May/June 2013 Today’s Veterinary Practice 59

ImagIng EssEnTIalsPeer reviewed

Small animal Spinal RadiogRaphy SeRieS

Thoracic Spine radiographyDanielle Mauragis, CVT, and Clifford R. Berry, DVM, Diplomate ACVR

Spinal radiographs are indicated for:

• Evaluation of traumatic injuries

• Neck and back pain

• Pain or neurologic issues associated with

thoracic or pelvic limb lameness isolated to

these regions.

Each radiographic projection is a separate study and

should be radiographed as such. High quality, correctly

positioned and collimated radiographs are required in

order to provide an accurate assessment of the area of

interest, especially for surgical planning.

Measuring the thoracic spine

Measure the thickest portion of the spine

that is within the area of collimation.

Follow these precautions

as a general rule, general anesthesia or heavy

sedation is necessary to evaluate the spine

because, in most cases, spinal images taken

in nonsedated patients are nondiagnostic.

In addition, the presence or absence of disk

space narrowing cannot be determined from

a nonsedated animal’s radiographs due to

unavoidable positioning artifacts.

If a back injury (fracture) is suspected, DO

nOT flex or extend the spine of the injured dog

or cat, and DO nOT turn the patient for an or-

thogonal image. If possible, a horizontal beam

image is done for the ventrodorsal projection.

imaging essentials provides

comprehensive information on small

animal radiography techniques. This article

is the second in a 3-part series covering

cervical, thoracic, and lumbar spine

radiography.

The following anatomic areas

have been addressed in previous

columns; these articles are available at

todaysveterinarypractice.com (search

“Imaging Essentials”).

• Thorax

• scapula, shoulder, and humerus

• abdomen

• Elbow and antebrachium

• Pelvis

• Carpus and manus

• stifle joint and crus

• Tarsus and pes

| ImagIng EssEnTIals

Today’s Veterinary Practice May/June 201360

routine Views

Lateral and ventrodorsal views are considered the

minimum orthogonal radiographs for the spine. Due to

the angled, divergent nature of the x-ray beam, the area

of the spine in the center of the field of collimation will

be the area that provides the correct anatomic detail and

intervertebral disk space widths.

A routine thoracic spine study includes:

1. Lateral image of the thoracic spine

2. Ventrodorsal image of the thoracic spine

3. Lateral image of the thoracolumbar spine

4. Ventrodorsal image of the thoracolumbar spine.

lateral projection: thoracic spine

For the lateral projection, position the patient in lateral recumbency (Figure 1). • Tape the thoracic limbs together evenly

and pull cranially, keeping the sternum and vertebrae equidistant to the table. • a foam wedge may be placed under the

cubital joints and/or sternum in order to maintain laterality of the patient; wedges are typically needed for large-breed and/or barrel-chested dogs.• Tape the pelvic limbs together evenly and pull

caudally, keeping the patient in lateral position.• The thoracic spine should be aligned with

the horizontal line of the collimated field of view (FOV). To accomplish this alignment, the pelvis of the dog or cat may need to be shifted ventrally. To determine whether or not the patient is

aligned in a lateral position and parallel to the table, gauge the superimposition of the iliac wings by palpating the wings to ensure they are even.

lateral collimation

For the lateral projection, the FOV should:• Include the dorsum just above the spinous

processes• Exclude the sternum and ventral third of the

thoracic cavity.

For all patients:• Palpate the vertebrae of the thoracic spine by

following the ribs dorsally to where they meet

the vertebral bodies; place the horizontal line of the FOV at this plane.• accommodate the contour of the thoracic

spine from a ventral position cranially to a more dorsal position caudally.• Place the radiographic marker to the caudal

right or left of the patient to keep it from overlapping with important anatomic areas.

Ventrodorsal projection: thoracic spine

For the ventrodorsal projection, position the patient in dorsal recumbency (Figure 2). • If a trough is used, place the entire thoracic

spine within the trough to eliminate edge artifacts. • Extend the skull and neck and align with the

manubrium; the skull and cervical spine should also be aligned in a straight line cranially. • align the sternum over the thoracic spine; it

should be superimposed onto the thoracic spine on the final image. • Tape the thoracic limbs either together or

individually and pull cranially. • Tape the pelvic limbs individually and pull

caudally.

Ventrodorsal collimation

For the ventrodorsal projection, the FOV should: • Include the thoracic vertebral bodies,

B

a

Figure 1. Dog positioned for lateral projection of the tho-

racic spine (A) and corresponding radiograph (B).

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with only the rib head and proximal rib bodies visualized.• Exclude the lateral body

wall and mid zone to periph-eral portion of the middle and caudal lung fields.

For all patients:• Palpate the manubrium and

the xiphoid of the sternum; collimate just cranial to the manubrium and 3 finger widths caudal to the xiphoid. • Place the center of the FOV

halfway in between these landmarks, with the horizon-tal line of the FOV placed midline.• Place the radiographic

marker on the soft tissues of the ventrum at the most lateral edge of the colli-mated FOV.

lateral projection: thoracolumbar

Junction

Due to x-ray beam divergence, it is neces-sary to include a projection of the thora-columbar (T-l) junction for a spinal radio-graphic survey that includes the thoracic and lumbar spine.

For the thoracolumbar junction lateral pro-jection, position the patient in lateral recum-bency (Figure 3). • Tape the thoracic limbs together evenly and

pull cranially in the same manner as a lateral thoracic radiograph, keeping the sternum and vertebrae equidistant to the table. • a foam wedge may be placed under the

elbows in order to maintain laterality of the patient. • Tape the pelvic limbs together evenly and

pull caudally, keeping the patient in lateral position. To determine whether or not the patient is

aligned in a lateral position and parallel to the table, gauge the superimposition of the iliac wings by palpating the wings to ensure eveness.

lateral collimation

For the lateral projection, the FOV should include T10 through l3, including spinous

processes of the re-spective vertebrae. • Palpate the junc-

tion between the last thoracic ver-tebral body (T13) and the first lumbar vertebra (l1) by following the caudal border of the last rib dor-sally to the point where it joins the vertebral column.• Place the center of

the FOV 2 finger widths caudal to this space. • Place the radio-

graphic marker to the caudal right or left of the patient to keep it from overlapping with important ana-tomic areas.

Ba

Figure 2. Dog positioned for

ventrodorsal projection of the

thoracic spine (A) and corre-

sponding radiograph (B).

B

a

Figure 3. Dog positioned for lateral

projection of the thoracolumbar spine

(A) and corresponding radiograph (B).

| ImagIng EssEnTIals

Today’s Veterinary Practice May/June 201362

aDDitional Views

Ventrodorsal oblique projection: thoracic spine

Subtle lesions, fractures, and intervertebral disk disease

are a few of the conditions that may require a ventrodor-

sal oblique projection of the spine (Figure 5).

• From the straight ventrodorsal position of the thoracic

spine, obliquely rotate the patient to the left approxi-

mately 10° to 15°; then take the radiograph.

• Rotate the patient to the right approximately 10° to 15°

and take a second radiograph.

Collimate as described for the ventrodorsal projection of

the thoracic spine (page 60). The ventrodorsal oblique tho-

racic spine projection requires a larger collimated FOV on the

lateral aspect due to the curvature of the spine in that region.

QualitY control

To make certain the desired technique has been achieved,

use the following guidelines to determine whether the ap-

propriate anatomy is included in the images.

thoracic spine

For the lateral projection of the thoracic spine:

• The cranial border should include the caudal aspect of

Ventrodorsal projection:

thoracolumbar Junction

For the thoracolumbar junction ventro-dorsal projection, position the patient in dorsal recumbency (Figure 4). • If a trough is used, place the entire

thoracic spine within the trough to eliminate edge artifacts.

• Extend the skull and neck and align with the manubrium.

• align the sternum over the thoracic spine; it should be superimposed with the thoracic spine on the final image.

• Tape the thoracic limbs either together or individually and pull cranially.

• Tape the pelvic limbs individually and pull caudally.

Ventrodorsal collimation

For the ventrodorsal projection, the FOV should: • Include the thoracic vertebral bodies,

with only the immediate rib heads and soft tissues visualized.

• Exclude the lateral body wall and lungs of the thoracic cavity.

For all patients:• Palpate the xiphoid of the sternum and

the curve of the last rib in the lateral body wall. • Place the center of the FOV halfway in between

these landmarks, with the horizontal line of the

FOV placed midline.• Place the radiographic marker on the soft tissues

of the ventrum at the most lateral edge of the colli-mated FOV.

Ba

Figure 4. Dog positioned for ventrodorsal projection of the thora-

columbar spine (A) and corresponding radiograph (B).

the cervical spine (C7).

• The caudal border should, at least, include lumbar

vertebra 1 (L1).

• For the lateral position, the rib heads should be

superimposed at the vertebral body level.

For the ventrodorsal projection of the thoracic

spine:

• The cranial border should include the caudal

aspect of the cervical spine at the level of C7.

• The caudal border should, at least, include lumbar

vertebra 1 (L1).

• The spinous processes should be superimposed over

the thoracic vertebral bodies.

thoracolumbar Junction

For the lateral projection of the thoracolumbar junc-

tion:

• The cranial border should include the caudal

aspect of the thoracic spine near the level of thoracic

vertebra 11 (T11).

• The caudal border should, at least, include lumbar

vertebra 3 (L3).

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Figure 5. Dog positioned for ventrodorsal

oblique projection of the thoracic spine, with

the sternum obliqued toward the right (A) and

corresponding radiograph (B). Ventrodorsal

oblique projection of the thoracic spine, with

the sternum obliqued toward the left (C) and

corresponding radiograph (D).

c D

B

For quality control of any diagnostic image, follow a simple 3-step approach: 1. Is the technique adequate (appropriate

exposure and development factors)?2. Is the correct anatomy present within the

image? 3. Is the positioning anatomically correct

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May/June 2013 Today’s Veterinary Practice 65

ImagIng EssEnTIals |

• For a true lateral position, the rib heads should be

superimposed at the vertebral body level.

For the ventrodorsal projection of the thoracolumbar

junction:

• The cranial border should include the caudal aspect

of the thoracic spine at the level of T11.

• The caudal border should, at least, include L3.

• The spinous processes should be superimposed over

the thoracic and lumbar vertebral bodies.

• In a straight dorsoventral projection, the dorsal spi-

nous processes should have a tear drop appearance. n

Suggested Reading

Burk rL, Feeney dA. Small Animal Radiology and Ultrasonography: A

Diagnostic Atlas and Text, 3rd ed. Philadelphia: Saunders elsevier, 2003.

Keely JK, McAllister H, Graham JP. Diagnostic Radiology and

Ultrasonography of the Dog and Cat, 5th ed. Philadelphia: Saunders

elsevier, 2011.

Sirois M, Anthony e, Mauragis d. Handbook of Radiographic Positioning for

Veterinary Technicians. Clifton Park, NY: delmar Cengage Learning, 2010.

Thrall de (ed). Textbook of Veterinary Radiology, 5th ed. Philadelphia:

Saunders elsevier, 2008.

Thrall de, robertson id. Atlas of Normal Radiographic Anatomy and

Anatomic Variants in the Dog and Cat. Philadelphia: elsevier Saunders,

2011.

Danielle Mauragis,

CVT, is a radiology techni-cian at University of Florida College of Veterinary Medi-cine. She teaches veteri-nary students all aspects of the physics of diagnos-tic imaging, quality control of radiographs, positioning of small and large animals, and radiation safety. Ms.

Mauragis coauthored the Handbook of Radio-graphic Positioning for Veterinary Technicians (2009) and was the recipient of the Florida Veteri-nary Medical Association’s 2011 Certified Veterinary Technician of the Year Award. This award recognizes an individual for the many outstanding contributions that person has made to the overall success of a veterinary practice operated or staffed by an FVMA member veterinarian.

Clifford R. Berry, DVM, Diplomate ACVR, is a pro-fessor in diagnostic imaging at the University of Florida College of Veterinary Medi-cine. His research inter-ests include cross-sec-tional imaging of the thorax, nuclear medicine applica-tions in veterinary medicine, and molecular imaging ap-

plications of imaging in human and veterinary medi-cine. Dr. Berry has been a faculty member at North Carolina State University and University of Missouri. He received his DVM from University of Florida and completed a radiology residency at University of California–Davis.

Terry Marie Curtis, DVM, MS,

Diplomate ACVB, is head of the

Clinical Behavior Service at the

University of Florida College of

Veterinary Medicine and also

makes house calls in Florida

and South Georgia for behavior-

related cases. Dr. Curtis is the

author of a number of peer-re-

viewed articles, including book

chapters in veterinary Clinics of North America and

Blackwell’s Five-Minute veterinary Consult (5th ed).

She regularly lectures at the NAVC Conference, is co-

ordinator for its day-long behavior symposium, and

has appeared on ABC’s Nightline and NBC’s Today

Show. Dr. Curtis received her DVM from University of

Florida and completed her veterinary behavior resi-

dency and MS in psychology at University of Georgia.

have you seen how to enhance Your

pet’s enVironMent?

This practical 1-page client handout: • Highlights signs of stress in pets

• Provides suggestions for environmental enrichment

• lists helpful links for additional ideas.

It is available for download and use in your

clinic at todaysveterinarypractice.com. select

resources; then go to client aids & handouts.

reluctant to emerge for food, attention, or litter box use

• One or more cats is particularly focused on another cat

or cats (ie, bullying behavior)

• If a behavior issue continues to manifest despite the

owner implementing the solutions provided by his or

her veterinary team

• Any combination of the above. n

References

1. wolfe rC. The Social Organization of the Free Ranging Domestic Cat (Felis

catus). Phd dissertation, University of Georgia, 2001.

2. Beaver Bv. Feline Behavior: A Guide for Veterinarians. Philadelphia: wB

Saunders, 1992, pp 181-182.

3. Pachel C, Neilson JC. Comparison of feline water consumption between

still and flowing water sources: A pilot study. J Vet Behav Clin Appl Res

2010; 5(3):130-133.

4. Chon e. The effects of queen (Felis sylvestris)-rearing versus hand-rearing

on feline aggression and other problematic behaviors. Intl Vet Behav Meet

Proc, 2005, pp 201-202.

5. Neilson JC. Feline house soiling: elimination and marking behaviors. Vet

Clin North Am Small Anim Pract 2003; 33(2):296.

6. Panaman r. Behaviour and ecology of free-ranging female farm cats (Felis

catus L). Zeitschriftfür Tierpsychologie 1981; 56:59-73.

7. Feldman HN. Methods of scent marking in the domestic cat. Can J Zool

1994; 72:1093-1099.

8. Hart BL, Barrett re. effects of castration on fighting, roaming, and urine

spraying in adult male cats. JAVMA 1973; 163(3):290-292.

9. Beaver Bv. Feline Behavior: A Guide for Veterinarians. Philadelphia: wB

Saunders, 1992, p 209.

On YOuR BEsT BEHaVIOR |

(Behavior continued from page 70)