Diagnostic Imaging
The staff of boarded veterinary radiologists, technologists and technicians of the Diagnostic Imaging Service at the University of Florida’s Veterinary Medical Center (VMC) is dedicated to patient care. Utilizing modalities such as computed radiography, fluoroscopy, ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI), our service uses state-of-the-art imaging equipment to assist clinicians in diagnosis and treatment of our VMC patients.
Magnetic Resonance Imaging (MRI)
The University of Florida Diagnostic Imaging service is proud to introduce the newest modality that is now available on-site, a magnetic resonance imaging unit (MRI). Providing a greater level of imaging capability to the hospital and to referring practices, the Toshiba Vantage 1.5 Tesla high-field magnet uses a strong magnetic field and the natural resonance of atoms in the body to visualize the structure and function of organs. MRI, primarily used to examine the internal organs for abnormalities, is noninvasive and is superior to other modalities for imaging soft tissues. The principles of MRI imaging are very complex.
The patient is placed in the strong magnetic field, and the hydrogen protons in the body are then manipulated as specific radiofrequencies (RF) are transmitted into the patient. This essentially turns these hydrogen atoms into small, moving magnets within the body. Because the hydrogen atoms respond in a predictable fashion based on their chemical bonds, the movement, or relaxation, of the protons can be used to generate an image. Based on the principles of Faraday’s Law, these tiny moving magnets can generate an electrical current, or signal, in a coil that is placed around the patient. These signals are collected, processed through a computer and converted into images of the patient. Both large and small animals are imaged using MRI. Imaging of large animal patients, due to size constraints, is limited to the limbs and head. As with CT, patients receiving an MRI exam require general anesthesia.
Computed Tomography (Catscan or CT)
Computed Tomography or CT is another important part of our diagnostic imaging arsenal. The VMC is fortunate in having a Aquilion Toshiba 8 slice multidetector-row CT scanner with the capability of scanning small animal and, with the recent acquisition of a specially designed table, large animal patients. Do to their size, our large animal patient studies are limited to the skull and lower extremities. Utilizing x-rays, a CT scan provides a cross-sectional image of all tissue types of the body region scanned. These images are obtained by making thin slices through the patient, similar to slicing a loaf of bread. This form of imaging, tomography, provides the radiologist much more information about the patient than conventional radiography and eliminates the superimposition of structures that is often so challenging when interpreting radiographic studies. CT is frequently used for imaging many disease processes such as cancer, fractures, lung disease, and vascular anomalies. CT also provides invaluable information for surgical and radiation treatment planning. Unlike radiography and ultrasound, tomographic imaging requires the patient to be anesthetized or heavily sedated for the examination.
Nuclear Scintigraphy
Nuclear Scintigraphy uses a gamma camera that detects gamma rays during the decay of a radionuclide. These radionuclides can be linked to a physiologically active agent and injected into the patient’s body, allowing different physiologic processes to be imaged with this modality. Examples include glomerular filtration rate using 99mTc-DTPA, bone modeling using 99mTc-HDP, or radiolabeled white blood cells to detect infection. While the most common application is bone scintigraphy to detect changes in bone metabolism that may be related to lameness, nuclear scintigraphy can also be used to detect portosystemic shunts, subclinical renal failure, hyperthyroidism and to evaluate mucociliary clearance, just to name a few.
Ultrasonography
Ultrasound (US) is non-invasive diagnostic tool that is used to assess disease processes within the patient. Sound waves emitted from a transducer travel through organs and tissues. As these sound waves travel through the patient, some are reflected or absorbed. The waves reflected back to the transducer produce a signal, called an echo. These echoes are detected and analyzed by a computer in the ultrasound machine to produce an image of the organ scanned. The images are captured in real time. Through additional techniques, blood flow through vessels, organs, and diseased tissues can be evaluated. Ultrasound also provides targeted sampling of small amounts of body cavity fluid, and obtaining fine-needle aspirates and biopsies or abnormal organs and tissues.
Radiography and US are complementary imaging modalities. While radiography provides limited information about the internal architecture of abdominal organs, it provides invaluable information about the entire abdominal cavity, including bones and areas such as the pelvic canal that cannot be adequately evaluated with US. It is important that these imaging modalities are used in conjunction with one another to provide the best possible diagnostic accuracy and patient care.
Computed Radiography
In 2004 the service made a landmark upgrade from traditional radiography, utilizing film and chemical processing, to computed radiography (CR). Using the same X-ray equipment already in place, CR uses a cassette system with an imaging plate that contains photostimulable (light stimulated) storage phosphors. These phosphors detect and store energy from the x-rays that strike the cassette. Instead of chemically processing the cassette is run through a computer scanner that utilizes a scanning laser to release the energy from the plate in the form of light. The light is captured, recorded, and processed into an image by a computer. The imaging plate is then erased by fluorescent light in the scanner, and is then ready to be used again. This allows the imaging plate to be used thousands of times. The digitized image can then be enhanced and viewed by using computer software that enables the interpreter to manipulate the radiograph’s contrast and brightness. The viewer can also zoom, pan and make measurements. Additionally, the images are created and stored using specific criteria for medical images (DICOM), which provides a secure file that is very difficult to alter. Fluoroscopy uses similar equipment to radiography; however, instead of making one image at a single moment in time, the patient can be examined in real-time. Fluoroscopy allows patients to be evaluated for dynamic tracheal disease, as well as cardiac and vascular diseases using angiographic techniques.