If two reflectors are 1.3 mm apart and the SPL of the transducer is 2.6 mm, how will they appear on the screen?

When two reflectors are closer together than the spatial resolution determined by the transducer's characteristics, they may be perceived differently on a sonographic image. In this situation, the two reflectors are 1.3 mm apart, and the spatial pulse length (SPL) of the transducer is 2.6 mm.

Spatial resolution is influenced by the SPL; when two structures are at least half the SPL apart, they can typically be resolved as separate entities. The rule of thumb in ultrasound is that if two structures are spaced apart by at least half of the SPL, they will be seen as distinct. Since the reflectors are 1.3 mm apart, which is less than the full SPL of 2.6 mm but more than half (which is 1.3 mm since half of 2.6 mm is 1.3 mm), they can still be differentiated on the ultrasound image.

Therefore, they will appear as two separate dots on the screen, as the spatial separation is sufficient to allow for the differentiability of the two reflectors, despite being very close. The ability to distinguish these reflectors is critical for accurate diagnostics and imaging in ultrasound.