title: Pancreatic mucinous cystic neoplasm size using CT volumetry, spherical and ellipsoid formulas: validation study.
abstract: BACKGROUND
  The accuracy for determining pancreatic cyst volume with commonly used spherical and ellipsoid methods is unknown. The role of CT volumetry in volumetric assessment of pancreatic cysts needs to be explored.
  
  
  OBJECTIVE
  To compare volumes of the pancreatic cysts by CT volumetry, spherical and ellipsoid methods and determine their accuracy by correlating with actual volume as determined by EUS-guided aspiration. Setting This is a retrospective analysis performed at a tertiary care center. Patients Seventy-eight pathologically proven pancreatic cysts evaluated with CT and endoscopic ultrasound (EUS) were included. Design The volume of fourteen cysts that had been fully aspirated by EUS was compared to CT volumetry and the routinely used methods (ellipsoid and spherical volume). Two independent observers measured all cysts using commercially available software to evaluate inter-observer reproducibility for CT volumetry.
  
  
  METHODS
  The volume of pancreatic cysts as determined by various methods was compared using repeated measures analysis of variance. Bland-Altman plot and intraclass correlation coefficient were used to determine mean difference and correlation between observers and methods. The error was calculated as the percentage of the difference between the CT estimated volumes and the aspirated volume divided by the aspirated one.
  
  
  RESULTS
  CT volumetry was comparable to aspirated volume (P=0.396) with very high intraclass correlation (r=0.891, P<0.001) and small mean difference (0.22 mL) and error (8.1%). Mean difference with aspirated volume and error were larger for ellipsoid (0.89 mL, 30.4%; P=0.024) and spherical (1.73 mL, 55.5%; P=0.004) volumes than CT volumetry. There was excellent inter-observer correlation in volumetry of the entire cohort (r=0.997, P<0.001).
  
  
  CONCLUSIONS
  CT volumetry is accurate and reproducible. Ellipsoid and spherical volume overestimate the true volume of pancreatic cysts.
authors.affiliation: Department of Radiology, Feinberg School of Medicine, Northwestern University. Chicago, IL, USA. hamid.chalian@gmail.com.
authors.forename: Hamid
authors.initials: H
authors.lastname: Chalian
authors.forename: Adeel Rahim
authors.initials: AR
authors.lastname: Seyal
authors.forename: Pedram
authors.initials: P
authors.lastname: Rezai
authors.forename: Hüseyin Gürkan
authors.initials: HG
authors.lastname: Töre
authors.forename: Frank H
authors.initials: FH
authors.lastname: Miller
authors.forename: David J
authors.initials: DJ
authors.lastname: Bentrem
authors.forename: Vahid
authors.initials: V
authors.lastname: Yaghmai
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D018282:Cystadenocarcinoma, Mucinous / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D018291:Cystadenoma, Mucinous / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D010181:Pancreatic Cyst / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D010192:Pancreatic Pseudocyst / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D015203:Reproducibility of Results; D013396:Suction; D014057:Tomography, X-Ray Computed; D047368:Tumor Burden; D014463:Ultrasonography; D055815:Young Adult