MR Essentials - Pulse Sequences - USA

Welcome to the MR Essentials - Pulse Sequences Online Training. This course will discuss how pulse sequences are used to make the MR scanner generate RF pulses and gradients to produce an image.   Upon successful completion of this course, you will be able to: Explain how a pulse sequence works Distinguish between the major types of pulse sequences Identify components of a pulse sequence diagram Congratulations. You have completed the MR Essentials - Pulses Sequence Online Training course. Listed below are the key learning objectives that have been presented. Take time to review the material in the downloadable document before you proceed to the final quiz. Explain how a pulse sequence works Identify components of a pulse sequence diagram Distinguish between the major types of pulse sequences Select the link below to view/print your review material before proceeding to the final quiz. Disclaimer: Please note that the learning material is for training purposes only! For the proper use of the software or hardware, please always use the Operator Manual issued by Siemens Healthineers. This material is to be used as training material only and shall by no means substitute the Operator Manual. Any material used in this training will not be updated on a regular basis and does not necessarily reflect the latest version of the software and hardware available at the time of the training. Please contact your local Siemens sales representative for the most current information. Functionalities described in the material or parts of this functionality may not yet be released for customers and not yet be commercially available in every country. Due to regulatory requirements, the future availability of said functionalities or parts thereof in any specific country is not guaranteed. The Operator Manual shall be used as your main reference, in particular for relevant safety information like warnings and cautions. The reproduction, transmission or distribution of this training or its contents is not permitted without express written authority. Offenders will be liable for damages. All rights, including rights created by patent grant or registration of a utility model or design, are reserved. Copyright © Siemens Healthcare GmbH, 2018 Four Main Classes of Sequences used for most clinical scanning include: Spin Echo Turbo Spin Echo Gradient Echo Echo Planar Timing Diagrams provide a visual means for distinguishing different types of sequences. RF pulses: Frequency Selective - narrow frequency bandwidth pulses represented by rolling shape Nonselective - wide frequency bandwidth pulses represented by box shape   Gradients: Fixed Amplitude - remain the same amplitude during the measurement, common with slice selection and readout gradients Variable Amplitude - gradient amplitudes will change during the measurement, common with phase-encoding gradients   Spin echo contains: 90o RF pulse 180o RF pulse Phase Encoding Gradient Single Echo Spoiler Gradients 90o 180o GS GF GP TE TR RF Spoiler Gradient Turbo Spin Echo has multiple refocusing RF pulses and multiple phase encoding tables. Higher Turbo Factors give faster scan time but fewer slices are available per TR Each echo has a different phase encoding amplitude Effective TE is used in acquiring the data contributing most to the tissue contrast Only have RF excitation pulse, no refocusing RF pulse Sources of spin dephasing from magnetic field inhomogeneities contribute to signal amplitude Allow variation of the flip angle of the excitation pulse Echo planar sequences acquire images in less than a second using a rapidly reversing read gradient. Unique characteristics include: RF pulse is only applied once per slice for the entire measurement Readout gradients alter in polarity Phase encoding gradient is turned on for a very short time at low amplitude (blip gradient) Total measurement time is 100 - 200 ms per image Images have lower spatial resolution and more noise. Main application is diffusion imaging for evaluating stroke patients. 3D or Volume Excitation Sequences Excite large tissue volumes High SNR Perform a double phase encoding approach to achieve thin slices Lots of possible gradient pair combinations