This document discusses improving non-invasive blood analysis by expanding the medical spectral window. It summarizes prior work using wavelengths above 600nm to analyze blood properties like oxygenation and hematocrit. The author proposes targeting the thumb webbing instead of finger for absorption measurements, hypothesizing it could provide a wider spectral window. An apparatus was created to collect data from the thumb webbing and finger. Preliminary data from three subjects showed transmission increased significantly when measuring the thumb webbing compared to finger, with absorption ratios varying between subjects. Further research with more wavelengths and subjects is suggested.

1. Improving Non-Invasive Blood
Analysis by Expanding the Medical
Spectral Window
Katherine Paseman

2. Goal: Detect Medical Problems by non-
Invasively observing Physical
Properties of Blood
Physical Medical Example
Property of Diagnostic Problem
Blood (Symptom)
Fluorescence Zinc Protoporphyrin Iron Deficient
(ZPP) Concentration Anemia, Lead
Poisoning
Absorption Hemoglobin Anemia
Concentration
Scattering Hematocrit Low- Blood loss,
High - Dehydration

3. Prior Non-Invasive Blood Analysis
Work: Pulse Oximetry
 Used to non-invasively
determine Pulse and Blood
Oxygenation.
 Oxygenation determined
using Time dependent
behavior
 Red (660nm), Infrared (940
nm) -> Finger ->
Photodiode
Webster, JG. Design of Pulse Oxcimeters

4. Beers-Lambert Law
 Io = Ii 10 –2.303 ε(λ) c t /(64,500 g Hb/mole)
t – cm
 c – g/liter (A typical value of c for whole
blood is 150 g Hb/liter.)

5. Prior Work: Masimo pt 1
Most non-invasive blood λ Hb02 Absorption Hb Absorption
nm cm-1/M cm-1/M
sensors (e,g, Masimo)
extend the pulse 610 1506 9443.6
oximeter’s differential
620 942 6509.6
absorption trick. Like the
630 610 5148.8
pulse oximeter, they
660 319.6 3226.56
target the finger using
wavelengths above 600 700 290 1794.28
nm, the so called ”Medical 730 390 1102.2
Spectral Window”, to 805 844 730.28
collect enough light. 905 1209.2 769.8

6. Prior Work: Masimo pt 2

7. Prior Work: Samsung pt 1
Samsung’s attempt to use lower λ Hb02 Absorption Hb Absorption
wavelengths produced this cm-1/M cm-1/M
comment:
G Yoon <gyoon@snut.ac.kr> -
569nm is highly absorbing in 569 44496 45072
tissue and, at the same time,
569nm intensity is small 660 319.6 3226.56
compared with that at longer
wavelength. That is why you
may not get good signal. We 805 844 730.28
used a custom-made LED array
that has several chips of 569nm 940 1214 693.44
to increase intensity.
975 1144 389.288

8. Prior Work: Samsung pt 2

9. Our Research: Target Thumb Webbing
for Absorption instead of Finger
 Our idea is to extend the medical
spectral window by targeting the
thumb webbing for absorption
([Sabrina Paseman 2008] did
this for fluorescence)
 Our hypothesis is that we can get
better measurements than
Samsung with a wider spectrum
of wavelengths by offsetting the
increase in extinction coefficient
with the decrease in sample
thickness.
 Interrogating thumb webbing
would give us a wider window in
which to view medical problems

10. Implications
Increasing the size of the window would allow us to:
 Detect Sources of error in Samsung’s work
 See if there is a statistically significant difference
between the light absorption of systolic and diastolic
blood at 569, 660, 805, 940 and 975 nm.
 See if there is a statistically significant difference
between the fluorescence of systolic and diastolic
blood excited at 425 nm.

11. The Apparatus
 We’ve created an adjustable width clip
that fits either the subject’s index
finger or thumb webbing.
 One end of the clip holds the same 5-
LED package used by Samsung and the
other holds a fiber optic cable which
connects to a spectrometer.
 This allows us to double check the
LED’s wavelength, determine its
intensity, and observe any swamping
of fluorescing effects.
 Samsung’s work specifies “Three
variables of R569,805, R569,940, and
R569,975 were used for calibration and
prediction models. It means that four
wavelengths were used in hematocrit
monitoring.” It is for this reason we
look specifically at 569nm

12. Experimental Approach 1
 Clamp is adjusted to fit the subject’s index finger.
Subject removes finger so distance between
spectrometer and LED can be measured with a
micrometer.
 Thumb webbing is placed over the entire LED,
integration time is adjusted and data is collected.
 Subject removes thumb webbing and places index
finger over LED. Data is collected with the same
integration time and plotted on the same axis for
comparison

13. Data: 569 nm Subject 1
Thumb webbing
Index Finger
54054.5 counts
Integration Time: 404.05 ms
Width: 0.7175 cm
4131.5 counts

14. Findings
 Transmission increases 13 fold
 Samsung’s LED chip has an artifact at around 875nm
when the 569nm LED is lit. If their device uses a
photodiode to collect light, especially at low
intensities, much of the collected light would come
from the artifact rather than the 569nm absorption
 This method limited the quality of the readings we
could take from subjects with darker skin

15. Experimental Approach 2
 Hold led underneath the thumb webbing and
the spectrometer on the other side.
 Re-integrate the spectrometer and record the
integration time. Capture the graph.
 For data analysis, find the ratio between the
ratios of the peak counts at 569nm and the
integration time Counts thumb webbing
Integration timethumb webbing
Absorption Ratio =
Countsindex finger
Integration timeindex finger

16. Data: 569 nm Subject 1 Finger
Index Finger
Integration Time: 3097.90 ms
13640.500 counts

17. Data: 569 nm Subject 1 Webbing
Thumb Webbing
Integration Time: 99.70 ms
32847.801 counts

18. Data: 569 nm Subject 2 Finger
Index Finger
Integration Time: 1736.15 ms
61598.500 counts

19. Data: 569 nm Subject 2 Webbing
Thumb Webbing
60849.000 counts Integration Time: 208.91 ms

20. Data: 569 nm Subject 3 Finger
Index Finger
60534.000 counts Integration Time: 3808.11 ms

21. Data: 569 nm Subject 3 Webbing
Thumb Webbing
55602.750 counts Integration Time: 114.73 ms

22. Data: 569 nm
Subject Countstw Integrationtw Countsif Integrationif Ratio
(ms) (ms)
1 32847.801 99.70 13640.500 3097.90 74.825
2 60849.000 208.91 61598.500 1736.15 8.209
3 55602.750 114.73 60534.000 3808.11 30.488

23. Conclusions
 Transmission increases across the board but
varies from subject to subject
 Our suspicions about the artifact are affirmed
by our second set up

24. Further Research
 Collectdata for more subjects with varying
melanin contents
 Observe wavelengths other than 569 nm
 Investigate the potential for finding pulse
readings through thumb webbing