Patent Application
20120302866
The present invention relates to a photoacoustic imaging apparatus and a photoacoustic imaging method in which an acoustic wave that is generated from an inner portion of a sample by irradiating the sample with light is detected, and a detection signal thereof is processed to obtain image data of the inner portion of the sample.
In the medical field, research in optical imaging apparatuses that irradiate a living body with light from a light source, such as a laser, and that performs imaging on information of an inner portion of the living body obtained on the basis of incident light is being positively conducted. Photoacoustic tomography (PAT) is one example of optical imaging technology. In the photoacoustic tomography, a living body is irradiated with pulsed light generated from a light source, and an acoustic wave (typically, an ultrasonic wave) generated from living tissues that have absorbed energy of the pulsed light propagated through/scattered in the living body is detected. That is, by making use of the difference between light energy absorptance of a sample (such as a tumor) and those of tissues other than the sample, a transducer receives an elastic wave that is generated when the sample absorbs the light energy with which the sample is irradiated and expands instantaneously. By mathematically analyzing a detection signal, an optical characteristics distribution, in particular, absorption coefficient distribution of the inner portion of the living body can be obtained. These items of information can be used in quantitative measurements of specific substances in the sample, such as hemoglobin and glucose contained in blood. In recent years, using the photoacoustic tomography, preclinical research in which imaging is performed on blood vessels of small animals and clinical research applying this principle to diagnosis of, for example, breast cancer are positively being conducted.
In the photoacoustic tomography, ordinarily, in the process of mathematically analyzing the detection signal (reconstructing the image), the average sound speed in the inner portion of the sample is used for calculation. In general, the average sound speed in the inner portion of the sample used in reconstructing the image is set on the basis of, for example, experimental values and reference values. However, since the sound speeds at samples depend upon, for example, finished produces and a holding method of the samples, if the average sound speed used in reconstructing the image differs from an actual sound speed in the inner portion of the sample, an error occurs in the calculation for reconstructing the image, thereby considerably reducing the resolution of the obtained image. This is because a generally used image reconstruction theory assumes that the velocity of an acoustic wave that propagates in an imaging area is constant. This is a problem based on the principle of image reconstruction theory of photoacoustic tomography.
A document that discusses a technology of determining the sound speed in a sample using PAT is PTL 1. In PTL 1, an acoustic wave generated by irradiating a very small optical absorber (an acoustic generator) with light without a sample and an acoustic wave generated by irradiating a sample with light are obtained separately. The very small optical absorber is installed outside the location where the sample is installed. By comparing signals thereof with each other and analyzing them, a sound speed distribution of the inner portion of the sample can be calculated. It is known that the sound speed in a cancerous tissue differs locally from those in the vicinity thereof. By using an image obtained by this method, it is possible to diagnose the sample.
PTL 1: European Patent No. 1935346
However, in the PTL 1, the purpose is to determine the sound speed distribution in the inner portion of the sample. The PTL 1 does not discuss or suggest anything about determining the average sound speed in the inner portion of the sample. That is, the invention of the PTL 1 does not aim at overcoming the problems based on the principle that is characteristic of the aforementioned PAT. In addition, the PTL 1 does not even discuss the problems. In order to determine the sound speed in the sample, it is necessary to separately obtain a photoacoustic wave signal generated by irradiating the very small absorber (disposed at the outer side of the sample) with light and a photoacoustic wave signal generated by irradiating the sample with light. As a result, it is necessary to perform at least two photoacoustic signal measurements. Therefore, a long measurement time is required until image data is formed. Further, in order to determine the sound speed distribution in the inner portion of the sample, it is necessary to obtain the aforementioned two signals from a plurality of directions. Therefore, the number of signal measurements and the measurement time are considerably increased.
The present invention is carried out on the basis of such related art and understanding of the problems. The present invention provides a photoacoustic imaging diagnosis in which the average sound speed in an inner portion of a sample can be easily calculated from a detection signal obtained when an ordinary sample measurement is performed using PAT, to obtain high-resolution image data using a measured average sound speed.
According to the present invention, there is provided a photoacoustic imaging apparatus including a detector configured to output detection signals by detecting acoustic waves generated at surfaces and an inner portion of a sample by irradiating the sample with light; and a signal processing unit configured to generate image data using the detection signal,
wherein the signal processing unit calculates an average sound speed in the inner portion of the sample by using the detection signal of the acoustic wave generated at the surface of the sample and propagated through the inner portion of the sample, and generates the image data using the average sound speed and the detection signal of the acoustic wave generated at the inner portion of the sample.
The present invention can provide a photoacoustic imaging apparatus that can easily measure an average sound speed in an inner portion of a sample by receiving a photoacoustic wave that is generated at a surface of the sample and that propagates through the inner portion of the sample. This makes it possible to obtain high-resolution image data using an actually measured average sound speed.
The present invention will hereunder be described in detail with reference to the drawings. In general, corresponding structural components are given the same reference numerals, and the same descriptions will not be repeated.
First, the structure of a photoacoustic imaging apparatus according to an embodiment will be described with reference to
A basic hardware structure of the photoacoustic imaging apparatus according to the embodiment includes a light source 11, an acoustic wave probe 17 serving as a detector, and a signal processing unit 20. Pulsed light 12 emitted from the light source 11 is guided by an optical system 13 including, for example, a lens, a mirror, and an optical fiber, and illuminates a sample 15, such as a living body. When a portion of energy of the light that has propagated through the inner portion of the sample 15 is absorbed by an optical absorber 14 (consequentially serving as a sound source), such as a blood vessel, the optical absorber 14 is thermally expanded, so that an acoustic wave 16 (typically an ultrasonic wave) is generated. The acoustic wave is also called a photoacoustic wave. The acoustic wave 16 is detected by the acoustic wave probe 17 and is converted into a digital signal by a signal acquisition unit 19, after which the digital signal is converted into image data of the sample by the signal processing unit 20.
When the sample is a living body, the light source 11 emits light having a particular wavelength that is absorbed by a particular component among components of the living body. The light source may be provided integrally with the imaging apparatus according to the embodiment, or may be provided separately from the imaging apparatus. As the light source, it is desirable to use a pulsed light source that can generate pulsed light on the order of a few nanoseconds to several hundreds of nanoseconds. More specifically, in order to efficiently generate an acoustic wave, a pulse width on the order of 10 nanoseconds is used. Although as the light source, it is desirable to user a laser because a large output is obtained, it is possible to use, for example, a light-emitting diode instead of a laser. As the laser, it is possible to use various laser types, such as a solid-state laser, a gas laser, a dye laser, and a semi-conductor laser. Irradiation timing, waveforms, intensities, etc. are controlled by a controller (not shown).
In the present invention, for the wavelengths of the light source used, it is desirable to select wavelengths that are characteristically absorbed by the skin at the surface of the living body. More specifically, wavelengths in the range of from 500 nm to 1200 nm are selected. This is because, in a processing operation described below, it becomes easier to distinguish between a photoacoustic signal generated at the surface of the sample (for example, the skin) and a photoacoustic signal generated at the optical absorber (such as a blood vessel) in the inner portion of the sample.
Although the light 12 emitted from the light source 11 is typically guided to the sample by optical components, such as a lens and a mirror, it is possible to propagate the light using, for example, a light guide such as an optical fiber. The optical system 13 includes, for example, a mirror that reflects the light and a lens that converges and enlarges the light and changes the form of the light. Any optical component may be used as long as it causes the light 12 emitted from the light source to illuminate the sample 15 in a predetermined form. In general, it is better to increase the area of the light to a certain extent rather than converging the light with a lens from the viewpoints of increased safety and an increased diagnosis area of the living body. In addition, it is desirable that the area of the sample irradiated with the light be movable. In other words, it is desirable that the imaging apparatus according to the present invention be formed so that the light generated from the light source is movable along the sample. When the light is movable along the sample, it is possible to irradiate a wider range with the light. Further, it is more desirable that the area of illumination of the sample with the light (that is, the light that illuminates the sample) be movable in synchronism with the acoustic wave probe 17. Examples of a method of moving the area of irradiation of the sample with the light are a method using, for example, a movable mirror and a method that mechanically moves the light source itself.
The sample and the optical absorber do not constitute a part of the imaging apparatus according to the present invention, but will be described below. The photoacoustic imaging apparatus according to the present invention is primarily provided for, for example, diagnosing blood vessel diseases, malignant tumors of human beings and animals, etc., and observing a chemical treatment process. As the sample, the living body, more specifically, the breast, the fingers, the hands, the legs, etc. of human beings and animals may be diagnosed. The optical absorber 14 in the inner portion of the sample has a relatively high absorption coefficient in the inner portion of the sample. For example, if the object to be measured is a human body, oxygenated, deoxygenated hemoglobin, blood vessels including large amounts of these substances, and malignant tumors including a large number of new blood vessels correspond to the optical absorber. Although not shown, melanin, which exists near the surface of the skin, exists as an optical absorber at the surface of the sample. In the present invention, “living body information” refers to a generating source distribution of acoustic waves generated by the light irradiation, and indicates initial sound pressure distribution in the living body, optical energy absorption density derived therefrom, and a concentration distribution of substances making up tissues obtained from these items of information. For example, the concentration distribution of substances include oxygen saturation. These items of information that have been subjected to imaging are called image data.
The acoustic wave probe 17, which is a detector that detects acoustic waves, generated at the surface and the inner portion of the sample using the pulsed light, detects the acoustic waves and converts the acoustic waves into electric signals which are analog signals. The acoustic wave probe 17 may hereunder be simply referred to as a “probe” or a “transducer”. Any photoacoustic wave detector can be used as long as it can detect acoustic signals, such as a transducer making use of piezoelectric phenomena, a transducer making use of resonance of light, and a transducer making use of changes in capacity. The probe 17 in the embodiment typically includes a plurality of receiving elements that are one-dimensionally or two-dimensionally disposed. By using multidimensionally disposed elements in this way, it is possible to detect the acoustic waves simultaneously at a plurality of locations, to reduce detection time, and to reduce influences of, for example, vibration of the sample.
In the embodiment, the sample 15 is compressed and secured by a flat plate 18a. The light irradiation is performed through the flat plate 18a. The flat plate 18a holds the sample, and is formed of an optically transparent material for transmitting the light therethrough. Typically, acryl is used. When it is also necessary to transmit acoustic waves, in order to suppress reflection, it is desirable to use a material whose acoustic impedance does not differ much from that of the sample. When the sample is a living body, for example, polymethylpentene is typically used. Although the flat plate 18a may be formed to any thickness as long as the flat plate 18a is strong enough to suppress deformation of the flat plate 18a when it holds the sample, the thickness is typically on the order of 10 mm. Although the flat plate 18a may be of any size as long as it can hold the sample, the size of the flat plate 18a is basically the same as the size of the sample.
Although, in
It is desirable that the imaging apparatus according to the embodiment include the signal acquisition unit 19 that amplifies the electric signals obtained from the probe 17 and converts the electric signals from analog signals to digital signals. The signal acquisition unit 19 is typically formed by, for example, an amplifier, an A/D converter, and a field programmable gate array (FPGA) chip. When there are a plurality of detection signals obtained from the probe, it is desirable that the plurality of signals be processed at the same time. This makes it possible to reduce the time until images are formed.
In the specification, the term “detection signal” is a concept referring to the analog signal obtained from the probe 17 and the digital signal obtained thereafter after the analog-to-digital conversion. In addition, the detection signal is also called a “photoacoustic signal”.
The signal processing unit 20 calculates the average sound speed in the inner portion of the sample. This calculation is a characteristic feature of the present invention. Using the detection signal, obtained from the acoustic wave generated at the inner portion of the sample, and the above calculated average sound speed, image data of the inner portion of the sample is generated (that is, images are reconstructed). Although described in more detail later, that the average sound speed is calculated on the basis of the detection signal obtained from the acoustic wave (first acoustic wave) generated at the surface of the sample and propagated through the inner portion of the sample is a characteristic feature of the present invention. In actually calculating the average sound speed on the basis of the acoustic wave propagating through the inner portion of the sample, a calculated value is an actual measurement value of the average sound speed in the inner portion of the sample. Since the acoustic wave is generated at both the surface and the inner portion of the sample by irradiating the sample with the light, when the signal processing is performed with some thought, it is possible to calculate the average sound speed and generate the image data of the inner portion of the sample by one light irradiation operation.
In the signal processing unit 20, for example, a workstation is typically used. The calculation of the average sound speed, the image reconstruction processing, etc. are performed on the basis of a previously programmed software. For example, the software used in the workstation includes two modules, that is, a signal processing module for determining the average sound speed from the detection signals and for reducing noise and an image reconstruction module for the image reconstruction. In the photoacoustic tomography, ordinarily, as a preprocessing operation performed prior to the image reconstruction, for example, the noise reduction is performed on a signal received at each location. It is desirable that such a preprocessing operation be performed with the signal processing module. In the image reconstruction module, image data is formed by the image reconstruction. As an image reconstruction algorithm, for example, a back projection method in a Fourier domain or a time domain ordinarily used in tomographic technology is applied. Exemplary image reconstruction methods using PAT typically include a Fourier transformation method, a universal back projection method, and a filtered back projection method. Since these methods also use the average sound speed as a parameter, it is desirable to actually measure the average sound speed precisely in the present invention.
Depending on the circumstances, the signal acquisition unit 19 and the signal processing unit 20 may be integrated to each other. In this case, it is possible to generate the image data of the sample not only by a software processing operation performed at the workstation, but also by a hardware processing operation.
A display apparatus 21 displays the image data output by the signal processing unit 20. For example, a liquid crystal display apparatus is typically used as the display apparatus 21. The display apparatus 21 may be provided separately from a diagnostic imaging apparatus according to the present invention.
Next, the calculation of the average sound speed in the inner portion of the sample performed by the signal processing unit 20 will be described with reference to
Processing Step (1) (S201) is a step in which detection signal data is analyzed to calculate a first time (tsurface) lasting from the irradiation with the pulsed light to the detection of the first acoustic wave.
The digital signal (see
A method of distinguishing between the photoacoustic signal A generated in the inner portion of the sample and the photoacoustic signal B generated at the surface of the sample will hereunder be described. In the embodiment, the first acoustic wave is generated from the surface of the sample secured to the compression plate 18a. When, as shown in
If the surface of the sample that is irradiated with light is formed into a flat surface as shown in
A specific example of the processing is described below. For example, detection signals detected by the plurality of receiving elements can be compared with each other. When the plurality of receiving elements contact the surface of the sample, a plane wave reaches the plurality of receiving elements at substantially the same time. However, a spherical wave reaches the plurality of receiving elements at different times. Therefore, such a comparison makes it possible distinguish the acoustic wave generated from the surface of the sample from the acoustic wave generated from the inner portion of the sample.
All of the detection signals detected at the respective receiving elements may be averaged at all of the receiving elements. The term “all of the detection signals” means all of the detection signals obtained by receiving both the photoacoustic waves at the surface and the inner portion of the sample. In this processing, at the plurality of receiving elements, the detection signals originating from the acoustic waves from the surface of the sample and detected at the same time are strengthened, and the detection signals originating from the acoustic waves from the inner portion of the sample and detected at different times are weakened. Even for signals including, for example, noise, only the photoacoustic signals generated at the surface of the sample can be specified.
As the method of specifying the detection signal obtained from the acoustic wave generated at the surface of the sample, a method that makes use of pattern matching may be used. For example, the pattern matching is performed to specify an N-type detection signal that is characteristic of the acoustic wave generated from the surface of the sample, and a time position of the specified N-type detection signal is defined as a first time tsurface. More specifically, a time position of the N-type signal at a minimum peak or a maximum peak is defined as tsurface. After a detection signal other than that obtained from the acoustic wave generated from the surface of the sample is reduced using the above-described method, for example, a method of detecting the peak of the N-type detection signal obtained from the acoustic wave generated at the surface of the sample by searching for a maximum and a minimum value may be used. Even in this method, the time position of the N-type signal at the minimum peak or the maximum peak is defined as tsurface. By, for example, the aforementioned methods, the first time tsurface can be calculated. Of the time positions at the maximum peak and the minimum peak of the N-type detection signal obtained from the acoustic wave generated from the surface of the sample, which of these is to be the first time depends upon the characteristics of the probe.
Processing Step (2) (S202) is a step in which the average soundspeed in the inner portion of the sample is calculated from the first time (tsurface) and the distance between the surface of the sample and the detector.
An average velocity caverage of the sample is calculated from the first time (tsurface) obtained by the aforementioned processing, and a distance d1 between the surface of the sample at a light irradiation position and the probe. Here, the average velocity caverage can be obtained by a simple Expression (1) given below:
c
average
=a
1
/t
surface (1)
In the embodiment in which the probe 17 is provided directly on the sample 15, the first acoustic wave propagates only through the inner portion of the sample over the first time (tsurface), so that the average sound speed can be calculated using the aforementioned mentioned expression. This means that the average sound speed of the sample can be actually measured by using the acoustic wave generated at the surface of the sample and propagated through the inner portion of the sample.
In the embodiment shown in
Processing Step (3) (S203) is a step in which, using the calculated average sound speed, the detection signal of the acoustic wave generated at the inner portion of the sample is processed to form image data of the inner portion of the sample.
Using the average sound speed caverage obtained by the processing step (2), and a plurality of digital detection signals output from the signal acquisition unit 19, the image reconstruction processing is performed, so that data related to the optical characteristics of the sample is formed. For example, back projection in a Fourier domain or a time domain used in a general photoacoustic tomography is suitable.
By performing the above-described steps, it is possible to easily calculate the average sound speed using only the signals obtained by irradiating the sample with light, and to obtain an image whose resolution is not reduced due to a difference in sound speed by using the average sound speed in the image reconstruction.
An exemplary imaging apparatus using photoacoustic tomography to which the embodiment is applied will be described using the schematic view of the apparatus shown in
As shown in
After performing a noise reduction operation on the detection signals by discrete wavelet transformation, the image reconstruction was performed using the calculated average sound speed in the phantom. Here, using the universal back projection method, which is a time domain method, volume data was formed. A voxel interval used here was 0.05 cm. An imaging range was 11.8 cm*11.8 cm*4.0 cm. An exemplary image obtained at this time is shown in
Next, without measuring the average sound speed in the phantom, it was assumed that the average sound speed in the phantom was equal to 1540 m/sec, corresponding to the average sound speed in a living body, and the image reconstruction was performed again using the pieces of detection signal data stored in the WS. An exemplary image obtained at this time is shown in
Comparing
In the (1-1)th embodiment, the probe 17 is directly set at the sample 15. However, in this embodiment, it is assumed that a sample is compressed and secured at respective sides thereof by a first flat plate and a second flat plate disposed substantially parallel to each other. The probe 17 is set at a surface of the second flat plate. In this case, an acoustic wave generated at a surface of the sample secured by the first plate is defined as a first acoustic wave. Since the first acoustic wave is received by the probe 17 not only after it propagates through an inner portion of the sample but also after it propagates through the second plate, the first time (tsurface) explained in the (1-1)th embodiment is no longer the time taken for the first acoustic wave to pass through the inner portion of the sample. Accordingly, when an area other than the inner portion of the sample is included in a path that the first acoustic wave, indispensable to the calculation of the average sound speed, passes until it reaches the probe 17, it is necessary to determine the average sound speed taking this into consideration.
More specifically, from the first time (tsurface), the time required for the first acoustic wave to pass through the second plate is subtracted, so that a second time required for the first acoustic wave to pass through the inner portion of the sample is calculated. “The time required for the first acoustic wave to pass through the second plate” may be included in the signal processing module as a known value from the thickness of and the sound speed (a characteristic value obtained from a material) in the second plate.
A propagation distance of the first acoustic wave in the inner portion of the sample can be equated with a distance d2 between the first plate and the second plate. If, in the Expression (1), the second time is substituted for the first time (tsurface) and d2 is substituted for the distance d1, the average sound speed in the sample can be actually measured.
In the first embodiment, the average sound speed is calculated by using only the acoustic wave (first acoustic wave) generated from one location. In a second embodiment, the average sound speed is calculated by using acoustic waves generated at a plurality of surfaces of a sample. That is, the average sound speed is calculated from detection signals obtained from a first acoustic wave and a second acoustic wave generated at a surface of the sample that differs from the surface of the sample where the first acoustic wave is generated. This will hereunder be described on the basis of Example 2.
Example 2 in which, in an imaging apparatus using photoacoustic tomography, laser was used for irradiation from two directions will be described with reference to
As a result of irradiating such a phantom with the light, the first acoustic wave and the second acoustic wave were generated from surfaces of the phantom secured by the first plate 18a and the second plate 18b, and an acoustic wave was also generated from the optical absorber in the phantom. The ultrasonic transducer received these acoustic waves simultaneously at 345 channels. Then, using a signal acquisition unit 19 including an amplifier, an AD converter, and an FPGA, items of digital data of the photoacoustic signals at all of the channels were obtained. An exemplary received signal is shown in
The first acoustic wave passed through an inner portion of the phantom and the second plate 18b, and reached the probe 17. In contrast, the second acoustic wave did not pass through the inner portion of the phantom. The second acoustic wave passed only through the second plate 18b, and reached the probe 17. The time it took the first acoustic wave to pass through the second plate and the time it took the second acoustic wave to pass through the second plate were the same. Accordingly, if the difference between times of detections of the first and second acoustic waves, that is, a time difference of 35.8 microsec between B and B′ was calculated, the time taken for the first acoustic wave to pass through only the inner portion of the phantom was obtained. When the average sound speed in the phantom was calculated by dividing this time by 4.9 cm, that is, the distance between the surfaces of the phantom, it was 1370 m/sec.
Next, using the average sound speed calculated from the received pieces of digital data of the photoacoustic signals at all of the channels, image reconstruction was performed. Here, using the universal back projection method, which is a time domain method, volume data was formed. A voxel interval used at this time was 0.025 cm. An imaging range was 3.0 cm*4.6 cm*4.9 cm. An exemplary image obtained at this time is shown in
In such an embodiment, the average sound speed can be calculated by dividing the difference between the time of detection of the first acoustic wave and the time of detection of the second acoustic wave by the distance between the surface of the sample where the first acoustic wave is generated and the surface of the sample where the second acoustic wave is generated. This calculation method is effective when a path taken by the first acoustic wave and the second acoustic wave until they reach the probe 17 is common, and the difference between the lengths of the path taken by the first and second acoustic waves correspond to the length of the inner portion of the sample.
In the embodiment, since the average sound speed can be calculated by using the difference between the time of detection of the first acoustic wave and the time of detection of the second acoustic wave, it is not necessary to accurately know the timing of irradiation using pulsed light as in the first embodiment. Therefore, this embodiment is advantageous from the viewpoint that it is not influenced by measurement errors caused by external factors such as instability of a light source system. Although, in this embodiment, the second plate 18b is not required, even if the second plate 18b exists along the entire surface of the probe 17, the time taken for the acoustic wave to pass through the second plate 18b is canceled by an operation for eliminating the time difference. Therefore, correction as in the (1-2)th embodiment is not required.
In the embodiment, it is not necessary to irradiate both sides of the sample as in Example 2. Only one side of the sample may be irradiated as in the first embodiment. When one side is irradiated, light illuminating the surface of the sample secured to the first plate may propagate through the inner portion of the sample while being attenuated, and reach the surface of the sample at the opposite side. In this case, a very weak second acoustic wave may be generated from the surface of the sample at the opposite side. However, if the thickness of the sample is on the order of 4 cm, even from the viewpoint of reliably eliminating the time difference, it is necessary for the second acoustic wave to have a certain intensity. Therefore, it is desirable to irradiate the sample from both sides.
In the embodiment, the distance sensor in Example 2 is not required. The distance between the surface of the sample where the first acoustic wave is generated and the surface of the sample where the second acoustic wave is generated may be a known distance.
Although, in the first and second embodiments, at least one flat plate 18a is used to secure the sample, the present invention is not limited thereto. Example 3 in which measurements are carried out by setting the probe 17 at the sample whose shape is not regulated by a plate will be described below.
Example 3 will be described with reference to a schematic view of an apparatus shown in
The present invention is carried out by executing the following operations. That is, a software (program) for realizing the functions in the above-described embodiments is supplied to a system or an apparatus through a network or various storage media, and the system or a computer (or a CPU, MPU, etc.) of the apparatus reads out and executes the program.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2010-025864, filed Feb. 8, 2010, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-025864 | Feb 2010 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2011/000554 | 2/1/2011 | WO | 00 | 8/6/2012 |
