Part 3a of a six part series covering the fundamentals of magnetic resonance imaging physics. In this section, Dr. Stafford expands on the concepts of gradients and echoes. Click here to view Part 3b or Part 1a.

Terms covered in Part 3:

• Pulse sequence diagram
• gradients
• echoes (echo)
• envelope function
• Gradient Recalled Echo (gradient echo) (GRE)
• spin echo

The effects of coronary artery diseases on the macrovasculature of the heart have been extensively studied, in contrast to the limited knowledge of effects seen in the microvasculature. As symtoms in the small vessels are an early warning sign of coronary artery disease, slowing or halting progression of these symptoms through improved diagnosis is the aim of the presented research. Dr. Robert deKemp is adapting PET imaging's stress over rest flow reserve, an established method in evaluating macrovasculature, to study the microvasculature. He presents his lab's translational micro-PET evalutaion of mice to determine effects of various stressors to eventually improve diagnostic procedures in humans and pre-clinically evaluate new therepeutic drugs.

Building on years of pioneering research, CAIN Investigator Dr. J. David Spence of the Stroke Prevention and Atherosclerosis Research Centre at Western University is refining the common understanding of atherosclerosis regression.  In a recent Letter to the Editor of Atherosclerosis, Dr. Spence critiques a work of Noyes and Thompson from the same journal, entitled A systematic review of the time course of atherosclerotic plaque regression, for both inaccurately determining plaque burden and therefore regression, and for approaching therapy intensity from an erroneous perspective. Spence’s previously published work in 2005 with fellow CAIN investigator Dr. Aaron Fenster of the Imaging Research Laboratories at Robarts Research Institute and Western University, underscores the rationale behind the correction, reiterating that “measurement of carotid plaque burden by ultrasound is much superior to IMT for assessing effects of therapy.”  His letter can be viewed here, and the original article here.

The partnership of Spence and Fenster et al. has also been employed towards better prognosis and risk stratification of atherosclerotic patients.  The tool, an ultrasound system capable of producing 3D images of the carotid artery and any associated plaque, has proven superior to the standard of care when evaluated in a cohort of patients in London, Ontario, providing a unique instrument for the measurement and characterization of these carotid plaques. The 3D ultrasound system provides a reliable method of evaluating total ulcer volume of atherosclerosis patients, which is a good and difficult to obtain prognostic indicator, as well as plaque texture change and total plaque volumes which are also important risk factors. This collaboration is effective; contributing to the global understanding atherosclerosis, the leading cause of illness and death in Canada.

Related training videos: 

Part 2b of a six part series covering the fundamentals of magnetic resonance imaging physics. In this section, Dr. Stafford introduces concepts of relaxation and image contrast. Click here to view Part 2a or Part 1a.

Terms covered in Part 2:

• Image voxel
• Nutation
• Thermodynamic equilibrium magnetization
• Proton density
• Dephasing/Regrowth/Recovery/Decay/Relaxation
• Bloch equation
• T2 relaxation curve/ transverse dephasing curve
• T1 vs T2
• MR signal
• Echo (TE)
• Repetition Time (TR)
• Inversion Recovery Imaging (IR)
• Inversion time
• MP-RAGE
• Proton-weighted images