An open environment CT-US fusion for tissue segmentation during interventional guidance. Academic Article uri icon


  • Therapeutic ultrasound (US) can be noninvasively focused to activate drugs, ablate tumors and deliver drugs beyond the blood brain barrier. However, well-controlled guidance of US therapy requires fusion with a navigational modality, such as magnetic resonance imaging (MRI) or X-ray computed tomography (CT). Here, we developed and validated tissue characterization using a fusion between US and CT. The performance of the CT/US fusion was quantified by the calibration error, target registration error and fiducial registration error. Met-1 tumors in the fat pads of 12 female FVB mice provided a model of developing breast cancer with which to evaluate CT-based tissue segmentation. Hounsfield units (HU) within the tumor and surrounding fat pad were quantified, validated with histology and segmented for parametric analysis (fat: -300 to 0 HU, protein-rich: 1 to 300 HU, and bone: HU>300). Our open source CT/US fusion system differentiated soft tissue, bone and fat with a spatial accuracy of 1 mm. Region of interest (ROI) analysis of the tumor and surrounding fat pad using a 1 mm(2) ROI resulted in mean HU of 6844 within the tumor and -9752 within the fat pad adjacent to the tumor (p<0.005). The tumor area measured by CT and histology was correlated (r(2)=0.92), while the area designated as fat decreased with increasing tumor size (r(2)=0.51). Analysis of CT and histology images of the tumor and surrounding fat pad revealed an average percentage of fat of 65.3% vs. 75.2%, 36.5% vs. 48.4%, and 31.6% vs. 38.5% for tumors <75 mm(3), 75-150 mm(3) and >150 mm(3), respectively. Further, CT mapped bone-soft tissue interfaces near the acoustic beam during real-time imaging. Combined CT/US is a feasible method for guiding interventions by tracking the acoustic focus within a pre-acquired CT image volume and characterizing tissues proximal to and surrounding the acoustic focus.

published proceedings

  • PLoS One

author list (cited authors)

  • Caskey, C. F., Hlawitschka, M., Qin, S., Mahakian, L. M., Cardiff, R. D., Boone, J. M., & Ferrara, K. W.

citation count

  • 11

complete list of authors

  • Caskey, Charles F||Hlawitschka, Mario||Qin, Shengping||Mahakian, Lisa M||Cardiff, Robert D||Boone, John M||Ferrara, Katherine W

editor list (cited editors)

  • Brechbiel, M. W.

publication date

  • January 2011