View source for 37. The fundamentals of nuclear medicine imaging. Types of radiation, applications.

* Fundamentals of nuclear medicine
** Nuclear medicine is ''functional'' not ''structural'' imaging
*** Measures the function of organ or tissue, not the structure
*** Can be combined with conventional imaging to produce functional + structural images
**** For example PET/CT
** A patient is given a short-lived radioactive material
*** This is called a radioactive isotope, radiotracer or radionuclide
*** Half-life of minutes or hours
** The radionuclide is attached to a carrier compound (a pharmaceutical) which concentrates in certain tissues
*** This combination is called a radiopharmaceutical
*** Examples of radiopharmaceuticals
**** F18-FDG = fluorine-18 + fluorodeoxyglucose (FDG)
***** Fluorine-18 is radioactive (emits positrons)
***** FDG concentrates in tumors
**** 99mTc-pertechnetate = technetium-99m + pertechnetate
***** Technetium-99m emits gamma rays
****** 99mTc is the most widely used radioisotope
***** Pertechnetate concentrates in thyroid, brain
**** '''Iodine-131'''
***** No carrier compound needed; the radioactive isotope I-131 concentrates in the thyroid
***** I-131 emits both gamma and beta rays
***** '''Can be used both for thyroid imaging and destruction of thyroid cancer'''
** The radiation emitted by the radiopharmaceutical is detected by a so-called ''gamma camera''
** Most nuclear medicine scans have a resolution of about 1 cm
*** Meaning that they can’t detect lesions smaller than that
** Most common types
*** Single photon emission computed tomography (SPECT)
**** Less expensive than PET but worse contrast and resolution
**** Uses gamma-emitting radioisotopes
***** '''Technetium-99m'''
***** Iodine-123
**** Especially used in
***** Myocardial perfusion imaging
***** Bone imaging
***** Functional brain imaging
*** Positron emission tomography (PET)
**** More expensive than SPECT but better contrast and resolution
**** Metabolic changes in the heart, brain and tumours can be examined
**** Uses positron-emitting radioisotopes
***** '''18F-FDG (most frequent)'''
***** Radioisotopes used in PET have ultrashort half-lives
****** They must therefore be made at the site of the examination
**** Indications
***** Diagnosis and follow-up of cancer
***** Locate hidden metastases
***** Detect recurrence of cancer
***** Measure brain activity
**** Physics
***** The patient is given an isotope which releases positrons
***** Inside the body these positrons will meet with electrons. They will annihilate each other
***** '''The annihilation produces gamma photons which are detected'''
*** Bone scan
*** Ventilation/perfusion scan
*** Cardiac scans
*** Thyroid scans
* (Important) types of radiation
** Beta particles
*** High-energy, high-speed electrons or positrons
*** Deliver high radiation dose to the patient
**** A disadvantage for imaging
**** An advantage for tissue destruction
** Gamma waves
*** Lower energy
*** Good for imaging
*** Similar to x-rays

[[Category:Clinical Radiology (POTE course)]]