5 ms·

Power isn't a problem, because at that frequency any kind of amplifier can be used. Overall IO speed usually is for the simple fact that very few chips are spe

by hwillis 10y ago

Power isn't a problem, because at that frequency any kind of amplifier can be used. Overall IO speed usually is for the simple fact that very few chips are specifically designed for that kind of thing, but it isn't impossible. AM335, FPGA and many DSP chips will handle that level of processing for <$20. The Raspberry Pi can't be used, but you could use a Beaglebone black if you tried hard enough (although it is also a poor choice). Regardless direct sampling ADC at 80 MHz or less is far from an impossible task. In the end I would say the writer is right and you are wrong. He is painting with an extremely broad brush but his guesses are dead on the money. You should look at the links he provides at the bottom, there are exceptionally good DIY and open source ultrasonic machines. Making the transducer is very, very difficult but he doesn't pretend it isn't.

jjoonathan 10y ago
> direct sampling ADC at 80 MHz or less is far from an impossible task The Sonix linked below has 32 40MHz 10bit ADC channels, which is a factor of 64 off from the 80 MHz figure if one were to assume 8 bit, and places us firmly into the realm of several-hundred-dollar ADCs. Not impossible, but I'm pretty sure that's where much of the cost is hidden.
- raverbashing 10y ago
  You probably don't need 10bit, but yeah, 32 channels is needed. I wonder how did older machines did that, if it was done using analog processing I wonder if there's an equivalence to 'synthetic aperture radar' on Ultrasound. then maybe you don't need 32 channels
  - temac 10y ago
    Very old machine did some analog processing. Then it switched to digital on dedicated hardware. New machines can do all the processing in software, running on conventional hardware. There is all kind of fun stuff that you can do with ultrasound, and some are similar to 'synthetic aperture radar'. However, 32 channel is still quite low. Lots of probes for humans are commonly using ~100 channels.
    - spott 10y ago
      Do they actually sample the baseband digitally? I would expect that they are looking at the return as an amplitude modulated and phase-shifted signal at the carrier frequency. They remove the carrier frequency and then look at the (much slower) modulation frequency. I'm not sure what you gain from looking directly at the carrier frequency...
      - temac 10y ago
        You don't necessarily need the baseband (I'm not even sure if you ever need it) & depending on the mode you can tune the amount of bandwidth needed.
      - sharpneli 10y ago
        The relative bandwidth in ultasound is immense conpared to radar etc where a relatively narrow bandwidth is used. As an example one of our probes in university days was something like from 5 to 30MHz. Doesn't save much if we would mix it down that 5. Instead of 60MHz ADC we would need 50MHz. Not worth it.
- temac 10y ago
  That kind of figures is better than nothing but is exactly what I had in mind between toy systems and what good quality ones are able to provide. 80MHz is actually not mandatory but 40MHz starts to be really on the low end side, I think, but for low frequency probes that should still be quite good. Of course if you stick to simple B-mode you can get something visible with pretty much anything. 32 channels seems to start to be quite low, though, but yeah, better than nothing. If you start to drive your TX path with "small" (depending on the number of channels) FPGA or CPLD, yeah this is more possible than with a raspberry pi GPIOs, this is even how some good ultrasound machines are build (depending on the volume) In the end the cost of the hardware will be not far from the production cost of a "conventional" ultrasound machine. Because that industry has "low" volumes and very high R&D costs (especially for machines intended for diagnostic use), the difference between production cost and market price is very high. If you can eliminate part of that difference because you operate in another context, that's one way to drive the price down. So yes, it should be possible to build one with limited capabilities for a few k$ per unit. (Spending various amount of money on R&D, depending what you're doing precisely.)
  - stymaar 10y ago
    > Because that industry has "low" volumes and very high R&D costs (especially for machines intended for diagnostic use), the difference between production cost and market price is very high. This is true, but this is only half of the story : the market price is also high because the elasticity of the demand for medical devices is really low. The hospitals charge a lot of money to their customers and their willingness to pay is also high. I've developed software for customers working in the legal industry and it's the same kind of market: these people pay a lot for really simple stuff because they have money and want to get things done.
    - temac 10y ago
      Hm, on the buyer side, it depends on the country but in some it is actually very competitive. So smaller players have a hard time to survive simply because of their lower volumes but similar R&D costs... Plus an ultrasound exam is not too expensive in some (most?) countries.
- TD-Linux 10y ago
  Do you actually need to do baseband sampling? It might be cheaper to bandpass and downconvert the received signal with an analog network first.
  - pjc50 10y ago
    You need the phase information. Actually, that might be a better way of simplifying the information to be sampled - a set of phase comparators.
    - jhallenworld 10y ago
      Phase information is preserved when down converting. But resolution certainly will depend on bandwidth. I read that ultrasound propagation delay is ~650 ns / mm... this is something like 500 KHz for 1 mm (using rise-time * bandwidth = .35 approximation).
- throwawaycanada 10y ago
  You don't need to sample at the carrier frequency for doppler measurement though. Time of Flight... I don't think so either.
- hwillis 10y ago
  It's definitely one of the most expensive parts, but its still a factor of 100 cost difference in parts to product. Even assuming there are 10 parts that all cost a few hundred dollars each (processor, memory, transducer, ADC, amplifier), thats still a 90% profit margin before r&d and other overhead. It's very high.

by hwillis 10y ago

jjoonathan 10y ago

> direct sampling ADC at 80 MHz or less is far from an impossible task The Sonix linked below has 32 40MHz 10bit ADC channels, which is a factor of 64 off from the 80 MHz figure if one were to assume 8 bit, and places us firmly into the realm of several-hundred-dollar ADCs. Not impossible, but I'm pretty sure that's where much of the cost is hidden.

raverbashing 10y ago
You probably don't need 10bit, but yeah, 32 channels is needed. I wonder how did older machines did that, if it was done using analog processing I wonder if there's an equivalence to 'synthetic aperture radar' on Ultrasound. then maybe you don't need 32 channels
- temac 10y ago
  Very old machine did some analog processing. Then it switched to digital on dedicated hardware. New machines can do all the processing in software, running on conventional hardware. There is all kind of fun stuff that you can do with ultrasound, and some are similar to 'synthetic aperture radar'. However, 32 channel is still quite low. Lots of probes for humans are commonly using ~100 channels.
  - spott 10y ago
    Do they actually sample the baseband digitally? I would expect that they are looking at the return as an amplitude modulated and phase-shifted signal at the carrier frequency. They remove the carrier frequency and then look at the (much slower) modulation frequency. I'm not sure what you gain from looking directly at the carrier frequency...
    - temac 10y ago
      You don't necessarily need the baseband (I'm not even sure if you ever need it) & depending on the mode you can tune the amount of bandwidth needed.
    - sharpneli 10y ago
      The relative bandwidth in ultasound is immense conpared to radar etc where a relatively narrow bandwidth is used. As an example one of our probes in university days was something like from 5 to 30MHz. Doesn't save much if we would mix it down that 5. Instead of 60MHz ADC we would need 50MHz. Not worth it.
temac 10y ago
That kind of figures is better than nothing but is exactly what I had in mind between toy systems and what good quality ones are able to provide. 80MHz is actually not mandatory but 40MHz starts to be really on the low end side, I think, but for low frequency probes that should still be quite good. Of course if you stick to simple B-mode you can get something visible with pretty much anything. 32 channels seems to start to be quite low, though, but yeah, better than nothing. If you start to drive your TX path with "small" (depending on the number of channels) FPGA or CPLD, yeah this is more possible than with a raspberry pi GPIOs, this is even how some good ultrasound machines are build (depending on the volume) In the end the cost of the hardware will be not far from the production cost of a "conventional" ultrasound machine. Because that industry has "low" volumes and very high R&D costs (especially for machines intended for diagnostic use), the difference between production cost and market price is very high. If you can eliminate part of that difference because you operate in another context, that's one way to drive the price down. So yes, it should be possible to build one with limited capabilities for a few k$ per unit. (Spending various amount of money on R&D, depending what you're doing precisely.)
- stymaar 10y ago
  > Because that industry has "low" volumes and very high R&D costs (especially for machines intended for diagnostic use), the difference between production cost and market price is very high. This is true, but this is only half of the story : the market price is also high because the elasticity of the demand for medical devices is really low. The hospitals charge a lot of money to their customers and their willingness to pay is also high. I've developed software for customers working in the legal industry and it's the same kind of market: these people pay a lot for really simple stuff because they have money and want to get things done.
  - temac 10y ago
    Hm, on the buyer side, it depends on the country but in some it is actually very competitive. So smaller players have a hard time to survive simply because of their lower volumes but similar R&D costs... Plus an ultrasound exam is not too expensive in some (most?) countries.
TD-Linux 10y ago
Do you actually need to do baseband sampling? It might be cheaper to bandpass and downconvert the received signal with an analog network first.
- pjc50 10y ago
  You need the phase information. Actually, that might be a better way of simplifying the information to be sampled - a set of phase comparators.
  - jhallenworld 10y ago
    Phase information is preserved when down converting. But resolution certainly will depend on bandwidth. I read that ultrasound propagation delay is ~650 ns / mm... this is something like 500 KHz for 1 mm (using rise-time * bandwidth = .35 approximation).
throwawaycanada 10y ago
You don't need to sample at the carrier frequency for doppler measurement though. Time of Flight... I don't think so either.
hwillis 10y ago
It's definitely one of the most expensive parts, but its still a factor of 100 cost difference in parts to product. Even assuming there are 10 parts that all cost a few hundred dollars each (processor, memory, transducer, ADC, amplifier), thats still a 90% profit margin before r&d and other overhead. It's very high.