**Core Concept**
A spot map is a graphical representation used to illustrate the distribution of a particular variable, such as blood flow, oxygen delivery, or drug concentration, within a specific region or organ of the body. This type of map helps clinicians visualize and understand the spatial patterns of the variable being mapped, which is particularly useful in medical imaging and research.

**Why the Correct Answer is Right**
Spot maps are commonly used in medical imaging techniques like positron emission tomography (PET) and single-photon emission computed tomography (SPECT), where they help visualize the distribution of radiotracers within the body. These tracers are designed to accumulate in specific tissues or organs, allowing clinicians to create detailed maps of their distribution. By analyzing these maps, clinicians can diagnose and monitor diseases, as well as assess the effectiveness of treatments.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because spot maps are not typically used for anatomical mapping, which would involve creating detailed images of the body's structure rather than visualizing the distribution of a specific variable.
**Option B:** This option is incorrect because spot maps are not used for creating three-dimensional models of the body, which would involve reconstructing the body's structure from multiple two-dimensional images.

**Clinical Pearl / High-Yield Fact**
Spot maps are particularly useful in oncology, where they can help clinicians visualize the distribution of cancer cells and assess the effectiveness of treatments. By analyzing spot maps, clinicians can identify areas of high or low tumor activity, which can inform treatment decisions and improve patient outcomes.

**Correct Answer: D.**