Radiation Oncology_ A MCQ and Case Study-Based Review.pdf

1 Radiation Physics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1 Test 1.1A. Radiation Physics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Test 1.1A. Explanatory Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.3 Test 1.2A. Radiation Physics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 1.4 Test 1.2A. Explanatory Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 1.5 Test 1.3A. Radiation Physics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 1.6 Test 1.3A. Explanatory Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 1.7 Test 1.4A. Radiation Physics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 1.8 Test 1.4A. Explanatory Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 1.9 Test 1.5A. Radiation Physics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 1.10 Test 1.5A. Explanatory Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 1.11 Test 1.6A. Radiation Physics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 1.12 Test 1.6A. Explanatory Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 1.13 Test 1.7A. Radiation Physics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 1.14 Test 1.7A. Explanatory Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 1.15 Test 1.1B. Radiation Physics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 1.16 Test 1.2B. Radiation Physics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 1.17 Test 1.3B. Radiation Physics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 1.18 Test 1.4B. Radiation Physics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 1.19 Test 1.5B. Radiation Physics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 1.20 Test 1.6B. Radiation Physics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 1.21 Test 1.7B. Radiation Physics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 1.22 Answer Key to Chapter 1. Radiation Physics . . . . . . . . . . . . . . . . . . 67 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 2 Radiobiology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 2.1 Test 2.1A. Radiobiology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 2.2 Test 2.1A. Explanatory Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 2.3 Test 2.2A. Radiobiology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 2.4 Test 2.2A. Explanatory Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 2.5 Test 2.3A. Radiobiology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 2.6 Test 2.3A. Explanatory Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 2.7 Test 2.4A. Radiobiology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 2.8 Test 2.4A. Explanatory Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 xii Contents 2.9 Test 5A. Radiobiology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118 2.10 Test 5A. Explanatory Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120 2.11 Test 2.1B. Radiobiology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 2.12 Test 2.2B. Radiobiology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 2.13 Test 2.3B. Radiobiology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 2.14 Test 2.4B. Radiobiology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128 2.15 Test 2.5B. Radiobiology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130 2.16 Answer Key to Chapter 2. Radiation Biology . . . . . . . . . . . . . . . . . . 132 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 3 Clinical Radiation Oncology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 3.1 Test 3.1A. Clinical Radiation Oncology . . . . . . . . . . . . . . . . . . . . . . 137 3.2 Test 3.1A. Explanatory Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 3.3 Test 3.2A. Clinical Radiation Oncology . . . . . . . . . . . . . . . . . . . . . . 146 3.4 Test 3.2A. Explanatory Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148 3.5 Test 3.1B. Clinical Radiation Oncology . . . . . . . . . . . . . . . . . . . . . . 154 3.6 Test 3.2B. Clinical Radiation Oncology . . . . . . . . . . . . . . . . . . . . . . 157 3.7 Answer Key to Chapter 3. Clinical Radiation Oncology . . . . . . . . . . 159 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159 4 Central Nervous System Tumors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161 4.1 Test 4.1. Central Nervous System Tumors . . . . . . . . . . . . . . . . . . . . . 161 4.2 Test 4.1. Explanatory Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 4.3 Test 4.2. Central Nervous System Tumors . . . . . . . . . . . . . . . . . . . . . 172 4.4 Test 4.2. Explanatory Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174 4.5 Answer Key to Chapter 4. Central Nervous System Tumors. . . . . . . 177 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184 5 Head and Neck Cancers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 5.1 Test 5.1. Nasopharynx . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 5.2 Test 5.1. Explanatory Answers – Nasopharynx . . . . . . . . . . . . . . . . . 188 5.3 Test 5.2. Oropharynx . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194 5.4 Test 5.2. Explanatory Answers – Oropharynx . . . . . . . . . . . . . . . . . . 196 5.5 Test 5.3. Hypopharyx . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200 5.6 Test 5.3. Explanatory Answers – Hypopharynx . . . . . . . . . . . . . . . . 200 5.7 Test 5.4. Larynx . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205 5.8 Test 5.4. Explanatory Answers – Larynx . . . . . . . . . . . . . . . . . . . . . . 206 5.9 Test 5.5. Oral Cavity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212 5.10 Test 5.5. Explanatory Answers – Oral Cavity . . . . . . . . . . . . . . . . . . 213 5.11 Test 5.6. Sinonasal Cancer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216 5.12 Test 5.6. Explanatory Answers – Sinonasal Cancer. . . . . . . . . . . . . . 217 5.13 Test 5.7. Salivary Gland Tumors . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223 5.14 Test 5.7. Explanatory Answers – Salivary Gland Tumors . . . . . . . . . 224 5.15 Test 5.8. Thyroid Cancer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228 Contents xiii 5.16 Test 5.8. Explanatory Answers – Thyroid Cancer . . . . . . . . . . . . . . . 229 5.17 Test 5.9. General Head and Neck Cancer . . . . . . . . . . . . . . . . . . . . . 232 5.18 Test 5.9. Explanatory Answers – General Head and Neck Cancer . . 233 5.19 Answer Key to Chapter 5. Head and Neck Cancers . . . . . . . . . . . . . 238 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247 6 Lung Cancer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251 6.1 Test 6.1. Non-Small Cell Lung Cancer . . . . . . . . . . . . . . . . . . . . . . . 251 6.2 Test 6.1. Explanatory Answers – Non Small Cell Lung Cancer . . . . 253 6.3 Test 6.2. Small Cell Lung Cancer . . . . . . . . . . . . . . . . . . . . . . . . . . . 259 6.4 Test 6.2. Explanatory Answers – Small Cell Lung Cancer . . . . . . . . 260 6.5 Answer Key to Chapter 6. Lung Cancer . . . . . . . . . . . . . . . . . . . . . . 262 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265 7 Breast Cancer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269 7.1 Test 7.1. Breast Cancer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269 7.2 Test 7.1. Explanatory Answers – Breast Cancer . . . . . . . . . . . . . . . . 272 7.3 Answer Key to Chapter 7. Breast Cancer . . . . . . . . . . . . . . . . . . . . . 285 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289 8 Genitourinary System Cancers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291 8.1 Test 8.1. Prostate Cancer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291 8.2 Test 8.1. Explanatory Answers – Prostate Cancer . . . . . . . . . . . . . . . 293 8.3 Test 8.2. Testicular Cancers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303 8.4 Test 8.2. Explanatory Answers – Testicular Cancer . . . . . . . . . . . . . 305 8.5 Test 8.3. Bladder Cancer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313 8.6 Test 8.3. Explanatory Answers – Bladder Cancer . . . . . . . . . . . . . . . 314 8.7 Answer Key to Chapter 8. Genitourinary System Cancer . . . . . . . . . 318 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321 9 Gynecological Cancers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325 9.1 Test 9.1. Cervix Cancer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325 9.2 Test 9.1. Explanatory Answers – Cervix Cancer . . . . . . . . . . . . . . . . 328 9.3 Test 9.2. Endometrial Cancer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336 9.4 Test 9.2. Explanatory Answers – Endometrial Cancer . . . . . . . . . . . 338 9.5 Test 9.3. Vaginal Cancer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345 9.6 Test 9.3. Explanatory Answers – Vaginal Cancer . . . . . . . . . . . . . . . 346 9.7 Answer Key to Chapter 9. Gynecological Cancer . . . . . . . . . . . . . . . 350 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354 10 Gastrointestinal System Cancers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357 10.1 Test 10.1. Esophageal Cancer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357 10.2 Test 10.1. Explanatory Answers – Esophagueal Cancer . . . . . . . . . 358 10.3 Test 10.2. Gastric Cancer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365 xiv Contents 10.4 Test 10.2. Explanatory Answers – Gastric Cancer . . . . . . . . . . . . . . 367 10.5 Test 10.3. Pancreatic Cancer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374 10.6 Test 10.3. Explanatory Answers – Pancreatic Cancer . . . . . . . . . . . 376 10.7 Test 10.4. Rectal Cancer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 381 10.8 Test 10.4. Explanatory Answers – Rectal Cancer . . . . . . . . . . . . . . 383 10.9 Test 10.5. Anal Cancer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 388 10.10 Test 10.5. Explanatory Answers – Anal Cancer . . . . . . . . . . . . . . . 389 10.11 Answer Key to Chapter 10. Gastrointestinal System Cancers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 403 11 Soft Tissue Sarcoma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 407 11.1 Test 11.1. Soft Tissue Sarcoma . . . . . . . . . . . . . . . . . . . . . . . . . . . . 407 11.2 Test 11.1. Explanatory Answers – Soft Tissue Sarcoma . . . . . . . . . 410 11.3 Answer Key to Chapter 11. Soft Tissue Sarcoma . . . . . . . . . . . . . . 416 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 418 12 Skin Cancer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 419 12.1 Test 12.1. Skin Cancer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 419 12.2 Test 12.1. Explanatory Answers – Skin Cancer . . . . . . . . . . . . . . . . 421 12.3 Answer Key to Chapter 12. Skin Cancer . . . . . . . . . . . . . . . . . . . . . 426 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 428 13 Lymphomas and Total Body Irradiation . . . . . . . . . . . . . . . . . . . . . . . . 429 13.1 Test 13.1 Hodgkin’s Lymphoma . . . . . . . . . . . . . . . . . . . . . . . . . . . 429 13.2 Test 13.1. Explanatory Answers – Hodgkin’s Lymphoma . . . . . . . . 431 13.3 Test 13.2. Non-Hodgkin’s Lymphoma . . . . . . . . . . . . . . . . . . . . . . . 440 13.4 Test 13.2-Explanatory Answers – Non-Hodgkin’s lymphoma . . . . 441 13.5 Test 13.3. Total Body Irradiation . . . . . . . . . . . . . . . . . . . . . . . . . . . 447 13.6 Test 13.3. Explanatory Answers – Total Body Irradiation . . . . . . . . 448 13.7 Answer Key to Chapter 13. Lymphomas and Total Body Irradiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 451 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 455 14 Pediatric Tumors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 459 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 471 15 Rare Tumors and Benign Diseases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 475 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 484 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 487 M. Beyzadeoglu et al., Radiation Oncology, 1 DOI 10.1007/978-3-642-27988-1_1, © Springer-Verlag Berlin Heidelberg 2012 1.1 Test 1.1A. Radiation Physics 1. Which of the following statements about the structure of the atom is false ? (a) Electrons are negatively charged and the lightest particle among the triad of protons, neutrons, and electrons. (b) Protons are positively charged, with a mass about 1,839 times higher than that of electrons. (c) The total number of nucleons is called the atomic number and symbolized by “Z.” (d) Protons and neutrons form the nucleus of the atom. (e) The total number of protons and neutrons in a nucleus is defi ned as the mass number of that atom. 2. Which of the following statements concerning radiation is false ? (a) The propagation of energy through a medium is called radiation. (b) The transmission of energy with radiation can be either in the form of particulate or electromagnetic (EM) radiation. (c) The photon is the smallest unit of EM radiation . (d) Photons have no mass and propagate through space with the speed of light. (e) Radio waves with the shortest wavelength with the highest frequency and energy are located on one side, whereas x- and gamma rays with lower frequency and energy are situated on the other side of the EM spectrum. 3. Which of the following is not a feature of electromagnetic (EM) radiation? (a) The speed of EM radiation is equal to the speed of light. (b) The amount of energy transferred by EM radiation correlates positively with the frequency and negatively with the wavelength of the radiation. (c) The energy of EM radiation decreases as it passes through a material because of absorption and scattering. (d) The energy of EM radiation decreases with a positive correlation of the square of distance in space. (e) The lowest energy of ionizing EM radiation is 12 eV. 1 Radiation Physics Murat Beyzadeoglu , Gokhan Ozyigit , and Ugur Selek 2 1 Radiation Physics 4. What is the mean energy transferred during the ionization process? (a) 14 eV (b) 24 eV (c) 34 eV (d) 44 eV (e) 54 eV 5. Which of the following statements concerning x-ray tubes is false ? (a) Electrons produced by thermionic emission in the cathode are accelerated towards the anode by the potential. (b) The anode is composed of a metal with a high melting temperature such as tungsten. (c) X-rays are mostly produced by the sudden deceleration of electrons by the bremsstrahlung process. (d) The energy and the wavelength of x-rays depend on the atomic number of the target metal, as well as the velocity and the kinetic energy gained by electrons. (e) Characteristic x-rays are used in the production of medical radiation in diagnostic x-ray units, linear accelerators, and betatrons. 6. Which of the following is not a feature of gamma rays? (a) Gamma rays are physically identical to x-rays. (b) Gamma rays have well-defi ned energies. (c) Two monoenergetic gamma rays with a mean energy of 1.25 MeV (1.17 MeV and 1.33 MeV) are emitted during the decay of Co-60. (d) Gamma rays consist of subatomic particles. (e) The speed of gamma rays is equal to the speed of light. 7. Which of the following statements is false ? (a) The half-life of a radioisotope is the time interval required for the decay of its activity to half of its initial radioactivity. (b) The activity of a radioisotope is the number of decays per second; its unit is the curie. (c) The decay of a radioactive nucleus is not a spontaneous process, but requires energy. (d) Gamma decay is decay without any change in the form of the nucleus from an excited form to its basal state. (e) Alpha or beta particles are emitted during the alpha and beta decays of an unstable nucleus to reach a stable nucleus. 8. Which of the following is true for alpha decay? (a) An alpha particle consisting of one proton and one neutron is emitted if the instability of the nucleus is due to the excess amount of both electrons and neutrons. (b) Most of the energy after alpha decay is taken by the alpha particle, which has a smaller mass, because of the law of momentum conservation. (c) Although the 4 2He nucleus has high energy, its range is long because of its light mass. (d) Alpha decay is usually observed in a nucleus with a mass number less than 190. (e) Its energy spectrum is continuous and barely interacts with the electrons of matter that it passes through. 1.2 Test 1.1A. Explanatory Answers 3 9. One of the neutrons transforms into a proton and an electron to give an excess amount of energy in its nucleus. This type of decay is called : (a) Gamma emission (b) β − decay (c) β + decay (d) Electron capture phenomenon (e) Alpha decay 10. 12 12 12 56 7 BC N , , and are called : (a) Isotopes (b) Isotones (c) Isobars (d) Isomers (e) Nucleons 1.2 Test 1.1A. Explanatory Answers 1. The answer is c [ 42 ] . The electron is negatively charged and is the lightest particle among the triad of protons, neutrons, and electrons. Protons are positively charged, and their mass is about 1,839 times higher than that of electrons. Neutrons are neutral, and their mass is nearly 1,839 times higher than that of electrons. Protons and neutrons form the nucleus of the atom, and these particles are also called nucleons. The total number of protons and neutrons in a nucleus (p + n) (i.e., the total number of nucleons) is defi ned as the mass number of that atom and is symbolized by A [ 1 ] . 2. The answer is e [ 42 ] . The propagation of energy from a source to the medium is called radiation. This transmission of energy can be either in the form of particulate or electromagnetic radiation. The various forms of energy originating from the atoms are called electromagnetic radiation [ 1 ] . Radiation including visible light as well as x- and gamma rays makes the electromagnetic radiation spectrum [ 1, 2 ] . Radio waves with the longest wavelength with the lowest frequency and energy are located on the one side, whereas x- and gamma rays with higher frequency and energy are situated on the other side of this spectrum. The photon is the smallest unit of electromagnetic radiation [ 3 ] . Photons have no mass and propagate through space at the speed of light. 3. The answer is d [ 42 ] . The common features of electromagnetic radiation are [ 4 , 5 , 6 , 7 ] : • They propagate in a straight line in the space. • Their speed is equal to the speed of light (nearly 300,000 km/s). Nuclide→ If an atom is expressed as A Z X , it is called a nuclide (e.g., 4 2He ). Radionuclide → If the atom that is expressed as A Z X has radioactivity, it is called a radionuclide. 4 1 Radiation Physics • They transfer energy to the medium that they passed through with a positive correlation of their frequencies and with a negative correlation of their wavelengths. • Their energy, when they pass through a material, decreases because of absorption and scattering, with a negative correlation of the square of distance in space. 4. The answer is c [ 42 ] . Electrons are knocked out of their atomic and molecular orbits (a process known as ionization) when high-energy radiation interacts with matter [ 8 ] . Those electrons produce secondary electrons during their passage through the material. A mean energy of 33.85 eV is transferred during the ionization process, which in atomic and molecular terms is a highly signifi cant amount of energy. 5. The answer is e [ 42 ] . Electrons produced by thermoionic emission in the cathode are accelerated toward the anode by the potential. They thus hit the anode, which is a metal with a high melting temperature. X-rays are produced by extranuclear procedures. Two kinds of x-rays are created by x-ray tubes [ 9 , 10 , 11 ] . Bremsstrahlung x-rays occur by the interaction of electrons with the nucleus, resulting in sudden deceleration. Bremsstrahlung x-rays are used to produce medical radiation in diagnostic x-ray units, linear accelerators, and betatrons. The characteristics x-rays arise from the removal of inner orbital electrons by the incoming electrons, and the resulting space is fi lled with other electrons coming from the outer orbit. The energy released during this displacement of outer orbital electrons generates the characteristic x-rays [ 12 ] . It is called characteristic because its energy depends on the specifi c target metal that the electrons hit. 6. The answer is d [ 42 ] . Gamma rays are physically identical to x-rays; however, they are emitted from the atomic nucleus (intranuclearly). An unstable atomic nucleus gives its excess energy either in the form of an intranuclear electron (e − ) (beta particle) or as a helium nucleus (alpha particle; Fig. 1.1 ). It still has excess energy, and gamma rays are emitted to reach a steady state (Fig. 1.2 ). Gamma rays have well-defi ned energies. For instance, two monoenergetic gamma rays with a mean energy of 1.25 MeV (1.17 MeV and 1.33 MeV) following beta rays of 0.31 MeV energy are emitted during the decay of 60 Co (cobalt). They transform into the fi nal stable decay product of 60 Ni (nickel). The cobalt element actually has a stable nucleus in nature, shown as 59 Co. However, 60 Co is made up by the neutron bombardment in nuclear reactors. 60 Co has a half-life of 5.26 years, and 1 g of 60 Co has 50 Ci (1.85 terabecquerel) of radioactivity [ 13, 14 ] . Electromagnetic radiation is also subdivided into two categories: ionizing and nonionizing radiation. Nonionizing radiation has a wavelength of equal to or greater than 10 −7 m. The energy of nonionizing radiations is less than 12 electron volts (eV), and it is accepted as the lowest energy of ionizing radiation [ 4 ] . 1.2 Test 1.1A. Explanatory Answers 5 7. The answer is c [ 42 ] . The half-life of a radioisotope is the time interval required for the decay of its activity to half of its initial radioactivity [ 15 ] . The activity of a radioisotope is the amount of decay per second, defi ned as Becquerel or curie. The decay of the radioactive nucleus is a spontaneous process. There are three forms of radioactive decay. Alpha or beta particles are emitted during the alpha and beta decays of an unstable nucleus to reach a stable nucleus. Gamma decay is the decay without any change in the form of the nucleus from an excited form to its basal state. 8. The answer is b . Alpha decay [ 16 ] : An alpha particle consisting of two protons and two neutrons is emitted if the instability of the nucleus is due to the excess amount of both protons and neutrons (Fig. 1.3 ). Most of the energy after alpha decay is taken by the alpha particle, which has a smaller mass, due the law of momentum conservation. Although the 4 2He nucleus has high energy, its range is short because of its heavy mass. Alpha decay is usually observed in the nucleus with a mass number of more than 190. Its energy spectrum is not continuous and varies between 4 and 10 MeV. It densely interacts with the electrons of matter that it passes through because it is a charged particle. Alpha particle (Helium nucleus) Spontaneous radiation Unstable nucleus Gamma rays Beta particle (Electron) Fig. 1.1 Alpha particles [ 42 ] • Becquerel (Bq): The current activity unit. It represents 1 disintegration (decay) per second. • 1 curie (Ci) = 3.7 × 10 10 disintegrations/s. 27Co60 28Ni601.17 MeV γ 1.33 MeV γ 0.31 MeV β Fig. 1.2 Co-60 decay [ 42 ] 6 1 Radiation Physics 9. The answer is b . Carbon-14 Nitrogen-14 Antineutrino Electron 6 protons 8 neutrons 7 protons 7 neutrons ν − − β- Fig. 1.4 β − decay [ 42 ] Beta decay [ 17 ] : There are three types of beta decay. β − Decay : If the instability of a radionuclide is due to the excess amount of neutrons in its nucleus, it transforms one of the neutrons into a proton and an electron to give an excess amount of energy in its nucleus (Fig. 1.4 ). The electron is rapidly propelled out, while the proton stays in the nucleus. This highspeed electron is called a b − particle, or negatron. The atomic number of the radionuclide, which decays with this type of beta emission, increases to +1 and becomes the isobar of the next element. This decay is also called isobaric decay since the mass number does not change [ 16, 17 ] . Large, unstable nucleus Smaller, more stable nucleus Alpha particle Fig. 1.3 Alpha decay [ 42 ] β + Decay [ 17 ] : If the instability of the atom is due to the excess number of protons or the lack of neutrons, one of the protons transforms into one neutron and a positively charged electron (positron). The neutron stays in the nucleus, while the positron is propelled out (Fig. 1.5 ). Thus, the proton number (atomic number) of the radionuclide that emits the positron decreases by 1 and becomes the isobaric atom of the preceding element. However, its mass number does not change. 1.2 Test 1.1A. Explanatory Answers 7 Carbon-10 Boron-10 6 protons 4 neutrons 5 protons 5 neutrons ν β+ + Neutrino Positron Fig. 1.5 β+ decay [ 42 ] Fig. 1.6 Electron capture phenomenon [ 42 ] . The mass number is constant in all three types of beta decay, whereas the number of protons and neutrons changes by one unit. Furthermore, the emission of some particles with no mass and no charge, called neutrinos or antineutrinos, is observed in each beta decay process. The existence of these particles was fi rst suggested by Pauli in 1930, and then Fermi called these particles neutrinos [ 16 ] . Carbon-11 Electron 6 protons 5 neutrons 5 protons 6 neutrons Boron-11 Neutrino - v Electron Capture Phenomenon [ 16 ] : If the nucleus is unstable because of the excess number of protons, one of the electrons close to the atomic nucleus such as in the K and L orbits is captured by the nucleus (Fig. 1.6 ). After that the electron combines with one proton and becomes one neutron and one neutrino. In this type of decay, no particle is emitted from the nucleus, but the proton number decreases 1 like in positron decay. However, the mass number does not change. The space of the electron is fi lled with outer orbital electrons, and characteristic x-rays are emitted during this process. Gamma Emission [ 13, 14, 16 ] : The atom cannot always have a stable state (basal energy level) just after the emission of radiation either because of the excess energy in the nucleus or the nuclide decay process, and the radionuclide after decay can be in a half-stable state (Fig. 1.7 ). This excited energy excess is emitted in the electromagnetic form of gamma radiation. There is no change in the atomic or mass number of the half-stable nucleus after this decay; thus, it is called isomeric decay. The half-life of gamma radiation is much shorter in comparison to other types of decay and generally less than 10 −9 s. However, some gamma radiation has a half-life of an hour, or even a day. Energy spectrums are not continuous. 8 1 Radiation Physics 10. The answer is c [ 42 ] . 1.3 Test 1.2A. Radiation Physics 1. Which of the following is not particulate radiation? (a) Electrons (b) Neutrons (c) Pi mesons (d) Alpha particles (e) Gamma rays 2. Which of the following statements about electrons is false ? (a) Electrons, due to their negative charge and low mass, can be accelerated to high energies in linear accelerators or betatrons. (b) There is a limited range of electrons in contrast to gamma and x-rays, and they can be absorbed by plastic, glass, or metal layers. (c) Electrons can be produced during nuclear decay processes and are called delta particles. (d) The number of electrons in an atom is equal to the number of positively charged protons in a neutral atom. (e) The electrical charge of an electron is equal to −1.6 × 10 −19 C. 3. Which of the following particles consists of one up and two down quarks? (a) Neutrons (b) Protons (c) Electrons (d) Positrons (e) Pi mesons Isotope [ 18 ] : Atoms with the same atomic number (proton number), but a different mass number (neutron number) are called isotopes ( 11 12 13 666 CCC , , ). Isotone : Atoms with the same number of neutrons, but a different number of protons are called isotones ( 9 10 11 12 3 4 56 Li Be B C , ,, ). Isobar : Atoms with the same mass number, but a different atomic number are called isobars ( 12 12 12 567 BCN , , ). Isomer : Atoms with the same atomic and mass number, but different energy levels are called isomers ( N-propyl alcohol, isopropyl alcohol, methyl ethyl ether, Tc 99m ). Fig. 1.7 Gamma emission [ 42 ] 60 Co 27 γ 60 Co 27 1.3 Test 1.2A. Radiation Physics 9 4. Which of the following statements is correct concerning the interaction of ionizing EM radiation with tissues? (a) Radiation is scattered when it passes through tissues and absorbed by tissues. (b) The intensity of radiation increases exponentially with the absorbent thickness. (c) The intensity of outgoing radiation only depends on the thickness of tissue. (d) The intensity of outgoing radiation only depends on the tissue absorption coeffi cient. (e) Only the photoelectric effect determines the absorption coeffi cient. 5. Which of the following statements concerning the photoelectric effect is false ? (a) Incoming radiation actually hits the orbital electron on the innermost side and propels it outside of the atom. (b) It is the basic interaction in diagnostic radiology. (c) It is dominant in energy levels higher than 35 kV and in atoms with low atomic number (Z). (d) Incoming photons lose all of their energy. (e) Bone absorbs more radiation than soft tissues because of this interaction. 6. Photons hit the outer orbital electron, and the photon and electron scatter in different directions at a certain angle. This phenomenon is called : (a) Coherent scattering (b) Photoelectric effect (c) Compton effect (d) Pair production (e) Photodisintegration 7. Which of the following photon-matter interactions causes the annihilation process and therefore can be evidence for the E = mc2 formula? (a) Coherent scattering (b) Photoelectric effect (c) Compton effect (d) Pair production (e) Photodisintegration 8. There is no transfer of energy to atoms in this event; thus, ionization does not occur. This type of photon-matter interaction is called : (a) Coherent scattering (b) Photoelectric effect (c) Compton effect (d) Pair production (e) Photodisintegration 9. Which of the following is not correctly related with bremsstrahlung x-rays and characteristic x-rays? (a) Characteristic x-rays are monoenergetic. (b) The probability of bremsstrahlung x-ray production increases with the square of the target’s atomic number. (c) Both types of x-rays can be used in megavoltage radiotherapy. 10 1 Radiation Physics (d) The major interaction occurs with inner orbital electrons in characteristic x-rays. (e) Both types of x-rays can be produced in x-ray tubes. 10. What is an electron volt (eV)? (a) The amount of kinetic energy gained by an electron (b) The amount of potential energy of an electron (c) An exposure unit (d) An absorbed dose unit (e) A radioactivity unit 1.4 Test 1.2A. Explanatory Answers 1. The answer is e [ 42 ] . Electrons, protons, alpha particles, neutrons, pi mesons, and heavy ions are forms of ionizing particulate radiation [ 19 ] . Electrons are the most widely used particles in routine clinics. The use of other particles is only performed in specifi c clinics worldwide. 2. The answer is c [ 42 ] . Electrons, due to their negative charge and low mass, can be accelerated to high energies in linear accelerators or betatrons. Electrons are normally bound to positively charged nuclei. The number of electrons in an atom is equal to the number of positively charged protons in a neutral atom. However, there can be more or fewer electrons than the number of positive charges in an atom. The total charge of atoms in this instance becomes either negative or positive, and this type of charged atom is called an ion. An electron that is not bound to an atom is called a free electron. Electrons can be produced during nuclear decay processes and called beta particles. There is a limited range of electrons in contrast to gamma and x-rays, and they can be absorbed by plastic, glass, or metal layers. 3. The answer is a [ 42 ] . Neutrons are the neutrally charged particles that enable the assembly of an atomic nucleus (Fig. 1.8 ). They decrease the pushing forces of protons to each other and jointly set the nucleus. They consist of one up and two down quarks. Protons are positively charged particles and have the same mass as neutrons (Fig. 1.9 ). They have two up quarks and one down quark. 4. The answer is a [ 42 ] . Radiation is scattered when it passes through tissues and absorbed by tissues [ 19, 20 ] . The intensities of mono-energetic x-rays or gamma rays attenuate exponentially within tissues. In other words, the intensity of radiation constantly decreases while moving forward within tissues. This decrease depends on the type of tissue and its thickness. As seen in the formula below, the intensity of radiation decreases exponentially with the absorbent thickness, and The mass of an electron 9.12 × 10 −31 kg The electrical charge of an electron −1.6 × 10 −19 C 1.4 Test 1.2A. Explanatory Answers 11 U D D Neutron U D = “up” quark = “down” quark Fig. 1.8 Neutron [ 42 ] Proton U D D U D = “up” quark = “down” quark Fig. 1.9 Proton [ 42 ] 12 1 Radiation Physics the intensity of outgoing radiation depends on the tissue absorption coeffi cient and its thickness. The photoelectric effect, Compton effect, and pair production determine the absorption coeffi cient. If the wavelength stays constant, the intensity of the radiation that passes through a tissue can be calculated by the following formula : 5. The answer is c [ 42 ] . At the atomic level, incoming radiation actually hits the orbital electron on the innermost side and propels it outside of the atom. This is the basic interaction in diagnostic radiology (Fig. 1.10 ). It is dominant in energy levels lower than 35 kV and in atoms with high atomic numbers (Z). Since the atomic number of bone is higher than that of soft tissues, bone absorbs more radiation than soft tissues. This absorption difference forms the basis of diagnostic radiology. In addition, this effect also explains why metals with higher atomic number (e.g., lead) are used for absorption of low-energy x-rays and gamma rays. 6. The answer is c [ 42 ] . The photon hits the outer orbital electron, and the photon and electron scatter in different directions at a certain angle [ 21 ] . The energy of the incoming photon is transferred into the electron in the form of kinetic energy. The scattered electrons also interact with the outer orbital electrons of other atoms. The incoming photon is scattered outside with a lower energy than its initial energy (Fig. 1.11 ). It is the most important explanation for the absorption of ionizing radiation in radiotherapy. It is the dominant effect Photon Fig. 1.10 Illustration of the Electron photoelectric effect [ 42 ]