DE102014206155A1 - Method and device for controlling the acquisition of a data record - Google Patents

Abstract

A method for controlling the acquisition of an image data set for representing the propagation of a contrast agent in a region of interest of the human or animal body, characterized in that the acquisition is started and / or terminated based on a sensor signal (34, 36) of a sensor (30, 32) which detects the arrival of contrast agent in an arterial vessel (16) supplying the region of interest (12) or a draining venous vessel (18).

Description

The invention relates to a method and a device for controlling the acquisition of a data record for representing the propagation of a contrast agent in a region of interest of the human or animal body.

Perfusion measurements are well known in the art and are used, inter alia, for the diagnosis and therapy of strokes caused by a circulatory disorder in the brain. By means of perfusion measurements, such a reduced perfusion can be established and, based on this, if appropriate, a therapy can be proposed.

In a known method, a contrast agent is injected into a patient as a so-called bolus and its inflow and outflow through the capillaries of the tissue are monitored by medical imaging techniques. For this purpose, a temporal series of images of the area through which the contrast medium flows is recorded. From the dynamics of the inflow and outflow of the contrast agent through the perfused tissue can draw conclusions about the perfusion. For example, the timing of the flooding or flooding for a particular area of the tissue may be represented as an intensity-time curve representing the intensity value over time. From the curve, for example, the blood volume, the blood flow or the mean transit time of the blood can be determined by the tissue. Such methods are used in particular for measuring the blood flow of the brain.

The propagation of a contrast agent can be done for example by means of digital subtraction angiography (DSA). In this case, after the administration of a contrast agent, two-dimensional time series images are repeatedly recorded at a specific, fixed projection angle with an X-ray device, for example a C-arm X-ray device, whereby a reference image is subtracted from each image of the time series at a time when no contrast agent is present. In this way, the flooding of the contrast agent can be observed. This method can also be referred to as time-dependent, two-dimensional DSA.

In addition, methods are also known for performing three-dimensional perfusion measurements in a tissue. These are usually in the form of a perfusion CT or a perfusion MRI. In this case, a contrast medium bolus is likewise injected and subsequently a series of projection images are recorded at different projection angles at short time intervals. Perfusion data can also be derived from the temporally resolved spatially three-dimensional data set obtained in this way. In another known method, a C-arm X-ray device is used to perform a tomographic three-dimensional perfusion measurement.

In both the two-dimensional and three-dimensional perfusion measurements, there is the problem that the contrast medium injected into a vein only reaches the region of interest after a certain delay and therefore a favorable time for the start of the acquisition has to be determined. If started too early, the patient will be unnecessarily exposed to X-rays. If you start too late, valuable information about the beginning of the flooding may be lost.

In the prior art, prior to dynamic imaging with C-arm devices or CT systems, a contrast agent bolus is typically injected and tracked with the existing imaging to set a suitable delay of the acquisition relative to the injection. After this preliminary work, the actual acquisition of the data set, ie the two-dimensional or three-dimensional perfusion measurement, takes place.

The disadvantage here is that time needed for the pre-measurement with the contrast agent test bolus and contrast medium and X-ray dose must be used.

The invention has for its object to provide a method and apparatus for controlling the acquisition of a data set for determining the propagation of a contrast agent in a region of interest of the human or animal body available, which allow the fastest possible and less burdensome determination of the data.

The object is achieved by a method having the features of claim 1 and an apparatus having the features of claim 9. Preferred embodiments of the invention are specified in the dependent claims and the following description, in particular in conjunction with the accompanying figures.

The method according to the invention is characterized in that the acquisition is started and / or terminated based on a sensor signal from a sensor which detects the arrival of contrast agent in an arterial vessel supplying the region of interest or a draining venous vessel.

The device according to the invention comprises a sensor device with at least one A sensor configured to detect the arrival of contrast agent in an arterial vessel supplying the region of interest and / or a draining venous vessel, and a controller configured to start acquisition based on a sensor signal from the sensor device break up.

A first basic idea of the invention can be seen to provide, in addition to the actual acquisition device for acquisition of the image data set, a sensor device with at least one sensor which monitors the contrast agent bolus and gives a start signal or trigger signal to the acquisition device which initiates the acquisition ) starts or ends. Thus, no prior calibration with a test bolus is required, and the X-ray load can be reduced exactly to the perfusion phase of interest.

Preferably, a first sensor is positioned on a feeding vessel and / or a second sensor on a discharging (outflowing) vessel.

Thus, according to the invention, the acquisition or acquisition of the image data set is started by the detection of an injected contrast agent bolus in an artery which supplies the region of interest with blood and / or depending on the detection of the refluxing contrast agent in a vein through which the contrast agent from the region of interest drains, stops. The detection of the contrast agent is effected by a separate sensor, which operates independently of the sensors for the acquisition of the image data set. This is preferably an external sensor, that is to say a sensor which monitors or detects the contrast agent bolus non-invasively.

The image data set representing the propagation of the contrast agent in the region of interest may be a series of temporally successive two-dimensional spatial images. Such a two-dimensional perfusion measurement already contains valuable information from which certain parameters of the blood circulation can be derived.

According to the invention, however, it is preferred that the image data set is a chronological sequence of spatially three-dimensional data (three-dimensional perfusion measurement). The image data set can thus also be referred to as a dynamic, spatially three-dimensional image data set.

The region of interest of the human or animal body in which the propagation of the contrast agent is to be followed is preferably a tissue region. In this, the capillary blood flow should be displayed and evaluated if necessary.

The acquisition of the image data set is preferably a perfusion CT or a C-arm angiography.

With the method according to the invention and the device according to the invention, a contrast agent bolus can be detected automatically at the entrance or exit of a region of interest of the human or animal body. Based on the detection, the dynamic acquisition can be started and / or terminated.

The mixing of the contrast agent bolus with blood changes various properties of the blood which can be detected. For example, a slight hypoxia is produced by mixing with contrast agent in the blood. In addition, the flow properties (flow characteristic) can change due to the contrast agent. The change in the properties of the blood caused by the contrast agent is detected by the sensor and used to trigger the acquisition. Depending on the application, different methods can be used for detection.

The detection of the contrast agent (contrast agent bolus) is preferably carried out by an optical measuring method. In this case, the sensor preferably detects an optical change in the region of the arterial or venous vessel caused by the contrast agent. The optical sensor provided for this purpose allows non-invasive detection of the contrast agent in the vessel.

In a preferred embodiment, the sensor detects the optical change by means of infrared radiation. Preferably, a laser beam is directed to the corresponding vessel and determines the arrival of the contrast agent by detecting the laser beam. The use of infrared radiation makes it possible to detect vessels lying under the skin. Infrared radiation has a penetration into the skin of about 2.5 mm. Thus, a corresponding infrared sensor, which preferably comprises a transmitter and a receiver, for detecting contrast agent in a near-surface vessel is suitable. In a preferred embodiment, the method relates to the propagation of a contrast agent in the brain of a patient, which is supplied by a large, near-surface artery (carotid artery, carotid artery).

Preferably, a sensor is used to detect the arrival of the contrast agent bolus, which operates according to a reflection method. This allows, in contrast to a sensor operating according to the transmission method to monitor a near-surface vessel in a relatively thicker body region (for example, neck). The sensor measures the light beam reflected from the vessel, which is preferably infrared light. The sensor is particularly suitable for use in the neck region of a patient.

The change in the optical properties of the blood due to the contrast agent injection is based inter alia on an altered oxygen uptake of the blood or an altered oxyhemoglobin and deoxyhemoglobin content. According to the invention, it is preferred that the change in the oxyhemoglobin and / or deoxyhemoglobin content be detected for the detection of the contrast agent bolus.

The detection of the contrast agent can be achieved in a comparatively simple manner if the arrival of the contrast agent in a near-surface vessel is detected. A near-surface vessel is understood in particular to mean a vessel in the subcutaneous region. The detection in a near-surface vessel allows the use of an infrared laser with a penetration depth of a few millimeters, as described above. Thus, a comparatively simple and inexpensive sensor can be used for triggering the recording.

The triggering, ie the beginning and / or the termination, of the recording preferably takes place based on thresholds. Preferably, the acquisition of the data record is thus started and / or terminated when a predetermined threshold value is exceeded or undershot. The threshold value of the detected property of the blood in the vessel can be, for example, a specific value of an optical property or another property of the blood, for example the flow characteristic.

A further preferred embodiment of the method is that the acquisition is started and / or terminated within a predetermined, time delay after the detection of the contrast agent. The detection of the contrast agent in this context preferably refers to the exceeding or, if appropriate, undershooting of a specific threshold value of a measured property or change of the blood in the corresponding vessel. Depending on the location and purpose of the recording, it may be advantageous to start or end the recording with a certain time delay. By a suitable choice of the value of the delay, the radiation exposure can thus be limited even further to the relevant period.

The sensor is preferably set up to detect a change in a property of the blood in the vessel to be discharged or discharged.

In a further preferred embodiment, it is provided that the sensor detects a change in flow properties in the region of the vessel caused by the contrast agent.

In terms of the device, it is preferable for the sensor device to comprise a holding element which can be positioned on the neck or neck of a patient and which carries the at least one sensor. In this way, perfusion measurements of the brain can be started and / or stopped automatically in a comfortable way. The at least one sensor can be safely positioned in the region of a supply and / or discharge vessel.

Furthermore, it is preferred that the at least one sensor is adjustably fastened to the holding element. This makes it possible to position the sensor in the targeted area of the supplying and / or discharging vessel. The sensor device can therefore be used flexibly for different patients.

Preferably, the at least one sensor comprises an infrared laser. By emitting and receiving infrared laser light can be easily and reliably detect an optical change in a near-surface vessel, which is caused by the contrast agent.

• 1. Optische Topographie: Hierbei wird der Patient mit Licht im roten oder infraroten Bereich bestrahlt und die reflektierten Strahlen analysiert. Es wird der Unterschied zwischen Blut mit und Blut ohne Kontrastmittel registriert, wobei vorzugsweise keine exakte Quantifizierung erfolgt.
• 2. Diffuse optische Tomographie (Diffusion optical tomography): Hierbei wird rotes und Infrarotlicht (insbesondere nahes Infrarotlicht) aus unterschiedlichen Winkeln auf die Region von Interesse (das Gefäß) gestrahlt. Spezifische Wellenlängen des Lichts werden absorbiert oder reflektiert (gestreut), in Abhängigkeit der Konzentration von Hämoglobin.

Preferably, light, in particular infrared light, is irradiated at a defined angle onto the vessel to be monitored, where it is partially reflected. The reflected light is detected by a detector, which preferably has a plurality of IR photodiodes. Since the triggering of the image is only a binary decision (contrast agent or no contrast agent) and no quantification of the measured property is required, the resolution of the system can be comparatively coarse. The sensor is adapted to register a change in the optical properties of the reflection and scattering, which occurs due to the mixing of the blood with contrast agent. The following measuring methods can be used, for example:

• 1. Optical topography: The patient is irradiated with light in the red or infrared range and the reflected rays are analyzed. The difference between blood and blood without contrast agent is registered, whereby preferably no exact quantification takes place.
• 2. Diffuse optical tomography: Here, red and infrared light (especially near infrared light) from different angles to the region of Interest (the vessel) blasted. Specific wavelengths of light are absorbed or reflected (scattered), depending on the concentration of hemoglobin.

Other methods of optical imaging are also applicable.

The sensor uses a suitable threshold to distinguish between blood and blood with contrast agent. If this threshold is exceeded or undershot (depending on the calibration of the system), the trigger for recording is triggered. The sensors transmit the signal (sensor signal / trigger signal) directly to the acquisition system at the start or end of the recording. In principle, known trigger mechanisms can be used which are also used, for example, in ECG triggering.

In particular, the acquisition completion sensor is used to control the scan length, ie, the acquisition time. Here, the bolus signal in the dissipating vessel is used to signal the acquisition system that the recording can be terminated. For example, the completion of the recording can take place as soon as the bolus has reached a defined position in the discharge vessel. The termination can also take place after a defined delay. Depending on the setting of the threshold value or the delay, recirculation phenomena can also be considered.

Another application of the sensor to complete the detection may be that the corresponding sensor signal is used to determine the length of time of the bolus passage. An aspect of the invention may thus be seen to determine the time interval of circulation of the blood in the region of interest by determining the time interval of arrival of the bolus in the delivery and discharge vessels. This allows, for example, the extrapolation of data due to the knowledge of the time interval for the circulation. Thus, information can be reconstructed, which may not have been measured by X-ray based. For example, the venous outflow timing of a gamma variant fitting (or similar parametric function) can be used to complement a time-contrast curve for perfusion analysis. As a result, it is also possible, if appropriate, to reprocess recordings which have been subject to poor sampling or have been prematurely terminated by technical errors.

In a further embodiment of the method according to the invention, the acquisition is discontinued before the bolus reaches the venous outflow of the region of interest. Nevertheless, due to the knowledge of the time interval between inflow and outflow, the signal detected in the dissipating vessel can be used to extrapolate the data set.

Overall, the invention provides a method and a device in which, based on optical reflection and scattering, preferably an input bolus and an output bolus of the blood-contrast agent mixture are detected. The detected signal is used as a trigger for the acquisition. The temporal difference of the input and output trigger signals can be used for temporal extrapolation methods, which can be included in a perfusion analysis.

The invention will be further described below with reference to an exemplary embodiment, which is illustrated in the accompanying schematic drawings. Hereby shows:

1 an embodiment of a device according to the invention;

2 : an arterial input function;

3 a detector signal in a dissipative vessel; and

4 : a recording device for acquiring an image data set.

The basis of the 1 described embodiment of a device according to the invention 10 is used to carry out a method according to the invention, wherein the propagation of a contrast agent in a region of interest 12 , here in the brain, is measured (perfusion measurement of the brain). Such a perfusion measurement can be carried out in basically known manner by means of perfusion CT, perfusion MRI or by means of a C-arm device. Here, temporally successive projection images are taken from different directions and reconstructed into sectional images or three-dimensional volume images of the region of interest, wherein the recording is preferably carried out according to the principle of digital subtraction angiography (DSA). In each case, a mask image, which was recorded without contrast agent, is subtracted from the determined sectional or volumetric images. In this way, only the signal components of the contrast agent remain, so that the propagation of the contrast agent can be very well observed. The calculation of the volume or sectional images from the projection images takes place in a basically known manner.

The device 10 includes a sensor device 20 with a holding element 22 which is annular in the illustrated embodiment and for positioning on the neck or neck of a patient 50 is set up. On the holding element 22 or retaining ring are two sensors, namely a first sensor 30 and a second sensor 32 arranged. The sensors 30 . 32 are positioned so that they contact the skin of the patient with a holding element applied. Preferably, the sensors 30 . 32 adjustable on the retaining element 22 arranged so that they can each be positioned at a desired position on the circumference of the holding element. In this way it is possible, for example, the first sensor 30 on a feeding vessel 16 To position, for example, the carotid artery (common carotid, internal carotid or carotid artery). For example, the second sensor 32 can be in a similar manner to a laxative or effluent vessel 18 (Sinus) of the brain.

With the sensors 30 . 32 they are preferably optical sensors, each having a transmitter and a receiver, wherein the transmitter is adapted to light, preferably in the red or infrared region, to radiate to the corresponding vessel and the receiver is set, light reflected from the vessel to detect. Due to the detected light, the arrival of a contrast agent bolus can be detected in the supplying or outflowing vessel.

2 Figure 4 shows a concentration-time curve of the contrast agent in the afferent artery of the brain, also referred to as arterial input function (AIF). Here the abscissa shows the time and the ordinate the concentration. From a certain threshold of the detected signal, which corresponds to a certain concentration, a trigger signal is triggered, which is a recording device 40 (Acquisition facility) causes a recording or acquisition to start. Such a trigger signal is in 1 right next to the first sensor 30 shown. At a certain threshold value, a switching signal is thus triggered, by which - possibly delayed - a temporal series of recordings is started.

The second sensor 32 operates in an analogous manner and is set up to monitor the laxative vascular system such that the arrival of the refluxing contrast agent is detected. A corresponding concentration-time curve of the contrast agent in a laxative vessel is shown in FIG 3 shown. In comparison to 2 It can be seen that due to the distribution of the contrast agent in the brain area, the curve is flatter and usually time-stretched. By a corresponding calibration, a switching signal can be triggered at a predetermined value of the measured optical property, which corresponds to a certain concentration. Such a switching signal is in 1 right next to the second sensor 32 shown. By the switching signal, for example, the recording - possibly with a predetermined delay - be stopped. The detection of the contrast agent in the laxative vessel 18 may additionally or alternatively be used to determine the time interval for the circulation of the blood in the region of interest (here: the brain). If necessary, further values can be derived from this information and / or data can be extrapolated. The sensors 30 . 32 are set up, upon detection of the contrast agent, a sensor or trigger signal 34 . 36 to a receiving device 40 to send.

An exemplary embodiment of a receiving device 40 is in 4 shown. This is a C-arm device with an X-ray source 42 and an X-ray detector 43 on the arms of a C-arm 41 are attached. The C-arm 41 is a patient bed 48 pivotable. In the case of the X-ray detector 43 it is preferably a digital detector, which digital X-ray images of a patient on the bed 48 bedded patients 50 can generate. The C-arm 41 is movable on a stand 44 suspended.

The movement of the C-arm 41 and the acquisition of the X-ray images are by a control device 45 controlled. Further, the through the X-ray detector 43 acquired, digital x-ray images to the controller 45 be transmitted and processed there, so that the control device can also be referred to as a control and computing device. In this case, in particular by the X-ray detector 43 acquired projection images are combined into sectional images and / or volume images. The control device 45 accesses a data store 46 which is configured, inter alia, for storing X-ray images. The control device 45 as well as the data memory 46 can be part of a calculator 47 be, for example, a PC, a workstation or a console. In addition, a screen for displaying X-ray images and input devices such as keyboard and / or mouse may also be present. The control device 45 receives the trigger signals 34 . 36 the sensors 30 . 32 ,

Claims (12)

A method for controlling the acquisition of an image data set for representing the propagation of a contrast agent in a region of interest of the human or animal body, characterized in that the acquisition is based on a sensor signal ( 34 . 36 ) of a sensor ( 30 . 32 ) is started and / or terminated, which the Arrival of contrast agent in a region of interest ( 12 ) supplying arterial vessel ( 16 ) or a draining, venous vessel ( 18 ) detected. Method according to claim 1, characterized in that the sensor ( 30 . 32 ) caused by the contrast agent, optical change in the region of the vessel ( 16 . 18 ) detected. Method according to claim 1 or 2, characterized in that the sensor ( 30 . 32 ) determines the optical change by means of infrared radiation. Method according to one of claims 1-3, characterized in that the sensor ( 30 . 32 ) works according to a reflection method. Method according to one of claims 1-4, characterized in that the arrival of the contrast agent in a near-surface vessel ( 16 . 18 ) is detected. Method according to one of claims 1-5, characterized in that the acquisition of the data set is started and / or terminated when a predetermined threshold is exceeded or undershot. A method according to claim 6, characterized in that the acquisition is started and / or terminated within a predetermined, time delay after the detection of the contrast agent. Method according to one of claims 1-7, characterized in that the sensor ( 30 . 32 ) a change of flow properties in the region of the vessel caused by the contrast agent ( 16 . 18 ) detected. Device for controlling the acquisition of a data set for determining the propagation of a contrast agent in a region of interest ( 12 ) of the human or animal body, comprising a sensor device ( 20 ) with at least one sensor ( 30 . 32 ) arranged to detect the arrival of contrast agent in an arterial vessel supplying the region of interest ( 16 ) and / or a draining venous vessel ( 18 ) and a control device ( 45 ), which is set up, based on a sensor signal ( 34 . 36 ) of the sensor device ( 20 ) to start or end the acquisition. Apparatus according to claim 9, characterized in that the sensor device ( 20 ) on the neck area ( 14 ) a patient positionable retaining element ( 22 ) comprising the at least one sensor ( 30 . 32 ) wearing. Apparatus according to claim 9 or 10, characterized in that the at least one sensor ( 30 . 32 ) adjustable on the holding element ( 22 ) is attached. Device according to one of claims 9-11, characterized in that the at least one sensor ( 30 . 32 ) comprises an infrared laser.

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