1. What is Digitally Reconstructed Radiograph (DRR)?
Based on acquired CT information, these are images that render a beam's eye view display of the treatment field anatomy and areas of treatment interest. These images resemble conventional radiographs and can be used in conjunction with patient Port Films to check patient treatment setup prior to irradiation.
A cylindrical phantom, 30 cm in diameter and 18 cm long, made of Solid Water. For patient QA, it separates into two hemispheres to place film and can have an ion chamber within 5 mm or film.
3. What is intraoperative Radiation Therapy (IORT)?
A boost technique in which a single dose of 10-20 Gy is delivered directly to the tumor bed with electrons or photons. The tumor bed has been surgically exposed, allowing critical normal structures to be shielded or displaced out of the radiation beam.
4. What is conformal Radiation Therapy?
Therapy that, with the use of 3D treatment planning, allows the delivery of higher tumor doses to selected target volume without increasing treatment morbidity. Requires a CT Simulator, 3D Treatment Planning System (TPS) and usually Multi-Leaf Collimators (MLCs) on the linear accelerator.
5. What is Electronic Portal Imaging Devices (EPID)?
A system producing near real-time portal images on a computer screen for evaluation. This is attached to the linear accelerator and is composed of amorphous Silicon (aSi) crystals. They receive MV x-rays that images the patients setup and is used to compare to the DRR's from the Treatment Planning System (TPS). These are done almost universally on all patients now.
6. What is characteristic Radiation?
Photon radiation that is emitted in discrete energies when an outer shell electron fills an inner shell position after the original inner shell electron is ionized. The binding energy difference between residing in the outer shell compared to the inner shell is the energy of the photon emitted.
7. What is Digital Imaging and Communications In Medicine (DICOM)?
A standard for handling, storing, printing, and transmitting information in medical imaging. This protocol was formed to provide communication standards for sharing image information regardless of manufacturer and has included radiation therapy treatment information. This facilitates the use of picture archival and communications systems (PACS) and allows diagnostic images to be widely distributed.
8. Do you know how Is Radiation Emitted From The Body?
The body radiates energy through thermal conduction through the skin to the air, clothes, etc, around the body. A small amount of energy would also be radiated as electromagnetic radiation with a peak wavelength directly related to the Kelvin temperature of the skin.
Also very small amounts of other radiation are emitted due to naturally occurring radioactive isotopes in the body (i.e. Carbon-14).
9. What is Intensity Modulated Radiation Therapy (IMRT)?
Therapy that delivers non-uniform exposure across the beam's eye view (BEV) rather than an open field. This type of treatment can be delivered with a machined compensator (rare outside of community clinics), linear accelerator Multi-Leaf Collimator (MLC) leaves or Tomotherapy binary leaves. The IMRT plan is usually (but not alwaysi.e. breast tangents with control points) developed with an inverse treatment planning system. While it can deliver a more conformal plan to the patient, extra care and quality checks must be done to ensure proper delivery due to its increased complexity..
10. What is clinical Target Volume (CTV)?
The visible (imaged) or palpable tumor plus any margin of subclinical disease that needs to be eliminated through the treatment planning and delivery process.
