Use of high-speed signal chain to improve quality of medical imaging

And all are very dependent on the progress of science and technology industry, medical imaging equipment manufacturers have to continuously improve their products, primarily the improved system of imaging quality.

Both ultrasonic reflection acoustic, magnetic resonance imaging (MRI) magnetic disturbance or Positron Emission Tomography (PET), positron emission, most medical imaging technology needs with signal receiving sensor array. Improve the image quality of the most direct way is to expand the size of the sensor array. But due to equipment add more sensors, signal transmission to the processing engine of signal chain must increase electronic devices.

At the same time, manufacturers must also improve its system standards, including the specific electronic component size, power consumption and performance.

System one aspect of the performance enhancements may present challenges to the other side. Simply increasing sensor and signal chain, can cause including system size and power consumption increases, adverse effects. However, used in medical imaging system of the newest generation of signal chain component enables medical system designers can improve signal chain density and power consumption without compromising dynamic performance — that is, the system also for higher image quality, lower power consumption and smaller dimensions.

Medical imaging sink chain of components

For most typical medical imaging applications, sensor array of each component requires its own signal chain and thus the sensor transmits small signal response and conversion into a fit (one fit) for digital signal processing.

Because imaging application sensor signal response properties, so the signal conversion process usually cannot be separated from the three main active components. First, low noise amplifier (LNA), whose main feature is the analog system of noise figure (NF), to the extent possible, fixed at a low level. After the LNA is signal gain another zoom level to achieve the last stage (the analog-digital converter (ADC)) input range of the best match.

Applications such as MRI (usually in signal amplitude, swing not large) can use fixed gain level.

However, if the system signal strength (ultrasonic) there is a big difference, then the system you need a variable gain amplifier (VGA), and you need to use the ADC programmable gain amplifier before (PGA). Through the ADC, the analog signals will be converted to digital signals and is ready to send to the system of digital signal processor (DSP), the procedure normally through field programmable gate array (FPGA) entered the last stage of signal processing and conversion. For MRI, the LNA and the amplifier may also have a range of mixing level to be magnets for radio frequency (RF) energy converted into low-frequency energy. Because each component requires three or more devices, sensors each doubled only accepts analog component signal chain number may need to add to the original six to 10 x! plus, power requirements increase. It is no wonder that system designers always require component supplier on its new integrated circuit (IC) design for innovation to solve the problems related to the dimension.

High integration: more, smaller size

One major improvement is the growing number of active devices integrated in a single chip, thereby reducing the system IC number required.

On a typical ultrasonic accept chain, each sensor may need four components, including three for the amplifier. With modern design and technology, IC vendors now provide the LNA, VCA and PGA integration in a variable gain amplifiers devices will eventually be reduced by one third chip. In addition, the current design is usually each chip contains multiple signal chain channel, such as TI launched VCA8617 devices on each chip has up to eight VGA channels. Through the device's integrated, system designers can optimize its design, resulting in power and performance to make trade-offs between. VCA8613 for a similar device, as opposed to 105 mW, the device power consumption of only 75 mW, but a high noise (1.2 nV/Hz and 1.0 nV/Hz phase contrast).

Lower power consumption and higher performance

And amplifiers, the rest of the ADC also had a similar integration.

Many modern design has 8 channel VGA compatible 8 ADC channel. At the same time, although substantial ADC lowers power consumption, but does not affect them in a typical medical imaging applications run envelope performance. Due to the medical imaging application of noise and linearity of the zoom level is generally such as GE-SI, built-in process. These techniques allow the typical response frequency (from DC to 20 MHz) to achieve the best balance of low noise, low power consumption and high linearity. On the contrary, high-speed ADC typically use CMOS technology to build, because the technology for 10-14-bit precision converters in power consumption and performance have done a very good trade-offs.

Thanks to CMOS technology progressive, ADC's power consumption characteristics and dimensions have been reduced, but its performance is greatly improved.

Compared with the previous ADC, ADC channel ADS5271 has increased four times, signal to noise ratio (SNR) improves 5.5dB. By further raising the channel density, a new generation of ADC will each channel power and board space and reduced by 66%. In addition, input frequency (IF) ADC performance improvement has implemented new MRI System schema. MRI machine magnet of narrowband IF range is 30 to 140 MHz. Traditional architecture will close IF mixed down in DC, you can use a high-precision ADC samples the input frequency. Now, a new generation of 14 and 16-bit ADC in this context to make easy recovery IFSample. With digital extraction technology, the ADC can be realized with the use of traditional architecture implemented similar-to-noise ratio (SNR), thereby improving the the imaging performance while saving board space.

As imaging in medical applications wider use, device manufacturers will continue to design launches imaging quality better type system.

In order to help device manufacturers seeking excellence in imaging effects, a leading semiconductor company will continue the research, development and launch of the technology required to meet the high quality imaging products, the dimension of these products will be more compact, low power consumption.

Reference information

If you would like to learn more about high speed, high accuracy data converters for more details, please visit: www.ti.com/dataconverter.