A brief survey of the permanent magnet design techniques that are made possible by the availability of modern magnetic materials is followed by experimental results and some consideration of their practical applicability to the realization of MRI magnets.
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Quality requirements for MRI simulation in cranial stereotactic radiotherapy: a guideline from the German Taskforce "Imaging in Stereotactic Radiotherapy".
Strahlenther Onkol
January 2024
Klinik und Poliklinik für Strahlentherapie und Radioonkologie, Universitätsklinikum Würzburg, Würzburg, Germany.
Accurate Magnetic Resonance Imaging (MRI) simulation is fundamental for high-precision stereotactic radiosurgery and fractionated stereotactic radiotherapy, collectively referred to as stereotactic radiotherapy (SRT), to deliver doses of high biological effectiveness to well-defined cranial targets. Multiple MRI hardware related factors as well as scanner configuration and sequence protocol parameters can affect the imaging accuracy and need to be optimized for the special purpose of radiotherapy treatment planning. MRI simulation for SRT is possible for different organizational environments including patient referral for imaging as well as dedicated MRI simulation in the radiotherapy department but require radiotherapy-optimized MRI protocols and defined quality standards to ensure geometrically accurate images that form an impeccable foundation for treatment planning.
View Article and Find Full Text PDFPrepolarized MRI of hard tissues and solid-state matter.
NMR Biomed
August 2022
MRILab, Institute for Molecular Imaging and Instrumentation (i3M), Spanish National Research Council (CSIC) and Universitat Politècnica de València (UPV), Valencia, Spain.
Prepolarized MRI (PMRI) is a long-established technique conceived to counteract the loss in signal-to-noise ratio (SNR) inherent to low-field MRI systems. When it comes to hard biological tissues and solid-state matter, PMRI is severely restricted by their ultra-short characteristic relaxation times. Here we demonstrate that efficient hard-tissue prepolarization is within reach with a special-purpose 0.
View Article and Find Full Text PDFSimultaneous imaging of hard and soft biological tissues in a low-field dental MRI scanner.
Sci Rep
December 2020
MRILab, Institute for Molecular Imaging and Instrumentation (i3M), Spanish National Research Council (CSIC) and Universitat Politècnica de València (UPV), 46022, Valencia, Spain.
Magnetic Resonance Imaging (MRI) of hard biological tissues is challenging due to the fleeting lifetime and low strength of their response to resonant stimuli, especially at low magnetic fields. Consequently, the impact of MRI on some medical applications, such as dentistry, continues to be limited. Here, we present three-dimensional reconstructions of ex-vivo human teeth, as well as a rabbit head and part of a cow femur, all obtained at a field strength of 260 mT.
View Article and Find Full Text PDFOptimization of Simultaneous Multislice, Readout-Segmented Echo Planar Imaging for Accelerated Diffusion-Weighted Imaging of the Head and Neck: A Preliminary Study.
Acad Radiol
November 2020
Department of Radiology, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, No.1 Shuaifuyuan, Dongcheng District, Beijing, China. Electronic address:
Rationale And Objectives: To evaluate the feasibility of simultaneous multislice (SMS)-accelerated, readout-segmented echo-planar imaging (rs-EPI, RESOLVE) with the use of special-purpose coils for head and neck assessment, particularly in patients diagnosed with head and neck malignant tumors, through comparison with the conventional RESOLVE and RESOLVE with readout partial-Fourier technique (RESOLVE-RPF).
Materials And Methods: Twenty-five healthy volunteers and 24 patients with histologically proven malignant head and neck tumors were included in this prospective study. The MR exam included conventional RESOLVE, RESOLVE-RPF, prototypic SMS-RESOLVE, and prototypic SMS-RESOLVE with special-purpose coils (SMS-RESOLVE + Coils), acquired at b-values of both 0 and 800 s/mm.
Relative Magnetic Force Measures and Their Potential Role in MRI Safety Practice.
J Magn Reson Imaging
April 2020
Department of Radiology, Brigham and Women's Hospital, Boston, Massachusetts, USA.
Background: Magnetic field markings are occasionally used at MRI sites to provide visual feedback of magnetic field strength at locations within the MRI scan room for safety purposes. In addition to magnetic field line markings, relative magnetic force, or ratio of magnetic to gravitational forces on an object, may be considered a useful complementary metric to quantify the risk associated with bringing objects containing ferromagnetic material into the magnetic field.
Purpose: To develop and validate methods for deriving useful relative magnetic-force measures including a simple force index for application to MRI safety.
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