What type of examination is performed using a portable hand-held machine that typically utilizes a standard 3-7 MHz curved array probe?

The correct answer is the FAST examination, which stands for Focused Assessment with Sonography for Trauma. This examination is specifically designed for rapid assessment of trauma patients, particularly assessing for internal bleeding in the abdomen and chest. The use of a portable handheld ultrasound device with a 3-7 MHz curved array probe is ideal for this procedure due to its ability to provide real-time imaging and its portability, allowing for examination in various settings, including emergency situations.

In contrast, CT scans, X-rays, and MRIs involve different types of imaging technology and are typically not performed with handheld devices. A CT scan uses X-ray technology to create detailed images of the body's internal structures and requires larger, stationary machines. X-rays also utilize a different form of radiation exposure for imaging bones and certain tissues, while MRIs rely on magnetic fields and radio waves, requiring bigger machinery and extended patient preparation. Thus, the portable ultrasound system's capability aligns perfectly with the requirements of a FAST examination, making it the appropriate choice.