Magnetic Resonance Imaging (MRI) Questions and Answers 2023

Magnetic Resonance Imaging (MRI) Questions and Answers 2023 True or false, Quenching is dangerous and prohibitively expensive True how is Data localization in MRI accomplished a gradient magnetic field is superimposed on a static external magnetic field. what is the primary variable in the data collection procedure during MRI the sequence True or false, Two electromagnetic coils are required to produce magnetic field gradients corresponding to the axis to be imaged False determines the section thickness, resolution and plane of the image in MRI Gradients coils Repetition time (TR) the interval between pulse sequences The frequency of a given type element is called the Larmor Frequency the longer the wave is applied to the patient, the greater the angle of precession The higher the proton density the higher the MRI signal True or false, a 380 degree pulse is most effective in MRI False, 90 degrees or 180 degrees pulse are more effective in MRI Higher strength magnetic field stronger RF signal CSF will appear as dark signal on T1 weighted images CSF will appear as bright signal on T2 wieghted images true or false, A free magnet will move to align itself in a magnetic field true, this is called a magnetic moment nuclei used in MRI are found in abundance in the human body, (Hydogen) have and odd number of protons and neutrons, and affect external magnetic field. Part of the scanning procedure controlled by the MRI operator RF pulse sequencing, , and it is user dependent type of bone that MR does not image as clearly as seen in CT Cortical bone Higher magnetic strengths produce stronger RF signals and higher resolution images what special problem in MRI is caused by the extremely long scan times that must be used Motion Contraindications to the contrast media most commonly used for MRI procedures Renal failure and pregnancy What type of magnet produces a strong field up to 4T Superconductive MR images are viewed in a Monitor a unit of magnetic field strength Telsa The protons of this element gives rise to the signal used in clinical MR imaging Hydrogen The ability to differentiate adjacent tissues contrast A measurement of smallest object that we can visualize in the image pixel The tiny MR signal which results from applying the radio waves to the patient echo The MR system component that makes the "knocking" noise during an exam. gradient Energy used in MR imaging Radio frequency An extremely cold liquid used in a superconducting magnet cryogen The grid of rows and columns of pixels which make the digital image matrix a plane which is perpendicular to the axis which runs from head to foot in the patient Transverse This property is exhibited by a spinning proton magnetism a type of image which can be stored on a computer and viewed on a monitor Digital This type of radiation is not used in MRI ionizing The digital processor used at the heart of an MR system computers (arrays) the "R" in MRI Resonance Lying face up Supine an MR image, representing a slice through the patient is called section the sub-atomic particular which gives the MR signal proton The loop of wire used to measure the MR signal coil The smallest unit of matter that still behaves like a particular substance atom TE, or time to echo Time period between the excitation and sampling of induced signal T1 weighted image demonstrates anatomy T2 weighted image demonstrates pathology resistive magnets high electrical current , Ideal for severe claustrophobia Resistive Magnets Advantages: Good uniform field, Can be turned off, Good for implants, orthopedic imaging, Inexpensive Resistive Magnets disadvantages: Low magnetic field strength, Longer imaging time, High electrical bill Permanent Magnets (no used today) vertical magnetic field, and temperature sensitive, unable to turn off Permanent Magnets advantages Easy to site, Good for implants, and orthopedic imaging, Inexpensive Permanent Magnets Disadvantages: Low magnetic field strength, Longer imaging time, Unable to turn off, Temperature sensitive Superconducting Magnets Electromagnet, Property of superconductivity,  Cryogens used to reduce resistance, Up to 3.0 Tesla Superconductive Magnets adventages High magnetic field strength, Shorter imaging time Superconductive Magnets Disadvantages: Expensive, Cannot be turned off (safety concerns) ramping bringing magnet to proper temperature Quenching abnormal termination of magnet operation, cryogens cools the magnet coils boil off rapidly FONAR Upright MRI Scanner, used for back and extremity imaging) World's Most Powerful MRI scanner 9.4 Tesla (T) at the University of Illinois at Chicago Gradient Coils Resistive electromagnets that create magnetic fields that vary in intensity, Located in the bore of the magnet RF Coils Attachment coils that surround the part that is being imaged, Serve as transmitter and/or receiver of MRI signal Shim Coils Corrective magnetic coils, Located in the bore of the magnet, Means of magnetic field homogeneity Spin echo (SE) (FSE) Most common pulse sequence Gradient recalled echo (GRE) rapid acquisition imaging Inversion recovery longest pulse sequence Gadolinium DTPA Paramagnetic agent, Shortens T1 relaxation times, appears bright, Used in neurology imaging, MRA Safety Areas Zone 1: outside of scanner environment, Zone 2 : greeting area, MRI technologist supervises area, Zone 3: control area, Access controlled and limited by MRI technologist, Zone 4 : Room housing scanner, MRI technologist must supervise everyone entering room