When tomorrow comes: computerized decision making.
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Humans↗
Biomedical subjects
R A Kruger
Publications and source records attributed to R A Kruger.
Digital radiography.
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Analog-Digital Conversion↗
Cross-sectional area measurements by digital subtraction videodensitometry.
A method for measurement of absolute cross-section areas in digital images of iodine-opacified vessels was tested in phantoms containing "normal" segments of circular cross-section and either circular or noncircular "stenoses" over a wide range of iodine concentrations. Accuracy varied with iodine concentration, with a slight tendency to overestimate the area at high concentration (185 mg I/ml) and to underestimate at low concentration (23 mg I/ml). Reproducibility was improved at the higher concentrations, with standard deviation ranging from 2% to 7% of the measured value, compared with 7% to 27% at the lowest concentration. Accuracy and reproducibility of area measurements on either normal or stenotic segments were unchanged by rotation of the vessel by up to 25 degrees out of the plane of the image. This method is easily implemented using computerized image processing techniques and has advantages over either manual or automated edge detection because it eliminates the need for an edge criterion and is independent of the viewing projection.
Absorptiometry, Photon↗
Digital subtraction coronary angiography using high-pass temporal filtration: a comparison with cineangiography.
Selective coronary angiograms were obtained using a real-time high-pass temporal filtration digital subtraction technique with videotape storage and display and compared to simultaneously recorded 35-mm cineangiograms for 32 stenotic lesions in 15 patients. Both methods were evaluated by three independent observers using caliper measurement of percent diameter reduction for each lesion. There was a good correlation between the two imaging methods for individual observers, though considerable variability was seen, r = .73, standard error of estimate (SEE) = 9.1%. The average severity of stenosis and the interobserver variability were similar between methods. This digital subtraction technique for selective coronary angiography compares favorably with a conventional film-based technique for evaluation of coronary stenoses and offers advantages of real-time image processing, limited tolerance to patient motion, and relatively small digital memory requirements. In addition to further improvements in image quality, more objective computer-aided scoring methods are needed to reduce the variability in lesion analysis.
Angiography↗
Vessel diameter measurement using digital subtraction radiography.
A method for obtaining absolute diameter and cross-sectional area measurements on subtraction digital images is described and tested in phantom vessels from 1.5 to 5.5 mm in diameter filled with iodine contrast at concentrations from 23 to 185 mg I/ml. A highly linear correlation of true vs. calculated diameter is demonstrated, with accuracy and reproducibility of the method varying from +/- 1% to 2% at the highest iodine concentration to +/- 30% in the smallest tube at the lowest concentration. A method is described for correction of the observed video density values to allow for nonlinearity of response of the imaging system to iodine density, and its effect on the measured diameters is demonstrated.
Angiography↗
Digital angiography: matched filtration versus mask-mode subtraction.
Matched filtration was compared to mask-mode subtraction in patients undergoing routine intravenous digital subtraction angiography. Images were analyzed for noise and edge sharpness, and the two techniques were compared subjectively by three radiologists. The quantitative results indicated that matched filtration increased the signal-to-noise ratio by an average of 2.23 but did not significantly increase vessel blurring. Subjectively, the observers favored matched filtration over mask-mode subtraction for overall image quality in 26 out of 30 cases (p less than 0.005) in terms of both sharpness and freedom from motion artifacts.
Angiography↗
Tomographic digital subtraction angiography: initial clinical studies using tomosynthesis. Work in progress.
We have developed a method for acquiring multiple tomographic subtraction images using a rapid, repetitive, circular tomographic motion. The method combines the principles of digital subtraction angiography (DSA) and electronic tomosynthesis. Fifteen patients were examined with the technique using single intravenous bolus injections of contrast material. The image sequence obtained during each injection was first processed with a nontomographic mask subtraction, and the result was then compared with the tomographic DSA scans synthesized from the same sequence. The effective section thickness was approximately 0.5 cm, with each section being 0.5-1.0 cm apart. Twelve of the intravenous DSA scans provided the necessary diagnostic or clinically useful information. Two of the three nondiagnostic scans were caused by avoidable technical reasons. In eight cases, the tomographic DSA scans were superior in quality to the nontomographic scans, exhibited significantly less artifact from patient motion and overlying bowel gas, and were effective in separating overlapping vessels. Tomosynthesis permits multiple electronic imaging of the area of interest without reinjection of contrast material and appears to be more informative than nontomographic intravenous DSA imaging.
Angiography↗
Computerized tomographic determination of vertebral density after total hip arthroplasty.
Computerized tomography (CT) provides the capability to determine vertebral bone density with a high degree of accuracy and precision, detecting density changes as small as 5% in serial testing. In this pilot study, CT was used to determine the effects of total hip arthroplasty and its consequent alterations in physical activity levels on the vertebral bone density of 13 postoperative patients. Vertebral bone density was also evaluated in six preoperative patients with degenerative joint disease of the hip and five control patients. The preoperative group and controls were then compared with the postoperative patients, who were divided into two groups--those who had achieved good activity levels and those whose levels of activity remained poor. CT measurement of bone density in the central bodies of T12, L1, and L2 showed that the preoperative group was similar to controls. This suggests that patients accept total hip arthroplasty rather than endure significant activity limitations for extended periods of time. When activity level was restored by arthroplasty, vertebral bone density was preserved. If the patient continued at a poor activity level postoperation, significant loss of bone density occurred secondary to disuse.
Aged↗
Real-time digital angiocardiography using a temporal high-pass filter.
A temporal high-pass filtration technique for digital subtraction angiocardiography was studied, using real-time digital studies performed simultaneously with routine cineangiocardiography (cine) for qualitative image comparison. The digital studies showed increased contrast and suppression of background anatomy and also enhanced detection of wall motion abnormalities when compared with cine. This digital technique is compatible with panning the image intensifier during an injection. The digital images are comparable with, and in some cases better than, cine images. Clinical efficacy of this digital technique is currently being evaluated. Real-time display, as well as potential reductions in radiation and contrast material doses, may make digital angiocardiography an attractive technique.
Angiocardiography↗
Tomosynthesis applied to digital subtraction angiography.
This extension of our previous work on tomographic digital subtraction angiography (DSA) describes the theory of tomosynthetic DSA image reconstruction techniques. In addition to developing the resolution limits resulting from x-ray exposure length and image intensifier field curvature, we describe one method of image formation and show tomosynthetic DSA images of animal and human anatomy. Methods for improving the present technique are discussed.
Angiography↗
Digital angiography.
The many available methods of digital subtraction angiography (DSA) are briefly reviewed. At present the most commonly used are temporal filtration techniques, which include conventional subtraction, integrated remasking , and various types of filtering. Their present use in intravenous, as well as intra-arterial, DSA is shown. The "moving mask" subtraction technique for cardiac and coronary studies is of particular interest. The current status of second-order subtraction techniques such as tomographic DSA and parametric digital imaging is presented. The latter method is particularly useful for demonstration of shunts. Finally, several examples of non-angiographic and future applications of digital radiography are presented.
Angiography↗
Image data acquisition, processing, storage and display.
It is important to optimize each stage of image formation to minimize and take the greatest advantage of X-ray dose used. For each stage (acquisition, processing, and display) an optimum exists within the limits of physical laws and current technology. These laws must be understood and the technologic limitations imposed by them appreciated to acquire the maximum information from digital subtraction angiography (DSA) examinations.
Angiography↗
Intravenous digital subtraction: a summary of recent developments.
Recent developments in digital subtraction angiographic imaging are discussed. The technical characteristics of several alternate subtraction methods are reviewed, including integrated remasking, matched filtering, recursive filtering, hybrid subtraction, and tomographic digital subtraction angiography (DSA). The properties that each exhibits are compared with conventional DSA imaging, and the major expected limitations and applications of each technique are discussed.
Angiography↗
Dynamic tomographic digital subtraction angiography using temporal filtration.
A variation of temporal recursive filtering for intravenous and intra-arterial digital subtraction angiography (DSA) is described. It results in a dynamic tomographic DSA display that may improve intravenous DSA performance by removing the confusion introduced by vessel overlap and reducing the severity of motion artifacts. A conventional circular tomographic apparatus was modified by the addition of a 23-cm image intensifier-television chain and made to run continuously at one revolution each 1.5 seconds. The video output was processed by the recursive filter in a two-step process resulting in a dynamic tomographic display of arterial opacification. Theory and results of initial animal studies are presented.
Angiography↗
Clinical intra-arterial digital subtraction imaging. Use of small volumes of iodinated contrast material or carbon dioxide.
Forty patients were examined with intra-arterial digital subtraction angiography (DSA) using meglumine iothalamate (202 mg iodine/ml) or CO2 as a contrast medium. Diagnostic studies were obtained in all patients. The use of CO2 resulted in diagnostic examinations of the common femoral artery to the level of the trifurcation. The use of CO2 and low-iodine-content contrast material reduced the iodine dosage, and temporal bandpass filtration DSA permitted a lower entrance exposure than pulsed systems. It is concluded that intra-arterial DSA, using the techniques described in this paper, will become a more important and widely used procedure than it currently is.
Angiography↗
Blood flow determination using recursive processing: a digital radiographic method.
Temporal filtration of fluoroscopic video sequences is being used as an alternative to pulsed digital subtraction angiography. Using the same image processing architecture and a slight modification in processing logic a parametric image can be synthesized from such a temporally filtered image sequence in virtual real time, i.e., an image sequence that spans T seconds takes exactly T seconds to process. Off-line computer processing is not required. Initial phantom studies imply that the time to maximum opacification (tmax) can be used to determine absolute and relative blood flow with a high confidence level (r greater than .989). Phantom and animal examples are presented.
Angiography↗
Digital subtraction angiography using a temporal bandpass filter: initial clinical results.
A dual digital memory recursive filtering system provides an effective alternative to digital subtraction imaging by using routine fluoroscopic equipment operated with slightly elevated fluoroscopic technical factors. This is accomplished with relatively inexpensive portable electronic equipment that can be connected to the video output of most modern fluoroscopic systems. Initial clinical experimental studies suggest that the system can produce diagnostic images comparable with pulsed fluoroscopic digital systems. The temporal filtering approach offers a real-time vascular imaging technique that requires no postprocessing and can be used either with arterial or intravenous injections of contrast materials.
Adult↗
Digital subtraction angiography using a temporal bandpass filter: associated patient motion properties.
A system for performing real-time digital angiography both intraarterially and intravenously is described. A filtering process, rather than mask subtraction produces diagnostic-quality angiograms using existing fluoroscopic x-ray systems operated continuously (30 frames/sec) at less than 70 kVp and 20 mA. The image degradation effects of patient motion (breathing, swallowing, sudden movement) are dealt with differently from a subtraction approach. Certain periodic patient motions can be accommodated without the need for postprocessing. An analysis of experimental and clinical results of intravenous angiographic studies is presented, with emphasis on patient motion properties.
Angiography↗