Nuclear Medicine Flashcards
Outline brief outline of nuclear medicine process
- Radiopharmaceuticals are taken internally, for example intravenously or orally.
- Then, external detectors (gamma cameras) capture and form images from the radiation emitted by the radiopharmaceuticals.
What is 2D: Scintigraphy (“scint”)
2D: Scintigraphy (“scint”) is the use of internal radionuclides to create two-dimensional images.
What is 3D: SPECT
3D: SPECT is a 3D tomographic technique that uses gamma camera data from many projections and can be reconstructed in different planes.
What is Positron emission tomography (PET)
Positron emission tomography (PET) uses coincidence detection to image functional processes.
Give 2 clinical applications of PET
- Neurological diseases such as Alzheimer’s and Multiple Sclerosis
- Cancer
- Effectiveness of treatments
- Heart conditions
Which of the following statements about Nuclear Medicine (NM) is NOT true?
A.NM relies on physiological processes to provide an image
B.NM uses radiopharmaceuticals
C.NM is solely used for diagnostic purposes
D.NM includes both 2D and 3D imaging
C.NM is solely used for diagnostic purposes
Why doesn’t NM provide anatomical information?
•NM relies on physiological processes and hence provides functional information and NOT anatomical information
What are the 3 main steps in NM?
- A suitable radiopharmaceutical (or radionuclide) is introduced into the patient;
- The radiopharmaceutical is allowed to concentrate in a specific organ;
- The organ is scanned using an appropriate scanner, e.g. gamma camera
Give 2 things NM can do
- •Physiological measurement
- •Lung, heart, kidney, bone
- •Diagnosis of primary tumours
- •Diagnosis of secondary tumours (metastases)
- •Radionuclide therapy
- 2D- planar imaging technique
- 3D- SPECT and PET
Give an overview of SPECT
- Single photon emission computed tomography
- Uses similar / same radiopharmaceuticals as 2D imaging
- e.g. technetium based
- Mode of acquisition changes
- i.e. how the data is acquired and processed
- Cross-sectional imaging
Give an overview of PET
- PET (Positron emission tomography)
- Different pharmaceutical to planar and SPECT imaging
- FDG (Flurodeoxygluocose) (18
- Radiopharmaceuticals decay by the emission of positrons
- Annihilation – positron travels a few mm then interacts with an electron
- Two gamma photons are emitted (511 keV)
- 1800 opposed to each other
- The camera detects gamma rays to produce the image
What type of nuclear instability results in positron emission?
- -Too many protons
- -Proton transformed into a neutron and a positron and neutrino are emitted
- -A is unchanged, Z is decreased, so the daughter product is a different element
Which of the following statements about radioactive decay process is NOT true?
A.Gamma rays have higher energy than α and β particles
B.During α decay a helium atom is ejected
C.During β decay the particle ejected can have positive or negative charge
D.Gamma rays are negatively charged
D.Gamma rays are negatively charged
What are the 3 modes of decay
- •Alpha decay or alpha particle emission
- •Beta decay or beta particle emission
- •Gamma decay
What is the difference between Gamma ray emission and alpha or beta decay
Gamma ray emission (not particulate like alpha or beta decay
The physical half-life of Technetium-99 metastable is 6 h. How much activity is needed at 9 am if 80 MBq is needed at 9 am next day?
A.2000 MBq
B.1280 MBq
C.320 MBq
D.160MBq
B.1280 MBq
Define Biological half-life
•is the time taken for the concentration of a certain chemical in an organ to be reduced to half its original concentration.
Define Effective half-life
is the time taken for the activity of a certain radionuclide in a certain organ to be reduced to half of its original activity.
•1/t1/2(eff)=1/t1/2(phys)+ 1/t1/2(bio)
The diagram depicts various parts of a gamma camera. What is the name of the part indicted by red arrow?
A.Detector
B.Collimator
C.Photomultiplier
D.Filter
A.Detector
Describe the detector from a gamma camera
- Scintillation crystal
- Usually sodium iodide crystal doped with thallium
- Converts gamma radiation into visible light
- Inefficient process
About 10% of incident gamma radiation converted to light
Technetium is a radioistope, which has many radiopharmaceuticals associated with it.
True or False: The associated radiopharmaceuticals have the same clinical applications
False
describe alpha decay
- Spontaneous emission of an alpha-particle (consists of 2 neutrons and 2 protons)
- The nucleus should have an A >150 and must have too few neutrons for the number of protons
- They have a short-range in tissue so have little practical application
Describe beta decay
- Nucleus should contain too many neutrons
- Conversion of neutrons to protons and vice versa
- A particle having a mass equal to that of an electron is ejected from nucleus
- The particle may have either positive (positron) or negative charge (negatron)
describe gamma decay
Gamma ray emission = wave (not particulate like alpha or beta decay)
what is a gamma camera
- Specialised imaging equipment
- Able to detect gamma photons
- Does NOT produce radiation
- Design is evolving continuously
how is NM used to measure metastatic spread
- Inject technetium
- Taken up by osteoblast- so measure the activity
- Come back 3 hours later for gamma scan
- Drink lots
- Gives less cloudy picture
- Reduces radiation dose/flushes through kidneys
- Reduces radiation dose
Sclerotic (osteoblastic activity) or nitic (osteoclast) metastases
what can NM be used to measure in orthopaedics
- Joint prostheses
- Inflammatory disease and Paget’s (rheumatology)
- Radiation Synovectomy
how can NM be used to measure infection
- Uptakes = infection?
- Inject on tables (dynamic scan- see blood flow/increased)
- Take 50mls of blood, remove white blood cells (label with gallium/indium)
- Re-infuse = trace
how can NM be used in GI pathology identification
- Gastrointestinal Bleeding Study (with Tc99m - RBC)
- Detection and localisation of gastrointestinal bleeding, and occult bleeding including lungs, retroperitoneal, and peripheral sites.
- Normal anatomy will take up lots of RBC’s as very metabolically active.
how can NM be used to assess gastric emptying
- Often to assess gastroparesis in diabetics.
- Tc-99m radiolabelled meal given – e.g. scrambled egg white followed by jam on toast or milk for fluids vs solids
- Sequences of images taken to assess the time taken for half the activity to leave the stomach
how can NM be used to assess liver function and pathology
- Tracking of bile flow through liver to gall bladder (if present) and then through to duodenum.
- Various pathologies e.g. cholecystitis, Sphincter of Oddi dysfunction, post-operative bile leak.
- Tc-99m HIDA given and patient imaged for up to 2 hours. May be given a fatty meal to empty gall bladder
how can NM be used to assess cardiac function
- Before transplant
- Stress/Rest test or pharmacological ie. adenosine
- Inject thallium or technicism then image via a SPECT scan immediately
- Need to consider both stress and resting state- transient ischaemia in heart due to angina, so won’t perfused. Can then compare if there are any defects
- May use second injection of thallium if rest can hasn’t re-perfused. To check if this is true or not.
what can filtered radionuclides be used for in urology
Evaluation of:
- perfusion of vascular supply
- filtration (renal function)
- drainage
What test would this be used instead of
micturating cystogram, as its better tolerated by children
How can NM be used for the thyroid
Used to show extent of uptake prior to therapy and / or nodules and adenomas and carcinomas
How can NM be used in neurology- specifically in dementia care
Measure cerebral perfusion to map dementia
