Isocenter definition in Radiotherapy:
The point in space relative to the treatment machine about which various components of the linac rotate
. The gantry rotation defines a horizontal axis which cuts a vertical axis defined by the rotation of the treatment couch.
What is an isocenter in radiotherapy?
Isocenter definition in Radiotherapy:
The point in space relative to the treatment machine about which various components of the linac rotate
. The gantry rotation defines a horizontal axis which cuts a vertical axis defined by the rotation of the treatment couch.
What is isocenter in linac?
The linac mechanical isocenter (linac isocenter) is defined as
the center of a circle that best fits the trajectory of a select linac X-ray source position
. The axis of rotation and the minimal bounding sphere are cornerstones for the rotation isocenters of the collimator, gantry and couch.
What is the purpose of Isocentric positioning?
An isocentric technique is where
all beams used in a radiation treatment have a common focus point
, a.k.a. the isocenter. Isocentric techniques require less patient repositioning as multiple field arrangements can be delivered with gantry and collimator movements, reducing treatment times.
What is SSD and sad technique in radiotherapy?
Modern photon beam radiotherapy is carried out with a variety of beam energies and field sizes under one of two set-up conventions: a
constant source to surface distance (SSD) for all beams
or an isocentric set-up with a constant source to axis distance (SAD).
What is the radiation therapy called before surgery?
To cure or shrink early-stage cancer
For other cancers, radiation may be used before surgery to shrink the tumor (this is called
pre-operative therapy or neoadjuvant therapy
), or after surgery to help keep the cancer from coming back (called adjuvant therapy).
What type of radiation is IMRT?
Intensity-modulated radiation therapy (IMRT) is an
advanced type of radiation therapy
used to treat cancer and noncancerous tumors. IMRT uses advanced technology to manipulate photon and proton beams of radiation to conform to the shape of a tumor.
What is Linac machine?
A
medical linear accelerator
(LINAC) is the device most commonly used for external beam radiation treatments for patients with cancer. It delivers high-energy x-rays or electrons to the region of the patient’s tumor.
What is meant by isocenter?
:
the point on an aerial photograph intersected by the bisector of the angle between the plumb line and the perpendicular to the photograph
.
What is Winston Lutz test?
The Winston-Lutz (WL) test is
a commonly used method to localize the isocenter of a linear
.
accelerator (linac) in radiation therapy
.(1) Compared with other methods, such as room lasers. and light field crosshairs, the WL test correlates the radiation fields directly with the object being.
What can radiotherapy be used for?
Radiation therapy (also called radiotherapy) is a cancer treatment that uses
high doses of radiation to kill cancer cells and shrink tumors
. At low doses, radiation is used in x-rays to see inside your body, as with x-rays of your teeth or broken bones.
What is field size in radiotherapy?
at the center of the front surface of the radiation source. The dosimetric, or the physical, field size is
the distance
.
intercepted by a given isodose curve (usually 50% isodose) on a plane perpendicular to the beam axis at a stated
.
distance
such as the SSD or the source‐axis distance.
What is box technique in radiotherapy?
Using the four field or “box technique” (opposing AP and lateral fields) in irradiating the pelvis,
one can reduce the dose to the bladder and rectum while unavoidably irradiating the femurs
.
Does radiation shorten your life?
“Rapidly dividing cells, such as cancer cells, are
more affected
by radiation therapy than normal cells. The body may respond to this damage with fibrosis or scarring, though this is generally a mild process and typically does not cause any long-term problems that substantially affect quality of life.”
Is chemo worse than radiation?
The radiation beams change the DNA makeup of the tumor, causing it to shrink or die. This type of cancer treatment
has fewer side effects than chemotherapy
since it only targets one area of the body.
What happens if I refuse radiation treatment?
Patients who refuse recommended adjuvant radiation therapy have
unacceptably high rates of local recurrence
. Omission of radiation for advanced age alone is associated with local recurrence rates comparable to those for younger patients.
