The standard method for measuring the slice thickness of magnetic resonance images uses the inclined surface of a wedge (wedge method); it is sensitive to small increases in noise because of the differentiation of the edge response function (ERF) required. The purpose of this study was to improve the wedge method by fitting a curve to the ERF. The curve-fit function was obtained by convolving an ideal ERF (a ramp function) with a Gaussian function to represent ERF blurring. Measurements of 5- and 3-mm slice thicknesses were performed on a 3T scanner using the conventional wedge method, the improved wedge method, and another standard method using an inclined slab (slab method). Subsequently, 0.5- and 0.25-mm slice thicknesses from multiple slices acquired using a three-dimensional sequence were measured using the improved wedge method. When measuring 5-mm slices, the differences in measurements obtained using the improved wedge method and the conventional slab and wedge methods were very small: <0.6% of the 5-mm slice thickness. The difference was ≤1.7% for 3-mm slices. For 0.5- and 0.25-mm slices, the mean values obtained using the improved wedge method were 0.543 ± 0.007 mm and 0.247 ± 0.015 mm, with a 1.2 and 5.9% coefficient of variation across slices, respectively. The improved wedge method is valid and potentially applicable to the measurement of sub-millimeter slice thicknesses.
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Fischbach F, Müller M, Bruhn H. High-resolution depiction of the cranial nerves in the posterior fossa (N III-N XII) with 2D fast spin echo and 3D gradient echo sequences at 3.0 T. Clin Imaging. 2009;33:169–74.
Simon JH, Li D, Traboulsee A, Coyle PK, Arnold DL, Barkhof F, Frank JA, Grossman R, Paty DW, Radue EW, Wolinsky JS. Standardized MR imaging protocol for multiple sclerosis: consortium of MS centers consensus guidelines. Am J Neuroradiol. 2006;27:455–61.
Sasaki M, Inoue T, Tohyama K, Oikawa H, Ehara S, Ogawa A. High-field MRI of the central nervous system: current approaches to clinical and microscopic imaging. Magn Reson Med Sci. 2003;2:133–9.
Yue Y, Jin Y, Yang B, Yuan H, Li J, Wang Z. Retrospective case series of the imaging findings of facial nerve hemangioma. Eur Arch Otorhinolaryngol. 2015;272:2497–503.
Tuleasca C, Carron R, Resseguier N, Donnet A, Roussel P, Gaudart J, Levivier M, Régis J. Decreased probability of initial pain cessation in classic trigeminal neuralgia treated with gamma knife surgery in case of previous microvascular decompression: a prospective series of 45 patients With >1 Year of follow-up. Neurosurgery. 2015;77:87–94.
Docampo J, Gonzalez N, Muñoz A, Bravo F, Sarroca D, Morales C. Neurovascular study of the trigeminal nerve at 3 T MRI. Neuroradiol J. 2015;28:28–35.
Association National Electrical Manufacturers. NEMA standards publications MS 5-2010, Determination of slice thickness in diagnostic magnetic resonance imaging. Rosslyn: National Electrical Manufacturers Association; 2010.
Och JG, Clarke GD, Sobol WT, Rosen CW, Mun SK. Acceptance testing of magnetic resonance imaging systems: report of AAPM nuclear magnetic resonance Task Group No. 6. Med Phys. 1992;19:217–29.
Price RR, Axel L, Morgan T, Newman R, Perman W, Schneiders N, Selikson M, Wood M, Thomas SR. Quality assurance methods and phantoms for magnetic resonance imaging: report of AAPM nuclear magnetic resonance Task Group No. 1. Med Phys. 1990;17:287–95.
Selikson M, Fearon T. Averaging error in NMR slice profile measurements. Magn Reson Med. 1988;7:280–4.
Lerski RA, de Certaines JD. Performance assessment and quality control in MRI by Eurospin test objects and protocols. Magn Reson Imaging. 1993;11:817–33.
Firbank MJ, Harrison RM, Williams ED, Coulthard A. Quality assurance for MRI: practical experience. Br J Radiol. 2000;73:376–83.
Lerski RA. An evaluation using computer simulation of two methods of slice profile determination in MRI. Phys Med Biol. 1989;34(12):1931–7.
Ohkubo M, Wada S, Kunii M, Matsumoto T, Nishizawa K. Imaging of small spherical structures in CT: simulation study using measured point spread function. Med Biol Eng Comput. 2008;46:273–82.
Yoshida R, Machida Y, Ogura T, Tamura H, Hikichi T, Mori I. Slice profile measurement using a crossed thin-ramps method in three-dimensional magnetic resonance imaging. Nihon Hoshasen Gijutsu Gakkai Zasshi. 2012;68:1456–66 (in Japanese).
We thank Libby Cone, MD, MA, from Edanz Group Japan (www.edanzediting.com/ac) for editing drafts of this manuscript.
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Kanazawa, T., Ohkubo, M., Kondo, T. et al. Improved wedge method for the measurement of sub-millimeter slice thicknesses in magnetic resonance imaging. Radiol Phys Technol 10, 446–453 (2017). https://doi.org/10.1007/s12194-017-0417-2
- Magnetic resonance imaging/MT
- Slice thickness
- Wedge method
- Slab method
- Edge response function
- Slice profile