MOTION ENABLE IN RADIATION

VOLUMETRIC ARC THERAPY

Vs

OTHER RADIOTHERAPY TECHNIQUES.

MD PHECHUDI

OBJECTIVE INTRODUCTION

EVOLUTION OR HISTORY

DEFINITIONS

PRINCIPLES OF VARIOUS TECHNIQUES

VOLUMETRIC ARCH THERAPY

• PHYSICAL ASPECTS

• ELEKTA MACHINE

• VARIAN

COMPARISM

JOURNAL DISCUSSIONS

CONCLUSION

INTRODUCTION 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……

RADIATION SOURCES

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

Gantry motion

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

radiotherapy beams

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

treatment

PRINCIPLES 3-D CONFORMAL

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

three dimensions.

Clinicians input these selections into computer systems that

control treatment delivery.

Elith, C., et al (2011)

CONT’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

receive.

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

(DMLCs)

CONT’Stereotactic

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.

THE VMAT 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

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.

ADVANTAGES

Conformal dose distribution around

tumor

Avoidance of critical structures and

less local toxicity

Computer-generated optimization

DISADVANTAGES

Equipment costs higher

Treatment time often longer

Learning curve can be steep

Additional quality assurance

necessary

Special immobilization required

JOURNAL DISCUSSION

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)

JOURNAL DISCUSSION

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

the rectum.

Wolff, D. et al (2009)

Palma, D. et al (2008)

JOURNAL DISCUSSION

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)

SUGGESTIONS AND RECOMENDATIONS

LIST OF ILLUSTRATION

REFERENCEPasler, 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-

386

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,

no 110

REFERENCEWolff 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

REFERENCESZhang, 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