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Adaptive x-ray controlRelated Patent Categories: X-ray Or Gamma Ray Systems Or Devices, Electronic Circuit, Object Responsive ControlAdaptive x-ray control description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070189455, Adaptive x-ray control. Brief Patent Description - Full Patent Description - Patent Application Claims
TECHNICAL FIELD [0001] Embodiments of the invention relate to medical imaging and, in particular, to the control of x-ray exposure during medical imaging. BACKGROUND [0002] Radiosurgery and radiotherapy systems are radiation treatment systems that use external radiation beams to treat pathological anatomies (e.g., tumors, lesions, vascular malformations, nerve disorders, etc.) by delivering a prescribed dose of radiation (e.g., x-rays or gamma rays) to the pathological anatomy while minimizing radiation exposure to surrounding tissue and critical anatomical structures (e.g., the spinal chord). Both radiosurgery and radiotherapy are designed to necrotize the pathological anatomy while sparing healthy tissue and the critical structures. Radiotherapy is characterized by a low radiation dose per treatment, and many treatments (e.g., 30 to 45 days of treatment). Radiosurgery is characterized by a relatively high radiation dose in one, or at most a few, treatments. [0003] In both radiotherapy and radiosurgery, the radiation dose is delivered to the site of the pathological anatomy from multiple angles. As the angle of each radiation beam is different, each beam can intersect a target region occupied by the pathological anatomy, while passing through different regions of healthy tissue on its way to and from the target region. As a result, the cumulative radiation dose in the target region is high and the average radiation dose to healthy tissue and critical structures is low. Radiotherapy and radiosurgery treatment systems can be classified as frame-based or image-guided. [0004] In frame-based radiosurgery and radiotherapy, a rigid and invasive frame is fixed to the patient to immobilize the patient throughout a diagnostic imaging and treatment planning phase, and a subsequent treatment delivery phase. The frame is fixed on the patient during the entire process. Image-guided radiosurgery and radiotherapy (IGR) eliminate the need for invasive frame fixation by tracking and correcting for patient movement during treatment. [0005] Image-guided radiotherapy and radiosurgery systems include gantry-based systems and robotic-based systems. In gantry-based systems, the radiation source is attached to a gantry that moves around a center of rotation (isocenter) in a single plane. Each time a radiation beam is delivered during treatment, the axis of the beam passes through the isocenter. In some gantry-based systems, known as intensity modulated radiation therapy (IMRT) systems, the cross-section of the beam is shaped to conform the beam to the pathological anatomy under treatment. In robotic-based systems, the radiation source is not constrained to a single plane of rotation. [0006] In image-guided systems, patient tracking during treatment is accomplished by registering two-dimensional (2-D) intra-treatment x-ray images of the patient (indicating where the patient is) to 2-D reference projections of one or more pre-treatment three-dimensional (3-D) volume studies of the patient (indicating where the patient should be to match the treatment plan). The pre-treatment 3-D volume studies may be computed tomography (CT) scans, magnetic resonance imaging (MRI) scans, positron emission tomography (PET) scans or the like. [0007] The reference projections (reference images), known as digitally reconstructed radiographs (DRRs) are generated using ray-tracing algorithms that replicate the geometry of the intra-treatment x-ray imaging system to produce images that have the same scale as the intra-treatment x-ray images. Typically, the intra-treatment x-ray system is stereoscopic, producing images of the patient from two different points of view (e.g., orthogonal views). [0008] As x-ray imaging technology advances, the sensitivity of the x-ray detectors used to capture the intra-treatment x-ray images is increasing. These increases are due, at least in part, to improved imaging materials (e.g., amorphous silicon) and image capture technologies (e.g., CCD and CMOS imaging arrays) and processing algorithms which reduce the quantum noise and electronic noise levels of the x-ray detectors and increase the signal-to-noise ratios of the intra-treatment x-ray images for any given imaging radiation level. Generally, a higher signal-to-noise ratio produces higher quality images that translate to improvements in image registration and patient tracking due to improved detectability of anatomical features and/or fiducial markers. For any given noise figure, the detectability of an anatomical object can be improved by changing x-ray properties. Two such changes can involve increasing the imaging radiation dose or energy to increase the SNR. FIG. 1 illustrates the improved detectability of an anatomical object 10 in a field of view 20 as the SNR is increased from 1:1 to 2:1 to 5:1 as the radiation dose is increased. X-ray sources used to generate intra-treatment x-ray images are typically set to dose and energy levels sufficient to penetrate larger patients and provide the required x-ray image quality (SNR level) for consistent and reliable tracking of patient and anatomical motion during setup and treatment. However, above a certain minimum SNR (e.g., 1:1), improvements in patient tracking and image registration may be offset by increased risks to the patient from higher radiation doses. BRIEF DESCRIPTION OF THE DRAWINGS [0009] Embodiments of the present invention are illustrated by way of example, and not by limitation, in the figures of the accompanying drawings in which: [0010] FIG. 1 illustrates x-ray detection as a function of signal to noise ratio. [0011] FIG. 2A illustrates an image-guided robotic radiosurgery system in one embodiment; [0012] FIG. 2B illustrates non-isocentric radiation treatment in one embodiment of an image-guided radiosurgery system; [0013] FIG. 3 is a flowchart illustrating a method in one embodiment of adaptive x-ray control; [0014] FIG. 4 illustrates treatment nodes in one embodiment of adaptive x-ray control; [0015] FIG. 5 is a flowchart illustrating a method in another embodiment of adaptive x-ray control; and [0016] FIG. 6 illustrates a system in which embodiments of the present invention may be practiced. DETAILED DESCRIPTION [0017] In the following description, numerous specific details are set forth such as examples of specific components, devices, methods, etc., in order to provide a thorough understanding of embodiments of the present invention. It will be apparent, however, to one skilled in the art that these specific details need not be employed to practice embodiments of the present invention. In other instances, well-known materials or methods have not been described in detail in order to avoid unnecessarily obscuring embodiments of the present invention. [0018] The term "coupled" as used herein, may mean directly coupled or indirectly coupled through one or more intervening components or systems. The term "x-ray image" as used herein may mean a visible x-ray image (e.g., displayed on a video screen) or a digital representation of an x-ray image (e.g., a file corresponding to the pixel output of an x-ray detector). The term "intra-treatment x-ray image" as used herein may refer to images captured at any point in time during the patient setup or treatment delivery phase of a radiosurgery or radiotherapy procedure, which may include times when the radiation treatment source is either on or off. Reference to an "x-ray image" may refer to a single image or a simultaneous or consecutive pair of images (as in a stereoscopic imaging system as described above). The term "IGR" as used herein may refer to image-guided radiotherapy, image-guided radiosurgery or both. A "target" as discussed herein may be an anatomical feature(s) of a patient such as a pathological anatomy (e.g., tumor, lesion, vascular malformation, nerve disorder, etc.) or normal anatomy and may include one or more non-anatomical reference structures. [0019] Unless stated otherwise as apparent from the following discussion, it will be appreciated that terms such as "processing," "computing," "determining," "estimating,""acquiring," "generating" or the like may refer to the actions and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (e.g., electronic) quantities within the computer system's registers and memories into other data similarly represented as physical within the computer system memories or registers or other such information storage, transmission or display devices. Embodiments of the method described herein may be implemented using computer software. If written in a programming language conforming to a recognized standard, sequences of instructions designed to implement the methods can be compiled for execution on a variety of hardware platforms and for interface to a variety of operating systems. In addition, embodiments of the present invention are not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement embodiments of the present invention. [0020] FIG. 2A illustrates the configuration of an image-guided, robotic-based radiation treatment system 100, such as the CyberKnife.RTM. Radiosurgery System manufactured by Accuray, Inc. of California. In FIG. 2A, the radiation treatment source is a linear accelerator (LINAC) 101 mounted on the end of a robotic arm 102 having multiple (e.g., 5 or more) degrees of freedom in order to position the LINAC 101 to irradiate a pathological anatomy (target region or volume) with beams delivered from many angles, in many planes, in an operating volume around the patient. Treatment may involve beam paths with a single isocenter, multiple isocenters, or with a non-isocentric approach. FIG. 2B illustrates non-isocentric radiation treatment in one embodiment. In FIG. 2B, a pathological anatomy (e.g., a tumor) 201 growing around a spinal cord (202) is treated for example, by radiation treatment beams 203, 204, 205 and 206, which each intersect the pathological target volume without converging on a single point, or isocenter, within the target). Continue reading about Adaptive x-ray control... Full patent description for Adaptive x-ray control Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Adaptive x-ray control patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Adaptive x-ray control or other areas of interest. ### Previous Patent Application: System and method for determining dimensions of structures/systems for designing modifications to the structures/systems Next Patent Application: Method for displaying a devise in a 3-d image of a volumetric data set Industry Class: X-ray or gamma ray systems or devices ### FreshPatents.com Support Thank you for viewing the Adaptive x-ray control patent info. IP-related news and info Results in 0.2716 seconds Other interesting Feshpatents.com categories: Medical: Surgery , Surgery(2) , Surgery(3) , Drug , Drug(2) , Prosthesis , Dentistry 174 |
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