Effects of slice thickness and head rotation when measuring glioma sizes on MRI: in support of volume segmentation versu
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LABORATORY INVESTIGATION
Effects of slice thickness and head rotation when measuring glioma sizes on MRI: in support of volume segmentation versus two largest diameters methods Pierre Schmitt • Emmanuel Mandonnet Adrien Perdreau • Elsa D. Angelini
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Received: 2 August 2012 / Accepted: 29 December 2012 / Published online: 9 February 2013 Springer Science+Business Media New York 2013
Abstract This paper presents a study of the effects of scanning parameters variability when assessing glioma sizes on MRI. A database of lesions of various shapes and sizes, segmented on 3D-SPGR MRI images, was acquired on 65 patients with low-grade glioma. Simulations of large slice thickness and patient’s head rotation were performed, allowing us to study their influence on two size indices: the bi-dimensional diameter product index (computed with the two largest diameters method) and the equivalent diameter index (computed with the volume segmentation method). Results show that thick slices and axial plane rotation can induce average (maximal) uncertainties on the bi-dimensional diameter product index between 32 and 6 % (150 %) for small and large tumors (size range 0.5–286 ml). The uncertainty on the equivalent diameter index, for the same categories of tumors, drops below 8 and 0.1 % (23 %). This study shows that the volume segmentation method is subject to less variability inherent to scanning conditions compared to the two largest diameters method. It also emphasizes the need for strict clinical guidelines on the replication of scanning conditions when performing MRI follow-ups on patients harboring small tumors. These
P. Schmitt A. Perdreau E. D. Angelini (&) Institut Mines-Telecom, Telecom ParisTech, CNRS LTCI, 46 Rue Barrault, 75013 Paris, France e-mail: [email protected] P. Schmitt e-mail: [email protected] A. Perdreau e-mail: [email protected] E. Mandonnet Neurosurgery Department, Hoˆpital Lariboisie`re, Paris, France e-mail: [email protected]
implications await confirmation on a series of real patients being re-scanned with FLAIR MRI. Keywords MRI Brain tumor Low-grade glioma Longitudinal growth quantification
Introduction Assessing the evolution of tumor size by morphological longitudinal MRI follow-up plays a prominent role in neuro-oncology. This holds especially true for diffuse lowgrade glioma, as radiological evolution is often the only measure available to capture the disease progression before treatment [1–3], after surgery [4], after chemotherapy [5, 6] or after radiotherapy [7]. Testifying to the importance of the analysis of radiological changes on MRI when evaluating treatment efficacy, the response assessment in neuro-oncology (RANO) group recently updated the original definition of the MacDonalds criteria of radiological response for the specific case of low-grade glioma [8]. These revised criteria now rely on the measure of the two largest tumor diameters (i.e linear measurements). Other authors recommend a full 3D-segmentation of the tumor on all
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