초록 ▼

In a subtraction angiography hybrid difference images are generated and reviewed visually. Hybrid images that exhibit no x-ray contrast medium and are free of artifacts are identified and selected for forming an integrated mask image. Hybrid images that exhibit contrast medium and are free of artifa

In a subtraction angiography hybrid difference images are generated and reviewed visually. Hybrid images that exhibit no x-ray contrast medium and are free of artifacts are identified and selected for forming an integrated mask image. Hybrid images that exhibit contrast medium and are free of artifacts are identified and selected for forming an integrated contrast medium image. The selected images that exhibit no contrast medium are integrated and those that exhibit contrast medium are integrated separately. The result of one integration is subtracted from the other to yield a single final image that exhibits substantially only the contrast medium in a blood vessel. In an alternate method temporal difference images are reviewed and a similar selection of some that exhibit no contrast medium and some that exhibit contrast medium is made. These images are separately integrated and subtracted to yield a single final image that exhibits substantially only contrast medium in the blood vessel.

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1. An integrated remasking method of producing data representative of an x-ray image of a blood vessel in a region of a body in a subtraction angiography procedure, the method comprising the following steps: repeatedly expose said body region containing said vessel to a low energy x-ray beam and

1. An integrated remasking method of producing data representative of an x-ray image of a blood vessel in a region of a body in a subtraction angiography procedure, the method comprising the following steps: repeatedly expose said body region containing said vessel to a low energy x-ray beam and a high energy x-ray beam in pairs and in either order during at least one of two periods, namely, a pre-contrast period when an x-ray contrast medium that has been introduced into said body has not yet arrived in said vessel and a period during which said medium has departed from said vessel, said periods being defined as non-contrast periods and the resulting images as non-contrast images, and maintaining said exposures during an intervening period when said medium is present in said vessel defined as the post-contrast period and the resulting images as the post-contrast images, convert the sequence of non-contrast and post-contrast x-ray images thus produced at high and low energy to data representative of the images, select the data for one of the low energy exposure images obtained during a non-contrast period as the low energy mask image data and select the data for one of the high energy exposure images obtained during a non-contrast period as the high energy mask image data, subtract the low energy mask image data from the respective data for the low energy exposure images in the sequence and subtract the high energy mask image data from the data for the high energy exposure images in the sequence to thereby provide a series of low energy temporal difference images data and a series of high energy temporal difference images data, perform energy subtraction comprising multiplying each of said low energy temporal difference images data, respectively, by a weighting coefficient and multiply each of said high energy temporal difference image data next to the low energy temporal difference image data in the series respectively by a different weighting coefficient and subtract the low energy temporal difference image from the high energy temporal difference image data, respectively, to thereby provide a series of first order hybrid difference images data extending over at least one of the non-contrast periods and over the post-contrast period, display one after another of the images that correspond to the first order hybrid difference images data and observe the images for identifying and selecting those first order hybrid non-contrast images that are of suitable quality to be used for forming new integrated mask image data and those post-contrast images that have contrast medium in them and are suitable for forming new integrated post-contrast image data, integrate the sequence of first order hybrid difference images data corresponding to the hybrid difference images that have been identified as usable to form the new mask image data and separately integrate the sequence of hybrid difference images data corresponding to the hybrid difference images that have been identified as usable to form new post-contrast image data, multiply the image data resulting from at least one of the two integrations by a scaling coefficient to normalize the brightness levels of the data in those cases where the number of images selected for the new integrated mask image differs from the number selected for the new post-contrast image and do not multiply by a scaling coefficient if the number of mask images and post-contrast images selected are equal, and subtract the integrated mask hybrid image data and the integrated hybrid post-contrast image data to produce final data which contains only the data representative of an image of the contrast medium in said blood vessel. 2. An integrated remasking method of producing data representative of an x-ray image of a blood vessel in a region of a body in a subtraction angiography procedure, the method comprising the following steps: repeatedly expose said body region containing said vessel to a low energy x-ray beam and a high energy x-ray beam in pairs and in either order during at least one of two periods, namely, a pre-contract period when an x-ray contrast medium that has been introduced into said body has not yet arrived in said vessel and an after post-contrast period during which said medium has departed from said vessel, said periods being defined as non-contrast periods and the resulting images as non-contrast images, and perform said exposures during an intervening period when said medium is present in said vessel defined as the post-contrast period and the resulting images as the post-contrast images, convert the sequence of x-ray images thus produced at high and low energy to data representative of the images, store the data for one of the low energy exposure images obtained during a non-contrast period as the low energy mask image data and store the data for one of the high energy exposure images obtained during said period as the high energy mask image data, for every other low and high energy exposure in the sequence subtract the low energy mask image data from the image data resulting from each low energy exposure and alternately subtract the high energy mask image data from the image data resulting from each high energy exposure and store the resulting series of alternate low and high energy temporal difference images data, repeatedly access from storage concurrently the data for one low energy temporal difference image and the data for one high energy temporal difference image that is next to it in the series and multiply the low energy temporal difference images data by one weighting coefficient and multiply the high energy temporal difference images by a different weighting coefficient, repeatedly subtract the low energy weighted temporal difference data and the high energy weighted temporal difference image data next to it in the exposure sequence to thereby produce a series of hybrid images data, display the images represented by the series of hybrid images data one after another as they are produced for enabling identification and selection by visual observation those non-contrast images that are suitable for forming new integrated mask image data and those post-contrast images that have contrast medium in them and are suitable for forming new integrated post-contrast image data, then re-access successive pairs of low and high energy temporal difference images data from storage and reproduce hybrid difference images data again by performing the steps previously set forth, integrate the reproduced hybrid difference images data corresponding to the hybrid difference images that have been identified as usable to form the new mask image data and separately integrate the hybrid difference images data corresponding to the hybrid difference images that have been identified as usable to form new post-contrast image data, multiply the image data resulting from at least one of the two integrations to normalize the brightness levels of the data in those cases where the selected number of images selected for the new integrated mask image differs from the number selected for the new post-contrast image and do not multiply by a scaling coefficient if the number of mask images and post-contrast images selected are equal, and subtract the integrated mask image data and the integrated post-contrast image data to produce a final data set which contains only the data representative of an image of the contrast medium in said blood vessel. 3. The method in accordance with any of claims 1 or 2 including the step of: varying the value of selected ones of said weighting coefficients by which said low and high energy temporal difference images are being multiplied as aforesaid while the image corresponding to the resulting hybrid image data is being displayed and continuing said varying until cancellation of motion or other artifacts remaining in the pairs of low and high energy temporal difference images such that only contrast medium in the hybrid image remains after said energy subtraction. 4. The method in accordance with any one of claims 1 or 2 including the step of amplifying logarithmically the data representative of the images resulting from the low and high energy exposures as the respective image data are acquired. 5. An integrated remasking method of producing data representative of an x-ray image of a blood vessel in a region of a body in a subtraction angiography procedure, the method comprising the following steps: repeatedly expose said body region containing said vessel to a low energy x-ray beam and a high energy x-ray beam in pairs and in either order during two periods, namely, a pre-contrast period during which an x-ray contrast medium that has been introduced into said body has not yet arrived in said vessel and an after-post-contrast period during which said medium has departed from said vessel, said periods being defined as non-contrast periods and the resulting images as non-contrast images, and also performing said pairs of exposures during an intervening period when said contrast medium is present in said vessel defined as the post-contrast period and the resulting images as the post-contrast images, convert the sequence of x-ray images thus produced at high and low energy exposures to data representative of the respective images, repeatedly throughout the sequence multiply the data representative of an image acquired with each low energy exposure in each pair by a weighting coefficient and multiply the data representative of an image acquired with each high energy exposure in the same pair by a weighting coefficient and subtract the weighted high energy images data from the low energy weighted images data composing the pair to yield a series of energy difference images data comprised of non-contrast and post-contrast images, store said series of energy difference images data, sequentially access from storage said energy difference image data and subtract them from the first energy difference image data in the sequence which serves as a mask to thereby produce a sequence of hybrid images data, display the images represented by the hybrid image data one after another as they are produced for enabling by visual observation of the images, identification and selection of those non-contrast images that are suitable for forming new integrated mask image data and those post-contrast images that have perceptible contrast medium in them and are suitable for forming new integrated post-contrast image data, integrate the energy difference image data that have been identified and selected as being usable to form a new mask image data and separately integrate the energy difference image data that have been selected as being usable to form new post-constrast image data, multiply the image date resulting from at least one of the two integrations by a coefficient to normalize the brightness levels in those cases where the number or images selected for the integrated mask image differs from the number selected for the integrated post-contrast image and do not multiply by a coefficient if the number of images selected for the integrated mask and integrated post-contrast image are equal, and subtract the integrated mask image data and the integrated post-contrast image data to achieve hybrid subtraction and produce final data which contains the data representative of an image of the contrast medium in the vessel. 6. The method in accordance with claim 5 including the step of amplifying logarithmically the data representative of the images resulting from the low and high energy exposures as the data are aquired. 7. An integrated remasking method of producing data representative of an x-ray image of a blood vessel in a region of a body in a subtraction angiography procedure, the method comprising the following steps: repeatedly expose said body region containing said vessel to a low energy x-ray beam and a high energy x-ray beam in pairs and in either order during two periods, namely, a pre-contrast period during which an x-ray contrast medium that has been introduced into said body has not yet arrived in said vessel and an after post-contrast period during which said medium has departed from said vessel, said periods being defined as non-contrast periods and the resulting images an non-contrast images, and perform said pairs of exposures during an intervening period when said medium is present in said vessel defined as the post-contrast period and the resulting images as the post-constrast images, convert the sequences of x-ray images as they are acquired at high and low energy to data representative of the respective images and store these images data, access from storage the data for one of the low energy exposure images obtained during the pre-contrast period as the low energy mask image data and access the data for one of the high energy exposure images obtained during said period as the high energy mask image data, subtract the low energy mask image data from the respective successive low energy exposure images in the sequence and subtract the high energy mask image data from the data for the respective successive high energy exposure images in the sequence to thereby provide a series of low energy temporal difference images data and a series of high energy temporal difference images data, perform energy subtraction by the steps of multiplying any low energy temporal difference image data by a weighting coefficient and multiplying the high energy temporal difference image data in the same exposure pair as said low energy temporal difference image data by a different weighting coefficient and subtract the data resulting from one multiplication from the data resulting from the other multiplication and by repeating these steps for each pair of low energy and high energy temporal difference images provide a series of first order hybrid difference images data extending over at least the pre-contrast and post-contrast periods, displaying one after another of the images that correspond to the first order hybrid difference images data for identifying and selecting, by visual observation, those non-contrast images that are suitable for forming a new integrated mask image and those post-contrast images that are suitable for forming a new integrated post-contrast image, integrating the first order hybrid difference images data corresponding to the hybrid difference images that have been identified and selected as usable to form the new mask image data and separately integrating the hybrid difference images data corresponding to the hybrid difference images that have been identified and selected as usable to form new post-contrast image data, multiply the image data resulting from at least one of the two integrations by a scaling coefficient to normalize the brightness levels of the data in those cases where the selected number of images selected for the new integrated mask image differs from the number selected for the new post-constrast image and do not multiply by a scaling coefficient if the numbers of images composing the new integrated mask image and the new integrated post-contrast image are equal, and subtract the integrated mask image data and the integrated post-contrast image data to produce final image data which contains only the data representative of an image of the contrast medium in said blood vessel. 8. The method in accordance with claim 7 including the step of amplifying logarithmically the data resulting from the low and high energy exposures as the respective images data are acquired. 9. The method in accordance with any one of claims 7 or 8 including the step of varying the value of the weighting coefficients by which said low and high temporal difference images are being multiplied while the image corresponding to the resulting hybrid difference image is being displayed and by visual observation of the displayed images choosing for final use the weighting coefficients that result in cancellation of motion of other artifacts found in a pair of low and high energy temporal difference images so that only the data representative of said contrast medium that defines the interior of the blood vessel remains after energy subtraction. 10. An integrated remasking method of producing data representative of an x-ray image of a blood vessel in a region of a body in a subtraction angiography procedure, the method comprising the following steps: repeatedly expose said body region containing said vessel to a low energy x-ray beam and a high energy x-ray beam in pairs and in either order during at least one of two periods, namely, a pre-contrast period during which an x-ray contrast medium that has been introduced into said body has not yet arrived in said vessel and an after-post-contrast period during which said medium has departed from said vessel, said periods being defined as non-contrast periods and the resulting images as non-contrast images, and performing said pairs of exposures during an intervening period when said medium is present in said vessel defined as the post-contrast period and the resulting images as the post-contrast images, convert the sequence of x-ray images resulting from the exposures at high and low energy to data representative of the respective images, form a series of images data representative of hybrid difference images by performing the steps of selecting one of the low energy non-contrast images data as the mask image data and subtract the mask image data from each subsequent low energy image data in the exposure sequence and select one of the high energy non-contrast images data as the high energy mask image data in the same exposure pair as the low energy mask and subtract the high energy mask image data from each subsequent high energy images data in the exposure sequence to thereby provide for producing a series of alternate low energy temporal difference images data and high energy temporal difference images data, multiply the low energy temporal difference images data and the high energy temporal difference images data in the same exposure pairs as they are produced by different weighting coefficients, respectively, and subtract the weighted images data to produce a series of hybrid difference images data and store each hybrid image data as it is produced, access from storage one after another of the hybrid difference images data and use these data to effect a display of the corresponding hybrid images for selection by visual inspection of the displayed images, and identification of those non-contrast hybrid images which are of suitable quality for forming a new integrated mask and those post-contrast hybrid images that are suitable for forming an integrated post-contrast image, integrate the hybrid difference images corresponding to those that have been selected to form the new mask and separately integrate those that have been selected to form a new post-contrast image, and subtract one resulting integrated image data from the other to yield a final image data that contains only the data representative of the contrast medium in said vessel. 11. The method in accordance with claim 10 wherein said series of hybrid image data are formed by the multiplying the images data resulting from the first non-contrast low energy exposure by a weighting coefficient and multiplying the images data resulting from the non-contrast high energy exposure in the same pair of exposures by a weighting coefficient and subtracting one of the weighted images data from the other to produce an energy subtraction mask image data, and multiplying the images data resulting from each subsequent low energy exposure by a weighting coefficient and multiplying the images data resulting from the high energy exposure in the same pair of exposures by a different weighting coefficient and subtracting one of the weighted images data from the other to produce a second energy subtraction image data, subtracting said second energy subtraction data from said energy subtraction mask image data to produce a hybrid image data for storage, and repeating the last-mentioned weighting and subtracting steps for all of the low and high energy exposure pairs in said sequence. 12. The method in accordance with any one of claims 10 or 11 wherein the data representative of the respective images resulting from the x-ray exposures are amplified logarithmically as these data are acquired and before performing the steps for producing the hybrid images data.