Phase Contrast Magnetic Resonance Imaging in the Rat Common Carotid Artery

Summary

The overall goal of this procedure is to measure the blood flow in the rat common carotid artery by using noninvasive phase contrast magnetic resonance imaging.

Abstract

Phase contrast magnetic resonance imaging (PC-MRI) is a noninvasive approach that can quantify flow-related parameters such as blood flow. Previous studies have shown that abnormal blood flow may be associated with systemic vascular risk. Thus, PC-MRI can facilitate the translation of data obtained from animal models of cardiovascular diseases to pertinent clinical investigations. In this report, we describe the procedure for measuring blood flow in the common carotid artery (CCA) of rats using cine-gated PC-MRI and discuss relevant analysis methods. This procedure can be performed in a live, anesthetized animal and does not require euthanasia after the procedure. The proposed scanning parameters yield repeatable measurements for blood flow, indicating excellent reproducibility of the results. The PC-MRI procedure described in this article can be used for pharmacological testing, pathophysiological assessment, and cerebral hemodynamics evaluation.

Introduction

Magnetic resonance imaging (MRI) is a versatile approach that provides detailed information on internal body structures and physiology, and is increasingly being used for clinical diagnosis and in preclinical animal studies. Animal models are vital for better understanding of considerable clinical implication ¹. As animal models considerably differ from humans with respect to anesthesia requirements and physiological parameters, optimization of MRI procedures for such animals assumes importance.

Phase contrast MRI (PC-MRI) is a specialized type of MRI that uses the velocity of flowing spins to quantify flow-related p....

Protocol

The Institutional Care and Use Committees (IACUC) of the China Medical University approved all procedures.

1. Animal Preparation and Monitoring

1. Leave all magnetically susceptible objects such as wallets, keys, credit card, etc. outside the scanner room prior to commencing animal preparation for MRI scanning.
2. Initially anesthetize the rat (2-month-old male Sprague-Dawley (SD) rat, 280–350 g) in an induction box using a mixture of 5% isoflurane (ISO) and oxygen (2 L/min) for 3–5 min, as necessary.
3. When the animal is recumbent and exhibits no response to a tail or toe pinch, discontinue ISO ....

Results

Correct slice geometry is pivotal for ensuring the success of the PC-MRI experiment. The accurate image plane positioning yields a "round" artery shape (Figure 3a), and as angulation increases, i.e., when it is less perpendicular to the artery, the resulting artery geometry becomes ovoid, leading to larger partial volume effects (Figure 3b). Severe partial volume effects would lead to the overestimation of blood flow 

Discussion

PC-MRI is a comprehensive approach for non-invasive and longitudinal evaluation of blood flow. We present a protocol for performing PC-MRI of the rat CCA. This procedure is easy to perform in any animal MRI scanner and demonstrates good reproducibility.

The PC-MRI technique has gained increasing popularity in human ^10,11 as well as animal studies ^4,12. Among these studies, resu.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
7T small animal MRI system	Bruker
Isoflurane	Baxter	1001936040	anesthetic
ECG lead	3M	2269T
Matlab	MathWorks		sofeware for image processing
Monitoring and gating system	SA instruments, Inc	Model 1030