**Core Concept**
Ultrasonography is a diagnostic imaging modality that uses high-frequency sound waves to produce images of internal structures. It is commonly used in obstetrics and gynecology, cardiology, and abdominal imaging. However, there are certain situations where ultrasonography may not be useful or may provide limited information.

**Why the Correct Answer is Right**
The correct answer is likely related to the limitations of ultrasonography in visualizing certain types of tissues or structures. Ultrasonography is not useful in imaging calcified structures, such as bone or certain types of kidney stones, due to the high density of these tissues. Additionally, air-filled structures, such as the lungs, can also make it difficult to obtain clear images using ultrasonography. This is because sound waves are unable to penetrate air-filled spaces.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because ultrasonography is actually useful in visualizing soft tissue structures, such as tendons, muscles, and organs.
* **Option B:** This option is incorrect because ultrasonography can be used to guide needle placement and injection in procedures such as biopsies and injections.
* **Option C:** This option is incorrect because ultrasonography is not limited by the use of contrast agents, which can be used to enhance image quality.

**Clinical Pearl / High-Yield Fact**
A key limitation of ultrasonography is its inability to penetrate air-filled structures or calcified tissues, making it less useful in these situations. This is an important consideration when selecting a diagnostic imaging modality for patients with suspected injuries or conditions involving these types of tissues.

**Correct Answer: D. Air-filled structures or calcified tissues.**