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Follow-up assessment of vestibular schwannomas: volume quantification versus two-dimensional measurements.

van de Langenberg R, de Bondt BJ, Nelemans PJ, Baumert BG, Stokroos RJ - Neuroradiology (2009)

Bottom Line: Two-dimensional and volume measurements both showed best reproducibility on CE T1-weighted images.Volume measurements are more accurate compared to two-dimensional measurements for the evaluation of VS growth.SDD (%) strongly depends on VS size.

View Article: PubMed Central - PubMed

Affiliation: Department of Otorhinolaryngology-Head and Neck Surgery, Maastricht University Medical Center, P.O. Box 5800, 6202 AZ, Maastricht, The Netherlands. rickvandelangenberg@hotmail.com

ABSTRACT

Introduction: A conservative treatment strategy is often proposed as a primary treatment option in the management of vestibular schwannomas (VS). In this "wait and scan" policy, audiovestibular symptoms are monitored regularly, and VS growth is measured on consecutive magnetic resonance images (MRI). The aim of this study is validation of two-dimensional versus volume MRI assessment in the longitudinal follow-up of VS and to define tumor growth beyond measurement error.

Methods: MRI scans of 68 consecutive patients with VS were analyzed retrospectively. Two-dimensional and volume measurements on contrast enhanced (CE) T1- and T2-weighted images were performed independently by two readers. Smallest detectable differences (SDD) were calculated, and intraclass correlation coefficients (ICCs) were determined for both assessment methods.

Results: Two-dimensional and volume measurements both showed best reproducibility on CE T1-weighted images. SDD for differences relative to baseline MRI [SDD (%)] for two-dimensional measurements had a higher interobserver error compared to volume measurements (40% versus 19.7%), which decreases when tumor size increases. The ICC for two-dimensional measurements in three directions was 0.947, 0.974, and 0.978 and for volume measurements 0.999.

Conclusion: Volume measurements are more accurate compared to two-dimensional measurements for the evaluation of VS growth. These measurements are assessed preferably on CE T1-weighted images. SDD (%) strongly depends on VS size. SDD between consecutive scans exceeds the common clinical applied criterion of 1 or 2 mm growth to define growth.

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a: Example of area tracing with volume software. Axial contrast-enhanced T1-weighted image shows a right-sided vestibular schwannoma (asterisk) with a large cerebellopontine angle component. The red line is the result of the autotracer which lines the vestibular schwannoma. b Three dimensional representation of a vestibular schwannoma (VS), integrating the surface of all slice intervals. The small intracanalicular (A) and large extracanalicular (B) portion of the VS can easily be identified
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Fig2: a: Example of area tracing with volume software. Axial contrast-enhanced T1-weighted image shows a right-sided vestibular schwannoma (asterisk) with a large cerebellopontine angle component. The red line is the result of the autotracer which lines the vestibular schwannoma. b Three dimensional representation of a vestibular schwannoma (VS), integrating the surface of all slice intervals. The small intracanalicular (A) and large extracanalicular (B) portion of the VS can easily be identified

Mentions: For two-dimensional assessment of VS, the maximum diameter was measured in three diameters: anteroposterior (AP), mediolateral (ML) [including the portion in the internal auditory canal (IAC)], and craniocaudal (CC) (Fig. 1a, b). To establish these dimensions, a digital submillimeter ruler was used. Volume assessment was done on a stereotactic radiotherapy treatment planning station, fitted with iPlan® RT image version 3—Advanced Contouring Workstation (BrainLAB Oncology Solutions, Feldkirchen, Germany). MR images were uploaded in this system, and area tracing software was used to outline the VS on each MR image that contained tumor tissue (Fig. 2a). If there was a sharp contrast with surrounding tissue, the auto brush function (surrounding the VS automatically) was used. Manual segmentation was necessary in cases in which differentiation with surrounding tissue was difficult because of the high sensitivity of this autotracer. Each segmentation result was checked visually. By tracing the VS surface on all slices, the software was able to calculate VS volume (Fig. 2b). Volumetric analysis was expressed in cubic centimeter.Fig 1


Follow-up assessment of vestibular schwannomas: volume quantification versus two-dimensional measurements.

van de Langenberg R, de Bondt BJ, Nelemans PJ, Baumert BG, Stokroos RJ - Neuroradiology (2009)

a: Example of area tracing with volume software. Axial contrast-enhanced T1-weighted image shows a right-sided vestibular schwannoma (asterisk) with a large cerebellopontine angle component. The red line is the result of the autotracer which lines the vestibular schwannoma. b Three dimensional representation of a vestibular schwannoma (VS), integrating the surface of all slice intervals. The small intracanalicular (A) and large extracanalicular (B) portion of the VS can easily be identified
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2710491&req=5

Fig2: a: Example of area tracing with volume software. Axial contrast-enhanced T1-weighted image shows a right-sided vestibular schwannoma (asterisk) with a large cerebellopontine angle component. The red line is the result of the autotracer which lines the vestibular schwannoma. b Three dimensional representation of a vestibular schwannoma (VS), integrating the surface of all slice intervals. The small intracanalicular (A) and large extracanalicular (B) portion of the VS can easily be identified
Mentions: For two-dimensional assessment of VS, the maximum diameter was measured in three diameters: anteroposterior (AP), mediolateral (ML) [including the portion in the internal auditory canal (IAC)], and craniocaudal (CC) (Fig. 1a, b). To establish these dimensions, a digital submillimeter ruler was used. Volume assessment was done on a stereotactic radiotherapy treatment planning station, fitted with iPlan® RT image version 3—Advanced Contouring Workstation (BrainLAB Oncology Solutions, Feldkirchen, Germany). MR images were uploaded in this system, and area tracing software was used to outline the VS on each MR image that contained tumor tissue (Fig. 2a). If there was a sharp contrast with surrounding tissue, the auto brush function (surrounding the VS automatically) was used. Manual segmentation was necessary in cases in which differentiation with surrounding tissue was difficult because of the high sensitivity of this autotracer. Each segmentation result was checked visually. By tracing the VS surface on all slices, the software was able to calculate VS volume (Fig. 2b). Volumetric analysis was expressed in cubic centimeter.Fig 1

Bottom Line: Two-dimensional and volume measurements both showed best reproducibility on CE T1-weighted images.Volume measurements are more accurate compared to two-dimensional measurements for the evaluation of VS growth.SDD (%) strongly depends on VS size.

View Article: PubMed Central - PubMed

Affiliation: Department of Otorhinolaryngology-Head and Neck Surgery, Maastricht University Medical Center, P.O. Box 5800, 6202 AZ, Maastricht, The Netherlands. rickvandelangenberg@hotmail.com

ABSTRACT

Introduction: A conservative treatment strategy is often proposed as a primary treatment option in the management of vestibular schwannomas (VS). In this "wait and scan" policy, audiovestibular symptoms are monitored regularly, and VS growth is measured on consecutive magnetic resonance images (MRI). The aim of this study is validation of two-dimensional versus volume MRI assessment in the longitudinal follow-up of VS and to define tumor growth beyond measurement error.

Methods: MRI scans of 68 consecutive patients with VS were analyzed retrospectively. Two-dimensional and volume measurements on contrast enhanced (CE) T1- and T2-weighted images were performed independently by two readers. Smallest detectable differences (SDD) were calculated, and intraclass correlation coefficients (ICCs) were determined for both assessment methods.

Results: Two-dimensional and volume measurements both showed best reproducibility on CE T1-weighted images. SDD for differences relative to baseline MRI [SDD (%)] for two-dimensional measurements had a higher interobserver error compared to volume measurements (40% versus 19.7%), which decreases when tumor size increases. The ICC for two-dimensional measurements in three directions was 0.947, 0.974, and 0.978 and for volume measurements 0.999.

Conclusion: Volume measurements are more accurate compared to two-dimensional measurements for the evaluation of VS growth. These measurements are assessed preferably on CE T1-weighted images. SDD (%) strongly depends on VS size. SDD between consecutive scans exceeds the common clinical applied criterion of 1 or 2 mm growth to define growth.

Show MeSH
Related in: MedlinePlus