Method and apparatus for calibrating rapid sequence radiography
OwnerJames R. Spearsinventor
Life of this patent
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Abstract
By moving a wedge (18) within the radiographic field during exposure of an area of interest, steps of the wedge are presented one by one at the same film location over sequential exposures. Wedge steps are thus superimposed over an identical position within the radiographic field, and a correlation may then be made between wedge step thickness and film optical density over successive exposures for calibrating the radiographs. A preferred form of the stepped wedge is circular (FIG. 2). An alternate form is a circular ramp (FIG. 3).
Claims10
A method for calibrating rapid sequence radiography comprised of the steps of
- positioning a movable wedge of radio-dense material in the field of interest between an x-ray source and cinematic photography means,
- moving said wedge in synchronism with said cinematic photography means to place successive portions of said wedge over a constant position in said field to change the thickness of radio-dense material of said wedge over said position for each frame of said cinematic radiography,
- recording on cinematic film each successive frame of said radiography,
- developing said film,
- projecting each successive frame of said developed film,
- detecting the intensity of light at a constant position of each projected frame corresponding to said constant position of said wedge in said field,
- from the intensity data developing a calibration curve relating light intensity to thickness of said wedge in said field of interest, and
- from said calibration curve translating intensity data at any position within said field into equivalent thickness of said wedge.
Apparatus for calibrating cinematic radiography comprised of
- a radiation generator,
- cinematic photographing means positioned to produce a cinematic radiograph, one frame at a time in succession of a field of interest in a patient,
- a wedge of known radio-dense material positioned in said field of interest between said patient and photographing means,
- means for moving said wedge in synchronism with said cinematic photography means to place a portion of said wedge over a constant position in said field to change the thickness of radio-dense material of said wedge for each frame of said cinematic radiography,
- means for projecting each successive frame of said cinematic radiography, and
- means for detecting the intensity of light at a constant position for each projected frame corresponding to said constant position of said wedge in said field, whereby a calibration curve relating light intensity to thickness of said wedge in said field of interest may be developed.
Dependencies are inferred from the claim text.