**9.9 Test case P4: intensity modulated radiation therapy (IMRT) plan with 12 coplanar beams**

For the Intensity Modulated Radiation Therapy (IMRT) with 12 coplanar beams, the percentage variation between planned dose and measured dose was noted as 1.42%.

The Dose-Difference (DD) and Distance-To-Agreement (DTA) and Gamma Index were 80.8%, 95.3%, and 98.8%, respectively.

For all the four Intensity Modulated Radiation Therapy (IMRT) plans the percentage variation between the planned dose and measured dose was found to be within the tolerance limit (< ± 3%) prescribed by International Commission on Radiation Units and Measurements (ICRU 83) [19]. Additionally, Gamma evaluation results are based on the critically acceptable criteria of 3 mm DTA and 3% DD given in **Table 3**.

### **10. Conclusion**

In radiation therapy, Quality Assurance (QA) is an essential aspect to ensure that the most accurate treatments are being delivered to a patient. When a new linear accelerator is commissioned at a hospital, the dosimetric parameters, for example, percentage depth dose, radiation beam symmetry, and flatness, are tested to verify the manufacturer's specifications and recommended guidelines. The machine is then periodically tested on a daily, monthly, and yearly basis to make sure that it remains within the specifications. This ensures that the machine continues to deliver what is indicated by a plan. For simple, traditional treatment methods, the Quality Assurance at the machine level is sufficient because possible errors are considered to be acceptable. However, for Intensity-Modulated Radiotherapy and Volumetric Modulated Arc Therapy planned treatments, the increased complexity along with high dose gradients, result in dosimetric errors and require empirical testing.

The main goal of radiation therapy is to deliver a prescribed dose to a target while minimizing the dose to the surrounding normal tissue. As new techniques are developed to achieve this goal, the treatments become more complex and the importance of having accurate dosimetry methods for both initial systems commissioning and ongoing Quality Assurance (QA) increases. Currently, it is mandatory that a patientspecific quality assurance test be performed prior to each new treatment course. Therefore, this study was conducted to develop an indigenous heterogeneous pelvic phantom similar to patient anatomy and perform a pre-treatment verification in a realistic clinical scenario to obtain reproducible dosimetry. Very few heterogeneous phantoms which are available commercially e.g. anthropomorphic phantom are very costly, and are not procured by most radiotherapy centers, especially in low-budget centers in developing countries [20].

In this study, an indigenous heterogeneous phantom was developed using wax for fat, artificial pelvic bone for pelvic bone, water for bladder, and borax powder with glue for rectum. Hounsfield unit and relative electron density of the phantom for different materials used for mimicking the patient were compared with the actual patient pelvic region. A comparison of Hounsfield Unit and electron density shows that the material used for the construction of phantom is almost equal to the *Intensity Modulated Radiation Therapy Plan (IMRT) Verification Using Indigenous… DOI: http://dx.doi.org/10.5772/intechopen.102710*

patient tissue heterogeneity as well as shape and tissue content. Materials used for the construction of phantom were locally available, cost-effective, and strong enough to maintain structural integrity.

In this study, Intensity Modulated Radiotherapy was verified using an indigenous heterogeneous pelvic phantom. For validation of heterogeneous phantom, similar plans were also verified using the Delta4 Phantom. The results obtained for all the studies were found to be within the tolerance limit which is <3% as prescribed by the International Commission of Radiation Protection (ICRU 83). This indicates that the phantom can be used successfully for routine patient-specific verification practices.

### **Author details**

Payal Raina1 \*, Rashmi Singh1 and Mithu Barthakur2

1 Department of Radiotherapy, Rajendra Institute of Medical Sciences, Ranchi, India

2 Dr. B. Borooah Cancer Institute, Guwahati, India

\*Address all correspondence to: payalraina2008@gmail.com

© 2022 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
