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A novel method for amplitude of radiofrequency field (B1+) mapping based on the Bloch-Siegert shift is presented. Unlike conventionally applied double-angle or other signal magnitude-based methods, it encodes the B(1) information into signal phase, resulting in important advantages in terms of acquisition speed, accuracy, and robustness. The Bloch-Siegert(More)
PURPOSE To use electromagnetic (EM) simulations to study the effects of body type, landmark position, and radiofrequency (RF) body coil type on peak local specific absorption rate (SAR) in 3T magnetic resonance imaging (MRI). MATERIALS AND METHODS Numerically computed peak local SAR for four human body models (HBMs) in three landmark positions (head,(More)
The Shinnar-Le Roux (SLR) radiofrequency (RF) pulse design algorithm is widely used for designing slice-selective RF pulses due to its intuitiveness, optimality, and speed. SLR is limited, however, in that it is only capable of designing one-dimensional pulses played along constant gradients. We present a nonuniform SLR RF pulse design framework that(More)
PURPOSE To investigate the efficacy of passive acoustic screening in the magnetic resonance (MR) environment by reducing direct and indirect MR-related acoustic noise, both from the patient's and health worker's perspective. MATERIALS AND METHODS Direct acoustic noise refers to sound originating from the inner and outer shrouds of the MR imager, and(More)
Current spokes pulse design methods can be grouped into methods based either on sparse approximation or on iterative local (gradient descent-based) optimization of the transverse-plane spatial frequency locations visited by the spokes. These two classes of methods have complementary strengths and weaknesses: sparse approximation-based methods perform an(More)
Broadband linear-phase refocusing pulses were designed with the Shinnar-Le Roux (SLR) transformation and verified experimentally. The design works in several steps: initially, a linear-phase B polynomial is created with the Parks-McClellan/Remez exchange algorithm. The complementary A polynomial required for the SLR transformation is generated with the(More)
PURPOSE to evaluate the influence of bone-conduction in the MR environment compared to a standardized acoustic environment. MATERIALS AND METHODS Acoustic noise is an unwanted side effect of MRI that is commonly tackled with passive hearing protection. In an MR scanner, however, with the patient completely surrounded by the MR sounds and in close contact(More)
In a recent work, we presented a novel method for B 1+ field mapping based on the Bloch-Siegert shift. Here, we apply this method to automated fast radiofrequency transmit gain calibration. Two off-resonance radiofrequency pulses were added to a slice-selective spin echo sequence. The off-resonance pulses induce a Bloch-Siegert phase shift in the acquired(More)
PURPOSE To propose a modified fast spin echo (FSE) magnetic resonance imaging sequence for MR thermometry, employing the proton resonance frequency (PRF) shift by means of MR phase maps. Despite their obvious advantages of speed and high signal-to-noise ratio (SNR), FSE sequences have not until now been used for this purpose due to the restraints imposed by(More)