title: X-ray CT high-density artefact suppression in cryosurgery.
abstract: Advantages of x-ray CT for imaging guidance of cryosurgery include 3D visualization of frozen and unfrozen tissue and calibration of temperature in the tissue water-ice interface (0-10 degrees C) to Hounsfield units. However, use of x-ray CT images and their thermal calibration can be compromised by the cryoprobes generating high-density streak artefacts. A new subtraction technique for artefact suppression is proposed and tested in prostate cryosurgery simulations. By subtracting the measured CT x-ray projection profile without cryoprobes from the profile with cryoprobes plus iceballs, one obtains the combined profile of the cryoprobes and a low value background. Polynomial interpolation to obtain the background profile allows its addition to the original profile without probes. The result may then be fed to a conventional filtered back-projection routine to reconstruct the probe-free image. Finally the cryoprobe pixels in the originally constructed image with probes and iceballs are added back to the probe-free image to get the final artefact-suppressed image. The major advantage of this subtraction technique is that it can successfully suppress the high-density artefacts in bone-abundant body regions such as the pelvis. X-ray CT images of cryoprobe arrays in a homogeneous gelatin phantom and the pelvic region of an anthropomorphic Rando phantom containing a human skeleton were generated. After suppression, cryoprobe metal artefact streaks are reduced and visualization of the positions and dimensions of the cryoprobes are well preserved.
authors.affiliation: School of Health Sciences, 550 Stadium Mall Drive, West Lafayette, IN 47907-2051, USA.
authors.forename: Jikun
authors.initials: J
authors.lastname: Wei
authors.forename: George A
authors.initials: GA
authors.lastname: Sandison
authors.forename: Laigao
authors.initials: L
authors.lastname: Chen
authors.forename: Yun
authors.initials: Y
authors.lastname: Liang
authors.forename: Lisa X
authors.initials: LX
authors.lastname: Xu
mesh_terms: D000465:Algorithms; D016477:Artifacts; D003452:Cryosurgery / Q000379:methods*; D006801:Humans; D008297:Male; D016343:Monitoring, Intraoperative / Q000379:methods*; D019047:Phantoms, Imaging; D011467:Prostate / Q000000981:diagnostic imaging / Q000601:surgery; D011786:Quality Control; D011856:Radiographic Image Enhancement / Q000379:methods*; D013382:Subtraction Technique; D014057:Tomography, X-Ray Computed / Q000379:methods*