Intensity Modulated Radiotherapy (IMRT)

What is IMRT and how does it work

Intensity Modulated Radiotherapy (IMRT) is a new technology in radiation oncology that delivers radiation more precisely to the tumor while relatively sparing the surrounding normal tissues.

IMRT is an advanced form of three-dimensional conformal radiotherapy that uses sophisticated software and hardware to vary the shape and intensity of radiation delivered to different parts of the treatment area. It is one of the most precise forms of external beam radiation therapy available.

In radiotherapy the single most important limiting factor is the normal tissue radiation tolerance, and the objective of optimal radiotherapy is to deliver the maximum radiation dose to the tumor while keeping the dose to the surrounding normal structures below tolerance.1

IMRT utilizes computer-controlled x-ray accelerators to deliver precise radiation doses to malignant tumors by modulation – or controlling – the intensity of radiation beam to focus a higher dose to the tumor while minimizing radiation exposure to surrounding normal tissues.

IMRT is a customized or individualized radiotherapy according to patient's location of tumor and anatomical structures, i.e. each patient has his or her own “unique” treatment plan.

One of its unique features is the dynamic multi-leaf collimators, which are computer-controlled devices that use up to 120 movable "leaves" to conform the radiation beam to the shape of the tumor from any angle, while protecting normal adjacent tissue as much as possible.

NMC is using the Varian Trilogy linear accelerator; the following educational video was made and released by Varian to help you understand the how IMRT and the multi-leaf collimator works.

Advantages of IMRT

  • Minimal radiation dose to healthy surrounding tissue
  • Decreased risk of harming normal cells
  • Controlled higher radiation dose to cancer cells
  • Reduced long term side effects
  • Ideal for tumors located near critical organs, i.e. tumours in the head & neck region, lung
  • Better patient comfort

[1 Woo SY, Sanders M, Grant WH et al. Does the “Peacock” have anything to do with radiation therapy? Int J Radiat Oncol Biol Phys 1994;29:213-214.]

Image Guided Radiotherapy (IGRT)

What is IGRT and how does it work

Image Guided Radiotherapy (IGRT) is a treatment technique that takes into account tumor motion. IGRT involves determining the position of the tumor every treatment session before giving any radiotherapy treatment and then altering the settings/treatment positioning if the tumor has moved.

IGRT allows changes in tumor position, size, and shape to be measured during the course of therapy, with adjustments made to maximize accuracy and precision of radiation delivery, reducing the volume of healthy tissue irradiated and permitting dose escalation to the tumor. IGRT complements IMRT during radiotherapy treatment.

What are the cancers treated with IGRT?

Tumors of the brain, head and neck is recommended as IGRT ensures that the delicate tissues, such as the spinal cord and salivary glands remain away from the high dose region.

On-Board Imager® & Respiratory Gating System

  • IGRT in combination with the On-Board Imager® & Respiratory Gating System allows more effective treatment for tumors that move due to respiratory movement, i.e. tumor in the lung
  • Gating automatically turns the treatment beam on and off at intervals synchronized with the patients' respiratory pattern, effectively freezing the moving target.
  • See how IGRT, On-Board Imager & Respiratory Gating System work together to deliver IMRT to a lung tumor
  • See how the radiation beam turns on & off depending on whether the tumor is in target or not

Advantages of IGRT

  • Enables higher degree of accuracy with the ability to ‘see’ precisely where the tumors are located during radiotherapy
  • Decrease radiation dosage to normal healthy tissues with higher ability to control the radiation beam on & off
  • Reduced effects of tumor motion during treatment

Accelerated Partial Breast Radiation (APBR)

What is Accelerated Partial Breast Radiation and how does it work

APBR delivers radiation using an external beam directly to the site where the tumor was found within a millimeter of accuracy and sparing healthy tissue.

Due to its accuracy, higher doses of radiation can be given to the tumor to shorten the treatment period from the average of six to eight weeks (for whole breast radiation) to only five days.

In many ways APBR is to current whole breast radiotherapy what a lumpectomy is to a mastectomy. The goal is to use a less invasive, more focused treatment without compromising survival.

APBR is done on an outpatient basis for highly selected patients.

Who is the Partial Breast Radiation treatment suited for?

The treatment is recommended for patients with early-stage breast cancer that has not spread to the lymph nodes & also do not have the poor prognostic features are candidates for partial breast radiation.

However, APBR is an alternative to whole breast irradiation, not a replacement. Patients must meet a long list of selection criteria to be considered suitable for accelerated partial breast irradiation including negative node status, positive ER–status, among many.

Advantages of Accelerated Partial Breast Radiation

  • Reduces radiation treatment time from the average of six to eight weeks to only four or five days
  • Increased convenience for patient who lives far from the treatment facility or women who are not able to be away from home/work for weeks
  • Completion of APBR enables patients to receive chemotherapy sooner, if appropriate
  • Also helps women with emotional closure, they can continue on with their lives after a successful treatment and put cancer behind them