A modified Edinburgh Pipe Phantom to quantify the effect of slice thickness on the imaging performance of curvilinear probes
Carmel Moran, Centre for Cardiovascular Science, University of Edinburgh
Background
We have previously demonstrated the usefulness of the Edinburgh Pipe Phantom (EPP) to measure the imaging performance of over 350 clinical and preclinical ultrasound transducers over a frequency range from 2.5-55MHz using the concept of the resolution integral (R). Recently, we have demonstrated the impact of slice thickness on the imaging performance of linear and matrix arrays and shown that R increased by a factor greater than 2.5 when slice thickness effects were removed. This study describes the manufacture and testing of a modified EPP to quantify the effect of slice thickness on R for curvilinear probes.
Methods
A phantom was constructed of two identical wedges of tissue-mimicking material (TMM) of height 250mm and width 100mm. The incline of the face of each of the wedges was at 40 degrees. The wedges were placed in a plastic box of degassed water and separated from each other using strips of polypropylene at distances between 0.42mm and 2.5mm, creating water-filled slots of these dimensions (insert Fig1). Since the width of the wedges (100mm) was greater than the probe slice thickness, the ability to image the slots was dependent primarily on the probe’s axial and lateral resolution. For each probe, the measurement of R obtained from the wedge phantom was compared to that obtained from the EPP. Two curvilinear probes were tested: Siemens Acuson S2000 6C1 HD (1-6MHz) and 4C1(1-4MHz).
Results/Discussion
R increased by a factor of 3.3(6C1) and 3.5(4C1) when measured using the wedge phantom compared to the EPP. This increase illustrates the impact of slice thickness on the imaging performance of curvilinear ultrasound transducers and highlights the need for elevational focusing of transducers to improve imaging performance.