**Core Concept**
Acute osteomyelitis is a bacterial infection of the bone, often caused by Staphylococcus aureus. Early diagnosis is crucial for effective treatment and prevention of complications. The primary challenge in diagnosing osteomyelitis lies in distinguishing it from soft tissue infections, which present with similar symptoms.

**Why the Correct Answer is Right**
Magnetic Resonance Imaging (MRI) is the most sensitive and specific diagnostic tool for differentiating osteomyelitis from soft tissue infections. MRI can detect changes in bone marrow and soft tissue characteristics, allowing for the identification of bone involvement. This is particularly important in the early stages of osteomyelitis, when radiographic findings may be normal or nonspecific. MRI's high sensitivity to soft tissue changes and its ability to visualize bone marrow edema make it an ideal imaging modality for diagnosing osteomyelitis.

**Why Each Wrong Option is Incorrect**
**Option A:** Clinical examination alone is not sufficient to distinguish osteomyelitis from soft tissue infections, as both conditions may present with similar symptoms such as pain, swelling, and erythema.

**Option B:** X-ray may not be diagnostic in the early stages of osteomyelitis, as changes in bone density may not be apparent until several weeks after infection onset. Moreover, X-ray findings may be nonspecific and similar to those seen in soft tissue infections.

**Option C:** CT scan can provide information on bone architecture and may show changes in bone density, but it is not as sensitive as MRI for detecting bone marrow edema and soft tissue involvement, which are key features of osteomyelitis.

**Clinical Pearl / High-Yield Fact**
Remember, in pediatric patients, early MRI findings in osteomyelitis may include bone marrow edema, soft tissue edema, and cortical disruption, which can be subtle and easily missed on X-ray or CT scan.

**✓ Correct Answer: D. MRI. Magnetic Resonance Imaging is the most sensitive and specific diagnostic tool for differentiating osteomyelitis from soft tissue infections.**