Medical Applications User Guide (pdf) - Freescale Semiconductor

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Medical Imaging 18.1 Introduction The complexities of medical imaging require extraordinary processing and RF power. Modalities, such as magnetic resonance imaging (MRI), computed tomography (CT) scans and ultrasound all push the performance limits for advanced integrated I/O, rigorous data processing, powerful display capabilities and high levels of connectivity. Many of these needs are addressed by Freescale’s family of Power Architecture multicore processors, StarCore DSPs and high-power RF devices. The Power Architecture family is designed for applications that require a rich user interface with complex displays and connectivity options with various standard protocols. StarCore DSPs offer unprecedented high-processing capacity to support data intensive applications, such as medical imaging reconstruction. Freescale’s RF power amplifiers provide the high output power required to achieve the desired frequency of resonance. 94 Medical Applications User Guide
18.2 Ultrasound Ultrasound is a non-invasive medical imaging technique used to visualize muscles, tendons, pathological lesions and many internal organs and other structures. It plays an important role during prenatal care and is commonly used as a diagnostic tool. One of the most common uses of ultrasound is for fetal monitoring. Ultrasound uses sound waves to create images of a fetus inside a uterus. Because it uses sound waves instead of radiation, ultrasound is safer than X-rays. Gradually, ultrasound has become an increasingly important part of prenatal care, providing information that can help the doctor to plan the monitoring of a pregnant woman, thus improving the chances of successful pregnancy. 18.3 How Ultrasound Works Ultrasound is based on bouncing sound waves into the body of the developing fetus. The echoes produced by these waves are converted into a picture called a sonogram, which appears on a monitor. This technique is also often referred to as sonography or sonar. Propagation and reflection rules that govern electric signals are also applied to ultrasound. A transmission line must be terminated in its characteristic impedance to avoid reflections. In the equation below, acoustic impedance Z is a fundamental property of matter and is related to the density ρ and the velocity of sound v : Z = ρv. The fraction of energy R refracted at the normal interface of two different tissue types is: R = (Z 2 -Z 1 ) (Z 2 +Z 1 ) 2 Figure 18-1: Ultrasound General Block Diagram Ultrasound Freescale Technology Optional 18.4 Transducer The transducer is the element that converts electrical signals into ultrasound waves. It consists of a set of transmitter and receiver transducers arranged in a linear array. A unique transducer is explained in Chapter 16.6, Fetal Heart Rate Monitor. Pulse trains are sent by transmitter transducers, and receiver transducers receive bounced waves. The operating frequency for this kind of device is from 5 MHz to 8 MHz. Medical Imaging HV Pulse Transducer DAC TX Beamformer Generator Tx/Rx Switches LNA Signal Conditioning The blocks needed for signal conditioning/ pulse generator blocks are shown in Figure 18-3. 18.5 Multiplexer for Tx/Rx Transducers This block may be implemented using analog gates controlled by the MCU/MPU. This allows the use of transducers as transmitters, and later the ability to switch the multiplexer to use as receivers. Multiplexing reduces the freescale .com/medical 95 VGA CW (Analog) Beamformer AAF Power Management Keypad DAC ADC ADC User Interface Spectral Doppler Processing (D Mode) Display Memory Audio Output Figure 17-2: 18-2: Ultrasound Transducer Diagram Diagram TX RX TX RX TX RX TX RX RX Beamformer RF Demodulation B-Mode Processing Scan Conversion USB Patient Beamforming Control DSP/DSC Color Doppler (PW) Processing (F Mode) Wireless Comm
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Medical Applications User Guide TM
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freescale.com/medical 3 Introductio
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Introduction 1.1 Freescale Offers T
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Monebo Kenetic ECG Algorithms Free
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Home Portable Medical 2.1 Introduct
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3.2 Home Health Hub (HHH) Reference
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3.7 How it Works The external capac
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eliably monitor and manage non-crit
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3.19 Standard Medical USB Communica
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4.2 Heartbeat Detection The heartbe
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Heart Rate Monitor 5.1 Introduction
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Instrumentation amplifier requireme
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6.2 Test Strip A test strip consist
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fully featured products at lower co
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Freescale’s Xtrinsic acceleromete
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7.2 Signal Acquisition This applica
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