Biochemistry
1 questionsWhich one of the following has the maximum ionization potential?
NEET-PG 2013 - Biochemistry NEET-PG Practice Questions and MCQs
Question 1321: Which one of the following has the maximum ionization potential?
- A. Helium ion (Correct Answer)
- B. Hydrogen ion
- C. Neutron
- D. Helium atom
Explanation: ***Helium ion (He⁺)*** - The question asks about ionization potential, which is the energy required to remove an electron from a species. A **helium ion (He⁺)** has already lost one electron, leaving only one electron bound very tightly to the nucleus with 2 protons. - The **second ionization energy of helium** (removing an electron from He⁺) is the **highest of any element** because the remaining electron experiences the full +2 nuclear charge with no shielding from other electrons. This requires approximately **54.4 eV** of energy. - This is significantly higher than the first ionization energy of any neutral atom, making He⁺ the species with the maximum ionization potential among the given options. *Hydrogen ion (H⁺)* - A **hydrogen ion (H⁺)** is a bare proton with **no electrons remaining**. Since ionization potential refers to the energy needed to remove an electron, and H⁺ has no electrons to remove, this option is technically not applicable. - However, if interpreted as asking about the hydrogen atom (H), its first ionization energy is 13.6 eV, which is much lower than the second ionization energy of helium. *Neutron* - **Neutrons** are subatomic particles with **no electric charge** and are not atoms or ions. They exist within atomic nuclei. - Since ionization potential specifically refers to removing an electron from an atom or ion, and neutrons have no electrons, they **do not have an ionization potential**. This option is not scientifically applicable to the question. *Helium atom (He)* - A neutral **helium atom** has two electrons in its 1s orbital. While helium has the **highest first ionization energy among all neutral atoms** (24.6 eV) due to its stable, filled electron shell, this is still less than half the energy required to remove an electron from He⁺ (54.4 eV). - The first ionization energy of helium is lower than the second ionization energy because removing the first electron from a neutral atom involves less electrostatic attraction than removing an electron from an already positively charged ion.
Internal Medicine
1 questionsWireless capsule endoscopy is done to visualize which of the following condition?
NEET-PG 2013 - Internal Medicine NEET-PG Practice Questions and MCQs
Question 1321: Wireless capsule endoscopy is done to visualize which of the following condition?
- A. Esophageal varices
- B. Gastric carcinoma
- C. Crohn's disease (Correct Answer)
- D. Ulcerative colitis
Explanation: ***Crohn's disease*** - Wireless capsule endoscopy is primarily used to visualize the **small bowel**, which is the main site of involvement in Crohn's disease [3]. - It helps detect **mucosal inflammation**, ulcers, and strictures that may not be accessible by conventional endoscopy [1]. *Esophageal varices* - **Esophageal varices** are best visualized and treated with conventional **esophagogastroduodenoscopy (EGD)**, which allows for direct intervention [2]. - Capsule endoscopy is not the preferred method due to its inability to adequately distend the esophagus or perform therapeutic maneuvers [4]. *Gastric carcinoma* - Diagnosing **gastric carcinoma** requires visualization of the stomach lining, typically achieved through **conventional upper endoscopy** with biopsies [2]. - The capsule may pass too quickly through the stomach or miss subtle lesions, and it cannot obtain tissue samples. *Ulcerative colitis* - **Ulcerative colitis** primarily affects the **colon**, which is visualized using a **colonoscopy** [3]. - While capsule endoscopy can visualize the small bowel, it is not effective for examining the colon due to insufficient imaging of the entire large intestine and lack of biopsy capabilities.
Obstetrics and Gynecology
1 questionsThe 'T' sign is associated with which condition?
NEET-PG 2013 - Obstetrics and Gynecology NEET-PG Practice Questions and MCQs
Question 1321: The 'T' sign is associated with which condition?
- A. Dichorionic twin pregnancy
- B. Monochorionic twin pregnancy (Correct Answer)
- C. Normal singleton pregnancy
- D. Multiple gestation
Explanation: ***Monochorionic twin pregnancy*** - The **'T' sign** on ultrasound is highly suggestive of a **monochorionic twin pregnancy**, indicating shared placenta and a thin inter-twin membrane that meets the chorion at a sharp, T-shaped angle. - This sign identifies the absence of a chorionic plate extending into the inter-twin membrane, distinguishing it from thick-membraned dichorionic pregnancies. *Dichorionic twin pregnancy* - Dichorionic pregnancies typically exhibit the **'lambda' or 'twin peak' sign**, where the chorion extends into the inter-twin membrane, creating a triangular projection, not a 'T' shape. - This sign indicates two separate placentas (or fused but distinct placentas) and two chorions, leading to a thicker inter-twin membrane. *Normal singleton pregnancy* - A normal singleton pregnancy involves only one fetus, and therefore no inter-twin membrane or associated signs like the 'T' or 'lambda' sign are present. - The concept of chorionicity and amnionicity is specific to multiple gestations, particularly twin pregnancies. *Multiple gestation* - While a monochorionic twin pregnancy is a type of multiple gestation, the term "multiple gestation" is too broad and does not specifically identify the **'T' sign**. - Multiple gestation can be either monochorionic or dichorionic, and only monochorionic pregnancies are associated with the 'T' sign.
Radiology
7 questionsWhat is the maximum radiation dose (in Gray) that bone tissue can tolerate?
What is the investigation of choice for whole body imaging in metastatic breast cancer?
On imaging, diffuse axonal injury is characterized by -
What is the CT scan finding in a carotid cavernous sinus fistula?
What is the echogenic lesion size criterion for chronic pancreatitis?
Investigation with least radiation dose in the diagnosis of Meckel's diverticulum is -
What condition is indicated by the double bubble sign on an abdominal X-ray?
NEET-PG 2013 - Radiology NEET-PG Practice Questions and MCQs
Question 1321: What is the maximum radiation dose (in Gray) that bone tissue can tolerate?
- A. 50 Gray (Correct Answer)
- B. 30 Gray
- C. 20 Gray
- D. 40 Gray
Explanation: ***Correct Option: 50 Gray*** - The **maximum radiation tolerance dose** for bone tissue is approximately **50-60 Gray (Gy)** based on radiobiology literature and clinical practice. - Among the given options, **50 Gy** represents the most appropriate threshold for bone tolerance. - According to **Emami et al. tolerance doses** and **QUANTEC guidelines**, bone can typically tolerate up to 60 Gy without significant risk of complications. - Doses approaching or exceeding **60 Gy** carry increased risk of **osteoradionecrosis**, particularly in the **mandible and weight-bearing bones**. - **Clinical significance**: In radiation therapy planning, doses of 50-60 Gy to bone are commonly used therapeutically for tumors involving or adjacent to bone. *Incorrect Option: 40 Gray* - 40 Gy is **below the accepted tolerance threshold** for bone tissue. - This dose is generally **well-tolerated** by bone without significant risk of necrosis or fracture. - Commonly used in palliative and definitive radiation protocols without major bone complications. *Incorrect Option: 30 Gray* - 30 Gy is **considerably below** the tolerance limit for bone. - This dose level is **safe for bone tissue** and carries minimal risk of radiation-induced bone damage. - Often used in palliative treatments with excellent bone tolerance. *Incorrect Option: 20 Gray* - 20 Gy is a **low radiation dose** from the perspective of bone tolerance. - This dose is **highly unlikely** to cause any significant bone damage or complications. - Represents a conservative therapeutic dose well within safety margins.
Question 1322: What is the investigation of choice for whole body imaging in metastatic breast cancer?
- A. Angiography
- B. Venography
- C. Magnetic Resonance Imaging
- D. CT Scan (Correct Answer)
Explanation: ***CT Scan (Correct answer for NEET 2013)*** - **Contrast-enhanced CT scan** was the standard imaging modality for **whole-body staging** in metastatic breast cancer at the time of this exam (2013). - CT offers **excellent spatial resolution** for detecting metastases in **bone, lung, liver, and lymph nodes**. - It is widely available, relatively quick, and provides comprehensive anatomical information. - **Modern Update:** While CT was the standard in 2013, **PET-CT (FDG-PET/CT) is now considered the gold standard** for whole-body staging in metastatic breast cancer due to its combined metabolic and anatomical imaging capabilities. However, PET-CT was not among the options in this historical question. *Magnetic Resonance Imaging* - **MRI** is highly sensitive for specific sites, particularly for **brain metastases** and **bone metastases (especially spine and bone marrow)**. - **Whole-body MRI** protocols are emerging but require longer acquisition times and specialized equipment. - Not ideal as a single first-line modality for comprehensive whole-body staging compared to CT (or modern PET-CT). *Angiography* - **Angiography** is an invasive vascular imaging procedure used to visualize **arterial blood flow**. - It has **no role in routine metastatic screening or staging** of breast cancer. - Reserved for specific indications like preoperative vascular mapping or interventional procedures. *Venography* - **Venography** specifically visualizes **venous structures** and is used to detect venous thrombosis or venous obstructions. - It is **not applicable** for detecting solid organ metastases, bone lesions, or lymph node involvement in cancer staging.
Question 1323: On imaging, diffuse axonal injury is characterized by -
- A. Patchy ill-defined low density lesion mixed with small hyperdensities of petechial hemorrhage
- B. Crescentic extra-axial hematoma
- C. White matter lucencies
- D. Multiple small petechial hemorrhages (Correct Answer)
Explanation: ***Multiple small petechial hemorrhages*** - Diffuse axonal injury (DAI) is characterized on imaging by numerous **small petechial hemorrhages** at the **gray-white matter junction**, **corpus callosum**, and **brainstem**. - These microhemorrhages are the **hallmark imaging finding** and are best visualized on MRI (GRE/SWI sequences), though they can be seen on CT as small hyperdensities. - This is the **most specific** and characteristic finding that defines DAI. *Patchy ill-defined low density lesion mixed with small hyperdensities of petechial hemorrhage* - While this description can be seen in DAI (combining edema with microhemorrhages), it is **less specific** and could represent other entities. - This mixed pattern is more commonly associated with **contusions** where there is more prominent parenchymal injury with larger areas of edema and hemorrhage. - DAI classically shows predominantly **small punctate hemorrhages** rather than larger patchy low-density lesions. *Crescentic extra-axial hematoma* - A crescentic extra-axial collection describes a **subdural hematoma**, which is an entirely separate entity from DAI. - Subdural hematomas are located between the dura and arachnoid membranes, whereas DAI involves direct **axonal shearing injury** within brain parenchyma. *White matter lucencies* - This is a **non-specific finding** that can occur in many conditions including ischemia, demyelination, and chronic small vessel disease. - While DAI can cause white matter edema leading to lucencies, this does not capture the **characteristic petechial hemorrhages** that define the condition on imaging.
Question 1324: What is the CT scan finding in a carotid cavernous sinus fistula?
- A. Enlarged superior ophthalmic vein (Correct Answer)
- B. Enlarged inferior ophthalmic vein
- C. Enlarged superior ophthalmic artery
- D. Enlarged inferior ophthalmic artery
Explanation: ***Enlarged superior ophthalmic vein*** * A carotid cavernous sinus fistula (CCSF) causes **high-pressure arterial blood** to shunt into the **venous system** of the cavernous sinus. * This increased pressure leads to retrograde flow and congestion in the draining veins, most notably the **superior ophthalmic vein**, causing its dilation. *Enlarged inferior ophthalmic vein* * While the inferior ophthalmic vein can also be involved in some cases of CCSF, the **superior ophthalmic vein** is typically more prominent and consistently affected due to its primary drainage pathway. * The inferior ophthalmic vein is less frequently the primary or most notable imaging finding compared to the superior ophthalmic vein. *Enlarged superior ophthalmic artery* * A CCSF involves an abnormal connection between the **carotid artery** (an artery) and the **cavernous sinus** (a venous structure), leading to venous, not arterial, dilation. * Arteries in the orbital region, like the superior ophthalmic artery, would not typically enlarge as a direct result of increased venous pressure in the cavernous sinus. *Enlarged inferior ophthalmic artery* * Similar to the superior ophthalmic artery, the inferior ophthalmic artery is an **arterial structure** and would not enlarge due to a high-flow arteriovenous shunt within the cavernous sinus. * The pathological changes in CCSF are primarily observed in the **venous drainage pathways**.
Question 1325: What is the echogenic lesion size criterion for chronic pancreatitis?
- A. > 2 mm
- B. > 3 mm (Correct Answer)
- C. > 1 mm
- D. > 4 mm
Explanation: ***> 3 mm*** - An echogenic lesion **greater than 3 mm** in size is a diagnostic criterion for **chronic pancreatitis** when observed on ultrasound imaging. - This represents one of the **major features** in ultrasound diagnosis of chronic pancreatitis, particularly when echogenic foci demonstrate acoustic shadowing (suggesting calcifications). - This criterion is part of established diagnostic frameworks and helps differentiate pathological calcifications from minor, non-specific findings. *> 4 mm* - While a **4 mm threshold** would indicate significant findings, the established diagnostic criterion for chronic pancreatitis uses **> 3 mm** as the cutoff. - Using a higher threshold would reduce sensitivity for detecting chronic pancreatitis. *> 2 mm* - A lesion larger than **2 mm** is generally considered below the established diagnostic threshold for **chronic pancreatitis**. - This size may represent early changes or incidental findings that are not yet definitive for diagnosis. *> 1 mm* - A lesion **greater than 1 mm** is too small to be a definitive criterion for **chronic pancreatitis** and could represent minor, non-pathological findings. - Such small echogenic foci lack sufficient specificity for diagnosing chronic pancreatic disease.
Question 1326: Investigation with least radiation dose in the diagnosis of Meckel's diverticulum is -
- A. MRI
- B. CT
- C. Contrast radiography
- D. Technetium -99m scanning (Correct Answer)
Explanation: ***Technetium-99m scanning*** - **Technetium-99m pertechnetate scan** (Meckel's scan) is the **gold standard investigation** for diagnosing Meckel's diverticulum with ectopic gastric mucosa - Among the investigations that can actually **diagnose Meckel's diverticulum**, it has the **lowest radiation dose** (approximately 1-2 mSv) - The radioisotope is specifically taken up by ectopic gastric mucosa, providing both diagnostic utility and relatively low radiation exposure - **Sensitivity: 85-95%** for detecting ectopic gastric mucosa in Meckel's diverticulum - The radiation dose is comparable to a few months of natural background radiation and significantly lower than CT or contrast studies *MRI* - While **MRI uses no ionizing radiation**, it is **not a standard or practical investigation** for diagnosing Meckel's diverticulum - MRI cannot identify ectopic gastric mucosa specifically - It is rarely used in clinical practice for this indication - The question asks about investigation "in the diagnosis" of Meckel's diverticulum, implying a test that is actually used diagnostically *CT* - **Computed Tomography (CT)** delivers a **high radiation dose** (typically 5-10 mSv or more) - While it can identify structural abnormalities, it is not specific for Meckel's diverticulum - Not the first-line investigation for this condition *Contrast radiography* - **Contrast studies** (barium studies) use **moderate ionizing radiation** (3-5 mSv) - Limited utility in diagnosing Meckel's diverticulum as it primarily assesses luminal patency - Cannot identify ectopic gastric mucosa - Lower sensitivity compared to Tc-99m scanning
Question 1327: What condition is indicated by the double bubble sign on an abdominal X-ray?
- A. Duodenal stenosis
- B. Volvulus
- C. All of the options
- D. Duodenal atresia (Correct Answer)
Explanation: ***Duodenal atresia*** - The **double bubble sign** on an abdominal X-ray is pathognomonic for **duodenal atresia**, characterized by two air-filled bubbles: one in the stomach and one in the proximal duodenum, separated by the pylorus. - This congenital anomaly results from a complete obstruction of the duodenum, preventing the passage of air and fluid past this point. *Duodenal stenosis* - While also an obstruction of the duodenum, **duodenal stenosis** is an incomplete obstruction, meaning some gas will pass beyond the duodenum. - This would result in gas being present in the distal bowel, which is not seen with a classic "double bubble" where the bowel distal to the duodenum is gasless. *Volvulus* - **Volvulus** involves the twisting of a loop of intestine, leading to obstruction and potentially ischemia. - While it can cause obstruction, it typically presents with a "corkscrew" appearance on an upper GI series or signs of diffuse bowel distension, not the isolated double bubble. *All of the options* - The double bubble sign is highly specific to **duodenal atresia** due to the complete obstruction it signifies. - Other conditions like duodenal stenosis and volvulus cause different radiological patterns, making this option incorrect.