HU is a measure of
Which of the following appears the same on both T1 and T2 weighted MRI sequences?
Which of the following features is used to identify the colon on an X-ray?
Investigation of choice for studying Renal Cortical mass
Rat tail appearance in contrast radiography is seen in?
A polytrauma patient's CT brain shows a crescent-shaped extra-axial collection with a concave inner margin. What is the most likely diagnosis?
Step ladder pattern of gas shadow is seen in
Which of the following techniques uses piezoelectric crystals?
Rim sign in IVP is seen in
Which of the following conditions is least likely to cause posterior scalloping of the vertebrae?
NEET-PG 2012 - Radiology NEET-PG Practice Questions and MCQs
Question 11: HU is a measure of
- A. CT (Correct Answer)
- B. MRI
- C. PET
- D. USG
Explanation: ***Correct Answer: CT*** - HU stands for **Hounsfield Units**, a standardized quantitative scale used exclusively in **computed tomography (CT)** to describe the **radiodensity** of tissues based on **X-ray attenuation**. - On this scale, **water is assigned 0 HU**, air is -1000 HU, and dense bone can be +1000 HU or more. - This allows objective measurement and comparison of tissue densities across different CT scanners and examinations. *Incorrect: MRI* - **Magnetic Resonance Imaging (MRI)** does not use Hounsfield Units. - MRI signal intensity is based on the **magnetic properties of tissues** and local hydrogen proton density, not X-ray attenuation. *Incorrect: PET* - **Positron Emission Tomography (PET)** measures the metabolic activity of cells using **radioactive tracers**. - Its output is typically quantified in **Standardized Uptake Value (SUV)**, not Hounsfield Units. *Incorrect: USG* - **Ultrasound (USG)** imaging uses sound waves to create images of internal body structures. - It measures the **acoustic impedance** of tissues and displays findings in terms of echogenicity, not Hounsfield Units.
Question 12: Which of the following appears the same on both T1 and T2 weighted MRI sequences?
- A. Gall bladder
- B. Fat (Correct Answer)
- C. Kidney
- D. CSF
Explanation: ***Fat*** - On both T1 and T2 weighted MRI sequences, fat appears **bright** (high signal intensity). - This consistent bright signal makes fat a useful internal reference point for signal interpretation. *Gall bladder* - The gall bladder is filled with **bile**, which appears bright on T2-weighted images due to its high water content, but can be variable on T1. - Bile does not maintain consistently the **same signal intensity** as fat on both sequences. *Kidney* - The renal parenchyma typically has **intermediate signal intensity** on both T1 and T2, but its signal characteristics are different from the consistently bright signal of fat. - The signal can vary depending on the specific sequence parameters and hydration status, unlike fat. *CSF* - **Cerebrospinal fluid (CSF)** appears dark (low signal) on T1-weighted images and bright (high signal) on T2-weighted images due to its high water content. - This distinct signal intensity difference between T1 and T2 is contrary to the shared bright appearance of fat on both sequences.
Question 13: Which of the following features is used to identify the colon on an X-ray?
- A. Haustra (Correct Answer)
- B. Valvulae conniventes
- C. String of beads sign
- D. More number of loops
Explanation: ***Haustra (Correct Answer)*** - **Haustra** are sacculations or pouches of the colon created by the uneven contraction of the **taeniae coli** - They are THE characteristic feature that helps distinguish the large bowel from the small bowel on an X-ray - These indentations typically do **not cross the entire width** of the bowel lumen, unlike the valvulae conniventes of the small intestine - Haustra appear as incomplete septations on plain radiographs *Valvulae conniventes (Incorrect)* - **Valvulae conniventes** (also known as plicae circulares) are large, circular folds of the **small intestine** mucosa that project into the lumen - They extend **completely across the lumen** of the small bowel, making them easily distinguishable from haustra which only partially traverse the colon - This is a feature of small bowel, not colon *String of beads sign (Incorrect)* - The "**string of beads sign**" is a **pathological radiographic finding** associated with small bowel obstruction - It refers to multiple small, gas-filled loops of small bowel stacked on top of each other, often with small pockets of fluid or air trapped between the folds, resembling beads on a string - This is not a normal anatomical feature used to identify the colon *More number of loops (Incorrect)* - The number of loops is **not a primary distinguishing feature** between the large and small bowel on an X-ray - While the small intestine generally has more convolutions or loops than the colon, this is a **less reliable and specific sign** compared to the presence of haustra - Haustra remain the gold standard feature for colon identification
Question 14: Investigation of choice for studying Renal Cortical mass
- A. 99mTc DTPA
- B. 53Cr Study
- C. 99mTc DMSA (Correct Answer)
- D. 99mTc Pyrophosphate
Explanation: ***99mTc DMSA*** - **99mTc DMSA** (Technetium-99m dimercaptosuccinic acid) is the radiopharmaceutical of choice for imaging the **renal cortex** and assessing **renal cortical mass** and scarring. - It binds preferentially to the cells of the **renal tubules**, allowing for excellent visualization of cortical tissue. *99mTc DTPA* - **99mTc DTPA** (Technetium-99m Diethylenetriaminepentaacetic acid) is primarily used to assess **glomerular filtration rate (GFR)** and renal blood flow. - It is filtered by the **glomeruli** but not reabsorbed or secreted by the tubules, making it suitable for functional studies rather than morphological assessment of cortical mass. *53Cr Study* - **53Cr** (Chromium-51) is used in studies to measure **red blood cell mass**, survival, or gastrointestinal protein loss. - It has no role in the direct assessment of **renal cortical mass** or function. *99mTc Pyrophosphate* - **99mTc Pyrophosphate** is primarily used to evaluate **myocardial infarction** (hot spots) or detect bone lesions. - It is not indicated for, nor does it provide useful information about, **renal cortical mass**.
Question 15: Rat tail appearance in contrast radiography is seen in?
- A. Carcinoma esophagus
- B. Plummer-Vinson syndrome
- C. Diffuse esophageal spasms
- D. Achalasia cardia (Correct Answer)
Explanation: ***Correct: Achalasia cardia*** - The **"rat tail" or "bird's beak" sign** is the classic radiological appearance of **achalasia cardia** on barium swallow study - Shows **smooth, symmetrical, tapered narrowing** of the distal esophagus with proximal esophageal dilatation - Due to **failure of the lower esophageal sphincter (LES) to relax**, causing functional obstruction - The smooth tapering distinguishes it from irregular narrowing seen in malignancy *Incorrect: Carcinoma esophagus* - Esophageal carcinoma shows **"shouldered lesion"** or **"apple core" appearance** - Characterized by **irregular, shelf-like margins** with abrupt transition - Narrowing is **asymmetric and irregular**, not the smooth tapering of rat tail sign - May show mucosal destruction and filling defects *Incorrect: Plummer-Vinson syndrome* - Shows **postcricoid web** in the upper esophagus on barium swallow - Associated with iron deficiency anemia, glossitis, and increased risk of esophageal cancer - Presents as a thin, web-like membrane rather than distal narrowing *Incorrect: Diffuse esophageal spasms* - Shows **"corkscrew esophagus"** or **"rosary bead" appearance** on barium swallow - Multiple, **simultaneous, non-peristaltic contractions** create segmented appearance - Dynamic finding with normal segments between contractions - Represents uncoordinated muscular activity, not fixed narrowing
Question 16: A polytrauma patient's CT brain shows a crescent-shaped extra-axial collection with a concave inner margin. What is the most likely diagnosis?
- A. EDH
- B. SDH (Correct Answer)
- C. Contusion
- D. Diffuse axonal injury
Explanation: ***SDH*** - The image shows a **crescent-shaped collection** of hemorrhage with a concave inner margin, consistent with a **subdural hematoma** (SDH). - SDHs result from the tearing of **bridging veins** and typically conform to the brain's surface, crossing suture lines but not limited by bony sutures. *EDH* - An **epidural hematoma (EDH)** characteristically appears as a **lenticular** or **biconvex** shape on CT, not crescent-shaped. - EDHs are typically caused by arterial bleeding, often from the **middle meningeal artery**, and are limited by cranial sutures. *Contusion* - A **contusion** is brain tissue bruising that appears as **heterogeneous areas** of hemorrhage and edema within the brain parenchyma itself. - It would not manifest as a distinct extra-axial collection with a smooth, concave margin. *Diffuse axonal injury* - **Diffuse axonal injury (DAI)** involves widespread microscopic damage to axons, often at the gray-white matter junction. - It may appear as *punctate hemorrhages* or **small lesions** at these junctions on CT, but often the CT can be normal, and it would not present as a large extra-axial collection.
Question 17: Step ladder pattern of gas shadow is seen in
- A. Intestinal obstruction (Correct Answer)
- B. Gastric outlet obstruction
- C. Duodenal obstruction
- D. Sigmoid volvulus
Explanation: ***Intestinal obstruction*** - A **step-ladder pattern** of gas shadows is a classic radiological sign seen in **small bowel obstruction** due to dilated, fluid-filled loops of small bowel stacked on top of each other. - This pattern results from the accumulation of gas and fluid proximal to the obstruction, causing dilated bowel loops to arrange horizontally. *Gastric outlet obstruction* - This condition primarily results in a **dilated stomach** with fluid and gas, not typically a step-ladder pattern in the small bowel. - Vomiting is usually a prominent symptom, and imaging would show a large fluid-filled stomach. *Duodenal obstruction* - Causes dilatation of the stomach and duodenum, leading to a "**double-bubble sign**" (dilated stomach and proximal duodenum). - It does not typically produce the extensive, stacked small bowel loops seen in a step-ladder pattern. *Sigmoid volvulus* - Characterized by a distinctive large, dilated loop of sigmoid colon, often described as a "**coffee bean sign**" or an **inverted U-shape**. - This is a large bowel obstruction and does not typically present with a step-ladder pattern of small bowel gas.
Question 18: Which of the following techniques uses piezoelectric crystals?
- A. Ultrasonography (Correct Answer)
- B. NMR imaging
- C. X-ray diffraction
- D. Xeroradiography
Explanation: ***Ultrasonography*** - **Piezoelectric crystals** are the core component of **ultrasound transducers**, which generate and detect ultrasonic waves. - These crystals convert electrical energy into mechanical vibrations (sound waves) and vice-versa, allowing for the creation of images. *NMR imaging* - **NMR imaging** (Nuclear Magnetic Resonance, now commonly known as **MRI**) uses strong magnetic fields and **radiofrequency pulses** to generate images. - It relies on the magnetic properties of atomic nuclei, particularly hydrogen, rather than piezoelectric effects. *X-ray diffraction* - **X-ray diffraction** is a technique used to study the atomic and molecular structure of materials, and it involves the interaction of **X-rays** with the electron clouds of atoms. - It does not involve piezoelectric crystals; instead, it uses an X-ray source and a detector to measure diffracted X-rays. *Xeroradiography* - **Xeroradiography** is an older imaging technique that used **xerographic plates** coated with a photoconductive material (like selenium) to capture X-ray images. - It relies on electrostatic charges and dry development rather than piezoelectric crystals to produce images.
Question 19: Rim sign in IVP is seen in
- A. Hydronephrosis (Correct Answer)
- B. Chronic Pyelonephritis
- C. Renal Cell Carcinoma
- D. Polycystic Kidney Disease
Explanation: ***Hydronephrosis*** - The **rim sign** in IVP (Intravenous Pyelography) refers to the opacification of the renal parenchyma surrounding a dilated pelvicalyceal system, forming a "rim" of contrast. - This sign is characteristic of acute obstruction leading to **hydronephrosis**, where the contrast accumulates in the compressed renal tissue and then slowly excretes into the dilated collecting system, outlining it. *Chronic Pyelonephritis* - Characterized by **focal cortical thinning**, scarring, and clubbing of the calyces, not a rim sign. - The kidney may appear small and irregularly outlined on IVP due to **parenchymal loss**. *Renal Cell Carcinoma* - Often presents as a **mass lesion** that distorts the collecting system, but typically does not cause a rim sign. - May show vascularity on imaging and can cause direct invasion or displacement of renal structures. *Polycystic Kidney Disease* - Involves multiple **cysts** of varying sizes throughout both kidneys, leading to significant renal enlargement and distortion of the collecting system. - The appearance is typically described as a "Swiss cheese" or "moth-eaten" pattern due to the numerous cysts, not a rim sign.
Question 20: Which of the following conditions is least likely to cause posterior scalloping of the vertebrae?
- A. Astrocytoma
- B. Neurofibromatosis
- C. Ependymoma
- D. Aortic aneurysm (Correct Answer)
Explanation: ***Aortic aneurysm*** - An **aortic aneurysm** is located **anterior to the vertebral column** and primarily affects the anterior aspect of the vertebral bodies, causing **anterior scalloping** due to chronic pulsatile erosion, not posterior scalloping. - Posterior scalloping requires intraspinal pathology that expands the spinal canal from within; an aortic aneurysm is extraspinal and anterior, making it the **least likely** cause of posterior scalloping. *Neurofibromatosis* - **Neurofibromatosis** commonly causes posterior vertebral scalloping due to **dural ectasia** (widening of the dural sac) and pressure erosion from expanding neurofibromas within the spinal canal. - This condition is also associated with paraspinal masses, posterior vertebral body erosion, and scoliosis. *Astrocytoma* - An **intramedullary astrocytoma** within the spinal cord can lead to expansion of the cord that causes chronic pressure on the posterior vertebral bodies from within the spinal canal. - This slow-growing intraspinal tumor gradually remodels the bone, causing posterior scalloping. *Ependymoma* - Similar to astrocytoma, an **intramedullary ependymoma** (the most common primary intramedullary tumor in adults) can enlarge the spinal cord, leading to pressure erosion on the posterior vertebral bodies. - This is a characteristic feature of slowly growing intraspinal masses, which cause remodeling of the bony spinal canal.