title: Feasibility of vibro-acoustography with a quasi-2D ultrasound array transducer for detection and localizing of permanent prostate brachytherapy seeds: a pilot ex vivo study.
abstract: OBJECTIVE
  Effective permanent prostate brachytherapy (PPB) requires precise placement of radioactive seeds in and around the prostate. The impetus for this research is to examine a new ultrasound-based imaging modality, vibro-acoustography (VA), which may serve to provide a high rate of PPB seed detection while also effecting enhanced prostate imaging. The authors investigate the ability of VA, implemented on a clinical ultrasound (US) scanner and equipped with a quasi-2D (Q2D) array US transducer, to detect and localize PPB seeds in excised prostate specimens.
  
  
  METHODS
  Nonradioactive brachytherapy seeds were implanted into four excised cadaver prostates. A clinical US scanner equipped with a Q2D array US transducer was customized to acquire both US and C-scan VA images at various depths. The VA images were then used to detect and localize the implanted seeds in prostate tissue. To validate the VA results, computed tomography (CT) images of the same tissue samples were obtained to serve as the reference by which to evaluate the performance of VA in PPB seed detection.
  
  
  RESULTS
  The results indicate that VA is capable of accurately identifying the presence and distribution of PPB seeds with a high imaging contrast. Moreover, a large ratio of the PPB seeds implanted into prostate tissue samples could be detected through acquired VA images. Using CT-based seed identification as the standard, VA was capable of detecting 74%-92% of the implanted seeds. Additionally, the angular independency of VA in detecting PPB seeds was demonstrated through a well-controlled phantom experiment.
  
  
  CONCLUSIONS
  Q2DVA detected a substantial portion of the seeds by using a 2D array US transducer in excised prostate tissue specimens. While VA has inherent advantages associated with conventional US imaging, it has the additional advantage of permitting detection of PPB seeds independent of their orientation. These results suggest the potential of VA as a method for PPB imaging that ultimately may allow US-based real-time intraoperative dosimetry.
authors.affiliation: Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota 55905.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Mehrmohammadi
authors.affiliation: Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota 55905 and Department of Internal Medicine, Mayo Clinic, Rochester, Minnesota 55905.
authors.forename: Azra
authors.initials: A
authors.lastname: Alizad
authors.affiliation: Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota 55905.
authors.forename: Randall R
authors.initials: RR
authors.lastname: Kinnick
authors.affiliation: Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota 55905.
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Davis
authors.affiliation: Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota 55905.
authors.forename: Mostafa
authors.initials: M
authors.lastname: Fatemi
mesh_terms: D001918:Brachytherapy / Q000379:methods*; D005240:Feasibility Studies; D006801:Humans; D008297:Male; D010865:Pilot Projects; D011467:Prostate / Q000000981:diagnostic imaging; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D014057:Tomography, X-Ray Computed; D014463:Ultrasonography / Q000295:instrumentation* / Q000379:methods*