Radiation Oncology Basics Practice Questions

Q: Mantle irradiation is used in:

Hodgkin's disease. **Hodgkin's disease** - **Mantle irradiation** is a historical radiation therapy technique specifically designed for **Hodgkin's lymphoma**, targeting lymph node regions above the diaphragm (cervical, supraclavicular, axillary, and mediastinal). - This method was used to irradiate contiguous lymph node chains, which is characteristic of Hodgkin's lymphoma spread. *Neuroblastoma* - **Neuroblastoma** is a solid tumor of childhood originating from neural crest cells, typically treated with surgery, chemotherapy, and sometimes local radiation to the primary tumor site, not mantle fields. - It does not primarily involve the cervical, supraclavicular, axillary, and mediastinal lymph nodes in a pattern suitable for mantle irradiation. *Chest secondaries from some cancers* - **Chest secondaries**, or metastases, from other cancers would require radiation fields tailored to the specific metastatic sites, which vary greatly depending on the primary cancer and spread pattern. - Mantle fields are too broad and specific to lymph node regions to be appropriate for varied metastatic disease. *Leukemia* - **Leukemia** is a cancer of the blood and bone marrow, typically treated with systemic chemotherapy and sometimes total body irradiation (TBI) if bone marrow transplantation is planned. - It does not involve localized lymph node chains in a way that would be effectively treated with mantle irradiation.

Q: The technique employed in radiotherapy to counteract the effect of tumour motion due to breathing is known as –

Gating. ***Gating*** - **Respiratory gating** involves delivering radiation only during specific phases of the patient's breathing cycle when the tumor is within a defined target window. - This technique helps to **minimize the irradiated volume** of healthy tissue by avoiding treatment when the tumor moves out of the planned treatment field. *Tracking* - **Respiratory tracking** involves actively adjusting the radiation beam in real-time to follow the motion of the tumor during breathing. - While it aims to compensate for motion, it is a different mechanism from gating, which involves turning the beam on and off. *Modulation* - **Intensity-modulated radiation therapy (IMRT)** and similar techniques focus on varying the intensity of the radiation beam across the treatment field to conform the dose to the tumor shape. - Modulation addresses dose distribution within a target, rather than directly managing tumor motion due to respiration. *Arc technique* - **Arc therapy** (e.g., VMAT) involves continuous delivery of radiation as the treatment machine rotates around the patient. - This technique optimizes dose delivery angles and conformity but does not inherently counteract tumor motion, although it can be combined with motion management.

Q: Which radiotherapy technique involves the use of remote afterloading to deliver radiation directly to the tumor?

Brachytherapy. ***Correct: Brachytherapy*** - **Remote afterloading** is a hallmark of modern brachytherapy, where radioactive sources are automatically advanced into catheters placed within or near the tumor. - This technique allows for the delivery of a **high dose of radiation directly to the tumor** while sparing surrounding healthy tissues. - Examples include **intracavitary** (cervical cancer), **interstitial** (prostate cancer), and **intraluminal** (esophageal cancer) brachytherapy. *Incorrect: External Beam Radiotherapy* - This technique involves delivering radiation from a machine **outside the body** to target a tumor. - It does not involve the direct placement of radioactive sources within the patient or the use of **remote afterloading**. *Incorrect: Stereotactic Radiotherapy* - While a precise form of external beam radiotherapy using focused beams, it still involves an **external source** of radiation. - It does not utilize internal radioactive sources or **afterloading techniques**. *Incorrect: Proton Beam Radiotherapy* - This is an advanced form of external beam radiotherapy that uses **protons instead of photons** to deliver radiation with high precision. - It does not involve the placement of radioactive sources within the patient or the use of **remote afterloading**.

Q: Commonly used type of radiation in radiotherapy is:

X-rays. ***X-rays*** - **X-rays** are the most commonly used type of radiation in external beam radiotherapy due to their ability to penetrate tissues and deliver precise doses to tumors. - Modern radiotherapy devices, such as **linear accelerators**, generate high-energy X-rays for cancer treatment. *Alpha rays* - **Alpha particles** have a very limited penetration range in tissue, making them unsuitable for treating deep-seated tumors with external beam radiotherapy. - Their primary use is in targeted internal radiation therapies, such as **alpha-emitting radioisotopes** in specific radiopharmaceuticals. *Beta rays* - **Beta particles** have a slightly greater penetration than alpha particles but are still generally limited for superficial treatment or internal applications rather than external beam therapy for most cancers. - They are used in certain types of **brachytherapy** or in radioisotope treatments. *Gamma rays* - **Gamma rays** are used in radiotherapy, particularly in older cobalt-60 teletherapy units, but less frequently than X-rays generated by linear accelerators today. - While possessing good penetration, their energy spectrum is fixed by the isotope, offering less flexibility in treatment planning than variable-energy X-rays.

Q: In which of the following conditions is Stereotactic Radiosurgery primarily indicated?

Arteriovenous malformation of the brain. ***Arteriovenous malformation of the brain*** - **Stereotactic Radiosurgery (SRS)** is a highly effective treatment for brain AVMs, particularly those that are **small to medium-sized** and located in eloquent brain regions. - SRS delivers a **highly focused dose of radiation** directly to the AVM, causing the abnormal blood vessels to gradually close off over time, reducing the risk of hemorrhage. *Medulloblastoma of the spinal cord* - Medulloblastoma is a **highly aggressive malignant brain tumor** that often metastasizes to the spinal cord via cerebrospinal fluid. - Treatment for spinal medulloblastoma typically involves **cranio-spinal irradiation with chemotherapy**, and SRS is generally not the primary treatment modality for diffuse spinal disease. *Ependymoma* - Ependymomas are tumors arising from the **ependymal cells** lining the ventricles and spinal cord. - While surgery is the primary treatment, radiotherapy, including **conventional fractionated external beam radiation**, is often used as adjuvant therapy, but SRS is less commonly the sole primary indication. *Glioblastoma multiforme* - Glioblastoma multiforme (GBM) is the **most aggressive primary brain tumor** and is typically treated with **maximal surgical resection followed by concurrent chemoradiotherapy**. - While SRS may be used in carefully selected cases for **recurrent GBM** or as a boost in primary treatment, it is not the primary solitary indication for initial management.

Q: Gamma knife utilizes which radioactive isotope?

Cobalt-60. ***Cobalt-60*** - The **Gamma Knife** employs multiple sources of **cobalt-60** to deliver highly focused beams of gamma radiation. - These beams converge at precise intracranial targets to treat various conditions like **tumors** and **vascular malformations**. *Strontium 89* - **Strontium-89** is a beta-emitting isotope used primarily in the palliation of **bone pain** from metastatic cancer. - It is not used in the **Gamma Knife** for focused intracranial radiation therapy. *I-131* - **Iodine-131** is a beta and gamma-emitting isotope used mainly in the treatment of **thyroid cancer** and hyperthyroidism. - Its application is systemic or targeted to the thyroid gland, not via the **Gamma Knife**. *P-32* - **Phosphorus-32** is a beta-emitting isotope historically used in applications like treating polycythemia vera and sometimes for intracavitary radiation. - It is not a component of the **Gamma Knife** system.

Q: What is the standard radiation dose delivered to Point A in the treatment of cervical cancer?

7000 cGy. ***7000 cGy*** - The standard radiation dose delivered to **Point A** in the treatment of cervical cancer, when combined with external beam radiation therapy and brachytherapy, typically totals around **7000-8000 cGy**. This dose aims to achieve tumor control while minimizing toxicity to surrounding organs. - **Point A** is a defined anatomical reference point used in brachytherapy planning for cervical cancer, representing the approximate location of the **uterine arteries** and the site of potential tumor recurrence. *3000 cGy* - A dose of **3000 cGy** is too low for definitive treatment of cervical cancer. Such a dose might be used as a palliative measure or part of a more extensive treatment regimen, but not as the total dose to Point A. - Inadequate dosing increases the risk of **local failure** and recurrence of the cancer. *5000 cGy* - While **5000 cGy** is a commonly used dose for external beam radiation therapy (EBRT) in cervical cancer, it is typically supplemented with brachytherapy to boost the dose to Point A and the tumor. - This dose alone would likely be insufficient to achieve adequate tumor control at **Point A** and the whole tumor volume. *8500 cGy* - A dose of **8500 cGy** to Point A might be considered in some highly selected and advanced cases, but it generally approaches the upper limits of tolerance for surrounding critical structures. - Doses this high carry an increased risk of **severe late toxicities** to organs such as the bladder, rectum, and small bowel.

Q: Which of the following radioisotopes is MOST commonly used in brachytherapy for cervical cancer?

Iridium-192. ***Iridium-192*** - **Iridium-192** is the most commonly used radioisotope for **high-dose-rate (HDR)** brachytherapy in cervical cancer due to its optimal energy and half-life for this application. - Its **higher dose rate** allows for shorter treatment times and outpatient procedures, making it widely preferred in modern radiation oncology. *Cobalt-60* - **Cobalt-60** was historically used in brachytherapy but has largely been replaced by other isotopes due to its **higher energy** and longer half-life, which pose greater shielding challenges. - While still used in some external beam radiation therapy units, it is less common for intracavitary brachytherapy in cervical cancer compared to Iridium-192. *Cesium-137* - **Cesium-137** is primarily used in **low-dose-rate (LDR)** brachytherapy, which involves continuous irradiation over several days. - While effective, LDR brachytherapy with Cesium-137 requires inpatient admission and prolonged immobilization, making it less commonly used than **HDR brachytherapy** with Iridium-192 in many contemporary practices for cervical cancer. *Radium-226* - **Radium-226** was the first radioisotope used for brachytherapy in cervical cancer and was widely employed historically. - However, due to **radiation safety concerns** (long half-life of 1600 years) and the availability of safer alternatives like Iridium-192 and Cesium-137, it has been largely phased out in modern practice.

Q: Mantle field radiation is primarily used in the treatment of which condition?

Hodgkin's lymphoma. ***Hodgkin's lymphoma*** - **Mantle field radiation** is a historical technique primarily used for treating **supradiaphragmatic lymph node involvement** in Hodgkin's lymphoma. - This technique covers lymphatic regions such as the **neck**, **axillae**, and **mediastinum** in a single field due to the predictable spread patterns of the disease. *Mantle cell lymphoma* - This is a type of **non-Hodgkin lymphoma** that typically involves widespread disease at diagnosis, making regional radiation like mantle field therapy less suitable. - Treatment usually involves systemic chemotherapy and sometimes **stem cell transplant**. *Multiple myeloma* - Multiple myeloma is a **plasma cell malignancy** that primarily affects the **bone marrow** throughout the body. - Its widespread nature requires systemic therapies, and radiation is typically used for **localized pain control** or specific skeletal lesions, not wide-field regional approaches. *Cervical cancer* - Cervical cancer is a **gynecologic malignancy** typically treated with a combination of **surgery**, **pelvic radiation**, and **chemotherapy**. - The anatomy and lymphatic drainage patterns are distinct, making mantle field radiation irrelevant for this condition.

Question 1

Mantle irradiation is used in:

Accepted Answer

Hodgkin's disease

Answer

Neuroblastoma

Answer

Chest secondaries from some cancers

Answer

Leukaemia

Question 2

The technique employed in radiotherapy to counteract the effect of tumour motion due to breathing is known as –

Accepted Answer

Gating

Answer

Tracking

Answer

Modulation

Answer

Arc technique

Question 3

Which radiotherapy technique involves the use of remote afterloading to deliver radiation directly to the tumor?

Accepted Answer

Brachytherapy

Answer

External Beam Radiotherapy

Answer

Stereotactic Radiotherapy

Answer

Proton Beam Radiotherapy

Question 4

Commonly used type of radiation in radiotherapy is:

Accepted Answer

X-rays

Answer

Alpha rays

Answer

Beta rays

Answer

Gamma rays

Question 5

In which of the following conditions is Stereotactic Radiosurgery primarily indicated?

Accepted Answer

Arteriovenous malformation of the brain

Answer

Ependymoma

Answer

Medulloblastoma of the spinal cord

Answer

Glioblastoma multiforme

Question 6

Gamma knife utilizes which radioactive isotope?

Accepted Answer

Cobalt-60

Answer

Strontium 89

Answer

P-32

Answer

I-131

Question 7

What is the standard radiation dose delivered to Point A in the treatment of cervical cancer?

Accepted Answer

7000 cGy

Answer

3000 cGy

Answer

5000 cGy

Answer

8500 cGy

Question 8

Which of the following radioisotopes is MOST commonly used in brachytherapy for cervical cancer?

Accepted Answer

Iridium-192

Answer

Cobalt-60

Answer

Cesium-137

Answer

Radium-226

Question 9

Mantle field radiation is primarily used in the treatment of which condition?

Accepted Answer

Hodgkin's lymphoma

Answer

Mantle cell lymphoma

Answer

Multiple myeloma

Answer

Cervical cancer

Question 10

A woman with endometrial carcinoma is undergoing radiotherapy. Which of the following statements about radiation therapy is true?

Accepted Answer

Intensity is inversely proportional to the square of the distance from the source.

Answer

Small intestinal mucosa is radioresistant.

Answer

Rapidly proliferating cells are radioresistant.

Answer

Small blood vessels are radioresistant.

Radiation Oncology Basics — MCQs

Radiation Oncology Basics — MCQs

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