Proton Therapy Glossary A-K

  • Active Beam
    A very precise moving proton beam. Sometimes called a "scanning beam" and refers to moving (or scanning) a proton beam across the height and width of a tumor volume. It also moves throughout the tumor's depth to "paint" the treatment volume. It does this using ionizing radiation from the beam alone or with fewer shaping aids (such as apertures and boluses).
    Active-beam technology is not yet available for patient treatments at Loma Linda University Medical Center, but is presently being used in the research room. When it is available, the proton beam therapy will permit Loma Linda University Medical Center physicians to treat more cancers, including breast cancer and larger lung cancers, with protons.

  • Aperture
    A recyclable metal block containing a hole through which the radiation (photon or proton) beam passes. Each portal for the patient requires a custom-made aperture. The lateral shape of the hole is the approximate shape of the target being treated by the beam. Every patient has her or his own set of apertures, and no other patients use them.

  • The Beam Transport System
    This system carries the beam from the accelerator to the treatment room. The system consists of several bending and focusing magnets which guide the beam around corners and focuses it to the desired spot size and location within the vacuum tube. The system monitors the size, position and intensity of the beam at many points. Variations from the prescribed parameters send messages through the computer network to adjust the beam or to trip interlocks which automatically shut it off.

  • Bolus
    A custom-made block positioned beyond the aperture. The contours and thickness of the block conform or contour the beam to the distal field-edge shape of the target. Boluses manufactured by Optivus Proton Therapy, Inc. are the only boluses on the market today that are completely recyclable.

  • Bragg Peak
    The exact point that protons (and other heavily charged particles) deposit most of their energy within the tumor site. This point occurs at the end of the protons' path and not at the entrance like traditional photon radiation therapy. By varying the beam's energy, radiation oncologists can spread this peak to match the contours of tumors or other targets.

  • Clinical or Hospital-Based Proton Therapy Center
    A proton treatment facility located in, or in close association with, a hospital or cancer center where an accelerator and treatment delivery system are used. From 1954 to 1990, all proton therapy was delivered in physics laboratories, using accelerators, mostly cyclotrons which were originally designed for basic research. The Loma Linda University Medical Center facility, which opened in 1990, was the first clinical or hospital-based proton therapy center in the world. Clinical proton therapy centers enable patients and physicians to take advantage of a variety of medical specialist's healthcare expertise, as needed.

  • Conformal Radiation Therapy
    Radiation that is shaped, or "conformed," to the shape of a tumor in all three dimensions, height, width and depth. The ability to precisely shape the beam helps the physician to deliver most of the radiation to the tumor, not to surrounding normal tissue.

  • CT Scan
    Computed tomography scan (also known as a CAT scan) is a computerized x-ray procedure. CT scan is a noninvasive, painless medical test that helps physicians diagnose and treat medical conditions. A CT scan produces cross-sectional images of internal organs, bone, soft tissue and blood vessels of the body. The images are far more detailed than x-ray films, and can reveal disease or abnormalities in tissue and bone. The procedure is usually noninvasive and brief.

  • Curie, Marie Sklodowska
    (1867 – 1934), with her husband, Pierre, was inspired to study radioactivity. Their research led in 1898 to the isolation of a new element, polonium, named after Poland, the country of Mme. Curie's birth, as well as radium. Together with her husband, she was awarded half of the Nobel Prize for Physics in 1903. She received a second Nobel Prize, this time in Chemistry, again in recognition of her work in radioactivity.

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  • Cyclotron Accelerator
    Created in 1931 for use in research laboratories and is now clinically used to treat patients. The Cyclotron uses a system of magnets and vacuum lines for transport of the beam that connects the accelerator to the treatment room. The system shapes the beam to the patients' unique treatment volume. The biggest difference between a cyclotron and a synchrotron is regarding safety. By design, cyclotrons operate at maximum energy level at all times which causes residual radiation to accumulate over time. An external degrader is used to vary the energy level since the cyclotron is fixed at 250MeV. The cyclotron uses very high intensities due to its inefficiencies and losses by the degrader. A typical cyclotron accelerator weighs 240 tons compared to a Optivus synchrotron that weighs 35 tons.

  • Dosimetrists
    People who plan and calculate the proper radiation dose for treatment. Dosimetrists work under the supervision of the physician. The physician prescribes the proper dose for treatment; the dosimetrists make sure that the prescribed dose is delivered by the therapy plan.

  • External-Beam Radiation
    Radiation delivered from a source outside the body.

  • Fixed (Stationary) Beam Delivery System
    It is a highly integrated treatment environment in which two types of beam delivery systems can be used; in both systems, the beam delivery system is fixed relative to the room. Therefore, the patient is moved relative to the beam delivery system in order to provide treatments at various angles. These beams are used for irradiating eye tumors, for central nervous system tumors and for head and neck cancers.

  • Gantry
    A large rotating device, resembling giant Ferris wheels that are used for delivering radiation around the patient during radiation therapy. This motion is designed to treat from different angles. Each gantry weighs about 90 tons and stands three stores tall. The 35-foot-diameter gantry supports the bending and focusing magnets to direct the beam and has counterweights for extra radiation shielding. The compact corkscrew gantry is a space saving configuration which minimizes the depth and space required for the gantry.

  • Image Guided Proton Therapy (IGPT)
    Image-guided proton therapy is conformal radiation treatment guided by imaging equipment, such as CT, ultrasound or stereoscopic X-rays, taken in the treatment room just before the patient is given the proton treatment. IGPT allows proton radiation to be delivered to tumors with more precision than traditional radiation treatment. IGPT minimizes the volume of healthy tissue exposed to radiation during treatment.

  • Intensity Modulated Proton Therapy (IMPT)
    Intensity Modulated Proton Therapy (IMPT) or Active Beam Scanning (ABS) extends the precision of proton radiation treatment to large, complex, irregularly shaped and multi-target volumes.  IMPT allows the intensity of the radiation to be changed during treatment, which spares more of the normal surrounding tissue. IMPT supports compensator-less treatments, variable energy controls penetration depth and is capable of continuous (raster scanning) and discrete point based (spot scanning). Optivus' IMPT system is FDA cleared.

    The scanning nozzle provides the capability to produce a small spot size and place dose throughout the treatment volume as voxels (spots) or as a swept beam. The beam begins scanning from the top down, depositing ionizing radiation from side to side. The process is repeated throughout the depth of the target volume until the entire diseased mass is treated.

  • Ionizing Radiation
    Radiation with enough energy that during an interaction with an atom, it can remove tightly bound electrons from the orbit of an atom, causing the atom to become charged or ionized. Ionized cells are damaged and must repair themselves to remain alive. Generally, normal cells are better able to repair themselves than cancer cells.

  • Immobilization Device
    A specially developed device that prevents the patient from moving during radiation treatment. One example is a form-fitting foam liner surrounded by a rigid plastic shell. The device allows the patient to lie comfortably during treatment.
    This type of immobilization is generally used for patients with tumors below the neck. Special masks or "bite blocks" are made for patients with diseases of the head or neck. Investigators in the Department of Radiation Medicine developed a vacuum-assisted bite block, which is used in many head and neck cases.

  • Intra-operative Radiation
    A type of external radiation used to deliver a single large dose of ionizing energy. The radiation is aimed directly at the tumor bed and surrounding tissue at the time of surgery.

  • Kjellberg, Raymond
    (1925 - 1993) In 1961 Raymond Kjellberg began to use protons for patient treatments at Harvard Cyclotron Laboratory. A young neurosurgeon at Massachusetts General Hospital in Boston, he became the first to use the Harvard beam to treat pituitary adenomas. Kjellberg also used the proton beam for Radiosurgery.


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