**Core Concept**
Radiation exposure is a critical concern in medical imaging, and various techniques can significantly impact the amount of radiation patients receive. The goal is to minimize radiation exposure while maintaining diagnostic image quality.

**Why the Correct Answer is Right**
The correct answer is **Digital Radiography (DR)**, which uses an electronic detector to convert X-ray energy into digital signals. This technology allows for optimal image quality at lower radiation doses compared to older film-screen radiography methods. The lower radiation doses are due to the ability to adjust the X-ray beam to the specific patient and the use of a digital detector that can optimize the image quality without increasing the radiation dose.

**Why Each Wrong Option is Incorrect**
**Option B:** **Computed Tomography (CT)** involves the use of X-rays and computer algorithms to produce detailed cross-sectional images. Unfortunately, CT scans require significantly higher radiation doses compared to DR, making it a less desirable option for minimizing radiation exposure.

**Option C:** **Mammography** is a specialized form of DR used for breast imaging. While mammography is designed to produce high-quality images at relatively low radiation doses, it is not the least radiation-exposure method compared to DR.

**Option D:** **Fluoroscopy** uses X-rays to produce real-time images of internal structures. However, fluoroscopy often requires higher radiation doses than DR, especially during prolonged procedures.

**Clinical Pearl / High-Yield Fact**
When choosing between different radiographic techniques, remember that **digital radiography (DR)** typically offers better image quality at lower radiation doses compared to film-screen radiography and other methods.

**Correct Answer: D. Digital Radiography (DR)**