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  • Explain the concept of radiotherapy and list typical doses for cancer therapy.

Therapeutic applications of ionizing radiation, called radiation therapy or radiotherapy    , have existed since the discovery of x-rays and nuclear radioactivity. Today, radiotherapy is used almost exclusively for cancer therapy, where it saves thousands of lives and improves the quality of life and longevity of many it cannot save. Radiotherapy may be used alone or in combination with surgery and chemotherapy (drug treatment) depending on the type of cancer and the response of the patient. A careful examination of all available data has established that radiotherapy’s beneficial effects far outweigh its long-term risks.

Medical application

The earliest uses of ionizing radiation on humans were mostly harmful, with many at the level of snake oil as seen in [link] . Radium-doped cosmetics that glowed in the dark were used around the time of World War I. As recently as the 1950s, radon mine tours were promoted as healthful and rejuvenating—those who toured were exposed but gained no benefits. Radium salts were sold as health elixirs for many years. The gruesome death of a wealthy industrialist, who became psychologically addicted to the brew, alerted the unsuspecting to the dangers of radium salt elixirs. Most abuses finally ended after the legislation in the 1950s.

The image shows an old advertisement of radium material branded as UNDARK with the tagline “Shines in the Dark.”
The properties of radiation were once touted for far more than its modern use in cancer therapy. Until 1932, radium was advertised for a variety of uses, often with tragic results. (credit: Struthious Bandersnatch.)

Radiotherapy is effective against cancer because cancer cells reproduce rapidly and, consequently, are more sensitive to radiation. The central problem in radiotherapy is to make the dose for cancer cells as high as possible while limiting the dose for normal cells. The ratio of abnormal cells killed to normal cells killed is called the therapeutic ratio    , and all radiotherapy techniques are designed to enhance this ratio. Radiation can be concentrated in cancerous tissue by a number of techniques. One of the most prevalent techniques for well-defined tumors is a geometric technique shown in [link] . A narrow beam of radiation is passed through the patient from a variety of directions with a common crossing point in the tumor. This concentrates the dose in the tumor while spreading it out over a large volume of normal tissue. The external radiation can be x-rays, 60 Co  γ rays, or ionizing-particle beams produced by accelerators. Accelerator-produced beams of neutrons, π-mesons , and heavy ions such as nitrogen nuclei have been employed, and these can be quite effective. These particles have larger QFs or RBEs and sometimes can be better localized, producing a greater therapeutic ratio. But accelerator radiotherapy is much more expensive and less frequently employed than other forms.

The image shows a man lying on a flat surface. A gamma ray machine is rotated around the man.
The 60 Co source of γ -radiation is rotated around the patient so that the common crossing point is in the tumor, concentrating the dose there. This geometric technique works for well-defined tumors.

Questions & Answers

Calculate the work done by an 85.0-kg man who pushes a crate 4.00 m up along a ramp that makes an angle of 20.0º20.0º with the horizontal. (See [link] .) He exerts a force of 500 N on the crate parallel to the ramp and moves at a constant speed. Be certain to include the work he does on the crate an
Collins Reply
What is thermal heat all about
Abel Reply
why uniform circular motion is called a periodic motion?.
Boniface Reply
when a train start from A & it returns at same station A . what is its acceleration?
Mwdan Reply
what is distance of A to B of the stations and what is the time taken to reach B from A
the information provided is not enough
Hmmmm maybe the question is logical
where are the parameters for calculation
there is enough information to calculate an AVERAGE acceleration
mistake, there is enough information to calculate an average velocity
what is the unit of momentum
wha are the types of radioactivity ?
Worku Reply
what are the types of radioactivity
what is static friction
Golu Reply
It is the opposite of kinetic friction
static fiction is friction between two surfaces in contact an none of sliding over on another, while Kinetic friction is friction between sliding surfaces in contact.
I don't get it,if it's static then there will be no friction.
It means that static friction is that friction that most be overcome before a body can move
static friction is a force that keeps an object from moving, and it's the opposite of kinetic friction.
It is a force a body must overcome in order for the body to move.
If a particle accelerator explodes what happens
why we see the edge effect in case of the field lines of capacitor?
what is wave
Muhammed Reply
what is force
force is something which is responsible for the object to change its position
more technically it is the product of mass of an object and Acceleration produced in it
wave is disturbance in any medium
energy is distributed in any medium through particles of medium.
If a particle accelerator explodes what happens
Eboh Reply
we have to first figure out .... wats a particle accelerator first
What is surface tension
Subi Reply
The resistive force of surface.
Who can tutor me on simple harmonic motion
yusuf Reply
on both a string and peldulum?
Do you have a chit-chat contact
I dont have social media but i do have an email?
Which is
Where are you chatting from
I don't understand the basics of this group
teach him SHM init
Simple harmonic motion
how.an.equipotential.line is two dimension and equipotential surface is three dimension ?
syed Reply
definition of mass of conversion
umezurike Reply
Force equals mass time acceleration. Weight is a force and it can replace force in the equation. The acceleration would be gravity, which is an acceleration. To change from weight to mass divide by gravity (9.8 m/s^2).
how many subject is in physics
Adeshina Reply
the write question should be " How many Topics are in O- Level Physics, or other branches of physics.
how many topic are in physics
Praise what level are you
If u are doing a levels in your first year you do AS topics therefore you do 5 big topic i.e particles radiation, waves and optics, mechanics,materials, electricity. After that you do A level topics like Specific Harmonic motion circular motion astrophysics depends really
Yeah basics of physics prin8
Heat nd Co for a level
yh I need someone to explain something im tryna solve . I'll send the question if u down for it
Tamdy Reply
a ripple tank experiment a vibrating plane is used to generate wrinkles in the water .if the distance between two successive point is 3.5cm and the wave travel a distance of 31.5cm find the frequency of the vibration
please send the answer
the range of objects and phenomena studied in physics is
Bethel Reply
I don't know please give the answer
Practice Key Terms 2

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Source:  OpenStax, College physics. OpenStax CNX. Jul 27, 2015 Download for free at http://legacy.cnx.org/content/col11406/1.9
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