U.S. patent application number 10/728548 was filed with the patent office on 2004-05-06 for system and method for optically monitoring the concentration of a gas in a sample vial using photothermal spectroscopy to detect sample growth.
Invention is credited to Bachur, Nicholas Robert JR..
Application Number | 20040086956 10/728548 |
Document ID | / |
Family ID | 25399215 |
Filed Date | 2004-05-06 |
United States Patent
Application |
20040086956 |
Kind Code |
A1 |
Bachur, Nicholas Robert
JR. |
May 6, 2004 |
System and method for optically monitoring the concentration of a
gas in a sample vial using photothermal spectroscopy to detect
sample growth
Abstract
A system and method for monitoring the concentration of a medium
in at least one container using photothermal spectroscopy. The
medium can be a gas, such as oxygen or carbon dioxide, or a solid
or liquid. The system and method each employs an energy emitting
device, such as a laser or any other suitable type of light
emitting device, which is adapted to emit a first energy signal
toward a location in the container. The first energy signal has a
wavelength that is substantially equal to a wavelength at which the
medium absorbs the first energy signal so that absorption of the
first energy signal changes a refractive index of a portion of the
medium. The system and method each also employs a second energy
emitting device, adapted to emit a second energy signal toward the
portion of the medium while the refractive index of the portion is
changed by the first energy signal, and a detector, adapted to
detect a portion of the second energy signal that passes through
the portion of the medium. The system and method each further
employs a signal analyzer, adapted to analyze the detected portion
of the second energy signal to determine an amount of a sample in
the container based on a concentration of the medium in the
container. In particular, the signal analyzer can analyze the
detection portion of the second energy signal to determine whether
the sample includes an organism which consumes or emits the
medium.
Inventors: |
Bachur, Nicholas Robert JR.;
(Monkton, MD) |
Correspondence
Address: |
BECTON, DICKINSON AND COMPANY
1 BECTON DRIVE
FRANKLIN LAKES
NJ
07417-1880
US
|
Family ID: |
25399215 |
Appl. No.: |
10/728548 |
Filed: |
December 5, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10728548 |
Dec 5, 2003 |
|
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|
09892012 |
Jun 26, 2001 |
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Current U.S.
Class: |
435/34 ;
435/287.5; 435/288.7 |
Current CPC
Class: |
G01N 21/171
20130101 |
Class at
Publication: |
435/034 ;
435/287.5; 435/288.7 |
International
Class: |
C12M 001/34 |
Claims
What is claimed is:
1. A system for monitoring the concentration of a medium in at
least one container, comprising: an energy emitting device, adapted
to emit a first energy signal toward a location in said container,
said first energy signal having a wavelength that is substantially
equal to a wavelength at which said medium absorbs said first
energy signal so that absorption of said first energy signal
changes a refractive index of a portion of said medium or an
adjoining medium; a second energy emitting device, adapted to emit
a second energy signal toward said portion of said medium while
said refractive index of said portion of said medium is changed by
said first energy signal; and a detector, adapted to detect a
portion of said second energy signal that passes through said
portion of said medium.
2. A system as claimed in claim 1, further comprising: a signal
analyzer, adapted to analyze said detected portion of said second
energy signal to determine an amount of a sample in said container
based on a concentration of said medium in said container.
3. A system as claimed in claim 1, wherein: said medium or
adjoining medium includes a gas; and said first energy emitting
device is adapted to emit said first energy signal at said
wavelength at which said gas absorbs said first energy signal.
4. A system as claimed in claim 1, wherein: said medium or
adjoining medium includes a liquid; and said first energy emitting
device is adapted to emit said first energy signal at said
wavelength at which said liquid absorbs said first energy
signal.
5. A system as claimed in claim 1, wherein: said medium or
adjoining medium includes a solid; and said first energy emitting
device is adapted to emit said first energy signal at said
wavelength at which said solid absorbs said first energy
signal.
6. A system as claimed in claim 1, wherein: said medium includes
oxygen; and said first energy emitting device is adapted to emit
said first energy signal at said wavelength at which oxygen absorbs
said first energy signal.
7. A system as claimed in claim 1, wherein: said medium includes
carbon dioxide; and said first energy emitting device is adapted to
emit said first energy signal at said wavelength at which carbon
dioxide absorbs said first energy signal.
8. A system as claimed in claim 1, wherein: said medium includes
one of NH.sub.3, H.sub.2S, CH.sub.4 or SO.sub.2; and said first
energy emitting device is adapted to emit said first energy signal
at said wavelength at which said one of NH.sub.3, H.sub.2S,
CH.sub.4 or SO.sub.2 absorbs said first energy signal.
9. A system as claimed in claim 1, wherein: said first energy
emitting device includes a laser which is adapted to emit laser
light as said first energy signal.
10. A system as claimed in claim 1, wherein: said second energy
emitting device includes a laser which is adapted to emit laser
light as said second energy signal.
11. A method for monitoring the concentration of a medium in at
least one container, comprising: emitting a first energy signal
toward a location in said container, said first energy signal
having a wavelength that is substantially equal to a wavelength at
which said medium absorbs said first energy signal so that
absorption of said first energy signal changes a refractive index
of a portion of said medium or an adjoining medium; emitting a
second energy signal toward said portion of said medium or
adjoining medium while said refractive index of said portion of
said medium is changed by said first energy signal; and detecting a
portion of said second energy signal that passes through said
portion of said medium or adjoining medium.
12. A method as claimed in claim 11, further comprising: analyzing
said detected portion of said second energy signal to determine an
amount of a sample in said container based on a concentration of
said medium in said container.
13. A method as claimed in claim 11, wherein: said medium includes
a gas; and said first energy signal is emitted at said wavelength
at which said gas absorbs said first energy signal.
14. A method as claimed in claim 11, wherein: said medium includes
a liquid; and said first energy signal is emitted at said
wavelength at which said liquid absorbs said first energy
signal.
15. A method as claimed in claim 11, wherein: said medium includes
a solid; and said first energy signal is emitted at said wavelength
at which said solid absorbs said first energy signal.
16. A method as claimed in claim 11, wherein: said medium includes
oxygen; and said first energy signal is emitted at said wavelength
at which oxygen absorbs said first energy signal.
17. A method as claimed in claim 11, wherein: said medium includes
carbon dioxide; and said first energy signal is emitted at said
wavelength at which carbon dioxide absorbs said first energy
signal.
18. A method as claimed in claim 11, wherein: said medium includes
one of NH.sub.3, H.sub.2S, CH.sub.4 or SO.sub.2; and said first
energy signal is emitted at said wavelength at which said one of
NH.sub.3, H.sub.2S, CH.sub.4 or SO.sub.2 absorbs said first energy
signal.
19. A method as claimed in claim 11, wherein: said first energy
emitting step includes energizing a laser to emit laser light as
said first energy signal.
20. A method as claimed in claim 11, wherein: said second energy
emitting step includes energizing a laser to emit laser light as
said second energy signal.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Related subject matter is disclosed in a U.S. patent
application of Nicholas R. Bachur, Jr. et al. entitled "System and
Method for Optically Monitoring the Concentration of a Gas, or the
Pressure, in a Sample Vial to Detect Sample Growth" (Attorney
Docket No. P-5026), the entire contents of which is incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a system and method for
optically monitoring the concentration of a gas in a sample vial
using photothermal spectroscopy to detect the presence of sample
growth. More particularly, the present invention relates to a
system and method employing an excitation source, such as a diode
laser, which is used to excite gas, such as carbon dioxide, in a
sample vial to create a gas lens in the sample vial, and an
interrogation source, such as another diode laser, which emits
light through the gas lens to a detector which measures the degree
that the light is refracted by the gas lens to determine the
concentration of the gas in the sample vial, which is
representative of microorganism growth in the sample vial.
[0004] 2. Description of the Related Art
[0005] Many medical diagnoses require that a fluid sample, such as
a blood sample, be taken from a patient, cultured in a growth
medium, and then examined for the presence of a pathogen believed
to be causing the patient's illness. The growth medium provides
nutrients that allow the pathogen, such as a bacteria, virus,
mycobacteria, mammalian cells or the like, to multiply to a
sufficient number so that their presence can be detected.
[0006] In some cases, the pathogen can multiply to a large enough
number so that it can be detected visually. For example, a portion
of the culture can be placed on a microscope slide, and visually
examined to detect for the presence of a pathogen of interest.
[0007] Alternatively, the presence of a pathogen or other organism
can be detected indirectly by detecting for the presence of
byproducts given off by the microorganism during its growth. For
example, certain microorganisms such as mammalian cells, insect
cells, bacteria, viruses, mycobacteria and fungi consume oxygen
during their growth and life cycle. As the number of microorganisms
increases in the sample culture, they naturally consume more
oxygen. Furthermore, these oxygen consuming organisms typically
release carbon dioxide as a metabolic byproduct. Accordingly, as
the number of organisms present increases, the volume of carbon
dioxide that they collectively release likewise increases.
[0008] Several methods exist for detecting the presence of carbon
dioxide in a sample to determine whether organisms are present in
the sample. For example, an instrument known as the Bactec.RTM.
9050 manufactured by Becton Dickinson and Company detects for the
change in color of an indicator to determine whether carbon dioxide
is present in a sample. That is, each sample is collected in a
respective sample vial containing an indicator medium having a
chemical that reacts in the presence of carbon dioxide to change
color. A light sensor detects the color of the indicator medium in
the sample vial when the sample vial is loaded into the instrument.
If the sample contains an organism which emits carbon dioxide, the
reflected or fluorescent intensity of the indicator medium will
change in response to the presence of carbon dioxide. The light
sensor will therefore detect this change in intensity, and the
instrument will thus indicate to an operator that an organism is
present in the sample contained in the sample vial. Other examples
of instruments for detecting the presence of organisms in a sample
by detecting for the change in carbon dioxide in the sample are
described in U.S. Pat. Nos. 4,945,060, 5,164,796, 5,094,955 and
5,217,876, the entire contents of each of these patents are
incorporated herein by reference.
[0009] Alternatively, instead of detecting for the presence of
carbon dioxide to detect the presence of an oxygen consuming
microorganism, it is possible to detect for a depletion in the
concentration of oxygen in the sample of interest. In such a
system, the sample vial includes an indicator whose color or
fluorescence changes as the concentration of oxygen in the vial
changes. This change in color or fluorescence can be detected by an
instrument, which can provide an indication to a technician that
oxygen in the sample is being depleted by an oxygen consuming
organism within the sample. An instrument employing this oxygen
detecting technique is described in U.S. Pat. No. 5,567,598, the
entire contents of which are incorporated herein by reference.
[0010] The presence of oxygen consuming organisms can also be
detected by detecting for a change in pressure in a sealed sample
vial containing the sample of interest. That is, as oxygen in a
closed sample vial is depleted by oxygen consuming organisms, the
pressure in the sealed sample vial will change. The pressure will
further change in the sample vial as the organisms emit carbon
dioxide. Therefore, the presence of such organisms can be detected
by monitoring for a change in pressure in the closed sample vial.
Instruments that are capable of detecting changes in pressure in
the sample vial are described in U.S. Pat. Nos. 4,152,213,
5,310,658, 5,856,175 and 5,863,752, the entire contents of each of
these patents are incorporated herein by reference.
[0011] It is noted that the techniques described above each detect
for the presence of oxygen or carbon dioxide in a sample vial by
detecting the change in a state or condition of an indicator other
than the oxygen or carbon dioxide itself. For example, certain of
the techniques detect for a change in color of an indicator, while
others detect for a physical change, such as the movement of a
diaphragm which indicates a change in pressure. These techniques
can therefore be susceptible to erroneous results if, for example,
the indicators themselves are inaccurate.
[0012] Accordingly, to avoid such errors, detection probes or
sensors can be inserted directly into the sample vial to detect for
the presence of carbon dioxide or oxygen directly. An instrument
for detecting for the presence of carbon dioxide in a sample
directly is described in U.S. Pat. No. 4,971,900, the entire
contents of which are incorporated herein by reference. This probe
technique, however, is an invasive technique which requires that a
sensor or probe be inserted directly into the sample vial
containing the sample. This technique can prove hazardous because
the probes can become contaminated with the organism present in the
sample. Moreover, when the probes are being inserted into or
removed from the vial, the potentially hazardous organisms can
escape into the atmosphere, thus endangering the technician or
others in the general vicinity of the instrument.
[0013] Techniques have therefore been developed which are capable
of detecting the presence of, for example, carbon dioxide without
the need for detecting a change in the condition of an indicator,
and without the use of an invasive detector or probe. In one
technique, infrared light is irradiated through the sample vial
containing the sample of interest. The infrared light passing
through the sample vial is detected by an infrared detector.
Because carbon dioxide absorbs infrared light within a certain
wavelength range, if any carbon dioxide is present in the sample
vial, infrared light within that particular wavelength range will
be absorbed by the carbon dioxide and thus not be detected by the
infrared detector. The signals from the infrared detector are
analyzed to determine whether any of the infrared light being
emitted into the sample vial is absorbed and thus not detected by
the infrared detector. If any absorption has occurred, the
instrument provides an indication that carbon dioxide is present in
the sample vial, and thus, a carbon dioxide producing organism is
likely present. Examples of instruments which perform this type of
technique are described in U.S. Pat. Nos. 5,155,019, 5,482,842 and
5,427,920, the entire contents of each are incorporated by
reference herein.
[0014] The infrared light detecting technique has advantages over
the technique described above which uses an invasive detector or
probe, because the technique reduces the possibility of
contamination. Furthermore, because the infrared light technique
directly detects for the presence of carbon dioxide instead of
detecting for a change in an indicator, more accurate results can
be attained. However, the infrared light technique has certain
disadvantages. For example, carbon dioxide absorbs infrared light
within a somewhat wide range of wavelength, which can also be
absorbed by other gases. Hence, if gases in the vial other than
carbon dioxide absorb some of the infrared light, the instrument
may provide a false indication that carbon dioxide is present
Accordingly, the accuracy of the infrared light technique described
in the patents referenced above is somewhat limited.
[0015] A need therefore exists for an improved non-invasive system
and method for detecting for the presence of oxygen or carbon
dioxide in a culture sample, to thus detect for the presence of an
oxygen consuming or carbon dioxide producing organism in the
sample.
SUMMARY OF THE INVENTION
[0016] An object of the present invention is to provide an improved
system and method for optically monitoring the concentration of a
gas in a sample vial to detect the presence of sample growth.
[0017] Another object of the present invention is to provide a
system and method employing photothermal spectroscopy to monitor
the concentration of a gas, such as oxygen or carbon dioxide, or
the concentration of a liquid or solid, in the sample vial to thus
detect for microorganism growth in the sample vial based on the
monitored concentration.
[0018] A further object of the present invention is to provide a
system and method capable of housing and incubating multiple sample
vials containing respective samples, and optically monitoring the
concentration of a medium in each of the sample vials by
photothermal spectroscopy to detect the presence of sample growth
in the vials based on the respective monitored concentrations.
[0019] These and other objects are substantially achieved by
providing a system and method for monitoring the concentration of a
medium in at least one container. The medium can be a gas, such as
oxygen or carbon dioxide, or a solid or liquid. The system and
method each employs an energy emitting device, such as a laser or
any other suitable type of light emitting device, which is adapted
to emit a first energy signal toward a location in the container.
The first energy signal has a wavelength that is substantially
equal to a wavelength at which the medium absorbs the first energy
signal so that absorption of the first energy signal changes a
refractive index of a portion of the medium.
[0020] The system and method each also employs a second energy
emitting device, adapted to emit a second energy signal toward the
portion of the medium while the refractive index of the portion or
portion of an adjoining medium is changed by the first energy
signal, and a detector, adapted to detect a portion of the second
energy signal that passes through the portion of the medium or
adjoining medium. The system and method each further employs a
signal analyzer, adapted to analyze the detected portion of the
second energy signal to determine an amount of a sample in the
container based on a concentration of the medium in the container.
In particular, the signal analyzer can analyze the detection
portion of the second energy signal to determine whether the sample
includes an organism which consumes or emits the medium.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] These and other objects, advantages and novel features of
the invention will be more readily appreciated from the following
detailed description when read in conjunction with the accompanying
drawings, in which:
[0022] FIG. 1 is a block diagram of a system employing multiple
incubation and measurement instruments according to an embodiment
of the present invention, which each uses photothermal spectroscopy
to monitor the concentration of a gas, such as oxygen or carbon
dioxide, in sample vials, to thus detect for microorganism growth
in the sample vials;
[0023] FIG. 2 is a detailed view of an instrument employed in the
system shown in FIG. 1;
[0024] FIG. 3 is a top view of the instrument shown in FIG. 2;
[0025] FIG. 4 is a detailed view of an example of a movable
monitoring assembly employed in the instrument shown in FIGS. 1-3
which uses photothermal spectroscopy techniques to monitor the
concentration of a gas in the sample vials;
[0026] FIG. 5 is another view of the monitoring assembly shown in
FIG. 4;
[0027] FIG. 6 is a detailed view of an example of a sensor head
assembly employed in the monitoring assembly shown in FIGS. 4 and
5;
[0028] FIG. 7 is a detailed view illustrating the sensor head
assembly shown in FIG. 6 retracted into the sensor head housing of
the movable monitoring assembly shown in FIGS. 4 and 5;
[0029] FIG. 8 is a detailed view showing the sensor head assembly
shown in FIG. 6 extended from another end of the sensor head
housing of the monitoring assembly shown in FIGS. 4 and 5;
[0030] FIG. 9 is a conceptual block diagram of an example of
electronic components used by the monitoring assembly to monitor
the concentration of one or more gasses in the sample vials;
[0031] FIG. 10 is a block diagram of an example of another type of
monitoring assembly that can be employed in the instrument shown in
FIGS. 2 and 3;
[0032] FIG. 11 is another block diagram of the monitoring assembly
shown in FIG. 10;
[0033] FIG. 12 is a top view of the instrument shown in FIG. 2
including the monitoring assembly shown in FIGS. 10 and 11;
[0034] FIG. 13 is a side view of another type of instrument
employing another embodiment of a detector assembly which uses
infrared laser spectrography and dual wavelength modulation
techniques to monitor the concentration of a gas or the pressure in
sample vials according to another embodiment of the present
invention;
[0035] FIG. 14 is a front view of the instrument shown in FIG.
13;
[0036] FIG. 15 is a detailed perspective view of the carousel and
detector assembly arrangement in the instrument shown in FIGS. 13
and 14;
[0037] FIG. 16 is a side view of the carousel and detector head
arrangement shown in FIG. 15; and
[0038] FIG. 17 is a detailed view of the detector assembly
arrangement as shown in FIGS. 15 and 16.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0039] A system 100 for detecting growth of microorganisms in
sample cultures according to an embodiment of the present invention
is shown in FIG. 1. As illustrated, the system 100 includes a
plurality of incubation and measurement modules 102 that are
connected to a central computer 104. The central computer 104 can
control the incubation temperatures and times, as well as the
timing of the measurements performed by the modules 102, and can
collect and classify the data readings obtained by the modules 102.
The system 100 can also include a data output device, such as a
printer 106, that can be controlled by the central computer 104 to
print data readings obtained by the incubation and measurements
modules 102.
[0040] Further details of the incubation and measurement modules
102 are shown in FIGS. 2 and 3. As illustrated, each incubation and
measurement module 102 in this example includes a housing 108 and
two shelves 110 that can be slid into and out of the housing 108 in
a direction along arrow A. Each shelf 110 includes a plurality of
openings 112, each of which is adapted to receive a sample vial
114. The openings 112 are arranged in a plurality of rows and
columns as shown, and each shelf 110 can have any practical number
of openings. For example, the openings 112 can be arranged in nine
rows, with nine columns in each row, thus totaling 81 openings 112
per shelf 110.
[0041] When a sample culture is to be analyzed by the incubation
and measurement module 102, the sample culture is placed in a
sample vial 114, and the sample vial 114 is loaded into a
respective opening 112 in the incubation and measurement module
102. The sample vial 114 is a closed sample vial in this example.
The incubation and measurement module 102 can further include a
keyboard, a barcode reader, or any other suitable interface that
enables a technician to enter information pertaining to the sample
into a database stored in a memory in the incubation and
measurement module 102, in the central computer 104, or both. The
information can include, for example, patient information, sample
type, the row and column of the opening 112 into which the sample
vial 114 is being loaded, and so on.
[0042] Each incubation and measurement module 102 further includes
a movable monitoring assembly 116 which is capable of monitoring
the contents of a medium in the sample vials 114 through the use of
a technique known as photothermal spectroscopy. The principles of
photothermal spectroscopy are generally described in a publication
by Stephen E. Bialkowski entitled "Photothermal Spectroscopy
Methods for Chemical Analysis", John Wiley & Sons, Inc., 1996,
the entire content of which is incorporated by reference
herein.
[0043] Details of the movable monitoring assembly 116 will now be
described with reference to FIGS. 4-9. As shown, the monitoring
assembly 116 includes a sensor head housing 118 which houses a
sensor assembly 120 that includes a plurality of lasers 122 and 124
and a detector 126, the details of which are described below.
[0044] Sensor head housing 118 is movably mounted to a vertical
shaft 128 and can be moved in the "Y" direction along the vertical
shaft 128 by, for example, a motor and pulley arrangement (not
shown) or any other type of arrangement as can be appreciated by
one skilled in the art. As further illustrated, vertical shaft 128
is movably mounted to a horizontal shaft 130, and can be moved
along the "Z" direction along horizontal shaft 130 by a motor or
pulley assembly (not shown) or any other type of arrangement as can
be appreciated by one skilled in the art. As shown in FIG. 3,
monitoring assembly 116 can be mounted in a module 102 between the
two shelves 110 so that the sensor assembly 120 can take readings
from sample vials 114 in both shelves 110 as described in more
detail below.
[0045] As further shown in more detail in FIGS. 7 and 8, the sensor
assembly 120 is movably mounted in sensor head housing 118 so that
sensor assembly 120 can be retracted into the sensor head housing
118 along the "X" axis by a motor and gear or pulley arrangement
(not shown), or by any other type of arrangement as can be
appreciated by one skilled in the art. As shown in FIG. 8, the
sensor assembly 120 can be further moved along the "X" direction to
extend out of the other side of sensor head housing 118.
[0046] The operation of monitoring assembly 116 will now be
described with reference to FIGS. 3-9. As discussed briefly above,
central controller 104 (see FIG. 1) or a controller (not shown) in
module 102 can control movement of the sensor head housing 118 and
vertical shaft 128, as well as the extension of the sensor assembly
120, so that one pair of lasers 122 and 124 and one detector 126
are positioned on opposite sides of the neck of a sample vial 114
of interest loaded into an opening 112 in one of the shelves 110,
as shown conceptually in FIG. 9. In this example, laser 122 is a
diode laser that emits photons (an excitation laser beam) having a
wavelength at or about 2004 nanometers, which is in the absorbance
wavelength band for carbon dioxide. The laser 122 is energized by a
reference voltage source 132 and an alternating voltage source 134
as shown, under the control of, for example, central controller 104
or a controller in module 102.
[0047] When a photon emitted from laser 122 strikes a carbon
dioxide molecule and is absorbed by the carbon dioxide molecule,
thermal energy is released into the surrounding atmosphere in the
vial 114. The thermal energy heats the gas molecules in the
vicinity of the carbon dioxide molecule, and the local air density
is reduced. As this density is reduced, the refractive index
n.sub.D of the atmosphere in the vial 114 consequently is reduced.
This localized reduction in the refractive index n.sub.D of the
atmosphere in the neck of vial 114 creates a gas lens 136 that is
capable of refracting light.
[0048] While laser 122 is energized to form the gas lens 136 in the
neck of vial 114, second laser 124 is energized by a voltage source
138 under the control of, for example, central controller 104 or a
controller in module 102. In this example, laser 124 is a diode
laser that emits photons (an interrogation laser beam) at a
wavelength at or about 650 nanometers. The photons are directed
toward the intersection of the excitation laser beam emitted from
excitation laser 122 and the gas contained in the neck of vial 114
as shown. As the interrogation laser beam emitted from laser 124
strikes the gas lens 136 formed by the photothermal effect
described above, the interrogation laser beam is defocused or
refracted by the gas lens 136. It is noted that as the
concentration of carbon dioxide in the gas mixture increases, the
gas lens 136 formed will have a greater refractive effect on the
interrogation laser beam. That is, a small concentration of carbon
dioxide will form a lens 136 having a smaller refractive effect and
thus, the interrogation laser beam will be refracted less. However,
a large concentration of carbon dioxide will form a lens 136 having
a larger refractive effect and thus, the interrogation laser beam
will be refracted more. Improvements to the interrogation beam path
not shown in the figures such as optical lenses or spatial
filtering may be applied to increase the magnitude of the gas lens'
refractive effect.
[0049] As further shown in FIG. 9, detector 126, which in this
example is a silicon photodetector, receives the refracted
interrogation laser beam that has passed through gas lens 136. The
photocurrent output by detector 126 is input to a transimpedance
amplifier 140, and the output of amplifier 140 is input to a
lock-in amplifier 142. A reference voltage provided by reference
voltage source 132, which is representative of the modulation
waveform of the excitation laser 122, is also input to the lock-in
amplifier 142, which is capable of accommodating relatively poor
signal to noise ratios for the detected refracted interrogation
laser beam. The output of the lock-in amplifier 142 can be provided
to a display 144, that displays a waveform which is representative
of the concentration of carbon dioxide in the vial 114. The
waveform can be further analyzed to determine the amount of sample
growth in the vial 114, which in this example is proportional to
the concentration of carbon dioxide in the vial 114. Also, it is
noted that other signal processing techniques, such as those
employing discriminator circuits, ratio detectors, phase shift
demodulation, and so on, can be used to process the photocurrent
output by detector 126.
[0050] The sensor head housing 118 can then be moved along the "Y"
direction to take readings from that column of sample vials 114 in
the manner described above. The sensor assembly 120 can then be
retracted into the sensor head housing 118 as shown in FIG. 7 so
that the vertical shaft 128 and sensor head housing 118 can be
moved in the "Z" direction to be aligned with another column of
sample vials 114. The reading process can then be repeated to take
readings from that column of sample vials 114, and the retracting,
moving and reading process can be repeated for all columns of
sample vials 114.
[0051] Once readings have been taken from all of the sample vials
114 in all of the columns in shelf 110, the central controller 104,
for example, or a controller in the module 102, can control the
monitoring assembly 116 to take readings from the sample vials 114
in the opposite shelf 110 in a similar manner. In this event, the
central controller 104 or other controller controls the monitoring
assembly 116 to position the sensor head housing 118 for reading a
column of sample vials 114 in that shelf 110. Once the sensor head
housing 118 has been properly positioned, the sensor head housing
118 is controlled to extend the sensor assembly 120 from the
opposite end of the sensor head housing 118 as shown in FIG. 8. The
central controller 102 or other controller then controls the sensor
head housing 118 to move along the vertical shaft 128 so that the
sensor assembly 120 can take readings from all the sample vials 114
in that column in a manner similar to that described above.
[0052] Once all of the sample vials 114 in that column have been
read, the sensor head housing 118 is controlled to retract the
sensor assembly 120 as shown in FIG. 7. The central controller 104
or other controller then controls movement of the vertical shaft
128 and sensor head housing 118 in the "Z" direction along
horizontal shaft 130 until the sensor head housing 118 is
positioned to read another column of sample vials 114. The sensor
head housing 118 is then moved in the "Y" direction along vertical
shaft 128 as appropriate to take readings from the sample vials 114
that occupy column of sample vials 114. The process is then
repeated until readings have been taken from the sample vials 114
in all of the columns of that second shelf 110. Once all of the
readings have been taken, or in contemporaneously, the data can be
processed, displayed and analyzed in a manner discussed above.
[0053] The photothermal spectroscopy technique described above has
several advantages over other types of spectroscopy techniques used
to monitor gas metabolites as a representation of sample growth.
For example, the photothermal spectroscopy technique described
above has a sensitivity of 1000 to 10,000 times that of gas
absorption spectroscopy. Also, with the photothermal spectroscopy
technique, the sensitivity of the measurements tends to increase as
the volume of sample gas decreases. On the contrary, with the gas
absorption spectroscopy technique, the sensitivity of the
measurements increase with increased gas volume and decrease with
decreased gas volume. Accordingly, the photothermal spectroscopy
technique is more desirable for use in monitoring samples that
produce small volumes of metabolites.
[0054] In addition, the photothermal spectroscopy technique
described above can be used to interrogate liquids and solids using
the excitation laser 122 and interrogation laser 124, and the
detector 126, and the material being interrogated need not be
transparent. Furthermore, the excitation laser 122 need not be a
laser, but rather, can be any type of light source that is capable
of emitting light having a wavelength confined to the absorption
band of the gas being analyzed (e.g., carbon dioxide). However, the
light source must not emit light that has a wavelength within the
absorption bands of other gases that may be present in the
atmosphere in which the gas being analyzed is present. In other
words, for the above example, the excitation light source 122 must
not emit light having a wavelength that is within the absorption
band of any gases other than carbon dioxide that may also be
present in the neck of vial 114. For example, the light source 122
can be an LED that produces light throughout the absorption
spectrum of the gas under analysis (e.g., carbon dioxide) can be
used. Alternatively, a strobe lamp can be used in conjunction with
narrow band absorption filters which confine the wavelength of the
light entering the neck of the sample vial 114 to the absorption
band of carbon dioxide or any other gas or medium being analyzed.
Also, a tunable bandpass filter can be applied to the path of the
excitation light emitted from excitation light source 122 to permit
rapid scanning of many different types of analytes over a wide
wavelength range.
[0055] It is also noted that the interrogation laser 124 can be an
inexpensive type of laser, such as the type used in laser pointers.
Furthermore, the detector 126 can be a photodiode detector using an
inexpensive silicon material capable of detecting light in the
visual wavelength range rather than, for example, expensive
Aluminum Gallium Arsenide Phosphide detectors that are typically
used to detect light in the mid-infrared (mid-IR) range.
[0056] It is further noted that the photothermal spectroscopy
techniques described above can be used to analyze molecules other
than carbon dioxide. For example, the monitoring assembly 116 can
be used to monitor the concentration of oxygen (O.sub.2), NH.sub.3,
H.sub.2S, CH.sub.4 or SO.sub.2, in the head space above a liquid
growth medium in the sample vials 114 to detect a microorganisms'
metabolic activity. However, to detect these different molecules,
the excitation laser or light source 122 needs to be configured to
emit light within the absorption band of the molecules of interest.
For example, to detect NH.sub.3, a laser 122 that emits light in
the 1997 nanometer band is used. To detect H.sub.2S, a laser 122
that emits light in the 1570 nanometer band is used, to detect
CH.sub.4, a laser 122 that emits light in the 1650 nanometer band
is used, and to detect SO.sub.2, a laser that emits light in the
7280 nanometer band is used. The monitoring assembly 116 can also
be used to monitor the concentration of other molecules such as
glucose, creatine kinase-MB, and so on.
[0057] In addition, the monitoring assembly 116 can have different
configurations. For example, as shown in FIGS. 10-12, the
incubation and measurement module 102 can be configured to include
a plurality of monitoring assemblies 150, which are positioned in
the incubation and measurement modules 102 to obtain readings from
the sample vials 114. In the example shown in FIGS. 10 and 11, each
monitoring assembly 150 is configured to obtain measurements from
sample vials 114 inserted in two rows of openings 112. However, the
monitoring assembly 150 can be configured to obtain readings from
sample vial 114 in any number of rows of openings 112 as
desired.
[0058] The monitoring assembly 150 includes a movable assembly 152
which, in this example, is slidably coupled to a rail assembly 154
which is fixedly coupled to the top portion of shelf 110. A motor
and pulley assembly 156 comprising a motor 158, such as a D.C.
servo motor, and a pulley arrangement 160 that is driven by the
motor 158, is coupled to the rail assembly 154 and movable assembly
152. The motor 158 is controlled by, for example, central computer
104 or a computer in incubation and measurement module 102 to drive
the pulley arrangement 160 which, in response, drives movable
assembly 152 to slide along rail assembly 154 in a sample vial
reading direction indicated by arrow B in FIG. 10.
[0059] Moveable assembly 152 also includes a sensor 164 which
includes a light emitting device 166 and a detector 168 positioned
on opposite sides of a rail 170 of rail assembly 154. As the motor
and pulley assembly 156 drives the moveable assembly 152 along rail
assembly 154, the sensor 164 detects the openings 172 in the rail
170, and provides a signal indicative of this detection to central
computer 104 or a computer in the incubation and measurement module
102. The central computer 104 or a computer in the incubation and
measurement module 102 uses this detection signal to monitor the
position of the moveable assembly 152 along rail assembly 154.
Also, because each opening 172 corresponds to a respective column
of openings 112 in the shelf 110, the computer can determine which
sample vials 114 are being read by the detectors in the moveable
assembly 152 of monitoring assembly 150.
[0060] Moveable assembly 152 further includes a plurality of sensor
assemblies 174, the number of which corresponds to the number of
rows of sample vials 114 that the monitoring assembly 150 is
configured to read. That is, if the monitoring assembly 150 is
configured to read two rows of sample vials 114, the movable
assembly 118 will include two sensor assemblies 174. For
illustration purposes, FIGS. 10 and 11 show only one sensor
assembly 174. Like sensor assembly 118 described above, each sensor
assembly 174 includes an excitation laser or light emitting device
122, and an interrogation laser or light emitting device 124, as
described above. The laser 122 can be coupled to a laser assembly
176, which includes a cooling and heating device 178 that can cool
or heat the laser 122 to tune the frequency of the light being
emitted by the laser 122. In other words, because the laser 122
emits light having a single frequency, central computer 104 or
another controller can control the cooling and heating device 178
to change these frequencies, thus enabling the laser 122 to scan a
range of frequencies. The laser assembly 176 further includes a
heat sink 180 that can dissipate heat from the cooling and heating
device 178, and thus aid in controlling the temperature of the
laser 122. A similarly configured cooling and heating device 178
and heat sink 180 can be employed in the laser assembly 120
described above (see FIGS. 4-8) to heat and cool laser 122 in that
laser assembly as desired.
[0061] As further illustrated, each sensor assembly 174 includes a
detector 126 that is mounted to receive the laser light being
emitted by laser 124 that has passed through the gas lens 136 that
has been created by the light from the excitation laser 122 as
described above. The lasers 122 and 124, laser assembly 176, and
detector 126 are coupled to a laser and detector mounting bracket
182, that is further coupled to a movable mounting bracket 184. The
movable mounting bracket 184 is coupled along slide rails 186 to a
fixed mounting bracket 188, which is coupled to rail assembly 154
for movement along rail assembly 154 by motor and pulley assembly
156. A motor 190 is coupled to movable mounting bracket 184 and is
controlled by central computer 104 or a computer in the incubation
and measurement module 102 to move the movable mounting bracket 184
in a direction along arrow C as shown in FIG. 11. The motor 190 can
thus position lasers 122 and 124 and detector 126 at the
appropriate location along the neck of sample vial 114 to obtain
the most accurate readings. Also, as can be appreciated from the
above description, by moving the fixed mounting bracket 188 along
rail assembly 154, the motor and pulley assembly 156 translates the
entire movable assembly 152 including the lasers 122 and 124 and
detector 126 along the direction B in FIG. 10. This movement thus
positions the lasers 122 and 124 and detector 126 at the necks of
the sample vials 114 in the row of sample vials 114, so that
readings can be taken from all the sample vials 114 in the row.
[0062] It is further noted that the techniques described above are
not limited to use with a particular type of sample vial. Rather,
sample vial 114 can by any of the various types of culture vessels
capable of containing the growth media. The sample vials 114 also
can use various types of growth media to allow for detection and
observation of the growth of mammalian cells, insect cells,
bacteria, virus, mycobacteria, fungi, and other organisms which
produce or consume gases as part of their growth and life cycle.
The sample vials 114 can include a gas permeable membrane, slug,
aliquot, or target which permits the optical interrogation of the
gas signal and excludes intervening liquids or solids.
[0063] The above carbon dioxide, oxygen and other gas detection
techniques can also be used to test if materials which are designed
to be sterile are indeed free of contamination or infection with
any of the organisms listed above. Examples of materials which may
be tested includes processed foods, biological preparations such as
banked human blood, mammalian cell lines and prepared
injectables.
[0064] The photothermal spectroscopy described above for the
detection of carbon dioxide and oxygen, as well as other gases, can
also be used to enhance growth detection, provide presumptive
speciation, and to separate background metabolism such as that
caused by blood cells from bacterial or other cells. The techniques
described above could also be used to determine the quantity of
oxygen, carbon dioxide gas or other gases flushed into sealed
containers as a preservative or stabilizer to maintain a product's
shelf life or quality, or to detect immediate gas concentrations
within a gas stream used, for example, in a production supply
line.
[0065] In the arrangements discussed above, the light emitting
devices and sensors move with respect to the containers. However,
it is noted that the apparatus can be configured so that the
containers are housed in a rotor, drum, conveyor or the like and
controlled to move past the light emitting devices and sensors
which remain stationary. In this arrangement, the containers are
thus sensed as they move between the light emitting devices and
sensors, and the readings obtained representing the contents of the
containers are evaluated in the manners described above.
[0066] That is, as shown in FIGS. 13-17, an instrument 200 can
employ a stationary monitoring assembly as will now be described.
Specifically, instrument 200 includes a housing 202 and a door 204
that is coupled to the housing 202 by a hinge 206 and a piston
arrangement 208 to provide access to the interior chamber of the
housing 202. As discussed above with regard to a module 102,
instrument 200 can act as an incubation chamber to. incubate the
samples stored in the sample vials 114.
[0067] As shown in FIGS. 14-16, sample vials 114 are loaded into
openings 210 of a carousel 212. The carousel 212 is rotatably
mounted to a carousel mount 214, which are both housed in the
interior chamber of the housing 202. The carousel is operable by a
motor 216 under the control of a controller (not shown), such as
the type of controller described above, to rotate in a clockwise or
counter clockwise direction, as desired. The instrument 200 further
includes a control panel 218 which enables an operator to set the
parameters of the instrument 200, such as the incubation
temperature, speed of rotation of the carousel 212, and so on.
[0068] As further shown in FIGS. 14-17, instrument 200 includes a
stationary monitoring assembly 220 that is mounted to the carousel
mount 214 and is used to monitor the samples in the sample vials
114 in the manner similar to that described above. However, instead
of the monitoring assembly 220 moving with respect to the sample
vials 114, the carousel 212 rotates the sample vials 114 past the
respective sets of lasers 122 and 124 and detector 126 so that the
lasers 122 and 124 can emit laser light as described above through
the respective necks of the sample vials 114. The lasers 122, 124
and detector 126 are coupled to the type of circuitry shown, for
example, in FIG. 9, and described above. Accordingly, as the
carousel 212 is rotated to move the sample vials 114 past their
respective lasers 122 and 124 and detector 126, the photothermal
spectroscopy techniques described above are performed to monitor
the concentration of a gas, such as oxygen or carbon dioxide, or
the concentration of a liquid or solid, in the sample vial to thus
detect for microorganism growth in the sample vial based on the
monitored concentration.
[0069] Although only a few exemplary embodiments of the present
invention have been described in detail above, those skilled in the
art will readily appreciate that many modifications are possible in
the exemplary embodiments without materially departing from the
novel teachings and advantages of this invention. Accordingly, all
such modifications are intended to be included within the scope of
this invention as defined in the following claims.
* * * * *