(a) Photograph of the phantom with mobile prostate and rectum. (b) CAD drawing of phantom. Note that the rectum shown in this figure is meant for end-fire US probes. For side-fire probes, a cylindrical rectum is used, as shown in Fig. 11.
Steps during construction of the prostate phantom. (a) Mould used to shape the outer frame of the phantom. (b) Heating of the PVC mixture. (c) Pouring the molten PVC into the prostate mould. (d) Placing the targets onto the first layer of the prostate. (e) The final prostate shape. (f) Coating the prostate with an echogenic stained PVC mixture. (g) Putting the prostate in place inside the frame. (h) Allowing the phantom to cool overnight.
The shallowest and deepest trajectories from the probe head, used to calculate the range of sound speeds in the phantom.
Mechanical characterization machine used to measure the compression stress-strain relationship of the PVC samples. The inlayed image shows a sample in place between the compression rods.
Stress-strain curves for the five sets of PVC samples. The displayed equations represent the polynomial fits for the compression phase (upper part) of each curve.
Volume over time of the segmented inclusions for the three samples stored at different temperatures. The uneven jumps in the curves are likely the result of slight image inconsistencies caused by variable probe pressure or the presence of air bubbles in the ultrasound gel applied at the probe–phantom interface.
Sagittal (left images) and transverse (right images) cuts of 3D ultrasound volumes taken of two different phantoms. The top images are of a phantom with 3 mm polymer clay targets embedded in the prostate, while bottom images show a phantom embedded with 1 mm glass targets. Note that the oblique angle of the prostate in the sagittal images is due to the use of an obliquely placed end-fire probe.
Transverse cuts of a CT (left) and an MR (right) volume of two different phantoms. The left phantom has polymer clay embedded targets. The right phantom has a urethra. (1) Frame, (2) rectum, (3) periprostatic material, (4) prostate, (5) polymer clay targets, and (6) urethra.
Axial needle force measured during needle insertion into our phantom. A denotes the needle traversing the perineum. B denotes the super soft PVC before reaching the prostate. C denotes the prostate. D denotes the relaxation of the material after stopping needle motion.
Needle insertion locations used for phantom deformation testing.
Prostate phantom with a horizontal cylindrical rectum, being used with a side-fire US probe during a mock brachytherapy test.
Properties of the typical soft materials used in phantom construction, as found in the literature. All values were reported at room temperature.
Ratios of hardener to softener used to make the various PVC mixtures used in our phantom. ρ is density, c is speed of sound, E is elastic modulus, and H is Hounsfield.
Results showing the translation and rotation of the prostate during needle insertion into the phantom.
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