title: Reliability of the Size Evaluation Method for Meningiomas: Maximum Diameter, ABC/2 Formula, and Planimetry Method.
abstract: BACKGROUND
  To evaluate the accuracy of tumor size by maximum diameter, ABC/2 formula, and planimetry method using thick-slice and thin-slice magnetic resonance imaging (MRI).
  
  
  METHODS
  Maximum diameter and tumor volume calculated using ABC/2 formula (V1) and planimetry method with thick-slice MRI (V2) and thin-slice MRI (V3) were examined in 83 meningiomas. Form factor (FF) analysis was performed to assess irregularity of the tumor. V3 values were considered as real tumor volumes. The accuracy of V1 and V2 was evaluated using ratio and difference from V3. Meningiomas were categorized by tumor locations: skull base (anterior, middle, and posterior) and non-skull base (calvaria and other sites).
  
  
  RESULTS
  Correlation between maximum diameter and V3 was statistically significant (r = 0.91), but the error was significant in tumors with longer maximum diameters. Correlation between V1 and V3 was significant (r = 0.97). However, V1 tended to be larger in middle skull base meningiomas or in tumors with low FF values (R2= 0.21). V2 represented relatively accurate volumes in both groups except in the case of small meningiomas. When tumors were demonstrated within 3 fractions on thick-slice MRI, the ratio of V2 to V3 showed significant variability.
  
  
  CONCLUSIONS
  Using the ABC/2 formula, the volume of meningiomas in the middle skull base or meningiomas with low FF value might be calculated larger than the real tumor volume. The planimetry method with thick-slice MRI demonstrated relatively accurate volumes if the tumor was fractionated in >4 slices.
authors.affiliation: Department of Neurosurgery, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
authors.forename: Yukitomo
authors.initials: Y
authors.lastname: Ishi
authors.affiliation: Department of Neurosurgery, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Terasaka
authors.affiliation: Department of Neurosurgery, Hokkaido University Graduate School of Medicine, Sapporo, Japan. Electronic address: syamama1945@gmail.com.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Yamaguchi
authors.affiliation: Department of Neurosurgery, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
authors.forename: Michiharu
authors.initials: M
authors.lastname: Yoshida
authors.affiliation: Department of Neurosurgery, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
authors.forename: Shogo
authors.initials: S
authors.lastname: Endo
authors.affiliation: Department of Neurosurgery, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kobayashi
authors.affiliation: Department of Neurosurgery, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
authors.forename: Kiyohiro
authors.initials: K
authors.lastname: Houkin
mesh_terms: D001932:Brain Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D005163:Factor Analysis, Statistical; D006801:Humans; D008279:Magnetic Resonance Imaging; D008577:Meningeal Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D008579:Meningioma / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D019635:Neurosurgical Procedures; D015203:Reproducibility of Results; D019292:Skull Base Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D047368:Tumor Burden
keywords: ABC/2 formula; Maximum diameter; Meningioma; Planimetry method; Volumetric analysis