ABSTRACT
Objective To explore the optimal delay time of enhanced scanning with CT based simulation before cyberknife treatment of carcinoma in different positions of the pancreas.Methods Philips 16 large aperture spiral CT scan was applied.Fifty-three patients with carcinoma in the head of the pancreas and 60 pancreatic cancer patients in the body or tail were randomly assigned to three groups with scan delays of 25,45,and 65 seconds in group A (25s group,pancreatic head n =18,pancreatic body or tail n =21);30,50,and 70 seconds in group B (3 0s,pancreatic head n =17,pancreatic body or tail n =19);and 35,55,and 70 seconds in group C (35s,pancreatic head n =18,pancreatic body or tail n =20),respectively.Images were evaluated by three associate professors of radiation oncology based on image quality score scale.The items rating in different time points were compared using a random intercept model of mathematical mean in three groups.Then the items rating of different time points were compared in pairs using the Sidak method.One-way ANOVA was used to compare the optimal time point of each group,so the optimal delay time of enhanced scanning with CT based simulation before cyberknife treatment of pancreatic cancer was obtained.Results The delayed time points with the highest scores for target delineation of the tumor in the pancreatic head and the pancreatic body or tail by CT enhanced scanning in three groups were 45 s/65 s,50 s/50 s,55 s/75 s,respectively.There was no significant difference in the scan time of 45 s,50 s and 55 s for the tumor in the pancreatic head.Similarly,no significant difference could be found in the scan time of 65 s,50 s and 75 s for the tumor in the pancreatic body and tail.Conclusions The recommended delay time interval for localizing the tumor in pancreatic head by CT enhanced scanning was 45 ～ 55 s,and for the tumor in the pancreatic body or tail was 50 ～75 s.