Balloon dilation angioplasty for coarctation of the aorta.

Eleven patients with coarctation of the aorta (C of A) underwent balloon dilation angioplasty at the University of Arizona from November 1983 to January 1985. Eight had previously undergone surgery and 3 had native C of A. Two operations were considered unsuccessful: 1 in a patient who underwent tube graft--descending aortic anastomosis narrowing and 1 in a patient with a native wedge type of C of A. Overall mean gradient fell from 47 to 13 mm Hg immediately after the procedure. Mean gradient at repeat catheterization in 7 patients (mean 8 months after angioplasty) was 6 mm Hg. Five patients showed a transient increase in the gradient measured on the day after angioplasty, with 3 showing a fairly marked increase. Values returned to levels equal to or less than gradients measured immediately after the procedure. Angiographic findings at follow-up catheterization in 7 patients showed no evidence of aneurysm formation in either the operative group or in the 2 patients with native C of A who had a membrane type of deformity. Mean C of A to ascending aortic diameter ratios increased from 0.44 to 0.80. At repeat angiography, the mean ratio was 0.76 in the 7 patients studied. Further longitudinal studies in these patients are necessary before reaching conclusions about the advantage of this procedure over surgery, but these early longitudinal results are encouraging for the populations studied: postoperative patients and patients with native membrane types of C of A.

Two dimensional echocardiography and intravenous digital video subtraction angiography for diagnosis and evaluation of double aortic arch.

Two infants and one 7 year old child with double aortic arch are described in whom subcostal two dimensional echocardiography identified the bifurcation of the aorta high within the thorax and imaged the proximal portions of the right and left aortic arches. In one of the infants and in the 7 year old child, the diagnosis was confirmed using intravenous digital video subtraction angiography, thus avoiding aortography and permitting accurate evaluation of the anatomic features. All cases were confirmed surgically. If X-ray examination after barium swallow and clinical history are suggestive of double aortic arch, two dimensional echocardiography is useful in verifying this possibility. Intravenous digital video subtraction angiography provides the capability for precise documentation of the anatomic features.

Cross-linked DTPA polysaccharides for magnetic resonance imaging. Synthesis and relaxation properties.

An attempt was made to develop a macromolecular paramagnetic contrast agent that would be easily and inexpensively synthesized, low in toxicity, and quickly eliminated from the body after completion of the desired imaging studies. Under more rigorous conditions than attainable with proteins, the bis-anhydride of DTPA was reacted in anhydrous, hot DMSO with dextrans ranging in size from 17,000 molecular weight (MW) to 150,000 MW in various ratios of DTPA to glucose units from 1:1 to 1:40. Up to several hundred DTPA units per saccharide complex could be attached with this technique. Depending on the initial polysaccharide length and ratio of DTPA to glucose units, various degrees of cross-linking occur. Average MW of the polymers ranging from 17,000 to particles several million MW could be synthesized. The ester bond thus formed is stable for prolonged periods in solution. Depending on the polymer size, soluble material, gels, or particles are formed. Relaxation rates of the soluble material are similar or better than Gd-DTPA on a molar basis of Gd3+. The particulate material demonstrates T2 shortening out of proportion to T1, as expected for solid material, from increased susceptibility effects.

Biodistribution and magnetic resonance imaging of cross-linked DTPA polysaccharides.

Large polysaccharide complexes, cross-linked with DTPA and chelated with gadolinium have been tested for various potential uses for magnetic resonance imaging (MRI) in rats. Biodistribution and pharmacokinetic data for several of the soluble polymers are presented and compared with Gd-DTPA and GdCl3. By varying the initial polysaccharide length and ratio of DTPA to glucose units, polymers of molecular weights (mol wt) from 17,000 to several million were formed, giving soluble material, gels, or particles. The larger polymers (mol wt greater than 100,000) demonstrate prolonged enhancement of the intravascular space, striking renal enhancement, and moderate hepatic uptake. Small particulate material (less than 10 microns) was also successfully used for intravascular enhancement. The material is metabolized and excreted in urine.

Improved pyeloureteral visualization using glucagon during experimental intravenous urography.

Intravenous urography is optimally performed using abdominal compression for distention of the pyelocalyceal systems. Because of real and potential difficulties with the application of compression, the authors have tested in dogs the alternative of administering glucagon as a means of improving pyelocalyceal distention and ureteral visualization. In six greyhound dogs, ureteral peristalsis transiently ceased following the intravenous injection of glucagon. Objective and coded subjective analyses showed statistically significant improvement in demonstration of collecting systems and ureters when urograms were performed with glucagon, as compared with those in which the drug was not administered. The success of glucagon in improving pyeloureteral visualization in dogs encourages its experimental use in human subjects as an alternative to abdominal compression.

Computer-simulated lung nodules in digital chest radiographs for detection studies.

Computer simulations of lung nodules overcome many shortcomings of creating radiographs using anthropomorphic nodule phantoms for lung nodule detection studies, but these algorithms can be cumbersome and involved. A simple, fast, and flexible computer program to simulate lung nodules in digital chest radiographs for detection studies is reported. To verify the realism of the simulated nodules, a psychophysical study and a statistical study were conducted. In the psychophysical study, six radiologists and four nonradiologists were asked to distinguish between 17 real lung nodules and 17 computer-simulated lung nodules shown in eight radiographs. The results show that the computer-simulated lung nodules are indistinguishable visually from real lung nodules. Using parameters from the Rose model of vision, results show that the simulated and real nodules are the same statistically. Thus, besides visual validity, statistical analysis in confirming the validity of the simulated lung nodules is included.

Computed radiographic evaluation of simulated pulmonary nodules. Preliminary results.

We evaluated the capabilities of a computed radiography system (CRS) and a standard radiography system (SRS) in the detection of simulated solitary pulmonary lung nodules of various sizes and contrast. A phantom simulated the pulmonary anatomy, and specially shaped plexiglass disks were externally mounted to simulate solitary pulmonary nodules of different diameters and thicknesses. ROC curves were generated based on the performance of each of the radiologists observing each film set. In this preliminary study, the overall performance for both the CRS and the SRS were comparable in detecting simulated pulmonary nodules.

Digital video subtraction angiography: screening technique for renovascular hypertension.

Significant deterrents to the detection of renovascular hypertension are the unreliability of current screening methods and the widespread belief that the incidence of renal artery stenosis is too low to justify the expense and morbidity of routine angiography. We have developed a new imaging method, digital video subtraction angiography, suitable for screening outpatients for renal artery lesions. It involves injecting a 45 cc bolus of contrast medium through a venous catheter. Instead of exposing x-ray film, images are recorded directly on an image intensifier, digitized, and stored in a computer that electronically subtracts, reconstructs, enhances, and magnifies the images on a video screen. Renal parenchymal vessels less than 1 mm in diameter can be seen. So far, 45 studies have been performed in 39 hypertensive patients. Images of diagnostic quality were obtained in all except one. Renal artery stenosis was revealed in 15 patients, renal artery occlusion in two, diffuse intrarenal arterial narrowing in two, atrophic kidney with small renal arteries in two, and normal renal vessels in 23. Digital video subtraction angiography is an inexpensive, cost-effective, safe, and accurate method for renovascular hypertension screening and for evaluating patients after surgical correction of renal artery stenosis.

Ischemic therapy in thrombocytopenia from hypersplenism.

Percutaneous transfemoral arterial balloon occlusion or gelatin sponge embolization of the splenic artery or both were carried out in three high-risk patients with hepatic cirrhosis to reduce splenic hyperfunction and improve severe thrombocytopenia. Although this maneuver raised peripheral platelet counts in each patient, in one patient left upper quadrant pain with splinting of the lower chest cage led to hypostatic lower lobe pneumonia, while in another septic splentitis with gas-forming organisms necessitated splecectomy. Transfemoral occlusion of the splenic artery, although an effective, noninvasive approach to control splenic hyperfunction, has at the same time potential dangers that should be viewed with extreme caution in therapeutic application.

Evaluation of cerebral hemispheric contrast transit with intravenous digital subtraction angiography.

Thirty-six patients with varying degrees of stenosis of one internal carotid artery were studied using intravenous digital subtraction angiography, assessing relative hemispheric washin and washout of contrast medium. Ipsilateral delayed contrast transit was seen in 16 of 18 patients with a 70% or greater carotid artery stenosis. Decreased hemispheric peak contrast density was also seen in most of these patients. With further improvements in the computer program and faster imaging rates, intravenous digital subtraction angiography has the capability of providing valuable physiologic data along with anatomic information in patients with suspected cerebral ischemia.

Digital subtraction angiography: technology, equipment, and techniques.

The equipment used in digital subtraction angiography is a combination of x-ray equipment and high-speed image-processing equipment. In this article, the components of a DSA system are described, including the x-ray generator, x-ray tube, image intensifier, television system, analog-to-digital (A-D) convertor, image processor, and image acquisition console, as well as available commercial equipment. Techniques for DSA examination are also discussed.

Digital cardiac radiology.

The purpose of this article is to provide the general diagnostic radiologist with an overview of digital radiographic techniques. The development of digital cardiac radiology is discussed first, followed by discussions of intravenous and intra-arterial digital left ventriculography. There is a discussion of the use of digital techniques in the diagnosis of congenital heart disease, and some comments on the use of digital techniques to study myocardial perfusion.

The digital radiology department of the future.

The boom in microelectronics, including cost-effectiveness, has now allowed us to consider the use of these objects to store digital images. There remains much research, development, and clinical evaluation to be done in receptor technology. Further improvements in image processing, optical laser disk storage, and optical transmission and further commercial development of display technology must take place. All of these developments are occurring simultaneously. Within 5 to 10 years, radiology departments will most likely be totally electronic, probably cost-effective, and, it is hoped, more diagnostically accurate.

Digital video subtraction angiography of the cervical and cerebral vasculature.

A digital video subtraction angiography unit developed at the University of Arizona is described. The system allows the angiographic evaluation of the cervical and cerebral vasculature by means of intravenous injection of contrast material. The procedure is performed on outpatients and is reliable, safe, and economical. The authors have evaluated suspected arterial and venous occlusive disease, certain aneurysms and tumors, and postoperative results of vascular bypass procedures and aneurysm clipping. The clinical application of the technique is shown with appropriate case presentations.

Design and testing of artifact-suppressed adaptive histogram equalization: a contrast-enhancement technique for display of digital chest radiographs.

One of the goals of our research in the field of digital radiography has been to develop contrast-enhancement algorithms for eventual use in the display of chest images on video devices with the aim of preserving the diagnostic information presently available with film, some of which would normally be lost because of the smaller dynamic range of video monitors. The ASAHE algorithm discussed in this article has been tested by investigating observer performance in a difficult detection task involving phantoms and simulated lung nodules, using film as the output medium. The results of the experiment showed that the algorithm is successful in providing contrast-enhanced, natural-looking chest images while maintaining diagnostic information. The algorithm did not effect an increase in nodule detectability, but this was not unexpected because film is a medium capable of displaying a wide range of gray levels. It is sufficient at this stage to show that there is no degradation in observer performance. Future tests will evaluate the performance of the ASAHE algorithm in preparing chest images for video display.

Ideal configuration for intravenous digital subtraction angiography machine.

An assessment of the current state of development of digital imaging systems is provided as well as recommendations for future areas of investigation, including the incorporation of large-field image intensifiers, higher raster rate TV systems, and high speed digital disks into digital subtraction angiography (DSA) machines. Recent advances in hardware and software developments are discussed as they pertain to the X-ray generator and tube, X-ray image sensors (image intensifiers and TV cameras), and the image processor of the DSA system.

Comparison of conventional pulmonary angiography with intravenous digital subtraction angiography for pulmonary embolic disease.

Intravenous digital subtraction pulmonary angiography was performed in 33 patients with suspected pulmonary embolism. It was performed as the initial examination, followed immediately by conventional film-screen pulmonary angiography performed with selective right or left main pulmonary injections. Intravenous studies of diagnostic quality were obtained in 31 of 33 patients (93.9%). Of the satisfactory intravenous studies, pulmonary embolism was correctly diagnosed in 12 cases and excluded in 18 cases. Emboli were detected in major and second-order branches, and occasionally in third-order branches as well. There was one false-positive intravenous pulmonary study, but the overall accuracy was 90.9% considering all studies and 96.8% excluding the two inadequate intravenous examinations. It is concluded that intravenous pulmonary angiography is an acceptable substitute for routine pulmonary angiography in most patients with suspected major pulmonary embolism. The technique is less expensive, and is safer, faster, and easier to perform than conventional pulmonary angiography.