Abstract: A digital image processing method automatically separates (segments) the desired regions in a digital radiographic image (i.e., the body part being imaged) from the undesired regions (background areas around the body part that have received unattenuated radiation or foreground areas that have received very little radiation due to the use of radiation limiting devices). The method includes the steps of edge detection, block generation, block classification, block refinement and bit map generation.

Abstract: A method and apparatus for automatically and adaptively generating tonescale transformation functions that are robust with respect to imaging systems, exposure conditions, and body parts. The technique uses the histogram of the digital input image, the cumulative distribution function of the histogram, and the entropy of subsections of the histogram to create the final tonescale transformation. Using these three functions, the histogram can be divided into a region of interest, a low-signal foreground region, and a high-signal background region. The tonescale is constructed to be substantially linear over the region of interest, joining smoothly with a nonlinear portion extending from the end of the low-signal foreground region to the start of the region of interest, and another nonlinear portion of the high-signal background region. The substantially linear region of interest and the entire image are subject to certain output density constraints to optimize the diagnostic utility of the final image.

Abstract: In storage phosphor radiography, a portion of the x-ray energy transmitted through the subject is absorbed by a storage phosphor plate. When stimulated by visible light of the right wavelength, the phosphor plate emits light (at another wavelength) in proportion to the absorbed energy. To obtain the radiographic image, the plate can be scanned in a raster fashion and the emitted light can be photoelectrically detected. The detected signal is then amplified, digitized, processed and finally printed on film, or displayed on a cathode ray tube (CRT). Setting the amplification gain of this scanning process, the so-called final scan (or final read-out) gain, is of interest in maximizing the information extracted from the phosphor. One method of setting the final scan gain invokes the use of a preliminary read-out (pre-scan). A pre-scan can be conducted on the phosphor plate by use of a stimulating ray having a stimulating energy lower than the stimulating energy in the final scan.

Abstract: A phototimer for controlling x-ray exposure includes an array of x-ray sensors, and digital processing electronics for calculating x-ray exposure by selecting one or more signals from the x-ray sensors, and calculating the x-ray exposure from the selected signals. After calculating the x-ray exposure, the calculated exposure is employed to control the x-ray exposure either by displaying the calculated exposure to an operator who compares the calculated exposure with a desired exposure and repeats the exposure if necessary, or by automatically terminating the exposure by sending a control signal to the x-ray source. The improvement in the state of x-ray phototimer technology resides in the automatic selection of a subset of signals from a plurality of photosensors, thereby improving the reliability of the measurement. In prior art devices, the signals from a plurality of sensors were either selected manually by a switch, or all employed in a predetermined algorithm.

Abstract: In any digital imaging system, the digital input signals must be converted to a visible image on some output material or medium. Because the range of this output medium is usually not the same as the input image range, care must be taken in converting the digital input signals into output signals. This conversion is done via the tone-scale transformation function. The type of tone-scale transformation function used largely determines the quality of the output image. A well designed tone-scale transformation function must ensure good contrast, no clipping and the display of the minimum and maximum densities that are present in the input. This invention deals with a reliable and robust technique of generating the tone-scale transformation function for digital projection X-ray input images. The method is based on the histogram entropy of the input image.

Abstract: In many digital image processing methods, it is desirable to selectively apply digital image processing to identifiable structures in the image. For this purpose it is known to select gray level thresholds between structures based upon the location of corresponding peaks in the gray level histogram of the digital image. However, it is a problem to automatically detect the locations of peaks in the histogram and to select the gray level thresholds. The present invention provides a method for automatically detecting the peaks and selecting gray level thresholds for segmenting a digital image into distinguishable structures including the steps of detecting peaks in a gray level histogram of the digital image by applying smoothing and differencing operators to the gray level histogram to generate a peak detection function wherein positive to negative zero crossings of the peak detection function represent the start of a peak, and maxima following such a zero crossing represents the end of a peak.