Non Uniformity Correction Using Cosine Functions and Total Variation Constraint in Musculoskeletal Nmr Imaging
نویسندگان
چکیده
Introduction: In this work, we attempted to correct the non-uniformities generated in lower limbs (calf and thigh) NMRI by RF inhomogeneities. Correction techniques are based in general on prior knowledge about the intensity distribution inside tissues (or tissue magnetic properties) which is not straightforward in case of pathological muscles, as in neuro-muscular disorders. For our application, we can rely only on the assumption of signal uniformity in the subcutaneous fat and we need to estimate the non uniformity values in muscles. An interpolation technique like spline or polynomial would not be efficient because the muscle area is large relative to fat. Parametric models are an attractive solution to the problem. Based on the observation that the non uniformity field is a low frequency signal, we expressed it as a finite sum of discrete cosine functions. The estimation of the parameters of the non uniformity field was done through the minimization of a convex cost function.
منابع مشابه
Evaluation of B1 Receive Non-uniformity Correction Techniques for Quantitative Musculoskeletal Nmr Imaging
1. Introduction: To be able de detect early pathological changes with high sensitivity, precision and reproducibility in diseased muscles, one needs to turn to truly
متن کاملAssessment of the Characteristics of MRI Coils in Terms of RF Non-Homogeneity Using Routine Spin Echo Sequences
Introduction: One of the major causes of image non-uniformity in MRI is due to the existence of non-homogeneity in RF receive and transmit. This can be the most effective source of error in quantitative studies in MRI imaging. Part of this non-homogeneity demonstrates the characteristics of RF coil and part of it is due to the interaction of RF field with the material being imaged...
متن کاملNew approach for calibration of pixelated scintillation detectors of intraoperative gamma cameras
Introduction:SURGEOSIGHT is a dedicated intra-operative hand-held gamma camera designed and manufactured by our team to be used for lymphoscintigraphy. Although conventional gamma cameras are widely used, they lack the capability of the sentinel lymph node (SLN) imaging in the operation room. Like conventional gamma cameras it is necessary to calibrate SURGEOSIGHT for linearity...
متن کاملNon-uniformity of Clinical Head, Head and Neck, and Body Coils in Magnetic Resonance Imaging (MRI)
Introduction Signal intensity uniformity in a magnetic resonance (MR) image indicates how well the MR imaging (MRI) system represents an object. One of the major sources of image non-uniformity in high-field MRI scanners is inhomogeneity of radio-frequency coil. The aim of this study was to investigate non-uniformity in head, head and neck, and body coils and compare the obtained results to det...
متن کاملThe Sine-Cosine Wavelet and Its Application in the Optimal Control of Nonlinear Systems with Constraint
In this paper, an optimal control of quadratic performance index with nonlinear constrained is presented. The sine-cosine wavelet operational matrix of integration and product matrix are introduced and applied to reduce nonlinear differential equations to the nonlinear algebraic equations. Then, the Newton-Raphson method is used for solving these sets of algebraic equations. To present ability ...
متن کامل