ULTRASOUND TRANSDUCER CHARACTERISTICS FOR IMAGING
1. ACOUSTIC WINDOW
- Standard acoustic window provides an unobstructed view of organ or region.
- Typical windows are located in or on the head, chest, abdomen, pelvis, vessels and various orifices of the body.
- Transducer can associated with certain regions through latin prefixes like:
Trans :- through or across
Intra : - Into or inside
Endo :- within.
- For example Transthoracic means Image through chest.
- For each type of acoustic window; a particular type transducer is used to get the required sonographic data.
- Eg:- phased arrays are used for transthoracic window and convex arrays are used for abdominal window.
|An acoustic window showing artery and vain|
- Penetration is the minimum scan depth at which electronic noise is visible; despite optimization of available control.
- It can be primarily determined by the center of the frequency of the transducer.
- That is the transducer having high frequency will have low penetration.
|Relationship between frequency and penetration|
3. SPACIAL RESOLUTION
- It is the ability to discern the smallest possible dimension in both axial and lateral directions.
- Axial resolution refers to the ability to distinguish two structures that lie along the axis (i.e. parallel) of the ultrasound beam as separate and distinct.
- Axial resolution is determined by the pulse length.
- Lateral resolution refers to resolution of objects lying side by side (i.e., perpendicular to the beam axis).
- Lateral resolution is directly related to the transducer beam width, which in turn is inversely related to the ultrasound frequency.
4. TRANSDUCER PARAMETERS
- It includes:
- Signal to Noise Ratio,
- Absorbtion of the tissues
- Band width
- Number of elements in transducer etc.