WO2009101572A2

WO2009101572A2 - X- ray apparatus, particularly for security applications

Info

Publication number: WO2009101572A2
Application number: PCT/IB2009/050526
Authority: WO
Inventors: Udo Van Stevendaal; Peter Forthmann
Original assignee: Koninklijke Philips Electronics N.V.; Philips Intellectual Property & Standards Gmbh
Priority date: 2008-02-14
Filing date: 2009-02-09
Publication date: 2009-08-20
Also published as: WO2009101572A3

Abstract

The invention relates to an X-ray apparatus (100) and a method for the examination of a subject (1), comprising the irradiation of the subject (1) with X-rays and the detection of backscattered/reflected photons (X') as well as transmitted photons (X). The apparatus may particularly be used in security applications, e.g. at an airport, for detecting suspect things concealed by a person (1). As an additional benefit, the transmission images of the person (1) may be evaluated with respect to medical anomalies, for example suspect lung nodules.

Description

X-ray apparatus, particularly for security applications

FIELD OF THE INVENTION

The invention relates to an X-ray apparatus and a method for examining a subject, particularly a person in a security application.

BACKGROUND OF THE INVENTION

The US 5 181 234 discloses an apparatus and a method for producing an image of a person and any suspect objects concealed by said person from scattered and reflected X-rays. A problem of this and similar devices for security applications is that all examined persons are exposed to X-ray doses though the normal case is that none of them carries suspect objects. This considerably limits the acceptance of such security measures.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide alternative means for an X-ray examination of subjects, wherein it is desirable that the acceptance of these means in security applications is increased.

This object is achieved by an X-ray apparatus according to claim 1 and a method according to claim 8. Preferred embodiments are disclosed in the dependent claims.

The X-ray apparatus according to the present invention is intended for the examination of a subject, particularly (but not exclusively) of persons in security areas like an airport. It comprises the following components: a) An X-ray source for irradiating the subject with X-rays. Suitable X-ray sources are well known in the art; they typically comprise a high- voltage unit with a cathode bombarding an anode with electrons such that the latter emits X-rays. The X-ray source usually further comprises a suitable aperture for forming an X-ray beam with a desired shape, spectrum and/or intensity. b) A detector, which will be called "backscatter-detector" in the following and which detects photons that are generated from the aforementioned X-rays by backscattering and/or reflection. The spectral sensitivity of this detector will therefore be adapted to the expected spectrum of backscattered and reflected photons in view of the emission spectrum of the X-ray source. c) A further detector, which will be called "transmission-detector" in the following and which can detect X-ray photons of the X-ray beam emitted by the X-ray source that were transmitted through the subject. Again, the sensitivity of the detector has to be chosen appropriately in view of the expected spectrum of transmitted X-ray photons.

Both the backscatter-detector and the transmission-detector can for example be realized as solid state devices comprising pixels in which incident photons are directly or indirectly (via visible photons) converted into electrical signals.

The described X-ray apparatus has the advantage to allow simultaneously the detection and evaluation of both backscattered/reflected and transmitted X-ray photons. Thus no information is lost and the X-ray dose to which the subject has been exposed is optimally exploited. The X-ray apparatus may further optionally comprise a signal processing device, for example a microcomputer with associated hardware and software, adapted for assisting the detection of predetermined materials and/or objects carried by the examined subject, wherein this detection is (at least partially) based on the signals of the backscatter- detector. The signal processing device allows particularly the use of the X-ray apparatus in security applications, where suspect materials or objects like concealed weapons or explosives shall be detected. The assistance that is provided by the signal processing device may for example comprise the reconstruction of an image of the examined subject in which a human observer can visually detect suspect items, or it can comprise additional automatic evaluation procedures (cf. US 5 181 234). The X-ray examination of the subject may take place in a static set-up, i.e. with fixed relative positions of the X-ray source, the subject, and the detectors. In a preferred embodiment, the X-ray apparatus comprises however a carrier for the subject, wherein said carrier can rotate (e.g. driven by a motor) relative to the X-ray source, the backscatter- detector and/or the transmission-detector. Preferably, the latter three components have fixed relative positions and the carrier with the subject rotates relative to all of them. It should be noted that the rotation is relative, i.e. any of the involved components may move (or rest) with respect to the environment. The relative rotation between subject and examination components allows to X-ray the subject from different viewing angles. The X-ray apparatus preferably further comprises an image processing device for processing the detection signals provided by the transmission-detector. As said signals will usually be (analogue or digital) electronic signals, the image processing device is typically realized by specialized electronic hardware and/or digital data processing hardware with associated software.

The aforementioned image processing device may particularly comprise a reconstruction module for reconstructing a cross-sectional image of the subject from projection images generated under different viewing angles (wherein the term "cross- sectional image" shall comprise a three-dimensional image of the subject or a part thereof). The reconstruction of such cross-sectional images may be done according to the methods of Computed Tomography (CT) which are well known to persons skilled in the art.

In another embodiment, the image processing device may comprise a Computer- Aided-Diagnosis (CAD) module for evaluating signals provided by the transmission-detector with respect to medical anomalies, particularly with respect to suspect lung nodules. The evaluated signals may especially constitute projection images of the subject generated by the transmitted X-ray photons, or they may constitute cross-sectional images of the kind described above. CAD methods are increasingly applied in medical imaging (cf. US 4 907 156, US 7 072 435). The integration of CAD methods allows to provide an X-ray apparatus that is used in a security application with an additional functionality, i.e. the screening for potential diseases. This is particularly relevant for lung cancer, which is one of the leading causes of cancer related deaths, with the survival rate critically depending on an early diagnosis. A person admitting a security examination with such an X-ray apparatus will therefore have the opportunity of an additional medical check - without additional cost in terms of X-ray dose. This is a real benefit for the normal, non-criminal person, which can highly increase the acceptance of X-ray examinations for security purposes.

According to a further a development of the aforementioned embodiment, the image processing device may be adapted to emit some indication or alarm signal in case an anomaly is detected. Thus the X-rayed persons can be informed about the detection result and for example consult a radiologist for further diagnosis.

The invention further relates to a method for the examination of a subject, the method comprising the following steps: a) Irradiating the subject with X-rays. b) Detecting backscattered and/or reflected photons. c) Simultaneously detecting transmitted X-ray photons.

The method comprises in general form the steps that can be executed with an X-ray apparatus of the kind described above. Reference is therefore made to the above descriptions for more information on the details, advantages and modifications of said method.

Particularly in security applications, the detected backscattered and/or reflected photons may be evaluated with respect to predetermined ("suspect") materials and/or objects carried by the subject.

According to another variant of the method, an image of the subject is reconstructed from the transmitted X-ray photons and automatically evaluated with respect to medical anomalies. In combination with the aforementioned embodiment, the method then provides both a security check and a medical screening.

BRIEF DESCRIPTION OF THE DRAWING These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. These embodiments will be described by way of example with the help of the accompanying single drawing, in which:

Figure 1 shows schematically a top view onto an X-ray examination apparatus according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

X-ray machines may be used at airports for screening passengers based on backscattered X-rays. Such a screening is usually voluntary, takes about one minute and requires a turning around of the passengers. In order to use also the transmitted X-rays and to prevent that invested dose goes to waste, it is suggested here to extend such an airport screening machine by a detector for transmitted X-rays. With this, the passengers that have agreed to an X-ray search would on top get transmission images, which they, or rather their radiologist, could use for diagnostic purposes. This is particularly interesting in view of lung cancer, which is the second leading cancer in the United States and the leading cause of cancer-related death among men and women. In the US alone, more than 150000 lung cancer-associated deaths occur per year. An early detection of lung cancer can increase the five-year survival rate from only 5 % to 70 %. Since a dedicated screening method takes the risk of inadequate X-ray exposure to volunteers, some effort is undertaken to define ultra-low dose CT protocols on the one hand (R. Wiemker, P. Rogalla, R. Opfer, A. Ekin, V. Romano, T. Bϋlow, "Comparative Performance Analysis for Computer Aided Lung Nodule Detection and Segmentation on Ultra-Low-Dose vs. Standard-Dose CT", in Proceedings of the SPIE Medical Imaging Conference 2006; V. Romano, U. Zaspel, P. Hein, T. Elgeti, B. Hamm, P. Rogalla, "MSCTR performed at a chest radiograph dose: Detection and characterization of pulmonary nodules compared with standard-dose CT", Proc. Radiol. Soc. of North America RSNA'03 SSA04-07, 2004) or to look for incidental findings in data sets acquired for other reasons, e.g. cardiac screening, on the other hand (S. Abbara, "Incidental findings", 5th International Conference on Cardiac CT). Figure 1 illustrates an X-ray examination apparatus 100 according to the present invention. For its intended use in e.g. a security check at an airport or other public location, the X-ray apparatus 100 comprises some housing or cabin 10 with a wall 11 and a rotatable plate 12 in its centre. A passenger 1 who shall be examined can stand on the plate 12 and then slowly be rotated around 360° while being exposed to X-rays X emitted by an X-ray source 20.

A backscatter-detector 30 extends to both sides of the X-ray source 20 for collecting photons X' that were generated in the person 1 by backscattering and/or reflection of the X-ray photons X emitted by the X-ray source 20. The backscatter-detector 30 is coupled to a signal processing device 60 that is adapted to evaluate the detected signals with respect to suspect materials and/or objects carried by the person 1, e.g. explosives or weapons.

In the optical path of the X-rays X emitted by the X-ray source 20 and behind the person 1, a transmission-detector 40 is disposed for the detection of transmitted X-rays. This transmission-detector 40 is coupled to an image processing device 50 for the processing and evaluation of the detector signals. The image processing device 50 may for example be realized by a microcomputer with associated software. It preferably comprises a reconstruction module 51 (realized in hardware and/or software) for the reconstruction of cross-sectional (e.g. 3D) images from projection images generated from different directions during the rotation of the person 1. The result of the image reconstructions may be supplied to a Computer- Aided-

Diagnosis (CAD) module 52 in which they are automatically evaluated with respect to medical anomalies, e.g. pulmonary nodules and possibly other malignant anomalies. The entire process is fully non-interactive up to this point. In case an anomaly is detected, the CAD module 52 activates an alarm unit 53 via which the operator and/or the person 1 are given a feedback about the detection result. The person 1 may then let a radiologist review the image data and/or make further medical examinations.

The described apparatus 100 provides persons 1 that take the trouble of an X-ray security investigation with the benefit of a medical check. This is particularly reasonable with respect to diseases having high incidence and mortality rates, e.g. lung cancer.

Finally it is pointed out that in the present application the term "comprising" does not exclude other elements or steps, that "a" or "an" does not exclude a plurality, and that a single processor or other unit may fulfill the functions of several means. The invention resides in each and every novel characteristic feature and each and every combination of characteristic features. Moreover, reference signs in the claims shall not be construed as limiting their scope.

Claims

CLAIMS:

1. An X-ray apparatus (100) for the examination of a subject (1), comprising: a) an X-ray source (20) for irradiating the subject (1) with X-rays (X); b) a backscatter-detector (30) for detecting photons (X') that are backscattered and/or reflected from the subject (1); c) a transmission-detector (40) for detecting X-ray photons (X) that were transmitted through the subject (1).

2. An X-ray apparatus (100) according to claim 1, characterized in that it comprises a signal processing device (60) for assisting the detection of predetermined materials and/or objects based at least partially on the signals of the backscatter-detector (30).

3. An X ray apparatus (100) according to claim 1, characterized in that it comprises a carrier (12) for the subject (1) which can rotate relative to the X-ray source (20), the backscatter-detector (30), and/or the transmission-detector (40).

4. An X ray apparatus (100) according to claim 1, characterized in that it comprises an image processing device (50) for processing the detection signals provided by the transmission-detector (40).

5. An X ray apparatus (100) according to claim 4, characterized in that the image processing device (50) comprises a reconstruction module (51) for reconstructing a cross-sectional image of the subject (1) from projection images taken from different angles.

6. An X ray apparatus (100) according to claim 4, characterized in that the image processing device (50) comprises a Computer- Aided Diagnosis module (52) for evaluating the signals provided by the transmission-detector (40) with respect to medical anomalies, particularly suspect lung nodules.

7. An X ray apparatus (100) according to claim 6, characterized in that the image processing device (50) is adapted to emit an alarm signal if an anomaly is detected.

8. A method for the examination of a subject (1), comprising: a) irradiating the subject (1) with X-rays (X); b) detecting backscattered and/or reflected photons (X'); c) simultaneously detecting transmitted X-ray photons (X).

9. The method according to claim 8, characterized in that the detected backscattered and/or reflected photons (X') are evaluated with respect to predetermined materials and/or objects carried by the subject (1).

10. The method according to claim 8, characterized in that the transmitted X-ray photons (X) are automatically evaluated with respect to medical anomalies.

11. A computer program product for enabling carrying out a method according to claim 8.

12. A record carrier on which a computer program according to claim 11 is stored.

13. Transmission of the computer program product according to claim 11 over a local or wide area telecommunications network.