INI-CET 2025 — Radiology
8 Previous Year Questions with Answers & Explanations
Which investigation is contraindicated in pregnancy?
Which of the following is the investigation of choice for spinal TB?
Based on the provided X-ray image, identify the type of thyroid malignancy.
Eye of the tiger appearance on MRI is associated with:
Honda or H sign on STIR MRI is characteristic of which condition?
Identify the investigation modality shown in the image.
What is the most useful investigation for localization of a parathyroid adenoma?
A child presents with seizures. Contrast-enhanced CT reveals a cystic lesion with a dot sign. What is the most likely diagnosis?
INI-CET 2025 - Radiology INI-CET Practice Questions and MCQs
Question 1: Which investigation is contraindicated in pregnancy?
- A. CT scan (Correct Answer)
- B. MRI
- C. Ultrasound
- D. Doppler
Explanation: ***CT scan*** - CT scan utilizes **ionizing radiation**, which carries potential risks including teratogenesis, fetal growth restriction, and childhood malignancy, particularly with high radiation doses (>100 mGy). - CT is **not absolutely contraindicated** but should be **avoided when alternative imaging is available** (e.g., ultrasound or non-contrast MRI). - When medically necessary (e.g., pulmonary embolism, acute appendicitis, severe trauma), CT can be performed with appropriate justification and dose reduction techniques. - Most diagnostic CT scans deliver fetal doses **below the threshold for deterministic effects** (<50 mGy), but the **ALARA principle** (As Low As Reasonably Achievable) applies. - Among the given options, CT carries the **highest radiation risk** and is the investigation most strongly discouraged unless essential. *MRI* - Non-contrast MRI uses **magnetic fields and radio waves** without ionizing radiation, making it **safe for diagnostic purposes** during pregnancy, particularly after the first trimester. - **Gadolinium contrast is contraindicated**, especially in the first trimester, as it crosses the placenta, remains in amniotic fluid, and has been associated with adverse fetal outcomes in some studies. - Non-contrast MRI is increasingly used for neurological, musculoskeletal, and abdominal imaging in pregnancy. *Ultrasound* - Ultrasound is the **safest and preferred** imaging modality in pregnancy, using high-frequency **sound waves** without ionizing radiation. - Essential for routine prenatal care, monitoring fetal growth, anatomical survey, and assessing placental location and amniotic fluid. - No known harmful effects to the fetus when used appropriately. *Doppler* - Doppler is a **safe and specialized type of ultrasound** that measures **blood flow velocity and vascular resistance** (e.g., umbilical artery, middle cerebral artery, uterine artery). - Crucial for evaluating fetal well-being in high-risk pregnancies, particularly in cases of **intrauterine growth restriction (IUGR)**, pre-eclampsia, or suspected fetal anemia. - No contraindication; thermal and mechanical indices should be monitored per safety guidelines.
Question 2: Which of the following is the investigation of choice for spinal TB?
- A. Ultrasound
- B. MRI (Correct Answer)
- C. CT scan
- D. CBNAAT
Explanation: ***MRI*** - **Magnetic Resonance Imaging (MRI)** is the investigation of choice, as it provides excellent visualization of soft tissues, including the **spinal cord**, nerve roots, and early features like **bone marrow edema** and **paraspinal abscesses**. - It can clearly define the extent of the disease, including disc involvement, **epidural space compression**, and neural compromise, which is crucial for surgical planning. *Ultrasound* - **Ultrasound** is primarily used for assessing soft tissue masses and guiding aspirations but has limited ability to image deep structures like the **vertebral column** and spinal canal. - It cannot adequately assess the extent of **bone destruction**, vertebral body involvement, or **intradural pathology** associated with spinal TB. *CT scan* - **CT scan** is superior to conventional radiography for demonstrating **lytic bone destruction**, calcification, and fine bony detail associated with TB. - However, it is less effective than MRI in visualizing **soft tissue involvement**, **early marrow changes**, or the degree of **cord compression**. *CBNAAT* - **CBNAAT (Cartridge-Based Nucleic Acid Amplification Test)** is a **microbiological test** used for the rapid diagnosis of TB and detection of rifampicin resistance. - It requires a **tissue or fluid sample** (e.g., from aspiration or biopsy) and is used for **pathological confirmation**, not as the primary radiological investigation of choice.
Question 3: Based on the provided X-ray image, identify the type of thyroid malignancy.
- A. Papillary carcinoma
- B. Hurthle cell carcinoma
- C. Follicular carcinoma (Correct Answer)
- D. Thyroid lymphoma
Explanation: ***Follicular carcinoma*** - This is the **correct answer** based on the X-ray showing bone metastases. - Follicular carcinoma characteristically spreads via **hematogenous (bloodstream) route** to distant sites, particularly **bones and lungs**. - Bone metastases from thyroid cancer are **most commonly** due to follicular carcinoma, presenting as **lytic lesions** on X-ray. - Follicular carcinoma accounts for 10-15% of thyroid cancers but is responsible for the majority of thyroid cancer bone metastases. *Incorrect: Papillary carcinoma* - Although papillary carcinoma is the **most common thyroid malignancy** (80% of cases), it predominantly spreads via **lymphatic route** to regional lymph nodes. - Distant hematogenous metastases to bone are **uncommon** in papillary carcinoma. - When papillary carcinoma does metastasize distantly, lungs are more commonly affected than bones. *Incorrect: Hurthle cell carcinoma* - This is an **aggressive variant of follicular carcinoma** (Hürthle cell or oncocytic variant). - While it can spread hematogenously, it is significantly **rarer** than conventional follicular carcinoma. - It represents only 3-5% of differentiated thyroid cancers. *Incorrect: Thyroid lymphoma* - Primary thyroid lymphoma is a **rare malignancy** typically presenting as a rapidly enlarging neck mass. - Usually occurs in elderly patients with a history of **Hashimoto's thyroiditis**. - Distant bone metastases are **not characteristic** of primary thyroid lymphoma.
Question 4: Eye of the tiger appearance on MRI is associated with:
- A. Pantothenate kinase-associated degeneration (Correct Answer)
- B. Wilson disease
- C. Krabbe disease
- D. Huntington chorea
Explanation: ***Pantothenate kinase-associated degeneration*** - The "eye of the tiger" sign is pathognomonic for **Pantothenate kinase-associated neurodegeneration (PKAN)**, a form of Neurodegeneration with Brain Iron Accumulation (NBIA). - It appears as a central area of high signal intensity (oedema/gliosis) surrounded by a rim of low signal intensity (iron deposition) in the **globus pallidus** on T2-weighted MRI. ***Wilson disease*** - Characterized by **copper deposition** in the liver, brain (e.g., basal ganglia, thalamus), and cornea (**Kayser-Fleischer rings**). - MRI findings typically show increased T2 signal intensity in the putamen, midbrain, and basal ganglia, but do not produce the classic "eye of the tiger" sign. ***Krabbe disease*** - This is a lysosomal storage disease (leukodystrophy) caused by a deficiency of the enzyme **galactocerebrosidase**. - MRI typically shows extensive white matter abnormalities and atrophy, but it is not associated with the **globus pallidus** changes seen in the "eye of the tiger" sign. ***Huntington chorea*** - A progressive brain disorder characterized by prominent atrophy of the **caudate nucleus** and putamen (striatum). - MRI primarily demonstrates severe **caudate atrophy** and is not associated with the characteristic PKAN finding in the globus pallidus.
Question 5: Honda or H sign on STIR MRI is characteristic of which condition?
- A. Multiple myeloma
- B. Sacral insufficiency fracture (Correct Answer)
- C. Acute osteomyelitis
- D. Bone marrow edema
Explanation: ***Sacral insufficiency fracture*** - The **Honda sign** (also known as the H sign or butterfly sign) is a characteristic finding on **STIR MRI** of the sacrum, particularly suggestive of a **sacral insufficiency fracture** caused by chronic microtrauma in osteoporotic bone. - It represents bilateral vertical fracture lines through the sacral alae connected by a horizontal fracture line through the body of S3 (or S2/S4), showing **medullary edema**/fracture line hyperintensity on STIR sequences. ***Multiple myeloma*** - Myeloma typically presents on MRI as multiple **focal lesions** (plasmacytomas) or diffuse marrow infiltration, often showing low signal intensity on T1 and variable T2/STIR signals. - While sacral involvement is possible, the classic H sign or Honda sign is not a typical presentation; rather, it often shows **lytic lesions** on plain films/CT. ***Acute osteomyelitis*** - Acute osteomyelitis of the sacrum would show localized **marrow edema** with corresponding T1 hypointensity and contrast-enhancing soft tissue/periosteal reaction. - It is usually unilateral and focal, lacking the characteristic H pattern of stress or insufficiency fractures. ***Bone marrow edema*** - Bone marrow edema is a generalized finding on STIR, indicating pathology such as trauma, infection, tumor infiltration, or avascular necrosis (AVN). - While the H sign is a type of bone marrow edema pattern, the sign itself is specific to a **sacral insufficiency fracture**, not a general edema observation.
Question 6: Identify the investigation modality shown in the image.
- A. X-ray defecogram (Correct Answer)
- B. Barium swallow
- C. MR defecogram
- D. X-ray barium enema
Explanation: ***X-ray defecogram*** - This is a dynamic fluoroscopic study, also known as **evacuation proctography**, which visualizes the rectum and anal canal during the act of defecation. - The images show contrast material within the rectum and its expulsion, allowing for the assessment of anorectal angle, pelvic floor descent, and identification of pathologies like **rectocele**, **enterocele**, or **intussusception**. *Barium swallow* - A barium swallow is a radiographic study used to examine the **upper gastrointestinal tract**, specifically the pharynx, esophagus, and stomach. - The image clearly depicts the pelvic anatomy and rectum, not the upper GI tract. *MR defecogram* - While also a dynamic study of defecation, an MR defecogram utilizes **magnetic resonance imaging (MRI)**, which provides superior soft-tissue contrast and does not use ionizing radiation. - The image shown is a plain radiograph (X-ray), which has a different appearance compared to an MRI scan. *X-ray barium enema* - A barium enema is used to visualize the anatomy of the **entire large intestine** to detect structural abnormalities like polyps, tumors, or diverticula. - It is typically a static study of the colon's morphology, whereas a defecogram is a functional study focused on the dynamics of evacuation.
Question 7: What is the most useful investigation for localization of a parathyroid adenoma?
- A. Sestamibi scan (Correct Answer)
- B. USG
- C. FDG PET
- D. SPECT
Explanation: ***Sestamibi scan*** - **Sestamibi scan (Tc-99m MIBI)** is the **gold standard** for preoperative localization of parathyroid adenomas, with a sensitivity of 80-95% when combined with SPECT. - The radiotracer is taken up by both thyroid and parathyroid tissue, but is **retained longer in the hyperfunctioning parathyroid adenoma**, allowing for differential washout imaging. - Can be enhanced with **SPECT/CT** for better anatomical localization, especially for ectopic glands. *USG* - **Ultrasound (USG)** is a useful anatomical localization tool, particularly for glands in typical locations, but its sensitivity (70-80%) is operator-dependent and limited by gland size/location. - Often used as a **complementary first-line investigation** alongside Sestamibi, especially for guiding needle aspiration or confirming location. - Less sensitive for ectopic or small adenomas compared to Sestamibi. *FDG PET* - **Fluorodeoxyglucose (FDG) PET** is generally not the primary investigation for typical parathyroid adenomas as they do not show intense FDG avidity. - Its use is reserved primarily for **parathyroid carcinoma** localization or in cases where other modalities have failed. - **C-11 Methionine PET** or **F-18 Choline PET** are specialized functional scans with better utility for adenomas than FDG PET, but are less commonly available than Sestamibi. *SPECT* - **SPECT (Single-Photon Emission Computed Tomography)** is an imaging technique that **enhances Sestamibi scan** anatomical resolution (Sestamibi-SPECT or SPECT/CT), especially for small or ectopic adenomas. - SPECT alone without a radiotracer like Sestamibi is not useful; it is the **combination of Sestamibi tracer with SPECT imaging** that provides superior localization. - The option likely refers to this combined modality, but Sestamibi scan (with or without SPECT) remains the most useful overall investigation.
Question 8: A child presents with seizures. Contrast-enhanced CT reveals a cystic lesion with a dot sign. What is the most likely diagnosis?
- A. Tuberculoma
- B. Neurocysticercosis (Correct Answer)
- C. Brain abscess
- D. Cerebral metastasis
Explanation: **Neurocysticercosis (Correct Answer)** - This is the most common parasitic infection of the central nervous system, caused by the larval stage of the pork tapeworm, *Taenia solium* - The contrast-enhanced CT shows a cystic lesion with an eccentric hyperdense focus, which is the **pathognomonic "hole-with-dot" sign**, representing the scolex within the cyst - This imaging finding is highly specific for neurocysticercosis and is commonly seen in endemic areas *Tuberculoma (Incorrect)* - Tuberculomas typically present as single or multiple ring-enhancing lesions, often with a central nidus of calcification, known as the **"target sign"** - They are usually associated with significant vasogenic edema and are more common in patients with a history of tuberculosis or immunosuppression - The "dot sign" is not characteristic of tuberculomas *Brain abscess (Incorrect)* - A brain abscess appears as a well-defined, smooth, ring-enhancing lesion with a central area of necrosis and is typically surrounded by marked vasogenic edema - Clinically, patients often present with fever, headache, and focal neurological deficits - The pathognomonic scolex ("dot sign") is absent in brain abscesses *Cerebral metastasis (Incorrect)* - Metastases typically appear as multiple solid or ring-enhancing lesions located at the gray-white matter junction, often with edema out of proportion to the lesion size - While they can be cystic, the "hole-with-dot" sign is not a feature - Cerebral metastases are less common in children compared to adults with a known primary malignancy