Estimating postoperative skull defect volume from CT images using the ABC method.
OBJECTIVE
Surgeons often perform decompressive craniectomy to alleviate a medically-refractory increase of intracranial pressure. The frequency of this type of surgery is on the rise. The goal of this study is to develop a simple formula for clinicians to estimate the volume of the skull defect, based on postoperative computed tomography (CT) studies.


METHODS
We collected thirty sets of postoperative CT images from patients undergoing craniectomy. We measured the skull defect volume by computer-assisted volumetric analysis (V(m)) and our own ABC technique (V(abc)). We then compared the volumes measured by these two methods.


RESULTS
The V(m) ranged from 3.2 to 76.4 mL, with a mean of 38.9 mL. The V(abc) ranged from 3.8 to 71.5 mL, with a mean of 38.5 mL. The absolute differences between V(abc) and V(m) ranged from 0.05 to 17.5 mL (mean: 3.8±4.2). There was no statistically significant difference between V(abc) and V(m) (p=0.961). The correlation coefficient between V(abc) and V(m) was 0.969. In linear regression analysis, the slope was 1.00086 and the intercept was -0.0035 mL (r(2)=0.939). The residual was 5.7 mL.


CONCLUSIONS
We confirmed that the ABC technique is a simple and accurate method for estimating skull defect volume, and we recommend routine application of this formula for all decompressive craniectomies.
Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan.
Furen
F
Xiao
I-Jen
IJ
Chiang
Thomas Mon-Hsian
TM
Hsieh
Ke-Chun
KC
Huang
Yi-Hsin
YH
Tsai
Jau-Min
JM
Wong
Hsien-Wei
HW
Ting
Chun-Chih
CC
Liao
D000465:Algorithms; D003399:Craniotomy / Q000379:methods*; D019299:Decompression, Surgical / Q000379:methods*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D019586:Intracranial Hypertension / Q000209:etiology / Q000601:surgery; D016014:Linear Models; D019635:Neurosurgical Procedures / Q000379:methods*; D011184:Postoperative Period; D015203:Reproducibility of Results; D012886:Skull / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed