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

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.

Assessment of pituitary adenoma volumetric change using longitudinal MR image registration

“…Compared to Fig. 1, the net displacement field in (b) does not indicate a volume change shown for vestibular schwannomas [15], while for glioblastomas, any significant difference has not been shown between volumes measured on 2D and 3D scans [16]. Tumor volume change (objective response) is an important endpoint in clinical trials [17].…”

Evaluation of the necessity of contrast for the follow up MR imaging of schwannomas

“…Vestibular schwannoma growth can be demonstrated by volumetric studies or diameter measurements (2,15). Studies in the literature have shown that diameter measurements can be used instead of volumetric measurements to compare tumor size (15,16).…”

“…MRI is the imaging technique used in the conservative management of vestibular schwannomas (2,3). T1W sequences with a gadolinium-based contrast agent are the gold standard for the initial detection and follow-up examinations of these tumors (5, 7).…”

The evolving role of neurological imaging in neuro-oncology

“…This has been suggested to increase accuracy and inter-rater reliability. A study by van de Langenberg et al [5] considered 68 patients with vestibular schwannomas and compared growth using both two-dimensional and volumetric MRI measurements and found that interobserver error using bi-dimensional measurements was more than twice the volumetric inter-observer error rate. A randomized control trial for motexafin in brain metastasis in which tumor response rates were analyzed using different measurements found a 50 % reduction of tumor using bi-dimensional measures versus a 65 % reduction of tumor using volumetric measures [6].…”