Patent Description:
Systems and methods that identify artifacts, and in particular vessels, in the surgical field during a surgical procedure provide valuable information to the surgeon or surgical team. hospitals lose billions of dollars annually in unreimbursable costs because of inadvertent vascular damage during surgery. In addition, the involved patients face a mortality rate of up to <NUM>%, and likely will require corrective procedures and remain in the hospital for an additional nine days, resulting in tens, if not hundreds, of thousands of dollars in added costs of care. Consequently, there is this significant value to be obtained from methods and systems that permit accurate determination of the presence of vessels, such as blood vessels, in the surgical field, such that these costs may be reduced or avoided.

Systems and methods that provide information regarding the presence of blood vessels in the surgical field are particularly important during minimally-invasive surgical procedures. Traditionally, surgeons have relied upon tactile sensation during surgical procedures both to identify blood vessels and to avoid inadvertent damage to these vessels. Because of the shift towards minimally-invasive procedures, including laparoscopic and robotic surgeries, surgeons have lost the ability to use direct visualization and the sense of touch to make determinations as to the presence of blood vessels in the surgical field. Consequently, surgeons must make the determination whether blood vessels are present in the surgical field based primarily on convention and experience. Unfortunately, anatomical irregularities frequently occur because of congenital anomalies, scarring from prior surgeries, and body habitus (e.g., obesity).

While the ability to determine the presence or absence of a vessel within the surgical field provides valuable advantages to the surgeon or surgical team and is of particular importance for minimally-invasive procedures where direct visualization and tactile methods of identification have been lost, the ability to characterize the identified vasculature provides additional important advantages. For example, it would be advantageous to provide information relating to the size of the vessel, such as the inner or outer diameter of the vessel. Size information is particular relevant as the Food and Drug Administration presently approves, for example, thermal ligature devices to seal and cut vessels within a given size range, typically less than <NUM> in diameter for most thermal ligature devices. If a thermal ligature device is used to seal a larger blood vessel or only part of a vessel, then the failure rate for a seal thus formed may be as high as <NUM>%.

In addition, it would be preferable to provide this information with minimal delay between vessel detection and vessel analysis, such that the information may be characterized as real-time. If considerable time is required for analysis, then at a minimum this delay will increase the time required to perform the procedure. In addition, the delay may increase surgeon fatigue, because the surgeon will be required to move at a deliberate pace to compensate for the delay between motion of the instrument and delivery of the information. Such delays may in fact hinder adoption of the system, even if the information provided reduces the risk of vascular injury.

Further, it would be advantageous to detect and analyze the vasculature without the need to use a contrast medium or agent. While the use of a contrast agent to identify vasculature has become conventional, the use of the agent still adds to the complexity of the procedure. The use of the agent may require additional equipment that would not otherwise be required, and increase the medical waste generated by the procedure. Further, the use of the contrast agent adds a risk of adverse reaction by the patient. <CIT> discloses an optical system that uses tissue fluorescence to determine tissue characteristics, particularly for real-time feedback control of tissue fusion procedures.

As set forth in more detail below, the present disclosure describes a surgical system including a system and method for determining vessel size embodying advantageous alternatives to the existing methods, which may provide for improved identification for avoidance or isolation of the vessel.

According to an aspect of the present disclosure, an optical surgical system is provided according to claim <NUM>.

The disclosure will be more fully understood from the following description taken in conjunction with the accompanying drawings. Some of the figures may have been simplified by the omission of selected elements for the purpose of more clearly showing other elements. Such omissions of elements in some figures are not necessarily indicative of the presence or absence of particular elements in any of the exemplary embodiments, except as may be explicitly delineated in the corresponding written description. None of the drawings is necessarily to scale.

A surgical system according to an embodiment of the present disclosure includes at least one light emitter, at least one light sensor, and a controller. The system may also include a surgical instrument as well.

The system determines a size of a vessel within a region proximate to a working end of the surgical instrument. In particular, it is believed that the system may be used to determine the size of a vessel within the region proximate to the working end of the surgical instrument regardless of the presence or the type of tissue surrounding the vessel. The embodiments of the system described below perform determinations relative to the presence and size of the vessel within the targeted region based on the light transmittance as determined by the light sensor, and thus the embodiments may appear facially similar to the technology used in transmissive pulse oximetry to determine the oxygen saturation (i.e., the percentage of blood hemoglobin that is loaded with oxygen). Careful consideration of the following disclosure will reveal that the disclosed system utilizes the light emitter(s) and light sensor(s) in conjunction with a controller (either in the form of unique circuitry or a uniquely programmed processor) to provide information regarding the presence and size of vessels that would not be provided by a pulse oximeter. Further, the disclosed embodiments include the use of a sensor array, the controller processing the pulsatile and non-pulsatile components of signals from that array to yield information regarding the diameter(s) of the vessel (e.g. the inner diameter or the resting outer diameter). Moreover, the disclosed technology may be utilized with vessels other than blood vessels, further separating the disclosed system and method from a transmissive pulse oximeter.

<FIG> and <FIG> illustrate an embodiment of such a surgical system <NUM> used to determine a size (e.g., diameter) of a vessel, V, within a region <NUM> of tissue, T, proximate to a working end <NUM> of a surgical instrument <NUM>. It will be understood that the vessel V may be connected to other vessels with the region <NUM> of tissue T, and in addition, the vessel V may extend beyond the region <NUM> so as to be in fluid communication with other organs (e.g., the heart) also found in the body of the patient. Furthermore, while the tissue T appears in <FIG> and <FIG> to surround fully the vessel V (in terms of both circumference and length) to a particular depth, this need not be the case in all instances where the system <NUM> is used. For example, the tissue T may only partially surround the circumference of and/or only surround a section of the length of the vessel V, or the tissue T may overlie the vessel V in a very thin layer. As further non-limiting examples, the vessel V may be a blood vessel, and the tissue T may be connective tissue, adipose tissue or liver tissue.

The surgical system <NUM> includes at least one light emitter <NUM> (or simply the light emitter <NUM>), at least one light sensor or detector <NUM> (or simply the light sensor <NUM>), and a controller <NUM> coupled to the light emitter <NUM> and the light sensor <NUM>. As noted above, the system <NUM> also may include the surgical instrument <NUM>.

The light emitter <NUM> is disposed at the working end <NUM> of the surgical instrument <NUM>. The light sensor <NUM> is also disposed at the working end <NUM> of the surgical instrument <NUM>. As illustrated in <FIG> and <FIG>, the light sensor <NUM> may be disposed opposite the light emitter <NUM> because the light emitter <NUM> and the light sensor <NUM> are disposed on opposing elements of the surgical instrument <NUM>, as explained in detail below.

The light emitter <NUM> is adapted to emit light of at least one wavelength. For example, the light emitter <NUM> may emit light having a wavelength of <NUM>. This may be achieved with a single element, or a plurality of elements (which elements may be arranged or configured into an array, for example, as explained in detail below). In a similar fashion, the light sensor <NUM> is adapted to detect light at the at least one wavelength (e.g., <NUM>). According to the embodiments described herein, the light sensor <NUM> includes a plurality of elements, which elements are arranged or configured into an array.

According to certain embodiments, the light emitter <NUM> may be configured to emit light of at least two different wavelengths, and the light sensor <NUM> may be configured to detect light at the at least two different wavelengths. For example, the light emitter <NUM> may emit light of three wavelengths, while the light sensor may detect light of three wavelengths. As one example, the light emitter <NUM> may emit and the light sensor <NUM> may detect light in the visible range, light in the near-infrared range, and light in the infrared range. Specifically, the light emitter <NUM> may emit and the light sensor <NUM> may detect light at <NUM>, at <NUM>, and at <NUM>. Such an embodiment may be used, for example, to ensure optimal penetration of blood vessel V and the surrounding tissue T under in vivo conditions.

In particular, the light emitted at <NUM> may be used as a reference to remove any variations in the light output because of motion and/or blood perfusion. The <NUM> wavelength corresponds to the isobestic point, where the absorption for both oxygenated and deoxygenated hemoglobin is equal. Consequently, the absorption at this wavelength is independent of blood oxygenation and is only affected by the change in light transmittance because of motion and/or changes in perfusion.

As stated above, the light sensor may be in the form of an array of light sensors. In fact, the array of light sensors <NUM> further includes at least one row of light sensors (see <FIG>); according to certain embodiments, the array <NUM> may include only a single row of light sensors, and the array <NUM> may be referred to in the alternative as a linear array. The at least one row of light sensors <NUM> includes a plurality of individual light sensors. The individual light sensors <NUM> may be disposed adjacent each other, or the light sensors may be spaced from each other. It may even be possible for the individual light sensors that define a row of light sensors to be separated from each other by light sensors that define a different row or column of the array. According to a particular embodiment, however, the array may comprise a charge coupled device (CCD), and in particular linear CCD imaging device comprising a plurality of pixels. As a further alternative, a CMOS sensor array may be used.

According to the embodiments of this disclosure, the individual light sensors <NUM> (e.g., pixels) are adapted to generate a signal comprising a first pulsatile component and a second non-pulsatile component. It will be recognized that the first pulsatile component may be an alternating current (AC) component of the signal, while the second non-pulsatile component may be a direct current (DC) component. Where the light sensor <NUM> is in the form of an array, such as a CCD array, the pulsatile and non-pulsatile information may be generated for each element of the array, or at least for each element of the array that defines the at least one row of the array.

As to the pulsatile component, it will be recognized that a blood vessel may be described as having a characteristic pulsation of approximately <NUM> pulses (or beats) per minute. While this may vary with the patient's age and condition, the range of pulsation is typically between <NUM> and <NUM> pulses (or beats) per minute. The light sensor <NUM> will produce a signal (that is passed to the controller <NUM>) with a particular AC waveform that corresponds to the movement of the blood through the vessel. In particular, the AC waveform corresponds to the light absorption by the pulsatile blood flow within the vessel. On the other hand, the DC component corresponds principally to light absorption and scattering by the surrounding tissues.

In particular, it is believed that the elements of the light sensor array <NUM> disposed on the opposite side of the vessel V from the light emitter <NUM> will have a higher AC signal than those elements where the vessel V is not disposed between the light emitter <NUM> and the light sensor array <NUM>, because the most marked fluctuations in the transmitted light will be caused by the vessel-associated pulsations. It is also believed that the elements of the array <NUM> disposed on the opposite side of the vessel V from the light emitter <NUM> will have a decreased DC signal compared to elements of the array <NUM> where the vessel V is not disposed between the light emitter <NUM> and the array <NUM>.

In fact, it is believed that particular regions of vessels, such as blood vessels, may undergo more pronounced pulsations that other regions, which differences are reflected in differences in the pulsatile component of the signal received from the array <NUM>. More particularly and with reference to blood vessels as a non-limiting example, as the heart pumps blood through the body, the muscular arteries pulse to accommodate the volume of blood being directed through the body. As this occurs, the middle layer (or tunica media) of the vessel expands and contracts. The expansion and contraction of the tunica media results in a relatively more significant change to the outer diameter of the vessel than to the inner diameter of the vessel. It is believed that the relatively more significant change in outer diameter that occurs during the expansion and contraction of the vessel causes the greatest fluctuations in the AC signal (which, as mentioned above, is related to the pulsations) over time at the edges of the vessel, as the outer diameter oscillates between an expanded position A and a resting positon B (see <FIG>).

Thus, according to the disclosed embodiments, the controller <NUM> is coupled to the light sensor <NUM>, and incudes a splitter <NUM> to separate the first pulsatile component from the second non-pulsatile component for each element of the light sensor array <NUM>. The controller <NUM> also includes an analyzer <NUM> to quantify the size of the vessel V within the region <NUM> proximate to the working end <NUM> of the surgical instrument <NUM> based on the pulsatile component. To display, indicate or otherwise convey the size of the vessel V within the region <NUM>, the controller <NUM> may be coupled to an output device or indicator <NUM> (see <FIG>), which may provide a visible, audible, tactile or other signal to the user of the instrument <NUM>.

In particular, the analyzer <NUM> may determine the magnitudes of the pulsatile components at the individual light sensors in the row of light sensors. Further, the analyzer may determine a first peak magnitude and a second peak magnitude of the pulsatile components. The analyzer may make the determination as to the first and second peak magnitudes after first determining the locations of transitions in the pulsatile and non-pulsatile components of the signal between higher and lower magnitudes, as explained in detail below. In addition, the analyze <NUM> may determine a resting outer diameter of the vessel V based on the first and second peak magnitudes of the pulsatile components.

According to certain embodiments, the analyzer <NUM> may determine the resting outer diameter of the vessel V by determining a first pair of positions along the row of light sensors where the magnitudes of the pulsatile component are a percentage (e.g., between <NUM>% and <NUM>%, such as <NUM>%) of the first (or second) peak magnitude, and a second pair of positions along the row of light sensors where the magnitudes of the pulsatile component are also the same percentage of the first (or second) peak magnitude, the second pair being disposed between the first pair of positions along the row of light sensors. The analyzer then determines a first distance between the first pair of positions and a second distance between the second pair of positions, and determines the resting outer diameter of the vessel as the average of the first and second distances. According to other embodiments, the analyzer <NUM> may instead use the inner pair of positions and a relationship between the inner and resting outer diameters. According to certain embodiments, the non-pulsatile component may be used instead of the pulsatile component.

According to certain embodiments, the splitter <NUM> and the analyzer <NUM> may be defined by one or more electrical circuit components. According to other embodiments, one or more processors (or simply, the processor) may be programmed to perform the actions of the splitter <NUM> and the analyzer <NUM>. According to still further embodiments, the splitter <NUM> and the analyzer <NUM> may be defined in part by electrical circuit components and in part by a processor programmed to perform the actions of the splitter <NUM> and the analyzer <NUM>.

For example, the splitter <NUM> may include or be defined by the processor programmed to separate the first pulsatile component from the second non-pulsatile component. Further, the analyzer <NUM> may include or be defined by the processor programmed to quantify the size of the vessel V within the region <NUM> proximate to the working end <NUM> of the surgical instrument <NUM> based on the first pulsatile component. The instructions by which the processor is programmed may be stored on a memory associated with the processor, which memory may include one or more tangible non-transitory computer readable memories, having computer executable instructions stored thereon, which when executed by the processor, may cause the one or more processors to carry out one or more actions.

In addition to the system <NUM>, the present disclosure includes embodiments of a method <NUM> of determining if a size of a vessel V within a region <NUM> proximate to a working end <NUM> of a surgical instrument <NUM>. The method <NUM> may be carried out, for example, using a system <NUM> as described above in regard to <FIG>. As illustrated in <FIG>, the method <NUM> of operating the system <NUM> includes emitting light at a working end of a surgical instrument at block <NUM> and sensing light at the working end of the surgical instrument at an array of light sensors comprising at least one row of light sensors at block <NUM>. As explained above, the light emitted may include light of at least two different wavelengths, and the sensing step may thus include sensing light of at least two different wavelengths. As also noted above, three different wavelengths of light may be used, and for example in the visible range and the near-infrared range. According to one embodiment, the light used may have wavelengths of <NUM>, <NUM>, and <NUM>.

The method <NUM> continues at block <NUM> wherein a pulsatile component is separated from a non-pulsatile component for individual sensors along the row of light sensors. The method <NUM> also includes determining the magnitudes of the pulsatile components at the individual light sensors in the row of light sensors at block <NUM>, determining a first peak magnitude and second peak magnitude of the pulsatile components at block <NUM>, and determining a resting outer diameter of the vessel based on the first and second peak magnitudes of the pulsatile components at block <NUM>.

More particular, as illustrated in <FIG>, the block <NUM> of the method <NUM> of <FIG> may include one or more actions. In particular, as illustrated in <FIG>, the action of block <NUM> may include determining a first pair and a second pair of positions along the row of light sensors at block <NUM>-<NUM>, where the magnitudes of the pulsatile component of the first and second pair of positions are a percentage of the first (or second) peak magnitude. The second pair of positions is disposed between the first pair of positions, as will be discussed relative to <FIG> below. In addition, the action of block <NUM> may include determining a first distance between the first pair of positions and a second distance between the second pair of positions at block <NUM>-<NUM>, and determining the resting outer diameter of the vessel V as the average of the first and second distances at block <NUM>-<NUM>.

To illustrate further the method <NUM> of operation of the system <NUM>, as illustrated in <FIG>, a plot is provided in <FIG>. In particular, <FIG> is a simulated plot of the magnitude of the pulsatile (AC) component for each element of a light sensor array and a plot of the magnitude of the non-pulsatile (DC) component for the same elements of the array. The lines are marked AC and DC to differentiate the two plots. According to this simulation, a vessel (specifically, a blood vessel) is disposed between the light sensor array and a light emitter array, with the vessel located generally between the light emitter array and the light sensor array in the region between <NUM> and <NUM> pixels.

As illustrated in <FIG>, the DC signal plot decreases from a relatively high value to a considerably lower value, and then increases from the lower value back to higher value at two different points (i.e., at points <NUM>, <NUM>) along the sensor array <NUM>. In accordance with the observations made above, the decrease in the magnitude of the DC signal in the region would be expected to occur where the vessel is disposed between the light emitter <NUM> and the light sensor <NUM>, and it therefore may be inferred that the vessel V is disposed between the point at which the DC signal plot transitions from the higher value to the lower value (i.e., point <NUM>) and the point at which the DC signal plot transitions from the lower value back to the higher value (i.e., point <NUM>).

In addition, the AC signal increases significantly from a relatively low value to a higher value at the point (i.e., point <NUM>) on one side of where the vessel is presumably located, and from a high value to a lower value (i.e., point <NUM>) on the other side of where the vessel is located. As also mentioned above, the relative increase in pulsatile (AC) signal is believed to occur where the vessel is disposed between the light emitter <NUM> and the light sensor <NUM>, and it therefore may be inferred that the vessel V is disposed between the point at which the AC signal plot transitions from the lower value to the higher value (i.e., point <NUM>) and the point at which the AC signal plot transitions from the higher value back to the lower value (i.e., point <NUM>).

While either the change in the DC signal or the change in the AC signal may be used to define a region of interest (ROI), the combination of the information on the transitions in the AC signal may be combined with the transitions in the DC signal to define an ROI to which the further consideration of the pulsatile (AC) information is confined. That is, the system <NUM> (and more particularly the controller <NUM>) may consider a subset of elements of all of the elements of the sensor array <NUM> in accordance with this information. This may be particularly helpful in eliminating fluctuations unrelated to the vessel in individual sensors along the array. According to such embodiments, the transitions between higher and lower values for each of the DC and AC plots are determined, and only the ROI where there is overlap between decreased DC magnitude and increased AC magnitude is considered. As illustrated in <FIG>, this region would be between the vertical bars (i.e., from about <NUM> pixels to <NUM> pixels).

According to embodiments of the present disclosure, as illustrated in <FIG>, the resting diameter of the vessel may be calculated based on a correlation observed between the expanded outer diameter of the vessel and the inner diameter of the vessel. In particular, it has been observed that the resting diameter of the vessel correlates to the average of the expanded outer diameter of the vessel and the inner diameter of the vessel. To perform this calculation, the expanded outer diameter (or line A) of the vessel is determined to be the distance between a first pair of points at which the AC magnitude is approximately <NUM>% of the peak AC magnitude: the leftmost occurrence (i.e., point <NUM>) prior to (or leading) the leftmost AC peak magnitude (i.e., at point <NUM>) and the rightmost occurrence (i.e., point <NUM>) after (or lagging) the rightmost AC peak magnitude (i.e., at point <NUM>). In addition, the inner diameter (or line C) is determined to be the distance between a second pair of points at which the AC magnitude is approximately <NUM>% of the peak AC magnitude: the leftmost occurrence (i.e., point <NUM>) after (or lagging) the leftmost AC peak magnitude (i.e., at point <NUM>) and the rightmost occurrence (i.e., point <NUM>) prior to (or leading) the rightmost AC peak magnitude (i.e., at point <NUM>). These distances may also be described as the distances between the two occurrences of <NUM>% peak AC magnitude outside and inside the peak AC magnitudes. It may also be said that the second pair is disposed between or inside the first pair.

It is not necessary to use the occurrences at <NUM>% peak AC magnitude according to all embodiments of the present disclosure. According to other embodiments, the inner diameter may be determined to be distance between the leftmost occurrence after (or lagging) the leftmost AC peak magnitude and the rightmost occurrence prior to (or leading) the rightmost AC peak magnitude of <NUM>% peak AC magnitude, while the expanded outer diameter also was determined at the <NUM>% peak AC magnitude occurrences described above.

Finally, as illustrated in <FIG>, the resting outer diameter (line B) may be determined to be the average between the inner diameter (line C) and the expanded outer diameter (line A).

According to other embodiments of the present disclosure, the determination of the resting outer diameter of the vessel V may be calculated without reference to two pairs of positons along the row of light sensors. More particular, the actions performed by the system <NUM> at the block <NUM> of the method <NUM> of <FIG> to determine the resting outer diameter of the vessel V may be as illustrated in <FIG>. According to this alternate method, the action of block <NUM> may include determining a pair of positions along the row of light sensors at block <NUM>-<NUM>' in between the two positons where the peak magnitudes occur. The single pair of positions (or "inner" pair) may occur where the magnitudes of the pulsatile component are a percentage of the first (or second) peak magnitude. For example, the inner pair may be defined by the pair of positions between the positions where the peak magnitudes occur corresponding to <NUM>% of the first (or second) peak magnitude. In addition, the action of block <NUM> may include determining a distance between the inner pair at block <NUM>-<NUM>'.

At block <NUM>-<NUM>', the distance between the inner pair of positions is then used to calculate the resting outer diameter. According to this method, as was the case in the method of <FIG>, the distance between the inner pair of positons is representative of the inner diameter of the vessel V. Further, it believed that the inner diameter of a vessel undergoing expansion and contraction varies to a far lesser degree (if at all) than the outer diameter. Moreover, it has been observed that the signal from the edges of the vessel may be obscured by the presence of tissue disposed about the vessel. Consequently, rather than attempting to approximate the outer diameter of the vessel, a relationship may be determined empirically between the inner diameter and resting outer diameter, which relationship may be used to calculate the resting outer diameter based on the measurement of the inner diameter, as determined in accordance with the actions of blocks <NUM>-<NUM>' and <NUM>-<NUM>'.

In its simplest form, the resting outer diameter may be determined to be a multiple of the inner diameter. According to other embodiments, the resting outer diameter may be calculated to be a multiple of the inner diameter with the addition of a constant term. <FIG> is a graph comparing the inner diameters and resting outer diameters of a set of muscular arteries. Based on this graph, a formula relating the outer diameter (y) with the inner diameter (x) was determined (y = <NUM>. 2x + <NUM>). Accordingly, for a given inner diameter determined at blocks <NUM>-<NUM>' and <NUM>-<NUM>', the formula may be used to calculate the resting outer diameter at block <NUM>-<NUM>'.

A further embodiment of a method that may be practiced using, for example, the system <NUM> illustrated in <FIG> is illustrated in <FIG>. The method <NUM> illustrated in <FIG> addresses a complication that may occur if the vessel is grasped tightly between the jaws of an instrument, such as is illustrated in <FIG> and <FIG>. In particular, the compression of the vessel V between the jaws of the surgical instrument <NUM> may change the pulsatile component of the signal, such that only a single peak may be observed, instead of the two peaks as illustrated in <FIG>.

The method <NUM> is similar to the method <NUM> in that light is emitted from the light emitter <NUM> at block <NUM>, and the transmitted light is sensed or detected by the light sensor array <NUM> at block <NUM>. The system <NUM> (or more particularly the controller <NUM>) operates to separate the non-pulsatile component of the signal from the pulsatile component of the signal at block <NUM>, and determines the magnitude of the pulsatile component at the individual sensors at block <NUM>.

At block <NUM>, the system <NUM> (controller <NUM>) then makes a determination as to the number of positons identified with a peak pulsatile magnitude at block <NUM>. According to certain embodiments, this determination may be performed after a region of interest is identified using transitions in the non-pulsatile component (e.g., from a higher magnitude to a lower magnitude) and optionally in the pulsatile component (e.g., from a lower magnitude to a higher magnitude). In fact, according to some embodiments, the determination at block <NUM> is performed once the transition in the non-pulsatile component of the signal from a higher magnitude to a lower magnitude is identified.

If the determination is made at block <NUM> that two peaks are present, for example, then the method <NUM> may proceed to blocks <NUM>, <NUM>, <NUM>, where a method similar to that described in regard to <FIG> is performed (although it will be appreciated that a method similar to that described in regard to <FIG> may be substituted). If the determination is made at block <NUM> that a single peak is present, then the method <NUM> may proceed to blocks <NUM>, <NUM>, <NUM>. In particular, a determination is made at block <NUM> as to a single pair of positions along the row of light sensors where the magnitudes of the pulsatile component are a percentage of the peak magnitude. For example, the pair may be defined by the pair of positions on either side of the peak magnitude (i.e., to the left or the right of the position corresponding to the peak magnitude) where the magnitude corresponds to <NUM>% of the peak magnitude. In addition, the system <NUM> (controller <NUM>) may determine the distance between this pair of positions at block <NUM>. The system <NUM> may then use the distance determined as the value for the inner diameter, and calculate the resting outer diameter using the relationship established between inner diameter and outer diameter, in a process similar to that described in regard to block <NUM>-<NUM>' in <FIG>.

It will be recognized that while the method <NUM> was described with reference to a determination as to how many peaks are present, the specifics as to how this determination is performed may differ among the various embodiments. For example, the determination may be made according to whether one peak is or two peaks are present. Alternatively, the determination may be made according to whether a single peak is present, with subsequent actions taken dependent upon whether the answer to this question is yes or no.

A further alternative to the methods described in <FIG> is to use the non-pulsatile component of the signal to determine the vessel outer diameter. As illustrated in <FIG>, the method <NUM> starts much like the methods <NUM>, <NUM>, in that light is emitted at block <NUM>, transmitted light is sensed or detected at block <NUM>, and pulsatile and non-pulsatile components are separated at block <NUM>. Unlike the methods above, the system <NUM> (controller <NUM>) interrogates the non-pulsatile component at block <NUM> to determine the non-pulsatile magnitude at individual sensors at block <NUM>. Moreover, unlike the methods above, the system <NUM> determines the positions along the row of light sensors where the non-pulsatile magnitude transitions from a higher value to a lower value and where the non-pulsatile magnitude transitions from a lower value back to a higher value at block <NUM>. This pair of positions, based on these transitions in the non-pulsatile component of the signal, is then used to determine the resting outer diameter at block <NUM>. For example, the distance between the pair of positions may be used as the estimate for the resting outer diameter, or a relationship based on empirical data may be used to calculate the resting outer diameter according to the distance between the pair of positions where the non-pulsatile component transitions.

Further enhancements may be included in the above embodiments, or may be practiced separately in combination to provide a further embodiment of a method for use with the surgical system <NUM>.

For example, relative to the detection of the region of interest, the contrast of the DC profile may be used to determine the presence of the region wherein the DC profile decreases and then increases (i.e., "dips"). According to this method, the contrast of the DC profile is defined as: <MAT> where N = the total number of sensors. The region of interest may then be determined using the first order derivative.

Furthermore, mirroring may be used to extract the "ideal" region of interest. It is believed that mirroring can be useful in this setting because vessels, such as arteries, can be expected to be symmetrical in structure. Thus, while the DC profile may not follow the symmetry of the vessels because tissue of differing thickness is disposed about the vessels, this expectation that the DC profile should be symmetrical can be used to improve the accuracy of at least the vessel size determination.

In addition, the DC profile may be used to adapt the intensity emitted by the light emitter <NUM>. In particular, it is believed that the intensity of the light emitter <NUM> plays an important role in the accuracy of vessel detection and vessel size determination. If the intensity of the light emitter <NUM> is set too low, the light may be absorbed by the tissue before reaching the sensor <NUM>. In such a circumstance, the sensor <NUM> may not be able to detect the pulsatile nature of the vessel, and it may be difficult to differentiate the vessel (e.g., artery) from the surrounding tissue (i.e., low resolution). On the other hand, if the intensity of the light emitter is set too high, only the portion of the sensor <NUM> located in the very center of the vessel may experience the decrease in non-pulsatile (DC) signal, which leasing to error in determining the region of interest and other spatial characteristics of the vessel. Therefore, it would be desirable to provide a method and mechanism for selection of the intensity of the light emitter <NUM> that would limit the consequences of using an intensity that was either too low or too high for conditions.

<FIG> illustrates an exemplary DC profile that will be used to discuss the various profile parameters that may be used to adapt the light emitter intensity such that it is neither too low nor too high for a particular setting. It will be recognized that the DC profile illustrated in <FIG> has four separate regions, labeled with Roman numerals I, II, III, and IV. Certain profile parameters are analyzed within regions I and IV, while other parameters are analyzed within regions II and III.

In particular, within regions I and IV, the relevant parameter is the derivative profile, while within regions II and III, the relevant parameters are the left and right angles, the contrast, the width profile and the symmetry. While the derivative profile is self-explanatory, it will be recognized that the left and right angles are determined using a straight line drawn from the point at which the derivative profile changes to a non-zero value (beginning of the "dip") to the lowest DC value (the bottom of the "dip") and as measured relative to the horizontal as illustrated in <FIG>, and the width profile is the distance between the lefthand edge (as viewed in <FIG>) of the "dip" to the right-hand edge. The contrast is determined using the equation provided above. In addition, a further parameter, referred to as the contrast to width ratio (CWR), may be determined by taking the ratio of the contrast to the width profile.

Starting with the derivative profile in regions I and IV, it is believed that when the emitter light intensity is neither too low nor too high, the derivative profile will be approximately zero in regions I and IV. Furthermore, it is believed that the left and right angles should be in the range of <NUM> to <NUM> degrees. It is also believed that the contrast should be within the range of <NUM> to <NUM>, and the width profile should not be too small nor too broad. In particular, it is believed that the CWR should be approximately <NUM> when the intensity Is neither too low nor too high. It is also believed that the profile should exhibit a relatively uniform symmetry between regions II and III, which may be quantified as a ratio of the width of the profile in region II to the width of the profile in region III. Here as well, it is believed the ratio should be approximately <NUM> when the intensity is neither too low nor too high.

<FIG> illustrate a series of DC profiles and AC profiles (DC profiles in solid line and AC profiles in dotted solid line) at different light intensities for the light emitter <NUM>. In all of the illustrations, the lines used to calculate the left and right angles have been added, although the regions I, II, III and IV have not been marked as such. However, one may easily determine the regions in <FIG> based on the presence of these lines. <FIG> illustrates a situation where the intensity of the light emitter was selected to be too low for conditions, while <FIG> illustrates a situation where the intensity of the light emitter was selected too high for conditions. On the other hand, <FIG> illustrates a situation where the intensity of the light emitter had been adapted to improve the determination of the size of the vessel.

Under certain circumstances, enhancements used generally with the DC profile may be used in conjunction with these parameters when adapting the light intensity of the light emitter. For example, mirroring may be used in conjunction with the other parameters when using the DC profile to adapt the light intensity of the light emitter <NUM>.

One method <NUM> using the above parameters to adapt the light intensity is illustrated in <FIG>. The DC profile is analyzed at block <NUM> for the presence of a dip in the DC profile. A determination is made at block <NUM> whether a dip is present, or not. If the determination is made at block <NUM> that the dip is present, the method <NUM> continues to block <NUM>; if not, the method <NUM> returns to block <NUM>.

At block <NUM>, the parameters discussed above are determined for the DC profile, and a series of comparisons are made relative to the ranges also discussed above. For example, at block <NUM>, a determination is made whether the derivative profile in regions I and IV are approximately zero. If the derivative profile is approximately zero, the method <NUM> continues to the determination at block <NUM>; if the derivative profile is not approximately zero, the light intensity is increased at block <NUM>, and the method <NUM> returns to block <NUM>.

At block <NUM>, a determination is made whether the left and right angles are within range. If the angles are within range, the method <NUM> proceeds to block <NUM>. If the angles are not within range, a subsequent determination is made at block <NUM> whether the angles fall outside the range because they are too large. If the angles are too large, then the method <NUM> proceeds to block <NUM> and the light intensity is increased; if the angles are outside the range because they are not too large (i.e., they are too small), then the method <NUM> proceeds to block <NUM> and the light intensity is decreased.

If the method <NUM> proceeds to block <NUM>, a determination is made whether the contrast to width ratio is approximately <NUM>. If the CWR is approximately <NUM>, then the method <NUM> proceeds to block <NUM> where the vessel size is determined. If the CWR is not approximately <NUM>, then the method <NUM> proceeds to block <NUM> where a determination is made whether the CWR is too large. If the CWR is too large, the light intensity is increased at block <NUM> and the method <NUM> returns to block <NUM>; if the CWR is not too large, the light intensity is decreased at block <NUM>, and the method <NUM> returns to block <NUM>.

As reflected in the foregoing embodiments, the non-pulsatile, or DC, component of the signal from the sensors <NUM> may be useful in determining, for example, a region of interest in an illumination pattern, determining the size (e.g., diameter) of a vessel (e.g., a blood vessel), and/or adapting the intensity emitted by the emitters <NUM>. Any of such aforementioned systems and methods may be further improved by providing or including a system and method that compensates for angular distortions, at least as to the non-pulsatile, or DC, component of the signal.

In this regard, some surgical instruments are known to have jaws with opposing surfaces that are parallel to each other. As a consequence, the light intensities received by sensors <NUM> disposed on one of the jaws (or more particular, attached to a surface of one of the jaws) are relatively similar. In such instruments, when the jaws are moved apart to permit a section of tissue to be disposed between the jaws for example, the distance between the opposing surfaces of the jaws changes by an equal amount along the length of the jaws. If emitters <NUM> are attached to one of the opposing surfaces, and sensors <NUM> are attached to the other of the opposing surfaces, then the distance between the individual emitters <NUM> and corresponding sensors <NUM> will change by an equal amount as the jaws are moved apart or together.

Many surgical instruments have jaws with opposing surfaces that are non-parallel to each other, however. In fact, the jaws may be pivotally connected to permit the angle between the opposing surfaces to be varied so that the jaws can be moved apart (or opened) to permit tissue to be disposed between the jaws, for example. A variable and angle dependent offset thus may be created between emitters <NUM> attached to one of the jaws and sensors <NUM> attached to the other of the jaws. For a given angle, the distance between the emitter <NUM> and the corresponding sensor <NUM> at the distalmost end of the jaw is greater than the distance between the emitter <NUM> and the corresponding sensor <NUM> at the proximal-most end of the jaw (i.e., the end of the jaw closest to the pivotal connection).

At smaller angles (and hence smaller distances), it is believed that the distortions caused by this offset may not be significant. As the angle between the jaws increases, it is believed that the distortion caused by this variation in distance between emitter <NUM> and sensor <NUM> becomes more pronounced for the different regions of the array along the length of the non-parallel jaws when compared to arrays of emitters and sensors arranged on a pair of parallel jaws.

Even without a tissue present between the jaws, the varying distances between the emitters <NUM> and the sensors <NUM> can distort the shape of the non-pulsatile, or DC, illumination pattern, or profile, determined using the sensors <NUM>. In a situation where each emitter <NUM> has equal radiant power, the unequal offset (i.e., unequal distances between the emitters <NUM> and the sensors <NUM>) creates a non-uniform illumination pattern along the sensor array. <FIG> illustrates the illumination pattern expected without any tissue disposed between the jaws. It is believed that the intensity will increase for sensors located further and further away from the distalmost end of the jaws (where the greatest distortion is believed to occur) until a maximum is reached. At this point, it is expected that there would be some reduction in intensity because the sensors nearest the pivot or joint would receive light from a single emitter that this not directly aligned with them. This would be contrasted with the uniform, constant illumination pattern that would be expected to be produced with parallel jaws having parallel opposing surfaces to which the emitters <NUM> and sensors <NUM> are attached.

It is further believed that a similar distortion can occur to the DC illumination pattern detected by the sensor array when a vessel is disposed between non-parallel jaws, for example. Consistent with the discussion above, it is believed that a vessel disposed between emitters <NUM> and sensors <NUM> arranged along opposing jaws will cause an inverted Gaussian-type absorption pattern (also referred to herein as a shadow or dip) in the DC illumination pattern when the jaws are substantially parallel. The absorption pattern and its shape are believed to be the result of (i) the inherent contrast between the absorption characteristics of the blood (greater) and tissue (lesser) and (ii) the general symmetrical shape of blood vessels (circular cross-section with greatest amount of blood in the center and roughly equal amounts on either side of the center). While this is described as a Gaussian-type absorption pattern, it is believed that the shadow or dip could be described alternatively by other distributions, such as Cauchy, Beta, Gamma, etc. <FIG> illustrate the illumination pattern expected when a vessel is disposed between the jaws of a surgical instrument with emitters <NUM> and sensors <NUM> attached to opposing surfaces of parallel jaws (or non-parallel jaws where the angular distortions are not significant) (<FIG>), and with emitters <NUM> and sensors <NUM> attached to opposing surfaces of non-parallel jaws where the angular distortions are significant (<FIG>). In <FIG>, the Gaussian-type absorption pattern is present having the symmetrical shape that is expected. In <FIG>, the Gaussian-type shadow is distorted and skewed toward one end. This distortion of the absorption profile may alter the blood vessel size estimations, intensity controls, etc., above.

According to an embodiment of the present system and method for compensating for angular distortions, a plurality of light emitters <NUM> are disposed at a working end <NUM> of a surgical instrument <NUM> on a first surface, and a plurality of light sensors <NUM> are disposed at the working end <NUM> of the surgical instrument <NUM> on a second surface opposing the first surface, the first and second surfaces disposed on a pair of non-parallel jaws, resulting in an angle between the opposing surfaces. According to some embodiments, the plurality of light emitters <NUM> and the plurality of light sensors <NUM> may be arranged in to an array of light emitters <NUM> and an array of light sensors <NUM>, respectively. Further, in embodiments of the system and method, the pair of non-parallel jaws may be adjustable to vary an angle between the first and second opposing surfaces on which the plurality of light emitters <NUM> and the plurality of light sensors <NUM> are disposed. The light sensors <NUM> are adapted to generate a signal comprising at least a non-pulsatile component (i.e., the signal may also include a pulsatile component, or the signal may include only a non-pulsatile component).

The system also includes a controller <NUM> coupled to the plurality of light sensors <NUM>, the controller <NUM> determining an illumination pattern from the non-pulsatile component of the signal(s) received from the light sensors <NUM>. In addition, the controller <NUM> determines a first point at a first side of a region of interest and a second point at a second side of the region of interest. The region of interest may be an absorption profile within the illumination pattern, and the first and second points may be to either side the absorption profile (i.e., one to the left of the region of interest and one to the right of the region of interest). The controller <NUM> further determines a linear curve including the first and second points disposed about the region of interest. The controller <NUM> then uses the linear curve to remove the angular distortion from the region of interest between the first and second points. According to certain embodiments, the controller <NUM> may use linear curves to remove the angular distortion from the entire illumination pattern.

To illustrate the specific operation of the system and method according to such an embodiment, an illumination pattern is illustrated in <FIG> with a region of interest between points A and B, the x-axis indicating the distance of a sensor <NUM> of the array from the distalmost point or tip (x=<NUM>) of the working end <NUM> of a surgical instrument <NUM>, and the y-axis indicating the magnitude of the non-pulsatile, or DC, component of the light detected by the sensor <NUM>. The coordinates for point A may be (xA, DCA), where x is the location along the array of sensors <NUM> and DC is the illumination at the particular location along the array of sensors <NUM>. In a similar fashion, the coordinated for point B may be (xB, DCB). As such, one can determine the slope, m, of the line including the first and second points as: <MAT> Furthermore, the offset, c, of the line including points A and B may be determined as: <MAT>.

Once the slope, m, and the offset, c, have been determined, the angular distortion in the non-pulsatile values within the region of interest between points A and B can be removed for all k that are within the set of A to B using: <MAT> That is, DCk represents the amount required to be added to a particular DC magnitude within the region of interest to compensate for the angular distortion. <FIG> illustrate graphically the manner in which the distortion may be removed from an illumination profile, at least within a region of interest, to permit the region of interest to be used in the systems and methods disclosed herein.

<FIG> illustrates a method <NUM> of operating the system described above. According to the method, light emitted from an array of emitters disposed along a first jaw (block <NUM>) is detected by an array of sensors disposed along a second jaw opposite the first jaw (block <NUM>), the first and second jaws disposed at an angle. The method <NUM> continues to block <NUM>, where an illumination pattern according to the light intensities detected by the array of sensors is determined. The method continues at block <NUM>, where a region of interest within the illumination pattern is determined. The region of interest may be, for example, an absorption profile. The method determines a first point to the one side of the region of interest and a second point to the other side of the region of interest at block <NUM> (which block <NUM> may be part of previous block <NUM>). This determination may be made based on changes in the rate at which the illuminations decrease or increase along the illumination pattern. For example, the derivative of the entire illumination pattern may be inspected from left to right, and the first point, A, may be defined as the point where the derivative first goes below a first threshold and the second point, B, may be defined as the point where the derivative goes above a second threshold.

Once the first and second points have been identified to either side of the region of interest, the method <NUM> continues to block <NUM> where the slope of the line through the first and second points is determined. As noted above, this may be determined by dividing the change along the y-axis (i.e., the non-pulsatile component) by the change along the x-axis (i.e., the distance along the sensor array). With the slope known, the offset, if any, or the line may be determined, as explained above at block <NUM>.

With the slope and offset of the line including the first and second points on either side of the region of interest determined, the linear curve may be used to remove the angular distortion from the curve at block <NUM>. For example, as illustrated above, the angular distortion may be removed by determining, for all elements k between the first and second points: <MAT> and then adding DCk to the DC magnitude at the element k. The region of interest, as compensated for the angular distortion, may then be used in any of the foregoing embodiments where the DC profile is consulted.

In regard to the theoretical underpinnings of the system and the method, it has been observed that the non-pulsatile illumination pattern is a polynomial that could be represented using piecewise linear curves, even when the illumination pattern has been subject to angular distortion. Based on this piecewise representation of the illumination pattern, it is believed that if the linear curve connecting end-points of a region of interest is determined, the degree of distortion, or attenuation, can likewise be determined. Once the level of distortion is known, the values within the region of interest can be compensated (for the angular distortion) and the shape of the curve within the region of interest (e.g., the absorption profile) may be recovered.

The system and method of angular distortion compensation has a number of advantages, and one or more of which may be present in a particular embodiment. The system and method do not require direct information regarding the angle between the opposing surfaces to which the emitters <NUM> and sensors <NUM> are attached. Therefore, there is no need to include a device for measuring the angle between the opposing surfaces, reducing the cost and complexity of the system. It is also believed that the system and method will function irrespective of the jaw angle and the blood vessel position along the opposing surfaces. The system and method rely on mathematical concepts that are not computationally expensive, which may reduce the cost of the system. Even more significant, the inexpensiveness of the system and method from a mathematical standpoint makes the angular distortion compensation better suited for a real-time or near-real-time implementation. Embodiments of the system and method also avoid the requirement for resort to look-up tables, and the need for calibration procedures prior to use of the surgical instrument. Further, it is believed that the method and system are useful for a very broad range of intensity values. In addition, because the system and method compensate for angular distortion without the need to modify the intensity of individual emitters <NUM>, this simplifies the system and method both in terms of cost and complexity by avoiding the need to provide control for each of the emitters <NUM>.

On the other hand, according to still further embodiments, a system and method to compensate for angular distortion may be based on controlling individual emitters <NUM>, instead of correcting the illumination profile produced using an array of emitters emitting the same or similar intensity. To permit control of the individual emitters <NUM> to compensate for angular distortion, the non-pulsatile (DC) illumination pattern is modeled, and then the model is used in as part of a feedback loop relative to a detected illumination pattern to control the intensity of the individual emitters <NUM>.

According to such a system and method for compensating for angular distortions, a plurality of light emitters <NUM> are disposed at a working end <NUM> of a surgical instrument <NUM> on a first surface, and a plurality of light sensors <NUM> are disposed at the working end <NUM> of the surgical instrument <NUM> on a second surface opposing the first surface, the first and second surfaces disposed on a pair of non-parallel jaws. The plurality of light emitters <NUM> and the plurality of light sensors <NUM> may be arranged in to an array of light emitters <NUM> and an array of light sensors <NUM>, respectively. According to certain embodiments the pair of non-parallel jaws may be adjustable to vary an angle (θ) between the first and second opposing surfaces on which the plurality of light emitters <NUM> and the plurality of light sensors <NUM> are disposed. The light sensors <NUM> are adapted to generate a signal comprising at least a non-pulsatile component (i.e., the signal may also include a pulsatile component, or the signal may include only a non-pulsatile component).

The system also includes a controller <NUM> coupled to the plurality of light emitters <NUM> and the plurality of light sensors <NUM>. The controller <NUM> models a non-pulsatile illumination pattern according to the intensities (I) of the individual emitters <NUM>. The controller <NUM> compares that model against the non-pulsatile illumination pattern detected using the light sensors <NUM>. The controller <NUM> then varies the intensities of the individual light emitters <NUM> based on the comparison of the pattern as determined according to the model and the pattern as determined according to the light sensors <NUM>. The intensities of the emitters <NUM> are varied until the feedback indicates that the angular distortion has been removed.

According to this method and system, the non-pulsatile illumination pattern detected across the sensor array may be modeled as: <MAT>.

Further, it is believed that the magnitude of the angular distortion (δk ) induced is a direct function of the jaw angle (θ) and the emitter intensity (I). This may be stated as: <MAT> For a particular jaw angle and a particular intensity emitted by an emitter <NUM>, the model will profile the magnitude of the angular distortion: <MAT> This distribution of the distortion will then be used as a feedback to update the intensity of the emitters <NUM>. In fact, it is believed that the emitter intensity required will be directly proportional to the magnitude of the distortion, as stated above. Accordingly, the emitter intensity update equation may be: <MAT>.

It will be recognized from the emitter intensity update equation that a larger distortion will require a larger change in individual emitter intensity, and vice-versa.

<FIG> illustrates a method <NUM> of operating the system described above. According to the method, light emitted from an array of emitters disposed along a first jaw (block <NUM>) is detected by an array of sensors disposed along a second jaw opposite the first jaw (block <NUM>), the first and second jaws disposed at an angle. The method <NUM> continues to block <NUM>, where an illumination pattern according to the light intensities detected by the array of sensors is determined. The method <NUM> continues at block <NUM>, wherein the illumination pattern is modeled according to the above-mentioned model. It will be recognized that, optionally, the activity of block <NUM> may precede block <NUM>. At block <NUM>, the illumination pattern detected by the array of sensors <NUM> is compared with the illumination pattern as modeled. At block <NUM>, the intensities of the individual light emitters <NUM> are modified according to the comparison at block <NUM>.

Having thus described the surgical system <NUM>, the method <NUM> and the principles of the system <NUM> and the method <NUM> in general terms, further details of the system <NUM> and its operation are provided.

Initially, while the emitter <NUM> and the sensor <NUM> are described as disposed at the working end <NUM> of the surgical instrument <NUM>, it will be recognized that not all of the components that define the emitter <NUM> and the sensor <NUM> need be disposed at the working end of the instrument <NUM>. That is, the emitter <NUM> may comprise a light emitting diode, and that component may be disposed at the working end <NUM>. Alternatively, the emitter <NUM> may include a length of optical fiber and a light source, the source disposed remotely from the working end <NUM> and the fiber having a first end optically coupled to the source and a second end disposed at the working end <NUM> facing the sensor <NUM>. According to the present disclosure, such an emitter <NUM> would still be described as disposed at the working end <NUM> because the light is emitted into the tissue at the working end <NUM> of the instrument <NUM>. A similar arrangement may be described for the sensor <NUM> wherein an optical fiber has a first end disposed facing the emitter <NUM> (or perhaps more particularly, an end of the optical fiber that in part defines the emitter <NUM>) and a second end optically coupled to other components that collectively define the sensor <NUM>.

As also mentioned above, the light emitter <NUM> and light sensor <NUM> are positioned opposite each other. This does not require the emitter <NUM> and the sensor <NUM> to be directly facing each other, although this is preferred. According to certain embodiments, the emitter <NUM> and sensor <NUM> may be formed integrally (i.e., as one piece) with jaws <NUM> of a surgical instrument <NUM>. See <FIG> and <FIG>. In this manner, light emitted by the emitter <NUM> between the jaws <NUM> and through the tissue of interest may be captured by the light sensor <NUM>.

The light emitter <NUM> may include one or more elements. According to an embodiment schematically illustrated in <FIG>, the light sensor <NUM> may include a first light emitter <NUM>-<NUM>, a second light emitter <NUM>-<NUM>, and a third light emitter <NUM>-<NUM>. All of the light emitters may be adapted to emit light at a particular wavelength (e.g., <NUM>), or certain emitters may emit light at different wavelengths than other emitters.

As to those embodiments wherein the light emitter <NUM> is in the form of an array including one or more light emitting diodes, as is illustrated in <FIG> for example, the diodes may be arranged in the form of a one-dimensional, two-dimensional or three-dimensional array. An example of a one-dimensional array may include disposing the diodes along a line in a single plane, while an example of a two-dimensional array may include disposing the diodes in a plurality of rows and columns in a single plane. Further example of a two-dimensional array may include disposing the diodes along a line on or in a curved surface. A three-dimensional array may include diodes disposed in more than one plane, such as in a plurality of rows and columns on or in a curved surface.

The light sensor <NUM> according to the embodiments of the present disclosure also includes one or more individual elements. According to an embodiment illustrated in <FIG>, the light sensor <NUM> may include a first light sensor <NUM>-<NUM>, a second light sensor <NUM>-<NUM>, an n-th light sensor <NUM>-n, and so on. As was the case with the light emitters <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, the light sensors <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> may be arranged in an array, and the discussion in regard to the arrays above applied with equal force here.

As discussed above, the system <NUM> may include hardware and software in addition to the emitter <NUM>, sensor <NUM>, and controller <NUM>. For example, where more than one emitter <NUM> is used, a drive controller may be provided to control the switching of the individual emitter elements. In a similar fashion, a multiplexer may be provided where more than one sensor <NUM> is included, which multiplexer may be coupled to the sensors <NUM> and to an amplifier. Further, the controller <NUM> may include filters and analog-to-digital conversion as may be required.

As for the indicator <NUM> used in conjunction with controller <NUM>, a variety of output devices may be used. As illustrated in <FIG>, a light emitting diode <NUM>-<NUM> may be attached to or incorporated into the associated surgical instrument <NUM>, and may even be disposed at the working end <NUM> of the instrument <NUM>. Alternatively or in addition, an alert may be displayed on a video monitor <NUM>-<NUM> being used for the surgery, or may cause an image on the monitor to change color or to flash, change size or otherwise change appearance. For example, <FIG> illustrates a portion of a graphical user interface (GUI) that may be displayed on the video monitor <NUM>-<NUM>, wherein a first region <NUM> is representative of the location of a section of a vessel and surrounding tissue between the jaws of the surgical instrument <NUM> and a second region <NUM> is an enhanced representation of the section of vessel and surrounding tissue illustrated in first region <NUM> with the vessel represented in a contrasting fashion to the surrounding tissue (e.g., through the use of bands of different color for the vessel and the surrounding tissue). The indicator <NUM> may also be in the form of or include a speaker <NUM>-<NUM> that provides an auditory alarm. The indicator <NUM> also may be in the form of or may incorporate a safety lockout <NUM>-<NUM> associated with the surgical instrument <NUM> that interrupts use of the instrument <NUM>. For example, the lockout could prevent ligation or cauterization where the surgical instrument <NUM> is a thermal ligature device. As a still further example, the indicator <NUM> also may be in the form of a haptic feedback system, such as a vibrator <NUM>-<NUM>, which may be attached to or formed integral with a handle or handpiece of the surgical instrument <NUM> to provide a tactile indication or alarm. Various combinations of these particular forms of the indicator <NUM> may also be used.

As mentioned above, the surgical system <NUM> may also include the surgical instrument <NUM> with the working end <NUM>, to which the light emitter <NUM> and light sensor <NUM> are attached (in the alternative, removably/reversibly or permanently/irreversibly). The light emitter <NUM> and the light sensor <NUM> may instead be formed integrally (i.e., as one piece) with the surgical instrument <NUM>. It is further possible that the light emitter and light sensor be attached to a separate instrument or tool that is used in conjunction with the surgical instrument or tool <NUM>.

As noted above, the surgical instrument <NUM> may be a thermal ligature device in one embodiment. In another embodiment, the surgical instrument <NUM> may simply be a grasper or grasping forceps having opposing jaws. According to still further embodiments, the surgical instrument may be other surgical instruments such as dissectors, surgical staplers, clip appliers, and robotic surgical systems, for example. According to still other embodiments, the surgical instrument may have no other function than to carry the light emitters/light sensors and to place them within a surgical field. The illustration of a single embodiment is not intended to preclude the use of the system <NUM> with other surgical instruments or tools <NUM>.

Experiments have been conducted using an embodiment of the above-described system. The experiments and results are reported below.

The first set of experiments was conducted using an excised porcine carotid artery. To simulate the pulsatile flow of fluid found in such blood vessels, a submersible DC pump was used. The pump was capable of operation at between <NUM> and <NUM> cycles per minute, and could provide a flow rate that could be set to a particular value. The fluid used was bovine whole blood to which heparin had been added and that was maintained at an elevated temperature to maintain physiological viscosity. For the experiments described below, the blood was pumped at <NUM> cycles per minute and at a flow rate of <NUM> per minute.

A light emitter array was disposed opposite a light sensor array with the excised porcine carotid artery disposed therebetween. The light emitter array included five light emitting diodes that emitted light at <NUM>. The light sensor array included a linear CCD array composed of <NUM> elements arranged side-by-side, with each group or set of <NUM> elements fitting into <NUM> of contiguous space along the array. The system was operated for <NUM> seconds, with the results of the experiments plotted in <FIG>. The inner diameter of the vessel was determined by using the distance between a pair of positions where the magnitude of the pulsatile component was <NUM>% of the peak magnitude (i.e., line C in <FIG>).

The second set of experiments was conducted using a light emitter array opposite a light sensor array, with the porcine carotid artery of a living porcine subject disposed therebetween. The light sensor array included five light emitting diodes that emitted light at <NUM>. The light sensor array included <NUM> individual photodetector elements, each element being <NUM> wide. The elements were spaced with <NUM> between adjacent elements, such that each element occupied <NUM> of contiguous space along the array. The system was operated for <NUM> seconds, with the results of the experiment plotted in <FIG>. The measurements for each photodetector were interpolated and converted to pixels to permit a comparison between the first set of experiments and the second set of experiments. Again, the inner diameter of the vessel was determined by using the distance between a pair of positions where the magnitude of the pulsatile component was <NUM>% of the peak magnitude (i.e., line C in <FIG>).

In both sets of experiments, the inner diameters of the porcine arteries determined using embodiments of the disclosed system were within a millimeter of the gross diameter measurements of the vessel. For example, relative to the first set of experiments, the inner diameter determined using the embodiment of the system was <NUM>, while the gross diameter measurement was <NUM>. As to the second set of experiments, the inner diameter determined using the embodiment of the system was <NUM>, and the gross diameter measurement was <NUM>.

For a third set of experiments, an embodiment of the system including an LED array emitting at <NUM> and a linear CCD array was used. The system was used to determine the resting outer diameters of four different arteries (gastric, left renal, right renal, and abdominal) in a living porcine subject. The system was operated for <NUM> seconds, and the inner diameters were determined using a pair of points associated with <NUM>% of the peak magnitude. After using the system to determine the inner diameters, the arteries were excised and the gross vessel diameters were obtained by quantifying the cross-section of the vessels at the point of measurement along the vessels using NIH ImageJ software.

The results of the third group of experiments are illustrated in <FIG>. As indicated in the graph, there is a close correlation between the inner diameters determined using an embodiment of the system disclosed herein and the inner diameters measured using conventional techniques. The error bars represent the standard deviation of measurements of the same artery taken at different points in time.

Claim 1:
An optical surgical system (<NUM>) with compensation for angular distortions, the system comprising
a plurality of light emitters (<NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>) disposed at a working enc (<NUM>) of a surgical instrument (<NUM>) on a first surface a plurality of light sensors (<NUM>-<NUM>, <NUM>-<NUM>, ... <NUM>-n) disposed at the working end of the surgical instrument on a second surface opposing the first surface, the first and second surfaces disposed on a pair of non-parallel jaws (<NUM>) with an angle (θ) between the first and second opposing surfaces; and
a controller (<NUM>) coupled to the plurality of light emitters and the plurality of light sensors, the controller configured to
model a non-pulsatile illumination pattern according to the intensities of individual emitters of the plurality of light emitters,
compare the non-pulsatile illumination pattern according to the model against a non-pulsatile illumination pattern detected using the plurality of light sensors, and
vary the intensities of the individual emitters of the plurality of light emitters based on the comparison of the non-pulsatile illumination pattern according to the model and the non-pulsatile illumination pattern detected using the plurality of light sensors until angular distortion has been removed.