27 Gamma Camera Flashcards
What is the whole point of using a gamma camera compared to x ray, cat scan?
Gamma camera models images based on the FUNCTION of an organ for example, rather than the direct anatomy of it
This allows for diagnosis of a problem ti do with functions instead
This happens in REAL TIME, and thus gamma camera and medical travel can model the function of kidney, brain , to see cancers etc
What is a medical tracer and how does it work
A chemical Compound where some of its atoms have been replaced by a RADIOISOTOPE, tehcneituim 99-m or fluorine 18 in this case
Essentially the compound selected is intentiwlly selected such that the organ wished ti model absorbs it specifically, and thus if radiation is detected we know the function of the organ is correct or not etc
Concentration of the medical tracer can be used to detect irregularities of the function of the brain
How can a medical tracer be used to model function.
The concentration of the radioisotopes can be used to diagnose any irregularities with the function of the organ, as the medical tracer has been designed specifically for the organ in question
Properties of the medical tracer
The radioiosptpe must
- have a short half life
Why?
- such that the activity is high and thus a clear image is produced ( due to higher intensity of gamma photons)
- such that it does not remain in high contractions of large periods of time in the patient, which not only affects the the patient but poses a risk to OTHERS too
- but half life must be long enough such for the image ti be captured , too short and it could emit before it has reached the organ
In terms of what radiation
- preferably gamma
- such that high penetration but LOW ionising, minimises risk ti oateitn, and allows for the gamma camera to successfully actually detect the radiation being emitted
Why does having a small half life benefit
Means high activity
Which means ONLY A SMALL AMOUNT OF RADIOACTIVE SOURCE IS NEEDED IN BODY to produce a clear enough image in a short time !
So large concs aren’t needed because acticity is high !
(Ofc also won’t stay in for long)
What radioactive isotope is used in gamma scans
Tech ietium 99m
Which is AN ISOTOPE OF TECHNETIUM , not the real thing
Half life 6 hours
And decay releases gamma photons
Gamma camera components to explore
- Collimator
- scintillator
- photomultiplier tubes
- computer
Image
Explain each component of the gamma camera
Collinator
1) collimator
- these are series of parallel thin tubes of LEAD
- their objective is to absorb any gamma photons that DONT travel along the axis of the tubes
- here this ensures only gamma photons travelling along the axis reaches the coolinator.
- the purpose of this is to increase the probability of knowing exactly where the gamma photons came from, and thus REDUCE BLUR
To increase clarity, keep the tubes of lead as close as possible, as this increases the clarity of where thr gamma photons came from
Scintillator
Gamma photons arriving at the scintillator will produce thousands of photons of visible light
Follow the light guide and then PHOTOMULTIPER TIBES
Rays of visible light arriving at the photomultiplier tubes, the tubes convert these light rays into ELECTRICAL / VOLTAGE SIGNALS, which are then sent to the computer to be processed
The computer can then produce an image in real time based on these impacts
Gamma camera again
The photons of gamma travel through thr collimator and reach at the scintillator
- the collimator is an array of lead tubes parallel to each other, with purpose ti ensure only gamma photons along the axis of the lead tubes arrive at the scintillator, ti increase surety of the whereabouts of the incoming gamma photon, DIRECLTY below it
- without them, the image produced would be blurry, as it would be unclear to where the gamma photons came from
- more thinner, the better
2) arriving at the scineta,toe, the gamma photons produce thousands of visible light ohotons
3) these travel to the photomultiplier,tiler tubes, which convert each light photon into an electrical, signal, which are all sent to the computer
4) computer processes this, and based on the impacts produces an image showing the concentration of the technetium , which can be used to diagnose the function
Why must genetics be produce on hospital ?
Bevause short half life of 6 hours, means it would start emitting if produced elsewhere,
What is the job of a LEAD SHIELD AWROUND THE GAMMA CAMERA
To stop any random background radiation from arriving at the scintillator, or the photumtupleir tube
By the fact gamma camera real time good
This is good bevause it allows for monrotijg. Of rapdily changign situations, whereas x ray is 2D shadow
Here the image does,ruin is trash but the purpose is for function
