3D backscatter imaging system

Systems and methods for imaging an object using backscattered radiation are described. The imaging system comprises both a radiation source for irradiating an object that is rotationally movable about the object, and a detector for detecting backscattered radiation from the object that can be disposed on substantially the same side of the object as the source and which can be rotationally movable about the object. The detector can be separated into multiple detector segments with each segment having a single line of sight projection through the object and so detects radiation along that line of sight. Thus, each detector segment can isolate the desired component of the backscattered radiation. By moving independently of each other about the object, the source and detector can collect multiple images of the object at different angles of rotation and generate a three dimensional reconstruction of the object. Other embodiments are described.

FIELD

This application relates generally to systems for creating images. More particularly, this application relates to imaging systems that use radiography to detect scatter field components (including backscattering) and methods of using imaging systems.

BACKGROUND

In many industrial, military, security or medical applications, images of an internal structure of objects are required. Radiography is one type of technique that can be used for imaging. Radiography generally comprises either conventional transmission radiography or backscatter radiography. When access behind an object to be interrogated is not possible, only backscatter radiography is possible. One method of backscatter imaging is Compton Backscatter Imaging (CBI), which is based on Compton scattering.

Lateral migration radiography (LMR) is one type of imaging based on CBI that utilizes both multiple-scatter and single-scatter photons. LMR uses two pairs of detector with each pair having a detector that is uncollimated to predominantly image single-scatter photons and the other detector collimated to image predominantly multiple-scattered photons. This allows generation of two separate images, one containing primarily surface features and the other containing primarily subsurface features.

Recently, backscatter radiography by selective detection (RSD), a variant of LMR, has been used. RSD uses a combination of single-scatter and multiple-scatter photons from a projected area below a collimation plane to generate an image. As a result, the image has a combination of first-scatter and multiple-scatter components, offering an improved subsurface resolution of the image.

SUMMARY

This application relates to imaging systems that use radiography to detect scatter field components (including backscattering) and methods of using such imaging systems. The imaging system comprises a radiation source for irradiating an object, the radiation source movable about the object. The imaging system also contains a detector for detecting backscattered radiation from the object. The detector can be disposed on substantially the same side of the object as the source and the detector can be rotationally movable about the object. The radiation source and the detector can move independently of each other about the object, including in a rotational movement, collecting multiple images of the object at different angles of rotation. These multiple images can be used to generate a three dimensional reconstruction of the object.

The radiation source can comprise x-ray, gamma ray, neutron, an electron beam source, or combinations thereof. The beam of the radiation source can be a pencil beam, fan beam, cone beam, or a combination thereof. The detector may comprise a photostimuable phosphorous-based image plate, TFT-based flat panel detector, an amorphous silicon panel, a digitizing field screen, or a combination thereof. The detector (or detectors) can be separated into multiple detector segments (i.e., using a collimator grid) so that each segment has a single line of sight projection through the object and so only detects radiation along that line of sight. The restricted line of sight allows each detector segment to isolate the desired component of the backscattered radiation.

The imaging system can be used for single-sided, non-destructive imaging of any desired object in many different industries, including medical, military, security, and other industries. The imaging system can analyze a wide variety of objects, such as buried or otherwise unobservable objects suspected of containing a bomb (e.g. landmine), voids or imperfections in a material, luggage, cargo, integrated circuits, or other items.

The imaging system images the object using radiation from the source. When radiation is backscattered towards the detector, it can be received through the collimator grid and isolated to each detector segment. Each detector segment has a “field of view” of small area on the object of interest. By processing the data collected by each detector segment, an image of the object can be generated. The source and/or the detector can then be moved or rotated to a different orientation about the object, radiation is again directed to the object, and backscattered radiation is again detected by each detector segment. By processing the data again collected by the detector segment, another image of the object can be generated. To further enhance the image, the source and/or the detector can be moved multiple times to gather data from multiple orientations (i.e., up to 360°). The multiple data sets may also be used for reconstructing the data into a three-dimensional image.

The Figures illustrate specific aspects of the imaging systems and methods for using the imaging systems. Together with the following description, the Figures demonstrate and explain the principles of the structures, methods, and principles described herein. In the drawings, the thickness and size of components may be exaggerated or otherwise modified for clarity. The same reference numerals in different drawings represent the same element, and thus their descriptions will not be repeated. Furthermore, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the described devices. Moreover, the Figures may show simplified or partial views, and the dimensions of elements in the Figures may be exaggerated or otherwise not in proportion for clarity.

DETAILED DESCRIPTION

The following description supplies specific details in order to provide a thorough understanding. Nevertheless, the skilled artisan will understand that the described imaging system and associated methods of making and using the system can be implemented and used without employing these specific details. Indeed, the imaging system and associated methods can be placed into practice by modifying the described systems and methods and can be used in conjunction with any other apparatus and techniques conventionally used in the industry. For example, while the description below focuses on using the imaging system for x-rays, it could be used for other types of radiations, such as gamma rays, neutrons, electron beams, or combinations thereof.

As the terms on, attached to, or coupled to are used herein, one object (e.g., a material, a layer, a substrate, etc.) can be on, attached to, or coupled to another object regardless of whether the one object is directly on, attached, or coupled to the other object or there are one or more intervening objects between the one object and the other object. Also, directions (e.g., above, below, top, bottom, side, up, down, under, over, upper, lower, horizontal, vertical, “x,” “y,” “z,” etc.), if provided, are relative and provided solely by way of example and for ease of illustration and discussion and not by way of limitation. In addition, where reference is made to a list of elements (e.g., elements a, b, c), such reference is intended to include any one of the listed elements by itself, any combination of less than all of the listed elements, and/or a combination of all of the listed elements.

Some embodiments of the imaging systems and methods for using the imaging systems are shown in the Figures.FIG. 1illustrates one imaging system which can be used for detecting backscattered radiation. As used herein, backscatter includes any scattering radiation occurring away from the surface of the irradiated object or material.

The system5contains a source of radiation10. The radiation source (or source)10can be any source (or sources) of radiation that penetrates the desired object (or objects), including an x-ray source, a gamma ray source, a neutron source, an electron beam source, or combinations thereof. The source10irradiates the desired object area (including the object itself) using the desired type of radiation to a desired depth.

In some embodiments, the amount of radiation (or intensity) from the source10can be controlled and customized for a specific object. For example, the radiation source10can be controlled to provide a photon illumination (energy) spectrum with an average depth in the object to obtain the detail need to create an image. In another example, the radiation intensity provided by radiation source10can be sufficiently low so as to not saturate the detector12(described below).

As shown inFIG. 1, the radiation source10transmits radiation26which partially or completely penetrates the surface of a material22that is part of an object or object area to be analyzed. The radiation26strikes internal portions of the material22, such as cracks20, voids18, or hidden objects in the material22. Those internal portions in the material22then backscatter a portion of the radiation26as backscattered radiation28. In some configurations, the radiation source10is also capable of independent motion in different directions including rotation, in-and-out movement of the radiation source10from the object region, and angular movement. The radiation source10can be adjusted to select or focus on the object that is being analyzed or scanner by the beam13of radiation26. Alternatively, the radiation source can be stationary and the object can be movable.

The beam13from the radiation source10can be configured to be any type of known beam. In some configurations, the beam can be configured as a pencil beam, fan beam, cone beam, or combinations thereof. In some instances, a fan beam or cone beam can be used since they can create a higher intensity backscatter field and have a larger field of view than a pencil beam, thereby saving time due to the simultaneous collection from a larger field of view. The width and/or length of the fan and/or cone beam can be adjusted to enhance the resolution of the image.

Where a fan beam is used, it can be configured by utilizing an aperture. In these embodiments, the beam of radiation can be passed through the aperture such that the output from the aperture is a fan beam of radiation. These embodiments can increase the analysis speed by radiating a line of the object, instead of only a spot radiated by a pencil beam, and by using the fan beam to create a higher intensity backscatter field.

The system5also contains a detector12. The detector12can be any detector (or detectors) of radiation that can detect the radiation scattered from the object. In some embodiments, the detector can include an x-ray detector, a gamma ray detector, a neutron detector, an electron beam detector, or combinations thereof. In other embodiments, the detector12can comprise NaI scintillator crystals, plastic scintillators, photostimuable phosphorous-based image plates, TFT-based flat panel detectors, amorphous silicon panels, or combinations thereof. For example, for x-ray radiography on a large area image, a photostimuable phosphor-based imaging plate and/or an amorphous silicon panel (ASP) conversion screen bonded to an array of photosensitive diodes.

The detector(s) can be separated into multiple detector segments that each detects radiation along a single path or line of sight. This separation can be accomplished using any mechanism that isolates each segment so that it only receives radiation along that path. For example, in the embodiments depicted inFIG. 1, the detector12comprises a collimator14coupled to the detector12and so is referred to as a collimated detector15. The collimator contains multiple detector segments within each grid of the collimator. In the embodiments depicted inFIG. 1, the radiation source10and the collimated detector15can be disposed on the same side of the object region to be analyzed. The radiation source10can generate photons that are directed toward the object region. The collimated detector15collects photons that are backscattered from the surfaces of the object and from objects hidden or voids beneath the surfaces. The collimated detector not only detects the backscattered radiation, but also assists in generating three-dimensional images of the object area, including hidden objects and/or voids.

The collimator14can include any of a variety of cross sectional areas, including a cylindrical, elliptical (non-circular), or rectangular. In some embodiments, the collimator14and the detector12have the shape so that any or all of the backscattered radiation that travels through the collimator14is detected. The collimator14may include any number of collimator features with various geometries including fins, slates, screens, and/or plates that may be curvilinear or flat. In some embodiments, the collimator14(and such features) can be formed from any known radiation absorbing material, such as lead. In other embodiments, the collimator14(and such features) can be formed from radiation reflective material, such as high density plastic, aluminum, or combinations thereof. These latter embodiments are helpful when enhancement, rather than removal, of certain backscatter radiation is desired. In some configurations, the collimator features can be oriented substantially perpendicular to the surface of the detector12. In other configurations, the collimator features can be given any orientation relative to the detector12that provides the desired line of sight radiation for each segment.

In some configurations, the separation of the detector using the collimator can create apertures16. Backscattered radiation from the object reaches the detector12through the apertures16if the backscatter direction is substantially parallel to the collimator features or has a narrow enough angle to travel through the aperture without being absorbed by the collimator feature. The collimator features can be modified to allow for a wider aperture to allow in more backscattered radiation or a narrower aperture to decrease the backscattered radiation from the object.

In some embodiments, the collimator14may be adjustable to alter the direction of the backscattered radiation which can reach the detector. In these embodiments, the position and/or orientation of the collimator features can be modified to change the position and/or orientation by manual mechanisms or by automatic mechanisms, such as through computer controlled motor drives.

The collimator14can be coupled to the detector using any known technique. In some embodiments, the collimator14can be optically coupled to the detector12so that radiation passing by the collimator14reaches the detector12and is measured, creating a collimated detector15. In other embodiments, the collimator14can be physically attached to the detector12.

The collimated detector15can move in different directions including rotation, in-and-out movement from the object region, and angular movement. In some configurations, the collimator14can move in different directions relative to the detector, including rotation, in-and-out movement, and angular movement. These movements can focus the image by selecting and/or isolating the desired backscattered radiation. In other words, adjusting the collimated detector15allows the user to select and isolate particular vectors of backscattered radiation to travel through the aperture16and be detected by the detector12. Alternatively, the collimated detector can be stationary and the object movable.

In some embodiments, the radiation source10and the collimated detector15may be attached to a moving structure (such as plate24), as shown inFIG. 1. The plate24has a movement axis that is substantially perpendicular to the object. In some embodiments, this movement axis is a rotational axis and so the plate24is a rotational plate. (Such rotational axis is shown as axis35inFIG. 2a.) The radiation source10and collimated detector15may be attached to the plate24as known in the art, such as poles17extending from the rotating plate24. The radiation source10and collimated detector15may be located at any location along the plate24and this location can be fixed or altered as desired. This configuration allows both the collimated detector15to detect backscatter and the source10to irradiate the object from any location along the plate24.

In these embodiments, the rotational axis of the plate24allows the source10and collimated detector15to be rotated about the object region while maintaining a similar distance and orientation from the object. Independent adjustments can be made to the source10and collimated detector15to change the distance and orientation from the object, if needed. In some configurations, the plate24may comprise a single plate so the source10and the collimated detector15remain at about an 180° angle relative each other. In other configurations, the plate24may be two plates, attached or separate, to allow the radiation source10and collimated detector15to be rotated independently and oriented at any desired angle relative to each other. For example, the radiation source10may remain in a fixed position while the collimated detector15can be rotated to create various angles of orientation relative to the source10.

In some embodiments, the system5can be contained in a protective and supportive housing which can be made from any known flexible and/or known lightweight materials. The housing holds the various components of the system5in place. Lightweight housing materials facilitate portability of the system, which can be advantageous in certain applications. Using such materials also allows the housing to be manufactured in a variety of desired shapes and allows the system to be relatively lightweight to make it easy to transport. In some embodiments, the system5can be configured as a compact system so that it is readily transportable and adopted to work within confined spaces.

In some embodiments, the system105can be used to detect backscattered radiation, as shown inFIG. 2a. In this Figure, a radiation source30transmits radiation40which penetrates the surface of a material36and strikes internal details such as voids42and44, hidden objects, and/or cracks (not shown) in the material36. These internal details in the material36then backscatter a portion of the transmitted radiation41. The backscatter41can pass through a collimator34and be detected by the detector32.

In these embodiments, the radiation source30can generate photons that are directed toward an object (including object region38) and the collimated detector33collects photons that are backscattered from the scanned surface and from the internal details beneath the scanned surface. The object region38can be shifted by independent adjustments to the radiation source30or by changing the location of the radiation source30along a rotating plate37. For example, adjustments can be made to the object region38by changing the distance from the radiation source30to the object region38, which will shrink or enlarge amount of the object region38being irradiated. Further, the object region38can be shifted by changing the angle of the radiation source30with respect to the object region38.

In these embodiments, the beam from the radiation source30may be a pencil beam, a fan beam, or a cone beam. With a cone beam it is possible to scan the entire object region38without the need to move or modify the radiation source30. The cone beam may also be moved to increase or decrease the size of the object region. When using a pencil beam or fan beam, it can scan a specific part of the object region38. The imaging system105can use any scanning design, including raster scanning, to create a desired object region38. The object region38can be a variety of cross sectional areas, including cylindrical, elliptical (non-circular), or rectangular (includes square). As explained in further detail below, data gathered from multiple orientations of the radiation source30and collimated detector33should be of approximately the same object region38.

The configuration of the radiation source30and the collimated detector33allow the acquisition of multiple sets of data or images from the object region38. Therefore, it is possible to obtain multiple images of the same object region38from different orientations between the radiation source30and the collimated detector33. In some embodiments, the orientation between the source30and the collimated detector33can range from about 1° up to about 359° relative to each other. For example, an image of an object region38may be collected when the radiation source30and the collimated detector33are initially at a 180° angle with respect to each other, and thereafter the radiation source30can be rotated in 10° increments around the object region38, collecting an image at each location. The subsequent application of a computer model on these multiple images will allow a three-dimensional reconstruction of the object region38.

As shown inFIG. 2a, multiple images46,48,50, and52can be taken from various configurations of the radiation source30and the collimated detector33. AlthoughFIG. 2adepicts four images, any number of images could be used to obtain a three-dimensional reconstruction. In some embodiments, the number of images can range from 2 (with appropriate constraints) to any desired number. In other embodiments, the number of images can range from 3 or 4 to 10 or 15. Of course, the more images that are taken, the better the resolution of the 3D reconstruction.

Image46can be obtained by data collected from the configuration of the source30and collimated detector33depicted inFIG. 2a. The voids42and44found in the material36can be depicted in image46as two-dimensional objects42aand44a. Image48can be obtained by rotating the radiation source30and/or the collimated detector33by the desired amount and collecting additional data to depict the voids42and44as two-dimensional objects42band44b. To obtain image48, the radiation source30and collimated detector33were both rotated 90° about the object region38in the same direction (e.g. remaining at a 180° angle with respect to each other). Image50can be obtained by rotating both the radiation source30and collimated detector33another 90° about the object region38in the same direction depicting the voids42and44as two-dimensional objects42cand44c. In some configurations, the configuration used to generate image50could be the mirror image of the configuration shown inFIG. 2a, having the radiation source30located on the right side of the system and the collimated detector located on the left side of the system. Image52is obtained by again rotating the radiation source30and collimated detector33another 90° about the object region38in the same direction depicting the voids42and44as two-dimensional objects42dand44d.

Rotation about the object region38can be accomplished by rotating plate37around rotational axis35that is oriented substantially perpendicular to the material36. In these embodiments, the plate37may be a single plate that rotates the radiation source30and collimated detector33at the same rotational distance from each other (i.e. the radiation source30and collimated detector33remain 180° from each other). In other embodiments, the plate37may be two plates, attached or separate, that allow the radiation source30and collimated detector33to rotate at different rotational distances with respect to each other. Rotation about the object region can also be accomplished by keeping the radiation source30and collimated detector33stationary and rotating the object region38.

FIG. 2bdepicts a three-dimensional (3D) structure of the object region38and voids42and44using the images46,48,50, and52. This 3D structure can be obtained using the reconstruction method described herein. The reconstruction method can be used to supply a three-dimensional structure of any desired feature of the material36, including voids, cracks, corrosion, delaminations, or other hidden objects.

The mathematical formulation, which gives rise to a forward or generative model, for use in reconstruction is as follows. The formulation only considers photons returning to the detector from a single backscatter rather than multiple scattering events. The collimated detector establishes a set of apertures each of which has an associated line of sight. Incident photons move along the associated line of sight, which is a three-dimensional space defined by the location and orientation of the aperture.

FIG. 3shows the simulation details for an embodiment of the reconstruction method. The region of space61to be imaged is called the object region. The position along collimated line72a distance s from the detector segment63is referred to as d(s). Line68connects d(s) with source60. The position along the line68a distance t from the radiation source is referred to as e(s,t). The distance from d(s) to the radiation source60is referred to as f.

The expression for the number of photons, or signal intensity, reaching the detector segment63from backscatter at d(s) can include four terms: (A) the number of photons radiated from the radiation source60, (B) the loss of intensity traveling along line68from the radiation source60as it passes through a material in the object region to reach d(s), (C) the fraction of that intensity that is scattered along line72, and (D) the loss of intensity as the backscattered photons travel along line72to the detector. The cumulative effects of terms A, B, C, and D are multiplicative and thus the mathematical expression for the intensity reaching the detector along a single path i, from a backscatter at a distance s is:
Ei(s)=A×B×C×D=E0e−∫0fρ(ei(t,s))dtγ(θi(s))ρ(di(s))e−∫soρ(di(q))dq;  (1)
where E0is the intensity of the radiation source60, ρ(x) is the material density as a function of the position x in the object region, θi(s) is the angle formed by the two lines68and72, and γ(θi(s)) is the differential scattering cross section as a function of the angle at which the two lines meet. In order to model the effects of Compton scattering γ(θi(s)) can be set equal to cos2(θ). Alternatively, other models of the scattering can be used and substituted into equation (1).

The total intensity traveling along path i is the integral of all the backscatter events along the line72. This is:
Ei=∫0∞Ei(s)ds=E0∫0∞e−∫0fρ(ei(t,s))dtγ(θi(s))ρ(di(s))e−∫s0ρ(di(q))dqds,(2)
where, in practice, the integral along d(s) ends at the effective boundaries of the object region (i.e. no material or signal becomes insignificant).

The basic form of equations 1 and 2, unlike conventional tomography or tomosynthesis, does not lend itself to an easy decomposition into linear expressions of ρ, the image density. Rather there is a nonlinear mixture of terms—a combination of the multiplicative effect of the backscattering term with the exponential terms that model the intensity loss and the composition of backscattering along the line of sight, represented as the outermost integral in Equation 2.

For reconstruction the term A=E0can be treated as a constant and absorbed into the detector units. The constant can be estimated globally or measured separately before imaging. The form for Equation 2 in terms of the integral along the detector segment line of sight and the image density therefore becomes:

EiE0=∫0∞⁢Bi⁡(ρ,s)⁢Ci⁡(s)⁢ρ⁡(di⁡(s))⁢Di⁡(ρ,s)⁢ⅆs,(3)
where the functions Biand Diare nonlinear functions of ρ. By treating the nonlinear interactions as secondary and using a fixed estimate for ρ, denoted as, the equation becomes:

Mi=EiE0=∫0∞⁢Bi⁡(ρ,s)⁢Ci⁡(s)⁢ρ⁡(di⁡(s))⁢Di⁡(ρ,s)⁢ⅆs=∫0∞⁢wi⁡(s)⁢ρ⁢(di⁡(s)),(4)
where the terms that do not depend explicitly on ρ into wi(s) are combined. The result is a linear operator, and thus, an expression for the image formulation that is of the same form as a conventional x-ray formation—and, by analogy, tomographic reconstruction.

Considering the discrete form of Equation 4, the approximation of ρ on a grid or individual detector segment is denoted as Rk, the value of ρ at a grid location is denoted as Xk, and the number of projection images collected as N. The discrete reconstruction Rkis designed to optimize the total difference between the measured detector intensities and those simulated from applying the imaging model to the discrete reconstruction, Rk. As shown in equation (4), the function wi(s) can be captured as a set of weights Wijthat measures the relationship between the fixed estimated, the solution on the grid Rkwhere the backscatter occurs, and the corresponding line integrals from the radiation source60and detector segment63to the point. Then the reconstruction is formulated as:

R=argmaxR⁢∑j=1N⁢(∑i=1M⁢Wij⁢Rj-Mi)2,(5)
where, M is the number of grid points (e.g., detector segments) in the reconstruction, and R represents the entire collection of grid points in the solution. R represents the object that is to be reconstructed and M represents the projection data collected. The weights Wijcan be computed in a manner that is similar to conventional computer tomography, that is, by using a linear interpolation (e.g. trilinear in 3D) and using the geometric relationships between the grid and the line integral to establish this linear dependence for each pair of points on the detector and the reconstruction grid.

The least squares problem in Equation 5 can be solved as an over-constrained linear system. The linear system in Equation 5 can be solved in a variety of ways including standard numerical relaxation (linear system) methods and conventional iterative methods such as the algebraic reconstruction technique (ART) or simultaneous algebraic reconstruction technique (SART). If SART is used, the algorithm formulates the reconstruction problem as finding an array of unknown variables using algebraic equations from the projection data. It is an iterative reconstruction algorithm, which has the advantage of robustness to noise and incomplete projection data. As the ART and SART algorithms, and variations thereof, are known to one of skill in the art, they will not be described further.

Due to the nature of the formulation and underlying physicscan be treated as fixed. Because the integrals in Equation (4) average (or smooth) the effects of the material properties between source-detector and position of the backscatter, and thus, aggregate material properties along the rays is sufficient to obtain some level of accuracy in the reconstruction.

The accuracy results depend on the accuracy of the models of the intensity loss that takes places as radiation moves to and from the point of backscatter. Iterative reconstruction can be used, denoting as a sequence of solutions R0,R1,R2, . . . , and a sequence of discrete estimates of the solution used to model intensity loss {circumflex over (R)}0,{circumflex over (R)}1,{circumflex over (R)}2, . . . . This gives a sequence of weights in the linear system, Wlij. In implementation, the estimates ofsimply lag in the formulation. In this wayl=Rl-1and Wlcan be computed from the intensity loss estimated from the previous solution and they change with each subsequent iteration. Such schemes can be effective for nonlinear optimization problem (i.e., let the nonlinear terms lag).

Some embodiments pertain to a method and apparatus for a single-sided, non-destructive imaging technique utilizing the penetrating power of radiation to image subsurface and surface features. These embodiments can be used for a variety of applications including non-destructive examination, medical imaging, military, and security purposes.

Implementation of the reconstruction algorithms can be conveniently performed using various means for reconstruction. In some embodiments, a conventional processing system (such as, for example, a computer) can provide a means for reconstruction using computer tomography. In particular, the algorithms can be implemented in software for execution on one or more general purpose or specialized processor(s). The software can be compiled or interpreted to produce machine executable instructions that are executed by the processor(s). The processor can accept as inputs any of the following:a. Orientation/position of the object relative to the sourceb. Orientation/position of the object relative to the detectorc. Output signal (array of signals) from the detector

If desired, the processor can also control the relative positioning of the object relative to the source and detector. Thus, the processor can output any of the following:a. Rotational control for the objectb. Linear positioning control for the sourcec. Linear positioning control for the detector

FIG. 4illustrates an example of a system for backscatter imaging. The system400can include a computer subsystem402(which can, for example, be a personal computer, workstation, web server, or the like). The computer system can be of conventional design, including a processor, memory (data storage and program storage), and input/output. The computer system can include a display (e.g., for displaying reconstructed images) and human input devices (e.g., keyboard, mouse, tablet, etc.). The computer system can interface to a radiation source404, to and provide control information406to the radiation source. For example, control information can provide for turning on/off the radiation output of the source and setting the source output intensity. The system can include mechanical means (e.g., as described above) for moving the source, in which case the control information can also control the position/orientation of the source.

The system400can also include a detector408which can provide measurements410of detected backscattered radiation to the computer system402. For example, the measurements can be digital data provided from the detector. As another example, the measurements can be analog data, and can be converted (e.g., using an analog to digital converter) into digital form before processing. The system can include mechanical means (e.g., as described above) for moving the detector, in which case control information412can be provided from the computer system to the detector to control the position/orientation of the detector.

The computer system402can be programmed to implement reconstruction techniques (e.g., as described above) to combine data from multiple two-dimensional slices of detected backscattered radiation410to form a three-dimensional reconstructed image. The three-dimensional reconstructed image can be output for display, stored in a memory for later use, or transmitted via a communications link (e.g., the Internet) to another location for display or storage.

If desired, the system400can also include means for moving the object to be imaged (e.g., as described above) in which case the computer system402can provide control output414for controlling the position/orientation of the object.

Applications of embodiments of the present invention include, but are not limited to scanner/imaging systems for detecting flaws and defects in materials and structures, scanners for detecting target objects and/or foreign object debris inside of walls and structures, devices for security purposes to identify objects hidden in walls, containers or on individuals, portal scanning, law enforcement and other security applications, and medical imaging.