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Whereas conventional radiography produces summed images of an object, tomographic scanners rotate around the object being imaged, dividing the object and organizing it into spatially consecutive image slices.
The red line on the standard lateral radiograph of this foal's skull demarcates the location of the CT image pictured. Note how much more obvious the severity of this foal's facial trauma (maxillary fractures and hemorrhage in the nasal cavity) is on the CT versus radiographic image.
The major advantage of CT over conventional radiographs is improved spatial resolution. Veterinary patients are placed on the CT table while under anesthesia.
The CT table moves through the circular tunnel of the CT scanner (gantry) while an x-ray tube within the CT housing emits x-rays as it encircles the patient within the gantry. A detector array, on the opposite side of the x-ray tube, measures the x-rays that pass through the patient and computer-generated cross-sectional images are constructed from this data. Computed tomography is particularly useful for diagnosing abnormalities of the nasal passages, middle and inner ear, brain, abdomen, lung, mediastinum and the musculoskeletal system.
The computed tomography service at the Veterinary Medical Center includes a GE LightSpeed 8-multidetector helical CT scanner. CT studies are archived on a digital PACS system and optical disc. A specially constructed CT table, built by the Engineering Department at The Ohio State University, enables CT imaging of large animal patients weighing up to 2500 pounds.
A fracture of this horse's foot was further charactized using CT. Though the fracture was identified on radiographs, the small bone fragment associated with the fracture was not seen until the CT study was performed (arrow).
3D reconstructions of the horse's foot (below) further define the margins of the fracture.
The Ohio State University is a leader in the development of clinical applications for CT imaging in veterinary patients. Some of the past and on-going investigations are listed below:
- Diagnosis of ureteral ectopia in dogs
- Characterization of the normal urogenital tract in dogs
- Diagnosis of vestibulovaginal stenosis in dogs
- Characterization of benign and malignant splenic tumors in dogs
- Characterization of normal lung density values in cats and dogs
- Characterization of lung density values in dogs with inflammatory lung disease
- Characterization of normal thyroid size and density values in cats
- Characterization of normal thyroid size and density values in alpacas
- Characterization of normal pancreas size and density values in cats
- Characterization of adrenal gland size and density values in cats with interstitial cystitis
- CT arthrography for characterization of normal dog stifle joint soft tissue structures
- CT arthrography for identification of cruciate and meniscal ligament disruption in dog stifle joints
- Characterization of bone density differences in horse fetlock joints with and without arthritis
- Characterization of bone density differences in fractured and non-fractured Greyhound dog hock joints
- Characterization of the auditory tube in dogs
- Quantification of tibial torsion angles in dogs
- Accuracy of bone tumor dimensions in dogs
- Characterization of primary secretory otitis media in Cavalier King Charles spaniels
- Structural analysis of the caudal skull in Cavalier King Charles spaniels