The paper describes an approach to solving the problem of providing a large-capacity image archive for diagnostic imaging departments at reasonable cost. Optical disk stores, when fitted retrospectively to scanners, are very expensive and may not be compatible with existing computer hardware. We describe the use of an industry standard personal computer (PC) linked to a standard 5 1/4-in. optical disk drive as a 'stand-alone' image store. Image data are transferred from the scanner using 8-in. floppy disks, and these are read into the PC using an attached 8-in. floppy disk drive and then transferred to the optical disk. The patient details (patient name, ID, date, etc.) are entered into a database program held on the PC and these are used to generate a reference pointer to the optical disk file through which the data can be retrieved. Data retrieval involves entering the patient details into the data base and inserting a blank 8-in. floppy disk into the drive attached to the PC. A sector copy is then made from the optical disk to the 8-in. floppy disk, which can then be used at the viewing station at the scanner. The system is flexible since it can accept data from a variety of sources in any format; it is also low cost and operates independently of the scanner. The hardware is industry standard, ensuring low maintenance costs.

Diagnostic Imaging↗

PubMedDate not supplied

Assessing clot lysis strategies using a simplified mathematical model.

This paper attempts to describe lysis of a clot by infusion of lytic agent using a simple geometrical approach, in which the rate of clot lysis is assumed proportional to the exposed surface of the clot and the concentration of lytic agent. Six simple realizations (a)-(f) of this basic model are developed which account for the dependence of clot lysis time on five different clot geometries. In all six cases the clot is initially described as a uniform cylinder which totally occludes a vessel. In model (a) lysis proceeds as an advancing front at the proximal face of the clot. In model (b) lysis proceeds radially outwards from the central axis of the vessel while in model (c) lysis occurs radially inwards from the surface adjacent the wall, of the cylinder. In models (d) and (e) it is assumed that the clot breaks into a uniform spherical and cylindrical fragments, respectively, while model (f) uses the spherical fragment model combined with a lytic agent concentration which decreases with time. The validity of the models was assessed using previously published data from 76 patients in whom lysis time and clot size were recorded. Least squares linear regression analysis based on the six model equations yielded highly significant correlation coefficients r2 of 0.457, 0.412, 0.412, 0.495, 0.469, 0.663 for models (a)-(f), respectively. The results suggest that when a constant lytic agent concentration is assumed, no single geometry accounts for significantly more variation than any other, but that a combination of varying lytic agent concentration and clot geometry significantly influences clot lysis time and accounts for much of the observed variation.

Humans↗

PubMedDate not supplied

Hepatic perfusion index (HPI) in mesenteric angina and following successful revascularization.

This is a case report of a 45 year old man who had previously undergone a small bowel resection for acute mesenteric ischaemia. He subsequently suffered from mesenteric angina due to stenosis of the origin of the superior mesenteric artery and intermittent claudication due to aorto-iliac atheroma. The patient underwent a successful aorto-bifemoral Y graft and small bowel revascularization with a saphenous vein graft between the Y graft and the accessible proximal portion of the superior mesenteric artery. Before vascular reconstruction, the hepatic perfusion indices (HPI) in both the fasted and fed states were elevated; after mesenteric revascularization the HPI values were substantially lowered. The hepatic perfusion index may, by demonstrating functional abnormality, be useful in the diagnosis of mesenteric ischaemia and also in the assessment of treatment. Further evaluation of HPI in patients with suspected mesenteric ischaemia is therefore required.

Aorta↗

PubMedDate not supplied

The application of a new method of limb blood flow measurement using a radioactive isotope and a gamma camera.

To evaluate a new method for limb blood flow measurement using a radioactive isotope and a gamma camera, blood flow measurements have ben made on 108 patients with peripheral vascular disease. Thirty-six patients had ischaemic rest pain, of whom two had previously undergone unilateral amputation. Five had bilateral symptoms, giving 29 asymptomatic limbs and 41 limbs with critical ischaemia. In 72 patients with intermittent claudication a series of exercise tests were attempted, in 33 these were unsatisfactory; 13 patients had a greater than 20% variability in the maximum walking distance between four tests and in 20 walking distance was limited by factors other than claudication. In these 33 patients the limb blood flow to the symptomatic leg was 3.95 (1.36-11.08) ml/100 ml of tissue/minute. This is not significantly different from the limb blood flow to the symptomatic leg of the 39 patients who satisfactorily completed four exercise tests, 3.75 (1.08-8.25) ml/100 ml of tissue/minute. In these 39 patients the mean pain-free walking distance was 40 metres and the mean maximum walking distance was 63 metres. The limb blood flow to the 41 symptomatic limbs of 36 patients with rest pain was 1.90 (0.90-4.49) ml/100 ml of tissue/minute, which is significantly less than that obtained in claudicants. There was a wide range of blood flow values found in the asymptomatic limbs of all the patients and in many cases the flow was markedly reduced from normal. This method of limb blood flow measurement is accurate and reproducible and may be recommended for assessment of peripheral vascular disease.

Adult↗