Data processing: structural design – modeling – simulation – and em – Electrical analog simulator – Of physical phenomenon
Reexamination Certificate
2000-09-22
2004-06-08
Broda, Samuel (Department: 2123)
Data processing: structural design, modeling, simulation, and em
Electrical analog simulator
Of physical phenomenon
C382S210000, C382S276000, C345S426000
Reexamination Certificate
active
06748347
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention generally relates to digital data processing, and more particularly, to a method and apparatus for rapid evaluation of digital data processing parameters.
BACKGROUND OF THE INVENTION
A hologram is a three-dimensional record, (e.g., a film record) of a physical system which, when replayed, produces a true three-dimensional image of the system. Holography differs from stereoscopic photography in that a holographic image exhibits full parallax by affording an observer a full range of viewpoints of the image from every angle, both horizontal and vertical, and full perspective (i.e. it affords the viewer a full range of perspectives of the image from every distance from near to far). A holographic representation of an image thus provides significant advantages over a stereoscopic representation of the same image. This is particularly true in medical diagnosis, where the examination and understanding of volumetric data is critical to proper medical treatment.
While the examination of data which fills a three-dimensional space occurs in all branches of art, science, and engineering, perhaps the most familiar examples involve medical imaging where, for example, Computerized Axial Tomography (CT or CAT), Magnetic Resonance (MR), and other scanning modalities are used to obtain a plurality of cross-sectional images of a human body part. Radiologists, physicians, and patients observe these two-dimensional data “slices” to discern what the two-dimensional data implies about the three-dimensional organs and tissue represented by the data. The intergration of a large number of two-dimensional data slices places great strain on the human visual system, even for relatively simple volumetric images. As the organ or tissue under investigation becomes more complex, the ability to properly integrate large amounts of two-dimensional data to produce meaningful and understandable three-dimensional mental images may become overwhelming.
Presently known modalities for generating volumetric data corresponding to a physical system include, inter alia, computerized axial tomography (CAT or CT) scans, magnetic resonance scans (MR), three-dimensional ultra sound (US), positron emission tomography (PET), and the like. Although a preferred embodiment of the present invention is described herein in the context of medical imaging systems which are typically used to investigate internal body parts (e.g., the brain, spinal cord, and various other bones and organs), those skilled in the art will appreciate that the present invention may be used in conjunction with any suitable data set defining any three-dimensional distribution of data, regardless of whether the data set represents a physical system, e.g., numerical, graphical, and the like.
Typical data sets comprise on the order of 10 to 70 (for CT systems) or 12 to 128 (for MR) two-dimensional data slices
14
. Those skilled in the art will appreciate that the thickness and spacing between data slices
14
are configurable and may be adjusted by the CT technician. Typical slice thicknesses range from 1.5 to 10 millimeters and most typically approximately 5 millimeters. The thickness of the slices is desirably selected so that only a small degree of overlap exists between each successive data slice.
The data set corresponding to a CT or MR scan is typically reproduced in the form of a plurality (e.g., 50-100) of two-dimensional transparent images which, when mounted on a light box, enable the observer (e.g., physician) to view each data slice. By reviewing a plurality of successive data slicers
14
, the observer may construct a three-dimensional mental image or model of the physical system within volume
16
. The accuracy of the three-dimensional model constructed in the mind of the observer is a function of the level of skill, intelligence, and experience of the observer and the complexity and degree of abnormality of the body parts within volume
16
.
In addition to the use of an angled gantry, other techniques may be employed to produce a data set in which a plane of each data slice is not necessarily parallel to the plane of every other data slice, or not necessarily orthogonal to the axis of the data set; indeed, the axis of the data set may not necessarily comprise a straight line. For example, certain computerized techniques have been developed which artificially manipulate the data to produce various perspectives and viewpoints of the data, for example, by graphically rotating the data. In such circumstances, it is nonetheless possible to replicate the three-dimensional data set in the context of the present invention. In particular, by carefully coordinating the angle at which the object beam is projected onto the film, the plane of a particular data slice may be properly oriented with respect to the plane of the other data slices and with respect to eh axis of the data set, for example by tilting screen 326 about its horizontal or vertical axis. Presently known CT scan systems generate data slices having a resolution defined by, for example, a 256 or a 512 square pixel matrix. Furthermore, each address within the matrix is typically defined by a twelve bit grey level value. CT scanners are conventionally calibrated in Houndsfield Units whereby air has a density of minus 1,000 and water a density of zero. Thus, each pixel within a data slice may have a grey level value between minus 1,000 and 3,095 (inclusive) in the context of a conventional CT system. Because the human eye is capable of simultaneously perceiving a maximum of approximately one hundred (100) grey levels between pure white and pure black, it is desirable to manipulate the data set such that each data point within a slice exhibits one (1) of approximately fifty (50) to one hundred (100) grey level values (as opposed to the 4,096 available grey level values). The process of redefining these grey level values is variously referred to as “windowing”.
The present inventor has determined that optimum contrast may be obtained by windowing each data slice in accordance with its content. For example, in a CT data slice which depicts a cross-section of a bone, the bone being the subject of examination, the relevant data will typically exhibit grey level values in the range of minus 600 to 1,400. Since the regions of the data slice exhibiting grey level values less than minus 600 or greater than 1,400 are not relevant to the examination, it may be desirable to clamp all grey level values above 1,400 to a high value corresponding to pure white, and those data points having grey level values lower than minus 600 to a low value corresponding to pure black.
As a further example, normal grey level values for brain matter are typically in the range of about 40 while grey level-values corresponding to tumorous tissue may be in the 120 range. If these values were expressed within a range of 4,096 grey level values, it would be extremely difficult for the human eye to distinguish between normal brain and tumorous tissue. Therefore, it may be desirable to clamp all data points having grey level values grater than, e.g., 140 to a very high level corresponding to pure white, and to clamp those data points having grey scale values of less than, e.g. minus 30, to a very low value corresponding to pure black. Windowing the data set in this manner contributes to the production of sharp, unambiguous holograms.
In addition to windowing a data set on a slice-to-slice basis, it may also be advantageous, under certain circumstances, to perform differential windowing within a particular slice, i.e. from pixel to pixel. For example, a certain slice or series of slices may depict a deep tumor in a brain, which tumor is to be treated with radiation therapy, for example by irradiating the tumor with one or more radiation beams. In regions which are not to be irradiated, the slice may be windowed in a relatively dark manner. In regions which will have low to mid levels of radiation, a slice may be windowed somewhat more brightly. In regions of a high concentration of radiat
Broda Samuel
Phan Thai
Snell & Wilmer L.L.P.
Voxel, Inc.
LandOfFree
Method and apparatus for rapidly evaluating digital data... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for rapidly evaluating digital data..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for rapidly evaluating digital data... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3365403