Ultrasound Modes

A Mode presents reflected ultrasound energy on a single line display. The strength of the reflected energy at nay particular depth is visualized as the amplitude of the waveform. B Mode converts A Mode information into a two dimensional grayscale display. C Mode is a color representation of blood flow velocity and direction. D Mode is a spectral representation of blood flow velocity and direction. P Mode is used to visualize very low blood flows in color. Unlike C Mode, this mode does not show the operator flow direction. Triplex is the simultaneous operation of B Mode, C Mode and D Mode. M Mode is a scrolling display allowing the operator to view and record organ motion.

Axial Resolution Another concern is Resolution. Axial resolution is corresponds directly to the wave length characteristics of the Ultrasound wave. As frequency increases wave length shortens allowing for greater resolution. What we loose is penetration. Again as frequency increases penetration decreases. Higher frequencies also provide finer tissue grain or smoothness. A less grainy look.

Lateral resolution In simple ultrasound systems Lateral resolution is attributed to physical focus characteristics of the crystal element. The concaved shape of the element provides focus to the beam and the width of the beam at any particular point effects the ability of the ultrasound system to resolve small objects that are side by side.

Transverse resolution Transverse resolution is unique to the phase array probe. It is the ability of the probe to resolve objects side by side, as in lateral resolution, but in this case it is measured transverse to what would be considered the normal imaging plane. Again this is assuming simplest probe construction.

Contrast Resolution The ability of the system to resolve adjacent bright reflectors is called contrast resolution. This is in small part due to the cumulative effects of axial and lateral resolution. The systems scan converter plays a large role is this characteristic.

Diagnostic Ultrasonography Displaying Monitor Transducer / Probe Keyboard Probe Connector Printer (B/W & Color)

Device that can change one form of energy into another. The necessary element for generating acoustic waves. Electrical excitation into motion and pressure.

(A) (B) (C) -

Transducer Design

Echoes from Two Interfaces

Echoes from Internal Organ

A- mode B- mode M- mode Doppler Pulsed Continuos

Amp H. V CRT Transducer Organ Body T/R switch Trigger Pulser Time variable gain Saw tooth voltage sweep Block diagram of an A-scan instrument. A pulser circuit triggers the transducer, and the saw-tooth generator. The T/R switch isolates the receiver amplifier during transmission. Amplitudes of the received echo signals are presented on the vertical axis of the CRT.

Brightness modulation Horiz. Vert. CRT Amp T/R switch Pulser circuit Time variable gain Saw tooth voltage sweep Beam steering control unit A pulser circuit triggers the transducer, and the saw tooth generator. The T/R switch isolates the receiver amplifier during transmission. For each scanning line, the amplitudes of the received echo signals are modulated to brightness. Steering unit is controlling the synchronization process.

Transducer Fixed organ Horiz. Vert. CRT Amp Moving Organ Body T/R switch Trigge r Pulser circuit Time variable gain Sawtooth voltage sweep Slow voltage ramp A B B

TRANSMITTERRECEIVER PULSED CONTINUES

Linear Probe Image

Sector (Phased array) Probe

Convex Probe Image

Real Time 3D

Fetal Spine

Reconstructional 3-D Obstetrics

Ultrasound Machines

Function Diagnostic ultrasound machines are used to give images of structures within the body. This chapter does not deal with other kinds of machine (e.g. therapeutic and lithotripsy). The diagnostic machine probes, which produce the ultrasound, come in a variety of sizes and styles, each type being produced for a particular special use. Some require a large trolley for all the parts of the unit, while the smallest come in a small box with only a audio loudspeaker as output. They may be found in cardiology, maternity, outpatients and radiology departments and will often have a printer attached for recording images. Unlike X-rays, ultrasound poses no danger to the human body. How it works The ultrasound probe contains a crystal that sends out bursts of high frequency vibrations that pass through gel and on through the body. Soft tissue and bone reflect echoes back to the probe, while pockets of liquid pass the ultrasound straight through. The echoes are picked up and arranged into an image displayed on a screen. The machine offers a number of processing options for the signal and image and also allows the user to measure physical features displayed on the screen. This requires the machine to incorporate a computer.

WHAT TYPES OF EXAMINATION ARE TO BE CARRIED OUT ?

1. TRANSDUCER * Curvilinear or combination of linear and sector. 2. FREQUENCY * Standard transducer should have central frequency of 3.5 MHz. 3. ANGLE for Sector probe should be 40 or more, linear array should be cm long. 4. FRAM RATE… Hz for linear array, Hz for sector array. 5. FRAM FREEZE DENSITY… at least 512*512*4 bits to provide 16 gray levels

6. ELECTRONIC CALIPERS… one pair at least, with Quantitative readout. 7. ADD DATA IS POSSIBLE… patient identification, hospital name, date of examination… etc. 8. HARD COPY… should be possible. 9. MONITOR… at least 13 cm * 10 cm (preferably larger) 10. STABILIZING… should be able to stabilize voltage variation of +/- 10%. 11. Biometric tables… (it may not be universal and should be adjusted for local standards.

WHAT WE HAVE TO CHECK WHEN WE RECEIVE THE SCANER USER’S MANUAL SERVICE MANUAL

1. Voltage setting should be compatible with the electrical supply. 2. Interference on the screen/ whit sparks. 3. Transducer and cables test. 4. Check the cursor / measuring length, … 5. Check the accessibility of the biometrics or measurement tables.

Any missing or distorted image that does not match the real image of the part being examined

Acoustic characteristics of the tissues. Scanner’s settings. Lack of user’s experience. Defected part within the scanner.

COMMON ARTIFACTS: Cyst’s artifact (strong back-wall effect). Abdominal wall artifact. Gas artifact. Reverberation artifact. Incomplete imaging artifact. Gain artifact. Shadows artifact.

Visually inspects all transducers. “Cable, cracked surface, punctured, discolored casing” Visually inspect the power cords. Verify that the trackball and DGC controls appears clean and free from gel or other contaminants. Once the system is powered on: Verify that the monitor displays CORRECTLY the connected transducer’s identification, current date, time.

FOCUS. DEPTH GAIN COMPENSATION. OVERALL GAIN. ZOOM. MONITOR (B/C).

MAIN UNIT Surface of the system. DGC slides control. Trackball. Unit filters. TRANSDUCERS Linear, convex, ….. Endocavity, interoperative, …