The impact of PACS on the information flow.

It is likely that changes in hospital operational practices made possible by the introduction of a whole hospital PACS will require the present information and data patterns to be changed significantly. Some of the factors which will affect the flow of data and information are considered, and the implications of comparing the costs of installing 'whole hospital' PACS systems in different institutions are discussed.

Clinical diagnosis from digital displays: preliminary findings of the St Mary's Evaluation Project.

Image quality is a fundamental issue in the introduction of picture archiving and communications systems (PACS), and one that has hitherto been eclipsed by other aspects of the considerable technological challenge facing scientists and manufacturers involved in its development. We conducted a formal evaluation of clinical radiological diagnosis from a commercially available PACS viewing station, using subperiosteal resorbtion in renal osteodystrophy as the test pathological diagnosis, with receiver operating characteristic (ROC) analysis of the results. We conclude that the displayed, digitised images were inferior to film using the apparatus tested and believe that careful, objective clinical evaluation of such systems is of paramount important.

Quantitative studies of splenic erythropoiesis in polycythaemia vera and myelofibrosis.

A quantitative scanning method employing cyclotron-produced 52Fe has been developed to assess splenic erythropoiesis in patients with myeloproliferative disorders. In 12 patients with myelofibrosis splenic uptake of 52Fe was from 5.0% to 48% of the injected dose. Although a single patient with classical polycythaemia vera had a minor uptake of 2.8% of six other patients with this diagnosis showed no concentration of isotope in the splenic area. The fraction of 52Fe in the spleen of four patients with 'transitional' myeloproliferative disorders characterized by a high red cell mass, hypercellular bone marrow and a leucoerythroblastic blood film varied from 5% to 41%. No clear relationship was noted between the degree of splenic erythropoiesis as defined by this technique and the level of haemoglobin, the degree of splenomegaly, the effectiveness of erythropoiesis of traditional 59Fe surface counting. If splenectomy is considered in patients with myelofibrosis splenic 52Fe quantitation will provide more precise data on the contribution of splenic erythropoiesis than 59Fe surface counting alone.

Rate of clearance by the spleen of heat-damaged erythrocytes.

The rate of uptake in the spleen of heat-damaged red blood cells labelled with 99mTc has been measured by radioisotope scanning in 38 patients. The values obtained for the half-clearance time into the spleen using this method have been compared with the values obtained simultaneously by blood sampling for the rate of loss of radioactivity from the circulation. It was found that the uptake into the spleen was approximately three times faster than the measured rate of loss of radioactivity from the blood. The reasons for this are discussed and it is suggested that the scanning technique is more reliable as a measure of this aspect of splenic function.

A comparison of clinical results in brain scanning using germanium semiconductor detectors and sodium iodide detectors.

A comparison is presented of the image quality obtained with a 70 mm Ge(Li) detector scanner and with routine techniques based on NaI (Tl) detectors. One hundred and sixty-five pairs of brain scans have been examined for which the patients have been scanned with both Ge(Li) and NaI (Tl) detectors. It is concluded that no major difficulties exist in introducing Ge(Li) scanners and that while a comparison of scans from different instruments is difficult there is evidence that improved diagnostic information may be obtained from scanners with Ge(Li) detectors.

The assay of iodine-123.

Compounds labeled with 123I are becoming more common in scintillation imaging due to the convenient combination of the 13.3-hr half-life and the 159-keV gamma radiation. Here attention is drawn to the particularly large summing effects observed when 123I is counted in a well counter. These could lead to errors in the assay of doses if the analyzer windows used are too narrow.

Quantitative measurement of splenic and hepatic red-cell destruction.

A method has been developed by means of which independent measurement can be made of the amount of red-cell destruction occurring in the spleen and the liver. The technique involves a standard red-cell survival study and surface-counting measurements together with quantitative scanning of the spleen and liver with 113mIn colloid in order to calibrate the surface counter. The rate of destruction in each organ is obtained by fitting the measured uptake curve for the organ to a theoretical uptake curve by computer. In addition, if whole body counting is also performed, the amount of red-cell destruction occurring in the rest of the reticuloendothelial system may be deduced. Results are given for measurements on a series of 11 patients.

The effect of the size of the gastric outlet on gastric emptying after vagotomy for duodenal ulcer.

Gastric emptying of isotopically labelled solid meals was studied in normal human subjects and in 30 patients who had had an operation for chronic duodenal ulcer. Each patient had a vagotomy of the whole stomach combined with either a Finney pyloroplasty to produce a large gastric outlet or a Heineke-Mikulicz pyloroplasty to produce a relatively small outlet. At 10-22 days after operation gastric emptying was equally and significantly slowed in both groups when compared with the normal controls. This delay occurred regardless of whether the vagotomy was complete or incomplete. At 4-6 months after operation emptying had returned to normal in the patients who had had a Finney pyloroplasty but remained significantly slowed after Heineke-Mikulicz pyloroplasty. Mild symptoms of gastric stasis frequently occurred in both groups in the early postoperative period, but were rare 4-6 months after operation. There was no correlation between the incidence of these early symptoms of stasis and the size of the gastric outlet constructed.

Gastric emptying following vagotomy and antrectomy and proximal gastric vagotomy.

Gastric emptying of solid meals labelled with 129Cs was studied in patients for up to one year after vagotomy and antrectomy or after proximal gastric vagotomy. Significant delay was found one month after vagotomy and antrectomy but this had returned to normal by six months. No delay was found after proximal gastric vagotomy. The effect of posture on gastric emptying was also studied in the same subjects. No significant differences were found between gastric emptying in the supine or sitting positions after solid meals.

Collimation and surface counting in haematology.

The effect on the results obtained in surface counting investigations of using a dual detector counting system and multihole collimators has been investigated. The use of the additional detector results in smoother curves for the uptake of the radionuclide and the use of multihole collimators increases the discrimination of the counting system against the effects of radioactivity outside the region of interest. In a clinical trial to compare multihole collimation with conventional single hole collimation it was found that increased excess counts were obtained over the spleen with the multihole collimators in eight of ten cases.