Delineation Of Gross Tumor Volume Of Esophageal Cancers On CT Images: Study Of Accuracy And Consistency In Length Of Primary Tumor

PartⅠ:Observation of Normal Appearance and Wall Thickness of Esophagus on CT ImagesPurpose:This study sought to observe the appearance of normal esophagus,measure and record the thickness of esophageal wall in order to offer reference for estimating esophageal wall abnormalities and delineating gross tumor target of esophageal carcinomas on CT images.Materials and methods:From September 2006 to February 2007,110 consecutive CT films from adult patients without esophageal diseaseswere collected and studied.On CT images the entire esophaguswas divided into cervical,thoracic,retrocardiac and intraabdominal segments.The appearance of esophagus was described when the esophagus contracted or dilated.Thickness of esophageal wall and diameters of esophageal cavities were measured by hard-copy reading with a magnifying glass.Age, sex and the thickness of subcutaneous fat of each patient were recorded.Results:It was observed that the esophagus presented both contracted and dilated status on CT images.In each segment there were certain portions of esophagus in complete contraction or dilatation.47 images(42.7%) showed contracted esophagus in each segment available for measurement.The largest wall thickness when esophagus was in contraction and dilatation was 4.70(95%CI:4.44-4.95)mm and 2.11 (95%CI:2.00-2.23)mm,respectively.When contracting,the intraabdominal esophagus was thicker than the cervical,thoracic and retrocardiac parts,and the average thickness was 5.68(95%CI:5.28-6.09)mm,4.67(95%CI:4.36-4.86)mm, 4.56(95%CI:4.31-4.87)mm,and 4.05(95%CI:3.71-4.21)mm,respectively.When the esophagus was dilating,the average esophageal wall thickness was between 1.87 and 2.70mm.The thickest part was cervical esophagus.Thickness of esophageal wall was larger in males than that of females(5.26mm vs.4.34mm p＜0.001).Age and the thickness of subcutaneous fat had no significant impact on the thickness of esophageal wall(p-value was 0.056 and 0.173,respectively).Conclusion:The observation of normal appearance and wall thickness of esophagus helps us to identify thickened esophageal wall on CT images using new CT scan technologies.Thus it is probably helpful in judging esophageal diseases and delineating gross tumor target of esophageal carcinomas in modern radiotherapy. PartⅡ:Lesion Lengths of Esophageal Cancer on CT Images,Barium Esophagram, Esophagoscopy and Surgical Specimens:Quantitative Comparisons and Clinical DiscussionPurpose:To compare the lengths of the primary lesion of esophageal cancer on CT images,barium esophagram,and corresponding lengths acquired from esophagoscopy and surgical specimens;to evaluate the differences among them;to discuss possible relationships between the parameters above and their potential clinical usage.Materials and methods:Medical data of 79 patients with esophageal cancers were reviewed retrospectively.CT and esophagram films were evaluated by two Radiation Oncologists and the lesion lengths were recorded as L_CT and L_X respectively.Lesion types on esophagram and lengths of complete circumference involvement on CT images(Lq) were identified.L_CT-X was refered to the length that lesion length given on CT images exceeded that given by esophagram.Lesion length on esophagoscopy and surgical specimens were recorded as Le and Lp respectively.On-body tumor length(Ls) was calculated by Lp divided by retraction rate which was 0.8 according to literatures.Compare the differences among L_CT,L_X,Le,Lp and Ls by paired test and analyse the influences of lesion characteristics on L_CT-X.by one-way anova.Results:Means of L_CT,L_X,Ls,Le and Lp were 6.39±2.98cm,4.87±1.99cm,4.38±2.03cm,4.10±1.85cm,3.50±1.62cm respectively.Mean of L_CT was 1.5cm larger than that of L_X with statistical significance(p＜0.001),and was 2cm larger than that of Ls with statistical significance(p＜0.001).Within the 53 patients where the tumor lengths on esophascopy were reported,mean of L_CT was 2.3cm larger than that of Le with statistical significance(p＜0.001).The differences between L_X and either Ls or Le were statistically significant(p value were 0.005 and 0.003 respectively),while the difference between Le and Ls was not statistically significant(p=0.738).L_CT-X varied according to tumor staging and the differences among groups of different T stages were statistically significant(p=0.020).L_CT-X were -0.21±0.81cm,1.54±1.50cm,1.76±1.61cm,1.75±1.19cm respectively at T1,T2,T3,T4 staging tumors,but difference of L_CT-X between T3/4 and T2 tumors did not show statistical significance(p=0.542).L_CT-X varied at different types of lesions.Lesions of fungating type had the smallest L_CT-X and the differences were statistically significant when compared with infiltrating type,ulcerating type and contrictive type. L_CT-X at proximal end was smaller than that at distal end and their difference was of statistical significance(p=0.033).There was linear correlation between Lq and L_CT-X (p＜0.001) and the correlation coefficient was 0.421.Conclusion:Lesion lengths of esophageal cancer on CT images were larger than those from esophagram,esophagoscopy,surgical specimens and extrapolated on-body tumor lengths.The differences between CT images and esophagram were related to lesion characteristics such as T staging,types on X-ray images,and lengths of complete circumference involvement.Such differences at proximal ends were smaller than those at distal ends.Further studies should be carried out to identify if the lesion length on CT images exceeding esophagram and other examinations would be sub-mucosal infiltration of the primary tumor. PartⅢ:Compare Consistencies of Gross Tumor Volumes of Esophageal Cancers on Images From Enhanced CT Scanning After 654-2 Intramuscular Injection With Those From Plain ScanningPurpose:Compare consistencies of gross tumor volumes of esophageal cancers on images from enhanced CT scanning after 654-2 intramuscular injection with those from plain scanning.Identify if the method of 654-2 intramuscular injection would help to dilate esophagus and further improve the consistency of tumor length delineation.Materials and methods:Cytologically or histopathological confirmed esophageal cancer patients were enrolled prospectively.Each patients had underwent simulation CT scanning twice at the same posture.The first simulation was plain scanning(C-) while the second one was enhanced scanning with 10mg 654-2 intramuscular injection 10-15 minutes before(C+).Three doctors of high seniority and three doctors of low seniority preformed the gross tumor volumes delineation independently.The gross tumor volumes were defined as GTV1-GTV6,of which the lengths were refered to L1-L6 and the volumes were V1-V6.The intersection part of either lengths or volumes divided by their union part was defined as Conformable Index(CI).Coefficient of variation of either lengths or volumes of GTVs were recorded as CV.Thus consistency of GTVs increased if CI increased or CV decreased.CI and CV were compared between two groups of different simulation methods(C- or C+) and doctors of different seniority using paired tests.Results:Within 15 patients enrolled,the method of 654-2 injection bring esophagus dilation in 2 more case at proximal end of the tumor and 6 more cases at distal end.L_CI of C- and C+ groups were 45±12%and 59±19%respectively and the differences between two groups was statistically significant(p=0.008).L_CV of C- and C+ groups were 0.26±0.09 and 0.18±0.13 respectively and the differences was also statistically significant(p=0.015).Both in C- and C+ group high seniority doctors presented higher L_CI than low seniority doctors,but with no statistical significance(p value were 0.552 and 0.109 respectively).Both among high seniority and low seniority doctors L_CI was higher in C+ group than that of C-,the differences were approaching statistical significance(p value were 0.071 and 0.053 respectively).V_CI of C- and C+ groups were 32±9%and 35±11%respectively and the difference between two groups was not statistically significant(p=0.349).V_CV of C- and C+ groups were 0.206±0.09 and 0.209±0.09 respectively and the difference was not statistically significant(p=0.919).Conclusion:654-2 intramuscular injection helped to dilate esophagus and helped doctors to judge esophageal cancer lesions on CT images.This method may increase consistency of tumor lengths delineation when used before enhanced CT scanning in esophageal cancer simulation.