TECHNIQUE FOR DYNAMIC ASSESSMENT OF PATIENT POSITION AND MOTION IN DIGITAL RADIOGRAPHY EXAMS
Publication Date: 2016-Feb-12
The IP.com Prior Art Database
A photogrammetry system and technique is proposed that enables patient positioning, collimation, and proper technique selection during digital radiographic exams. The technique described herein uses an optical photogrammetry system integrated into a collimator or an X-ray tube assembly of a conventional or mobile X-ray system. The photogrammetry system uses a light source, typically that used in an X-ray collimator for patient alignment or utilizes an additional light source. The light source is used to project a pattern of light on the object undergoing imaging. Given a known distance of the source to a patient barrier, magnification of the pattern is calculated and reference dimensions are known to the photogrammetry system. When an object is placed between the patient barrier and the pattern, magnification changes, thereby, resulting in a change of spacing of the grid pattern. A camera is used to detect the changes and estimate distance of surface of an object that is imaged from the patient barrier. Changes in shape or relative spacing of elements of the pattern indicate displacement of parts of the object relative to other parts.
The present invention relates generally to a digital radiography system and more particularly to a technique for dynamic assessment of patient position and motion during digital radiography exams.
Generally, high quality radiographs are difficult to obtain in a clinical setting and requires optimal equipment and appropriate selection of technical parameters. In addition, radiographs require proper positioning of a patient to ensure required anatomy is in a field of view, and in a relative orientation as expected by a radiologist to interpret an image.
A primary cause of poor quality images requiring repeated radiation exposures is insufficient or excessive dosage reaching an image receptor. A conventional technique utilizes automatic exposure control (AEC) device in fixed room radiographic systems. Such device enables considerable reduction in inappropriate exposure levels. However, inappropriate radiation exposure levels remain a challenge for mobile X-ray systems, where AEC devices are not typically used. Another conventional technique includes digital flat panel detectors having wide dynamic range. Such detectors reduce incidence of repeated radiography exams resulting from poor radiation exposure.
However, the above mentioned conventional techniques do not address problems arising from patient positioning, motion, collimation or poor technique selection by a technologist. In order to solve such problems, direct visual observation of the patient is commonly used. Further, conventional techniques do not enable accurate measurement of patient thickness, thereby, requiring the technologist to often manually estimate and enter patient size parameters. As a result, such conventional techniques result in errors or require selection of a generic technique to save time.
One other conventional technique uses a computer algorithm as a retrospective technique to determine information on a respiratory cycle from a series of images. However, the technique does not enable gating acquisition(s) according to the respiratory cycle or motion. Yet another conventional technique utilizes fiducial markers on skin of the patient to record motion during extended imaging exams, such as, computed tomography (CT) or radiation therapy treatments. However, the above mentioned conventional technique does not provide automated system to estimate or provide feedback on amount of raw radiation and anatomy to be exposed.
It would be desirable to have a technique to provide an automated system to assess patient position and motion in digital radiography exams.
BRIEF DESCRIPTION OF DRAWINGS
Figure 1 depicts a grid and other light patterns for photogrammetric analysis from a laser grid projection source of machine vision technology.
Figure 2 depicts a light emitting diode (LED) pattern projector machine vision technology that is used to project a grid or other light patt...