Nuclear medicine imaging US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Nuclear medicine imaging. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Nuclear medicine imaging US Medical PG Question 1: 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)
Nuclear medicine 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.
Nuclear medicine imaging US Medical PG Question 2: A 35-year-old woman is presenting for a general wellness checkup. She is generally healthy and has no complaints. The patient does not smoke, drinks 1 alcoholic drink per day, and exercises 1 day per week. She recently had silicone breast implants placed 1 month ago. Her family history is notable for a heart attack in her mother and father at the age of 71 and 55 respectively. Her father had colon cancer at the age of 70. Her temperature is 99.0°F (37.2°C), blood pressure is 121/81 mmHg, pulse is 77/min, respirations are 14/min, and oxygen saturation is 98% on room air. Physical exam is unremarkable. Which of the following is the most appropriate initial step in management?
- A. Alcohol cessation
- B. Colonoscopy at age 60
- C. Mammography at age 50
- D. Colonoscopy at age 40 (Correct Answer)
- E. Mammography now
Nuclear medicine imaging Explanation: ***Colonoscopy at age 40***
- This patient has a **first-degree relative (father) diagnosed with colorectal cancer at age 70**, which increases her risk compared to the average population.
- Current **USPSTF and ACS guidelines** recommend that individuals with a first-degree relative diagnosed with colorectal cancer at **age 60 or older** should begin screening at **age 40** (or 10 years before the age of diagnosis in the relative, whichever is earlier).
- Since her father was diagnosed at age 70, she should start screening at age 40 (which is 10 years earlier and also the recommended age for those with family history).
- At age 35, she does **not yet need** colonoscopy, but should plan for screening in 5 years.
*Colonoscopy now*
- This is **too early** based on current guidelines.
- Immediate colonoscopy at age 35 is not indicated in an asymptomatic patient whose father was diagnosed at age 70.
- Screening at age 40 provides adequate time for early detection while avoiding unnecessary early intervention.
*Colonoscopy at age 60*
- This is **too late** and ignores the increased risk from family history.
- Delaying screening until age 60 would miss the recommended earlier screening window for patients with first-degree relatives with CRC.
*Alcohol cessation*
- The patient drinks **1 alcoholic drink per day**, which is within recommended limits for women.
- While reducing alcohol consumption has general health benefits, this is not the most urgent preventive measure given her family history of colon cancer.
*Mammography now*
- Screening mammography typically begins at **age 40-50** for average-risk women.
- At age 35 with no specific high-risk factors (no BRCA mutation, no strong early-onset breast cancer family history), mammography is not indicated now.
*Mammography at age 50*
- While this may be appropriate for breast cancer screening depending on guidelines followed, it is **not the priority** given her significant family history of colorectal cancer requiring earlier intervention.
Nuclear medicine imaging US Medical PG Question 3: A 65-year-old man with a 40-pack-year smoking history presents with hemoptysis and a persistent cough. Chest CT shows a 3.5 cm centrally located mass in the right main bronchus. Positron emission tomography confirms a malignant nodule. Bronchoscopy with transbronchial biopsy is performed and a specimen sample of the nodule is sent for frozen section analysis. The tissue sample is most likely to show which of the following tumor types?
- A. Carcinoid tumor
- B. Metastasis of colorectal cancer
- C. Small cell lung carcinoma
- D. Large cell carcinoma
- E. Squamous cell carcinoma (Correct Answer)
Nuclear medicine imaging Explanation: ***Squamous cell carcinoma***
- This is the most likely diagnosis given the **central location** in the main bronchus, **heavy smoking history**, and presentation with **hemoptysis**.
- **Squamous cell carcinoma** accounts for 25-30% of lung cancers and characteristically arises in **central/proximal airways**, making it readily accessible by **bronchoscopy**.
- Histologically, it shows **keratin pearls** and **intercellular bridges** on biopsy.
- The **central endobronchial location** and ability to obtain tissue via transbronchial biopsy strongly favor squamous cell over peripheral tumors.
*Carcinoid tumor*
- **Carcinoid tumors** are **neuroendocrine tumors** that can present as central endobronchial masses and cause hemoptysis.
- However, they are typically **slow-growing** with more indolent presentation, and PET scans show **variable uptake** (often less intense than aggressive carcinomas).
- They represent only **1-2% of lung tumors** and occur more commonly in **younger, non-smoking patients**.
*Metastasis of colorectal cancer*
- While lung is a common site for **colorectal metastases**, these typically present as **multiple peripheral nodules** rather than a solitary central endobronchial mass.
- The clinical presentation strongly suggests **primary lung cancer** rather than metastatic disease.
- Without history of colorectal cancer, this is unlikely.
*Small cell lung carcinoma*
- **Small cell lung carcinoma** (SCLC) represents 15% of lung cancers and typically presents as a **large central mass** with early mediastinal involvement.
- However, SCLC is usually **too extensive at presentation** for transbronchial biopsy alone and often requires mediastinoscopy or CT-guided biopsy.
- Histology shows **small cells with scant cytoplasm**, **salt-and-pepper chromatin**, and **oat-cell morphology**.
- While possible, the single accessible endobronchial mass is more characteristic of squamous cell.
*Large cell carcinoma*
- **Large cell carcinoma** is a **diagnosis of exclusion** made when tumors lack features of adenocarcinoma, squamous cell, or small cell differentiation.
- It typically presents as **large peripheral masses** rather than central endobronchial lesions.
- It represents only **10% of lung cancers** and is less common than squamous cell carcinoma in this clinical scenario.
Nuclear medicine imaging US Medical PG Question 4: A 75-year-old female presents to your office with her daughter. The patient states that she feels perfectly well and that she does not know why she is present. The daughter states that over the last several years, the patient has become forgetful and recently forgot her grandchild's name, along with the groceries she was supposed to buy. She was also found lost 10 miles away from her house last week. The daughter also states that the patient has had urinary incontinence over the last few months and has been seeing little children in the morning that are not present. The patient denies any recent falls. Her vitals are normal and her physical exam does not reveal any focal neurological deficits. Her mini-mental status exam is scored 22/30. What is the most accurate test for this patient?
- A. CT angiography of head
- B. CT scan of head
- C. Lumbar puncture
- D. MRI scan of head (Correct Answer)
- E. PET scan of head
Nuclear medicine imaging Explanation: ***MRI scan of head***
- An MRI scan of the head is the **most accurate initial test** to evaluate cognitive decline and rule out structural/reversible causes of dementia.
- This patient's presentation includes **progressive memory loss, disorientation, urinary incontinence, and visual hallucinations** - suggestive of **Lewy Body Dementia (LBD)** or potentially **Normal Pressure Hydrocephalus (NPH)**, though gait disturbance (a key NPH feature) is notably absent.
- MRI provides detailed visualization of **brain atrophy patterns**, **ventricular enlargement** (for NPH), **white matter lesions** (vascular dementia), **hippocampal atrophy** (Alzheimer's), and excludes other reversible causes like **subdural hematoma, tumor, or stroke**.
- **Must be performed first** before any invasive procedures like lumbar puncture.
*CT scan of head*
- A CT scan is useful for acute conditions like **hemorrhage, stroke, or mass lesions**, but it is **significantly less sensitive** than MRI for detecting subtle changes critical for dementia diagnosis.
- Cannot adequately visualize **cortical atrophy, hippocampal volume loss, or subtle white matter changes** that help differentiate dementia subtypes.
- While faster and more accessible, it is not the "most accurate" test for cognitive decline evaluation.
*CT angiography of head*
- CT angiography specifically visualizes **blood vessels** to detect **aneurysms, stenoses, or vascular malformations**.
- While vascular disease can contribute to dementia, this test does not evaluate the **brain parenchyma** or structural changes necessary for diagnosing neurodegenerative conditions.
- Not indicated as the initial test for cognitive impairment without focal vascular symptoms.
*Lumbar puncture*
- Lumbar puncture analyzes **cerebrospinal fluid (CSF)** for biomarkers (**amyloid-beta, tau, alpha-synuclein**), infection, or inflammation.
- It is an **invasive procedure** that should only be performed **after neuroimaging** to rule out increased intracranial pressure, hydrocephalus, or mass lesions.
- While useful for confirming specific dementia diagnoses (e.g., Alzheimer's or LBD biomarkers), it is a **second-line test**, not the initial most accurate diagnostic study.
*PET scan of head*
- PET imaging (FDG-PET or amyloid-PET) measures **metabolic activity** or **specific protein deposits** and is highly specific for certain dementias like **Alzheimer's disease** or **Frontotemporal dementia**.
- It is typically a **specialized second-line test** used after structural imaging when the diagnosis remains unclear.
- **More expensive and less available** than MRI, and not necessary as the initial most accurate test for broad cognitive impairment evaluation.
Nuclear medicine imaging US Medical PG Question 5: A 57-year-old female presents to general gynecology clinic for evaluation of a pelvic mass. The mass was detected on a routine visit to her primary care doctor during abdominal palpation. In the office, she receives a transvaginal ultrasound, which reveals a mass measuring 11 cm in diameter. In the evaluation of this mass, elevation of which tumor marker would be suggestive of an ovarian cancer?
- A. Alpha fetoprotein
- B. CA-125 (Correct Answer)
- C. CA-19-9
- D. Beta-hCG
- E. S-100
Nuclear medicine imaging Explanation: ***CA-125***
- **CA-125** is the most widely used tumor marker for the detection and monitoring of **epithelial ovarian cancer**.
- Elevated levels in a postmenopausal woman with a large pelvic mass are highly suggestive of **ovarian malignancy**.
*Alpha fetoprotein*
- **Alpha fetoprotein (AFP)** is primarily associated with **germ cell tumors** of the ovary (e.g., endodermal sinus tumor) or **hepatocellular carcinoma**.
- It is not typically elevated in common epithelial ovarian cancers, which are more prevalent in older women.
*CA-19-9*
- **CA-19-9** is a tumor marker commonly elevated in **pancreatic cancer** and sometimes in **cholangiocarcinoma** or other gastrointestinal malignancies.
- While it can be elevated in some mucinous ovarian tumors, it is not the primary marker for general ovarian cancer evaluation.
*Beta-hCG*
- **Beta-hCG (Human Chorionic Gonadotropin)** is a marker for **choriocarcinoma** and other **gestational trophoblastic diseases**, as well as some germ cell tumors.
- It would not be expected to be elevated in a typical epithelial ovarian cancer in a 57-year-old female.
*S-100*
- **S-100 protein** is a marker primarily associated with **melanoma** and neural tissue tumors.
- It has no significant role in the diagnosis or monitoring of ovarian cancer.
Nuclear medicine imaging US Medical PG Question 6: A 29-year-old woman presents to a medical office complaining of fatigue, nausea, and vomiting for 1 week. Recently, the smell of certain foods makes her nauseous. Her symptoms are more pronounced in the mornings. The emesis is clear-to-yellow without blood. She has had no recent travel out of the country. The medical history is significant for peptic ulcer, for which she takes pantoprazole. The blood pressure is 100/60 mm Hg, the pulse is 70/min, and the respiratory rate is 12/min. The physical examination reveals pale mucosa and conjunctiva, and bilateral breast tenderness. The LMP was 9 weeks ago. What is the most appropriate next step in the management of this patient?
- A. Beta-HCG levels and a transvaginal ultrasound (Correct Answer)
- B. Beta-HCG levels and a transabdominal ultrasound
- C. Beta-HCG levels and a pelvic CT
- D. Abdominal x-ray
- E. Abdominal CT with contrast
Nuclear medicine imaging Explanation: ***Beta-HCG levels and a transvaginal ultrasound***
- The patient's symptoms (fatigue, nausea, vomiting, morning sickness, breast tenderness, and **amenorrhea** for 9 weeks) strongly suggest **early pregnancy**.
- **Urine or serum beta-HCG** confirms pregnancy, and a **transvaginal ultrasound** is crucial for confirming an **intrauterine pregnancy**, estimating gestational age, and ruling out complications like ectopic pregnancy, especially at this early stage when transabdominal ultrasound might not provide clear images.
*Beta-HCG levels and a transabdominal ultrasound*
- While beta-HCG levels are appropriate, a **transabdominal ultrasound** may not be sufficient to visualize an early intrauterine pregnancy at 9 weeks due to limited resolution compared to transvaginal ultrasound.
- A definitive confirmation of **intrauterine pregnancy** is critical to rule out an **ectopic pregnancy**, which is better achieved with transvaginal imaging in early gestation.
*Beta-HCG levels and a pelvic CT*
- **CT scans** expose the patient to significant **ionizing radiation**, which is **contraindicated in pregnancy** unless absolutely necessary for life-threatening conditions.
- While it could identify some pelvic pathologies, it is **not the primary imaging modality** for confirming or evaluating early pregnancy due to radiation risks and inferior soft tissue resolution for early gestational sacs compared to ultrasound.
*Abdominal x-ray*
- An **abdominal X-ray** involves **ionizing radiation** and offers very limited diagnostic value for early pregnancy, as it cannot visualize the gestational sac, fetus, or fetal heart activity.
- It is **contraindicated** in suspected pregnancy due to the risk of fetal harm.
*Abdominal CT with contrast*
- **Abdominal CT with contrast** involves both **ionizing radiation** and **contrast agents**, both of which pose significant risks to a developing fetus.
- It is an **inappropriate initial step** for suspected pregnancy and offers no specific diagnostic benefits for confirming or characterizing early gestation.
Nuclear medicine imaging US Medical PG Question 7: A 69-year-old man is scheduled to undergo radical retropubic prostatectomy for prostate cancer in 2 weeks. He had a myocardial infarction at the age of 54 years. He has a history of GERD, unstable angina, hyperlipidemia, and severe osteoarthritis in the left hip. He is unable to climb up stairs or walk fast because of pain in his left hip. He had smoked one pack of cigarettes daily for 30 years but quit 25 years ago. He drinks one glass of wine daily. Current medications include aspirin, metoprolol, lisinopril, rosuvastatin, omeprazole, and ibuprofen as needed. His temperature is 36.4°C (97.5°F), pulse is 90/min, and blood pressure is 136/88 mm Hg. Physical examination shows no abnormalities. A 12-lead ECG shows Q waves and inverted T waves in leads II, III, and aVF. His B-type natriuretic protein is 84 pg/mL (N < 125). Which of the following is the most appropriate next step in management to assess this patient's perioperative cardiac risk?
- A. No further testing
- B. 24-hour ambulatory ECG monitoring
- C. Radionuclide myocardial perfusion imaging (Correct Answer)
- D. Treadmill stress test
- E. Resting echocardiography
Nuclear medicine imaging Explanation: ***Radionuclide myocardial perfusion imaging***
- This patient requires **perioperative cardiac risk assessment** before intermediate-risk surgery (radical prostatectomy).
- Key factors include: history of **myocardial infarction**, current cardiac risk factors, and **inability to exercise** due to severe osteoarthritis.
- Since he cannot perform exercise stress testing, **pharmacologic stress testing** with radionuclide myocardial perfusion imaging (using agents like adenosine, dipyridamole, or regadenoson) is the most appropriate test to assess for **inducible myocardial ischemia**.
- This provides functional assessment of coronary perfusion under pharmacologic stress, helping guide perioperative risk stratification and management.
- *Note: The presence of unstable angina would typically require cardiac stabilization first; this question focuses on selecting the appropriate stress test modality for a patient unable to exercise.*
*No further testing*
- This patient has significant cardiac risk factors including **prior MI**, ongoing cardiac medications, and ECG changes suggesting old infarction.
- Proceeding directly to surgery without functional cardiac assessment would be **inappropriate** given his risk profile and the intermediate-risk nature of the planned surgery.
*24-hour ambulatory ECG monitoring*
- Holter monitoring detects arrhythmias and silent ischemic episodes but does not provide **functional capacity assessment** or evaluation of inducible ischemia under stress conditions.
- It is not the primary tool for **perioperative cardiac risk stratification** before major surgery.
*Treadmill stress test*
- The patient's **severe osteoarthritis** prevents him from climbing stairs or walking fast, making him unable to achieve adequate exercise workload for a treadmill stress test.
- This functional limitation makes **exercise stress testing contraindicated**; pharmacologic stress testing is required instead.
*Resting echocardiography*
- Resting echocardiography assesses **baseline left ventricular function**, wall motion abnormalities from prior infarction, and valvular disease.
- While useful for structural assessment, it does **not evaluate for exercise-induced or stress-induced ischemia**, which is critical for perioperative risk assessment in patients with coronary artery disease.
- His normal BNP (84 pg/mL) suggests adequate baseline ventricular function, making functional ischemia assessment more relevant than structural evaluation alone.
Nuclear medicine imaging US Medical PG Question 8: A pathologist receives a patient sample for analysis. Cells in the sample are first labeled with fluorescent antibodies and then passed across a laser beam in a single file of particles. The light scatter and fluorescent intensity of the particles are plotted on a graph; this information is used to characterize the sample. This laboratory method would be most useful to establish the diagnosis of a patient with which of the following?
- A. Ventricular septal defect and facial dysmorphism with low T-lymphocyte count
- B. Painless generalized lymphadenopathy with monomorphic cells and interspersed benign histiocytes on histology
- C. Pancytopenia and deep vein thrombosis with intermittent hemoglobinuria (Correct Answer)
- D. Multiple opportunistic infections with decreased CD4 counts
- E. Vesicular lesions with dermatomal distribution and dendritic corneal ulcers
Nuclear medicine imaging Explanation: ***Pancytopenia and deep vein thrombosis with intermittent hemoglobinuria***
- The described laboratory method is **flow cytometry**, which is the **gold standard for diagnosing paroxysmal nocturnal hemoglobinuria (PNH)** by detecting the absence of **CD55** and **CD59** on red blood cells due to impaired GPI anchor synthesis.
- PNH classically presents with **pancytopenia**, **hemolytic anemia** (leading to hemoglobinuria), and a high risk of **thrombosis** (e.g., deep vein thrombosis).
*Ventricular septal defect and facial dysmorphism with low T-lymphocyte count*
- This clinical picture suggests **DiGeorge syndrome**, which involves a developmental defect of the **third and fourth pharyngeal pouches**, leading to thymic hypoplasia and **T-cell deficiency**.
- While flow cytometry is used to quantify T-lymphocyte subsets (e.g., CD3, CD4, CD8), the primary method for diagnosing DiGeorge syndrome is **fluorescent in situ hybridization (FISH)** for a **22q11 deletion**, making it less ideal for flow cytometry diagnosis.
*Painless generalized lymphadenopathy with monomorphic cells and interspersed benign histiocytes on histology*
- This description with "**monomorphic cells**" is more consistent with certain **non-Hodgkin lymphomas** (e.g., Burkitt lymphoma) rather than Hodgkin lymphoma, which typically shows a **polymorphic** cellular infiltrate.
- While flow cytometry can be useful in characterizing lymphomas by identifying cell surface markers, the diagnosis is primarily established by **lymph node biopsy and histopathology** with **immunohistochemistry**, making flow cytometry a supplementary rather than primary diagnostic tool.
*Multiple opportunistic infections with decreased CD4 counts*
- This presentation is highly suggestive of **HIV infection leading to AIDS**. The "decreased CD4 counts" are a key diagnostic and prognostic marker.
- While flow cytometry is used to **monitor CD4 cell counts** in HIV patients, the initial diagnosis of HIV is established via **antibody/antigen combination tests** and confirmed by **Western blot** or **PCR for viral load**, not by flow cytometry.
*Vesicular lesions with dermatomal distribution and dendritic corneal ulcers*
- This clinical presentation points to **herpes zoster ophthalmicus** (shingles affecting the eye due to **varicella-zoster virus** reactivation).
- Diagnosis is primarily **clinical** based on the characteristic rash and eye findings, although **PCR** of vesicular fluid can confirm VZV infection. Flow cytometry has no role in this diagnosis.
Nuclear medicine imaging US Medical PG Question 9: A 55-year-old man presents to the physician with tiredness, lethargy, bone pain, and colicky right abdominal pain for 1 month. He has no comorbidities. He does not have any significant past medical history. His height is 176 cm (5 ft 7 in), weight is 88 kg (194 lb), and his BMI is 28.47 kg/m2. The physical examination is normal, except for mild right lumbar region tenderness. Laboratory studies show:
Hemoglobin 13.5 g/dL
Serum TSH 2.2 mU/L
Serum calcium 12.3 mg/dL
Serum phosphorus 1.1 mg/dL
Serum sodium 136 mEq/L
Serum potassium 3.5 mEq/L
Serum creatinine 1.1 mg/dL
Urine calcium Elevated
An ultrasound of the abdomen reveals a single stone in the right ureter without hydroureteronephrosis. Clinically, no evidence of malignancy was observed. An X-ray of the long bones reveals diffuse osteopenia with subperiosteal bone resorption. The serum parathyroid hormone level is tested and it is grossly elevated. What is the most appropriate next step in his management?
- A. Ultrasound of the neck only
- B. CT scan of the neck
- C. 99mTc sestamibi scan with ultrasound of the neck (Correct Answer)
- D. Bone scan (DEXA)
- E. Sestamibi scan only
Nuclear medicine imaging Explanation: ***99mTc sestamibi scan with ultrasound of the neck***
- The patient presents with **hypercalcemia**, **hypophosphatemia**, elevated **PTH**, **nephrolithiasis**, and **osteopenia with subperiosteal bone resorption**. These are classic signs of **primary hyperparathyroidism**.
- A **99mTc sestamibi scan** helps localize abnormally functioning parathyroid tissue (adenoma), while an **ultrasound of the neck** provides anatomical detail, guiding surgical planning for parathyroidectomy.
*Ultrasound of the neck only*
- While an ultrasound can identify some parathyroid adenomas, its sensitivity can be limited, especially for smaller or ectopically located glands.
- It does not assess the functional activity or metabolic uptake, which is crucial for identifying the hyperfunctioning gland.
*CT scan of the neck*
- A CT scan can help identify parathyroid adenomas, particularly in cases where ultrasound is inconclusive, but it involves radiation exposure.
- It is generally considered a second-line imaging modality for parathyroid localization after sestamibi scan and ultrasound, or in cases of ectopic adenomas.
*Bone scan (DEXA)*
- A **DEXA scan** measures **bone mineral density** and would confirm the severity of osteopenia or osteoporosis, which is expected in hyperparathyroidism.
- However, it does not localize the source of the excess PTH, which is the immediate goal for surgical planning.
*Sestamibi scan only*
- A **sestamibi scan** is excellent for localizing hyperfunctioning parathyroid tissue but may lack precise anatomical resolution for surgical planning.
- Combining it with an **ultrasound of the neck** provides both functional and anatomical information, optimizing surgical success.
Nuclear medicine imaging US Medical PG Question 10: A 27-year-old man presents to the emergency department with back pain. The patient states that he has back pain that has been steadily worsening over the past month. He states that his pain is worse in the morning but feels better after he finishes at work for the day. He rates his current pain as a 7/10 and says that he feels short of breath. His temperature is 99.5°F (37.5°C), blood pressure is 130/85 mmHg, pulse is 80/min, respirations are 14/min, and oxygen saturation is 99% on room air. On physical exam, you note a young man who does not appear to be in any distress. Cardiac exam is within normal limits. Pulmonary exam is notable only for a minor decrease in air movement bilaterally at the lung bases. Musculoskeletal exam reveals a decrease in mobility of the back in all four directions. Which of the following is the best initial step in management of this patient?
- A. MRI of the sacroiliac joint (Correct Answer)
- B. CT scan of the chest
- C. Pulmonary function tests
- D. Ultrasound
- E. Radiography of the lumbosacral spine
Nuclear medicine imaging Explanation: ***MRI of the sacroiliac joint***
- The patient's symptoms of **worsening back pain**, morning stiffness that improves with activity, and decreased back mobility are highly suggestive of **ankylosing spondylitis**.
- **MRI** is the most sensitive imaging modality for detecting early inflammatory changes in the **sacroiliac joints** and spine, which are characteristic of ankylosing spondylitis, even before radiographic changes are visible.
*CT scan of the chest*
- While the patient reports feeling **short of breath**, his vital signs and oxygen saturation are normal, and he does not appear in acute distress.
- A CT scan of the chest would be a more appropriate step if there were clearer signs of acute pulmonary pathology, such as significant hypoxemia, fever, or adventitious lung sounds, which are not present here.
*Pulmonary function tests*
- **Shortness of breath** could eventually be a complication of severe ankylosing spondylitis due to restricted chest wall expansion.
- However, PFTs are generally not the *initial* diagnostic step given the primary presentation of back pain and the need to confirm the underlying rheumatologic condition first.
*Ultrasound*
- **Ultrasound** is not a primary imaging modality for evaluating the sacroiliac joints or the spine in the context of suspected ankylosing spondylitis.
- It could be useful for assessing peripheral joint inflammation in other arthropathies, but not for axial involvement.
*Radiography of the lumbosacral spine*
- **X-rays of the lumbosacral spine** might show changes in advanced ankylosing spondylitis (e.g., squaring of vertebrae, syndesmophytes), but they are often normal in the early stages of the disease.
- **MRI** is superior for detecting early inflammatory changes and is often used to diagnose the condition before radiographic damage is evident.
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