Biomedical subjects
Publications and source records attributed to J Gardener.
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Knowledge of the segmental anatomy and intersegmental biliary connections is an essential prerequisite to the effective management of patients with complex biliary strictures. Three dimensional (3D) imaging has the ability to demonstrate complex anatomical relationships that are difficult to appreciate on simple non-invasive two dimensional (2D) imaging. Our aim was to develop a technique for accurate, non-invasive 3D computed tomography (CT) cholangiography. Contiguous 4 mm CT sections were obtained through the liver during a dynamic bolus of 200 ml IV contrast. 3D surface reconstructions were then performed, the biliary system was isolated from surrounding hepatic parenchyma using segmentation and contrast threshold algorithms. 14 patients (six females, eight males, median age 68 years (range 48-82)) were studied. 13/14 had malignant biliary obstruction and one had obstruction secondary to a pancreatic pseudocyst. Obstruction was at the liver hilum in eight, the common bile duct in five and the common hepatic duct in one. Four patients had biliary endoprostheses but were symptomatic from inadequate drainage. There was good demonstration of the biliary anatomy, obstructed segments and intersegmental biliary connections in 13/14; irregular biliary dilatation secondary to primary sclerosing cholangitis rendered interpretation difficult in one. 3D cholangiography provided a useful adjunct to other imaging techniques. In particular, in patients with complex hilar strictures it aided implementation of appropriate interventional drainage procedures.
The ultrasonic appearance of in vitro normal and atherosclerotic arterial wall was investigated with an intravascular ultrasound (IVUS) probe. Fresh cadaver specimens were used: two carotid, two aorta, four iliac and eight superficial femoral arteries. The wall of muscular arteries has a three-layered sonographic appearance. The central hypoechoic layer corresponds to the media, which is primarily composed of smooth muscle. Elastic arteries whose media have a high elastin content appear uniformly echogenic. Calcified plaque is strongly echogenic with acoustic shadowing, fibrous plaque is moderately echogenic, and where there is no cellular matrix the plaque is poorly echogenic. IVUS can provide information about internal plaque architecture. Three-dimensional reconstructions can be generated using a transputer-based workstation coupled to the transducer, providing detailed views of surface contour.
A system is described which produces displays of anatomical surfaces from sets of X-ray computed tomography (CT), magnetic resonance imaging (MRI) and ultrasonographic scans (US). The displays are created to show the three-dimensional character of the internal and external anatomy. The images may be manipulated on the screen to simulate dissection of the three-dimensional object they represent. Thus it is possible to increase the diagnostic value of the original data and to plan surgery by simulation. To allow long-term studies on the human face for surgical planning and assessment a non-hazardous optical scanning system has been devised. The display system also produces data to drive a numerically controlled milling machine for the production of models, prostheses and implants.
Phase and amplitude analysis was applied to intravenous digital left ventriculograms to avoid the artefacts associated with image subtraction. Eight controls and 40 patients with known coronary artery disease underwent digital left ventriculography before and after a symptom limited supine bicycle exercise test. The resultant images were subjected to phase and amplitude analyses. In the control group there was no deterioration in left ventricular wall motion after exercise. In 30 of the 40 patients there was a deterioration in wall motion on exercise. This group contained all eight patients with three vessel disease and 12 of the 17 patients with two vessel disease. Ten patients showed no change in wall motion--five with one vessel disease and five with two vessel disease. Phase and amplitude analysis of digital left ventriculograms is a method of detecting exercise induced myocardial ischaemia that may help in the assessment of patients with coronary artery disease.
Arrival-time analysis was applied to intravenous digital aortograms. A single static image was produced by representing the time to 90% maximum density for each image pixel on a grey scale. Arrival-time analysis confirmed the diagnosis in four of six patients with aortic dissection that had been shown by image subtraction. In a further three patients with no dissection the arrival-time images were normal. In two patients with surgical repair of the ascending aorta, residual false lumens were shown by both subtraction and arrival-time analysis. In one of these cases arrival-time analysis prompted reanalysis of the subtraction image that had previously been interpreted as showing a normal aorta. Arrival-time analysis provides a static image of aortic dissection, which helps to overcome subtraction artefact.
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