Nuclear Medicine Flashcards
what is nuclear medicine?
It is a branch of medicine which involves application of radioactive substances for imaging and therapy
what are the steps involved in nuclear medicine?
- 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
what is difference b/w x-rays and nuclear medicine?
- x-rays provide structural and anatomical function
2. nuclear medicine provide physiological and functional information
Define radiopharmaceutical
- radio means radioactive element and pharmaceutical means drug or medicine
- therefore, radiopharmaceutical is a radioactive element/substance that can be administered into the body for diagnostic and therapeutic purposes
which radioisotope is used in DTPA scan or renogram?
technetium (gamma ray emitter) and DTPA (technetium labelled DTPA) is excreted by kinder which allows to measure the renal function and GFR
Define radioisotope
isotope is an element with same atomic number but different atomic mass so radioisotope is any isotope that is radioactive
why isotopes become radioactive and explain radioactive decay?
- due to an unstable nucleus
- the strong nuclear forces do not generate enough NBE to hold the nucleus together permanently
- therefore, to attain stability the nucleus emits an extra energy in the form of radiation and converts into a stable nucleus of lower energy
- this is called radioactive decay
what are the features of stable nucleus?
- equal number of protons and neutrons (lighter elements)
2. strong nuclear binding energy (NBE) to hold the nucleus together
what are three modes of decay?
- alpha decay or alpha particle emission
- beta decay or beta particle emission
- gamma decay
what are the features of alpha decay?
- rapid emission of an alpha particle (consist of 2 neutrons and 2 protons)
- the atomic mass of nucleus should >150 and
- the nucleus must have too few neutrons for the number of protons
- they have a short range in tissue so have little practical application
what are the features of beta decay?
- conversion of neutrons to protons and vice versa
- a particle have a mass equal to that of an electron is ejected from nucleus
- nucleus should contain too many neutrons
- the particle may have either positive (positron) or negative charge (negatron)
how many steps are there in decay process and what is decay scheme?
Decay process - can either be a single step with mode of decay or a multiple step process with one or many modes of decay
decay scheme - the graphical representation of decay process
Define
- physical half life
2. activity
- physical half life - it is the time taken by the radioactive isotope sample to decay to one half of its original value
- activity - total number of disintegration per second
- it is measured in becquerel (Bq)
- 1Bq = 1 nuclear disintegration per second
define
- biological half life
2. effective half life
- biological half life - it is the time taken by any chemical in an organ to reduce to half its original concentation
- effective half life - it is the time taken by certain radionuclide in a certain organ to be reduced to half its original activity
what are the properties of an ideal radioisotope?
- Have a short half-life
- Emit gamma-rays of relatively low energy
- Emit no particles
- Be added to the pharmaceutical without altering it’s chemical nature
- Be readily excreted
- Be easily generated
what is gamma camera?
- specialised imaging equipment
- able to detect gamma photons
- does NOT produce radiation
- design is evolving continuously
what does the gamma camera consists of?
collimator, detector, photomultiplier, electronics (used for creating images)
what is the detector in gamma ray
- made of
- its function
- efficiency
- made up of scintillation crystal, usually sodium iodide doped with thallium
- its function is convert gamma radiations into visible light
- inefficient process - only about 10% of gamma radiation is converted to light
what is structure and function of photomultiplier tube?
- consist of photocathode (where the the incoming light photon hits) , dynode (electron is passed through this) and anode (sends photomultiplier outputs as electric impulse)
- they are closely packed for optimum light detection
what is SPECT and what are its features?
SPECT - single photon emission computed tomography
- uses similar radiopharmaceuticals as 2D imaging - e.g. technetium based
- mode of acquisition changes, i.e. how the data is acquired and processed
- cross sectional imaging
what is PET and what are its features?
PET - positron emission tomography
- diffrent pharmaceutical to planar and SPECT imaging - FDG (flurodeoxyglucose)
- radiopharmaceuticals decay by the emission of positrons
- annihilation - positron travels a few mm then interacts with an electron -> 2 gamma photons are emitted and 180degree opposed to each other
- the camera detects the gamma rays to produce the image
name two 3D imaging techniques?
- SPECT
2. PET
what is the role of NM?
1. Physiological measurement Lung, heart, kidney, bone 2. Diagnosis of primary tumours 3. Diagnosis of secondary tumours (metastases) 4. Radionuclide therapy 2D- planar imaging technique 3D- SPECT and PET
