14 Radiotherapy Flashcards
Aims of today’s lecture
What is radiotherapy? When is it used? Procedure? Side effects The future of radiotherapy.
Radiation?
Atoms are made up of neutrons protons and electrons
Ionising radiation?
Atoms of natural radioactive substances
with unstable nuclei emit
radioactive decay
Electromagnetic waves i.e. X rays or gamma rays
alpha or ά particles (short range more damaging)
beta or particles
Many radioactive substances emit all three
Some examples of how radiation is used:?
Smoke detectors
Sterilizing medical instruments
Dating rocks and materials such as archaeological finds
Tracers for medical diagnosis
Killing cancer cells
Radiotherapy ?
The treatment of disease by ionising radiation
Radiotherapy
Ionising radiation can penetrate tissues and alter the nuclear material i.e. DNA disrupting cell growth and reproduction
Damaging human cells causing apoptosis.
When a high-energy ray hits a molecule, it can cause it to break up. This can form free radicals, which can cause further damage to the inside of the cell.
Advantage – targeted to damage cancer cells – healthy cells can recover
Used in the treatment of malignancies.
Radiotherapy
Schuster (physicist) used X-rays to treat small skin complaints (small cancers
1895 Marie Curie and husband Pierre isolated radium and characterised its properties-
suffered radiation sickness Nobel prize in 1906 (joint) 1911 (MC)
1904 Schuster together with Christie Hosp. started radium therapy – but too expensive
In 1900’s early treatment consisted of a massive dose (up to an hour duration)
major side effects
1930s It conclusively proved that fractionated therapy was just as effective as single-dose therapy, but caused fewer side effects.
“The Manchester system”
Max safe dose in a standardized way.
Radiotherapy
Alpha and gamma radiation are more likely to cause tissue or cell damage because are more effective at producing ionisation.
They are therefore the preferred treatment in comparison to beta radiation or neutrons for treating malignancies
Radiotherapy may be used :
To treat cancer as a stand alone treatment
To shrink a tumour before surgery
To reduce cancer returning after surgery
To control symptoms or to reduce pain if cancer has progressed and is no longer treatable
To reduce the growth of cells – Graves disease
Palliative radiotherapy
Specifically used to treat malignancies confined to one area
Brain Skin Prostate Breast Uterus
Types of Radiotherapy
External
Supplied from outside the body
Internal
Utilizing radioactive implants placed inside the body
Both treatment aim to be local exposure-targeting specific cells
Each exposure is termed as a fraction
External Radiotherapy
Usually given over several days or weeks Mon-Fri with the weekend off Mark target area -need to lie in a certain position Motionless ~5 min per fraction Painless procedure
Radiotherapy machine
a metal element is heated to produce electrons. These accelerate in an electric field towards a piece of tungsten metal, which then emits high-energy x-rays when they hit it”.
Conformal radiotherapy (CRT)
3D CRT
Use of metal blocks to direct the beam of ionising radiation
More closely target the shape of the tumour
Routinely used for Prostate Cancer
Internal Radiotherapy (also know as brachytherapy)
May be given once or only a few times
Usually involves a short stay in hospital
Radioactive wires or seeds (radioactive gold or Iodine) put into affected area
A few days (wires or IV)
Permanent (small amounts (seeds) of ionising radiation placed in tumour- degrade over time)
Radioactivity monitored using a Geiger counter
May have to limit contact with people
