Radionuclide Imaging Flashcards
Disadvantages of a radionuclide..
-Lacks diagnostic specificity
-Relatively poor resolution
-Relatively long scan times
What does a Gamma Camera do?
Detects and measures the radiation that is emitted before the location is recorded
Define Radionuclide
The nuclei of an atom that is unstable and tends to “fly apart”, emitting radiation (also known as radioisotope)
What are some functions of Radioisotopes?
-Undergo spontaneous changes in their nuclei to either form a stable element -Become another radionuclide which undergoes further decay
-Breakdown and decay to cause alpha, beta and gamma ray/particle emission
-Undergo random processes that can be predicted and measured using radionuclide rates of decay
What are 4 advantages of using radioactive substances?
-Target treatment to specific cells
-Find disease at its earliest stage
-Used for cancer, trauma and infection
-Monitors response to treatment
What other advantages of RNI are there?
-Demonstration of rough anatomical structures, functionality of organs, size and shape of pathology
-Relatively low dose
-Highly sensitive to physiological/metabolical changes
-Determines how the body is functioning at a cellular level
List 6 components of a Gamma Camera:
-Display Unit
-Amplifier
-Pulse Height Analyser
-Large Sodium Iodide Scintillator
-Photomultiplier
-Computer Processing Unit
-Collimator
What is Spatial Resolution?
A measure of the smallest object that the imaging system can distinguish between. The smaller the holes in the collimator, the greater the SR but it cannot compare to X-ray SR
What are the 3 routes of radionuclide disposal?
-Liquid: Drainage/sewer systems and sinks/toilets
-Solid: Incineration and landfill
-Gas: Fume cupboard and exhaust into atmosphere
What properties do Scintillation crystals hold?
-High atomic density
-Fast conversion
-Good absorption
-Air and light proof containment (Hermetically sealed in an aluminium can)
-Low cost
-Transparent
-Efficient converter of radiation into light at an optimum wavelength for PMT sensitivity
What does Sensitivity mean?
The amount of radiation getting through to the detector. The larger the holes in the collimator the greater the sensitivity.
What is the half-life of Technetium (99mTc) and the area of interest it is used for?
-6 hours
- Salivary gland, Thyroid, Bone, Liver, Lung & Heart
True or False?
I-131 is used for the Thyroid and has a half-life of 10 days.
False. I-131 has a half-life of 8 days
What are 5 side effects of RNI treatment?
-Drowsiness
-Swelling of the throat, hands and feet
-Stomach pain
-Fainting
-Sensitivity to rapid temperature changes
-Fever
-Chills
-Difficulty breathing
The ideal properties of a radionuclide are:
-Short half-life
-Cheap
-Readily available
-Non-toxic/allergenic
-Stable
-Good shelf life
-A single target organ
-Emits only Gamma radiation at 120-300KeV
Which radioisotopes are inhaled into the lungs?
Xenon-133 and Krypton-81m
Bones are the specific target organ for which radionuclides?
99mTc-MDP and 99mTc
Collimator said have high attenuation due to lead plates which are either:
-LEAP (low-energy all purpose)
-MEAP (medium-energy “)
-HEAP (high-energy “)
-LEUHR (low-energy high resolution)
Usually parallel collimators
Which radionuclide is subcutaneously administered into Lymph Nodes?
99mTc
What are the safety guidelines after using Iodine 131?
-Drink at least 2 pints of fluid (water)
-Urinate sitting down and flush twice
-Avoid public transport
-Stop breast-feeding before starting treatment
-Pregnant women to avoid sharing utensils, food and having skin-to-skin contact
-Avoid contact with pregnant women and children
How must the decontamination of spills be managed?
-Contain and avoid spread
-Notify RPS and prioritise injuries
-Decontaminate affected patients and staff
-Write incident report to RPA for evaluation
What do the terms RPS and RPA mean?
Radiation Protection Supervisor and Radiation Protection Advisor
What must be recorded first when dose is administered?
The absolute dose
True or False?
After flushing with saline, not all measured dose goes into the patient as some is retained in the syringe.
True.
What is essential to know when calculating the differential function of an organ?
Exactly how much radioactivity has gone into the patient.
How do you calculate the absolute dose?
Original drawn up dose - Residual dose
Why is the injected dose entered into the system?
So that differential function can be calculated.
When is it especially important to calculate the differential function of a patient and why?
When treating paediatric patients because the dose levels are so low and the volume of injected radiopharmaceuticals are small (0.1ml)
How long is the half-life of Gallium (67Ga) and what is the “target organ”?
78 hours and inflamed Tumours
Explain the process of radionuclide combination.
-Combines with a carrier molecule to form a radiopharmaceutical
-Carrier molecules are selected to target specific organs/tissues
-Only small amounts and low doses are considered safe and diagnostic of precautions are taken
