Vestibular schwannomas: Accuracy of tumor volume estimated by ice cream cone formula using thin-sliced MR images
February
Vestibular schwannomas: Accuracy of tumor volume estimated by ice cream cone formula using thin-sliced MR images
Hsing-Hao Ho 0 1
Ya-Hui Li 0 1
Jih-Chin Lee 1
Chih-Wei Wang 0 1
Yi-Lin Yu 1
Dueng- Yuan Hueng 1
Hsin-I Ma 1
Hsian-He Hsu 0 1
Chun-Jung Juan 0 1
0 Department of Radiology, Tri-Service General Hospital , Taipei, Taiwan , 2 Department of Radiology, National Defense Medical Center , Taipei, Taiwan , 3 Department of Otolaryngology-Head and Neck Surgery, Tri-Service General Hospital , Taipei, Taiwan , 4 Department of Otolaryngology-Head and Neck Surgery, National Defense Medical Center , Taipei, Taiwan , 5 Department of Neurological Surgery, Tri-Service General Hospital , Taipei, Taiwan , 6 Department of Neurological Surgery, National Defense Medical Center , Taipei, Taiwan , 7 Department of Biochemistry, National Defense Medical Center , Taipei , Taiwan
1 Editor: Girish Bathla, University of Iowa , UNITED STATES
-
Data Availability Statement: All relevant data are
within the paper and its Supporting Information
files.
Funding: C.J.J. was partially supported by the
Ministry of Science and Technology of Taiwan
(https://www.most.gov.tw)
(MOST-105-2314-B016-024-MY2) for attending the 55th Annual
Meeting of the American Society of Neuroradiology
for presentation of part of this study and for the
PLOS publication fee. The funder had no role in
Purpose
Methods
We estimated the volume of vestibular schwannomas by an ice cream cone formula using
thin-sliced magnetic resonance images (MRI) and compared the estimation accuracy
among different estimating formulas and between different models.
The study was approved by a local institutional review board. A total of 100 patients with
vestibular schwannomas examined by MRI between January 2011 and November 2015
were enrolled retrospectively. Informed consent was waived. Volumes of vestibular
schwannomas were estimated by cuboidal, ellipsoidal, and spherical formulas based on a
one-component model, and cuboidal, ellipsoidal, Linskey's, and ice cream cone formulas based on a
two-component model. The estimated volumes were compared to the volumes measured
by planimetry. Intraobserver reproducibility and interobserver agreement was tested.
Estimation error, including absolute percentage error (APE) and percentage error (PE), was
calculated. Statistical analysis included intraclass correlation coefficient (ICC), linear
regression analysis, one-way analysis of variance, and paired t-tests with P < 0.05 considered
statistically significant.
Results
Overall tumor size was 4.80 ± 6.8 mL (mean ±standard deviation). All ICCs were no less
than 0.992, suggestive of high intraobserver reproducibility and high interobserver
agreement. Cuboidal formulas significantly overestimated the tumor volume by a factor of 1.9 to
2.4 (P
0.001). The one-component ellipsoidal and spherical formulas overestimated the
tumor volume with an APE of 20.3% and 29.2%, respectively. The two-component ice
study design, data collection and analysis, decision
to publish, or preparation of the manuscript.
Competing interests: The authors declare that no
competing interests exist.
cream cone method, and ellipsoidal and Linskey's formulas significantly reduced the APE to
11.0%, 10.1%, and 12.5%, respectively (all P < 0.001).
Conclusion
The ice cream cone method and other two-component formulas including the ellipsoidal and
Linskey's formulas allow for estimation of vestibular schwannoma volume more accurately
than all one-component formulas.
Introduction
Vestibular schwannomas are benign tumors that arise most commonly from the nerve sheath
of the vestibular portion of cranial nerve VIII [
1
]. Size of the vestibular schwannomas is a
factor influencing the choice of treatment [2±5]. Small vestibular schwannomas can be either
managed conservatively [
6
] or treated by radiosurgery [
3, 7
], while large vestibular
schwannomas often require surgical intervention. According to the International RadioSurgery
Association (IRSA) guidelines, in general, radiosurgery is effective for vestibular schwannomas less
than 3 cm in diameter, while microsurgery is the first choice for vestibular schwannomas
larger than 3 cm in diameter [8]. Tumor size has been used as an important prognostic factor
for preserving cochlear and facial nerve function [
5, 9, 10
]. Change of tumor size has been
used as an indicator of treatment response [
11
]. Moreover, it must be followed in patients
receiving either conservative or aggressive treatments [
10, 12
].
In vestibular schwannomas, tumor volume can be measured based on slice-by-slice
planimetry [
13, 14
]. Although planimetry has been regarded as the standard method in measuring
vestibular schwannoma volume, it is rather time-consuming [15] and not convenient in daily
practice. Alternatively, the tumor size can be estimated rapidly based on cuboidal [
16, 17
],
spherical [18], or ellipsoidal [13±15, 17, 19±23] formulas based on either one- (...truncated)