CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of U.S. Provisional Patent Application Serial. No. 62/332,249, filed on May 5, 2016, the disclosure of which is incorporated herein by this reference in its entirety.

BACKGROUND

[0002] The present disclosure relates generally to devices, systems, and methods for generating high-resolution tomosynthesis-based images of internal tissues using x- rays.

[0003] Prostate cancer is a common disease in the male population, diagnosed in the United States in 1 in 7 men during their lifetimes. Current methods of prostate cancer detection include digital rectal examination (DRE) and prostate specific antigen (PSA) screening. However, these screening tools often suffer from low accuracy, including the frequent generation of ambiguous results, false positives and false negatives.

[0004] In many instances, the result of ambiguous results or false positives in screening results in additional procedures, such as taking a biopsy from the prostate and analyzing the biopsied tissue for cancer pathology. Biopsies are very invasive, expensive, time-consuming, and can increase risk of procedure-related complications such as infection, urinary/sexual dysfunction, and even death. Nevertheless, due to the high rates of ambiguous results and false positives resulting from current screening methods, many of these invasive procedures are performed needlessly on individuals not having prostate cancer. [0005] On the other hand, biopsies may also produce false negatives. In particular, small regions of tumors may go undetected, such as when an insufficient number of biopsy cores are made, the biopsy cores are not properly spread, or the tumor cells are simply not included in any of the biopsied and tested tissue. In addition to false positives in biopsies, screening methods can also produce false negatives. Physicians may miss a tumor during a DRE, and a PSA test may provide a low PSA reading despite the subject having prostate cancer.

BRIEF SUMMARY

[0006] The present disclosure relates generally to devices, systems, and methods for generating high-resolution images of internal tissues located within a patient's body. In some embodiments, a imaging device includes a radiation detector configured for detecting x-ray radiation, and a delivery structure coupled to the radiation detector. The radiation detector is configured in size and shape to enable positioning of the radiation detector internally within a patient, andthe delivery structure is configured to support the radiation detector during imaging of one or more internal tissues.

[0007] Internal tissues which may be imaged using one or more of the embodiments described herein include: endorectal tissues and prostate tissues; vaginal and cervical tissues; upper gastrointestinal tract tissues such as oral, tracheal, and esophageal tissues; the colon; the rectum; ovaries; the thyroid; other tissues surrounding or otherwise associated with the foregoing tissues, and/or tissues accessed through a surgical incision.

[0008] In some embodiments, a tissue imaging system includes a imaging device and a radiation source configured to direct x-ray radiation toward the imaging device. In some embodiments, a method for high-resolution imaging of one or more internal tissues includes positioning a imaging device within a patient such that the radiation detector is proximal to a targeted area of interest, and such that at least a portion of the targeted area of interest is disposed between the radiation detector and a radiation source, directing x-ray radiation from the radiation source toward the radiation detector, and the radiation detector detecting x-ray radiation passing through the targeted area of interest to enable the generation of image data.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] To further clarify the above and other advantages and features of the present disclosure, a more particular description of the disclosure will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. It should be appreciated that these drawings depict only illustrated embodiments of the disclosure and are therefore not to be considered limiting of its scope. Embodiments of the disclosure will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:

[0010] Figure 1A through 1C illustrate exemplary embodiments of imaging devices;

[0011] Figures 2A and 2B illustrate an imaging device movable between a folded configuration with a profile suitable for insertion within a patient and an unfolded configuration having a larger detection surface;

[0012] Figure 3 illustrates an imaging device configured to rotate so as to maintain desired orientation with respect to the radiation source;

[0013] Figure 4 illustrate an exploded view of an imaging device showing the different layers according to one embodiment; [0014] Figures 5A and 5B illustrate an imaging device including an indexing mechanism for determining the location of the device in relation to the radiation source;

[0015] Figure 6 illustrates an antiscatter grid which may be utilized with an imaging device as described herein;

[0016] Figure 7 illustrates image acquisition through sweeping of a radiation beam through an arc over a targeted area of interest;

[0017] Figures 8A and 8B illustrate an embodiment of a tissue imaging system endorectally inserted for imaging of a patient's prostate;

[0018] Figures 9 A and 9B show images of a surrogate prostate as generated using scanned projection radiography scanning on a CT scanner, with images generated using the built-in CT scanner detector array (Figure 9A) compared to images generated using an endorectal imaging device (Figure 9B);

[0019] Figure 10A and 10B illustrate images of implanted low dose rate brachytherapy seeds in a plastic phantom pelvis generated with scanned projection radiography scanning on a CT scanner, with images generated using the built-in CT scanner detector array (Figure 10A) compared to images generated using an endorectal imaging device (Figure 10B);

[0020] Figure 11A and 11B illustrate images of implanted low dose rate brachytherapy seeds in a gelatin phantom pelvis generated with scanned projection radiography scanning on a CT scanner, with images generated using the built-in CT scanner detector array (Figure 11 A) compared to images generated using an endorectal imaging device (Figure 11B);

[0021] Figure 12 illustrates a reconstructed image plane using a tomosynthesis reconstruction method of the plastic phantom with brachytherapy seeds; and [0022] Figure 13 illustrates a reconstructed image plane using a tomosynthesis reconstruction method of the gelatin phantom with brachytherapy seeds.

DETAILED DESCRIPTION

Introduction

[0023] The present disclosure relates generally to devices, systems, and methods for generating high-resolution images of internal tissues. In at least some circumstances, the devices, systems, and methods disclosed herein are capable of generating high-resolution images of internal tissues that are located within a patient's body, and which are therefore not amenable to high-resolution imaging using the imaging devices, systems, and methods of the prior art.

[0024] Internal tissues which may be imaged using one or more of the embodiments described herein include: prostate tissues; vaginal and cervical tissues; upper gastrointestinal tract tissues such as oral, tracheal, and esophageal tissues; the colon; the rectum; ovaries; the thyroid; and/or other tissues surrounding or otherwise associated with these tissues. Additionally, or alternatively, one or more embodiments described herein may be used in the imaging of other internal tissues, such as tissues that are accessed through surgical incisions. Although many of the particular examples described herein are directed to prostate tissue imaging, one of skill in the art will recognize, in light of this disclosure, the other applications in which certain embodiments may be utilized.

[0025] Other imaging methods are sometimes included as part of prostate cancer screening. However, if the resulting images lack sufficient quality and resolution to enable full screening using imaging methods alone, ambiguous or suspicious results will still frequently lead to invasive biopsy procedures for more determinative diagnosis.

[0026] Magnetic resonance imaging (MRI) is the current gold standard for prostate imaging technology, with multiparametric MRI becoming more effective for early stage prostate cancer detection. Contrast enhanced ultrasound microbubbles is another newer technology with some promise for detecting early stage prostate cancer. However, the costs associated with these imaging methods for prostate cancer screening can be prohibitive, particularly with methods based on MRI. Further, MRI- based imaging is a slow and expensive process, and patient movement during imaging will disrupt image quality. Also, some patients cannot be subjected to MRI techniques (e.g., patients with a pacemaker), and some MRI methods may suffer from susceptibility artifacts and poor signal reach for tissues deep within the body (such as the prostate and cervix).

[0027] Transrectal ultrasound (TRUS) is another primary prostate imaging method. It can accurately visualize the prostate for image-guided biopsy and can be used to assess prostate volume. It is not effective for visualizing cancer within the prostate due to poor contrast differentiation between normal prostate tissue and cancer. Image quality is also highly dependent on operator skill and properly adjusted equipment settings.

[0028] Nuclear imaging techniques, such as positron emission tomography (PET) and single photon emission computed tomography (SPECT) are also capable of providing tissue imaging and screening, but suffer from a lack of effective prostate cancer radiotracers for functional imaging. Conventional computed tomography (CT) scanning may also be used, but produces images with poor soft tissue contrast. For example, conventional CT imaging it is difficult to contrast between the prostate and nearby soft tissue anatomy such as the levator ani muscle.

[0029] Local prostate cancer recurrence is associated with a significantly increased risk for metastatic disease. The process may occur as follows: a patient undergoes a radical prostatectomy procedure and the prostate gland is removed. Approximately 30-35% of these men will experience a bio-chemical relapse - their PSA levels begin rising as if they have prostate cancer. It takes an average of eight years between the bio-chemical relapse and distant metastasis.

[0030] Because prostate cancer local recurrences can be efficiently treated by salvage therapies, it becomes critical to detect them early. Multiparametric MRI has been used increasingly in the early detection and localization of local recurrence by enhancing imaging of recurrent nodules. In dynamic contrast-enhanced MRI (DCE- MRI), which is one of the particular scans usually performed in multiparametric MRI, uptake and washout of blood to certain tissues is assessed. Prostate cancer in general has more blood vessels than surrounding, non-cancerous tissues, so a region of prostate cancer will appear to have a higher signal. In DCE-MRI, spatial resolution is typically 1-2 mm and temporal resolution is typically 5-18 seconds, which may affect the detection of small recurrences. This can result in lesions developing undetected that may metastasize and lead to a significant risk of metastatic disease within prostate cancer patients that have received treatment by tradition means (radiation therapy, chemotherapy, brachytherapy, prostatectomy, etc.). Further, despite the benefits, such MRI-based imaging methods may be slow and cost-prohibitive.

[0031] At least some of the embodiments described herein overcome one or more of the foregoing difficulties by providing high-resolution images of the prostate and surrounding tissues, enabling greater certainty in defining the prostate and greater ability to distinguish the prostate from other nearby tissues. One or more embodiments disclosed herein also overcome similar challenges related to the imaging of other internal tissues located in and/or near body cavities, such as the internal tissues described above.

[0032] Further, certain embodiments provide greater image resolution, relative to at least some conventional imaging methods, for a given radiation exposure/dose, thereby enabling the same or better resolution compared to typical methods with less required patient exposure to radiation.

[0033] One or more embodiments may be used in conjunction with a contrast agent. For example, an iodine contrast agent may be administered to a patient/subject for imaging using the devices, systems, and/or methods described herein, to provide greater tissue contrast and/or other beneficial imaging effects. Such contrast enhancements can improve visualization of vasculature in and around the prostate to aid in the detection of local prostate cancer and local recurrence following treatment. Such methods may allow for superior imaging of local cancer recurrence and it may be recommended that it be performed at regular intervals - for example, once per year.

[0034] Certain embodiments described herein are also useful in imaging brachytherapy seeds. Such seeds may be misplaced and/or may migrate to other locations within the body during or after treatment, and post-implantation imaging is typically required to ensure seed locations and orientations match desired locations. However, the limited resolution of conventional CT scanning often makes it difficult to differentiate seeds that are overlapping or otherwise close together. One or more embodiments can be utilized to provide images related to post-implantation dosimetry. Beneficially, the high-resolution generated through use of the disclosed embodiments improves capability in determining seed position and orientation.

[0035] Certain embodiments described herein are also useful for the imaging of periprostatic adipose tissue (PPAT) near the prostate. In some studies, PPAT has shown a positive correlation with tumor aggressiveness in prostate cancer patients. High-resolution images of PPAT surrounding the prostate, using one or more of the embodiments described herein, can aid in prostate cancer screening, diagnosis, watchful waiting, and/or active surveillance.

Imaging Device

[0036] Exemplary embodiments of imaging devices are illustrated in Figures 1 A through 5B. In the illustrated embodiments, the imaging devices are configured as x- ray detectors (XRDs) configured to be internally positionable near one or more targeted tissues of interest so as to receive radiation projected through the targeted tissue(s) of interest for imaging of the tissue(s). Exemplary embodiments described below are directed toward particular implementations as endorectal probes for imaging related to endorectal positioning of a detector (e.g., prostate, cervical, or colon imaging). However, such particular implementations are exemplary only, and one or more embodiments may be directed, additionally or alternatively, to the imaging of other tissues, such as those described above.

[0037] Figure 1 A illustrates a imaging device 100 having a radiation detector 104 coupled to a delivery structure 106 (e.g., shaft, delivery catheter, guidewire, probe, etc.) configured to enable delivery and/or positioning of the radiation detector 104 internally at or near a given area of interest. In some embodiments, the delivery structure 106 is omitted. The illustrated imaging device 100 is configured such that when inserted into a patient, the radiation detector 104 is positioned nearby the targeted tissue of interest with the detection surface 102 oriented toward the tissue of interest. The imaging device 100 is configured in size and shape to allow insertion into the patient.

[0038] The rectum has limited space for the placement of the imaging device 100. In one embodiment, the radiation detector 104 has a length of about 5.0 cm, a width of about 2.0 cm, and a thickness of about 0.5 cm. In other embodiments, the radiation detector 104 may have a size of about 20-60 mm in length, about 20-30 mm in width, and a thickness of about 2-25 mm. Other embodiments may have one or more dimensions outside the foregoing ranges. The size of the radiation detector 104 may be determined based on the size of the tissue to be imaged, patient anatomy, and/or particular application needs.

[0039] The radiation detector 104 is configured for operation at energies typical for medical imaging (e.g., about 20 kVp to 140 kVp). The radiation detector 104 may be configured for operation at an energy level dependent on what the imaging device 100 is to be used with as a radiation source.

[0040] The radiation detector 104 may be communicatively coupled to a processor (e.g., via hardwire connection or wireless connection). In such embodiments, one or more connection wires may be coupled to the delivery structure 106 (e.g., adhered to the shaft, coiled around the shaft) and/or may pass through a lumen of the delivery structure 106 to wire the radiation detector 104 to the processor. Alternatively, a wireless transmitter may be may be housed within the radiation detector 104 to provide wireless transmission (e.g., via Bluetooth or other suitable wireless signaling protocol) of x-ray detection data from the radiation detector 104 to the processor. In some embodiments, a processor having image reconstruction software may be housed within the radiation detector 104 to provide transmission (e.g., via Bluetooth or other suitable wireless signaling protocol) of reconstructed image data to a suitable viewing device.

[0041] The radiation detector 104 may include a charge couple device (CCD), a complimentary metal-oxide semiconductor (CMOS), a thin film transistor array (TFT), other suitable detector type, or combination of the foregoing, with or without a suitable medium for converting x-rays to a readable signal (e.g., a scintillator layer to convert x-ray to light to be detected by a CCD chip) as required by detector type.

[0042] Figures IB and 1C illustrate alternative embodiments of imaging devices 200 and 300 with radiation detectors having curved detection surfaces in contrast to the substantially flat detection surface 102 of imaging device 100 shown in Figure 1A. As shown in Figure IB, the detection surface 202 may be concave in shape, and as shown in Figure 1C, the detection surface 302 may be convex in shape. The imaging devices 200 and 300 may otherwise be configured in a manner similar to the imaging device 100. The curved detection surfaces shown in Figures IB and 1C may functionally increase the field of view. For example, such embodiments can beneficially align the detection surface with an arcing radiation source, such that the portion of the detection surface at which the radiation source is generally directed, at a given moment in a scan, is substantially normal to the radiation beam. In some embodiments, the imaging device 200 and/or imaging device 300 is configured to be moveable to a curved configuration (e.g., after insertion into a patient).

[0043] Figures 2A and 2B illustrate an embodiment in which a imaging device 400 includes a plurality of overlaid or attached panels, each panel being functional as a radiation detector. The separate panels may be joined in a flexible or hinge-like fashion. The illustrated imaging device 400 includes a first lateral panel 408, a second lateral panel 412, and a central panel 410 disposed therebetween. Each of the panels may include an x-ray sensor so that each separate panel contributes to the overall detection surface of the device. Alternative embodiments may include more or less than three panels coupled together in a foldable arrangement; for example, two, four, five, or six panels may be coupled together in a foldable arrangement.

[0044] Foldable embodiments such as shown in Figures 2A and 2B are moveable from a folded/collapsed configuration (as shown in Figure 2A) to an unfolded/open position (as shown in Figure 2B). For example, the imaging device 400 may be endorectally inserted while in the folded/collapsed configuration. Then, after insertion, the panels 408, 410, and 412 may be unfolded or otherwise opened so as to expose the detection surface. Preferably, such an expandable imaging device is selectively collapsible back into the smaller profile folded/collapsed position in order to enable emergency removal as necessary.

[0045] The adjustable functionality of the imaging device 400 may beneficially improve imaging of the targeted area of interest. For example, when the prostate or other area of interest is larger than the detector's field of view, truncation artifacts may result. The unfolded/open position shown in Figure 2A provides a relatively larger detection surface which can minimize or eliminate such truncation artifacts.

[0046] The imaging device 400 may otherwise be configured in a manner similar to the other imaging devices 100, 200, and 300 described above. For example, the foldable imaging device 400 may include one or more panels having a curved detection surface.

[0047] Figure 3 illustrates an embodiment of a imaging device 500 configured to rotate with the radiation source so as to maintain alignment with the source. As shown, the device may rotate such that the detection surface 502 maintains a perpendicular orientation with respect to the radiation beam 514. In some embodiments, the delivery structure 506 of the delivery device 500 is mechanically coupled to a rotating assembly (not shown). The rotating assembly (e.g., bearing assembly or other suitable means of rotational power transmission) may be positioned external of the patient during an imaging procedure to provide selective operator control over rotational position of the imaging device 500. The imaging device 500 may otherwise be configured in a manner similar to that of any the above described imaging devices, such as imaging device 100, 200, or 300.

[0048] In some embodiments, a imaging device includes a balloon. For example, a imaging device may include an expandable balloon (e.g., formed from latex or some other biocompatible material) which may be inflated after insertion into the rectum to bring the imaging device into better contact with surrounding tissues and/or to better hold the imaging device in a desired position or orientation. In some embodiments, a imaging device is configured to expand in size and/or available detection surface area upon expansion of the balloon. The balloon may be expanded, for example, using air, perfluorocarbon (PFC), water, saline, other suitable inflation agent, or combination thereof.

[0049] Figure 4 illustrates an exploded view of an embodiment of a imaging device 600 showing various layers of the device. The above described imaging device embodiments may be likewise formed. As shown, a front cover 616 and a rear cover 618 form a housing which holds an x-ray detection layer 620 and corresponding electronics layer 622. As described above with respect to radiation detector 104, the x-ray detection layer 620 may be configured to function as a charge couple device (CCD), a complimentary metal-oxide semiconductor (CMOS), a thin film transistor array (TFT), other suitable detector type, or combination of the foregoing, with or without a suitable medium for converting x-rays to a readable signal (e.g., a scintillator layer to convert x-ray to light to be detected by a CCD chip) as required by detector type. The x-ray detection layer 620 and electronics layer 622 are preferably configured to provide a pixel size of about 0.3 mm or less. The x-ray detection layer 620 and electronics layer 622 are preferably configured to provide a resolution of about 5-25 line pairs (lp)/mm, or about 9-20 lp/mm.

[0050] Figures 5A and 5B illustrate an embodiment of a imaging device 700 including one or more radiopaque indexing members 724 configured to provide position indexing of the radiation detector in relation to the x-ray source during scanning. Figure 5B is an expanded view of a portion of the device shown in Figure 5A to better show an indexing member 724 and resulting shadow 726 resulting from x-ray radiation. The one or more indexing members 724 are disposed within housing 716 to protect the indexing members 724 from damage and to prevent injury to the patient. The illustrated embodiment shows the indexing members 724 as pins, but other projecting shapes may additionally or alternatively be utilized. The indexing members 724 may be disposed about the perimeter of the detection surface 702 to assist a user/operator in proper positioning of the detector relative to a targeted area of interest. When the detector is subjected to x-ray radiation from an x-ray source, the indexing member 724 may cast a shadow 726 onto the detection surface 702. The size and/or orientation of the shadow 726 may provide angular positioning information to an operator. The illustrated imaging device 700 may otherwise be configured in a manner similar to the above described imaging device embodiments.

[0051] Figure 6 illustrates an exemplary antiscatter grid 828. Some imaging device embodiments, including any of the above-described embodiments, may include and/or be associated with the antiscatter grid 828. The antiscatter grid may be positioned between the targeted tissue or area of interest and the detection surface, and functions to filter radiation that has been overly scattered as a result of passage through tissue. As shown in Figure 6, overly scattered radiation 815 is filtered, while radiation 814 passes through the grid 828 to the underlying detection surface. The antiscatter grid 828 may be formed with a grid ratio (height to width of interspace material) of about 5 to 20, or about 10, or other ratio suited to a particular application, as needed.

[0052] The grid 828 may be moveable between foldable and unfoldable positions and/or may be configured to be directly coupled or built into the housing of the imaging device. For example, an embodiment of a collapsible/foldable imaging device can be associated with a grid that is likewise collapsible/foldable. Additionally, or alternatively, the grid 828 may have a curved surface and/or may be capable of adjustment so as to be curved. In this manner, the grid 828 may be more effectively aligned with the arc of travel of the radiation source.

Tissue Imaging Systems

[0053] In some embodiments, a tissue imaging system includes a imaging device and a radiation source configured to project an x-ray beam through the tissue of interest. The x-ray source is preferably configured to enable the directing of x-rays incrementally over a predetermined arc. In some embodiments, imaging is carried out using multi-energy image acquisition (e.g., at 30 kVp and 40 kVp) to enhance soft tissue contrast, phase contrast imaging, contrast enhanced imaging, and/or x-ray scattering imaging. In some embodiments, the radiation source includes a CT scanner as an x-ray source. In another embodiment, the CT scanner is a retrofit CT scanner that includes components and/or modifications enabling more efficient use of the CT scanner for high-resolution imaging of internal tissues according to embodiments described herein. For example, a CT scanner can be modified by operatively associating a imaging device to the CT scanner. In some embodiments, the radiation source includes an x-ray tube, linear path radiography tube, or other radiation source having micro-focus functionality and that is arranged and indexed for use with the tissue imaging devices and methods described herein.

[0054] In some embodiments, the radiation beam is highly collimated, and the field of view is highly restricted, in order to minimize scatter and out of field patient dose. Beneficially, the close proximity of the imaging device to the prostate or other tissue of interest enables the use of a restricted field of view and the concomitant advantages of scatter minimization and reduced geometric distortion from the finite sized focal spot in the x-ray tube. In some embodiments, the tissue imaging system also includes a collimator. For example, a collimator may be positioned between the radiation source and the patient.

[0055] As illustrated by Figure 7, image acquisition may be performed by sweeping a radiation source 940 through an arc over the targeted area of interest 930. The internally positioned imaging device 900 then receives the passing radiation 914. Projection images may be captured while the radiation source 940 is traveling through the arc. In some embodiments, capture of the projection images is accomplished in about 2 to 45 seconds, or about 3 to 30 seconds, or about 4 to 20 seconds, or within another scan time suited to a particular application. The scan time may be adjusted based on application requirements.

[0056] In some embodiments, the arc angle may be less than 5 to more than 90 degrees, with less than 5 to more than 100 images comprising the projection image dataset. In one example, a projection image is captured for about every 0.5 to 5 degrees, or about every 0.75 to 3 degrees, or about every 1 to 2 degrees of travel through the arc. Arc angles and image capture parameters may be configured to suit a particular application, as needed. In alternative embodiments, the radiation source 940 may be passed through a linear path instead of an arc.

[0057] Figures 8A and 8B illustrate an embodiment of a tissue imaging system including a imaging device 1000 coupled to a table attachment 1050. The imaging device 1000 is shown positioned within a patient 10 (shown schematically) at a position for imaging of the prostate 12. As shown, a table attachment 1050 may be provided in order to provide positioning/indexing information related to the imaging device 1000. For example, the table attachment 1050 may be adjustable according to x, y, and z coordinates (e.g., relative to the table 1052 on which it rests) to aid an operator in appropriately positioning the imaging device 1000 within the patient. The table attachment 1050 may additionally or alternatively be configured to provide rotational adjustment of the imaging device 1000 relative to the table attachment 1050. The table attachment thereby provides for precise location of the imaging device 1000 within the patient relative to the radiation source.

[0058] As shown in Figure 8B, a radiation source may direct x-ray radiation 1014 (shown as the "slice" between the dashed lines) toward the patient 10. The radiation 1014 may then be detected by the imaging device 1000, which is beneficially positioned near the targeted prostate 12 to enable high-resolution images and/or low- radiation-dose images of the targeted prostate 12. The radiation may be directed from a CT scanner, an x-ray tube, or other suitable x-ray source. Although the illustrated radiation beam 1014 is shown as relatively wide, it will be understood that the size of the beam will depend on the particular radiation source utilized. Tomosynthetic Reconstruction

[0059] In some embodiments, image data is gathered as a set of projection images, which may be compiled into three-dimensional and/or cross-sectional image data of the tissues of interest using one or more tomosynthesis reconstruction processes. For example, a set of projection images may be reconstructed using a geometric technique, a shift and add technique, a filtered back projection technique, an iterative reconstruction technique, other suitable image reconstruction algorithm or process, or combination of the foregoing.

[0060] For example, a geometric technique consists of registering projection images collected at variable arc angles and, based on the length of traversed arc of anatomical landmarks or other points of reference, determining the location of anatomical landmarks or other points of reference. For example, a shift and add technique may include shifting the acquired images a known amount, summing the images by projection, and normalizing the output. For example, a filtered back projection technique may include the use of Fourier based post-processing. For example, an iterative reconstruction technique may include starting with an image "guess," comparing an actual projection with the guess, modifying the guess to form a forward projection, comparing an error matrix, and repeating until the error matrix is acceptable.

EXAMPLES

Example 1

[0061] In a first example, a surrogate prostate (small citrus fruit) was positioned in a constructed pelvic phantom simulating the male pelvis. A GE Lightspeed RT16 CT scanner was used to collect a set of planar radiographs of the phantom. Images were collected using SPR mode on the CT scanner. Figure 9A shows an image collected using the built-in CT scanner detectors, while Figure 9B shows an image collected using a imaging device endorectally positioned within the pelvic phantom. As shown, the images collected using the imaging device has superior resolution as compared to the image captured using the CT scanner's own detectors.

Example 2

[0062] In a second example, collection of low dose rate brachytherapy (LDRBT) seeds (length of shell about 4.5 mm, diameter of shell about 0.8 mm, length of core about 3 mm, diameter of core about 0.5 mm) were scanned. Two phantoms simulating the male pelvic region were used to test the capabilities of an endorectal imaging device for imaging permanent brachytherapy seed implants. Phantom 1 was constructed from sheets of acrylic plastic with cavities milled in the locations of the prostate and the rectum. The prostate cavity was filled a Styrofoam plug containing 10 training seeds. Training seeds are radioactive low-dose rate brachytherapy seeds that have been allowed to decay to a minimal level of radioactivity safe to handle. Phantom 2 was constructed from a tissue-equivalent gelatin and contained a gelatin prostate phantom implanted with 18 strands of training seeds. A imaging device was placed posteriorly in the phantom rectum within 2 cm of the center of the region implanted with seeds. Scout scans were taken of the phantoms over a limited arc angle using a CT scanner (GE Lightspeed RT16, 80 kV, 120 to 200 mA, 5 cm scan length, images taken from 340° to 20° in 2° increments). The detector was removed from the phantoms and normal helical CT and scanned projection radiography (0°) scans were collected (120 kV, auto-mA, 10 cm scan length). [0063] Figures 10A and 10B show images of the seeds implanted within the plastic pelvic phantom. Figure 10A shows a planar image using CT detector array with radiation from the CT scanner in scanned projection radiography mode, while Figure 10B shows a planar image captured using the endorectal detector with radiation from the CT scanner in scanned projection radiography mode. Figures 11A and 11B show images of the seeds implanted within the gelatin plastic phantom. Figure 11 A shows a planar image using CT detector array with radiation from the CT scanner in scanned projection radiography mode, while Figure 11B shows a planar image captured using the endorectal detector with radiation from the CT scanner in scanned projection radiography mode. As shown, the images captured using the endorectal detector show superior resolution of the brachytherapy seeds.

Example 3

[0064] Images of brachytherapy seeds were subjected to tomosynthetic reconstruction using a shift and add technique. Figure 12 illustrates a reconstructed image of a plane located 0.8 cm from detector surface. The image shows characteristic blurring of shift and add tomosynthesis reconstruction method with the seed in the reconstructed plane appearing bright (seed reinforces and does not blur out). Figure 13 illustrates a reconstructed image of a plane located 2.6 cm from the detector surface. The image shows characteristic blurring (the dimmer seeds) of shift and add tomosynthesis reconstruction method with the seeds in the reconstructed plane appearing bright.

[0065] The present disclosure may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the disclosure is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.