An Open Environment CT-US Fusion for Tissue Segmentation during Interventional GuidanceReport as inadecuate




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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 mm2 ROI resulted in mean HU of 68±44 within the tumor and −97±52 within the fat pad adjacent to the tumor p<0.005. The tumor area measured by CT and histology was correlated r2 = 0.92, while the area designated as fat decreased with increasing tumor size r2 = 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 mm3, 75–150 mm3 and >150 mm3, 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.



Author: Charles F. Caskey , Mario Hlawitschka, Shengping Qin, Lisa M. Mahakian, Robert D. Cardiff, John M. Boone, Katherine W. Ferrara

Source: http://plos.srce.hr/



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