Final answer:
To improve axial resolution in ultrasonography, a sonographer can use a higher frequency transducer which offers finer detail but less tissue penetration. The period of the ultrasound wave must be smaller than the minimum time resolution for seeing small details, and a balance between resolution and penetration depth must be maintained.
Step-by-step explanation:
The sonographer can improve the axial resolution of an ultrasound by using a higher frequency transducer. Higher frequency sound waves have a shorter wavelength, which allows for finer detail in the image. However, there is a trade-off as higher frequencies do not penetrate as deeply into tissue as lower frequencies. The optimal frequency depends on the depth of the area of interest and the level of detail required. In diagnostic ultrasound, echo times are measured to determine distances to reflecting surfaces within a patient. To see details as small as 0.100 cm or 1 mm, discrimination of small time differences in echo times is necessary.
Concerning the period T of the ultrasound and its relation to time resolution, T must indeed be smaller than the minimum time resolution to resolve fine details. Therefore, the minimum frequency of the ultrasound must be sufficiently high. Standard diagnostic ultrasounds range from approximately 2 to 15 MHz. Increasing the frequency increases the resolution but decreases the penetration depth, which needs to be considered for each specific application.