Principles of cross-sectional imaging US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Principles of cross-sectional imaging. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Principles of cross-sectional imaging US Medical PG Question 1: A 57-year-old man presents to his family physician for a routine exam. He feels well and reports no new complaints since his visit last year. Last year, he had a colonoscopy which showed no polyps, a low dose chest computerized tomography (CT) scan that showed no masses, and routine labs which showed a fasting glucose of 93 mg/dL. He is relatively sedentary and has a body mass index (BMI) of 24 kg/m^2. He has a history of using methamphetamines, alcohol (4-5 drinks per day since age 30), and tobacco (1 pack per day since age 18), but he joined Alcoholics Anonymous and has been in recovery, not using any of these for the past 7 years. Which of the following is indicated at this time?
- A. Colonoscopy
- B. Chest computerized tomography (CT) scan (Correct Answer)
- C. Abdominal ultrasound
- D. Chest radiograph
- E. Fasting glucose
Principles of cross-sectional imaging Explanation: ***Chest computerized tomography (CT) scan***
- This patient has a significant **smoking history** (1 pack per day since age 18 = **39 pack-years**) and is 57 years old, placing him in a high-risk group for **lung cancer**.
- Annual low-dose CT screening for lung cancer is recommended for individuals aged 50-80 with a 20 pack-year smoking history who currently smoke or have quit within the past 15 years.
- He meets all criteria: age 57, 39 pack-years, and quit only 7 years ago (within the 15-year window).
- Since he had screening **last year** with no masses, this year's visit represents the appropriate time for his **annual follow-up screening**.
*Colonoscopy*
- The patient had a colonoscopy last year with **no polyps**, suggesting he is at average risk for colorectal cancer.
- For individuals at average risk with normal findings, repeat screening colonoscopy is typically recommended every **10 years** (or every 5 years for flexible sigmoidoscopy), not annually.
*Abdominal ultrasound*
- One-time abdominal ultrasound screening for **abdominal aortic aneurysm (AAA)** is recommended for men aged 65-75 who have ever smoked.
- This patient is only 57 years old and does not yet meet the age criteria for AAA screening.
*Chest radiograph*
- While a chest radiograph can identify some lung abnormalities, a **low-dose CT scan** is far more sensitive and specific for detecting early-stage lung cancer in high-risk populations.
- Chest radiography is **not recommended** as a screening tool for lung cancer due to its lower sensitivity and lack of mortality benefit in trials.
*Fasting glucose*
- The patient had a **normal fasting glucose** of 93 mg/dL last year, and there are no new symptoms suggestive of diabetes.
- For asymptomatic adults with normal glucose, diabetes screening is typically repeated every **3 years**.
- Annual re-screening is not indicated without new risk factors or symptoms.
Principles of cross-sectional imaging US Medical PG Question 2: During a surgical procedure to repair an abdominal aortic aneurysm, the surgeon must be careful to avoid injury to which of the following arterial structures that originates near the level of the renal vessels?
- A. Left renal artery (Correct Answer)
- B. Celiac trunk
- C. Right renal artery
- D. Superior mesenteric artery
Principles of cross-sectional imaging Explanation: ***Left renal artery***
- The **left renal artery** arises from the aorta usually just below the superior mesenteric artery, making it susceptible to injury during an **abdominal aortic aneurysm (AAA) repair** if the aneurysm extends proximally.
- Its proximity to the typical location of AAA, often near or involving the **infrarenal aorta**, necessitates careful identification and protection during clamping or graft placement.
*Celiac trunk*
- The **celiac trunk** originates higher up from the aorta, typically at the level of **T12-L1 vertebrae**, well above the common infrarenal AAA repair site.
- While important, it is generally less directly threatened during a typical infrarenal AAA repair compared to arteries immediately adjacent to or within the aneurysm sac.
*Right renal artery*
- The **right renal artery** also originates from the aorta near the level of the renal veins, but it is typically located more posteriorly and usually passes behind the inferior vena cava.
- Although it can be at risk, the left renal artery's course is often more anterior and directly in the field of dissection for the **aortic neck** during AAA repair.
*Superior mesenteric artery*
- The **superior mesenteric artery (SMA)** originates from the aorta proximal to the renal arteries, typically around the L1 vertebral level.
- While crucial, its origin is usually cephalad to the infrarenal aneurysm neck, making it generally less prone to direct injury during infrarenal AAA repair, though flow must be monitored.
Principles of cross-sectional imaging US Medical PG Question 3: A 36-year-old male is taken to the emergency room after jumping from a building. Bilateral fractures to the femur were stabilized at the scene by emergency medical technicians. The patient is lucid upon questioning and his vitals are stable. Pain only at his hips was elicited. Cervical exam was not performed. What is the best imaging study for this patient?
- A. AP and lateral radiographs of hips
- B. Lateral radiograph (x-ray) of hips
- C. Magnetic resonance imaging (MRI) of hips, knees, lumbar, and cervical area
- D. Anterior-posterior (AP) and lateral radiographs of hips, knees, lumbar, and cervical area
- E. Computed tomography (CT) scan of cervical spine, hips, and lumbar area (Correct Answer)
Principles of cross-sectional imaging Explanation: ***Computed tomography (CT) scan of cervical spine, hips, and lumbar area***
- In **high-energy trauma** (fall from height), a CT scan is the **gold standard** for evaluating the **spine and pelvis**, providing detailed cross-sectional images superior to plain radiographs.
- Since the **cervical exam was not performed**, cervical spine imaging is **mandatory** per ATLS (Advanced Trauma Life Support) protocols. High-energy falls carry significant risk of **cervical spine injury** even without obvious neurological symptoms.
- CT allows comprehensive assessment of **hip fractures, pelvic injuries, and the entire spine** (cervical, thoracic, lumbar), identifying both obvious and **subtle fractures** that may be missed on plain films.
- This approach provides the most **efficient and thorough evaluation** in the acute trauma setting, allowing for appropriate surgical planning and ruling out life-threatening spinal instability.
*AP and lateral radiographs of hips*
- Plain radiographs provide **limited detail** and may **miss subtle fractures**, particularly in complex areas like the pelvis and acetabulum.
- This option **fails to address cervical spine clearance**, which is essential in all high-energy trauma patients, especially when cervical exam has not been performed.
- Radiographs are insufficient for **comprehensive trauma evaluation** after a fall from height.
*Lateral radiograph (x-ray) of hips*
- A single lateral view is **grossly insufficient** for evaluating hip and pelvic fractures, providing only a **two-dimensional perspective** that can miss significant injuries.
- This option **completely neglects spinal evaluation**, which is dangerous in an uncleared trauma patient with a high-energy mechanism.
*Magnetic resonance imaging (MRI) of hips, knees, lumbar, and cervical area*
- While MRI excels at evaluating **soft tissues, ligaments, and bone marrow**, it is **not the initial imaging modality** for acute bony trauma due to longer scan times and lower sensitivity for acute fractures compared to CT.
- MRI is **time-consuming and impractical** in the emergency setting for initial fracture assessment, potentially delaying definitive treatment.
- CT is superior for evaluating **acute skeletal injuries** in the trauma bay.
*Anterior-posterior (AP) and lateral radiographs of hips, knees, lumbar, and cervical area*
- Multiple plain radiographs have **limited sensitivity** for complex or non-displaced fractures, particularly in the **spine and pelvis**, making them inadequate for high-energy trauma evaluation.
- Obtaining multiple radiographic views requires **numerous patient repositionings**, which risks further injury if **spinal instability** is present.
- Plain films provide significantly **less diagnostic information** than CT scanning for trauma assessment.
Principles of cross-sectional imaging US Medical PG Question 4: A 65-year-old Caucasian man visits the nephrology outpatient clinic for a follow-up appointment. He was previously diagnosed with stage G3a chronic kidney disease (CKD) and albuminuria stage A2. He follows strict dietary recommendations and takes enalapril. He has a history of benign prostatic hyperplasia which has been complicated by urinary tract obstruction. His vitals are stable, and his blood pressure is within the recommended limits. His most recent laboratory studies are as follows:
Serum sodium 140 mEq/L
Serum potassium 5.8 mEq/L
Serum chloride 102 mEq/L
Serum phosphate 4.0 mg/dL
Hemoglobin 11.5 mg/dL
Albumin excretion rate (AER) 280 mg/day
Which of the following is the best strategy in the management of this patient?
- A. Observation
- B. Addition of furosemide
- C. Addition of patiromer (Correct Answer)
- D. Addition of sevelamer
- E. Removal of enalapril
Principles of cross-sectional imaging Explanation: ***Addition of patiromer***
- The patient has **hyperkalemia** (serum potassium 5.8 mEq/L) which is exacerbated by his enalapril use and CKD; **patiromer** is a potassium binder that can effectively lower serum potassium without necessitating discontinuation of essential medications like ACE inhibitors.
- Patiromer is a good choice for chronic hyperkalemia in patients with **CKD** who require drugs that can increase potassium, such as **ACE inhibitors**, helping to maintain the benefits of these renoprotective agents.
*Observation*
- The patient's **serum potassium is elevated at 5.8 mEq/L**, which is a potentially dangerous level requiring intervention, not just observation.
- Hyperkalemia can lead to **life-threatening cardiac arrhythmias**, necessitating active management rather than a wait-and-see approach.
*Addition of furosemide*
- While furosemide can promote potassium excretion, its primary role is fluid removal and relief of congestion, and it may not be sufficient to address significant hyperkalemia in a patient on an **ACE inhibitor** with CKD.
- Furosemide would not directly counteract the potassium-retaining effect of **enalapril** as effectively as a potassium binder would, especially in the context of controlled blood pressure and no overt fluid overload.
*Addition of sevelamer*
- **Sevelamer** is a phosphate binder primarily used to manage **hyperphosphatemia** in CKD patients, which this patient does not have (serum phosphate 4.0 mg/dL is within normal limits).
- Its mechanism of action does not involve **potassium binding** or excretion, making it ineffective for the patient's hyperkalemia.
*Removal of enalapril*
- **Enalapril** is crucial for its **renoprotective effects**, including reducing proteinuria (AER 280 mg/day) and controlling blood pressure in CKD patients.
- Discontinuing enalapril would remove these benefits and could worsen kidney disease progression and proteinuria, while there are other strategies (like **patiromer**) to manage the side effect of hyperkalemia.
Principles of cross-sectional imaging US Medical PG Question 5: A patient undergoes spinal surgery at the L4-L5 level. During the procedure, which of the following ligaments must be divided first to access the spinal canal?
- A. Nuchal ligament
- B. Anterior longitudinal ligament
- C. Supraspinous ligament
- D. Ligamentum flavum (Correct Answer)
Principles of cross-sectional imaging Explanation: ***Ligamentum flavum***
- The **ligamentum flavum** connects the laminae of adjacent vertebrae and forms the posterior boundary of the spinal canal, making it the first ligament encountered anteriorly after removing the lamina.
- While performing a posterior approach **laminectomy**, the ligamentum flavum is typically divided or removed to gain access to the neural structures within the spinal canal.
*Nuchal ligament*
- The **nuchal ligament** is located in the cervical spine and provides attachment for muscles, extending from the external occipital protuberance to the spinous process of C7.
- It is not present at the **L4-L5 level** and therefore plays no role in lumbar spinal surgery.
*Anterior longitudinal ligament*
- The **anterior longitudinal ligament** runs along the anterior surfaces of the vertebral bodies and intervertebral discs.
- It would be encountered during an **anterior surgical approach** to the spine, not a posterior approach to access the spinal canal.
*Supraspinous ligament*
- The **supraspinous ligament** connects the tips of the spinous processes and is the most superficial ligament posteriorly.
- While it is incised during a posterior approach, it is **superficial to the lamina** and ligamentum flavum; therefore, the lamina and ligamentum flavum must be removed or divided first to access the canal.
Principles of cross-sectional imaging US Medical PG Question 6: A cardiologist is studying how a new virus that infects the heart affects the electrical conduction system of the cardiac myocytes. He decides to obtain electrocardiograms on patients with this disease in order to see how the wave patterns and durations change over time. While studying these records, he asks a medical student who is working with him to interpret the traces. Specifically, he asks her to identify the part that represents initial ventricular depolarization. Which of the following characteristics is most consistent with this feature of the electrocardiogram?
- A. Elevated in patients with full thickness ischemic injury of the heart
- B. Becomes peaked in states of hyperkalemia
- C. Becomes prominent in states of hypokalemia
- D. Normal duration defined as less than 120 milliseconds (Correct Answer)
- E. Normal duration defined as less than 200 milliseconds
Principles of cross-sectional imaging Explanation: ***Normal duration defined as less than 120 milliseconds***
- The question asks for the representation of **initial ventricular depolarization**, which corresponds to the **QRS complex** on an ECG.
- The normal duration of the **QRS complex** is typically less than **0.12 seconds (120 milliseconds)**, reflecting efficient ventricular depolarization.
*Elevated in patients with full thickness ischemic injury of the heart*
- This description refers to the **ST segment elevation** seen in **ST-segment elevation myocardial infarction (STEMI)**, which represents myocardial injury, not initial ventricular depolarization.
- While related to cardiac electrical activity, **ST segment elevation** is a consequence of injury and refers to repolarization abnormalities, not the QRS complex itself.
*Becomes peaked in states of hyperkalemia*
- **Peaked T waves** are characteristic of **hyperkalemia**, indicating altered ventricular repolarization, not ventricular depolarization.
- The T wave represents ventricular repolarization, and its morphology changes significantly with potassium imbalances.
*Becomes prominent in states of hypokalemia*
- A **prominent U wave** is sometimes observed in **hypokalemia**, which follows the T wave and is thought to represent repolarization of Purkinje fibers.
- The U wave is distinct from the QRS complex and does not represent initial ventricular depolarization.
*Normal duration defined as less than 200 milliseconds*
- A duration of less than 200 milliseconds (0.20 seconds) typically refers to the normal duration of the **PR interval**, which represents atrial depolarization and conduction through the AV node.
- The **QRS complex** (initial ventricular depolarization) has a shorter normal duration, typically less than 120 milliseconds.
Principles of cross-sectional imaging US Medical PG Question 7: An investigator is studying the relationship between fetal blood oxygen saturation and intrauterine growth restriction using MRI studies. The magnetic resonance transverse relaxation time (T2) is inversely related to the concentration of deoxyhemoglobin so that high concentrations of deoxyhemoglobin produce a low signal intensity on T2-weighted MRI. In a normal fetus, the T2 signal is most likely to be the highest in which of the following vessels?
- A. Descending aorta
- B. Superior vena cava
- C. Ductus venosus (Correct Answer)
- D. Pulmonary veins
- E. Right atrium
Principles of cross-sectional imaging Explanation: ***Ductus venosus***
- The **ductus venosus** shunts highly oxygenated blood directly from the **umbilical vein** to the inferior vena cava, bypassing the liver.
- This vessel carries the most oxygen-rich blood in the fetal circulation (lowest deoxyhemoglobin concentration), resulting in the **highest T2 signal intensity**.
*Descending aorta*
- The descending aorta receives a mixture of oxygenated blood from the left ventricle and deoxygenated blood from the **pulmonary artery** via the **ductus arteriosus**.
- This mixing reduces its overall oxygen saturation compared to the umbilical vein and ductus venosus.
*Superior vena cava*
- The superior vena cava carries **deoxygenated blood** from the upper body and head back to the right atrium.
- This vessel has a low oxygen saturation and high deoxyhemoglobin concentration, leading to a **low T2 signal**.
*Pulmonary veins*
- In a normal fetal circulation, the **lungs are not fully functional**, and pulmonary blood flow is relatively low.
- The pulmonary veins carry only a small amount of moderately oxygenated blood returning from the developing lungs, which is significantly less oxygenated than blood in the ductus venosus.
*Right atrium*
- The right atrium receives **mixed blood** from both the superior and inferior vena cava.
- While it receives some oxygenated blood from the inferior vena cava via the ductus venosus, this is diluted by deoxygenated blood, resulting in lower oxygen saturation than the blood within the ductus venosus itself.
Principles of cross-sectional imaging US Medical PG Question 8: A CT scan of the abdomen reveals a mass in the pancreatic uncinate process. Which of the following structures is most likely to be compressed by this mass?
- A. Common bile duct
- B. Portal vein
- C. Splenic vein
- D. Superior mesenteric vein (Correct Answer)
Principles of cross-sectional imaging Explanation: ***Superior mesenteric vein***
- The **uncinate process** of the pancreas hooks around the **superior mesenteric vessels**. Therefore, a mass in this region would most directly compress the **superior mesenteric vein (SMV)** and artery (SMA).
- Compression of the SMV can lead to **venous outflow obstruction** from the small intestine, potentially causing **bowel ischemia** or edema.
*Common bile duct*
- The **common bile duct** passes through the **head of the pancreas**, not typically the uncinate process.
- Compression of the common bile duct would more commonly be associated with masses in the **head of the pancreas**, leading to **jaundice**.
*Portal vein*
- The **portal vein** is formed by the union of the **splenic vein** and the **superior mesenteric vein**, generally posterior to the neck of the pancreas.
- While pancreatic masses can affect the portal vein, a mass specifically in the uncinate process would more directly impinge on the SMV before significantly affecting the main portal vein, which is superior and posterior to the uncinate process.
*Splenic vein*
- The **splenic vein** runs along the **posterior aspect of the body and tail of the pancreas**.
- A mass in the uncinate process, located at the inferior margin of the head, is relatively distant from the splenic vein.
Principles of cross-sectional imaging US Medical PG Question 9: A 34-year-old woman presents to her primary care provider after intermittently passing bright pink urine over several days. She is concerned this discoloration is due to blood. Her medical history is unremarkable, she denies being sick in the past weeks and has only taken a couple of diclofenac capsules for pelvic pain associated to her menstrual period. She does not drink alcohol or smoke cigarettes. At the doctor’s office, her blood pressure is 150/90 mm Hg, pulse is 80/min, respiratory rate is 18/min, and temperature is 36.5°C (97.7°F). On physical exam, she has 2+ pitting edema up to her knees. A urinalysis is taken which shows red blood cells, red blood cell casts, and acanthocytes. No proteinuria was detected. Her serum creatinine is 2.4 mg/dL, blood urea nitrogen 42 mg/dL, serum potassium 4.8 mEq/L, serum sodium 140 mEq/L, serum chloride 102 mEq/L. Which of the following is the most appropriate next step in the management of this case?
- A. Discontinuation of NSAID
- B. Fomepizole
- C. Intravenous fluid therapy and electrolyte correction
- D. Noncontrast computed tomography
- E. Renal biopsy (Correct Answer)
Principles of cross-sectional imaging Explanation: ***Renal biopsy***
- The patient presents with **acute nephritic syndrome**, characterized by **hypertension**, **edema**, and **active urine sediment** (RBCs, RBC casts, acanthocytes) indicating glomerular inflammation, despite no overt proteinuria.
- Given the features of rapid progression (elevated creatinine) and the classic findings of nephritic urine, a **renal biopsy** is crucial for establishing the specific diagnosis (e.g., IgA nephropathy, post-infectious glomerulonephritis, rapidly progressive glomerulonephritis) and guiding appropriate immunosuppressive therapy.
*Discontinuation of NSAID*
- While **NSAIDs** can cause acute kidney injury, the presence of **RBC casts** and **acanthocytes** in the urine strongly points towards a **glomerular pathology**, which is not typically caused solely by NSAID use.
- Although NSAIDs should generally be avoided in kidney injury, simply discontinuing them would not address the underlying glomerular disease.
*Fomepizole*
- **Fomepizole** is an antidote used for **ethylene glycol** or **methanol poisoning**, which cause a severe **metabolic acidosis** and often acute kidney injury with oxalate crystals.
- The patient's presentation does not suggest toxic alcohol ingestion; she has no severe acidosis, and the urine sediment points to intrinsic glomerular disease.
*Intravenous fluid therapy and electrolyte correction*
- While the patient has **elevated creatinine** and potential fluid overload (pitting edema), her electrolytes are currently within normal limits, and the initial management should focus on diagnosing the underlying cause of her nephritic syndrome.
- Aggressive fluid administration might worsen her **hypertension** and **edema** in the setting of acute kidney injury with fluid retention.
*Noncontrast computed tomography*
- A **noncontrast CT** is useful for identifying kidney stones, hydronephrosis, or large renal masses as causes of hematuria but would not provide the specific diagnosis for a **glomerular disease** manifesting with RBC casts and acanthocytes.
- It would not show the microscopic changes crucial for diagnosing glomerulonephritis, making it a less appropriate initial step compared to a renal biopsy in this context.
Principles of cross-sectional imaging US Medical PG Question 10: A 74-year-old male is brought to the emergency department 1 hour after he fell from the top of the staircase at home. He reports pain in his neck as well as weakness of his upper extremities. He is alert and immobilized in a cervical collar. He has hypertension treated with hydrochlorothiazide. His pulse is 90/min and regular, respirations are 18/min, and blood pressure is 140/70 mmHg. Examination shows bruising and midline cervical tenderness. Neurologic examination shows diminished strength and sensation to pain and temperature in the upper extremities, particularly in the hands. Upper extremity deep tendon reflexes are absent. Strength, sensation, and reflexes in the lower extremities are intact. Anal sensation and tone are present. Babinski's sign is absent bilaterally. Which of the following is most likely to confirm the cause of this patient's neurologic examination findings?
- A. CT angiography of the neck
- B. MRI of the cervical spine without contrast (Correct Answer)
- C. X-ray of the cervical spine
- D. CT of the cervical spine with contrast
- E. Cervical myelography
Principles of cross-sectional imaging Explanation: ***MRI of the cervical spine without contrast***
- This patient presents with symptoms consistent with **central cord syndrome**, characterized by greater weakness in the upper extremities than the lower extremities, often following a hyperextension injury in older adults with pre-existing cervical spondylosis. **MRI is the gold standard for visualizing soft tissue injuries**, including spinal cord compression, edema, or hemorrhage, which are typical causes of central cord syndrome.
- Given the primary concern for spinal cord injury and the detailed neurological deficits indicating specific cord involvement, **MRI** offers the best resolution for evaluating the extent of cord damage, disc herniation, ligamentous injury, and pre-existing degenerative changes.
*CT angiography of the neck*
- **CT angiography** primarily evaluates the **vascular structures** of the neck (e.g., carotid and vertebral arteries) for dissection, stenosis, or occlusion.
- While vascular injury could occur in trauma, the patient's neurological findings (disproportionate upper extremity weakness, pain and temperature sensation loss) point more directly to **spinal cord pathology** rather than isolated vascular compromise as the primary cause.
*X-ray of the cervical spine*
- **X-rays** are useful for initial screening of **bony fractures** and significant dislocations but offer limited information about soft tissues, such as the spinal cord, ligaments, or intervertebral discs.
- They cannot adequately visualize the spinal cord damage responsible for the patient's specific neurological deficits, making it insufficient for confirming the cause of central cord syndrome.
*CT of the cervical spine with contrast*
- **CT scans** excel at visualizing **bony structures** and acute fractures, but even with contrast, they provide less detail of the **spinal cord parenchyma** and soft tissue ligaments compared to MRI.
- **Contrast** is typically used to highlight vascular structures, inflammatory processes, or tumors, which are not the primary diagnostic concerns suggested by this patient's acute post-traumatic presentation of central cord syndrome.
*Cervical myelography*
- **Myelography** involves injecting contrast into the subarachnoid space, followed by X-ray or CT imaging, to outline the spinal cord and nerve roots.
- While it can identify **spinal cord compression**, it is an **invasive procedure** with risks (e.g., headache, seizures) and has largely been replaced by the non-invasive and superior soft tissue imaging capabilities of MRI, especially in acute trauma.
More Principles of cross-sectional imaging US Medical PG questions available in the OnCourse app. Practice MCQs, flashcards, and get detailed explanations.
