A customer wants to construct an ultrasonic medical imaging system based on a transducer array. A central ultrasonic generation transducer generates a burst of ultrasonic energy which travels towards a tissue specimen. Echoes reflected off the tissue specimen are simultaneously detected by an array of 48 ultrasonic receiver transducers arranged in a dish-like pattern.
The customer must simultaneously digitize all 48 signals and download them to PC RAM as quickly as possible. The customer requires 8 bit vertical resolution and would like to sample at 40 MS/s, but 20 MS/s would be acceptable. The customer will provide a trigger signal, after which each signal must be digitized for one microsecond.
Finally, the customer wants to write his own applications in C.
The proposed GaGe solution is an integrated turn-key system constructed by GaGe engineers. The system consists of a GaGePC 586 industrial PC modified so that it is housed in a PIA-725 chassis with a 20 slot ISA backplane. The GaGePC 586 is connected to a second PIA-725 industrial grade chassis with a 20-slot ISA backplane through an ISA Bus Expansion Kit.
The acquisition will be done by 24 CompuScope LITE boards, each operating in dual-channel mode. There will be eight CompuScope LITE boards in the industrial PC and 16 in the expansion chassis. The boards will operate independently but will all be connected to the same external trigger, provided by the customer.
The customer will sample at 20 MS/s for 1 ms for a record length of:
Record Length = 1 us x 20 MS/s = 20 (us)(MSamples)/s = 20 Samples -6 6 Calculation help: 1u x 1M = 10 x 10 = 1
In dual-channel mode, the CompuScope LITE allows the length of the post-trigger record to be specified in increments of 64 samples, so that 64 samples must be acquired and the customer can ignore the last 44. The ISA bus transfer rate on the CompuScope LITE is 1 MS/s, so that the transfer time to download the record from each board is:
Transfer Time = 64 Samples / 1 MSample/s = 64 s/1M = 64 ms 6 -6 Calculation help: 1/1M = 1/10 = 10 = 1u
If we make a conservative estimate of the set-up time for PCI transfer of 10 ms, then this gives us a transfer time of 74 ms per channel. The total transfer time for the 48 channels is, therefore, 48 x 74 u s = approximately 3.6 ms.
Since the capture time of 64 / 20 MS/s = 3.2 us is insignificant when compared to the 3.6 ms total transfer time, it can be ignored in calculating the maximum achievable pulse repeat frequency (PRF). The maximum achievable PRF is, therefore, simply:
Maximum PRF = 1/3.6 ms = 278 Hz
This means that the customer can capture and download all 48 x 64 Samples = approximately 3 kSamples of data at rates of up to 278 times per second. This rate far exceeds the ~30 Hz necessary to create the illusion of continuous motion for the human eye. Since processing and displaying the data would slow the process down, it could all be stored in PC DRAM on-line and then processed and analyzed later.
For instance, if the PC had 16 MBytes (=16 MSamples) of available onboard DRAM, then the customer could capture and transfer 16 MSamples/(3 kSamples/burst) = approximately 5300 bursts of data. This would allow the customer to store 5300 x 3.2 ms approximately 17 seconds worth of data before filling up PC memory and having to stop either to dump the data to disk or to process and display the data. Alternatively, the customer could use fast processing and video boards to process and display the data on-line.
In view of the large number of channels, the customer is considering constructing his own dedicated 48-channel acquisition boards which will involve purchasing materials plus dedicating at least three months of his own time to build, test, interface and program the boards. The customer's estimated minimum total real cost of the customer's custom-built boards is less than GaGe's quoted price - but there is no guarantee that the system will work.
For a cost of under 50 % more than the customer's home-made solution, GaGe provides an integrated, turn-key solution that is completely tested by GaGe engineers before shipment, is totally expandable and comes with tried and tested C drivers that can simply be inserted into the customer's main software application.
We encourage you to contact us and discuss your medical application in more detail with our engineering team. GaGe can provide tailored custom data acquisition hardware and software solutions to meet specific application requirements.