CT Elastography: A Pilot Study via a New Endoscopic Tactile Sensor

Objective: To develop a CT elastography imaging system useful for part of the human body in which ultrasound is not capable of reaching. The proposed system would measure CT modality through fusion of the stiffness mapping on the images by the tactile sensor system, improving precision of the endoscopic operation. Methods: We made some liver fibrosis phantoms of bovine skin gelatin with various densities as the target organ of the study. Using the tactile sensor system, which requires no compression during endoscopic operation, stiffness of each phantoms was measured. The resulting stiffness vs density curve was evaluated and translated to the stiffness vs CT number (Houndsfield Unit, HU) curve with a CT number vs density curve obtained by CT scan of the phantoms. A transformation formula can be deduced from these curves to the elasticity via CT number, which was confirmed in vitro with pig liver and in vivo CT scan data. Results: The stiffness and CT modality of each phantom was successfully measured and subjected to constant reduction. The CT value shows a linear relationship with the ROI values of the livers used. Conclusion: This paper reports method of supplementing stiffness information measured by a tactile sensor system, with a CT image for use with an endoscope. It is shown that CT number can be derived with a stiffness sensor and CT data in endoscopic surgery. From there results, we prove the possibility of measuring stiffness with CT and high resolution CT number.