Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Science

Program

Medical Biophysics

Supervisor

McIntyre, Christopher

Abstract

Cardiac sodium (Na+) MRI has the potential to unveil relationships between chronic kidney disease (CKD) and cardiovascular disease (CVD). Unfortunately, this modality requires many technical adaptations before it’s possible to extract and compare image data between individuals. This study investigated whether cardiac electrocardiogram (ECG) gating could improve image quality, and whether a uniform phantom could increase signal uniformity if a surface coil is used to acquire the image. Healthy participants were imaged with a custom-built surface coil and 3.0-T MR system. Cardiac gated images presented with a decreased signal-to-noise ratio (SNR), but intensity correction significantly increased image signal uniformity. Future studies using cardiac Na+MRI with a surface coil should consider implementing signal intensity correction but should recognize that cardiac gating reduces image quality unless scan time is increased.

Cardiac sodium (Na+) MRI has the potential to unveil relationships between chronic kidney disease (CKD) and cardiovascular disease (CVD). Unfortunately, this modality requires many technical adaptations before it’s possible to extract and compare image data between individuals. This study investigated whether cardiac electrocardiogram (ECG) gating could improve image quality, and whether a uniform phantom could increase signal uniformity if a surface coil is used to acquire the image. Healthy participants were imaged with a custom-built surface coil and 3.0-T MR system. Cardiac gated images presented with a decreased signal-to-noise ratio (SNR), but intensity correction significantly increased image signal uniformity. Future studies using cardiac Na+ MRI with a surface coil should consider implementing signal intensity correction but should recognize that cardiac gating reduces image quality unless scan time is increased.

Summary for Lay Audience

Introduction: Patients with damaged kidneys are also often found to suffer from heart conditions. Since damaged kidneys can’t adequately excrete excess sodium in the body, it would be beneficial to image sodium in the heart tissue of kidney disease patients and compare this to their heart function. This can be done using sodium MRI, but the low concentration of sodium in tissue is a challenging problem and imaging hardware and techniques must first be optimized. In this study, we set out to improve sodium MR image quality by removing the motion of the heart during imaging and correcting for the non-uniform image signal created by the custom-made imaging hardware.

Methods: We imaged the hearts of four healthy individuals with sodium MRI in each part of this study. In the first part of this study, each participant’s heart was imaged with and without heart motion. These images were then compared to assess image quality. In the second part of the study, a large bin with vials containing different concentrations of saline solution were imaged, along with large bin of uniform saline concentration. The image of the vials was divided by the image of the bin to correct for the signal intensity uniformity. Vial images before and after correction were compared to determine whether the intensity was corrected. This correction was then applied to each participant’s heart images as well.

Results: Removing heart motion during sodium imaging was not found to increase image quality but correcting the signal intensity uniformity of the images was found to be possible.

Conclusions: Technical adaptions must be implemented when imaging human hearts with sodium MRI. Removing heart motion is not necessary for quality images. However, signal intensity correction is necessary if quantitative measurements from image data are to be extracted and compared between participants. Dividing a heart sodium image by an image of a uniform saline solution can correct for the inherent signal intensity non-uniformity. Future studies may include using these technical adaptations to image the hearts of patients with kidney disease with sodium MRI to determine whether sodium build-up in heart tissue correlates with heart complications.

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