Comparison of Quantification Methods of¹¹¹In-Labelled Platelet Deposition in Peripheral Bypass Grafts

The action of antithrombotic drugs can be evaluated by measuring the deposition of¹¹¹In-labelled platelets on peripheral bypass grafts several days after injection. This evaluation can be performed qualitatively (visual interpretation on the daily images) or quantitatively. Four different methods which calculate the ratio of platelet uptake with a reference region are compared: two methods use a gamma camera and two a detector. A blood sample or the region under the sternal angle are used as reference. The daily ratio of the counts, recorded by a gamma camera in a region of interest covering the graft, and the blood radioactivity interpolated from a platelet survival curve appears to be the most reliable method. The information of all the ratios can be combined in a single thrombogenicity index which reflects the daily rise of a linear or exponential regression versus time.

Zusammenfassung

Die Wirkung von Antithrombose-Medikamenten kann durch eine Messung der Ablagerung von mit ¹¹¹In-markierten Blutplättchen auf periphere Bypassgrafts mehrere Tage nach der Injektion bewertet werden. Vier verschiedene Methoden zur Berechnung der relativen Ablagerung der Blutplättchen wurden verglichen: zwei Methoden benutzen eine Gammakamera, zwei einen Detektor. Die tägliche Speicherung, bestimmt aus einem Bereich um den Graft und der Blutradioaktivität, interpoliert mit einer Blutplättchen-Überlebenskurve, scheint die zuverlässigste Methode zu sein. Diese Relationen können in einem Thrombogenitätsindex zusammengefaßt werden, der den täglichen Zuwachs nach einer linearen oder exponentiellen Regression wiedergibt.

• REFERENCES

• 1 Heyns A, Du P. et al. The kinetics and sites of sequestration of platelets in arterial disease. Abstract of the Conference on Radionuclide Labelled Cellular Blood Elements. 14 Bloemfontein RSA; February 1986
• 2 Erekowitz M. D. et al. Imaging platelet deposition. Abstract of the Conference on Radionuclide Labelled Cellular Blood Elements. 26 Bloemfontein RSA. February 1986
• 3 Goldman M, Norcott H. C, Hawker R. J. et al. Femoropopliteal bypass grafts. An isotope technique allowing in vivo comparison of thrombogenicity. Brit. J. Surg 1982; 69: 380-2.
• 4 Goldman M, Norcott H. C, Hawker R. J. et al. Platelet accumulation on mature dacron grafts. Brit. J. Surg 1982; Suppl. 69: 38-40.
• 5 Goldman M, Hall C, Rykes J. et al. Does ¹¹¹Indium-platelet deposition predict potency in prosthetic arterial grafts?. Brit. J. Surg 1983; 70: 653-8.
• 6 Hardemans M. R. et al. Blood Cells in Nuclear Medicine, Part I. 17-28 Mar-tinus Nijhoff, Dordrecht 1984;
• 7 Harker L. A, Slichter S. J. Studies of platelet and fibrinogen kinetics in patients with prosthetic heart values. New Engl. J. Med 1970; 283: 1302.
• 8 Lewis S. M. and the Panel on Diagnostic Applications in Hematology (ICSH):. Recommended methods for radioisotope platelet survival studies. Blood 1977; 50: 1137-44.
• 9 Mortelmans L, Verbruggen A, de Roo M, Vermylen J. Evaluation of three methods of platelet labelling. Nucl. Med. Comm 1986; 07: 519-29.
• 10 Peeters A. M. et al. Platelet kinetics. Abstract of the Conference on Radionuclide Labelled Cellular Blood Elements. 20 Bloemfontein, RSA: February 1986
• 11 Pope C. F, Ezekowitz M. P, Smithe E. O. et al. Detection of platelet deposition at the site of peripheral balloon angioplasty using ^mIndiurn platelet scintigraphy. Amer. J. Cardiol 1985; 55: 495-7.
• 12 Powers W. J, Hopkins K. T, Welch M. J. Validation of the dual radiotracer method for quantitative ¹¹¹In platelet scintigraphy. Thromb. Res 1984; 34: 135-45.
• 13 Pumphrey C. W, Dewanjee M. K, Chereho J. H. et al. A new method for quantifying human platelet-vascular graft interaction and the effect of platelet-inhibitor therapy. Proc. Third World Congr. Nucl. Med. Biol. Part I. 895-7 Pergamon Press; Paris: 1982
• 14 Pumphrey C. W. In vivo quantitation of platelet deposition on human peripheral arterial bypass grafts using ¹¹¹indium-labelled platelets. Amer. J. Cardiol 1983; 51: 796-801.
• 15 Sinzinger H. et al. Imaging and monitoring of human atherosclerotic lesions with radiolabelled platelets. Abstract of the Conference on Radionuclide Labelled Cellular Blood Elements. 20 Bloemfontein, RSA: February 1986
• 16 Stratton J. R, Thiele B. L, Ritchie J. L. Platelet deposition on dacron bifurcation grafts in man: Quantitation with ¹¹¹Indium platelet imaging. Circulation 1982; 66: 1287-93.
• 17 Stratton J. R, Thiele B. L, Ritchie J. L. Natural history of platelet deposition on dacron aortic bifurcation grafts in the first year after implantation. Amer. J. Cardiol 1983; 52: 371-4.
• 18 Stratton J. R, Ritchie J. L. Failure of tichlopidine to inhibit deposition of ¹¹¹Indium-labelled platelets on dacron prosthetic surfaces in humans. Circulation 1984; 69: 677-83.