Today's Veterinary Practice

MAY-JUN 2014

Today's Veterinary Practice provides comprehensive information to keep every small animal practitioner up to date on companion animal medicine and surgery as well as practice building and management.

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May/June 2014 Today's Veterinary Practice 55 ImagIng EssEnTIals | RaDIogRaPhy of ThE small anImal skull: TEmPoRomanDIbulaR JoInTs & TymPanIC bullaE tvpjournal.com tor, as needed. To ensure the patient is properly positioned, place your hands: • On either side of the skull, feeling for the symmetry of the mandible and/or zygomatic arches. • Relative to either anatomic location to be equidistant from the table on the right and left sides. Collimation 1. Set the central beam to the level of the caudal zygomatic arch (at a level just caudal to the eyes) with the collimator opened to include C1/C2, the neurocranium, and the caudal portion of the nasal cavi- ty (approximate level of maxillary premolar 3). 2. Place the radiopaque marker on the right side of the dog or cat, tak- ing care to avoid superimposition of the marker over any part of the skull. Ensuring Image Quality For VD or DV images of the skull, the rostral extent of the image should be the nasal planum, while the caudal extent is C1. Make sure the various parts of the skull are symmetrically positioned right and left, and not obliqued. This may be impossible in patients that have skull trauma with multiple fractures. bREED-bASED POSITIONING although positioning for many of these projections is similar, use of sponges and tape will vary based on skull size and shape: • Dolichocephalic breeds (eg, Doberman pinscher) have long, narrower heads • Mesaticephalic breeds (eg, beagle) have medium sized and shaped heads • brachycephalic breeds (eg, bulldog) have short, wide heads, with foreshortening of the nasal cavity and absence of frontal sinuses • Cats have more standard sized and shaped heads; however, some brachycephalic cat breeds (eg, Persian) require the same considerations as brachycephalic dog breeds. Figure 3. Dog positioned for an open-mouth rostrocaudal oblique radio- graph of the TMJ and tym- panic bullae (A) and corre- sponding radio- graph (B). A b sPecific PRojections: tMj & tyMPanic Bullae OPEN-MOUTH ROSTROCAUDAL ObLIQUE PROJECTION (Figure 3) Positioning 1. Place the patient in dorsal recumbency. 2. Flex the neck, positioning the hard palate and mandibles perpendicu- lar to the table and x-ray collimator system. 3. Place small triangle sponges under the external occipital protuber- ance to help maintain a symmetric position on the table. 4. Place tape—starting from one side of the table at the level of the ab- domen—and pass it around the patient's nose, fastening it to the other side of the table at the same level. 5. Angle the hard palate approximately 10 degrees rostral to the perpen- dicular plane of the body. 6. Extend the mandible caudally (open mouth) with the endotracheal tube secured to the mandible, taking care to avoid kinking the tube and stopping the flow of oxygen/inhalation of anesthetic agent. Collimation 1. Set the central beam through the open mouth at the level of the soft palate. 2. Take care to ensure the cranium is straight, without lateral rotation. 3. Assess this positioning by standing at the patient's head and placing your hands on either side of the cranium, at the level of mandibular rami, verifying both rami are equidistant to the table. Ensuring Image Quality The open-mouth projection should include both TMJ and tympanic bullae without rotation or superimposition of the endotracheal tube. Collimation should extend caudally from C1 to include the full tympanic bullae rostrally. 2014-0506_IE_Skull2.indd 55 5/23/2014 12:59:38 PM

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