COLLOQ 1 Flashcards
What is nuclear medicine?
Is the application of radionuclides (RN) for the purpose of:
> m. DIAGNOSIS (radionuclide diagnosis RND)
> RADIOTHERPAY (RT)
-metabolic brachytherapy (use of short range radio source to treat tumors)
What radioactivity?
spontantenous change of mass, electrical charge or energy of atomic nucleus with the emission of a, b or g emissions
What are the types of ionising radiation?
> direct ionising radiation
> indirect ionising radiation
Give examples of direct and indirect ionising radiation?
> direct IR - alpha + beta
> indirect IR - gamma + roentgen
What is a radionuclide?
Elements whose nuclei has the ability to decay - emitting ionising/ radioactive rays
Give examples of RN particulates ?
> beta electrons
beta positrons
alpha
Give examples of RN electromagnetic/ photon rays
> gamma rays
Outline the main elements of radioactive families?
> thorium
uranium
actinium
neuptinium
What is the penetrating ability of alpha, beta and gamma?
alpha + beta = short penetration
gamma = deep penetration
What is absorbed dose?
measure of the energy deposited in matter by ionizing radiation per unit mass
> units: Gray (Gy)
What does the biological effect of IR depend on?
> DOSE
How does DOSE affect the biological effect of IR?
> higher the dose»_space; greater the damage effect on living tissue
How does IR work in RT (radiotherapy) ?
> IR damages DNA of exposed tissues ( cancer + normal cells)»_space; leading to cellular death
What is the ALARA principle?
1) the radiation dose received by P must be ALARA
As Low As possible/ Reasonably Achievable
2) the ratio of risk vs benefit should be kept ALARA
As Low As possible/ Reasonably Achievable
Outline the uses of electromagnetic rays and particulate rays?
> electromagnetic rays (Y)
- long range
- deep penetration
- detected outside body
- low energy
- low dose
- RND radio nuclear diagnosis
> particulate rays (a + b)
- short range
- short penetration
- not detected outside body
- so not useful for RND
- high dose
- RT (metabolic brachytherapy)
What is the RN emission for Iodine 131?
> both Y and b-
Y = RND
b- = RT
What is the RN emission for Technetium (Tc) 99?
> pure Y emission
> for RND
What is the RN emission for Fluorine 18 + Gallium 68?
> b positron
pairs of annihilation Y photons
PET scans (Positron emission tomography)
Define pharmaceuticals?
chemical compounds with selective accumulations/ uptake by certain organs/ tissues
What specific compounds are used for bone metabolism and thyroid metabolism?
> bone - phosphates
> thyroid - iodine
Outline Radiopharmaceuticals (RPh) for bone specific?
> Ca-P metabolism
accumulate in bones
Tc 99 -Phosphate compounds
Outline RPh for Thyroid specific?
> thyroid hormone production
Ionine (NaI)
99 Tc-eluate
Outline RPh for tumor specific ?
> accumulate in malignant tumors
99 Tc -MIBI
18 F -FDG
How does NM diagnostic devices work?
> Y rays emitted by RN incorporated in RPh
> detected from outside body by NM diagnostic devices
How does gamma cameras (SPET) work? What does SPET stand for?
SPET:
Single photon emission tomography
> detects single Y rays from Y emitting RPh (99Tc)
How does PET scan work?
What does PET stand for?
PET:
Position emission tomography
> pairs of annihilation Y rays from p+ emitting RPh (18F)
(PET) = allows Dr to check for diseases body > scan uses special dye containing radioactive tracers > tracers either swallowed, inhaled, or injected into vein
How is TH stored in TG?
stored in TG as thyroglobulin molecules
What is the regulatory control of thyroid gland?
Hypothalamic Pituitary Thyroid axis
Explain how the hypothalamic pituitary thyroid axis works?
> hypothalamus - TRH
pituitary - TSH
thyroid - T3 + T4
Which hormone stimulates secretion of T3 + T4?
thyroid stimulating hormone
Explain how thyroid hormones and TSH work as negative feedback?
> high T3 + T4 suppresses TSH secretion to maintain negative feedback loop
What happens to TSH in hyperthyroidism?
TSH is suppressed
Explain how RND is used in thyroid gland examination?
> Radioactive Iodine (NaI) used
> > thyroid function ( measures uptake of RPh)
> > thyroid anatomy (place, form, size, morphology)
** first used RN = 131 Iodine
What is thyroid scinthygraphy and why is it used?
> IMAGING: produces a visual display of thyroid based on uptake of radionuclides eg RN Iodine (NaI)
> quantitative assessment: uptake measure of RPh by TG
Outline characteristics of Iodine 131?
> beta emission > gamma emission > short half life > limited application = DTC only Differentiated Thyroid Cancer P only
