RU2804228C1 - Method for minimizing motion artifacts when examining tissue using optical coherence angiography and device for its implementation - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: device for obtaining intravital images of the microvascular bed in the near-surface layers of biological tissues, made in form of an ellipse-shaped platform with a pipe, the inner diameter of which corresponds to the outer diameter of the cylindrical sensor of an OCT (optical coherence tomography) device, with the ability to connect to a separately located aspirator via a vacuum tube. A method for minimizing motion artifacts when studying tissues using optical coherence angiography, in which, when performing optical coherence angiography (OCA), a device is installed on the cylindrical sensor of the OCT device to obtain intravital images of the microvascular bed in the near-surface layers of biological tissues, and a vacuum tube of the aspirator is attached; the pressure level when examining integumentary tissues is set at -125 mmHg, and for examining the abdominal organs at a value equal to the mean arterial pressure in mmHg at the time of the study minus 60 mmHg.

EFFECT: improvement of quality of the data obtained during OCA by reducing the number of artifacts on OCA images; the possibility of continuous movement of the sensor over the surface of the tissue without disrupting microcirculation.

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Description

The group of inventions relates to medicine, namely to the field of diagnostics in clinical and experimental surgery, and can be used to obtain intravital images of the microvascular bed in the surface layers of biological tissues.

Topical diagnosis of the state of blood circulation in tissues is one of the universal and complex tasks of surgery. In particular, intraoperative verification of the presence of blood flow in the intramural vessels of the intestine is necessary to objectively determine the boundaries of viable and non-viable intestine, and, accordingly, to determine the boundaries of its resection. Verification of the state of skin microvessels is necessary to determine the viability of thermally damaged or transplanted areas. Changes in the microcirculation of the oral mucosa must be monitored during radiation therapy for head and neck tumors to prevent the development of severe stages of mucositis. Microcirculation indicators can also be effective predictors for the diagnosis of precancerous conditions of the oral cavity. Optical coherence angiography (OCA), based on signal analysis in the optical coherence tomography (OCT) method, has the necessary technical potential for objective diagnosis of intramural microvessels in these tissues to a depth of 2 mm, sufficient to obtain clinically relevant information. In addition, the use of OKA in experimental studies of acute ischemic, traumatic, and radiation tissue damage can significantly deepen the understanding of the pathogenesis of these common pathological conditions. The main reason for the limitations in the use of OCA for diagnosing the microvasculature in tissues in vivo is the high sensitivity of the technique for extracting information about blood vessels to the presence of movements of the tissues under study during scanning. An important condition for increasing the effectiveness of the clinical and experimental use of OKA is the ability to reproduce a continuous picture of the network of blood vessels during translational displacement of the sensor: such a possibility would allow for a diagnostic search for tissue areas with impaired blood circulation if the sensor was not initially installed in the lesion. However, currently, the movement of the sensor involves step-by-step movement, rather than sliding of the sensor surface over the tissue, which leads to discrete OKA patterns and, ultimately, to a significant decrease in the quality of diagnostic data.

From the work of [P.D. Agrba, E.A Bakshaeva, D.O. Ellinsky, I.L. Shlivko, M.Yu. Kirillin. The role of mechanical compression in visualization of human skin using cross-polarization optical coherence tomography. STM. 2014. 6(1): 75-82] there is a known method of mutual fixation of the probe and the tissue under study, which consists in ensuring controlled pressing of the OCT probe to the surface of the tissue (thin human skin). The pressing force is controlled using a dynamometer coupled to a probe.

The probe description states: “The CP OCT probe, coupled with a dynamometer that measures the force of pressing the probe against the sample, was positioned perpendicular to the surface of the sample and pressed against it with a force of 0.35 ± 0.04 MPa. The compression force was chosen in such a way as to ensure complete contact of the probe with the surface of the skin and cause minor discomfort. Such compression is a non-invasive effect, all changes are reversible, and their consequences disappear within 20 minutes after the end of the experiment. A further increase in pressure can lead to the appearance of a hematoma, which can already be classified as an invasive effect. During the measurement process, the pressing force of the CP OCT probe to the surface of the biological tissue was kept at a constant level throughout the entire observation period.”

The method can only be carried out on open horizontal surfaces where there is enough space to install a dynamometer; This method does not work on inclined and vertical surfaces. Allows you to obtain only discrete OKA images, which can lead to the loss of some important diagnostic data due to the inability to move the sensor without detachment.

From US patent No. 4736749 (MPK A61B 5/00, 5/04, A61B 7/04, published on April 12, 1988), a device for vacuum fixation on the human body is known, containing a separately located vacuum pump, which is connected to a hollow body with a centrally located chamber and an annular cavity, which is limited from below by the surface of the sealing device, which is pressed to the body by means of a detachable connector to form one chamber with the possibility of covering it from below with the surface of the human body.

The disadvantages of this device and the method of its use are:

1. The size of the device significantly exceeds the size of the sensor, therefore tissue fixation occurs only in the area of the annular cavity located around and at a distance from the area of study by the sensor, therefore the surface of the tissue under study in the contact zone remains mobile relative to the sensor, as a result of local micro-movements of the tissue, motion artifacts appear, reducing the quality of OKA images.

2. The impossibility of moving the device along the surface of the tissue while maintaining constant contact between the surface of the sensor and the tissue without the risk of depressurization of the vacuum cavity and mutual displacement of the sensor and tissue.

The objective of the proposed group of inventions is to increase the accuracy of OKA diagnostics by minimizing artifacts that appear on OKA images due to involuntary displacements of the tissue under study relative to the device sensor or due to arbitrary movement of the device sensor along the tissue surface during a diagnostic search.

The technical result is to improve the quality of the data obtained during OKA by reducing the number of artifacts on OKA images; the possibility of continuous movement of the sensor over the surface of the tissue without disrupting microcirculation.

The technical result is achieved by a device containing a separately located aspirator, which is connected to the device by means of a vacuum tube, the device is made in the form of an ellipsoidal platform with a pipe, the internal diameter of which corresponds to the outer diameter of the cylindrical sensor of the OCT device, the height of the pipe is greater than the height of the sensor of the OCT device, no more than 4 mm, the transition from the platform to the nozzle from the inside is smoothed, in the distal part of the device in the area not covered by the sensor of the OCT device, there is an outlet for connecting the vacuum tube of the aspirator to the nozzle.

The technical result is also achieved by the fact that when performing OKA, the proposed device is installed on the OKA sensor, and a vacuum tube of the aspirator is attached to create a vacuum; set the pressure level when examining integumentary tissues at a level of at least -125 mmHg, and for examining the abdominal organs - to a value not less than the mean arterial pressure in mmHg, at the time of the study minus 60 mmHg .st.

Preferably, to study an adjacent area of tissue, the OCT device sensor is shifted along with the device without tearing it off by “sliding” along the tissue being studied along the conventional major axis of the device area.

The group of inventions is illustrated by figures, where in FIG. 1 - photo of the device on the cylindrical sensor of the OKA device with a vacuum tube connected to the outlet; in fig. 2 - photo of using the device when conducting a study using the proposed method on the neck of a volunteer, in FIG. 3 (a, b) - examples of conducting an OKA study without using the proposed device and method; in fig. 4 - stage of obtaining an OKA image on an area fixed using the developed device and method (photo); in fig. 5 (a, b) - OKA images obtained using the developed device and method of fixing the device sensor; in fig. 6 - histological structure of the intestinal wall after obtaining the OKA image using the developed method (a) and the intact small intestine, not subjected to diagnostic or any other manipulations (b); in fig. 7 - a series of OKA images obtained using the developed device and method during long-term monitoring of a section of the intestine with controlled displacement of the area of interest without removing the device, where (a) - OKA image at the starting point of the study, (b) - OKA image, displaced 1.8 mm down from the starting point; (c) - OKA image shifted 1.8 mm downward 10 minutes from the start of the study; (d) - OKA image fixed at the previous research point for 20 minutes; in fig. 8 - study of the skin area of the dorsal surface of the hand using manual clamping of the OCT sensor (a), OKA images obtained using manual clamping of the OCA sensor (b, c), study of the skin of the dorsal surface of the hand using the developed device (d) , OKA images obtained using the proposed method (e, f); in fig. 9 - study of the skin area of the lateral surface of the neck using the developed device (a), the obtained OCA image (b), the condition of the skin at the study site after completion of the study (c); in fig. 10 - study of an area of the oral mucosa using a manual clamp of the OCT sensor (a), obtained using a manual clamp of an OCT sensor OKA images (b, c), study of a site of the oral mucosa using the developed device (d) and OKA images obtained using the developed device (e, f).

The device for minimizing motion artifacts when studying tissue using optical coherence angiography (Fig. 1, Fig. 2) is made in the form of an ellipsoid-shaped platform (1) with a pipe (2), the inner diameter of which corresponds to the outer diameter of the cylindrical sensor of the OCT device (3 ), the small diameter of the platform is close to the outer diameter of the pipe. The height of the nozzle is no more than 4 mm greater than the height of the OCT device sensor. The transition from the platform to the pipe from the inside is smoothed. In the distal part of the device, in the area not covered by the sensor of the OCT device, there is an outlet (4) for connecting the vacuum tube of the aspirator to the branch pipe.

The method is carried out as follows.

An area of skin tissue, mucous membrane, segment of intestine, etc. is selected for examination. The proposed device is placed on the sensor of the OCT device in such a way that between the end of the sensor and the distal edge of the pipe there remains from 1 to 4 mm, the outlet is not blocked by the sensor of the device. The distal end of the aspirator tube is hermetically connected to the outlet. The proximal end of the tube is hermetically connected to the operating aspirator. The level of negative pressure created by the aspirator when examining integumentary tissues is set at a level of at least -125 mm Hg, and for examining the abdominal organs - to a value not less than the mean arterial pressure in mm Hg at the time of the study. minus 60 mm Hg. The operating aspirator is turned on and contact of the device platform with the tissue surface is created until the effect of “suction” of the tissue section to the sensor surface is obtained. Conducting research. After completing the study and recording OKA images, the pressure inside the device is compensated by turning off the aspirator.

If it is necessary to study a neighboring area of tissue, the sensor of the OCT device is shifted along with the device, maintaining contact between the device and the tissue. The movement is carried out by “sliding” along the conventional major axis of the device platform. The ellipsoidal shape of the platform forms rounded “protrusions”, which ensure minimal deformation of the tissue located outside the device when moving (“sliding”), and the smooth connection of the nozzle and the platform from the inside ensures a reduction in the level of tissue trauma.

We give examples of the use of a group of inventions.

Example 1.

The device and method were used to perform an OKA study of blood circulation in the intestinal wall of the minipig “Wiesenau” in an experiment, since the intestinal parameters of this category of laboratory animals are closest to the parameters of the human intestine. Extract from experiment No. 3. Under intubation anesthesia, a median laparotomy was performed, then, retreating 40 cm from the duodenojejunal junction, a section of the small intestine was brought into the wound. Acute ischemia of an intestinal segment was modeled by ligation of the jejunal artery. An OKA study was carried out without using the proposed device and method (Fig. 3a, Fig. 3b), adjusting the required contact manually. Then a study was carried out using the proposed method and device. The proposed device was installed on the sensor of the OCT device. There was 4 mm between the end of the sensor and the distal edge of the pipe; the outlet, made at the level of 3 mm, was not blocked by the device sensor. The distal end of the aspirator tube was hermetically connected to the outlet. The proximal end of the tube was hermetically connected to the operating aspirator. The mean arterial pressure at the time of the OCT study was 90 mmHg. Safe level of negative pressure in the lumen of the device, since the study was carried out on the abdominal organ SAD-60=90-60=30. The level of negative pressure created by the aspirator during the study was set to -30 mmHg. The Elema-N OX-8/40 (AM4M10) operating aspirator was turned on and contact of the device platform with the tissue surface was created until the effect of “suction” of the tissue section to the sensor surface was obtained (Fig. 4). For 26 seconds required to obtain OKA images, the area under study remained motionless relative to the sensor of the OKA device, as a result of which the quality of OKA images increased significantly in comparison with the traditional (manual) method of fixation: motion artifacts - bright horizontal stripes of different thicknesses - disappeared and the wavy nature of the pattern (Fig. 5a, Fig. 5b). No visual changes were found at the site of the study; complete anatomical preservation of the examined area was confirmed histologically (Fig. 6a) and corresponds to normal (Fig. 6b).

Example 2.

Extract from experiment No. 4. Using the proposed method and device, OKA monitoring of a section of the intestine was carried out for 30 minutes. Mean arterial pressure (MAP) at the time of the study was 120 mm Hg. The level of safe negative pressure created by the aspirator during the study was established at -60 mmHg. (SAD-60=120-60=60). An OCA image was obtained at the starting point of the study (Fig. 7a). Then, maintaining contact between the device and the intestinal tissue, moving along the conditional major axis of the device platform 1.8 mm down from the starting point, the following OKA image was obtained (Fig. 7b). Then, maintaining contact between the device and the intestinal tissue, moving the device platform 1.8 mm down along the conventional major axis of the device, the following image was obtained 10 minutes from the start of the study (Fig. 7c). Within 20 minutes the study was carried out at the end point (Fig. 7d). In all cases, artifact-free OKA images were obtained. The movements of the researcher's hands holding the device's sensor and the physiological movements of the tissues under study did not lead to tissue displacement relative to the working surface of the sensor and did not affect the quality of OCA images.

Example 3. An OKA study of blood circulation in a healthy volunteer was performed on the back of the hand without (Fig. 8 a-c) and using the proposed device and method (Fig. 8 d-f). When using the proposed method, the negative pressure level is set to 125 mmHg. During the 26 seconds required to obtain OKA images, the area under study remained motionless relative to the device’s sensor, as a result of which the quality of OKA images significantly increased in comparison with the traditional (manual) method of fixing the sensor.

Example 4.

An OKA study of blood circulation was performed using the proposed group of inventions in a healthy volunteer on the lateral surface of the neck (Fig. 9a). The study was carried out in a sitting position. When using the proposed method, the negative pressure level is set to 125 mm Hg. During the 26 seconds required to obtain OKA images, the area under study remained motionless relative to the device sensor; as a result, OKA images were obtained without artifacts (Fig. 9b). After completing the study and recording OKA images, the pressure inside the device was compensated by turning off the aspirator. No visualized pathological changes (hemorrhages, edema, ischemia, etc.) were found at the site of the study (Fig. 9c).

Example 5.

An OKA study of blood circulation in a healthy volunteer was performed in the oral mucosa without (Fig. 10 a-c) and using the proposed device and method (Fig. 10 d-f). When using the proposed method, the level of negative pressure is set to 120 mmHg. The outlet in the device used is made at a level of 2 mm. During the 26 seconds required to obtain OKA images, the area under study remained motionless relative to the device’s sensor, as a result of which the quality of OKA images significantly increased in comparison with the traditional (manual) method of fixing the sensor.

Thus, the developed method and device improve the quality of the data obtained during OKA by reducing the number of artifacts on OKA images and provide the ability to continuously move the sensor along the tissue surface while maintaining the quality of the information obtained. By creating a fixed pressure difference between the internal volume of the attached device and the external environment, mutual fixation of the probe of the OKA device and the tissue under study occurs, which allows for controlled and constant pressure over time of the surface of the tissue under study to the end of the probe. The use of the proposed device and method made it possible to completely neutralize tissue movements relative to the sensor (respiratory, pulse, muscle contractions) and sensor movements relative to tissues (movements of the researcher’s hands holding the device’s sensor) for the duration of the study. Due to the pressure deficit inside the device created by the aspirator, the tissues under study were fixed in a controllable force and time manner to the working surface of the OCT sensor; after obtaining the OKA image, the pressure deficit was compensated, the device was disconnected from the tissues under study without macro- and microscopic signs of damage to the latter.

Claims (3)

1. A device for obtaining intravital images of the microvascular bed in the near-surface layers of biological tissues, designed to be connected to a separately located aspirator via a vacuum tube, characterized in that the device is made in the form of an ellipsoidal platform with a pipe, the inner diameter of which corresponds to the outer diameter of the cylindrical sensor of the device OCT (optical coherence tomography), the height of the nozzle is no more than 4 mm greater than the height of the OCT device sensor, the transition from the platform to the nozzle from the inside is smoothed, in the distal part of the device in the area not covered by the OCT device sensor, there is an outlet for connection aspirator vacuum tube to the nozzle. 2. A method for minimizing motion artifacts when studying tissue using optical coherence angiography, characterized in that when performing optical coherence angiography (OCA), a device according to claim 1 is installed on the cylindrical sensor of the OCT device, a vacuum tube of the aspirator is attached; set the pressure level when examining integumentary tissues at a level of -125 mm Hg. or more, and for the study of abdominal organs - to a value equal to the mean arterial pressure in mmHg, at the time of the study minus 60 mmHg. 3. The method according to claim 2, characterized in that in order to study an adjacent area of tissue, the sensor of the OCT device with the installed device according to claim 1 is shifted, without tearing it off, by “sliding” along the tissue under study along the conditional major axis of the device area.