DE102016001658A1 - Method for detecting organ perfusion - Google Patents

Abstract

The invention relates to a method for detecting the organ perfusion on the basis of sonographic methods according to the Doppler principle using a system for position detection, which is equipped with an aligned on the blood vessel to be examined transducer. The object of the invention is to provide a related technical solution with which an angle between the blood vessel to be examined and the respective associated ultrasound head can be measured. It should be achieved that not only individual vessels are selectively subjected to a study, but that all the vessels of a tissue can be examined simultaneously. In this way one can determine the actual mean flow velocity and, in combination with the determined cross-sectional area in each individual vessel, the exact flow volumes after angle correction. This object is achieved by arranging the system for detecting the position on the skin surface of the person to be examined successively at at least two different positions, wherein the parameters detected in these two positions of the transducer and the position detection system are fed to a computational evaluation by the volume flow (V). is calculated on the basis of the parameters cross-sectional area, velocity and the determined sound angle by means of vector determination along the vessel axis.

Description

The invention relates to a method for detecting organ perfusion based on sonographic methods according to the Doppler principle using a system for position detection (eg camera marker systems, electromagnetic position detection) which is equipped with a transducer aligned with the blood vessel to be examined.

The perfusion referred to as perfusion of organs of the human body causes a supply of body tissue with oxygen and other blood components and disposal of metabolic products and the like. Functional deficiencies of organ perfusion, colloquially referred to as a circulatory disorder, can cause acute or chronic impairment of various organ or tissue functions. Therefore, it is necessary for various medical tasks to detect the organ perfusion of the human body.

A typical application in this respect is, for example, the examination during pregnancy. For the normal functioning of all organs and for the normal development of organ function in the course of pregnancy, an adequate blood supply is an indispensable prerequisite. Disruptions of the necessary blood supply of organs lead, especially during embryonic and fetal development, to growth inhibition and disruption of organ structure and / or organ function. Both deviations from the norm lead to complications shortly before, during or immediately after birth in the majority of patients with such a disorder. Furthermore, many pathophysiological processes (changes in bodily functions) are accompanied by a change in organ and tissue perfusion. For example, inflammatory diseases are regularly associated with an increase in tissue perfusion, whereas many chronic diseases are associated with decreased tissue perfusion and the onset of smaller blood vessels within an organ.

Therefore, both for an assessment of the embryonic and fetal prenatal development of a child as well as for a later evaluation of numerous diseases, it is desired that the organ perfusion can be measured.

For this purpose, various methods are already available in medicine, which, however, each have specific disadvantages.

For example, magnetic resonance tomography and computer tomography are very expensive and expensive, so that these methods are used predominantly only for specific questions. In addition, computed tomography and other radiological procedures, such as angiographic imaging of vessels, are associated with radiation exposure to the patient and require injection of a contrast agent. This can be z. B. lead to functional impairment of the kidney to a further deterioration of renal function, so that this method is not applicable in particular in many elderly patients. Furthermore, these methods are inherently invasive and require in addition to the injection of a contrast agent, the puncture of a vein or artery and sometimes also a catheterization of certain vascular areas.

Further possibilities for the detection of the organ perfusion offer scintigraphic procedures, ie imaging techniques using gamma rays. The main disadvantage here is the poor spatial resolution and the thus missing possibility of assigning the perfusion signals to certain tissue formations.

An alternative are methods using sonography. These have the significant advantage over the above-mentioned methods that the application is completely harmless to patients. It can be displayed non-invasively using the cost-effective and widely available method of color Doppler technique, the circulation. Furthermore, no injection of contrast agents is required, further increasing the applicability of this method. The sonographic methods, in particular the color duplex sonography, therefore also allow in the outpatient sector an arbitrarily often repeatable representation of the blood flow in the organs and tissues that can be reached by the ultrasound.

Therefore, in prenatal diagnosis, color Doppler sonography is used to assess blood flow phenomena in the umbilical cord and in the unborn child itself and also in a blood circulation assessment of various postpartum disorders. However, a disadvantage of the hitherto known color duplex sonographic methods is that no actual quantification of blood flow volumes can be undertaken hereby. Rather, the so-called blood flow measurements are the punctual derivation of flow velocity spectra over several cardiac actions. In this case, only two measured values, namely the systolic (blood outflow phase of the heart) and the diastolic (blood inflow phase of the heart) speed value are predominantly determined and set in relation to one another in order to obtain a so-called. To calculate - "(V _min V _max) / V _max RI =" where "RI" vascular resistance index, "V _max" systolic maximum flow velocity and "V _min" end-diastolic minimum flow rate during a cardiac cycle describe vascular resistance index based on the following formula ,

However, such a vascular resistance calculation merely describes the change in blood flow velocity during a heart action. In this case, it is dispensed with, especially for smaller vessels, to measure the angle between the blood vessel and the ultrasound head. An exact - but not taking place here - sound angle determination is according to the Doppler principle the indispensable prerequisite for the correction of the measured velocities in order to be able to calculate the actual flow velocity after their division by the cosine of the vessel angle. The previous methods for measuring organ perfusion therefore do not provide accurate flow velocity measurement.

The prior art also describes other less common methods. A method is realized by an ultrasound image in 3D by a matrix or linear sound head. The determination of the organ perfusion is made by cutting in the horizontal plane in conjunction with the determination of the area by counting the pixels and thus determining the perfusion. Starting from an ideally round vessel, an oblique cross-section results in an ellipse. The parameters are calculated according to the following formulas:
Area ellipse: A = π · a · b → a _real = b _measured / cosα → b _length = a _real · cosα volume flow / flow: V. = v _blood · A
Blood flow velocity: V = v _{measuring blood} / cos

It follows: V. = (v _measurement · π · a _real · a _real · cosα) / cosα V. = v _measurement · π · a _real ² = v _measurement · A _measurement

This procedure is made possible by software (eg a software known under the name "PixelFlux" by Chameleon), whereby corresponding calculations by Prof. Scholbach are known, see for example "Ultrasound in Medicine / Impact Factor 3.260 / E122 to E127 ". A disadvantage of this method, however, is that it takes place on the basis of inhomogeneous, because temporally offset to the heart action, recorded ultrasound of the 3D cube.

At the US 2007/007 3153 A1 . US 2002/004 2574 A1 and US 6,261,233 B1 known technical solutions either specially made transducers are used or two transducers must be placed on the skin of the patient simultaneously.

In a method according to US 8,622,913 B2 the vessel profile and thus its sound angle from a high rate of images in the color Doppler and alternately in the B image is determined continuously. This is done with the aid of several scarf levels relatively independent of the actual position of the transducer. The main difference lies in the transducer used and in the acquisition of the "Scan Planes" mentioned in the document for vascular tracking. The disadvantage of the method is that a 3D transducer is absolutely necessary, whereby either electronic sound steering in a matrix array or a motor-controlled swivel is carried out continuously. The position and area of the vessel are determined in real time. The reference image is constantly angle corrected from the surrounding scan planes, with the transducer remaining at a position on the skin surface for calculation.

Furthermore, "hands-free method with position sensor" are known, however, as in the method by means of the aforementioned software "PixelFlux" (horizontal section), the Doppler signals in the evaluable reconstruction are inhomogeneous, since the images of the vessel cross-sections are performed independently of the heart action. This inevitably leads to false values in pulsatile vessels.

The object of the invention is to provide a technical solution for angle-corrected exact measurement of perfusion in vessels and organs. In this case, the angle between the blood vessel and the ultrasound device is to be measured by means of a position detection system. It is to be achieved that not only individual vessels are punctually examined, but that all the vessels of a tissue can be examined simultaneously to determine the actual mean flow velocity in each individual vessel after an angle correction. In addition, the cross-sectional area of all vessels in a tissue is to be determined and set in relation to the total tissue cross-section.

This object is achieved with the technical features specified in the claim, which will be explained in more detail in an embodiment.

With the solution according to the invention, any 2D color Doppler transducer available on the market can be used. Only an adaptation of the positioning system on the ultrasound head must be adjusted. It is sufficient single transducer, which is moved parallel to the skin surface. Thus, with the usual handling both reference positions, which are necessary for the calculation of the vessel angle, approached with the transducer.

When using the method according to the invention, a single manual swivel is performed, followed by evaluation based on at least two positions taken therefrom on the skin of the patient. The resulting sequence is therefore subsequently evaluated, ie not in real time.

An exemplary embodiment is explained below with reference to the drawing:

1 shows the basic procedure according to the invention in a stylized representation. Accordingly, a calculation in a two-dimensional frontal plane is provided, wherein with a system for position detection A / B (eg camera marker system), which is equipped with a vessel-facing transducer on the skin surface of the person to be examined in a short pivot along the visible in the ultrasound image vessel axis (s) is performed and thus at least two different positions (Pos 1 and Pos 2) each record the vessel cross-section D are triggered, the detected by the transducer - thus in the ultrasound image - and the position detection system Parameters are fed to a computational evaluation.

The above inhomogeneity of previous solutions is eliminated, since only one initial sequence of the cross-sectioned vessel D with all cardiac actions C is necessary - the transducer is not moved to - followed by at least one further recording at a second position (single shot or frame from sequence) , which is needed for determining the position of the respective vessel in the room. On the basis of the vector determination in space, the data relevant for a statement on organ perfusion are determined.

For this purpose, the volume flow (V) in the initial sequence is calculated on the basis of the parameters cross-sectional area, average velocity and the determined sound angle α by vector determination along the vessel axis using at least two positions at a defined distance in one or more vessels according to the following formula: V. = V _measurement · A _measurement · tanα

This ensures that the angle between the blood vessel to be examined and the respective associated ultrasound head can be measured during a measurement of the organ perfusion. It is achieved that not only individual vessels and these are selectively examined, but that all the vessels of a tissue can be examined simultaneously to determine the actual flow rate in each vessel after an angle correction.

In addition, the cross-sectional area of all vessels in a tissue can be determined and compared to the total tissue cross-section.

Furthermore, hitherto difficult to carry out measurements in twisted and unbalanced vessels, z. As the umbilical cord, possible. This is justified by the fact that even a not ideally round shaped vessel in the cross section due to a sound angle <90 ° in the image has a higher area than a vessel orthogonal to the flow direction, but together with the changed speed by the Doppler effect and the tangent of the sound angle none Correction of the surface itself is necessary. By automatically counting the pixels and the programmatic interpretation of the color information on the basis of a scale on the edge of the ultrasound image you can multiply the converted in mm ² surface of the vessel in the image directly with the determined average speed and with the precisely determined by said device sound angle and one gets the same exact flow volume.

With the proposed technical solution can be made by a very accurate determination of the perfusion amount significantly more accurate statements on organ perfusion and the risks of disorders of organ function and organ morphology are better assessed. This is relevant to many medical applications, with the preferred use being related studies during pregnancy.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 2007/0073153 A1 [0014]
• US 2002/0042574 A1 [0014]
• US 6261233 B1 [0014]
• US 8622913 B2 [0015]

Claims (1)

A method for detecting organ perfusion based on sonographic methods according to the Doppler principle using a system for position detection, which is equipped with a targeted to the blood vessel to be examined transducer, characterized in that the system for detecting the position on the skin surface of the person to be examined in succession at least two different positions is arranged, wherein the detected in these two positions of the transducer and position detection system parameters of a computational evaluation are supplied by the volume flow (V) based on the parameters cross-sectional area, velocity and the determined sound angle by vector determination along the vessel axis based on at least two positions at a defined distance in one or more vessels according to a formula V. = V _measurement · A _measurement · tanα is calculated.

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