Linear Accelerator

United Hospital has brought the most modern Linear Accelerator for Cancer Care treatment with State of the Art technology:

Intensity Modulated Radiation Therapy (IMRT)

The goal of all radiation therapy is to irradiate the tumor with a lethal dose while limiting the radiation received by the normal tissue that surrounds the tumor. IMRT uses a sophisticated dose calculation to design and deliver precisely targeted radiation. This is accomplished by using computer controlled small radiation shields in a linear accelerator. Dozens of uniquely shaped radiation fields are delivered to the patient using various angles and approaches.

The difference between 3-D conformal radiation and IMRT is that IMRT can create high dose volumes that are concave in shape, sparing critical normal issues that are extremely close to and surrounded by the tumor. During each field of treatment, the dose delivered is being modulated or adjusted by the multi-leaf collimator (a device that consists of a number of "fingers" or "leaves" which project into the primary beam to create the required shape). However, in order to spare some areas, other areas will receive more radiation. It is the job of the radiation oncologist and the radiation physicist to critically evaluate the trade-offs between avoiding normal tissues and adjusting radiation doses to the tumor.

IMRT is useful in treating small, fairly stationary targets surrounded by a large volume of normal tissue and/or critical structures that are especially close to the targeted tumor. Types of tumors that may be treated with IMRT include brain, head & neck cancer, prostate, spinal cord or tumors very close to radiosensitive normal tissues, such as the optic nerve (e.g., pituitary or nasopharyngeal cancer). Many tumors are too large or too mobile to be treated with IMRT.

Image Guided Radiation Therapy (IGRT

Image-guided radiation 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 radiation treatment.  IGRT allows radiation to be delivered to tumors with more precision than was traditionally possible. One of the challenges encountered when radiation is delivered to a tumor is that the tumor can move based on the patient's day-to-day position on the treatment table (as well as from breathing). IGRT allows the physician to better deliver the radiation dose directly to the cancer by using a variety of automated and tracking systems.  

Clinicians obtain daily high-resolution imagery to pinpoint tumor sites, adjust patient positioning when necessary, and complete a treatment, all within the standard treatment time period. By imaging the tumor daily, we can detect movement in normal structures or changes in tumor location or size which permits the physician to precisely locate the tumor while the patient is in the treatment position.  This minimizes the volume of healthy tissue exposed to radiation during treatment, yet allows the delivery of higher doses of radiation to the tumor volume.

Respiratory Gating

Improved accuracy, while avoiding damage to surrounding healthy tissue, is the goal of radiation therapy treatments. Respiratory gating is a new technology that allows the radiation treatment to be timed to an individual's breathing pattern, thus targeting the tumor only when it is in the best range for treatment. This is particularly important when treating lung and upper gastrointestinal tumors. By monitoring breathing through the treatment planning CT scans as well as treatment sessions, the radiation oncologist can choose the best moment in a patient's breathing cycle to deliver the treatment. This monitoring and compensation for tumor movement allows for tighter treatment margins so more critical structures and healthy tissue can be spared while using higher doses to treat the tumor.

The device sits on top of the patient's chest and checks for movement. The therapist can see that movement on the monitor while it records the rise and fall of the chest during breathing. The tracking mechanism of the system notifies the therapist when the patient is breathing so the beam is timed to work at the appropriate moment.


RapidArc is the biggest advance in linear accelerator radiotherapy for many years. This advanced technology unleashes the precision of the intensity-modulated radiation therapy (IMRT) two to eight times faster than was previously possible. Linear accelerators equipped with RapidArc can deliver daily treatments in a single rotation. During that rotation, a precise treatment beam continually morphs to match the shape and volume of the tumor at every possible angle. This extreme accuracy spares more normal tissue, improves clinical outcomes and reduces unwanted side effects.

Advantages of RapidArc:

  • Treatment time is dramatically reduced. It is two to ten times faster than older forms of intensity-modulated radiation therapy (IMRT).
  • Faster treatment means patients spend less time on the treatment table so they experience less discomfort and disruption.
  • RapidArc delivers precise treatments to match the tumor size and location while minimizing damage to surrounding healthy tissue.
  • With treatment completed quickly in a single gantry rotation, peripheral tissues receive a lower overall dose of radiation compared to conventional IMRT.
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