Bequerel – 1 disintergration per second (DPS)

Curie – the number of disintergrations per second per 1 gram of radium (equal to 3.7 x 1010 dps)

Half life – the amount of time required to reduce the radioactivity to ½ its present value (radioactivity is equal to activity)

ALL DISINTEGRATIONS OF RADIOACTIVE ATOMS ARE RANDOM AND INDEPENDENT EVENTS (WE DONOT KNOW WHICH ATOMS WILL UNDERGO DECAY AND WHICH WILL NOT!)

Activity Factor (Decay Constant) – is the percent reduction per unit of time

Radioactive Decay – is a property of the nucleus of an atom where there is an instability in the nucleus which is manifested by the emission of energy and/or particles

Alpha Particle – is the nucleus of a helium atom (contains 2 protons and 2 neutrons)

Atomic Number (Z) – amount of protons in the nucleus of an atom

Atomic Mass (A) – amount of protons and neutrons in the nucleus of an atom

Alpha Decay – is where 2 proton and 2 neutrons join and leave the nucleus of a atom leaving the atom less 2 protons and less 2 neutrons so the Atomic Number and the Atomic Mass are decreased by 2 each.

Beta Particle – is an electron (can be a +/- charged electron)

Beta Negative Decay – an electron is ejected from the nucleus of an atom by being released by a neutron.  So no we have an 1 more proton and 1 less neutron (since for our intents a neutrons is a electron attached to a proton).  The released electron leaves the nucleus and is considered a beta particle.

Beta Positive Decay – excess energy in the nucleus decides it doesn’t want to be energy anymore and becomes an electron and a positron.  The electron joins with a proton in the nucleus to form a neutron and the positron leaves the nucleus as a beta particle.  When the positrion comes to rest outside the nucleus it releases 2 photons each with the energy of .511 MeV that are traveling at 180 degrees from each other.

Electron Capture – electron enters the nucleus of an atom from on of the shells (most likely the K shell) and the electron will join with a proton to form a neutron.  Now from the vacancy left in the shell characteristic radiation is released.  The characteristic radiation will be that of the daughter atom formed when the proton is lost and the neutron is gained.

Fission – nucleus is bombarded by high energy particles like neutrons, their nuclei are then broken apart which then forms radioactive elements

Fusion – is the joining together of the nuclei to for a radioactive element

Neutron Capture – a neutron is absorbed into the ncleus of an atom.

Specific Activity – is the mCi of radioactivity per gram total mixture

Carrier Free – all grams of the substance are radioactive at the same time

Gross Tumor Volume (GTV) – gross palpable or visible/demonstratable extent of malignant growth

Clinical Target Volume (CTV) – includes the GTV and/or subclinical microscopic malignant disease which has to be eleiminated

Planning Tumor Volume (PTV) – includes the CTV plus an appropriate margin to take treatment uncertainties into account

Treatment Volume (TV) – minimum target dose that encloses the PTV (example would be the 90% level)

Irradiated Volume (IV) – volume of tissue that is receiving a significant dose (example 50% or greater

Treatment Planning Process : visualization, localization and simulation, field selection and placement, documentation

Primary collimators – a fixed cone shaped block of metal that defines the maximum field size (transmission of the beam through the block should only be .2% of the central axis dose)

Secondary Collimators – adjustable collimators that are designed to reduce transmission of the beam to less than 2% of the central axis dose. (tungsten alloy or lead)

Symmetric – 2 pairs of collimators that move with each other that con only produce square or rectangular field sizes

Assymentric (Independent Jaw) – each collimator moves independently

MLC – collimnator consists of 20 – 120 pairs of tungsten leaves that can be arranged to form field shapes and can be moved in IMRT treatments

Radium Needles – needles that are filled with radium chloride which are used as temporary implants.  Full activity is reached in 30 days by the radon gas produced by the radium

Uniform Linear Activity – intensity is uniform throughout the needle.  (radium needles are offered in .66mg/cm or .33mg/cm)

Indian Club – there is a lighter activity at one end of the needle

Dumbell – there is high activity at both ends but not in the center of the needle

Exposure Rate Constant (Gamma Ray Constant) – is the exposure normally measured at 1 meter from the source.  For Brachy the constant is calculated in Roentgens per hour at 1cm from a 1 mCi source.

For 1 mg of radium Exposure Rate Constant = 8.25 R cm2 / h mg or 8.25 R/hr / mCi @ 1cm  (This is for a filtered source with a .5mm platinum filter.  IMPORTANT!!! For every addition of .1mm above .5mm platiunum a 2% reduction in output occurs and must be taken into account)

Secular Equilibrium – the half life of the parent is much greater than the half life of the daughter and at equilibrium the rate at which the daughter is produced equals the rate at which the parent is decaying.

Transient Equilibrium – the parents half life is not much greater than the daughters and then after the  time required to attain equilibrium has elapsed, the activity of the daughter decreases with the apparent “half life” equal to half of the parent

RadioIsotopes:

Physical Half Life – the time it takes for ½ the initial radioactive atoms to decay (half life is not effected by temperature or pressure)

Biological Half Life – the time it takes for the body to eliminate ½ the dose of the isotope by whatever is the normal excretion process

Effective Half Life – is the combination of the physical half life and the biological half life (this is an artificial half life)

Te – is the time required for the radioactivity in the body to be reduced by ½ as a result of the combined actions of radioactive decay and biological elimination (Note: you can use a long lived physical half life if they have a very short biological half life)

Orthogonal Imaging Method – source localization method where x-rays are taken at right angles with the central axis meeting approximately in the middle of the implant.  Used for intracavitary implants such as with tandem and ovoid in the cervix

Stereo Shift Method - source localization method where 2 xrays are taken of the same view but the patient or xray tube is shifted a certain distance between the 2 exposures.  Used for seed implants where there are a large number of seeds.

CT SCAN is now used for localization of implants.

Quimby and Paris System –              Uniform placement of needles in a row, giving a non uniform dose distribution, gives a uniform distribution of radium.

Manchester System (Paterson Parker) – uniform placement of needles in a definite calculated pattern giving a nearly uniform homogeneous dose, gives the maximum homegenity of dose. (Maximum variation of dose over the treatment surface does not exceed + or – 10%)

Single Plane Implants – used if lesion is 1 cm thick

Two Plane Implants – used if the lesion measure 1 – 2.5 cm in thickeness