Patent Description:
In correctional facilities and at national borders, there is a need to detect contraband such as weapons, narcotics, mobile telephones, and other objects. Objects may be concealed internally or externally, for example in clothing, in body cavities such as the mouth or anal canal, hidden in prosthetics such as artificial limbs, they may also be swallowed or even surgically implanted.

Detection of such contraband is necessary for law enforcement, and to maintain order in correctional facilities, and to control the transit of contraband across national borders. It has been proposed to use imaging techniques based on ionising radiation, such as transmission X-ray, to identify contraband hidden in the human or animal body.

Techniques such as transmission X-ray are advancing rapidly. Human and animal bodies can be inspected in their entirety, from head to toe, and even the smallest item of contraband may be identifiable - regardless of where it has been hidden.

It may therefore have been thought that there is no need to develop alternative techniques. Commonly held prejudice would suggest that the problem of detection of contraband has been conclusively solved.

The present application however identifies a hitherto unrecognised opportunity to advance conventional techniques.

<CIT> discloses a searching system using X-ray and millimetre-wave signal.

<CIT> discloses an integrated walk-through personnel scanner system for security portals.

Aspects and embodiments of the present disclosure, such as those set out in the appended claims, aim to address the above mentioned technical problem, and related technical problems.

In an aspect, there is provided a method of scanning a clothed human subject. The method comprises: obtaining first scan data using a first scanner by illuminating the subject with a first source of radiation adapted for scanning soft tissue surfaces hidden by the subject's clothing; obtaining second scan data by illuminating the subject with a second source of radiation that is directed more towards the subject's torso than towards other parts of their body, wherein the second source of radiation comprises tissue penetrating radiation; obtaining first image data based on the first scan data and second image data based on the second scan data; and indicating a body region shown in the second image data based on a feature of the first image data. The method may comprise identifying a feature in the first scan data by comparing the first scan data with comparator data. The comparator data may comprise reference data associated with the subject. The first scan data may comprise image data and the reference data may comprise stored image data obtained from the subject.

In an aspect, there is provided a scanning apparatus for scanning a clothed subject. The apparatus comprises: a first scanner configured to scan surfaces hidden by the subject's clothing to obtain first scan data; a second scanner configured to scan internal structures of the subject's body to obtain second scan data and comprising a source of tissue penetrating radiation arranged to direct radiation more towards the subject's torso than towards other parts of their body; and a controller configured to obtain first image data based on the first scan data and second image data based on the second scan data and to indicate a body region shown in the second image data based on a feature of the first image data.

The apparatus may comprise an imaging region in which the subject is to be provided in a selected position, wherein the source of tissue penetrating radiation is arranged to illuminate the torso of a human subject in the selected position. The first scanner and the second scanner may be coupled to a rigid support structure adapted to provide a selected spatial relationship between the first scanner and the second scanner. The selected spatial relationship may be variable or fixed, and the controller may be adapted to transform at least one of: (a) the scan of surfaces hidden by the subject's clothing; and (b) the scan of internal structure of the subject's body based on the selected spatial relationship.

Aspects and embodiments of the disclosure will now be explained, by way of example only, with reference to the accompanying drawings, in which:.

In the drawings like reference numerals are used to indicate like elements.

<FIG> shows a schematic illustration of a scanning apparatus. The apparatus illustrated in <FIG> comprises a first scanner <NUM> and a second scanner <NUM>. The first scanner <NUM> is arranged to use a first radiation type to detect hidden objects concealed by a subject's clothing. It is operable to scan soft tissue surfaces, such as skin, hidden beneath the subject's clothing.

As illustrated, this apparatus also comprises a second scanner <NUM>. The second scanner <NUM> comprises a second radiation provider <NUM>-<NUM> and a second radiation detector <NUM>-<NUM> and is arranged to use a second radiation type comprising a tissue penetrating radiation to scan a subject. Data obtained by this scanning may be used to provide transmission image data of the interior of the same subject's torso. The second type of radiation is directed at the subject's torso more than at other parts of their body. For example their abdomen may be illuminated more than the rest of their body.

Embodiments of the disclosure may therefore provide better quality inspection of human subjects because they permit higher power tissue penetrating radiation to be used to detect objects in the torso than would otherwise be the case. Optimised optics may also be used to enable greater magnification to be provided - for example by placing the source of a fan beam closer to the subject while moving the detector relatively further away. The use of the first scanner <NUM> provides detection of objects concealed beneath clothing, and may enable surface irregularities to be detected. This information can then be combined with the transmission image data from their torso to provide sensitive, reliable, detection of non-tissue objects such as concealed contraband. Counterintuitively therefore, excluding body parts such as the limbs and head from exposure to the tissue penetrating radiation may provide more thorough inspection.

Methods and apparatus of the present disclosure may be arranged to shield at least a part of the subject's body from the second type of radiation. For example at least a part of the head and/or one or more of the limbs may be shielded from the second type of radiation. By contrast to the second type of radiation, the first type of radiation may illuminate most of the subject's body. For example it may illuminate one or more of their limbs at least partially, and may also illuminate their head. The first type of radiation may be delivered more evenly across the body than the second type of radiation. The first radiation type may comprise non-ionising radiation such as millimetre wave, terahertz, and infrared radiation. Other examples of non-ionising radiation include high frequency acoustic signals such as ultrasound.

In <FIG>, there is illustrated an imaging region, which may be demarcated by a portal, sized to allow passage of an upright human adult. In <FIG> shows a side view with the subject in profile standing in the imaging region. <FIG> shows the arrangement of <FIG> in plan.

The first scanner <NUM> of <FIG> includes a part <NUM>-<NUM> arranged to the front of the imaging region for scanning the face and front of the subject's body, and a part <NUM>-<NUM> arranged to the rear of the imaging region for scanning the back of the subject's body. Each part <NUM>-<NUM>, <NUM>-<NUM> includes radiation providers and radiation detectors, for example transmit/receive antennae. The second scanner <NUM> is different in that the radiation provider <NUM>-<NUM> and the radiation detector <NUM>-<NUM> are separated by the imaging region. This enables the second scanner to scan the imaging region by passing radiation from the second radiation provider <NUM>-<NUM>, through the subject <NUM> to the second radiation detector <NUM>-<NUM>.

Accordingly, in the example shown in <FIG>, the first scanner <NUM> includes a front view part <NUM>-<NUM> comprising a first radiation provider and first radiation detector arranged to scan the front of the subject's body. It also comprises a back view part <NUM>-<NUM> also having a first radiation provider and first radiation detector arranged to scan the back of the subject's body as the subject <NUM> stands in the imaging region. The first radiation provider and the first radiation detector may be provided by transmitting and receiving antennae that are tuned to receive and transmit the first radiation type, for example mm-wave antennae. The first scanner <NUM> shown in <FIG> comprises an elongate linear array of such transmitting and receiving antennae. The front view part <NUM>-<NUM> may comprise one such linear array provided in front of the subject's body to provide a front view, while the rear view part <NUM>-<NUM> may be provided by another such array behind the subject's body.

In the arrangement illustrated in <FIG>, each array spans the height of the subject's body, from the floor of the imaging region to at least the height of the subject's head. In <FIG> each linear array is arranged in a straight vertical line. It can be seen in <FIG> that these arrays of the first scanner <NUM> define an imaging plane. Relative movement of this imaging plane with respect to the subject <NUM> can enable the subject's body to be scanned with the first radiation type. The first scanner <NUM> is thereby arranged so that first scan data can be collected from most, for example, all areas of the subject's body in the imaging region. This can enable first image data, showing these areas of the subject's body, to be reconstructed from the scan data.

As mentioned above, the first radiation provider may comprise a plurality of sources of the first radiation type and these sources may be spaced apart to provide an array. As mentioned, they may be arranged in a linear array, which may be at least partially upright. In contrast to the second radiation type, this array may be arranged to deliver the first radiation type in an even distribution of energy density across the imaging region. For example the energy density of the first radiation type may be distributed in a manner that is at least partially homogeneous for example completely homogeneous.

The first scanner <NUM> comprises a first radiation detector arranged to detect radiation after it has interacted with, for example been reflected, by the subject's body. It will be appreciated in the context of the present disclosure that the spatial and/or temporal distribution of signal intensity of this scattered radiation can be used to scan the subject's body. Image data is obtained based on the scan data. This need not comprise the scan data being reconstructed into an image in the conventional sense that a human operator might recognise - for example features of the scan data (for example signal intensity or Fourier domain features) may be used instead without the need to reconstruct a complete image. The scan data may of course however be used to assemble an image of the subject's body. Such images may be three dimensional. One way to achieve this is to use synthetic aperture reconstruction. Other image reconstruction techniques will be apparent to the skilled person in the context of the present disclosure.

<FIG> also shows a second scanner that comprises a second radiation provider and a second radiation detector. As noted above, the second scanner <NUM> is arranged slightly differently from the first scanner <NUM> in that its radiation provider <NUM>-<NUM> and radiation detector <NUM>-<NUM> are separated from each other by the imaging region. This enables it to generate a transmission image of the subject <NUM> - for example tissue penetrating radiation can be passed through the subject <NUM> to obtain an image of the subject <NUM>. This image may indicate spatial variations in density, or transmissivity, of the subject <NUM>. For example it may comprise a transmission X-ray image.

<FIG> illustrates an arrangement in which the second radiation provider <NUM>-<NUM> is arranged to illuminate the subject <NUM> with a thin fan beam of tissue penetrating radiation. The second radiation detector <NUM>-<NUM> comprises a line of detectors on the other side of the imaging region from the second radiation provider <NUM>-<NUM>. This can enable an image of the subject's body to be assembled based on the transmission of the fan beam of radiation through the subject's body. It can be seen in <FIG> that the fan beam of the second type of radiation may be collimated so that it is of tightly constrained horizontal width (transverse to the beam direction) but fans out vertically. Generally the horizontal width of this beam is less than <NUM>, for example less than <NUM>. The width of the beam is selected so that the spread of the beam at the detector matches the width of the detector.

The plane of illumination defined by this fan beam, and the detector line of the second radiation detector may be offset from the imaging plane of the first scanner <NUM>. For example the two imaging planes may be offset (spaced apart) in a direction that is transverse to both planes. The first scanner <NUM> may thereby be arranged so that it does not obstruct the line of sight between the second radiation source and the second radiation detector.

In the example illustrated in <FIG>, the radiation provider of this second scanner <NUM> is arranged to illuminate only a selected part (i.e. less than all) of the imaging region. The selected part is arranged to correspond to the position of the torso of an upright human adult <NUM> standing in the imaging region. The selected part may have a vertical extent of between <NUM> and <NUM>, for example between <NUM> and <NUM> in the imaging region. For example it may extend about <NUM> upward from a point at the bottom of the subject's abdomen. For example the lower edge of the illuminated area may be selected to be at least lower than the subject's anal canal, and at least higher than a midpoint of their thighs, for example at least higher than their knees. For example, embodiments of the disclosure may be configured to obtain an image of the subject using the first scanner and to adjust the field of view of the second scanner based on the image of the body obtained using the first scanner.

In the example illustrated in <FIG> the second radiation provider <NUM>-<NUM> comprises an X-ray fan beam provider. The second radiation provider <NUM>-<NUM> is arranged so that the second radiation type illuminates this selected part of the imaging region in more strongly than other parts of the imaging region. For example, the field illuminated by the fan beam may be restricted to this selected area. Other parts of the imaging region may be shielded from the second radiation type. This may be accomplished by directing the fan beam only at this area and/or by attenuating the second type of radiation that might otherwise reach parts of the imaging region. For example a radio opaque shield may be arranged to shield other parts of the imaging region from direct exposure to radiation from the second radiation provider.

<FIG> illustrates a side view of an apparatus in which the first scanner <NUM> comprises an array <NUM>-<NUM> that is arranged for inspection of upward facing surfaces and another <NUM>-<NUM> that is arranged for the inspection of downward facing surfaces of the subject's body. For example, the array(s) of front view system and/or back view system may comprise one or more horizontal arrays. As shown in <FIG>, one such horizontal array may be arranged for imaging the bottom of the subject's feet. As illustrated in <FIG> a horizontal array may be arranged for imaging upward facing surfaces of the subject's body such as the top of their head. In the example of <FIG> the upright and horizontal parts of the arrays are shown as being perpendicular, but this is merely an example. They may also comprise one or more arrays arranged in a non-upright, nonhorizontal orientation. The arrays may also be curved.

Accordingly, in embodiments such as those described above with reference to <FIG>, the first type of radiation may be directed towards the subject <NUM> from a plurality of spatial positions that are distributed around the imaging region. The first scanner <NUM> itself may be scanned across the subject's body. In some possibilities it may also be scanned in a trajectory that surrounds the subject's body, for example along a circular scan path, while the subject <NUM> remains stationary. It will also be appreciated however that the subject <NUM> can be moved while the imagers remain stationary. One way to achieve this is to provide a moving support surface for the subject <NUM> to stand on, such as a conveyor or rotatable turntable. Accordingly, in some embodiments the apparatus comprises a moving support surface that is arranged to move the subject <NUM> relative to the fan beam of the second radiation type and relative to the field of view of the first scanner <NUM>.

It will be appreciated in the context of the present disclosure that a subject may be scanned to obtain image data (e.g. data from which an image could be reconstructed) without the need to reconstruct that image for display to a human operator. For example spatial frequency data, texture data, or other image parameters may be derived from image data obtained from a scan and used to detect objects. In other words - information about the subject may be inferred from the scan without the need to reconstruct a human interpretable image.

It will also be appreciated that <FIG> is described in terms of an active imager e.g. it comprises its own radiation provider. <FIG> shows a first scanner which includes two parts, front <NUM>-<NUM> and rear <NUM>-<NUM>, only one such part is needed, but in some cases more parts may be used - for example further parts may be arranged for imaging the sides, upper and lower facing surfaces of the subject.

<FIG> shows a scanning apparatus comprising a first scanner <NUM>, a second scanner <NUM>, a controller <NUM>, and an operator interface <NUM>. The first scanner <NUM> and the second scanner <NUM> are coupled to a movable support structure <NUM> which holds them at selected positions for scanning an imaging region which can be occupied by a human subject <NUM>. Each of the first scanner and the second scanner may comprise imaging hardware and/or software adapted to provide image data based on the scan data acquired from scanning the subject.

The controller <NUM> is coupled to the first scanner <NUM> and the second scanner <NUM>, and to the operator interface <NUM>.

The operator interface <NUM> comprises a display for showing images and for communicating information to a human operator. It may also comprise a human input interface for allowing the operator to provide commands to the controller <NUM>, for example for controlling the display and/or first scanner <NUM> and the second scanner <NUM>.

The controller <NUM> comprises processing logic adapted for processing signals from the imagers to reconstruct images, and for manipulating the images for display by the operator interface <NUM>. The controller <NUM> also comprises a machine readable data store <NUM>.

The data store <NUM> may be configured to store position data based on the position of the first scanner <NUM> relative to the second scanner. The position data may comprise a transformation, such as an affine transform, adapted for transforming image data based on the scan acquired by the first scanner <NUM> and image data based on the scan acquired by the second scanner into a common frame of reference - for example this transformation may be configured to co-register the two types of image data.

The data store <NUM> may also be configured to store comparator data, such as comparator scan data and comparator image data - for example scan or image signatures associated with the presence of concealed objects. For each image signature, the comparator data may comprise comparator data for the first image type (surface images) and comparator data for the second image type (transmission images). Image signatures in the first image type may comprise things such as image data associated with phase lines, image data associated with a flat surface, image data associated with a straight edge, image data associated with an angular feature, and image data associated with one or more different types of non-tissue objects. Image signatures in the second image type may comprise thresholds of transmissivity, for example an image density threshold associated with a plastic or metal object, for example geometric shapes. The comparator data may also comprise expected anatomical data. Embodiments of the disclosure may be configured to compare image data obtained from a subject with the comparator data to detect anomalies, and to trigger an alert in the event based on this comparison.

The first scanner <NUM> comprises a front view system and a back view system having the features described above with reference to <FIG>. Likewise, the second scanner comprises a second radiation provider and a second radiation detector. The second radiation provider and the second radiation detector are separated from each other by an imaging region in which a human subject <NUM> can be placed. The second scanner is adapted for scanning the subject's torso as explained above. Also as described above, the first scanner <NUM> is adapted for providing images of the surface of most of the subject's body. As explained above, the first source of radiation comprises non-ionising radiation, and the second source of radiation comprises tissue penetrating radiation.

In operation, a human subject <NUM> stands in the imaging region, and the controller <NUM> controls the movable support structure <NUM> to move the first scanner <NUM> and the second scanner <NUM> to scan the subject <NUM> with the first type of radiation and the second type of radiation.

The first scanner <NUM> then provides the first image data to the controller <NUM>. The first image data comprises a front view of the subject <NUM> and a back view of the subject <NUM> each view showing surfaces, such as soft tissue and concealed objects, hidden by the subject's clothing. The second scanner <NUM> also provides the second image data which shows an image based on the transmissivity of the subject's torso, as explained above. This may exclude at least one of a head and a limb of the subject. The first image data however shows the torso of the subject and at least one of their head and one of their limbs. The second scanner may obtain the second image data simultaneously with the first scanner, or at another time, for example before or after the first image data is obtained.

The controller <NUM> then takes this image data and applies the transformation based on the relative positions of the first scanner <NUM> and the second scanner <NUM> to co-register the front view and/or the second view of the subject's body surfaces with the transmission image of their torso.

The controller <NUM> can then provide a composite image based on the two different types of image data for display by the operator interface <NUM>. This composite image may comprise a side-by-side display of the different image types - for example the first image data (the subject shown head to foot) may be displayed adjacent to the second image data showing their torso. As a result of the co-registration the vertical height of the torso image may be adjusted so that the two images can be easily compared by the operator.

The controller <NUM> can also then compare at least one of the first image data and the second image data with the stored comparator data for that image type. These comparisons may be performed according to a pattern matching algorithm.

In the event that a feature in the first or second image data matches one of the stored items of comparator data, or indicates an anomaly from a normal reference (such as anatomical reference data) the controller <NUM> may be configured to indicate that a closer inspection should be performed. This may be done by triggering an audible or visible alert. This visible alert may comprise indicating the location of a corresponding region in the other of the first or second image data, for example by highlighting that region, for example by providing a boundary around it on the display of the operator interface <NUM>.

The controller <NUM> may also be configured to overlay the first image data and the second image data. This may be done by making at least one of the two types of image appear to be at least partially transparent. Different overlays can be provided. For example the front view can be overlaid with the transmission image, and the back view can be overlaid with the transmission image. The controller <NUM> may be configured to display a sequence of different images. For example one of the front view and the back view may be displayed, followed by a display of the transmission image at the same spatial location on the display. This may help the operator to visually identify regions of the transmission image which show unusually high density due to some kind of surface feature, such as an object which may be concealed beneath the subject's clothing. The different overlays may also be interleaved in this sequence. The sequence may be predetermined, or the controller <NUM> and operator interface <NUM> may be configured to allow an operator to select which image to show next at the same spatial location on the display.

The first radiation provider comprises a source of non-ionising radiation. A suitable wave length range of the non ionising radiation is from <NUM> to 500THz, for example between <NUM> and <NUM>, for example between <NUM> and 400THz, for example mm-wave radiation from <NUM> to <NUM>, and also <NUM>, also <NUM> and higher, for example the J/K bands. Infrared radiation in the frequency range of <NUM> to <NUM> THz may also be used.

The second radiation provider may comprise a generator of tissue penetrating radiation such as a linear accelerator or microwave excited X-ray source. The energy of the tissue penetrating radiation may be in the range of 50keV to 160keV. For example, to provide an energy range of 50keV to 160keV a tube based X-ray generator may be used, such as in the B-SCAN 16HR-LD range of transmission X-ray scanners, which are available from Smiths Group plc. <NUM> Park Avenue, Bushey, Watford, Hertfordshire, WD23 2BW. In some embodiments the second radiation provider may comprise a dual band X-ray source. In some embodiments the second radiation provider comprises a passive source of tissue penetrating radiation such as a radioactive isotope that provides a gamma ray source. The second radiation provider may for example comprise a wave guide for obtaining radiation from such a radiation source and a collimator for providing a beam of radiation for illuminating the subject's torso. The second radiation provider therefore need not actually comprise the source of radiation itself - it need only be able to direct the second type of radiation in the manner needed to provide transmission images as described above. The generator may be made and sold separately.

In some embodiments the tissue penetrating radiation may be non-ionising. For example radio frequency radiation may be used. In these embodiments NMR based techniques may be used to scan the subject. Such techniques could involve the application of a magnetic field to the body, or may be based on low field NMR/MRI techniques.

With reference to the drawings in general, it will be appreciated that schematic functional block diagrams are used to indicate functionality of systems and apparatus described herein. It will be appreciated however that the functionality need not be divided in this way, and should not be taken to imply any particular structure of hardware other than that described and claimed below. The function of one or more of the elements shown in the drawings may be further subdivided, and/or distributed throughout apparatus of the disclosure. In some embodiments the function of one or more elements shown in the drawings may be integrated into a single functional unit.

In some examples, one or more memory elements can store data and/or program instructions used to implement the operations described herein. Embodiments of the disclosure provide tangible, non-transitory storage media comprising program instructions operable to program a processor to perform any one or more of the methods described and/or claimed herein and/or to provide data processing apparatus as described and/or claimed herein.

The activities and apparatus outlined herein may be implemented with fixed logic such as assemblies of logic gates or programmable logic such as software and/or computer program instructions executed by a processor. Other kinds of programmable logic include programmable processors, programmable digital logic (e.g., a field programmable gate array (FPGA), an erasable programmable read only memory (EPROM), an electrically erasable programmable read only memory (EEPROM)), an application specific integrated circuit, ASIC, or any other kind of digital logic, software, code, electronic instructions, flash memory, optical disks, CD-ROMs, DVD ROMs, magnetic or optical cards, other types of machine-readable mediums suitable for storing electronic instructions, or any suitable combination thereof.

The above embodiments are to be understood as illustrative examples. Further embodiments are envisaged. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments.

The discussion above has mentioned the use of at least two linear arrays for the first scanner <NUM>, but it will be appreciated that three, four or more linear arrays may be used. These may provide more coverage of the person. e.g. front, back, top (head and shoulders) and bottom (e.g. under their feet). Multiple linear arrays may also be provided, and offset from each other to enable the person to be scanned as they stand still, and without moving the array. For example one or both of the front view imaging system and the back view system of the first scanner may comprise a 2D array. For example a phased array may be used to scan the back of the person and another phased array may be used to scan the front of the person. As will be appreciated in the context of the present disclosure, a phased array antenna may be composed of lots of radiating elements each phase shifted from the other. By control of the phase shift constructive/destructive interference effects can be used to steer the beam in the desired direction. Different patterns can be used to focus the beam on different voxels. Examples of systems suitable for use as a first scanner include the eqo (RTM) active millimetre-wave scanner available from Smiths Detection.

The second scanner <NUM> generally comprises a transmission X-ray scanner. Suitable classes of X-ray scanner include single energy transmission x-ray line scanner.

It has been explained above that in some circumstances, the torso scan configuration of this second scanner <NUM> is of particular utility. For example the lowest and or highest boundary of the field of illumination of the second radiation type may be adjustable to allow the height of the illuminated region to be adjusted.

It will be appreciated that a multiple view system may also be used. For example, more than one x-ray imager can be used to provide the second scanner. For example one full body view system, and a second torso view system, or <NUM> torso views at different angles to give more information about the subject, or about the shape of a concealed object. Viewing angles for these systems could be <NUM>° and <NUM>°.

The second scanner <NUM> may be configured to provide a fixed dose of the second radiation type per inspection. It may also be configured to provide a switchable/variable dose per inspection.

The second scanner <NUM> may also be positioned so that the subject can face the second radiation provider, or can face away from it.

It has been explained above that the imagers may remain stationary and the subject may be moved past the sensors. For example on a conveyor system. Alternatively, the person may stand still while they are scanned - either electronic scanning or mechanical scanning may be used. As will be appreciated in the context of the present disclosure electronic scanning may comprise controlling a phased array to electronically steer a beam.

The two imagers may also be used in combination with other, additional, sensors and identifiers for uniquely identifying the subject. These may comprise identifiers based on machine readable markers such as barcodes or identity cards. Biometric identifiers such as fingerprints may also be used. The apparatus may comprise a camera, such as a video camera to record the scan, or simply to capture a picture of the person who is being scanned.

It will also be appreciated by the skilled addressee in the context of the present disclosure that the operator of the apparatus may be present when the scan takes place - for example they may be in the same facility, for example in the same building, in the same room or an adjacent room. There could be one or more operators. The operator function could be combined - a single operator may both start the scan and evaluate the scan. In some embodiments the operator function could be split - a first operator may start the scan, and a second operator may evaluate the scan.

The system could produce results in a number of different ways. The system could produce static images from each of the sensors. e.g. a transmission x-ray image and front and back millimetre wave images. The system could produce a combined image using data from the transmission x-ray scan and the millimetre wave scan to produce a combined image. Images could be displayed side by side or stacked/layered. The system could provide a moving image / video of the person as they pass through the system or a collection of images from different views. The operator could mark an area on one of the images and the corresponding area would be marked on the other images to help the operator to evaluate the images.

A hybrid image could be provided to the operator to help them to evaluation the image. For example different colours could be used to show front, back and internal anomalies. The operator could be provided with software tool to assist them evaluating the images. For example by highlighting areas that have a high density. The system could use automatic detection software to provide results about the image - e.g. clear result or anomaly result. For example, the system may be configured to identify a symmetry property of a subject, for example differences between the left side and right side of their body and any deviations from such symmetry.

Alarms could be placed on the raw images or on a generic mannequin image.

Claim 1:
A method of scanning a clothed human subject (<NUM>), the method comprising:
obtaining first scan data using a first scanner (<NUM>) by illuminating the subject (<NUM>) with a first source of radiation adapted for scanning soft tissue surfaces hidden by the subject's clothing;
obtaining second scan data by illuminating the subject (<NUM>) with a second source of radiation that is directed more towards the subject's torso than towards other parts of their body, wherein the second source of radiation comprises tissue penetrating radiation;
obtaining first image data based on the first scan data and second image data based on the second scan data; and
indicating a body region shown in the second image data based on a feature of the first image data.