title: A realistic deformable prostate phantom for multimodal imaging and needle-insertion procedures.
abstract: OBJECTIVE
  Phantoms are a vital step for the preliminary validation of new image-guided procedures. In this paper, the authors present a deformable prostate phantom for use with multimodal imaging (end-fire or side-fire ultrasound, CT and MRI) and more specifically for transperineal or transrectal needle-insertion procedures. It is made of soft polyvinyl chloride (PVC) plastic and includes a prostate, a perineum, a rectum, a soft periprostatic surrounding and embedded targets for image registration and needle-targeting. Its main particularity is its realistic deformability upon manipulation.
  
  
  METHODS
  After a detailed manufacturing description, the imaging and mechanical characteristics of the phantom are described and evaluated. First, the speed of sound and stress-strain relationship of the PVC material used in the phantom are described, followed by an analysis of its storage, imaging, needle-insertion force, and deformability characteristics.
  
  
  RESULTS
  The average speed of sound in the phantom was measured to be 1380 ± 20 m/s, while the stress-strain relationship was found to be viscoelastic and in the range of typical prostatic tissues. The mechanical and imaging characteristics of the phantom were found to remain stable at cooler storage temperatures. The phantom had clearly distinguishable morphology in all three imaging modalities, with embedded targets that could be precisely segmented, resulting in an average US-CT rigid registration error of 0.66 mm. The mobility of the phantom prostate upon needle insertion was between 2 and 4 mm, with rotations between 0° and 2°, about the US probe head.
  
  
  CONCLUSIONS
  The phantom's characteristics compare favorably with in vitro and in vivo measurements found in the literature. The authors believe that this realistic phantom could be of use to researchers studying new needle-based prostate diagnosis and therapy techniques.
authors.affiliation: UJF-Grenoble 1/CNRS/TIMC-IMAG UMR 5525, Grenoble, France. Nikolai.Hungr@imag.fr
authors.forename: Nikolai
authors.initials: N
authors.lastname: Hungr
authors.forename: Jean-Alexandre
authors.initials: JA
authors.lastname: Long
authors.forename: Vincent
authors.initials: V
authors.lastname: Beix
authors.forename: Jocelyne
authors.initials: J
authors.lastname: Troccaz
mesh_terms: D001918:Brachytherapy / Q000295:instrumentation* / Q000379:methods; D017076:Computer-Aided Design; D055119:Elastic Modulus; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D009339:Needles; D019047:Phantoms, Imaging; D011471:Prostatic Neoplasms / Q000175:diagnosis* / Q000532:radiotherapy*; D019919:Prosthesis Implantation / Q000295:instrumentation*; D013382:Subtraction Technique / Q000295:instrumentation*