Intersubject specific absorption rate variability analysis through construction of 23 realistic body models for prostate imaging at 7T

For ultrahigh field (UHF) MRI, the expected local specific absorption rate (SAR) distribution is usually calculated by numerical simulations using a limited number of generic body models and adding a safety margin to take into account intersubject variability. Assessment of this variability with a large model database would be desirable. In this study, a procedure to create such a database with accurate subject‐specific models is presented. Using 23 models, intersubject variability is investigated for prostate imaging at 7T with an 8‐channel fractionated dipole antenna array with 16 receive loops.

[1]  Gabriele Eichfelder,et al.  Local specific absorption rate control for parallel transmission by virtual observation points , 2011, Magnetic resonance in medicine.

[2]  K. Caputa,et al.  An algorithm for computations of the power deposition in human tissue , 1999 .

[3]  Gregory J. Metzger,et al.  A 16‐channel combined loop‐dipole transceiver array for 7 Tesla body MRI , 2017, Magnetic resonance in medicine.

[4]  C A T van den Berg,et al.  Design of a radiative surface coil array element at 7 T: The single‐side adapted dipole antenna , 2011, Magnetic resonance in medicine.

[5]  Peter R Luijten,et al.  The fractionated dipole antenna: A new antenna for body imaging at 7 Tesla , 2016, Magnetic resonance in medicine.

[6]  Özlem Ipek,et al.  Intersubject local SAR variation for 7T prostate MR imaging with an eight‐channel single‐side adapted dipole antenna array , 2014, Magnetic resonance in medicine.

[7]  Ravi S. Menon,et al.  Imaging at high magnetic fields: initial experiences at 4 T. , 1993, Magnetic resonance quarterly.

[8]  D Le Bihan,et al.  kT‐points: Short three‐dimensional tailored RF pulses for flip‐angle homogenization over an extended volume , 2012, Magnetic resonance in medicine.

[9]  Peter Börnert,et al.  A specific absorption rate prediction concept for parallel transmission MR , 2012, Magnetic resonance in medicine.

[10]  Gillian Haemer,et al.  Mixing loops and electric dipole antennas for increased sensitivity at 7 Tesla , 2012 .

[11]  Michel Luong,et al.  Probabilistic analysis of the specific absorption rate intersubject variability safety factor in parallel transmission MRI , 2017, Magnetic resonance in medicine.

[12]  Alexander Hammers,et al.  Tailored excitation in 3D with spiral nonselective (SPINS) RF pulses , 2012, Magnetic resonance in medicine.

[13]  Niels Kuster,et al.  Virtual population‐based assessment of the impact of 3 Tesla radiofrequency shimming and thermoregulation on safety and B1+ uniformity , 2016, Magnetic resonance in medicine.

[14]  Cornelis A T van den Berg,et al.  Specific absorption rate intersubject variability in 7T parallel transmit MRI of the head , 2013, Magnetic resonance in medicine.

[15]  Niels Kuster,et al.  The Virtual Family—development of surface-based anatomical models of two adults and two children for dosimetric simulations , 2010, Physics in medicine and biology.

[16]  Thoralf Niendorf,et al.  Design and Evaluation of a Hybrid Radiofrequency Applicator for Magnetic Resonance Imaging and RF Induced Hyperthermia: Electromagnetic Field Simulations up to 14.0 Tesla and Proof-of-Concept at 7.0 Tesla , 2013, PloS one.

[17]  Kamil Ugurbil,et al.  Imaging at ultrahigh magnetic fields: History, challenges, and solutions , 2017, NeuroImage.

[18]  Michael B. Smith,et al.  Calculations of B1 distribution, SNR, and SAR for a surface coil adjacent to an anatomically‐accurate human body model , 2001, Magnetic resonance in medicine.

[19]  Joseph V. Hajnal,et al.  Parallel transmission for ultrahigh‐field imaging , 2015, NMR in biomedicine.

[20]  R. W. Lau,et al.  The dielectric properties of biological tissues: II. Measurements in the frequency range 10 Hz to 20 GHz. , 1996, Physics in medicine and biology.

[21]  J. Lagendijk,et al.  7 T body MRI: B1 shimming with simultaneous SAR reduction , 2007, Physics in medicine and biology.

[22]  Daniel Sodickson,et al.  The Circular Dipole , 2013 .

[23]  J. Lagendijk,et al.  SAR and power implications of different RF shimming strategies in the pelvis for 7T MRI , 2009, Journal of magnetic resonance imaging : JMRI.

[24]  O. Dössel,et al.  Toward individualized SAR models and in vivo validation , 2011, Magnetic resonance in medicine.

[25]  R. Goebel,et al.  7T vs. 4T: RF power, homogeneity, and signal‐to‐noise comparison in head images , 2001, Magnetic resonance in medicine.

[26]  K. Uğurbil,et al.  Transmit and receive transmission line arrays for 7 Tesla parallel imaging , 2005, Magnetic resonance in medicine.