What is VMAT treatment?
VMAT, or Volumetric Modulated Arc Therapy is an advanced radiotherapy technique combining rotation of a linear accelerator with simultaneous changes in radiation parameters to create a precise dose distribution around the tumor.
Some radiotherapy techniques deliver beams from a few fixed angles. In VMAT, the linear accelerator moves around the patient in an arc during delivery, continuously varying beam parameters.
Imagine a sculptor shaping stone from different angles. Similarly, in VMAT the machine moves around the patient, directing radiation at the target from various angles according to the treatment plan.
How does VMAT work? Precision and speed
As the machine moves, key parameters change in coordination under the treatment planning system's control.
Continuously changing angle
The linear accelerator moves around the patient in an arc during treatment.
Changing beam shape
Movable metal leaves (MLCs) inside the machine are controlled to match the radiation field shape to the treatment plan.
Changing beam intensity
Radiation intensity may also change along the machine's path to achieve the planned dose distribution more precisely.
Benefits of VMAT
The radiotherapy technique depends on the patient's condition, tumor type and location, and the care team's assessment. In appropriate cases, VMAT can offer important planning and delivery benefits.
Shorter delivery time
In many plans, VMAT can reduce radiation delivery time compared with some older techniques, shortening time on the treatment couch.
High precision
Simultaneous changes to beam angle, shape and intensity allow the care team to plan dose distribution more precisely for the target volume.
Greater attention to healthy tissue
Planning aims to deliver the appropriate dose to the tumor while reducing exposure to surrounding healthy tissues and organs.
What happens during a VMAT session?
Understanding the stages of treatment can help reduce patients' concerns and stress.
Step 1: Simulation and treatment planning
Before the main sessions, imaging with CT Simulation is performed to obtain the information needed for treatment planning.
The radiation oncologist and medical physicist identify the target volume and sensitive organs and design the treatment plan using specialist software.
Step 2: Treatment day
The patient enters the treatment room and lies on the machine's couch.
Radiotherapy technicians place the patient in the planned position. Special immobilization devices may help maintain it.
Step 3: Machine operation begins
After precise positioning, staff leave the room but continuously monitor the patient through video and audio systems.
The machine moves along its planned path without touching the patient's body and delivers radiation according to the treatment plan.
Step 4: End of the session
When delivery ends, the machine stops and the patient can leave the couch and return to daily activities as advised by the care team.
Is VMAT painful?
No. External radiation delivery is usually painless. Patients do not feel the radiation, and the machine does not touch their body.
However, side effects may occur during treatment depending on the treatment area and the patient's condition. The medical team will assess and manage them.
Answers to common questions and concerns
Will my body become radioactive after VMAT?
No. VMAT is external radiotherapy: radiation is delivered only while the machine is operating, and none remains in the body after the session.
What are the side effects of VMAT?
Side effects depend on treatment location, radiation dose, the patient's condition and other factors. Some patients may experience fatigue, skin changes or effects related to the area being treated.
Precise planning can reduce unnecessary radiation to some healthy tissues, but does not eliminate the possibility of side effects.
Do I need to hold my breath during treatment?
Most treatments do not require breath-holding, and patients can breathe normally.
Certain treatments, including some lung and breast tumors, may use breathing-motion control techniques. The care team will provide instructions before treatment begins.
Important: VMAT is selected individually according to the tumor type and location, the patient's condition, treatment goals and the specialist team's assessment.