Share this
The Handbook of Small Animal MRI was written by Ian Elliott and Geoff Skerritt and published by Wiley-Blackwell in 2010. Both authors live in the United Kingdom and have extensive experience with MRI techniques in veterinary patients, Elliott as a radiographer and Skerritt as a veterinary neurologist. MRI, or magnetic resonance imaging, is gaining more acceptance and usage in the veterinary field as MRI scanners become more affordable and available with the advent of mobile veterinary MRI machines. This handbook was designed to introduce the basic concepts of MRI scanning and how one would employ its use in the veterinary field.
The handbook is divided into two sections, “Part One: Physical Principles of MRI” and “Part Two: MRI in Veterinary Medicine.” Chapters in Part One include basic principles, MR system hardware, imaging parameters, and image artifacts. The MRI technician has the ability to alter or manipulate image contrast through signal intensity so it is important the fundamental theory behind MRI be understood before attempting analysis of images. “Chapter One: Basic Principles” gives the reader a brief overview of radiation physics. The hydrogen proton is generally used in the MR system as it is plentiful in the body, is able to generate a large magnetic moment, and resonates well. Resonance is created using radio frequency energy in pulses, and the effects of an external magnetic field (Bo) on the patient’s hydrogen protons are discussed. The main equipment necessary for the MR system, the magnet being a central component, is reviewed in Chapter Two. The system is dependent upon magnetism and radio frequency interaction.
“Part Two: MRI in Veterinary Practice” begins with an overview of the safety features and aspects to be considered when employing an MRI scanner. The Medical Devices Agency noted hazards from the static magnetic field, the magnetic field gradients, and the radio frequency magnetic fields. The MRI scanning itself causes no adverse reactions in the patient’s body in magnetic fields less than 2.5 Tesla, however loose metallic objects and previous surgical implants are of consideration for the patient and staff. Typically the permanent or super conducting magnets in an MRI system cannot be turned off without costly repercussions, so the magnetic fields generated are of concern for anyone with medical implants such as cardiac pacemakers or stents in the “controlled area,” often the scanning room.
The remainder of the text is devoted to the actual usage of MRI in clinical veterinary situations and an atlas of normal anatomy as seen on MR imagery. Once the basic patient anesthesia, positioning, clinical indications, and specific contrast agents are reviewed, the main body systems in which MRI excels are discussed along with photo images of the actual image slices. Many of the irregular or suspect areas are, however, not labeled clearly other than a general description of the lesion. Several photos do use arrows as guidelines for the reader, however, many do not. For the novice MRI observer, this creates a challenge, having to flip between the normal atlas following the chapter, and the abnormal image preceding the atlas.
The Handbook of Small Animal MRI is a good start to the basic understanding of MRI for the unaccustomed veterinarian. General indications for MRI usage and how the images are generated are clearly demonstrated with clear and well thought out diagrams. A well-labeled atlas of normal anatomy as seen by MRI is included for reference as well as a glossary of terminology.
Sandra L. Jex is a veterinarian and consultant.