METHOD OF IMAGING

Abstract

A method of imaging motion of an organ that changes volume in a patient including the steps of monitoring change in volume of the organ, and recording multiple in vivo images of the organ, wherein the change of organ volume between the images is constant or of some other predetermined value.

Claims

1. A method of measuring an organ motion of an organ, the method comprising: monitoring a change of a parameter value corresponding to motion of the organ during at least one respiration cycle; upon each of a plurality of occurrences of a same change in the parameter value during the at least one respiration cycle, triggering an acquisition of in vivo images of the organ; and measuring the organ motion between two or more of the in vivo images.

2. The method of claim 1, wherein measuring the organ motion comprises: reconstructing a spatial velocity of motion from the in vivo images.

3. The method of claim 1, wherein: monitoring the change in parameter value comprising creating monitoring data that is fed in real time to an imaging control system, and triggering an acquisition of in vivo images of the organ is carried out in response to an actuation signal from a signal processing system.

4. The method of claim 3, wherein: triggering an acquisition of in vivo images of the organ comprises: acquiring a first plurality of in vivo images from a first perspective in response to an actuation signal from the imaging control system, and acquiring a second plurality of in vivo images of the organ from at least one further perspective in response to an actuation signal from the imaging control system, and measuring the organ motion comprises subsequently, reconstructing a spatial velocity of organ motion from the first plurality of in vivo images and the second plurality of in vivo images.

5. The method of claim 1, wherein: triggering the acquisition of in vivo images of the organ comprises acquiring a first plurality of in vivo images of the organ from a first perspective and acquiring a second plurality of in vivo images of the organ from a second perspective, and measuring the organ motion comprises subsequently, reconstructing a spatial velocity of organ motion from in vivo images acquired from the first perspective and the second perspective.

6. The method of claim 1, wherein the change of a parameter value corresponding to motion is a change in any one or any combination of shape, volume, flow, pressure, shear, displacement, orientation, or location of the organ.

7. The method of claim 6, wherein the change of a parameter value corresponding to motion is a change in displacement of the organ.

8. The method of claim 1, wherein at least three in vivo images of the organ are acquired.

9. The method of claim 1, wherein the same change of the parameter value is a predetermined value.

10. The method of claim 1, wherein the same change of the parameter value is a predetermined constant value.

11. The method of claim 1, wherein the in vivo images comprise in vivo fluoroscopy x-ray images.

12. The method of claim 1 wherein the organ is a lung.

13. A system comprising: one or more energy sources; one or more detectors configured to acquire in vivo images of an organ created by energy from the one or more energy sources passing through a subject intermediate the energy source and detector; and a signal processing system coupled to the one or more energy source and the one or more detectors and configured to: monitor a change of a parameter value corresponding to an organ motion of the organ during at least one respiration cycle; upon each of a plurality of occurrences of a same change in the parameter value during the at least one respiration cycle, trigger an acquisition of in vivo images of the organ; and measure the organ motion between two or more of the in vivo images.

14. The system of claim 13, wherein the signal processing system is configured to measure the organ motion by being configured to: reconstruct a spatial velocity of motion from the in vivo images.

15. The system of claim 13, wherein: the signal processing system is configured to monitor the change in parameter value by being configured to create monitoring data in real time, and the triggering of an acquisition of in vivo images of the organ is carried out in response to an actuation signal.

16. The system of claim 15, wherein: the signal processing system is configured to trigger an acquisition of in vivo images of the organ by being configured to: acquire a first plurality of in vivo images from a first perspective in response to an actuation signal, and acquire a second plurality of in vivo images of the organ from at least one further perspective in response to an actuation signal, and the signal processing system is configured to measure the organ motion by being configured to subsequently, reconstruct a spatial velocity of organ motion from the first plurality of in vivo images and the second plurality of in vivo images.

17. The system of claim 13, wherein: the signal processing system is configured to trigger an acquisition of in vivo images of the organ by being configured to acquire a first plurality of in vivo images of the organ from a first perspective and acquire a second plurality of in vivo images of the organ from a second perspective, and the signal processing system is configured to measure the organ motion by being configured to subsequently, reconstruct a spatial velocity of organ motion from in vivo images acquired from the first perspective and the second perspective.

18. The system of claim 13, wherein the change of a parameter value corresponding to motion is a change in any one or any combination of shape, volume, flow, pressure, shear, displacement, orientation, or location of the organ.

19. The system of claim 13, wherein at least three in vivo images of the organ are acquired.

20. A non-transitory computer readable storage medium storing computer executable code, comprising instruction for causing an apparatus to: monitor a change of a parameter value corresponding to an organ motion of an organ during at least one respiration cycle; upon each of a plurality of occurrences of a same change in the parameter value during the at least one respiration cycle, trigger an acquisition of in vivo images of the organ; and measure the organ motion between two or more of the in vivo images.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Further disclosure, objects, advantages and aspects of preferred and other embodiments of the present application may be better understood by those skilled in the relevant art by reference to the following description of embodiments taken in conjunction with the accompanying drawings, which are given by way of illustration only, and thus are not limitative of the disclosure herein, and in which:

[0065] FIGS. 1a and 1b illustrate lung inspiration and expiration by plots of lung volume against time (sec) (FIG. 1a, also referred to herein as FIG. 1a) and lung air pressure (cm/H.sub.2O) versus time (sec) (FIG. 1b, also referred to herein as FIG. 1b).

[0066] FIGS. 2a and 2b are plots of lung volume against time as shown in FIG. 1a, marked up to indicate a scanning regime according to the present invention during inspiration and expiration (FIG. 2a, also referred to herein as FIG. 2a) and during expiration alone (FIG. 2b, also referred to herein as FIG. 2b).

[0067] FIGS. 3a and 3b are plots of lung volume against time as shown in FIG. 1a, marked up to indicate a scanning regime according to the prior art during inspiration and expiration (FIG. 3a, also referred to herein as FIG. 3a) and during expiration alone (FIG. 3b, also referred to herein as FIG. 3b).

[0068] FIG. 4 illustrates a typical arrangement of components in a CTXV scanner.

[0069] FIGS. 5a and 5b illustrate the output from the application as it detects when to trigger the imaging system based on a constant and preset change of volume (FIG. 5a, also referred to herein as FIG. 5a) and the non-linear time base is depicted on a subset of the same data (FIG. 5b, also referred to herein as FIG. 5b).

[0070] FIG. 6 is a flow chart summarizing the function of one embodiment of the application of a system according to the present invention.

[0071] FIG. 7 is a graph illustrating radiation dose savings according to the present invention for preset volume change value for a system that is ordinarily run at 30 fps. This data can also be seen in Table 1.

[0072] FIGS. 8a and 8b illustrate the system (FIG. 8a, also referred to herein as FIG. 8a) and apparatus (FIG. 8b also referred to herein as FIG. 8b) used for the method of this invention.

DETAILED DESCRIPTION

[0073] FIG. 1a is a plot of lung volume (liters) versus time (sec) during inspiration and expiration of a human lung. The plot illustrates inspiratory reserve volume (IRV) 1, VT 2, expiratory reserve volume (ERV) 3, residual volume (RV) 4, functional reserve capacity (FRC) 5, inspiratory capacity (IC) 6, vital capacity (VC) 7, total lung capacity (TLC) 8

[0074] FIG. 1b is a plot of pressure (cm/h.sub.2O) versus time (ms) for inspiration and expiration of a human lung. The flow of air into and out of the lung can be correlated with the change in volume of the lung as shown in FIG. 1a.

[0075] In the past, images of organs that change volume, such as the heart, blood vessels or lungs have been recorded at the fastest imaging rate possible with a constant time between images.

[0076] With reference to lungs, this was an attempt to capture the fast motion that occurs during the beginning of the inspiratory cycle and the beginning of the expiratory cycle. FIG. 3 is a plot of lung volume (liters) against time (sec) that illustrates sequential scanning according to the prior art technique during inspiration and expiration (FIG. 3a) and during expiration only (FIG. 3b) with a constant time period between each image.

[0077] However, as illustrated in FIG. 3a, this will result in many images being captured during the end of inspiration and expiration where the volume (and pressure) curves have begun to asymptote towards their final values and little lung motion is actually happening.

[0078] By contrast, FIG. 2 illustrates volume based gating for scanning according to the present invention with a constant lung volume change between each image. FIG. 2 is a plot of lung volume against time during inspiration and expiration (FIG. 2a) and during expiration alone (FIG. 2b). Thus, for a predetermined unit of air flow or change in lung volume, a predetermined number of images can be taken. This optimizes the proportion of images taken during the course of inspiration and expiration when the lung is working hardest and the most information regarding its health can be obtained. It also minimizes the number of images taken at other times, such as the end of inspiration and expiration when the lung is not working as hard, concomitantly minimizing the dosage of radiation.

[0079] The method of the present invention does not require images to be taken as fast as possible at over-power levels. Instead, using the method of the present invention the CTXV scanner can be run at a lower power level without the need to cool-down, or for a shorter cool-down period. This allows more efficient throughput of patients, lower power usage, and thus overall better economy of usage of a CTXV scanner.

[0080] The current invention is particularly valuable when used in CTXV imaging and CTXV scanners of the prior art as depicted in FIG. 4. FIG. 4 is a schematic diagram outlining the basic design of a CTXV system according to the present invention. The diagram shows three polychromatic X-ray beams transmitted through a sample and converted to visible light by scintillators. High-speed detector systems then produce a set of images. Multiple projection data are gathered simultaneously without rotating the sample. Coordinates (typically Cartesian co-ordinates (x, y, z)) are fixed to the sample and rotated at an angle from the beam axis p. With reference to FIG. 4, each imaging line would typically consist of the following key components:

[0081] a. video speed or double shutter X-ray camera (21);

[0082] b. cone beam X-ray source (22);

[0083] c. source modulation system (23);

[0084] d. basic source alignment hardware (24a);

[0085] e. high-resolution camera alignment hardware (24b);

[0086] f. image capture and analysis hardware (25); and

[0087] g. user interface (26).

[0088] FIG. 5 shows an actual volume vs time graph captured from a subject. The points chosen to trigger for image acquisition correlates to an equal volume spacing between images. This can be seen more clearly in FIG. 5b.

[0089] FIG. 6 shows a flowchart of one particular embodiment of the application relating to this technology. This lists the processing steps that can occur for this technique to be used effectively.

[0090] Table 1 displays an example of the dose savings that can be achieved using this technique.

TABLE-US-00001 TABLE 1 Examples of Dose Saving for a Given Volume interval Volume Number of frame Dose reduction L Standard 30 fps Triggered Saving 0.1 90 34 62% 0.2 90 19 79% 0.3 90 13 86% 0.4 90 10 89% 0.5 90 9 90% 0.6 90 7 92% 0.7 90 6 93% 0.8 90 6 93% 0.9 90 5 94% 1 90 4 96% 1.1 90 4 96%

[0091] FIG. 7 is a plot showing the dose reduction that is possible using the method of the present invention on a 30 frame per second imaging system as compared with imaging at a constant rate. The plot shows how the dose reduction changes (30) as the predetermined volume change of the lungs is set to different levels (triggered 32).

[0092] FIG. 8 shows the system and apparatus of the present invention. The physiological input (39) is sent from the patient located between the source (42) and the detector (44) to the sensor (48). The signal processing system (38) in FIG. 8a shows how a physiological parameter is used for controlling the timing of image acquisition of FIG. 8b. The sensor turns this physiological information into a parameter signal (50) that is then sent to the signal processing unit (52). The signal processing unit converts the signal to an appropriate trigger (40) that feeds into the imaging system controller (46). The signal processing may include some other input information from the user such as preset volume change value or an equation for a series of volume change values or another set of rules by which the input physiological information is to be converted to an appropriate triggering signal for the imaging system.

[0093] Typically, a CTXV scanner of this type comprises multiple energy sources and multiple detectors used simultaneously or in close temporal sequence. This current invention, when utilized in CTXV imaging (irrespective of the number of energy/detector pairs) includes application to imaging of animals and also application to imaging of humans. Due to the nature of CTXV technology often being utilized for direct measures of lung volume change, dramatic reductions in dose can be achieved for little or no loss of information gathered during a scan by using a volume based gating system.

[0094] While this invention has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modification(s). This application is intended to cover any variations uses or adaptations of the invention following in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth.

[0095] As the present invention may be embodied in several forms without departing from the spirit of the essential characteristics of the invention, it should be understood that the above described embodiments are not to limit the present invention unless otherwise specified, but rather should be construed broadly within the spirit and scope of the invention as defined in the appended claims. The described embodiments are to be considered in all respects as illustrative only and not restrictive.

[0096] Various modifications and equivalent arrangements are intended to be included within the spirit and scope of the invention and appended claims. Therefore, the specific embodiments are to be understood to be illustrative of the many ways in which the principles of the present invention may be practiced. In the following claims, means-plus-function clauses are intended to cover structures as performing the defined function and not only structural equivalents, but also equivalent structures.

[0097] Comprises/comprising and includes/including when used in this specification is taken to specify the presence of stated features, integers, steps, or components but does not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof. Thus, unless the context clearly requires otherwise, throughout the description and the claims, the words comprise, comprising, includes, including and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of including, but not limited to.