Significance of TL Radiation Dosimetry of Carbon Ion Beam in Radiotherapy

Karan Kumar Gupta¹'², N.S. Dhoble³, Vijay Singh¹ and S.J. Dhoble²*

• 1 Department of Chemical Engineering, National Taiwan University, Taipei, Taiwan, ROC
• 2 Department of Physics, R.T.M. Nagpur University, Nagpur - 440033, India
• 3 Department of Chemistry, Sevadal Mahila Mahavidyalava, Nagpur - 440009, India ¹ Department of Chemical Engineering, Konkuk University, Seoul, 143701, Korea

Introduction

As it is known that radiation is a type of electromagnetic wave which can travel through vacuum or most of the matter having a different media. There are mainly two types of radiation: (1) ionizing and (2) non-ionizing. Here we are concerned only with ionizing radiations. When the ionizing radiations pass through any medium the medium gets ionized. In Radiation Therapy (RT) these high ionizing radiations are used to kill malignant tissues in the treatment of cancerous tumors. The discovery of X-ray by Roentgen in the year 1895 led to the use of photons in external beam radiotherapy (EBRT), which is a major type of treatment modality in radiotherapy. In the year 1946, Dr. Robert R. Wilson was the first person who worked on developing a particle accelerator and proposed the medical use of protons in the treatment of cancer (Wilson 1946). Proton radiotherapy is associated with some main advantages over photon radiotherapy such as deposition of a very low entrance dose and a maximum dose deposition when it reaches the target and stops, thereby eliminating an exit dose (Parker 1985). In spite of better dose distribution, the Relative Biological Effectiveness (RBE) of proton beams is slightly greater than photon beams (Eickhoff et al. 1999).Whereas the physical and biological properties of proton and heavy charged particles are quite different from each other due to high LET value of heavy charged particles. Thus, particle therapy can be further subdivided in two categories: one with proton having low LET value and another with heavy charged 'Corresponding author: This email address is being protected from spam bots, you need Javascript enabled to view it particle having high LET value (Ertner et al. 2006). Since a carbon ion beam is a type of heavy charged particle beam having LET higher than a proton, and possesses significantly increased RBE value particularly in the Bragg peak region, it becomes very popular and advantageous in the treatment of malignant tissues which lead to the double strand DNA break during its single hit to the targeted tumor (Ertner et al. 2006; Kraft 2000; Tsuji and Kamada 2012). In the treatment of cancerous tumors and other malignant tissues with ionizing radiation, it is important to measure the amount of dose (absorbed dose) delivered to the targeted area, within an uncertainty of 5% at 2o (two standard deviation) level, to reduce the risk of normal tissue complication (Pour et al. 2018). Thus with the help of a suitable dosimetry (which helps to determine the absorbed dose), we can control the radiation exposure to targeted or other areas within the patient's body.

Instead of several electronics and other dosimeters, TL dosimeter has an advantage of a small size and does not need high voltage supply, wires or cables i.e. easy to handle characteristics, which makes thermoluminescence dosimeters (TLDs) as one of the most preferred choices of detectors as a measurement of ionizing radiation in environmental and medical applications over the decades. For this purpose several TL materials (LiF:Mg, Ti; LiF:Mg, Си, P; CaS0₄:Dy etc.) are investigated (Samuel et al. 2017).

After the development of several particle accelerators, the efficacy of heavy charged particles in clinical use has been proved in radiotherapy, which leads to the investigation of proper dosimetry for HCPs (Karger et al. 2010; Bert et al. 2010). As mentioned earlier, the carbon ion beam is a type of heavy charged particle beam and these days it is mostly used in external beam radiotherapy which makes the necessity of the suitable carbon ion beam dosimetry to monitor the desired amount of dose which should be delivered to the patient. In this chapter we deal with some possible aspects that can be obtained using thermoluminescence dosimetry to measure the dose delivered to a patient in carbon radiotherapy and for this purpose we tried to develop the idea of carbon RT and its advantages over other low ionizing radiation with reference to Linear Energy Transfer (LET) and Relative Biological Effectiveness (RBE) of the carbon ion beam. To detect ionizing radiation, especially ion beam radiation with the help of the TL technique, it is important to know how ion beam radiation interacts with the TL phosphor and leads to the creation of defects inside the phosphor. Since, the TL phenomenon completely depends on the type and position of defect formation, which acts as a trapping center for electron and holes inside the TL materials, in this chapter we have tried to make a clear understanding of HCP interaction with TL materials and defect formation by the same and also the TL response of these materials with respect to another reference radiation like ⁶⁰Co or ¹³⁷Cs. However, to understand the effect of ionization density on TL response of various TL materials and relative HCP or photon TL efficiencies, we have taken help of three models/theories in this chapter as Track Structure Theory (TST), Modified Track Structure Theory (MTST) and Micro Dosimetric Target Theory (MTT). The actual problem on ion beam irradiation of TLD materials arises due to saturation effect of TL response at high fluences of the ion beam (Horowitch et al. 2001; Brandan et al. 2002; Salah 2011). Track Interaction Model (TIM), Extended Track Interaction Model (ETIM) and Unified Interaction Model (UIM) have been successfully described for explaining this saturation effect and to understand the incorporation of the trapping center, luminescence center and competitive center along the HCP track, which is responsible for the TL. To show how we can measure the carbon ion beam radiation dose with the help of the TLDs, some of the TL phosphor irradiated to different energies and at different fluences of carbon beam at ion per cm² within a certain range have been included in this chapter.

Radiotherapy

Radiotherapy is a type of medical treatment which uses high ionizing radiation to control or kill malignant cells. Thus, radiotherapy is also known as radiation therapy. Radiation therapy is commonly applied or may be curative in various types of cancerous tumors if they are localized in the body. In radiotherapy high energy beams are delivered to damage the DNA of the cancerous tissue leading to cellular death. This treatment can be used both in terms of a cure as well as to provide pain control. Radiotherapy may also be used as a part of the adjuvant therapy to reduce the risk of tumor recurrence on the area around the original cancer after surgery (Overman et al. 2010).

In radiotherapy high energy beams can also affect both cancer cells and normal tissue (such as skin or organs through which radiation must pass through to treat the cancer). To prevent normal tissue from being excessively damaged, shaped radiation beams are aimed from several angles of exposure to match the shape of the tumor located inside the patient's body, providing a much larger absorbed dose at the tumor site instead of the surroundings. Radiotherapy may be combined together with surgery, chemotherapy, immunotherapy, hormone therapy or a combination of all these four therapies. During bone marrow transplant many patients go through radiotherapy treatment which is also known as Total Body Irradiation (TBI). Total body irradiation is a technique which makes sure that body of a patient is ready to receive bone marrow or stem cell transplant. Radiation oncologists also used TBI together with high dose chemotherapy treatment to damage the cancer cells in areas (skin, bones, nervous system, and testes in men) not affected after chemotherapy. Radiotherapy can be further subdivided into two main categories known as external radiotherapy and internal radiotherapy. In external radiotherapy, the radiation source is placed outside the patient's body whereas in internal radiotherapy such as in Brachytherapy, the radiation source is sent inside the patient's body via a protective capsule or wire to the area requiring treatment (Skowronek 2017).

Radiotherapy finds its application in malignant and several non- malignant conditions such as in the treatment of acoustic neuromas or neurolemmomas (hearing loss), trigeminal neuralgia or prosopalgia (pain in the face), severe thyroid eye disease or thyroidopthalmopathy (starey eyes), pigmented villonodular synovitis etc. (Bagheri et al. 2004; Behbehani et al. 2004). It can also be used in the hindrance of keloid scar growth, heterotopic ossification (three types - Myositis ossification progressive, Traumatic myositis ossification and Neurogenic heterotopic) and vascular restenosis. However, the uses of radiation therapy in non-malignant treatment have some side effects like the risk of radiation persuaded cancer. In radiotherapy treatment, at low doses there is a minimum side effect whereas high doses can cause different types of side effects. These side effects are mainly: (1) Acute side effects like nausea and vomiting, swelling, infertility, mouth, throat and stomach sores (Eric 2000), damage to the epithelial surfaces etc.

• (2) Late side effects like cancer, heart disease (Taylor et al. 1990), dryness etc.
• (3) Cumulative side effects (Nieder et al. 2000). To overcome the side effects of high doses, different amounts of ionizing radiation in different intervals of time is used (also called Fractionation) in the course of treatment.