医学交流课件：OPTIMIZING YOUR

1、ABDOMEN- Physics OPTIMIZING YOUR MACHINE OPTIMIZING YOUR MACHINE Ultrasound is a dynamic process Constant interaction between you and your machine is required TRANSDUCERS IDEAL TYPE OF TRANSDUCER? Mechanical vs electronic Linear, convex, phased array, sector scanner Scan head shape Frequency Depends

2、 on use and available money! Mechanical Sector Transducer Does not allow variable focussing Elements are mechanically rotated Small footprint intercostal scanning Moving parts subject to wear More prone to damage when dropped Electronic Transducers Multiple crystals fire together or sequentially Mul

3、ti-element transducers are called arrays Linear Convex Phased Linear Array Transducer Rectangular FOV Often limited skin contact Wide near-field, limited depth Best for musculoskeletal application, superficial structures Highest lateral resolution High frequencies (up to 25mHz) Convex Array Transduc

4、er = curvilinear 60, 90, 120 Wide near-field Even wider far- field Best for abdominal scans Phased Array Transducer Sector FOV Firing of multiple transducer elements in a precise sequence electronically Wide FOV at deep depths Phased Array Transducer Limited near-field visibility compared with linea

5、r-array or curvilinear-array transducers Useful for evaluation of deeper structures Best for heart (intercostal windows) Transducer Care Do not apply alcohol directly onto surface Clean/wipe after every scan Freeze image when not in use Heat sensitive do not sterilize Settings - Power Intensity (Amp

6、litude) of sound Adjusting power effects entire screen Related to artefact production The lower the power setting, the less likely artefacts will occur Settings - Gain Amplification and reject controls Intensity of sound decreases with depth Amplification of returning echoes Selects gain (vs Overall

7、 Gain) Not equal to power Settings - Gain Overall Gain Uniform amplification of all returning echoes regardless of depth Settings - Gain Time Gain Echoes returning from deeper structures are weaker than those arising from more superficial structures Selective gain Near-field gain Far-field gain Series of sliding controls Settings - Gain Time Gain Settings - Focus Set continuously during scanning, dynamic process Autofocus Single or multiple Changes in frame rate Patient Preparation Starve or not? Access to water Avoid stress