**Carotid Artery Stenosis Screening**

**Core Concept**
Carotid artery stenosis screening involves assessing the degree of narrowing of the carotid arteries, which supply blood to the brain. The primary goal is to identify individuals at high risk of stroke due to significant stenosis.

**Why the Correct Answer is Right**
The correct choice for in vivo carotid artery stenosis screening involves using non-invasive imaging modalities to visualize the carotid arteries and quantify stenosis. **Doppler ultrasound** is a widely used and effective method for this purpose, as it allows for real-time assessment of blood flow and velocity through the carotid arteries. This information helps determine the degree of stenosis and identify potential risk factors for stroke.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify an in vivo imaging modality, whereas carotid artery stenosis screening requires an invasive or non-invasive approach to visualize the arteries.

**Option B:** This option is incorrect because while **angiography** can be used to assess carotid artery stenosis, it is typically performed invasively and is not the preferred initial screening method.

**Option C:** This option is incorrect because **computed tomography angiography (CTA)** is an imaging modality that can be used to assess carotid artery stenosis, but it is not the most commonly used in vivo screening method due to radiation exposure and cost considerations.

**Clinical Pearl / High-Yield Fact**
When screening for carotid artery stenosis, it is essential to consider the patient's overall risk factors for stroke, including hypertension, diabetes, and smoking. These factors can increase the likelihood of significant stenosis and should be taken into account when selecting the most appropriate screening modality.

**Correct Answer:** C.