Radiation Physics and Protection Practice Questions

Q: The photosensitive material used in X-rays films consists of:

Silver bromide. ***Silver bromide*** - **Silver bromide** is the primary photosensitive material used in X-ray film emulsions, forming the basis for image capture due to its high sensitivity to light and X-rays. - When exposed to radiation, **silver bromide crystals** undergo a chemical change, forming a **latent image** that can then be developed into a visible image. *Cellulose acetate* - **Cellulose acetate** is primarily used as the **film base** or support layer in X-ray films, providing flexibility and strength. - It is not a photosensitive material itself but rather a structural component that holds the emulsion layer. *Zinc oxide* - **Zinc oxide** can be used as a **photoconductor** in some imaging technologies but is not the primary photosensitive component in conventional X-ray film. - It is more commonly found in **direct digital radiography (DR) detectors** or older xeroradiography systems. *Cadmium selenide* - **Cadmium selenide** is a semiconductor material often used in **photovoltaic cells** and some types of **quantum dots** due to its luminescent properties. - It is not used as the photosensitive material in traditional X-ray film due to different chemical properties and sensitivity characteristics.

Q: Least penetrating power among following mentioned rays is

Alpha rays. ***Alpha rays*** - **Alpha particles** are relatively heavy and carry a **double positive charge**, interacting strongly with matter. - Due to their size and charge, they lose energy quickly and have the **shortest range** in air and can be stopped by a sheet of paper or skin. *Beta rays* - **Beta particles** are much lighter than alpha particles and carry a single negative or positive charge, making them more penetrating than alpha particles. - They can penetrate deeper into tissues and typically require materials like plastic or aluminum to be shielded. *Gamma rays* - **Gamma rays** are a form of electromagnetic radiation, meaning they are massless and chargeless, thus interacting less frequently with matter. - They possess high energy and are significantly more penetrating than both alpha and beta particles, requiring thick lead or concrete for shielding. *X-ray* - **X-rays** are also a form of electromagnetic radiation, similar to gamma rays but generally lower in energy and produced by different mechanisms. - While highly penetrating, they are typically less energetic than gamma rays and are commonly used in medical imaging due to their ability to pass through soft tissues but be absorbed by denser materials like bone.

Q: Bragg peak effect pronounced in:

Proton. ***Proton*** - The **Bragg peak** is a sharp increase in the dose deposited by a charged particle beam (like protons) just before it comes to rest. This allows for highly localized dose delivery. - This effect is a defining characteristic of **particulate radiation** due to their mass and charge, enabling precise targeting of tumors while sparing surrounding healthy tissue. *X-rays* - X-rays are a form of **electromagnetic radiation**, not charged particles, and therefore do not exhibit a Bragg peak. - Their dose deposition gradually decreases as they penetrate tissue, leading to an **exponential dose fall-off** rather than a sharp peak. *Neutrons* - Neutrons are **uncharged particles** and do not experience Coulombic interactions that lead to a Bragg peak. - They deposit energy primarily through **nuclear interactions**, resulting in a more uniform dose distribution rather than a sharp localized peak. *Electron* - While electrons are charged particles, their smaller mass and higher scattering in tissue lead to a **less pronounced and broader Bragg peak** compared to protons. - The dose distribution of electrons typically peaks closer to the surface and then rapidly falls off, making them suitable for **superficial tumors**.

Q: SI unit of absorbed dose is -

Gray. ***Gray*** - The **Gray (Gy)** is the SI unit of **absorbed dose**, defined as one joule of energy absorbed per kilogram of matter. - It quantifies the **energy deposited** by ionizing radiation in a material, such as human tissue. *Becquerel* - The **Becquerel (Bq)** is the SI unit of **radioactivity**, representing the number of disintegrations per second. - It measures the **activity of a source** of ionizing radiation, not the dose absorbed by a material. *Coulomb/cm* - **Coulomb (C)** is the SI unit of electric charge; therefore, **Coulomb/cm** would refer to **electric charge per unit length**. - This unit is not relevant to measuring **absorbed radiation dose**. *Sievert [Sv]* - The **Sievert (Sv)** is the SI unit of **equivalent dose** and **effective dose**, which account for the biological effects of different types of radiation. - It is derived from the Gray by multiplying by a **radiation weighting factor**, which considers the relative biological effectiveness of the radiation.

Q: The source of endogenous radiation is

Potassium. ***Potassium*** - **Potassium-40** is a naturally occurring radioactive isotope found in food, water, and the human body, making it a significant source of **endogenous radiation**. - Approximately 0.012% of all natural potassium is **K-40**, which emits beta particles and gamma rays as it decays. *Radon* - **Radon** is a radioactive gas that is primarily an **exogenous source** of radiation, found in soil and rocks and seeping into buildings. - While humans can inhale radon, it originates from outside the body rather than metabolic processes within. *Thorium* - **Thorium-232** is a naturally occurring radioactive element found in rocks and soil and is a source of **natural background radiation**, but it is primarily an **exogenous source**. - While small amounts can be ingested or inhaled, it is not a major contributor to radiation originating from within the body's natural composition. *Uranium* - **Uranium**, specifically **Uranium-238** and **Uranium-235**, is a naturally occurring radioactive element found in the Earth's crust and is an **exogenous source** of radiation. - Exposure to uranium is typically environmental and is not considered an endogenous source of radiation within the human body.

Q: Which substance has the highest Hounsfield Unit (HU) value?

Bone. ***Bone*** - **Bone**, particularly cortical bone, has the **highest density** and thus the highest Hounsfield Unit (HU) value among the given options, typically ranging from +300 to +1000 HU. - Its high density causes **significant attenuation** of X-rays, leading to a bright appearance on CT scans. *Water* - **Water** is defined as having a Hounsfield Unit (HU) value of **0**, serving as the reference point for the scale. - Substances less dense than water have negative HU values, while those more dense have positive values. *Fat* - **Fat** has a negative Hounsfield Unit (HU) value, typically ranging from **-50 to -100 HU**, indicating it is less dense than water. - This low density causes less X-ray attenuation, making fat appear dark on CT scans. *Soft tissue* - **Soft tissues** such as muscle or organs generally have HU values slightly higher than water, ranging from **+20 to +60 HU**. - Their density is greater than fat but significantly less than bone.

Q: What is the half-life of Ra-226?

1600 years. ***1600 years*** - The **half-life of Radium-226 (Ra-226)** is approximately **1600 years** (more precisely 1602 years). - This long half-life means it decays slowly, making it a persistent source of radiation. - Ra-226 is historically significant in radiotherapy and radiation protection studies. *8 days* - **Iodine-131 (I-131)** has a half-life of 8 days, which is used in medical therapies and diagnostics. - This is significantly shorter than the half-life of Ra-226. *28 years* - The half-life of **Strontium-90 (Sr-90)** is approximately 28-29 years, a common fission product. - This isotope is known for its bone-seeking properties and is much shorter-lived than Ra-226. *38 years* - This is a distractor value that does not correspond to Ra-226. - It may be confused with **Cesium-137 (Cs-137)**, which has a half-life of approximately 30 years. - This is not the half-life of Radium-226.

Q: Which of the following statements about neutron radiography is true?

Is an example of non-destructive testing. ***Is an example of non-destructive testing*** - **Neutron contrast studies** are a form of **non-destructive testing** (NDT) because they allow for the analysis of a material's internal structure and properties without causing damage to the sample. - This characteristic makes them valuable for examining delicate or critical components where preserving structural integrity is essential. *Cannot provide spatial resolution of internal structures* - This statement is incorrect; **neutron imaging** techniques, such as **neutron radiography** and **tomography**, are capable of providing detailed **spatial resolution** of internal structures. - These methods can reveal features like cracks, voids, and material interfaces within an object. *Hydrogen and boron have low neutron absorption cross-sections* - This statement is incorrect; **hydrogen** and especially **boron** have very **high neutron absorption cross-sections**. - This high absorption is precisely why these elements are excellent for **neutron contrast imaging**, as they create strong contrast by attenuating neutrons significantly. *Cannot detect light elements within heavy metallic matrices* - This statement is incorrect; one of the key advantages of **neutron imaging** over X-ray imaging is its ability to **detect light elements** (like hydrogen, carbon, nitrogen, oxygen) even when they are embedded within **heavy metallic matrices**. - This is due to the inherent difference in how neutrons interact with matter compared to X-rays, as neutron interaction cross-sections do not monotonically increase with atomic number.

Q: Which type of radiation exhibits the Bragg peak effect?

Proton. ***Proton*** - **Protons** are charged particles that deposit most of their energy at the end of their range, creating a sharp maximum called the **Bragg peak**. - This characteristic allows for highly conformal radiation delivery, sparing surrounding healthy tissue, which is beneficial in **radiation oncology**. *X ray* - **X-rays** are photons that exhibit an exponential decrease in dose deposition with increasing depth, not a sharp peak. - Their energy deposition profile is broad, making it difficult to precisely target deep tumors without affecting superficial tissues. *Neutron* - **Neutrons** are uncharged particles that deposit energy through nuclear interactions, resulting in a relatively continuous dose deposition rather than a distinct Bragg peak. - They have a high **linear energy transfer (LET)**, which makes them effective against certain radioresistant tumors but also more damaging to surrounding healthy tissue. *Electron* - **Electrons** are charged particles that deposit their energy closer to the surface due to continuous energy loss through ionization and excitation, resulting in a flatter dose profile compared to a Bragg peak. - They are typically used for treating superficial tumors because their range in tissue is limited and their dose distribution falls off rapidly after reaching a certain depth.

Q: All are done to minimize radiation exposure to the patient under fluoroscopy, except which of the following?

Increasing fluoroscopic time. ***Increasing fluoroscopic time*** - **Increasing fluoroscopic time** directly leads to a greater cumulative dose of radiation received by the patient. - This action goes against the principle of **ALARA (As Low As Reasonably Achievable)** for radiation safety. *Decreasing fluoroscopic time* - **Decreasing fluoroscopic time** reduces the total duration of X-ray exposure, thereby minimizing the radiation dose to the patient. - This is a fundamental practice in radiation protection. *Using low dose of radiation* - Employing **low-dose radiation protocols** means using the minimum amount of radiation necessary to obtain diagnostic images. - This directly reduces the patient's exposure while maintaining image quality for diagnosis. *Decrease in field of view* - A **decrease in the field of view** (collimation) restricts the X-ray beam to only the area of interest, limiting irradiation of surrounding healthy tissues. - This targeted approach significantly reduces the overall radiation dose to the patient.

Question 1

The photosensitive material used in X-rays films consists of:

Accepted Answer

Silver bromide

Answer

Cellulose acetate

Answer

Zinc oxide

Answer

Cadmium selenide

Question 2

Least penetrating power among following mentioned rays is

Accepted Answer

Alpha rays

Answer

Beta rays

Answer

Gamma rays

Answer

X-ray

Question 3

Bragg peak effect pronounced in:

Accepted Answer

Proton

Answer

Electron

Answer

X-rays

Answer

Neutrons

Question 4

SI unit of absorbed dose is -

Accepted Answer

Gray

Answer

Becquerel

Answer

Sievert [Sv]

Answer

Coulomb/cm

Question 5

The source of endogenous radiation is

Accepted Answer

Potassium

Answer

Radon

Answer

Thorium

Answer

Uranium

Question 6

Which substance has the highest Hounsfield Unit (HU) value?

Accepted Answer

Bone

Answer

Water

Answer

Fat

Answer

Soft tissue

Question 7

What is the half-life of Ra-226?

Accepted Answer

1600 years

Answer

28 years

Answer

38 years

Answer

8 days

Question 8

Which of the following statements about neutron radiography is true?

Accepted Answer

Is an example of non-destructive testing

Answer

Cannot provide spatial resolution of internal structures

Answer

Hydrogen and boron have low neutron absorption cross-sections

Answer

Cannot detect light elements within heavy metallic matrices

Question 9

Which type of radiation exhibits the Bragg peak effect?

Accepted Answer

Proton

Answer

X ray

Answer

Neutron

Answer

Electron

Question 10

All are done to minimize radiation exposure to the patient under fluoroscopy, except which of the following?

Accepted Answer

Increasing fluoroscopic time

Answer

Decreasing fluoroscopic time

Answer

Using low dose of radiation

Answer

Decrease in field of view

Radiation Physics and Protection — MCQs

Radiation Physics and Protection — MCQs

On this page

Practice by Chapter

Want unlimited practice?