A breathing anthropomorphic liver phantom for interventional radiology

Abstract

Liver cancer causes 700.000 deaths annually. To assess new devices and pre-clinical procedures for treatment, a safe test environment can be provided by a phantom. Phantoms act as a surrogate for certain physical properties of tissue. The purpose of this study is to design, construct and evaluate an anthropomorphic liver phantom, which simulates respiratory motion and inhibits similar needle-tissue interaction for ultrasoundguided needle interventions. The liver model and surroundings are made from water-based solution with polyvinylalcohol (PVA). The liver model and surroundings are made of 6%m, 4%m PVA with 2 and 3 freeze thaw cycles, respectively. The rigid structures, i.e. vertebrae and ribs, are made of a flexible polymer. Threedimensional printing technique is employed to create molds for the anthropomorphic structures in terms of organ shape. Detailed steps for phantom construction and choice of phantom ingredients and construction recipe are reported. The actuation is provided by a linear actuator, which is adjustable in stroke length, frequency and direction. Preliminary results of the reproduced motion in the liver model are 20.7, 10.8 and 6.7 mm in CC, AP and LR direction, respectively. Further, the phantom allows both subcostal and intercostal ultrasound needle guidance. The liver model is designed to simulate diseased tissue. From Fibroscan measurements, the livermodel is characterizedwith an elastic modulus of 24.0(±8.0) kPa. Further, the liver model shows median higher axial needle friction forces (0.0374 N/mm) compared to healthy liver tissue (0.01108
N/mm). Furthermore, tactile feedback on the liver model is obtained from a liver surgeon, dr. W. Polak, whom graded the liver model with fibrosis scale 2. Based on the Fibroscan results, increased needle friction forces and tactile feedback, the liver model can be classified as cirrhotic. Additionally, the prototype is assessed by head of the section interventional radiology at the Erasmus MC, dr. A. Moelker. The doctor was able to perform ultrasound-guided needle insertion. Concluding, that a working prototype, which simulates respiratory motion and inhibits similar tissue-needle interaction as human tissue for ultrasound-guided needle interventions, is created.