VMAT (RapidArc) | Volumetric Modulated Arc RadioTherapy and IMRT

VMAT, also known by the trade name RapidArc, is an advanced form of radiation therapy that delivers precise, highly targeted treatment much faster than traditional methods.

What Is VMAT?

VMAT stands for Volumetric Modulated Arc Therapy, a cutting-edge technique where radiation beams are delivered continuously as the treatment machine’s gantry rotates a full 360 degrees around the patient. This rotational delivery allows the radiation oncologist to shape and modulate the beam intensity from virtually any angle, conforming the dose tightly to the tumor while sparing healthy tissues.

How Does VMAT Work?

VMAT integrates several important technological advances:

  • Intensity Modulated Radiation Therapy (IMRT): Varies radiation intensity to focus more dose on the tumor and less on normal tissues.
  • Image-Guided Radiation Therapy (IGRT): Uses imaging before and during treatment to precisely target the tumor.
  • On-Board Imaging (OBI) and Cone Beam CT (CBCT): Provide 3D imaging of the treatment area for accurate positioning.

Why Is VMAT Better Than Older Technologies?

Traditional IMRT delivers radiation from a limited number of fixed angles—usually 5 to 7 positions—pausing at each one to deliver part of the daily dose. This limits how well the radiation can avoid sensitive normal tissue.

By contrast, VMAT delivers radiation continuously during a full rotation, adjusting the beam intensity dynamically throughout the arc. This allows for far greater flexibility in shaping the radiation dose and targeting the tumor, resulting in:

  • Less radiation exposure to healthy tissue
  • Reduced side effects
  • Highly conformal and sophisticated treatment plans

Example: VMAT for Prostate Cancer

In prostate cancer treatment, the prostate’s position can shift due to changes in bladder or rectal filling. Conventional IMRT treatments take about 10 minutes per session, increasing the chance that the prostate moves during treatment.

Because VMAT delivers radiation in 90 seconds or less, it greatly reduces the opportunity for prostate motion during delivery. This faster treatment means:

  • Improved targeting precision
  • Fewer risks of missing the tumor or hitting healthy tissue
  • Increased patient comfort due to shorter treatment times

VMAT (RapidArc) represents the next generation of radiation therapy by combining speed, precision, and flexibility. It allows your care team to deliver powerful doses of radiation quickly and safely, improving treatment outcomes while minimizing side effects.