Alternative Imaging Techniques

1. EQUINE MEDICINE
Alternative Imaging Techniques: Ultrasound, MRI, CT Scan

2. Ultrasound
Evaluation of soft tissue
Transducer- Probe that uses sound waves to image tissues
Echo-Sound waves that bounce off tissues and travel back
to the transducer
Converted by a computer into a gray scale image

3. Transducers
Sector Scan-Pie-shaped image
Phased Array-Crystals pulsed sequentially
Delay between pulses
Annular Array-Crystals in ring
Pulse directed through crystals
Use: Limited access areas

4. Transducers
Linear Array Scan-Rectangular-shaped image
Alternate pulse on groups of crystals
Use: Unrestricted areas
Equine tendons
Transrectal imaging

5. Patient Preparation
Clip or shave area
Scrub area with shampoo & rinse thoroughly
Wipe area with alcohol
Use acoustic coupling gel to eliminate air

6. Imaging

7. Digital Radiography
Basis for all digital images is the DICOM file format

8. Digital Radiography
DICOM: Digital Imaging & Communications in Medicine
Standard: Secure standardized images
Reliable accurate images
Hold up under legal scrutiny
Other formats: jpeg, tiff, gif, png, psg
Need viewing program to use!!!!

9. Digital Radiography
Image Quality: Hardware & software used
Imagine detector
Image processing
Monitor

10. Computed Radiography
Replaces film, intensifying screen & cassette with an imaging plate
Processor is replaced with a digital imaging reader
Advantages:
Digital imaging
Retrofit of equipment
Mobile
Relatively inexpensive
Disadvantages:
Imaging plate needed
Single plate development
Image reader needed

11. Direct Digital Radiography
Radiographic film & cassette are replaced with an imaging sensor
Advantages:
Digital imaging
Partial retrofit of equipment
Immediate image generation
No processing
No imaging plate
Image quailty
Disadvantages:
Cost
Sensor attachment by wire

12. Computed Axial Tomography
Produces cross-sectional imaging
X-ray beam is highly collimated, & rotates around animal to obtain image

13. Computed Axial Tomography
Voxel-Density of a small volume within a patient
Projected onto screen or film to produce image
Advantages: Detects small tissue density differences
Highly detailed image produced
Ability to see deep/small changes
Disadvantages: Cost
Requires general anesthesia
Gantry opening may limit patient access

14. Magnetic Resonance Imaging
Uses hydrogen protons in the body to produce a detailed image
Animal placed in a magnetic field
Magnet aligns hydrogen protons in the same direction
Pulse of high energy radio frequency disrupts alignment
Radiofrequency is released as atoms realign-imaged produced

15. Magnetic Resonance Imaging
System Types:
High Field System
1.0 T magnetic field
Higher detail image
Fast image production
General anesthesia required
Low Field System
<0.5 T
Lower image quality
Longer acquisition times
Animal may be standing

16. Magnetic Resonance Imaging
Imaging Protocols
Proton Density-Clear anatomic structure
T2 Weighting-High fluid contrast
T1 Weighting-Good bone definition
Variations
Short Tau Inversion Recovery (STIR)
Fat Suppression (FS)
Water-Excitation (WE)

17. Imaging

18. Nuclear Scintigraphy
Radioactive substance injected into the body & traced as it interacts with tissues
May localize problem area, will not determine cause
Advantages: May be performed in a standing animal
Single injection used to image entire animal
Image Production:
Gamma rays are acquired through a collimator
Computer uses information to produce an image

19. Nuclear Scintigraphy
Phases of Distribution:
Vascular Phase: Immediately after injection
Represents vascular blood flow
Early Pool Phase:
Soft tissue phase
Lasts 15 min
Diffusion from blood vessels to tissues
Late Pool Phase:
Bone phase
2-3 hr post injection up to 24 hrs