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• These notes are for RAD 212 and cover positioning terminology, patient preparation, positioning devices, and grids.
• The overall goals are to create quality radiographs with veterinary significance, use positioning terminology/aids, know common radiographic positions, understand patient positioning and restraint, know how to create radiographs of cats and dogs, maintain record keeping and storage, and be able to evaluate radiograph quality.
• General objectives are to transfer skills, reduce retakes, minimize stress to animals, and maximize safety.

Terminology

• It's essential to know the normal anatomy and proper terminology for each species.
• Positioning terminology and aids are important.
• Radiographic views depend on common views and patient restraint.
• Should know terminology for radiography of cats and dogs.
• Need to review terms to obtain radiographs for efficiency, patient care, and safety

Directional Terminology

• Derived from the American College of Veterinary Radiology (ACVR).
• Based on the orientation of the primary beam.
• Cranial and caudal refer to the limb proximal to the carpus/tarsus.
• Palmar = forelimbs, plantar = hind limbs.
• Oblique is added when the central beam passes through the patient at an angle.
• In combinations of terms, rostral, cranial, and caudal precede other descriptors, e.g., caudoventral for the head, neck, trunk, & tail .
• Remember etymological rules when combining two terms.
• Common terms include Dorsal (D), Ventral (V), Cranial (Cr), Rostral (R), Caudal (Cd), Medial (M), Lateral (L), Palmar (Pa, P), Plantar (Pl, P), Proximal (Pr),and Distal (Di).

Patient Preparation

• Several factors must be considered to create a quality radiograph including welfare of patient, restraint and immobilization, the location and minimizing trauma during exam.
• Minimize risk of exposure to technician and other personnel.
• Comfort and welfare of the patient are primary concerns.
• Patience is vital, especially with injured or painful animals, or animals that can't be sedated.
• Animals do not understand the X-ray is painless.
• Use handling skills to keep calm, quiet, and deliberate motions.
• To minimize anxiety, use a soft voice and gentle stroking.
• Avoid quick movements and severe restraint.
• Prep the patient before positioning if possible.
• Patient prep includes measuring the patient, setting the machine, positioning imaging plate, and inputting information into the system.
• Document exposures, ensure staff have appropriate PPE then position and expose.
• Use of nonmanual restraint is important and simple tools can complete exposures without radiation exposure.
• Patient welfare should be kept in mind at all times.
• Use calipers and never guess when measuring.
• Affected area down, based on effects of distortion, SID, and anatomy.
• Remove items like collars, leashes, IV tubes, and other body parts from the area of interest.
• Consider effects caused by hair coat or metallic objects.
• Remove bandages, splints and casts to avoid shadows if they’re not part of the study

Required Views

• Minimum of two views are necessary for diagnostic purposes, but views are usually at right angles to one another.
• Center the primary beam directly over area of interest.
• If there's a known lesion (break), center the beam over it.
• Ensure all relevant anatomy fits in the view.
• Place the thickest part at cathode end if possible due to the heel effect.
• Guidelines include placing the area of interest closest to the receptor, to reduce distortion and magnification.
• When doing limbs, take images of the other leg to compare is useful
• Use a nonslip pad under the plate with tabletop views.
• Ensure settings are correct
• Check the plate/cassette/machine/grid is in position and that markers are in the correct location
• Coliminate properly
• Ensure the patient (body part) parallel to receptor and perpendicular to the beam.
• Confirm correct phase of respiration.
• Proximal part of the limb points up and with cranial/dorsal pointing left for lateral/oblique limbs views
• The proximal end of the extremity at top of viewer for DP/PD/CrCd/CdCr views.
• Lead markers should be present and the radiograph must be labelled correctly, properly centered, with appropriate contrast and density, and with no artifacts.

Types of Restraint

• Manual restraint is the least desireable and should be the last report unless necessary.
• One should always wear PPE, and be 6 feet from the source, or behind a lead wall.
• Mechanical restraint includes physical means of holding the animal or convincing the animal that it is being held.
• Commercial products for mechanical restraint: sandbags, foam wedges, positioning troughs, Velcro, compression bands, ropes, wood blocks, and straps.
• Be create when devising positioning aids - use IV fluids , tape, rope, boxes, pillows, shipping material, and a spare lead glove as needed.
• Aids should be waterproof and stain resistant as much as possible.
• Position aids/mechanical restraints with sand not beads.
• The GI tract must be free of feces and ingesta for abdominal studies.
• Gl tract prep involves laxatives or enemas when radiographying the abdomen.
• The bladder should also be empty so it won't displace other organs.
• Options include manual, mechanical, and chemical restraint.
• Chemical restraint may utilize Anxiolytics, Sedation, Anesthesia.
• Lower doses are often enough and is necessary for some studies..
• Mechanical aid for a dog is often a muzzle, but may require light sedation in the same instance.
• Chemical restraint may not be right for animals in trauma.
• Every sedative protocol carries some risk to the patient and every patient receiving sedative meds must have a complete pre-sedative examination.

Grids

• A device is placed between the patient and the film designed to absorb scatter.
• Grids can be under the tabletop between patient and the imaging plate; most are built in under the tabletop and correlated with the bucky tray.
• Composed of alternating strips of lead and spacer material.
• Lead strips are 0.5mm, and there should be a number of them(500-1500).
• The spacer is aluminum, plastic, or fiber
• Grids focus on aligning lead strips with the primary beam so rays reach the film.
• Lead strips absorb rays that are not traveling the same direction as the primary beam.
• Spacers are inert and permit primary rays to hit the film.
• The grid should have a focus at the focal point of the X-ray tube, machine should be calibrated
• Encased in protective plastic for durability.
• The more lead in a grid, the more scatter it absorbs, but, if the lead is too thick, it shows up on the radiograph.
• Eg. If height is 6 times greater than spacing distance, grid ratio is 6:1
• Linear grids have parallel lines that are consistent with the primary beam angle, but are limited to small x-ray fields.
• Types include linear, parallel, focused, and crossed.
• Linear and focused are the most common, and crossed is most effective.

Grid Cutoff

• Grid cutoff happens if SID is beyond range indicated by manufacture
• Cutoff happens if unintentional primary rays are absorbed giving way to decreased density on the sides of a radiograph
• Improper centering of the grid and the primary beam can cause cutoff
• Tilting the tube or the grid will affect cuttoff, or placing the focused grid upside-down and backwards