Ultrasound is a diagnostic technique commonly used in veterinary practices to support radiography in small animals. Ultrasound is a non-invasive technique in which ultrasonic waves are directed into the tissue and the reflections they create of the deep structures of are represented as a visual image. Ultrasound is used to evaluate most soft tissues, the heart and the abdominal system in small animals. However, it can also be used in equine to show tears in tendons and ligaments. Ultrasound is usually performed on a conscious patient which is being manually restrained. However sometimes sedation is needed for a nervous patient to help them to relax, especially for an abdominal scan (Cooper, Mullineaux and Turner, 2011).

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Technical Detail

Before the ultrasound is carried out the patient must be clipped in order to allow contact between the probe and the skin. An ultrasound gel is also applied to the skin and probe to allow better contact (Lattimer, 2018). The patient is normally restrained in dorsal or lateral recumbency except when the heart is being scanned: in this case a special table is used with a hole in it which allows the patient to be scanned from beneath (Cooper, Mullineaux and Turner, 2011). The ultrasound machine consists of two main parts: the probe and processor. The probe generates sound waves and receives reflected sound waves. The processor takes the sound waves and turns them into an image (Lattimer, 2018). Ultrasonic waves are produced by electrically stimulating a piezoelectric crystal (transducer). When the beam hits a boundary between tissues of varying acoustic impedance some of the sound waves are reflected back to the transducer as echoes (Lattimer, 2018). The echoes are converted into electrical impulses that are displayed on a machine to produce the picture of the tissues under examination (Lattimer, 2018).

Special Equipment

Ultrasounds machine consists of two main parts: a probe and the processor. There are two main probes that are used for different investigations. The first is a linear array transducer which is mainly used for rectal examination in large animals as they need a long contact area (Lattimer, 2018). The second type of probe is the sector scanner transducer which is used in small animal investigation work as it only requires a small area of contact (Cooper, Mullineaux and Turner, 2011). Images on the ultrasound machine can be adapted by using the controls to change the depth, size, brightness and contrast. Images can be frozen to interpret an area and the image can be saved for later reference (Lattimer, 2018).

Clinical Applications

Ultrasound scans can be used to assist biopsies and fine needle aspiration; and heart motion and abdominal organ investigation. In biopsy and fine needle aspiration, the ultrasound scan helps to detect the area of the specific organ the needle is going to be injected into (Cooper, Mullineaux and Turner, 2011).

In my practice, ultrasound is most commonly used in large animals to identify and changes in tendons and ligaments. It is also used to help diagnose suspected pyometras and bladder stones.

Endoscopy

Principles

Endoscopy is used to visually examine internal organs and body parts without invasive exploratory surgery. An endoscope is an optical handheld device that travels in through the nasal cavity and transmits a high-quality magnified image. Endoscopy can help with the removal of a foreign body and samples of tissues can also be collected by means of endoscopy (Cooper, Mullineaux and Turner, 2011). When surgery is need, endoscopy is used to provide greater surgical precision and access in relation to more inaccessible areas of the body. Procedures are carried out through the natural orifices or an incision made by the veterinary surgeon. Surgery through endoscopy results in less tissue trauma, reduced intraoperative and post-operation pain, and quicker recovery and reduced infection rates. In practices it is becoming more common to carry routine operations, such as a bitch spays, in this way (Cooper, Mullineaux and Turner, 2011).

Technical Detail

There are two different endoscope cables that carry light from the end of the scope into the body lighting up the area being investigated. One or two cables carry light into the patient’s cavity while one carries the reflected light back to the eyepiece (Woodford, 2018b). The endoscope is either flexible or rigid. There are two types of flexible endoscopes: the fiberscope and videoendoscope, both of which are used for examining the gastrointestinal tract (Woodford, 2018a). A flexible endoscope machines comprise an umbilical cord which attaches to a light source and a suction pump, a hand piece and a long insertion tube which have a tip that bends in two or four directions. This type of endoscopy can be directed deep into the fluid or tissue to move foreign bodies, visualise lesions and take fluid or tissue samples. Rigid endoscopes are used to investigate body cavity and joint space (Woodford, 2018a). They comprise steel tubes containing rod lenses with an eye piece, and a connecter which allows for a light source to be attached. Rigid endoscopy is very delicate so extra care needs to be taken when using and cleaning (Clark, 2018).

Special Equipment

The flexible endoscope has channels inside that are designed to allow the user to place instruments down them. The instruments must fit the diameter and length of the endoscope. Biopsy forceps and grasping forceps are commonly used (Clark, 2018).

Clinical Applications

Endoscopy is used in the veterinary practice in different ways. One of the main uses of endoscopy is to look through the gastrointestinal tract, in order to identify foreign bodies and help remove them. Endoscopy is also used to collect samples from the bronchial or intestinal mucosa for cytology and culture (Woodford, 2018b). In my practice, endoscopy is used weekly on horses. Endoscopy is used prior to racing if the horse starts to cough or bleed from the nose while exercising. It is used to investigate their windpipe and larynx (Woodford, 2018b).

Magnetic Resonance Imaging (MRI)

Principles

Magnetic resonance imaging (MRI) is currently the most up-to-date method of diagnostic imaging and does not use ionising radiation: instead, it combines magnetism and radio waves. MRI is used to examine different parts of the body, especially the brain, spine, eye sockets, joints and soft tissue (Willows Veterinary Centre and Referral Service, 2018). The MRI scanner consists of a powerful magnet. There are two types of magnet that can be used: cylindrical (used in medium or high-field MRI) or open (used in low-field MRI). MRI causes the tissues within the magnetic field to become magnetised, which causes the protons of the hydrogen atoms in the area of the patient’s body being investigated to line up. Radio waves are then targeted at the area being investigated by an aerial, or RF coil. Transmissions last minutes at a time and cause the protons to emit tiny radio signals themselves. These are detected by the RF coil and turned to an image (Cooper, Mullineaux and Turner, 2011).

Technical Detail

During an MRI investigation, as the scan can take up to an hour or more, the patient is anaesthetised as they have to be completely still. They are placed on a table in the magnetic field with the area to be imaged in an RF coil. The RF coil come in different shapes and sizes depending on what area of the body they are designed for (Willows Veterinary Centre and Referral Service, 2018). Different types of scans can be performed using MRI to show tissues in different ways (Cooper, Mullineaux and Turner, 2011).

Specialised Equipment

MRI equipment consists of a large cylindrical case that contains a high-powered magnet. It is attached to a computer that analyses the radio signals received and turns them into images. The images are cross-sections of the are under investigation, which is useful as other structures that are in the way of the structure being investigated can be visually moved through or past in order to reveal the structure in question (Willows Veterinary Centre and Referral Service, 2018). Anaesthetic monitoring equipment cannot be used because of the presence of a strong magnetic field. However, when a low-field magnet is used, an anaesthetic machine can be used at distance. MRI produces extra heat so cool air has to be provided to the room (Willows Veterinary Centre and Referral Service, 2018). Patient temperature can decrease because of this, so blankets may need to be used to warm the patient up (University of Florida College of Veterinary Medicine, 2018).

Clinical Application

MRI is used to help diagnose different problems. They are commonly used in small animals to investigate brain and spinal conditions. MRI can also be used to investigate diseases such as neoplasia, soft tissue foreign bodies (VetSci, 2018). MRI is used in investigating the limbs of horses mainly to identify lameness causes. There is no MRI scanner in my practice although I have been involved with patients that have been referred to a specialist hospital with the correct equipment to carry out further MRI investigations.

References

Clark, J. C. (2018). Endoscopic equipment for the veterinary practitioner. [online] Available at: https://todaysveterinarypractice.com/endoscopic-equipment-for-the-veterinary-practitioner/ [Accessed 2 Oct. 2018].
Cooper, B., Mullineaux, E. and Turner, L. (2011). BSAVA textbook of veterinary nursing. Quedgeley: British Small Animal Veterinary Association, pp.496-506.
Lattimer, J. C. (2018). Ultrasonography – clinical pathology and procedures. [online] Available at: https://www.msdvetmanual.com/clinical-pathology-and-procedures/diagnostic-imaging/ultrasonography [Accessed 3 Oct. 2018].
University of Florida College of Veterinary Medicine (2018). Magnetic resonance imaging (MRI). [online] Available at: https://smallanimal.vethospital.ufl.edu/clinical-services/support-services/diagnostic-imaging/magnetic-resonance-imaging-mri/ [Accessed 1 Oct. 2018].
VetSci (2018). Clinical veterinary magnetic resonance imaging. [online] Available at: http://vetsci.co.uk/2011/11/08/clinical-veterinary-magnetic-resonance-imaging/# [Accessed 2 Oct. 2018].
Willows Veterinary Centre and Referral Service (2018). What is MRI scanning? [online] Available at: https://www.willows.uk.net/specialist-services/pet-health-information/diagnostic-imaging/what-is-mri-scanning [Accessed 2 Oct. 2018].
Woodford, C. (2018a). Care and handling of the flexible endoscope: anatomical structure. [online] Available at: https://www.educationaldimensions.com/eLearn/endoscope/anatomy.php [Accessed 3 Oct. 2018].
Woodford, C. (2018b). How endoscopes work. [online] Available at: https://www.explainthatstuff.com/endoscopes.html [Accessed 3 Oct. 2018].