VMAT is a new type of intensity-modulated radiation therapy (IMRT) treatment technique that uses the same hardware (i.e. a digital linear accelerator) as used for IMRT or conformal treatment, but delivers the radiotherapy treatment using a rotational or arc geometry rather than several static beams.
This technique uses continuous modulation (i.e. moving the collimator leaves) of the multileaf collimator (MLC) fields, continuous change of the fluence rate (the intensity of the X rays) and gantry rotation speed across a single or multiple 360 degree rotations
VOLUMETRIC ARC THERAPY
OTHER RADIOTHERAPY TECHNIQUES.
EVOLUTION OR HISTORY
PRINCIPLES OF VARIOUS TECHNIQUES
VOLUMETRIC ARCH THERAPY
• PHYSICAL ASPECTS
• ELEKTA MACHINE
There are two broad categories of radiation therapy; both
are designed to target the tumor precisely while minimizing
exposure to the surrounding, healthy tissue.
In the first category, external beam radiation therapy
(EBRT), the radiation is usually delivered by a machine
called a linear accelerator, or linac.
In the second treatment category, the radiation is
delivered by radioactive material placed inside the body
near the cancer
It all started……
Early 1900 - Radium was used in various forms.
Mid 1900 – Cobalt therapy with 2-D technique
1971, 3D planning became a possibility and created a
shift from 2-D to 3-D radiation delivery
1980 Shift to IMRT technique (moving MLCs)
presently IMRT is improved to VMAT
Variable dose rate
Movement of MLCs
DEFINITIONS OF TERMS
Three-dimensional (3D) conformal radiation therapy is a
technique where the beams of radiation used in treatment are
shaped to match the tumor.
Stereotactic radiotherapy is a way of targeting
radiotherapy very precisely at the tumor, with the
Intensity-modulated radiation therapy (IMRT) is an
advanced mode of high-precision radiotherapy that uses
computer-controlled linear accelerators
VMAT is a new type of IMRT technique. The
radiotherapy machine rotates around the patient during
3-DCRT begins with virtual simulation
Virtual simulation creates a permanent digital file
Scanned images are then linked into treatment planning
software that allows physicians to visualize the treatment area in
Clinicians input these selections into computer systems that
control treatment delivery.
Elith, C., et al (2011)
Intensity Modulated Radiation Therapy
IMRT links CT scans to treatment planning software that allows the
cancerous area to be visualized in three dimensions
3DCRT and IMRT differ in how the pattern and volume of radiation
delivered to the tumor is determined.
In IMRT, the physician designates specific doses of radiation
(constraints) that the tumor and normal surrounding tissues should
A sophisticated computer program is used to develop an
individualized plan to meet the constraints.
This process is termed "inverse treatment planning“.
As a unique feature, it also involves dynamic multi-leaf collimators
SRS, or stereotactic radiosurgery, is a technique that is most commonly
used for tumors in the brain or spinal column.
Unlike IMRT, SRS is typically delivered in a maximum of five sessions
using higher doses of radiation with each session.
A focused high-intensity beam of radiation is used to target the tumor.
SBRT, or stereotactic body radiation therapy, is a very similar technique to
SRS, but is used for targets that are outside the brain and the spine.
SBRT is most commonly used for targets in the lung, liver, pancreas and
kidney, and is typically delivered in a maximum of five sessions.
VMAT is a new type of intensity-modulated radiation therapy
(IMRT) treatment technique that uses the same hardware (i.e. a
digital linear accelerator) as used for IMRT or conformal
treatment, but delivers the radiotherapy treatment using a
rotational or arc geometry rather than several static beams.
This technique uses continuous modulation (i.e. moving the
collimator leaves) of the multileaf collimator (MLC) fields,
continuous change of the fluence rate (the intensity of the X rays)
and gantry rotation speed across a single or multiple 360 degree
HOW VMAT IS PLANNED
A step-and-shoot treatment plan is created in the
treatment planning system with beams separated
by 10 degrees.
The optimized intensity maps are extracted and
sent to our arc-sequencing algorithm.
The sequencer produces a VMAT plan that is read
back to the planning system for a final
convolution/superposition dose calculation.
Conformal dose distribution around
Avoidance of critical structures and
less local toxicity
Equipment costs higher
Treatment time often longer
Learning curve can be steep
Additional quality assurance
Special immobilization required
O VMAT for node-positive left-sided breast
cancer allows the maximum doses to
organs at risk (the heart) while retaining
target homogeneity and coverage when
compared to IMRT.
Pasler, M. et al (2013)
O Two other studies conducted on 10 and 9
prostate patients treatment plans shows
VMAT being the most efficient treatment
technique with improved quality when
comparing to 3D-conformal treatments,
providing best OAR sparing especially for
Wolff, D. et al (2009)
Palma, D. et al (2008)
O Another article comparing VMAT to
stereotactic body radiotherapy (SBRT) in
15 lung cancer patients mention that
faster delivery times, better conformity to
target, sharper dose fall-off in normal
tissues and lower dose to normal lung
than the 3D plans for lung SBRT was
demonstrated VMAT plans.
Zhang, G.G et al (2011)
Pasler, M., Georg, D., Bartelt, S. & Lutterbach, J., (2013) Node-positive
left-sided breast cancer: does VMAT improve treatment plan quality with
respect to IMRT? Strahlentherapie und Onkologie, vol 5, no 189, 380-
Onal, C., Arslan, G., Parlak, C. & Sonmez S., (2014) Comparison of
IMRT and VMAT plans with different energy levels using Monte-Carlo
algorithm for prostate cancer. Jpn J Radiol, vol 1, no 32, 224–232
Alvarez-Moret, J., Pohl, F., Koelbl, O. & Dobler, B. (2010) Evaluation of
volumetric modulated arc therapy (VMAT) with Oncentra MasterPlan®
for the treatment of head and neck cancer. Radiation Oncology, Vol 5,
Wolff a, D., Stieler, F., Welzel, G., Lorenz, F., Abo-Madyan , Y., Mai, S.,
Herskind, C., Polednik, M., Steil, V., Wenz, F. & Lohr, F., (2009) Volumetric
modulated arc therapy (VMAT) vs. serial tomotherapy, step-and-shoot
IMRT and 3D-conformal RT for treatment of prostate cancer.
Radiotherapy and Oncology, vol 1, no 93, 226-233
Palma, D., Vollans, E., James, K., Nakano, S., Moiseenko, V., Shaffer,
R., Mckenzie, M., Morris, J. & Otto, K., (2008) Volumetric modulated arc
therapy for delivery of prostate radiotherapy: comparison with intensity
modulated radiotherapy and 3D-conformal radiotherapy. Radiation
Oncology, Vol. 72, No. 4, 996–1001.
Elith, C.,Dempsey, S.E.,Findlay, L.,Warren-Forward, H.M.,
(2011) An Introduction to the Intensity-modulated Radiation Therapy
(IMRT) Techniques, Tomotherapy, and VMAT. Journal of Medical
Imaging and Radiation Science,vol 1,no. 42,37-43
Zhang, G.G., Ku, L., Thomas J Dilling, T.J., Stevens, C.W., Ray R Zhang,
R.R., Li, W., & Vladimir Feygelman V., (2011) Volumetric modulated arc
planning for lung stereotactic body radiotherapy using conventional and
unflattened photon beams: a dosimetric comparison with 3D technique.
Radiation Oncology, vol 6, no 152
Huang, C., (2012) Treatment of Multiple Brain Metastases Using
Stereotactic Radiosurgery with Single-Isocenter Volumetric Modulated
Arc Therapy: Comparison with Conventional Dynamic Conformal Arc and
Static Beam Stereotactic Radiosurgery. Radiation Oncology. vol 1