**Core Concept**
MRI is the imaging modality of choice for CNS neoplasms due to its excellent soft tissue contrast and ability to detect subtle lesions. This is because MRI provides detailed images of the brain and spine, allowing for the accurate diagnosis and characterization of tumors.

**Why the Correct Answer is Right**
The correct answer is **CT scan**. This is because CT scans are less sensitive than MRI in detecting small CNS lesions, and they often cannot distinguish between different types of tumors. CT scans are more useful for detecting calcifications, hemorrhages, and bony abnormalities, but they are not the best choice for evaluating the soft tissue characteristics of CNS neoplasms.

**Why Each Wrong Option is Incorrect**
* **Option A:** MRI is the gold standard for CNS neoplasm imaging due to its excellent soft tissue contrast and ability to detect subtle lesions.
* **Option B:** PET scans can be useful in CNS neoplasm imaging, particularly in detecting tumor metabolism and guiding radiation therapy, but they are not the primary imaging modality.
* **Option C:** Angiography is not typically used for CNS neoplasm imaging, but it may be used to evaluate tumor vascularity or guide interventional procedures.

**Clinical Pearl / High-Yield Fact**
When evaluating a patient with a suspected CNS neoplasm, it is essential to consider the patient's age, symptoms, and medical history, as well as the imaging characteristics of the lesion. For example, a lesion that is isointense to gray matter on T1-weighted MRI images and hyperintense on T2-weighted images is more likely to be a glioblastoma.

**Correct Answer:** D. CT scan