Ultrasound what does it allow you to see, and what is the specificity and safety
What is involved with preparing the patient for ultrasound and echocardiology
What are 3 important reasons to sedate during ultrasound
What are the 3 types of ultrasound
1) B-mode imaging - most common - provides a real time cross-sectional 2D image
2) M-mode imaging - provides a graphical trace of motion over time and is used in echocardiography
3) doppler mode - provides information on blood flow
Doppler mode what does it provide information on, how to interpret and the 2 types
How are ultrasound images made
what determines the depth and brightness of displayed echo
What are the 3 interactions of sound with tissue
What are the 2 things that influence the rate of sound attenuation
Acoustic impedance mismatch what is it and what are the 2 main structures involved
What does the ultrasound transudcer do and what are the 3 types
Ultrasound transducer what should you consider
When selecting a transducer, consider the frequency and the footprint of the transducer.
- Low frequency transducers are used to image deep structures BUT LOW SPATIAL RESOLUTION
Spartial resolution in terms of ultrasound what are the 2 types and what makes better resolution
Contrast resolution in terms of ultrasound what is it and what are the 2 things its controlled by
ability to display differences in echogenicity (greyness) of objects
1) Controlled by dynamic range
○ Use a low dynamic range for echocardiography
§ Difference between parenchyma and lumen
○ Use high dynamic range for abdominal ultrasound
§ Want to see all the shades of grey
2) Also our ability to perceive the different echogenicity
○ Best seen in low gain setting and in darkened conditions
Define echogenicity, anechoic, hypoechoic, hyperechoic and isoechoic
Nuclear scintigrapy what does it do and the 3 molecules involved
- images the distribution of a radiopharmaceutical within the body, using a gamma camera resulting in structure and function ○ Make the body radioactive 1) Radionuclide 2) Radioactivity 3) Radiopharmaceutical
What is a radionuclide, radioactivity and radiopharmaceutical
1) Radionuclide
○ radioactive atom with an unstable nucleus
○ undergoes radioactive decay and emits the excess energy as radiation
2) Radioactivity [Bq]
○ rate of radioactive decay of a radionuclide with spontaneous emission of radiation
○ Half-life = time taken for radioactivity to reduce by half
3) Radiopharmaceutical
○ chemical containing a radionuclide, suitable for in vivo use to diagnose or treat disease
What is radioactivity dosage and radiation dose
Radioactivity dosage - amount of radioactivity administered to a patient
Radiation dose - amount of radiation absorbed by the body tissues
In terms of nuclear scintigraphy what does the radiopharmaceutical do, what is it made up of and example
radiopharmaceutical = radionuclide + ligand
- radiopharmaceutical allows the radionuclide to target the area of interest
○ Ligand - determines the physiologic distribution
Ligand eg - ○ 99mTc-MDP = Technetium Methylene Diphosphonate
§ bone scintigraphy
How does technetium work in terms of nuclear scintigraphy and what is the half life
Technetium starts as Mo and undergoes beta decay -> Tc which emits gamma rays as transitions from metastable to stable state (we get Tc at the metastable state)
HALF LIFE of 6 hours from metastable to stable state -> want to order the day before doing the study as doesn’t last as long
Generally at background levels within 24 hours
What are the 2 types of nuclear scintigraphy and what information do they provide
1) static acquisition - anatomic information - common to localise lameness in horses
2) dynamic acquisition - provides functional information - get multiple reading over time so see the movement of the radiopharmaceutical
Static acquisition nuclear scintigraphy what information does it provide and what used for
Dynamic acquisition nuclear acquisition what information does it provide and the 2 main types
Dynamic acquisition provides functional information -> get multiple reading over time so see the movement of the radiopharmaceutical
1) Renal scintigraphy to measure GFR -> much more common in cats but still not as common
§ may be important to see when removing a kidney that the other kidney is functioning and won’t lead to kidney failure
§ Time activity curves allow you to quantify the GFR
2) Portal scintigraphy to diagnose portosystemic shunt - not as common anymore mainly just for laboratory testing
§ With a shunt over time the peak of radiopharmaceutical the peak occurs in the heart first and then liver or sometimes no peak in the liver -> BOTH SENSITIVE AND SPECIFIC FOR THIS DIAGNOSIS
Dynamic acquisition what are the main advantages and disadvantages
Advantages
- Provides functional information
- May be very sensitive -> sensitive at detecting physiologic processes
Disadvantages
- Poor anatomic resolution
- May have poor to moderate specificity
○ May be a “Hot spot” in the right shoulder = increased bone turnover but is it neoplasia, osteomyelitis, fracture
○ THEREFORE scintigraphy is usually followed up with other images modalities and/or biopsy
- The patient emits gamma radiation
○ Technetium is excreted by urine, faeces and saliva