MR Physics for Clinicians: Fast Imaging Techniques
ORGANIZERS: Anthony Christodoulou, Peng Hu, Mariya Doneva
Tuesday, 18 May 2021
||14:30 - 15:00
||Moderators: Vera Keil & Taylor Chung
Skill Level: Basic to Intermediate
Session Number: WD-09
Parent Session: MR Physics for Clinicians: Fast Imaging Techniques
Session Number: WD-09
This course will be a basic and comprehensive review of fast MRI physics and image reconstruction. The presentations will be non-mathematical and suitable for clinicians (or physicists new to the field). The course will cover three complementary approaches to accelerated MRI: fast pulse sequences, parallel imaging, and sparse reconstruction.
This course is primarily designed for the clinician who will benefit from an understanding of the "hows" and "whys" of fast MR imaging. While it requires no prior experience with MR, those with some familiarity and experience will also benefit. Those interested may include: radiologists and clinicians relatively new to MR imaging (including residents and fellows), experienced radiologists and clinicians wanting a refresher course in MR physics and image reconstruction, and physicists and engineers wanting an introduction to the field.
As a result of attending this course, participants should be able to:
- Explain how fast pulse sequences (e.g., gradient echo, EPI, spiral, non-Cartesian acquisition) physically acquire data more quickly;
- Explain how parallel imaging methods (e.g., SENSE, GRAPPA) model or exploit the different sensitivity patterns of multichannel receiver coils to require less data; and
- Explain how image reconstruction methods (e.g., partial Fourier imaging, compressed sensing, low-rank imaging) model the underlying images to require less data.
||Fast Pulse Sequences: Acquiring Data More Quickly
This talk will cover the physical principles of acquiring data rapidly and introduce commonly-used fast pulse sequences. Gradient-recalled echo and balanced SSFP pulse sequences reduce scan time by reducing the repetition time. Spin-echo-train pulse sequences reduce scan time by acquiring a series of k-space lines interspersed between refocusing pulses. A third way to reduce scan time is to collect more than a single line of k-space during a single readout, as in echo-planar imaging and spiral scanning. The audience will learn the fundamentals and applications of these fast pulse sequences.
||Parallel Imaging: Modelling the System to Acquire Less Data
The objective of this presentation is to provide an overview of parallel MR imaging methods and their applications in clinical practice. We will start with discussing image formation for reduced data acquisition and ways to compensate for the missing data with parallel MRI techniques. We will discuss the limitations of parallel MRI such as noise amplification and sensitivity to calibration and their effect on achievable acceleration and image artifacts. We will finish with review of some clinical applications that can benefit from the use of parallel imaging.
||Sparse Reconstruction: Modelling the Image to Acquire Less Data
Sparsity is ubiquitous in medical images and can be exploited to scan faster. In this presentation, the concept of sparsity and the related concept of compressibility are reviewed. This is followed by an overview of how these concepts can be leveraged to scan faster, and conditions under which imaging speed can be pushed further.