Flashcards in flash cards by mikayla Deck (61)
What other names is there for nuclear medicine?
What is nuclear medicine?
A modality which images the relative distribution of a radiopharmaceutical in the body or a particular organ
Steps in producing a Scintigram?
Select a suitable tracer (Radiopharmaceutical)
Administer to patient.
Acquire images with a GAMMA CAMERA
Process images with computer to give functional information.
What is Gamma Camera?
An instrument that produces quantitative images of the distribution of gamma emitting tracers within a patient.
A Scintigram can be in the form of:
Static images that reflect the uptake and therefore function of an organ.
Movie images that show the distribution of tracer as time passes.
Quantitative information e.g. graphs and uptake values.
Advantages of Nuc med:
Low patient dose
Disadvantages of Nuc med:
Poor anatomical detail
With reference to the gamma camera:i.) What is the crystal made from?
What is added to the crystal and why?
Thallium added to ensure that the scintillations are at the blue end of the visible spectrum.
iii) What is the relationship between the energy of a gamma ray and the size of the scintillation it produces.
The quantity of light being proportional to the energy of the incident photon. (unsure if correct)
Photons striking _____ interact by _____ or ______. Produce a ________: ____/UV light
Photons striking CRYSTAL interact by COMPTON or PE. Produce a scintillation: BLUE/UV light
What does a Light Guide do?
Provides optical coupling
between crystal and PM tubes
What are Photo Multiplier Tubes
Several PM tubes will detect each scintillation
Produce small electrical signal from each scintillation
Amplify it maintaining proportionality
What does a position computer do?
Produces x and y signals corresponding to the position of the event.
What does Pulse Height Analyser look at?
PHA “looks” at the z pulse corresponding
to each scintillation
ADC does what?
ADC processes the signal
into digital form
Information density means..
number of photons collected over region of interest
Spatial Resolution, what is it?
Ability to image two adjacent point sources
as separate points
What is it dependent on?
Intrinsic resolution (Ri)
Scatter component (Rsc)
Surrounding tissue produces Compton scatter
Some scattered photons will reach crystal.
Some will be within the 20% energy window.
Degrades the image
Worse at increasing depth
SPECT what is it? What is it?
What problem does it solve?
Problem-background activity in surrounding tissues and the increased amount of scatter limits the resolution and target to background ratio of the organ being imaged.
Solution-SPECT (Single Photon Emission Computed Tomography) Reconstruct using filtered back projection
Advantages of SPECT
Increased “pick up” of deep lesions
Correlate with CT
Disadvantages of SPECT
Requires special equipment
Careful setting up
Acquisition times 15-30 minutes
Uses for SPECT
Cardiac (myocardial Perfusion)
Gamma Camera Q.C. 3 parts;
Centre of Rotation
What is Field Uniformity?
Uniform response over whole field of view
Intrinsic (without collimator) Extrinsic (with collimator)
Linearity:Ability of a gamma camera to image a straight line in x and y planes
QC of centre of rotation
To ensure that the mechanical centre of rotation and the co-ordinates stored in the computer are the same.
Types of collimators? What are they called (2)?
High resolution &
High Sensitivity collimators.