A correlation study on target displacement and volume variation of primary middle and distal esophageal cancer during normal respiration using four-dimensional CT

Abstract

Objective To investigate the correlation between the motion of gross tumor volume (GTV) and the interested organs, and the correlation between the volume of GTV and the volume of heart and lung for the mid - and distal esophageal cancer using four - dimensional CT ( 4 DCT ) . Methods Seventeen patients with middle/distal esophageal carcinoma underwent respiration-synchronized 4DCT simulation during free breathing. All image sets were registered with the reference image ( T0 phase) , and the GTV, the dome of diaphragm, lung and heart were delineated on CT images of the ten respiratory phases. The position of GTV, lung, heart and the dome of diaphragm were identified in all 4DCT phases,and the volume of GTV , lung and heart were also achieved. Paired sample t test wereperformed to compare the primary esophageal cancer displacement in the three directions. The pearson correlation test was use to study the corTelation of GTV motion with the OARs , and the volume correlation of GTV with lung and heart.Results The maximum displacement of the GTV were 0. 19 cm,0. 17 cm,and 0. 48cm , respectively in x,y and z directions. And the displacement were significant different between z and x, y directions (t = - 3. 59 , - 4. 09 ,P = 0. 002,0.001) . The displacement of GTV correlated well with right lung and heart in three dimensions ( TRL-x = 0. 922 ,PRL-x = 0. 000 , TRL-y = 0. 700 , PRL-y = 0. 024, rRL-z = 0. 994 , PrRL-z = 0. 000;TH-x = 0. 720 , PH-x = 0. 010, rH-y = 0. 920 , PH-y = 0. 000 , rH-z = 0. 910, PH-z = 0. 000 ) , and only significantly associated with left lung in z direction (r = 0. 987,P = 0. 000) . There was a good correlation between GTV and the dome of diaphragm in z direction ( rL = 0. 918 , PL = 0. 000 ; rR= 0. 928 , PR= 0. 000 ) . Changes in the GTV volume was correlated well with the lung volume ( rLL = - 0. 680, PLL =0. 031 ;rrL = - 0. 670, PrL = 0. 034) , but the correlation was not significant with the heart ( r= -0. 368, P= 0. 295 ) during respiratory cycle. Conclusions For middle/distal esophageal cancer, the primary tumor motion was maximal in superior-inferior direction during normal respiration, and synchronized with the dome ofdiaphragm. The primary tumor displacement and volume variation have different correlations with heart and lung. Key words: Tomography,X-ray computed,four-dimensional; Cross tumor volume; Displacement correlation; Esophageal neoplasms/radiotherapy