Image reconstruction in SNR units: A general method for SNR measurement

• Published in: Magnetic resonance in medicine Vol. 54; no. 6; pp. 1439 - 1447
• Main Authors: Kellman, Peter, McVeigh, Elliot R.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.12.2005
• Subjects: Algorithms; Computer Simulation; Image Enhancement - methods; Image Interpretation, Computer-Assisted - methods; Information Storage and Retrieval - methods; Magnetic Resonance Imaging - instrumentation; Magnetic Resonance Imaging - methods; Models, Biological; Models, Statistical; MRI; noise; parallel MRI; Phantoms, Imaging; phased array; Reproducibility of Results; SENSE; Sensitivity and Specificity; Signal Processing, Computer-Assisted; SNR measurement; Stochastic Processes
• ISSN: 0740-3194; 1522-2594; 1522-2594
• DOI: 10.1002/mrm.20713

The method for phased array image reconstruction of uniform noise images may be used in conjunction with proper image scaling as a means of reconstructing images directly in SNR units. This facilitates accurate and precise SNR measurement on a per pixel basis. This method is applicable to root‐sum‐of‐squares magnitude combining, B1‐weighted combining, and parallel imaging such as SENSE. A procedure for image reconstruction and scaling is presented, and the method for SNR measurement is validated with phantom data. Alternative methods that rely on noise only regions are not appropriate for parallel imaging where the noise level is highly variable across the field‐of‐view. The purpose of this article is to provide a nuts and bolts procedure for calculating scale factors used for reconstructing images directly in SNR units. The procedure includes scaling for noise equivalent bandwidth of digital receivers, FFTs and associated window functions (raw data filters), and array combining. Magn Reson Med, 2005. Published 2005 Wiley‐Liss, Inc.