Patent Application
20080061242
While the appended claims set forth the features of the present invention with particularity, the invention, together with its objects and advantages, may be best understood from the following detailed description taken in conjunction with the accompanying drawings of which:
This invention provides a multi-modality imaging system for use in radical medicine and methods of using the same. In the following, the invention will be discussed in connection with various embodiments. In view of the many possible embodiments to which the principles of this invention may be applied, it should be recognized that the embodiments described herein in connection with the drawings are meant to be illustrative only and should not be taken as limiting the scope of invention. Those skilled in the art will recognize that the illustrated embodiments can be modified in arrangement and detail without departing from the spirit of the invention. The embodiments that will be discussed herein are not mutually exclusive, unless so stated, or if readily apparent to those of ordinary skill in the art.
Referring to the drawings,
Imaging assembly 102 of this example can be SPECT, PET, SPECT/CT, or PET/CT, or other nuclear imaging instruments used in radical medicine. Patient pallet 106 is provided for supporting a patient undergoing imaging. In operation, the pallet is aligned to imaging axis 110 of the imaging assembly. Such position of the pallet is referred to as the imaging position.
For enabling real-time therapy, such as prostate brachytherapy during or shortly after the imaging process, the pallet is constructed such that the pallet is movable, especially rotatable about a rotational axis that is preferably perpendicular to the pallet. As shown in the figure, the rotation axis passes through pivoting point 108 and normal to the imaging axis 110. The pivoting point can be stationary or movable when the pallet is moving. It is preferred that the pivoting point is within the pallet, but not required. The rotated position is referred to as an intervention position, which is shown in
Referring to
In the intervention process (or imaging process), the pallet is rotated to an angle such that the detector can be placed as close to the organ of interest as possible, which is better illustrated in a top view of the system in
The rotatable pallet in the radical imaging system as discussed above can be configured in many ways, examples of which are demonstratively illustrated in
An alternative configuration of the rotatable pallet is illustrated in
Nuclear Imaging Systems with Converging Collimators
Current nuclear imaging systems for use in nuclear medicine, such as nuclear imaging systems for prostates, are limited by long imaging time and poor spatial resolution. It is often difficult to determine, for example, whether prostate cancer has spread beyond the prostate gland into the seminal vesicles, or vicinity lymph nodes. A solution to this problem is provided herein according to a further aspect of the invention.
The radical imaging system according to an example of the invention employs modern iterative reconstruction (e.g. maximum likelihood with 3D-beam modeling) techniques that have the capability of correcting depth dependent resolution and attenuation. A large Filed-of-View (hereafter FOV) short focal length cone beam collimator is used for taking images. The collimator can be constructed such that the collimator is movable relative to the patient (or the FOV) or the camera. Moreover, the collimator can be constructed with structures that are dynamically movable during imaging. By adjusting the structures of the collimator, focal length and spatial resolution of the collimator can be dynamically adjusted when necessary. The system thus can be of great importance for detecting prostate cancer and for brachytherapy treatment of prostate cancer because the radioactive seed is enabled to be localized with CT, and images obtained therefrom can be fused with SPECT so as to correlate density of seed placement with active tumor regions.
As an example of this aspect of the invention, the collimator has a finite (non-infinite) focal length. Such a collimator can be accomplished in many ways. For example, the collimator may be composed of a stack of slats. The slats are tilted non-uniformly such that imaginary extensions of the slats converge at a point—the focal point of the collimator. Collimator 136 in
As an aspect of the invention, the collimator is formed of a stack of slats that are dynamically movable. For example, each slat is coupled with a driving mechanism for moving (e.g. rotating) the slat. The movement can be translational or rotational or a combination thereof. In operation, the slats can be configured to have an infinite focal length by positioning the slats in parallel. When necessary, for example, in precise imaging, the slats can be configured dynamically to have the finite focal length. This can be done by moving the slats appropriately using individual driving mechanism coupled to the slats. If necessary, the slats can be dynamically adjusted to change the spatial resolution of the imaging system (also the spatial resolution of the image). This can be accomplished for varying the distance between adjacent slats of the collimator.
Regardless of whether the collimator is configured to have or not have a finite focal length, the collimator is preferably constructed in the imaging system such that the collimator, the field of interest, or the camera is capable of relative movement. As an example, the collimator is coupled to a moving mechanism, such as a motor, for moving the collimator relative to the camera or the field of interest or both. In another example, the camera can be coupled to a moving mechanism for moving the camera relative to the collimator or the field of interest or both. In yet another example, the camera and collimator can be associated together and coupled to a moving mechanism such that both of the camera and collimator are movable (e.g. together) relative to the field of interest.
Mobility of the collimator (or both of the collimator and camera) can be of great importance when the collimator has finite focal length. With the finite focal length and mobility, high spatial resolution and image acquisition efficiency can be obtained in imaging. Moreover, imaging and therapy can be performed simultaneously. This is accomplished by placing the focal point of the collimator on the field of interest and scanning the focal point across the field of interest. By combining the sequence of images taken at each location during scanning, a tomographic image of the field of interest can be reconstructed. Specifically, by lateral (or raster) motion of the camera and collimator or the collimator only, longitudinal (with limited angle) images can be acquired for the formation of a multi-plane tomographic image of the field of interest, such as prostate gland 132 and vicinity. For imaging the field of interest, such as the prostate (or any other desired body part) either by scanning the focal point over the gland or by magnification, sensitivity gain as compared to collimators composed of parallel holes can be very large. As a way of example, assuming the camera has a FOV of 12″ (30 cm) and typical size of prostate from 3 to 4 cm, the magnification can be approximately 7 to 10. Sensitivity gains relative to PHC can be approximately (7.5)2 to (10)2 or from 50 to 100.
Imaging speed can also be improved. For example, prostate SPECT studies normally take around 50 minutes with dual-head parallel hole collimator. The spatial resolution is approximately 2 cm. With a converging collimator as discussed above, the spatial resolution of the imaging system can be can be improved to approximately 1.3 cm or higher resolution. The imaging time can be significantly reduced to approximately 5 minutes or less, or even 1 minute or less.
An imaging system with a scanning focal point can be adapted to easily identify the position of highest tracer uptake in the prostate gland. By making small movement steps in X-Y-Z, directional gradient of the count density that representing the tracer density can be determined. The location of the “hot spots” wherein negative tumor is more likely located can be identified. Needle biopsy samples can then be taken from the identified negative regions with the highest tracer uptake.
It can also be beneficial in seed placement in brachytherapy to image either the seed or the needle used for seed placement simultaneously with the nuclear tracer image of the prostate. The prostate is deformable by a needle of ultrasonic probe. Hence, better optimization in seed placement may be possible if both seed (on needle) and radioisotope tracer are imaged simultaneously in a real-time fashion. Common isotopes capable for brachytherapy are listed in Table 1.
The imaging system of the invention has many advantages. For example, formation of the tomographic images do not need to be analog as required in many existing imaging systems for use in radical or nuclear medicine. Images can be reconstructed based upon statistical methods, such as maximum likelihood, maximum posterior, maximum entropy, and other suitable statistical methods.
With the high magnification and sensitivity of the system, images can be refreshed frequently during the study such that most current state of the gland subject to dynamic deformation can be obtained, and monitored in real-time.
Using a collimator composed of movable stacks of slats, the camera can acquire images in both parallel and converging focusing modes. Data acquisition in the parallel mode can facilitate comparison with conventional SPECT studies.
In another aspect of the invention, the collimator may be composed of a stack of movable slats such that the spatial resolution of the collimator can be varied. Specifically, slats of the collimator can be moved or rotated uniformly, for example, in the same direction and with the same displacement. Alternatively, the slats can be moved individually, preferably according to a predetermined pattern, such as a pattern such that a unique focal point is defined. The latter instance can be achieved by coupling each slat with a moving mechanism, such as electrostatic force with addressing electrodes or mechanical force, which will not e discussed in detail herein.
High resolution imaging with collimation angle of approximately 0.02 radians can yield system spatial resolution at 15 cm of approximately 6 mm. Such high resolution will be useful to determine if the cancer is confined to the prostate capsule or has invaded into nearby structures such as the seminal vesical. It is also noted that embodiments of the invention are also applicable to other type of cameras and can be used in examining and/or treating other organs or other parts of a human (or animal) body.
A non-transaxial single photon scanning tomographic imager using large short focal length collimation, preferably with moving slat septa can image the major arteries seen in prostate scan with high resolution. The presence of positive lymph nodes near arteries is currently is difficult. A scanner that can focus on and track arterial vessels can detect abnormal lymph nodes with higher accuracy.
For imaging the prostate and vicinity, the focal point of the collimator scans different locations across the prostate and vicinity. At each location, an image is taken representing an image of the transverse layer of the prostate (or the vicinity). After the scanning, the sequence of images is reconstructed so as to form a tomographic image of the prostate and vicinity. The reconstructed tomographic image carries functional information of the prostate and vicinity and can be fused with atomic image obtained from suitable imaging systems, such as CT. The fused image can be used for guiding the treatment of the prostate when disease is found therein. In fact, imaging and treatment can be performed at the same time. For example, given a CT image, treatment actions can be taken as the functional images of the prostate being taken. Because of the efficient and short imaging time, functional images can be refreshed frequently, in the range from 20 seconds to 2 minutes during the interventional procedure. Frequent refreshing rates enable accurate treatment and real-time monitoring of the treatment, which improves treatment quality.
It will be appreciated by those skilled in the art that a new and useful radical imaging system and method of using the same have been described herein. In view of the many possible embodiments to which the principles of this invention may be applied, however, it should be recognized that the embodiments described herein with respect to the drawing figures are meant to be illustrative only and should not be taken as limiting the scope of invention. Those of skill in the art will recognize that the illustrated embodiments can be modified in arrangement and detail without departing from the spirit of the invention. Therefore, the invention as described herein contemplates all such embodiments as may come within the scope of the following claims and equivalents thereof.
