Comparison of the position and volume of esophagus between quiet end-inspiration and end-expiration three dimensional CT assisted with active breathing control and corresponding phases in four dimensional CT

Objective To compare the position,volume and matching index (MI) of esophagus between quiet end-inspiration and end-expiration in three dimensional CT (3D-CT) assisted with active breathing control (ABC) and the corresponding phases in four dimensional CT (4D-CT).Methods Eleven patients with peripheral lung cancer underwent 4D-CT simulation scan and 3D-CT simulation scans in end-inspiratory hold (CTEIH) and end-expiratory hold (CTEEH) in succession.The 0％ phase was defined as end-inspiratory phase (CT0),while the 50％ phase was defined as end-expiratory phase (CT50).The proximal,mid-,and distal thoracic esophagus were delineated separately on CT0,CT50,CTEIH and CTEEH images.The position,volume and MI of each segment esophagus between CT0 and CTEIH,CT50 and CTEEH were compared.Results In the left-right (x) direction,the position differences in the proximal,mid-,and distal thoracic esophagus between CT0and CTEIH were (-0.02 ±0.16)cm,(0.06 ± 0.26)cm and (0.10 ± 0.33) cm respectively,and in the anterior-posterior (y) direction,the position differences were (0.04 ±0.24)cm,(0.04 ±0.12) cm and (0.08 ±0.15) cm respectively,and the position differences in the same direction were not statistically significant.In the x direction,the position differences of the proximal,mid-,or distal thoracic esophagus between CT50 and CTEEH were (-0.02 ±0.24) cm,(0.12 ± 0.37) cm and (0.26 ± 0.33) cm respectively,and in the y direction,the position differences were (0.03 ±0.21)cm,(0.04 ±0.17)cm and (0.14 ±0.18)cm respectively,and the position differences in x and y directions of proximal and mid-thoracic esophagus between CT50 and CTEEH were not statistically significant,while the position differences in x and y directions of distal thoracic esophagus between CT50and CTEEH were both statistically significant (t =0.025,0.024,P ＜ 0.05).The volumes of the proximal,mid-and distal thoracic esophagus were all larger in CT0and CT50 than those in CTEIHand CTEEH,but without statistical differences.The MIs of the volumes of the proximal,mid-and distal thoracic esophagus between CT0 and CTEIH were (0.50 ± 0.17),(0.50 ± 0.19) and (0.56 ± 0.08),respectively,and those between CT50and CTEEH were (0.50 ±0.16),(0.47 ±0.14) and (0.51 ±0.15),respectively.The MI of each segment esophagus between CT0and CTEIHwas larger than that between CT50 and CTEEH,but without statistical differences.Conclusions The influence of breathing modes on the centroid positions of the proximal,mid-thoracic normal esophagus were not significant and there were spatial mismatches for any segment esophagus between 3D-CT assisted with ABC and 4D-CT. Key words: Esophagus;  Active breathing control;  Three dimensional-CT;  Four dimensional-CT