**Core Concept**
Intravenous (I/V) contrast agents are substances used to enhance the visibility of internal structures or lesions during various imaging modalities. These agents work by altering the magnetic properties in MRI, altering the X-ray attenuation in CT scans, or altering the density of iodine in X-ray images.

**Why the Correct Answer is Right**
Myelography involves the injection of a contrast agent into the spinal canal to visualize the spinal cord and nerve roots using X-ray imaging. Since myelography does not require I/V contrast, it stands out as the correct answer. In contrast, CT scans (Option A) and IVP (Option C) both use I/V contrast to visualize internal structures, while MRI (Option B) can also use I/V contrast agents to improve image quality.

**Why Each Wrong Option is Incorrect**
**Option A:** CT scans use I/V contrast agents, such as iodine-based compounds, to enhance the visibility of internal structures and lesions.
**Option B:** MRI can use I/V contrast agents, such as gadolinium-based compounds, to improve image quality and enhance the visualization of certain tissues or lesions.
**Option C:** IVP (Intravenous Pyelography) uses I/V contrast agents to visualize the urinary tract and its structures, such as the kidneys, ureters, and bladder.

**Clinical Pearl / High-Yield Fact**
When choosing between I/V contrast and other types of contrast agents, it's essential to consider the specific imaging modality and the desired outcome. Understanding the properties and uses of different contrast agents can help you make informed decisions in clinical practice.

✓ Correct Answer: D. Myelography