABLATION

Abstract

Benchtop studies are often used to evaluate cardiac ablation techniques, and commonly utilize ex-vivo animal tissues. While widely available, ex-vivo animal tissues do not consistently replicate live atrial tissue physical properties, adding variability. Tissue mimicking phantoms have been used in non-cardiac ablation studies, but their mechanical and electrical properties may not mimic cardiac tissue. Furthermore, analysis of ablation lesions ex-vivo has been limited to 2D measurements of lesion cross-sections, precluding lesion volume measurement and limiting accuracy. Polyacrylamide (PAA) gels, which have modifiable elasticity, and similar thermal and electrical properties to live human tissues, have been used to study liver ablation. The addition of bovine serum albumin (BSA) – a protein that coagulates when heated beyond a set temperature – has also been shown to provide optical and MRI contrast in ablated gels. The aim of this study was to develop a reproducible atrial tissue phantom with realistic elasticity, friction, and electrical impedance, enabling in-vitro replication of cardiac ablation lesions and 3D quantification using high resolution MRI scans. Gels were mixed with acrylamide concentrations from 3% to 12% (g/mL) and 2% BSA. Resulting Young's moduli and coefficients of friction were measured with a custom tester. Reference frictional properties of ex-vivo porcine aortic specimens were measured using the same methods. Reference elasticity values were derived from the literature. Gels were ablated in saline with 20-40W of power, for 20-40s, with 10-20g of contact force. Baseline impedances were set to 125Ω by titrating the salinity of the bath. Finally, gels were imaged using a 3D T2-weighted sequence on a 3T MRI scanner. The elasticity and friction of the fabricated gels are reported in Table 1, along with reference values. 10.5-12% acrylamide PAA gel phantoms matched live contractile tissue elasticity, and simulated realistic atrial tissue frictional and electrical properties. Ablations were made optically visible by the coagulation of coagulated BSA (Fig 1a) and appeared hypointense on T2-MRI (Fig 1b), enabling automated 3D analysis by thresholding. Measured lesion dimensions were comparable to those reported in prior literature. PAA gel phantoms enabled in-vitro replication of cardiac lesions with realistic mechanical and electrical properties. The addition of BSA facilitated optical verification of lesions and 3D quantification using MRI.Tabled 1Table 1: Reference and measured physical properties of gel phantoms and ex-vivo aortae as compared to literature valuesPhysical PropertyReferenceMeasured ValueMaterialValueMaterialValueYoung's Modulus (kPa)Ex-vivo porcine left atrium28.0% PAA gel32.6In-vivo human left ventricle20-200.210.5% PAA gel68.1In-vivo skeletal muscle6.2-108.612.0% PAA gel108.0Coefficient of FrictionEx-vivo porcine aorta0.02-0.046Ex-vivo porcine aorta0.058±0.024Agarose gel0.03510.5% PAA gel0.023±0.0014 Open table in a new tab