Dr Mohamed el Safwany, MD.

 The student should learn at the end of this lecture medical ultrasound imging.

The Ultrasound Machine A basic ultrasound machine has the following parts: 1.Transducer probe - probe that sends and receives the sound waves 2.Central processing unit (CPU) - computer that does all of the calculations and contains the electrical power supplies for itself and the transducer probe 3.Transducer pulse controls - changes the amplitude, frequency and duration of the pulses emitted from the transducer probe 4.Display - displays the image from the ultrasound data processed by the CPU 5.Keyboard/cursor - inputs data and takes measurements from the display 6.Disk storage device (hard, floppy, CD) - stores the acquired images 7.Printer - prints the image from the displayed data

The basic functional components of an ultrasound imaging system are shown below. THE ULTRASOUND IMAGING SYSTEM

Modern ultrasound systems use digital computer electronics to control most of the functions in the imaging process. 1.Transducer 2.Pulse Generator 3.Amplification 4.Scan Generator 5.Scan Converter 6.Image Processor 7.Display We will now consider some of these functions in more detail and how they contribute to image formation.

Transducer 1 The transducer is the component of the ultrasound system that is placed in direct contact with the patient's body. It alternates between two major functions: (1) producing ultrasound pulses and (2) receiving or detecting the returning echoes. Within the transducer there are one or more piezoelectric elements. When an electrical pulse is applied to the piezoelectric element it vibrates and produces the ultrasound. Also, when the piezoelectric element is vibrated by the returning echo pulse it produces a pulse of electricity. The transducer also focuses the beam of pulses to give it a specific size and shape at various depths within the body and also scans the beam over the anatomical area that is being imaged.

Pulse Generator 2 The pulse generator produces the electrical pulses that are applied to the transducer. For conventional ultrasound imaging the pulses are produced at a rate of approximately 1,000 pulses per second. This is the pulse rate (pulses per second) and not the frequency which is the number of cycles or vibrations per second within each pulse. The principal control associated with the pulse generator is the size of the electrical pulses that can be used to change the intensity and energy of the ultrasound beam.

Amplification 3 Amplification is used to increase the size of the electrical pulses coming from the transducer after an echo is received. The amount of amplification is determined by the gain setting. The principal control associated with the amplifier is the time gain compensation (TGC), which allows the user to adjust the gain in relationship to the depth of echo sites within the body.

Scan Generator 4 The scan generator controls the scanning of the ultrasound beam over the body section being imaged. This is usually done by controlling the sequence in which the electrical pulses are applied to the piezoelectric elements within the transducer.

Scan Converter 5 Scan conversion is the function that converts from the format of the scanning ultrasound beam into a digital image matrix format for processing and display. Image Processor 6 The digital image is processed to produce the desired characteristics for display. This includes giving it specific contrast characteristics and reformatting the image if necessary.

Display 7 The digital ultrasound images are viewed on the equipment display (monitor) and usually transferred to the physician display or work station. One component of the ultrasound imaging system is the digital storage device that is used to store images for later viewing if that process is used. Keyboard/Cursor 8 Ultrasound machines have a keyboard and a cursor, such as a trackball, built in. These devices allow the operator to add notes to and take measurements from the data.

Disk Storage 9 The processed data and/ or images can be stored on disk. The disks can be hard,floppy disk, compact discs (CDs) or digital video discs (DVDs). Typically, a patient's ultrasound scans are stored on a floppy disk and archived with the patient's medical records. Printers 10 Many ultrasound machines have thermal printers that can be used to capture a hard copy of the image from the display.

 David Sutton’s Radiology  Clark’s Radiographic positioning and techniques

 Two students will be selected for assignment.

 Define role of amplification in ultrasound?

Thank You 16