Hi, all,
Hoping there are still some DSP folks round here despite the evil Google
ban. (But I repeat myself.)
I'm working on a completely noninvasive sensor for fetal blood oxygen,
using optical sensing through the mom's abdomen. It's a very low SNR >measurement on account of all the attenuation.
The mom's heartbeat modulates her pulse-ox signal, which is much
stronger than the fetus's on account of the scattering and absorption in >maternal tissue.
The data are several time series. The main issue is the variability of
both pulses, which smear out the spectra and therefore knock the peak
heights way down towards the noise. There are weak multiplicative
effects between maternal and fetal signals, as you'd expect.
What I'm looking to do is something like:
1. Use a digital PLL to find the time-dependent maternal pulse rate.
2. Resample the data accordingly, and notch out the first 5 or so mom >harmonics.
3. Do the PLL thing on the fetal pulse, and signal average to pull out
the average fetal pulse ox signal.
Extra credit: sometimes the baby's pulse can cross the first or second >harmonic of the mom's, and it would be good to preserve both pulse
shapes accurately.
Resampling a noisy signal isn't necessarily the most well-conditioned >operation, so I'd welcome suggestions for just how to do this.
Thanks
Phil Hobbs
On Tue, 18 May 2021 18:31:28 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
Hi, all,
Hoping there are still some DSP folks round here despite the evil Google
ban. (But I repeat myself.)
I'm working on a completely noninvasive sensor for fetal blood oxygen,
using optical sensing through the mom's abdomen. It's a very low SNR
measurement on account of all the attenuation.
The mom's heartbeat modulates her pulse-ox signal, which is much
stronger than the fetus's on account of the scattering and absorption in
maternal tissue.
The data are several time series. The main issue is the variability of
both pulses, which smear out the spectra and therefore knock the peak
heights way down towards the noise. There are weak multiplicative
effects between maternal and fetal signals, as you'd expect.
What I'm looking to do is something like:
1. Use a digital PLL to find the time-dependent maternal pulse rate.
2. Resample the data accordingly, and notch out the first 5 or so mom
harmonics.
3. Do the PLL thing on the fetal pulse, and signal average to pull out
the average fetal pulse ox signal.
Extra credit: sometimes the baby's pulse can cross the first or second
harmonic of the mom's, and it would be good to preserve both pulse
shapes accurately.
Resampling a noisy signal isn't necessarily the most well-conditioned
operation, so I'd welcome suggestions for just how to do this.
Thanks
Phil Hobbs
Would an Adaptive Noise Cancelling or Adaptive Noise Reduction
technique work? I'd guess that the mom's heartbeat could be isolated reasonably well as the "noise" source with potentially a separate
sensor placed to minimize the fetal heartbeat, and use that as the
noise to be cancelled by the ANC/ANR?
Just a thought. Since the mom's heartbeat has higher SNR it seems
like it could be subtracted, and an ANR/ANC would be a pretty well-established way to do that. If the mom's heartbeat needs more
SNR, or the fetal heartbeat rejected more for the noise reference
signal, a separate sensor or sensors might help with that.
Sounds like an interesting problem, regardless.
I'm working on a completely noninvasive sensor for fetal blood oxygen,
using optical sensing through the mom's abdomen. It's a very low SNR measurement on account of all the attenuation.
The mom's heartbeat modulates her pulse-ox signal, which is much
stronger than the fetus's on account of the scattering and absorption in maternal tissue.
The data are several time series. The main issue is the variability of
both pulses, which smear out the spectra and therefore knock the peak
heights way down towards the noise. There are weak multiplicative
effects between maternal and fetal signals, as you'd expect.
Am 19.05.21 um 00:31 schrieb Phil Hobbs:
I'm working on a completely noninvasive sensor for fetal blood oxygen,
using optical sensing through the mom's abdomen. It's a very low SNR
measurement on account of all the attenuation.
The mom's heartbeat modulates her pulse-ox signal, which is much
stronger than the fetus's on account of the scattering and absorption
in maternal tissue.
The data are several time series. The main issue is the variability
of both pulses, which smear out the spectra and therefore knock the
peak heights way down towards the noise. There are weak
multiplicative effects between maternal and fetal signals, as you'd
expect.
How about using a second channel to detect the mother's heartbeat? For example an ECG channel? It's not perfectly synchronized, though, the
delay between ECG and pulse oxymetry is influenced by the blood
pressure. So it only works if the blood pressure is constant.
    Christian
Hi, all,
Hoping there are still some DSP folks round here despite the evil Google
ban. (But I repeat myself.)
I'm working on a completely noninvasive sensor for fetal blood oxygen,
using optical sensing through the mom's abdomen. It's a very low SNR measurement on account of all the attenuation.
The mom's heartbeat modulates her pulse-ox signal, which is much
stronger than the fetus's on account of the scattering and absorption in maternal tissue.
The data are several time series. The main issue is the variability of
both pulses, which smear out the spectra and therefore knock the peak
heights way down towards the noise. There are weak multiplicative
effects between maternal and fetal signals, as you'd expect.
What I'm looking to do is something like:
1. Use a digital PLL to find the time-dependent maternal pulse rate.
2. Resample the data accordingly, and notch out the first 5 or so mom harmonics.
3. Do the PLL thing on the fetal pulse, and signal average to pull out
the average fetal pulse ox signal.
Extra credit: sometimes the baby's pulse can cross the first or second harmonic of the mom's, and it would be good to preserve both pulse
shapes accurately.
Resampling a noisy signal isn't necessarily the most well-conditioned operation, so I'd welcome suggestions for just how to do this.
Thanks
Phil Hobbs
There are weak multiplicative
effects between maternal and fetal signals, as you'd expect.
Phil Hobbs wrote:
Hi, all,
Hoping there are still some DSP folks round here despite the evil
Google ban. (But I repeat myself.)
I'm working on a completely noninvasive sensor for fetal blood oxygen,
using optical sensing through the mom's abdomen. It's a very low SNR
measurement on account of all the attenuation.
The mom's heartbeat modulates her pulse-ox signal, which is much
stronger than the fetus's on account of the scattering and absorption
in maternal tissue.
The data are several time series. The main issue is the variability
of both pulses, which smear out the spectra and therefore knock the
peak heights way down towards the noise. There are weak
multiplicative effects between maternal and fetal signals, as you'd
expect.
What I'm looking to do is something like:
1. Use a digital PLL to find the time-dependent maternal pulse rate.
2. Resample the data accordingly, and notch out the first 5 or so mom
harmonics.
3. Do the PLL thing on the fetal pulse, and signal average to pull out
the average fetal pulse ox signal.
Extra credit: sometimes the baby's pulse can cross the first or second
harmonic of the mom's, and it would be good to preserve both pulse
shapes accurately.
Resampling a noisy signal isn't necessarily the most well-conditioned
operation, so I'd welcome suggestions for just how to do this.
Thanks
Phil Hobbs
I'd be tempted to take a cuff-style/smartwatch heartrate reading from Ma
and use that as the top of a search tree for the other frequencies. "Top
of a search tree" isn't really all that much help but it's a start.
The thing I'd wonder is whether the fetal ox cycle isn't a harmonic of
Ma's respiratory cycle. Actually, if it's not that's kind of an even
more interesting question.
There are weak multiplicative
effects between maternal and fetal signals, as you'd expect.
This makes me think of an old Stroboconn/Peterson tuner. Obviously,
those are solving a much simpler problem. I'd be tempted to play
with the aliasing/sidebands.
The peterson/Stroboconn had a base model of the frequency under
measurement and provided a visual , intentionally aliased display
of the difference. It literally wagonwheeled.
This probably isn't much help, but it's clearly a profound problem.
Seems like a thing more for metaphor than for mechanism. Find the story
and the mechanism reveals itself. I'd almost bet that there's a model in
the brain of every neonatalist.
(I posted this in comp.dsp a couple of weeks ago, but most of the actual
DSP people seem to have disappeared, so the discussion petered out
fairly fast. Trying again here.)
Phil Hobbs wrote:
(I posted this in comp.dsp a couple of weeks ago, but most of the actualCrap. Sorry!
DSP people seem to have disappeared, so the discussion petered out
fairly fast. Trying again here.)
Cheers
Phil Hobbs
On Sun, 6 Jun 2021 14:45:11 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
Phil Hobbs wrote:
(I posted this in comp.dsp a couple of weeks ago, but most of the actual >>> DSP people seem to have disappeared, so the discussion petered outCrap. Sorry!
fairly fast. Trying again here.)
Sorry about what ?
It's an interesting project but my digital PLL skills are a bit
lacking. At least in software which is where I would like to be
better at.
I do know about acquiring ECGs but only using diff amps.
Might be a good question for the "dsprelated" forum along with embeddedrelated and all that stuff.
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