The vmat vs other recent radiotherapy techniques

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

1. MOTION ENABLE IN RADIATION VOLUMETRIC ARC THERAPY Vs OTHER RADIOTHERAPY TECHNIQUES . MD PHECHUDI

2. OBJECTIVE INTRODUCTION EVOLUTION OR HISTORY DEFINITIONS PRINCIPLES OF VARIOUS TECHNIQUES VOLUMETRIC ARCH THERAPY PHYSICAL ASPECTS ELEKTA MACHINE VARIAN COMPARISM JOURNAL DISCUSSIONS CONCLUSION

3. 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

4. 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

5. 1980 Shift to IMRT technique (moving MLCs) presently IMRT is improved to VMAT Gantry motion Variable dose rate Movement of MLCs

6. 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.

7. Stereotactic radiotherapy is a way of targeting radiotherapy very precisely at the tumor, with the radiotherapy beams

8. Intensity-modulated radiation therapy (IMRT) is an advanced mode of high-precision radiotherapy that uses computer-controlled linear accelerators

9. VMAT is a new type of IMRT technique. The radiotherapy machine rotates around the patient during treatment

10. 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)

11. 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 )

12. 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.

13. 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

14. uses special software and an advanced linear accelerator to deliver IMRT treatments up to eight times faster than what was previously possible..

15. Rapid Arc can deliver the dose to the entire tumor in a single rotation — in less than two minutes.

16. 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.

17. ADVANTAGES Conformal dose distribution around tumor Avoidance of critical structures and less local toxicity Computer-generated optimization

18. DISADVANTAGES Equipment costs higher Treatment time often longer Learning curve can be steep Additional quality assurance necessary Special immobilization required

19. JOURNAL DISCUSSION 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)

20. JOURNAL DISCUSSION 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)

21. JOURNAL DISCUSSION 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)

22. SUGGESTIONS AND RECOMENDATIONS

23. LIST OF ILLUSTRATION

24. REFERENCE 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, 380-386 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

25. REFERENCE 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

26. REFERENCES 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