Vestibular schwannomas: Accuracy of tumor volume estimated by ice cream cone formula using thin-sliced MR images

PLOS ONE, Nov 2019

Purpose 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. Methods 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 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.

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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)


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Hsing-Hao Ho, Ya-Hui Li, Jih-Chin Lee, Chih-Wei Wang, Yi-Lin Yu, Dueng-Yuan Hueng, Hsin-I Ma, Hsian-He Hsu, Chun-Jung Juan. Vestibular schwannomas: Accuracy of tumor volume estimated by ice cream cone formula using thin-sliced MR images, PLOS ONE, 2018, Volume 13, Issue 2, DOI: 10.1371/journal.pone.0192411