Image-Guided Radiation Therapy — MCQs
Precise FNAC can be obtained by using:
I/V contrast is not used in -
The technique employed in radiotherapy to counteract the effect of tumour motion due to breathing is known as –
For which malignancy is intensity-modulated radiotherapy (IMRT) the most suitable?
Which one of the following imaging techniques gives the maximum radiation exposure to the patient?
In cervical cancer brachytherapy, the primary reference point for dose prescription is -
Which is the treatment of choice for irradiation in Chordoma?
Which radioisotope is commonly used in teletherapy?
A patient was treated for mantle cell Hodgkin lymphoma with radiation therapy. After 6 months he develops an electric shock-like pain along the spine on flexing his neck. What is the diagnosis?
An elderly male presents with T3N0 laryngeal carcinoma. Treatment is:
Image-Guided Radiation Therapy Indian Medical PG Practice Questions and MCQs
Question 1: Precise FNAC can be obtained by using:
- A. CT
- B. MRI
- C. Endoscopic USG
- D. USG (Correct Answer)
Explanation: ***USG*** - **Ultrasound (USG)** guidance is the **most commonly used** modality for **fine needle aspiration cytology (FNAC)** due to its real-time imaging capabilities, allowing the operator to visualize the needle tip entering the lesion. - It is particularly useful for superficial lesions or those with a clear acoustic window, offering good **spatial resolution**, wide availability, no radiation exposure, and accessibility for most body regions. - USG provides excellent precision for routine FNAC procedures across various clinical settings. *CT* - **Computed tomography (CT)** provides excellent anatomical detail and is useful for guiding FNAC in deeper or more complex lesions within the body cavity (e.g., lungs, retroperitoneum). - However, it involves **ionizing radiation** and, unlike USG, does not offer real-time visualization of the needle path, requiring intermittent scanning. *MRI* - **Magnetic resonance imaging (MRI)** offers superior soft tissue contrast and is excellent for visualizing certain lesions, but it is less commonly used for routine FNAC guidance. - The high cost, long scan times, and challenges with MRI-compatible needles make it less practical for real-time guidance compared to USG or CT. *Endoscopic USG* - **Endoscopic ultrasound (EUS)** is highly effective for precise FNAC of lesions adjacent to the gastrointestinal tract (e.g., pancreas, mediastinum, submucosal lymph nodes) as it provides high-resolution imaging from within. - While very precise for its specific indications, it is an invasive procedure requiring endoscopy and is not suitable for all body regions like routine superficial or transthoracic biopsies where the question is generally referring to.
Question 2: I/V contrast is not used in -
- A. IVP
- B. Myelography (Correct Answer)
- C. MRI
- D. CT scan
Explanation: ***Myelography*** - Myelography involves injecting contrast material directly into the **subarachnoid space** of the spinal canal to visualize nerve roots and the spinal cord, and therefore does not use intravenous contrast. - The contrast in myelography is typically **iodinated non-ionic contrast** injected intrathecally, not intravenously. *IVP* - **Intravenous Pyelogram (IVP)** is a radiological procedure that specifically uses **intravenous iodinated contrast** to visualize the kidneys, ureters, and bladder. - The contrast is excreted by the kidneys, highlighting the urinary tract structures on X-ray images. *MRI* - While many MRI scans do not require contrast, **intravenous gadolinium-based contrast agents** are commonly used to enhance visualization of certain pathologies like tumors, inflammation, or vascular anomalies. - The contrast is administered intravenously to accumulate in areas with increased vascularity or disrupted blood-brain barrier. *CT scan* - **CT scans** frequently utilize **intravenous iodinated contrast** to improve the visibility of blood vessels, organs, and various lesions like tumors or inflammatory processes. - The contrast enhances density differences between tissues, making pathologies more conspicuous.
Question 3: The technique employed in radiotherapy to counteract the effect of tumour motion due to breathing is known as –
- A. Tracking
- B. Gating (Correct Answer)
- C. Modulation
- D. Arc technique
Explanation: ***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.
Question 4: For which malignancy is intensity-modulated radiotherapy (IMRT) the most suitable?
- A. Lung
- B. Prostate (Correct Answer)
- C. Leukemias
- D. Stomach
Explanation: ***Prostate*** - **IMRT** is highly suitable for prostate cancer due to the prostate's proximity to critical organs like the **rectum and bladder**. - Its ability to conform the **radiation dose tightly** to the tumor while sparing adjacent healthy tissue significantly reduces side effects like **rectal bleeding** or **urinary dysfunction** [1]. *Lung* - While IMRT is used in lung cancer, especially for complex tumors near vital structures, **stereotactic body radiation therapy (SBRT)** is often preferred for early-stage lung cancer due to its high dose delivery over fewer fractions. - The **motion of the lung** during respiration can make precise IMRT delivery challenging without specialized techniques like **gating or tracking**. *Leukemias* - **Leukemias** are systemic diseases involving blood and bone marrow, making localized radiation therapies like IMRT generally unsuitable as a primary treatment. - Treatment for leukemias primarily involves **chemotherapy, targeted therapy, or stem cell transplant**. *Stomach* - **Stomach cancer** often requires larger radiation fields due to tumor spread and nodal involvement, making the precise dose sculpting of IMRT less advantageous compared to its benefits in smaller, well-defined tumors. - The **mobility of the stomach** and surrounding organs can also present challenges for highly conformal radiation delivery.
Question 5: Which one of the following imaging techniques gives the maximum radiation exposure to the patient?
- A. Chest X-ray
- B. MRI
- C. CT scan (Correct Answer)
- D. Bone scan
Explanation: ***CT scan*** - **CT scans** involve multiple X-ray projections and computer processing, resulting in a significantly higher radiation dose compared to conventional X-rays. - The effective dose from a single chest or abdominal CT scan can be equivalent to hundreds of standard chest X-rays, making it the highest radiation contributor among the options listed. *Chest X-ray* - A **chest X-ray** uses a very small amount of ionizing radiation, typically one of the lowest doses among diagnostic imaging techniques that involve radiation. - While it uses radiation, its contribution to overall exposure is minimal, especially compared to CT scans. *MRI* - **MRI (Magnetic Resonance Imaging)** uses strong magnetic fields and radio waves to create detailed images of organs and soft tissues, not ionizing radiation. - Therefore, it involves **no radiation exposure** to the patient. *Bone scan* - A **bone scan** uses a small amount of **radioactive tracer** (radionuclide) injected into the bloodstream, which is then detected by a special camera. - While it involves radiation, the dose is generally lower than that of a CT scan and is comparable to or slightly higher than a series of X-rays.
Question 6: In cervical cancer brachytherapy, the primary reference point for dose prescription is -
- A. Point A (Correct Answer)
- B. Point B
- C. Side walls of pelvis
- D. Point H
Explanation: ***Point A*** - **Point A** is defined as 2 cm lateral to the central canal of the uterus and 2 cm superior to the external os, representing a dose estimation to the **parametrium** and a critical reference for tumoricidal dose. - This point serves as the **primary prescription and reporting point** for brachytherapy in cervical cancer, as it is highly correlated with treatment outcomes and complications. - Established by **ICRU Report 38** as the standard reference point for dose prescription. *Point B* - **Point B** is located 5 cm from the midline (3 cm lateral to Point A) at the level of Point A, and is primarily used to estimate the dose received by the **pelvic side wall** and regional lymphatics. - It provides an indication of dose to structures further from the applicator but is **not the primary prescription point** for the target volume in brachytherapy. *Side walls of pelvis* - The dose to the **side walls of the pelvis** is relevant for assessing potential toxicity to structures like the obturator nerve and external iliac vessels, and for ensuring adequate coverage of pelvic lymph nodes. - While critical for treatment planning, the side walls themselves are not a primary dose prescription point but rather a **region of interest** for dose constraints and coverage. *Point H* - **Point H** represents the reference point for estimating the dose to the **rectum** in brachytherapy, located at the posterior vaginal wall. - While important for assessing **rectal toxicity** and as a dose-limiting structure, Point H is used for reporting organ-at-risk doses, not for primary tumor dose prescription.
Question 7: Which is the treatment of choice for irradiation in Chordoma?
- A. Protons (Correct Answer)
- B. Electrons
- C. Gamma radiation
- D. 3D - CRT
Explanation: ***Protons*** - Proton therapy is the treatment of choice for **chordoma** due to its ability to deliver a high dose of radiation directly to the tumor while minimizing dose to surrounding healthy tissues. - This precision is critical for tumors located near **sensitive structures**, such as the brainstem, spinal cord, or optic nerves, common sites for chordomas. *Electrons* - **Electron therapy** is typically used for superficial tumors because electrons rapidly deposit their energy within the first few centimeters of tissue. - Chordomas are often deeply seated tumors, making electron therapy an unsuitable option for comprehensive treatment. *Gamma radiation* - **Gamma radiation**, as delivered by techniques like **Gamma Knife radiosurgery**, is primarily used for smaller, well-circumscribed intracranial lesions. - While precise, it may not be ideal for the larger, often irregularly shaped chordomas found in the skull base or sacrum, and it lacks the dose-sparing capabilities of proton beams at depth. *3D - CRT* - **3D Conformal Radiation Therapy (3D-CRT)** uses multiple beams to shape the radiation dose to the tumor, offering better conformity than conventional radiation. - However, compared to proton therapy, 3D-CRT still deposits a significant amount of radiation in tissues both distal and proximal to the tumor, leading to a higher risk of side effects, which is particularly concerning for chordomas given their proximity to critical structures.
Question 8: Which radioisotope is commonly used in teletherapy?
- A. Ra-226
- B. Cs-137
- C. Co-60 (Correct Answer)
- D. Ir-192
Explanation: ***Co-60*** - **Cobalt-60** is a widely used radioisotope in teletherapy (external beam radiotherapy) due to its high-energy gamma emissions (1.17 and 1.33 MeV). - Its relatively long half-life of **5.27 years** makes it practical for sustained clinical use in **teletherapy units**. *Ra-226* - **Radium-226** was historically used in brachytherapy but has largely been replaced due to its alpha emissions, which are difficult to shield, and its long-lived radioactive decay products. - Its use for teletherapy is **not common** because of these safety concerns and the availability of more suitable isotopes. *Cs-137* - **Cesium-137** is primarily used in **brachytherapy** and some low-dose rate teletherapy machines for specific applications, but not as commonly as Co-60 for general teletherapy. - Its lower gamma energy (0.662 MeV) and shorter half-life than Co-60 (30.17 years) make it less ideal for the widespread **deep penetration** required in many teletherapy treatments. *Ir-192* - **Iridium-192** is predominantly used in **high-dose-rate (HDR) brachytherapy** for temporary implants, delivering radiation over short periods. - Its relatively short half-life of **73.8 days** and lower average gamma energy make it unsuitable for typical long-term teletherapy external beam applications.
Question 9: A patient was treated for mantle cell Hodgkin lymphoma with radiation therapy. After 6 months he develops an electric shock-like pain along the spine on flexing his neck. What is the diagnosis?
- A. Multiple sclerosis
- B. Cervical arthritis
- C. Spinal cord compression
- D. Radiation-induced myelopathy (Correct Answer)
Explanation: ***Radiation-induced myelopathy*** - This diagnosis is signaled by the **electric shock-like pain** along the spine upon neck flexion (Lhermitte's sign) developing 6 months after receiving **radiation therapy** for lymphoma. - This condition represents a delayed complication of radiation, affecting the **spinal cord's white matter**. *Multiple sclerosis* - While it can present with **Lhermitte's sign**, the patient's history of **radiation therapy** and its timing strongly favor myelopathy. [1] - MS is a demyelinating disease usually presenting with a **variety of neurological symptoms** over time, rather than isolated Lhermitte's sign post-radiation. *Cervical arthritis* - This condition would typically present with **neck pain and stiffness**, possibly radiating pain, and limited range of motion, but not specifically an electric shock sensation on neck flexion (Lhermitte's sign). [2] - While an osteophyte might cause compression, the specific **Lhermitte's sign** points away from simple degenerative changes. *Spinal cord compression* - While Lhermitte's sign can indicate spinal cord involvement, **spinal cord compression** usually implies an acute or subacute onset with more severe and progressive neurological deficits, such as motor weakness or sensory loss, and bladder/bowel dysfunction. [3] - Given the 6-month delay and the isolated Lhermitte's sign after radiation, **radiation-induced myelopathy** is a more specific and likely cause.
Question 10: An elderly male presents with T3N0 laryngeal carcinoma. Treatment is:
- A. Radical radiotherapy followed by chemotherapy
- B. Concurrent chemoradiotherapy (Correct Answer)
- C. Neo-adjuvant chemotherapy followed by radiotherapy
- D. Radical radiotherapy without chemotherapy
Explanation: ***Concurrent chemoradiotherapy*** - For **T3N0 laryngeal carcinoma**, concurrent chemoradiotherapy is the **preferred organ preservation treatment** in appropriate candidates, offering comparable oncologic outcomes to total laryngectomy. - The combination of **chemotherapy (typically cisplatin) and radiation** works synergistically to enhance tumor cell kill, with chemotherapy acting as a **radiosensitizer**. - This approach achieves **local control rates of 60-70%** while preserving laryngeal function and voice quality. - Standard protocols include **radiation (70 Gy) with concurrent cisplatin** (100 mg/m² on days 1, 22, 43). *Radical radiotherapy without chemotherapy* - **Radiation therapy alone** is an alternative organ preservation approach for selected T3N0 cases, particularly in **elderly patients** with comorbidities who cannot tolerate chemotherapy. - However, multiple studies show that **concurrent chemoradiotherapy provides superior local control** and survival compared to radiation alone for T3 laryngeal cancer. - RT alone may achieve **local control in 50-60%** of T3 cases, which is lower than concurrent chemoRT. *Radical radiotherapy followed by chemotherapy* - Sequential therapy is **less effective** than concurrent administration because chemotherapy's primary role is as a **radiosensitizer** during radiation. - Delivering chemotherapy after radiation loses the **synergistic effect** crucial for tumor control. - This sequence is not a standard treatment approach for T3 laryngeal cancer. *Neo-adjuvant chemotherapy followed by radiotherapy* - **Induction chemotherapy** followed by radiation is used in some organ preservation protocols, particularly for advanced disease. - However, this approach is typically reserved for **T4 disease** or for tumor downstaging assessment. - Current evidence favors **concurrent chemoradiotherapy over sequential induction-radiation** for T3 laryngeal cancer in terms of organ preservation rates and survival.
Want unlimited practice?
Get full access to all questions, explanations, and performance tracking.
Start For Free