The size of the crystal inside the ultrasound machine primarily affects which aspect of the beam?

The size of the crystal inside the ultrasound machine primarily affects which aspect of the beam?

• A. Size of crystal in machine
• B. Frequency
• C. Speed of sound in tissue
• D. Tissue attenuation

Answer: (A)

The beam’s shape and directivity are governed by the transducer’s aperture—the size of the crystal. A larger crystal acts like a bigger antenna, producing a narrower beam with less divergence as it leaves the probe. That narrower beam improves lateral resolution at depth and concentrates energy more tightly in the path of the beam. The other factors—frequency, speed of sound in tissue, and tissue attenuation—aren’t determined by the crystal’s lateral size. Frequency is set mainly by the crystal’s thickness and material, speed of sound is a property of the tissue, and attenuation depends largely on frequency and tissue characteristics, not the crystal size.

The beam’s shape and directivity are governed by the transducer’s aperture—the size of the crystal. A larger crystal acts like a bigger antenna, producing a narrower beam with less divergence as it leaves the probe. That narrower beam improves lateral resolution at depth and concentrates energy more tightly in the path of the beam. The other factors—frequency, speed of sound in tissue, and tissue attenuation—aren’t determined by the crystal’s lateral size. Frequency is set mainly by the crystal’s thickness and material, speed of sound is a property of the tissue, and attenuation depends largely on frequency and tissue characteristics, not the crystal size.