Basics and Indications of Ultrasound, Nuclear Scintigraphy, CT, and MRI

Question 1

describe benefits of fluoroscopy

Answer 1

1. radiographic cine loop (series of images instead of just one)
2. good for dynamic lesions like tracheal collapse, GI contrast/swallowing studies, and interventional radiology

still uses ionizing radiation though

Question 2

describe the basics of ultrasonography (3)

Answer 2

1. ultrasound waves that exceed normal hearing range
2. noninvasive and nonionizing
3. transducer is used to interrogate the area of interest; clipping hair and adding coupling gel to the skin helps
   -the higher the frequency, the better the image but the less deep the penetration (linear transducers have a higher freq)

Question 3

what are the 4 echogenicities of ultrasound?

Answer 3

1. hyperechoic: brighter than surroundings; more beams coming back
2. hypoechoic: darker than surroundings; fewer beams coming back
3. isoechoic: same shade as surroundings; same amount of US beams coming back as adjacent tissues
4. anechoic: no echos/beams coming back

Question 4

what are 8 indications for ultrasonography?

Answer 4

1. abdomen/coelom
2. neck
3. heart
4. musculoskeletal
5. ophthalmic
6. T-FAST/A-FAST
7. brain: only in smaller animals when skull is pretty thin or open fontanels
8. guidance for FNA and biopsy

Question 5

describe nuclear medicine/scintigraphy (3)

Answer 5

1. use of gamma rays (ionizing radiation)
2. administration of a radiopharmaceutical specific to the tissue type to be evaluated
3. radiopharmaceutical will accumulate in active areas and emit radiation, which will be captured by the gamma camera to generate FUNCTIONAL images

Question 6

what are the 3 main indications for nuclear medicine/scintigraphy?

Answer 6

1. bone scan: equine lameness, met check for small animals
2. thyroid
3. renal: GFR measure function of kidney over time

Question 7

describe computed topography (CT) (6)

Answer 7

1. x-ray generator and detector rotate 360 degrees around the patient acquiring images that are 3D using ionizing radiation
2. data is reformatted into different planes and windows (concentrate the shades of grey) to optimize evaluation of different structures (soft tissue, bone)
3. no superimposition of structures because takes slices!
4. excellent osseous detail
5. new machines make this a fast exam
6. use of IV contrast is very important!!

Question 8

what are the indications for CT?

Answer 8

almost everything (donut of truth)

1. gold standard for pulmonary evaluation
2. also good for oncology staging and the head
3. not indicated for CNS (central nervous system) and MSK (musculoskeletal); but unless you have an MRI, CT is the best option for CNS and MSK

Question 9

describe MRI

Answer 9

1. use a strong magnetic field and radiowaves to develop a digital image WITHOUT using ionizing radiation!
2. multiple sequences are used to increase the conspicuity of certain areas/structures
3. doesn’t obey the order of the shades of grey of the radiographs and CT!! because no ionizing radiation

Question 10

what is MRI indicated for? (2)

Answer 10

is the gold standard!!
for CNS and MSK (CT is secondary to MRI for these systems)