IMAGING techniques

1. VM 352
Prof. Modesta Makungu
Dept. of Veterinary Surgery and
Theriogenology
2022
OTHER IMAGING
TECHNIQUES

2. Fiberoptic endoscopy
• Is a non invasive technique for evaluating the
lumen and mucosa of the gastrointestinal tract
• A knowledge of the normal appearance of various
luminal surfaces and the underlying anatomy is
essential
• Requires general anaesthesia
• Many git lesions have a polymorphic appearance.
Therefore biopsy is mandatory for definitive
diagnosis

3. Fiberoptic endoscope

4. Indications
• Oesophagus
-Oesophagitis
-Foreign body obstruction
-Neoplasia
-Stricture
-Gastroeosophageal intussusception
-Hiatal hernia

5. • Stomach
-Acute and chronic gastritis
-Gastric ulceration
-Foreign body
-Neoplasia
-Pyloric sternosis
-Hypertrophic gastropathies

6. • Small intestines
-Ulceration
-Chronic inflammatory disorders
-Foreign body
-Neoplasia
• Colon
-Colitis
-Neoplasia
-Ileocolic intussusception

7. Endoscopic procedure
• The animal must be fasted for 24 hours
- Allow ingesta to pass from the stomach and
upper intestine
- Preparation for general anaesthesia
• For upper digestive tract
- Animal should be in left lateral recumbency
(releases the pylorus and pyloroduodenal angle
from the weight of the viscera)
• General anaesthesia
• Moderate insufflation

8. Endoscopic procedure
• A colonoscopy is also performed on an
animal in left lateral recumbency,
• Avoids accumulation of liquid within the
transverse colon and ease the passage of
the endoscope beyond the splenic flexure
of the colon
• Moderate insufflation

9. Normal appearance
• Oesophagus
Pale pink in colour Ulcerative oesophagitis

10. Oesophageal foreign body
Oesophageal stricture
Normal oesophagus

11. • Stomach
Normal gastric mucosa Haemorrhagic gastritis

12. • Colon
Normal colon Colitis

13. PRINCIPLES OF COMPUTED
TOMOGRAPHY

14. Computed tomography (CT):
• Is the process of production of cross
sectional images using X-rays and
computers
• Advantages of CT over conventional X-ray
techniques
- Superior soft tissue differentiation
- No superimposition of overlying structures

15. CT
• Tomogram – an image of a slice or cut
through a body part
• CT, MRI and ultrasound are all tomograms

16. CT Physics
• Heavy duty x-ray tube rotates around the
patient
• Multiple x-ray beam projections are made
through the patient

17. CT Physics
• The x-rays are attenuated by the tissues
• The remnant radiation strikes a circular or
curvilinear array of detectors

18. CT Physics
• The detectors when stimulated convert the
radiation into an electric signal
• The computer processes all the digital
signals in a complex algorithm
• A transverse (axial) image is reconstructed
and displayed

19. CT Physics
• Image is composed of pixel
• Pixel = 2D square
• Voxel = 3D block of tissue
• Each pixel represents attenuation in a
voxel

21. Image processing
• The amount of remnant radiation passing
through the voxel is dependant on the
attenuation of that voxel

22. Image processing
• Each pixel is given a certain grey scale
• Grey scale = attenuation of voxel of tissue
• Grey scale = CT number = HOUNSFIELD
UNITS

23. Image processing
• CT number of water = 0
• All other tissues are
compared to water and
assigned a CT number
(from -1000 to +4000)
• The higher the CT number the brighter (or
denser) the pixel

24. Image processing

25. Advantages of CT
• Excellent contrast resolution
• Cross sectional anatomy avoids super
imposition
• Rapid image acquisition
• Post-acquisition digital manipulation
including multiplanar and 3D
reconstruction

26. Disadvantage of CT
• Radiation dose

27. Image Display;
• Multiplanar reformatting
• Maximum Intensity Projection
• Surface Shaded Display
• Volume Rendering Technic

28. Components of a CT scanner

32. Clinical applications
• Head
- Fractures
- Tumours
• Spine
- Disc prolapses
- Fractures
- Neoplasia
• Thorax
• Abdomen
• Joints

33. Principles of magnetic resonance
imaging (MRI)

34. Advantages of MRI compared to other
imaging modalities
• Excellent soft tissue contrast
• Cross sectional images
• No ionizing radiation
NB: Ideal for central nervous system imaging

35. • The patient is placed in a high magnetic field
• A radiofrequency wave is applied and which
interacts with protons in the patient
• The radiofrequency wave is turned off which
results in a signal being emitted from patient
• The signal is received by an antenna and the
image is reconstructed by computer
• The RF pulse frequencies are varied in duration
and strength to produce T1 and T2 weighted
images

38. T2 T1

39. Imaging planes
• Sagittal
• Transverse
• Dorsal

40. Hydrocephalus
Courtesy University of Pretoria

41. Meningioma

42. Precautions

43. Disadvantages
• General anaesthesia
• Limitation use in patients with
- Ferrous implants
Can cause artefacts and can be pulled out
of patient

44. Nuclear Medicine

45. Scintigraphy
• Diagnose abnormal function
• Detect diseases that alter the physiology

46. Scintigraphy
• Some atoms have nuclei with excess
energy = radionuclide
• Abnormally excited state
• Undergoes radioactive decay to become
more stable
• Emits particles and energy (β, α, ɤ rays)

47. Scintigraphy
• Radionuclide bound to a localising agent =
radiopharmaceutical
• Injected IV
• Localises in a particular body region
• Undergoes radioactive decay
• Emits gamma rays = imaged with gamma
camera

49. Radioactive decay
• Rate of decay specific for each
radionuclide
• Expressed as radioactive half-life
• Half life = time required for 50% of
radioactivity to decay
• Becquerel = 1 disintegration per second
• Curie = 3.7 x 1010 disintegration per
second

50. 99m-Technetium
• Most commonly used
• Formed by decay of Molybdenum
• Easily generated
• Binds to various RPs
• Half-life = 6 hours
• Emits gamma rays
• 140 keV photon is readily detectable

51. Radiopharmaceutical kits
• Sterile reaction vial with non-radioactive
chemical

52. Gamma Camera
• Scintillation detector
• Counts
• Detects position

53. Gamma Camera
• Collimator
• NaI scintillation crystal
• Photomultiplier (PM) tubes
• Positional circuitry
• Pulse height analyzer
• Computer

54. Image evaluation
• Decreased RP uptake = photopaenia “cold
spot”
• Increased RP uptake = “hot spot”
• Always compare to opposite limb at the
same time

55. Clinical application
• Bone
• Thyroid
• Portosystemic shunts

56. FLUOROSCOPY

57. Fluoroscopy
• Is a specialized type of x-ray examination
used primarily to visualize the continuous
movement of internal structures
• Provides a real time radiographic viewing of
moving anatomic structures
• Uses an X-ray tube, image intensifier and
television viewing system

58. Indications
• For assessment of motility and function of
the pharynx, oesophagus, stomach and
bowel
• Evaluation of respiratory function
- tracheal collapse
- bronchial collapse
- observe diaphragmatic movement
• To direct internal organs biopsies and
aspirates e.g. lung

59. Fluoroscopic system consists of:
• X-ray tube
• Image intensifier tube
• Television viewing system
NB: Most fluoroscopic systems
have the X-ray tube located
under the table

60. X-ray tube
• Generation of X-rays

61. Image intensifier tube
• Has an input and output fluorescent screens
• Screens contains crystals
• Converts x-ray image;
- into light image,
- then to an electron image
- and finally back to a light
image of diminished size
and increased brightness

62. • The image is viewed through closed-circuit
television
• Permanent records of fluoroscopic images
can be recorded on x-ray films (spot film) or
video tape

64. Radiation exposure
• Radiology personnel involved in fluoroscopy
receive higher exposures because of the long
fluoroscopic times that are used
• Radiation exposure to personnel is the major
disadvantage of doing fluoroscopy in animals
• Therefore fluoroscopic studies should used only
when specifically indicated
• Should be performed by a veterinary radiologist or
similarly trained person who is knowledgeable
about radiation protection and the equipment