SU-E-E-09: The Novel Investigation of the Accuracy of Image Position for Liver During Respiration in Helical CT




To assess the image position of liver along the Z-axis in helical CT compared to 4D CT and to evaluate the imaging similarity of helical CT and different phases of 4D CT for liver during respiration.


Eleven patients with whole liver scanning during free breath in both helical CT and 4D CT were investigated. Eleven representative points ₍in liver segment 1, 2, 3, 4a, 4b, 5, 6, 7, 8, main portal vein, liver dome₎ were drew in helical CT image and adaptive deformed to 4D CT image, including the phase of end-inspiration ₍phase 0₎ and end-expiration ₍phase 50₎, using SmartAdapt in Eclipse™ version 11.5. Distances along the Z-axis of the 11 points from helical CT to phase 0 CT, helical CT to phase 50 CT were measured, which represented the similarity of helical CT and end-inspiration CT, helical CT and end-expiration CT, respectively, for liver.


Mean distance along the Z-axis from helical CT to phase 0 CT is -2.4±1.3 ₍mean±SD₎₍mm₎, which is the average of the 11 points ₍S1:-2.5±4.6, S2:-2.5±5.1, S3:-4.0±3.2, S4a:-0.9±4.4, S4b:-2.9±4.1, S5:-2.0±2.5, S6:-3.6±3.3, S7:-3.6±4.3, S8:-1.8±3.9, main portal vein:-3.4±4.1, liver dome:0.3±4.1₎. Mean distance from helical CT to phase 50 CT is 3.9±1.6 ₍S1:3.0±4.2, S2:3.2±3.8, S3:2.1±1.9, S4a:1.4±3.6, S4b:3.7±3.9, S5:3.7±2.7, S6:3.9±3.3, S7:6.0±5.0, S8:3.7±3.8, main portal vein:4.8±4.8, liver dome:7.1±5.9₎.


Surprisingly, the image of helical CT scanning at random during free breath is more similar to the image at end-inspiration, which is not corresponding to human physiology. Moreover, the helical CT image at liver dome is even beyond the image at end-inspiration.