CT protocols will vary per region you are attempting to image, patient positioning, slice thickness, algorithms, and whether or not contrast will be used. Each of these factors is critical, but the most commonly overlooked factor is patient positioning. Ensure the region of the patient you are imaging is straight and symmetrically positioned on midline of the CT table, as subtle changes in obliquity may make structures appear abnormal when they are not. Use positional aids, sponges, or troughs if needed, and ensure that all metallic or other unnecessary objects are removed. Place the patient either head-first or hindlimb-first into the gantry, depending on which will be closest to the region for imaging. The following are recommended protocols for different body regions based on common problems seen in MWDs.
Patient positioning should be in ventral recumbency, with the hard palate parallel to the CT table. Studies should extend from the tip of the nose to the 2nd to 3rd cervical vertebra. Bone, standard, and bone algorithms with slice thicknesses of 2.5 mm, 1.25 mm, and 0.625 (if available) should be performed, respectively. Sagittal and dorsal reconstructions should be made as needed.
Patient positioning should be in ventral recumbency, with the hard palate parallel to the CT table. Studies should extend from the tip of the nose to the larynx. A bone algorithm with slice thicknesses of 2.5 mm and 0.625 mm (or equivalent) and a standard algorithm with slice thickness of 1.25 mm should be performed. Intravenous contrast should be administered, and the standard algorithm with 1.25 mm thick slices repeated. Dorsal reconstructions are required. Sagittal reconstructions should be made as needed.
Patient positioning should be in ventral recumbency, with the hard palate parallel to the CT table. Studies
should extend from mid-muzzle to the 2nd to 3rd cervical vertebra. Bone, standard, and brain algorithms with slice thicknesses of 2.5 mm, 1.25 mm, and 1.25 mm should be performed, respectively. IV contrast should be administered and brain and standard algorithms repeated. Sagittal and dorsal reconstructions of the standard algorithms are required.
Patient positioning should be in ventral recumbency, with the hard palate parallel to the CT table. Studies should extend from the orbits to the 2nd or 3rd cervical vertebra. Bone and standard algorithms with slice thicknesses of 0.625 - 1.25 mm and 1.25 mm should be performed, respectively. Sagittal and dorsal reconstructions should be made as needed.
Patient should be positioned in dorsal recumbency, with the hind limbs maximally extended caudally (like for a hip-extended VD pelvic view in radiography). Study should extend through necessary vertebral regions based on pain and/or neurolocalization. More specifically for the hind limbs, if UMN signs are present, extend from T8-T9 through sacrum, and if LMN signs present, from T12-T13 through sacrum. CT slices should be acquired perpendicular to vertebral canal (may require gantry rotation). A bone algorithm with 2.5 mm and 1.25 mm slice thicknesses and a standard algorithm with 1.25 mm slice thickness should be performed. For suspect lumbosacral disease, the bone algorithm of 1.25 mm slice thickness should be replaced with 0.625 mm (or equivalent) slice thickness to better visualize the neuroforamina at the lumbosacral junction. Sagittal and dorsal reconstructions of bone and standard algorithms are required.
Anesthesia and breath holds are required. Patient should be positioned in ventral recumbency. Study should extend from thoracic inlet through caudal aspect of liver (ensure extent of all lungs imaged). Bone, standard, and lung algorithms should be performed with slice thicknesses at 5.0 mm, 2.5 mm, and 1.25-2.5 mm, respectively. Sagittal and dorsal reconstructions of lung and standard algorithms are required.
Anesthesia and breath holds are required. Patient should be positioned in dorsal recumbency. Study should extend from caudal margin of cardiac silhouette through pelvic canal (or prostate if male). Bone and standard algorithms should be performed with slice thicknesses at 5.0 mm and 2.5 mm, respectively. Sagittal and dorsal reconstructions of bone and standard algorithms are required.
Patient positioning depends on whether imaging forelimbs or hindlimbs. For forelimbs, the patient is in ventral recumbency. The forelimbs should be extended cranially, resting the forearms and paws on the table with the elbows and shoulders bent at a normal resting position. If the hindlimbs are the focus of the study, the patient is usually placed in dorsal recumbency. The hindlimbs should be placed in maximal caudal extension, keeping both limbs symmetric and including both in the study for comparison purposes (use tape, sponges, or other positional aids). CT slices should be acquired perpendicular to joint spaces, which may require gantry rotation if the joint is the focus of the study. Bone and standard algorithms should be performed along the affected region with slice thicknesses of 1.25 mm. If a joint the focus of the study, conducting an additional bone algorithm sequence with a slice thickness of 0.625 mm is required (if available). Sagittal and dorsal reconstructions of the affected limb only are required.