Orthovoltage X-rays
Encyclopedia
Orthovoltage X-rays are produced by X-ray generators operating at voltage
s in the 200–500 kV range, and therefore an energy
in the 200–500 keV range (see external beam radiotherapy
for an explanation of the maximum and mean energies as a function of voltage). When used to treat patients, radiation oncologist
s find that they penetrate to a useful depth of about 4–6 cm. That makes them good for treating skin
, superficial tissues, and ribs, but not for deeper structures such as lungs or pelvic organs.
Orthovoltage X-rays are sometimes termed "deep" X-rays (DXR). Historically, as radiation machines were improved in the 1930s–'40s
, the beam energy (and so its penetration) were increased. So as the new 200–500 kV beams became available, they were considered 'deep'. Now, with modern linear accelerators being able to produce X-rays of much higher energy, the penetration of orthovoltage X-rays is considered quite shallow.
By convention, the voltage is used to characterize X- and gamma-ray beams (in volts), whilst electron
beams are characterized by their energies (in electronvolts).
Voltage
Voltage, otherwise known as electrical potential difference or electric tension is the difference in electric potential between two points — or the difference in electric potential energy per unit charge between two points...
s in the 200–500 kV range, and therefore an energy
Energy
In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...
in the 200–500 keV range (see external beam radiotherapy
External beam radiotherapy
External beam radiotherapy or teletherapy is the most common form of radiotherapy. The patient sits or lies on a couch and an external source of radiation is pointed at a particular part of the body...
for an explanation of the maximum and mean energies as a function of voltage). When used to treat patients, radiation oncologist
Radiation oncologist
A radiation oncologist is a doctor who specializes in the treatment of cancer patients, using radiation therapy as the main modality of treatment. Radiation can be given as a curative modality, either alone or in combination with surgery and/or chemotherapy. It may also be used palliatively, to...
s find that they penetrate to a useful depth of about 4–6 cm. That makes them good for treating skin
Skin
-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...
, superficial tissues, and ribs, but not for deeper structures such as lungs or pelvic organs.
Orthovoltage X-rays are sometimes termed "deep" X-rays (DXR). Historically, as radiation machines were improved in the 1930s–'40s
1940s
File:1940s decade montage.png|Above title bar: events which happened during World War II : From left to right: Troops in an LCVP landing craft approaching "Omaha" Beach on "D-Day"; Adolf Hitler visits Paris, soon after the Battle of France; The Holocaust occurred during the war as Nazi Germany...
, the beam energy (and so its penetration) were increased. So as the new 200–500 kV beams became available, they were considered 'deep'. Now, with modern linear accelerators being able to produce X-rays of much higher energy, the penetration of orthovoltage X-rays is considered quite shallow.
By convention, the voltage is used to characterize X- and gamma-ray beams (in volts), whilst electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
beams are characterized by their energies (in electronvolts).