A dual modality phantom for cone beam CT and ultrasound image fusion in prostate implant

Journal Article · Thu May 15 04:00:00 EDT 2008 · Medical Physics

DOI:https://doi.org/10.1118/1.2898189· OSTI ID:21120699

Ng, Angela; Beiki-Ardakan, Akbar; Tong, Shidong; Moseley, Douglas; Siewerdsen, Jeffrey; Jaffray, David; Yeung, Ivan W. T. ^[1]

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1. Radiation Medicine Program, Princess Margaret Hospital, 610 University Avenue, Toronto, Ontario M5G 2M9 (Canada)

In transrectal ultrasound (TRUS) guided prostate seed brachytherapy, TRUS provides good delineation of the prostate while x-ray imaging, e.g., C-arm, gives excellent contrast for seed localization. With the recent availability of cone beam CT (CBCT) technology, the combination of the two imaging modalities may provide an ideal system for intraoperative dosimetric feedback during implantation. A dual modality phantom made of acrylic and copper wire was designed to measure the accuracy and precision of image coregistration between a C-arm based CBCT and 3D TRUS. The phantom was scanned with TRUS and CBCT under the same setup condition. Successive parallel transverse ultrasound (US) images were acquired through manual stepping of the US probe across the phantom at an increment of 1 mm over 7.5 cm. The CBCT imaging was done with three reconstructed slice thicknesses (0.4, 0.8, and 1.6 mm) as well as at three different tilt angles (0 deg., 15 deg., 30 deg. ), and the coregistration between CBCT and US images was done using the Variseed system based on four fiducial markers. Fiducial localization error (FLE), fiducial registration error (FRE), and target registration error (TRE) were calculated for all registered image sets. Results showed that FLE were typically less than 0.4 mm, FRE were less than 0.5 mm, and TRE were typically less than 1 mm within the range of operation for prostate implant (i.e., <6 cm to surface of US probe). An analysis of variance test showed no significant difference in TRE for the CBCT-US fusion among the three slice thicknesses (p=0.37). As a comparison, the experiment was repeated with a US-conventional CT scanner combination. No significant difference in TRE was noted between the US-conventional CT fusion and that for all three CBCT image slice thicknesses (p=0.21). CBCT imaging was also performed at three different C-arm tilt angles of 0 deg., 15 deg., and 30 deg. and reconstructed at a slice thickness of 0.8 mm. There is no significant difference in TRE between 0 deg. and 15 deg. (p=0.191) as well as between 0 deg. and 30 deg. (p=0.275), which suggests that the C-arm may be tilted intraoperatively to acquire CBCT images without compromising the quality of image fusion. The results conclude a high degree of accuracy and precision for the CBCT-TRUS fusion, which could be useful toward achieving real time intraoperative dosimetry in prostate brachytherapy.

• OSTI ID: 21120699
• Journal Information: Medical Physics, Journal Name: Medical Physics Journal Issue: 5 Vol. 35; ISSN 0094-2405; ISSN MPHYA6
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
ACCURACY
BRACHYTHERAPY
COMPUTERIZED TOMOGRAPHY
DOSIMETRY
IMAGE PROCESSING
IMAGES
PHANTOMS
PROSTATE
THICKNESS
ULTRASONOGRAPHY
X RADIATION