Functional Imaging in Oncology — MCQs
Gold standard investigation for breast carcinoma screening in a patient with silicone breast implants
On MRI, which of the following shows diffusion restriction?
Investigation of choice for leptomeningeal carcinomatosis:
Radiation-induced necrosis can be diagnosed by:
Distant bone metastases can be best detected by which of the following imaging techniques?
MUGA scan is not useful in:
In a child, non-functioning kidney is best diagnosed by:
Tc-labeled RBCs are used for all except:
CD40 deficiency in a person signifies?
Thiamine deficiency is assessed by:
Functional Imaging in Oncology Indian Medical PG Practice Questions and MCQs
Question 1: Gold standard investigation for breast carcinoma screening in a patient with silicone breast implants
- A. Mammography
- B. CT scan
- C. USG
- D. MRI (Correct Answer)
Explanation: ***MRI*** - **MRI** is considered the **gold standard** for breast cancer screening in patients with silicone breast implants due to its superior ability to visualize breast tissue through the implant and detect subtle lesions. - It offers **high sensitivity** in detecting both implant rupture and early malignancies, often providing better clarity than mammography in augmented breasts where implants can obscure tissue. *Mammography* - While a standard screening tool, **mammography** can be limited in patients with silicone implants because the implants can **obscure adjacent breast tissue**, making detection of small masses challenging. - Special views (e.g., **Eklund views**) can be used, but sensitivity is still reduced compared to MRI in augmented breasts. *CT scan* - **CT scans** are not routinely used for primary breast cancer screening due to their use of **ionizing radiation** and lower sensitivity for detecting early breast lesions compared to MRI. - CT is more commonly used for **staging** advanced cancers or evaluating complex masses detected by other modalities. *USG* - **Ultrasound (USG)** is a valuable complementary tool, especially for evaluating palpable lumps or clarifying findings from mammography, but it is **operator-dependent** and has a lower overall sensitivity for general screening compared to MRI. - It is particularly useful for differentiating between **cystic and solid masses** and detecting implant ruptures but is not the gold standard for comprehensive screening in augmented breasts.
Question 2: On MRI, which of the following shows diffusion restriction?
- A. Ependymoma
- B. Meningioma
- C. Medulloblastoma (Correct Answer)
- D. Germinoma
Explanation: ***Medulloblastoma*** - **Medulloblastomas** are highly cellular tumors, leading to **restricted diffusion** on MRI due to the dense packing of cells and reduced extracellular space. - This feature helps distinguish them from other posterior fossa tumors like ependymomas and pilocytic astrocytomas. - They are the **most common malignant posterior fossa tumor in children** and show bright signal on DWI with low ADC values. *Ependymoma* - **Ependymomas** typically show **facilitated diffusion** or no significant diffusion restriction on MRI due to their less cellular nature and higher water content. - They often arise from the ependyma lining the ventricles and can have heterogeneous signal characteristics. - Variable ADC values are seen, generally higher than medulloblastomas. *Meningioma* - **Meningiomas** usually do not show significant **diffusion restriction**; instead, they have an appearance reflecting their fibrous and vascular nature. - They tend to be extra-axial, dural-based tumors that enhance homogenously. - ADC values are typically elevated compared to highly cellular tumors. *Germinoma* - **Germinomas** are also highly cellular tumors and **do show diffusion restriction** similar to medulloblastomas. - However, they are typically located in the **pineal or suprasellar regions**, not the posterior fossa. - In this context, **medulloblastoma** is the best answer as the classic example of a diffusion-restricting posterior fossa tumor commonly tested in examinations.
Question 3: Investigation of choice for leptomeningeal carcinomatosis:
- A. Gd enhanced MRI (Correct Answer)
- B. CT scan
- C. SPECT
- D. PET
Explanation: ***Gd enhanced MRI*** - **Gadolinium-enhanced MRI** is the investigation of choice for **leptomeningeal carcinomatosis** as it can visualize the subtle nodular or linear enhancement along the leptomeninges, indicating tumor dissemination. - It offers superior **soft tissue contrast** and spatial resolution compared to CT, enabling detection of small lesions and accurate mapping of disease extent. *CT scan* - A **CT scan** has limited sensitivity for detecting leptomeningeal involvement due to poor contrast resolution of soft tissues and the dura/arachnoid spaces. - It might show hydrocephalus or large tumor deposits, but subtle leptomeningeal enhancement is often missed. *SPECT* - **Single photon emission computed tomography (SPECT)** is primarily used for functional imaging and is not the investigation of choice for anatomical visualization of leptomeningeal carcinomatosis. - Its resolution is too low to detect the fine structural changes associated with leptomeningeal spread. *PET* - **Positron emission tomography (PET)**, often combined with CT, identifies metabolically active tumor cells and can detect diffuse metastatic disease. - While useful for overall cancer staging and identifying primary lesions, it is less effective than gadolinium-enhanced MRI for directly visualizing the morphology and enhancement patterns of leptomeningeal carcinomatosis due to limited spatial resolution in the CSF spaces.
Question 4: Radiation-induced necrosis can be diagnosed by:
- A. MRI
- B. CT
- C. PET
- D. Biopsy (Correct Answer)
Explanation: ***Biopsy*** - A **biopsy** is the definitive diagnostic method for radiation-induced necrosis, allowing for histological examination of tissue to confirm necrosis and rule out residual or recurrent tumor. [1], [2] - It provides a direct view of cellular changes, identifying **necrosis, atypical cells**, and ruling out **malignancy**. *MRI* - While **MRI** can show structural changes indicative of necrosis (e.g., mass effect, edema), it often cannot definitively differentiate between **radiation necrosis** and **tumor recurrence.** [2] - It often shows **T1 hypointensity** and **T2 hyperintensity**, but these findings are not specific. *CT* - **CT scans** are useful for detecting gross changes like **mass effect** and **edema** but have limited sensitivity for distinguishing necrosis from tumor recurrence. - It may show **low-density lesions** but lacks the resolution and specificity for precise diagnosis. *PET* - **PET scans** measure metabolic activity and can help distinguish between **tumor recurrence** (high uptake) and **radiation necrosis** (low uptake) in some cases. - However, false positives can occur, as some inflammatory processes in necrosis can also show increased uptake, making it **less definitive** than a biopsy. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1307-1308. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 340-341.
Question 5: Distant bone metastases can be best detected by which of the following imaging techniques?
- A. Bone scan (Correct Answer)
- B. CT
- C. Intravenous venogram
- D. PET scan
Explanation: ***Bone scan*** - A **bone scan** is highly sensitive for detecting **osteoblastic activity**, which is characteristic of most bone metastases. - It involves injecting a **radioactive tracer** (usually technetium-99m methylene diphosphonate) that accumulates in areas of increased bone turnover, making it excellent for surveying the entire skeletal system. *PET scan* - While a **PET scan** (Positron Emission Tomography) can detect bone metastases, especially with **FDG-PET**, it is generally more expensive and may not be as sensitive for purely **osteoblastic lesions** as a bone scan. - Its primary role is often in assessing metabolic activity of the primary tumor and other distant soft tissue metastases. *CT* - **CT scans** (Computed Tomography) are excellent for assessing bone anatomy, cortical destruction, and soft tissue involvement, but they are generally less sensitive for detecting early or widespread **osseous metastatic disease** compared to a bone scan. - CT provides detailed anatomical information but may miss early **marrow involvement** that alters bone metabolism. *Intravenous venogram* - An **intravenous venogram** is an imaging technique used to visualize veins, primarily for detecting **thrombosis** or venous insufficiency. - It has no role in the detection of **bone metastases**, as it provides no information about bone structure or metabolic activity.
Question 6: MUGA scan is not useful in:
- A. Stroke volume
- B. Regional wall perfusion (Correct Answer)
- C. Left ventricular ejection fraction
- D. Regional wall motion
Explanation: ***Regional wall perfusion*** - A MUGA scan assesses **ventricular function** through blood pool imaging, evaluating wall motion and ejection fraction. - It does not directly visualize or quantify myocardial perfusion, which is the flow of blood through the coronary arteries to the heart muscle. *Stroke volume* - A MUGA scan accurately measures **end-diastolic volume** and **end-systolic volume**, from which stroke volume (EDV – ESV) can be calculated. - This parameter directly reflects the amount of blood pumped out by the ventricle with each beat. *Left ventricular ejection fraction* - The MUGA scan is considered a gold standard for calculating **left ventricular ejection fraction** (LVEF), a key indicator of cardiac pump function. - It uses a count-based method from gated blood pool images to determine the percentage of blood ejected from the left ventricle. *Regional wall motion* - MUGA scans are highly effective in assessing **regional wall motion abnormalities**, identifying areas of **hypokinesis**, **akinesis**, or **dyskinesis**. - This is crucial for diagnosing and monitoring conditions like myocardial ischemia or infarction, and is a primary utility of the scan.
Question 7: In a child, non-functioning kidney is best diagnosed by:
- A. Ultrasonography
- B. IVU
- C. Creatinine clearance
- D. DTPA renogram (Correct Answer)
Explanation: ***DTPA renogram*** - A **DTPA (diethylenetriamine pentaacetic acid) renogram** is a nuclear medicine study that assesses **renal blood flow**, **glomerular filtration**, and urinary drainage. It directly measures the function of each kidney by quantifying tracer uptake and excretion, making it ideal for diagnosing a non-functioning kidney in a child. - The test provides information on the **relative function** of each kidney and outflow obstruction, which is crucial for determining if a kidney is truly non-functioning rather than just poorly visualized. *Ultrasonography* - While ultrasound can visualize the **anatomy** of the kidney (size, shape, presence of hydronephrosis), it does not directly assess renal function. - It may show a small, atrophic, or poorly developed kidney, but cannot definitively determine if it is non-functioning without functional studies. *IVU (Intravenous Urogram)* - An **IVU** relies on the kidneys' ability to excrete contrast material, which is visualized by X-ray. If a kidney is non-functioning, it will not excrete the contrast, leading to non-visualization. - However, IVU exposes the child to **radiation** and **iodinated contrast**, and newer, safer, and more precise functional studies like renograms are preferred, especially in pediatric cases where radiation exposure should be minimized. *Creatinine clearance* - **Creatinine clearance** is a measure of overall **glomerular filtration rate (GFR)** for both kidneys combined. - It does not provide information on the individual function of each kidney, so it cannot diagnose a non-functioning unilateral kidney.
Question 8: Tc-labeled RBCs are used for all except:
- A. Liver adenoma (Correct Answer)
- B. LV function
- C. GI bleeding
- D. Liver hemangioma
Explanation: ***Liver adenoma*** - Tc-labeled RBCs are primarily used to highlight a specific type of tissue or process. **Liver adenomas** do not typically show an affinity for **Tc-labeled RBCs**, as they are benign epithelial tumors with a different vascular composition. - While adenomas can be vascular, they do not inherently contain the **vascular pooling** or blood volume characteristics that would be specifically targeted by **Tc-labeled RBCs** for diagnostic imaging. *LV function* - **Tc-labeled RBCs** (or Tc-99m-pertechnetate) are commonly used in **gated blood pool imaging** (MUGA scan) to assess **left ventricular (LV) function**, including **ejection fraction** and wall motion abnormalities. - This technique directly visualizes the blood pool within the cardiac chambers, making it suitable for assessing functional parameters of the heart. *GI bleeding* - **Tc-labeled RBCs** are a standard imaging agent for detecting and localizing **active gastrointestinal (GI) bleeding**, especially when the bleeding rate is intermittent or slow. - The labeled RBCs extravasate at the site of hemorrhage, creating a 'hot spot' that can be identified over time. *Liver hemangioma* - **Tc-labeled RBCs** are highly effective in diagnosing **liver hemangiomas**, which are benign vascular tumors composed of large, dilated blood vessels. - These lesions show characteristic uptake and retention of **labeled RBCs** due to their slow blood flow and large intravascular space, appearing as early peripheral enhancement with subsequent centripetal filling.
Question 9: CD40 deficiency in a person signifies?
- A. IgG increase
- B. T cell absent
- C. IgM increase (Correct Answer)
- D. B cell absent
Explanation: ***IgM increase*** - A deficiency in **CD40**, or its ligand **CD40L** (found on T helper cells), disrupts **T-cell-dependent B cell activation** and **class switching**. - Without proper signaling through CD40/CD40L, B cells cannot undergo **isotype switching** from **IgM** to IgG, IgA, or IgE, leading to elevated IgM levels and deficiencies in other antibody classes. *IgG increase* - **IgG levels** would likely be **decreased** in CD40 deficiency due to the impaired ability of B cells to undergo **class switching** from IgM to other antibody isotypes. - The primary role of CD40/CD40L interaction is to facilitate this class switching process. *T cell absent* - **CD40 deficiency** does not directly cause the absence of **T cells**; rather, it affects the ability of T cells to adequately activate B cells. - T-cell absence or severe dysfunction would be indicative of a different primary immunodeficiency, such as **SCID (Severe Combined Immunodeficiency)**. *B cell absent* - **CD40 deficiency** does not result in the absence of **B cells**; B cells are present but are dysfunctional in terms of antibody class switching. - Conditions like **X-linked agammaglobulinemia (XLA)** are characterized by the absence or severe deficiency of B cells.
Question 10: Thiamine deficiency is assessed by:
- A. Serum thiamine level
- B. RBC thiamine levels
- C. Erythrocyte transketolase activity (Correct Answer)
- D. RBC Glutathione reductase
Explanation: ***Erythrocyte transketolase activity*** - This is the **most reliable functional assay** for thiamine deficiency, as thiamine pyrophosphate (TPP) is a crucial cofactor for the enzyme **transketolase**. - A significant increase in transketolase activity after the addition of TPP *in vitro* indicates a deficiency, demonstrating the enzyme's reliance on exogenous thiamine. *Serum thiamine level* - **Serum thiamine levels** can fluctuate and do not accurately reflect the body's thiamine stores or functional status, as most thiamine is intracellular. - This measurement may be normal even in cases of functional deficiency or tissue depletion. *RBC thiamine levels* - While red blood cell (RBC) thiamine levels provide a better estimate of tissue stores compared to serum levels, they are **still less sensitive** than direct functional assays like transketolase activity. - RBC thiamine measurements do not directly assess the functional impact of thiamine deficiency on metabolic pathways. *RBC Glutathione reductase* - **Glutathione reductase** activity is used to assess **riboflavin (vitamin B2) deficiency**, not thiamine. - Riboflavin in its coenzyme form, **flavin adenine dinucleotide (FAD)**, is a necessary cofactor for glutathione reductase.
Want unlimited practice?
Get full access to all questions, explanations, and performance tracking.
Start For Free