Download NUCLEAR SCINTIGRAPHY Scintigraphy is a method of imaging

NUCLEAR SCINTIGRAPHY
Scintigraphy is a method of imaging that emphasizes physiology rather than anatomy.
Whereas a radiograph or ultrasound takes an image of a patient's anatomy,
scintigraphy takes an image of a patient's physiological processes. This is
accomplished by administering a radioactive compound, allowing the compound to
accumulate within the patient, and then measuring the amount of radioactivity emitted
from the patient. A gamma camera is used to measure the radioactivity.
Fig. 7-12 A and B, A small piece of brown paper is
pressed over the packing material to protect it from
debris. C, The horse is allowed to set the hoof down once
the packing material has been covered.
The properties of the radioactive compound determine where in the body the
compound is likely to accumulate, according to the body organs that process the
compound; this is the physiological part of the image process. The radioactive
compound, or radiopharmaceutical, is made by attaching a radioisotope to another
compound that has an affinity for certain body organs, such as iodine for the thyroid
or phosphonates for bone. Technetium-99m is the most common radioisotope used
for the radiolabel.
Most large animal scintigraphy is performed to evaluate the musculoskeletal system;
skeletal scintigraphy is also known as a “bone scan.” The patient is sedated for the
procedure. Technetium-labeled diphosphonate is given intravenously to the patient,
and the diphosphonates are incorporated into the patient's bone, taking the radioactive
technetium “tags” with them. The radioactivity over the bone is then measured, and
high emission of radiation is assumed to reflect areas of increased blood flow in the
bone and/or uptake by osteoblasts—an indication of inflammation and/or new bone
formation. These areas of increased radioactivity are commonly called “hot spots.”
TABLE 7-1 RADIOGRAPHIC VIEWS OF THE EQUINE
LIMBS
Anatomical Part
Standard Radiographic Views
Supplemental Views
P3/Hoof
Straight DP
60 degrees DP (stand-on)
Lateromedial
60 degrees DP obliques (stand-on)
Navicular bone
Lateromedial
60 degrees DP(stand-on)
45 degrees flexor tangential (stand-on)
30 degrees DP (stand-on)
45 degrees DP (stand-on)
60 degrees DP obliques (stand-on)
Pastern
Lateromedial
Straight DP
Obliques (MLO, LMO)
30 degrees DP
Fetlock
Lateromedial
Flexed lateromedial
Straight DP
Obliques (MLO, LMO)
Hanging DP
Flexor skyline
Proximal-distal obliques (MLO, LMO)
Metacarpus/metatarsus
Lateromedial
DP
Obliques (MLO, LMO)
Carpus
Lateromedial
Flexed lateromedial
DP
Obliques (MLO, LMO)
Flexed skyline (distal radius)
Flexed skyline (proximal row carpal bones)
Flexed skyline (distal row carpal bones)
Radius
Lateromedial
Craniocaudal (AP)
Obliques (MLO, LMO)
Elbow
Mediolateral
Craniocaudal (AP)
Shoulder
Mediolateral
Tarsus
Lateromedial
DP
Obliques (MLO, LMO)
Flexed skyline
Flexed lateromedial
Tibia
Lateromedial
Craniocaudal (AP)
Obliques (MLO, LMO)
Stifle
Lateromedial
Caudocranial (PA)
Flexed lateromedial
Flexed skyline
Obliques (MLO, LMO)
Pelvis
Ventrodorsal
Ventrodorsal obliques
DP, Dorsopalmar/dorsoplantar; MLO, mediolateral oblique; LMO,
lateromedial oblique; AP, anteroposterior; PA, posteroanterior.
Scintigraphy is helpful in detecting lesions when radiography and ultrasonography
have not confirmed a diagnosis or cannot penetrate deeply enough, especially in the
regions of the upper limbs, shoulders, and pelvis. Scintigraphy can also screen large
areas of the patient (Fig. 7-13).
Only clinics or hospitals that are licensed to handle and dispose of radioactive
materials and waste can perform this procedure. The patient must usually be isolated
for several days until the radioactive material is cleared from the body; excrement
requires special handling requirements. Each state has regulations for licensing and
operating these facilities.