**Core Concept**
High-resolution computed tomography (HRCT) is the gold standard for diagnosing and characterizing interstitial lung diseases (ILDs). HRCT provides detailed images of the lung parenchyma, allowing for the identification of subtle abnormalities and patterns that are characteristic of specific ILDs.

**Why the Correct Answer is Right**
HRCT is superior to other imaging modalities due to its high spatial resolution and ability to detect subtle changes in lung density. The HRCT protocol typically involves thin-section images (1-2 mm) obtained at multiple levels, allowing for a comprehensive assessment of the lung parenchyma. This enables the detection of characteristic patterns such as ground-glass opacification, reticular markings, and honeycombing, which are hallmarks of various ILDs.

**Why Each Wrong Option is Incorrect**
**Option A:** Chest X-ray (CXR) is not sensitive enough to detect subtle changes in lung density and is often normal in patients with interstitial lung disease.
**Option B:** Chest MRI may be useful in certain cases, but it is not as sensitive as HRCT for detecting interstitial lung disease.
**Option C:** Pulmonary function tests (PFTs) are useful for assessing the functional impact of ILD on lung function but do not provide direct visualization of the lung parenchyma.

**Clinical Pearl / High-Yield Fact**
When interpreting HRCT images, it's essential to remember that the pattern of disease is often more important than the degree of disease. Characteristic patterns such as ground-glass opacification or honeycombing can help narrow down the differential diagnosis and guide further management.

**Correct Answer: C. Pulmonary function tests are useful for assessing the functional impact of ILD on lung function but do not provide direct visualization of the lung parenchyma.**