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Objective: Both state and federal regulations require weekly monitoring of the resolution and linearity of the scintillation camera. Several phantoms are available to perform this quality control function. These include the quadrant bar. Bureau of Radiological Health (BRH), and orthogonal-hole (OH) phantoms. Each of these phantoms has either functional or temporal limitations on its use. The orthogonal tri-hole phantom (OTHP) was designed to overcome these limitations., Methods: The OTHP consists of a precision-drilled lead plate sandwiched between two plastic plates. The OTHP has an active area of 15 in. x 20 in. which contains an orthogonal array of three-hole (2.5-mm, 3.0-mm, and 4.0-mm) clusters. Intrinsic and extrinsic images were acquired for the OTHP, OH phantom, BRH phantom and quadrant bar phantom., Results: The OTHP test pattern allows resolution, linearity, object shape, and contrast to be evaluated simultaneously, either intrinsically or extrinsically, in a single image over the entire useful field-of-view., Conclusion: The OTHP provides a more quantitative evaluation of the quality control parameters than any other phantom currently available. The use of the OTHP results in cost savings since both camera and technologist time are reduced because only one image is required instead of the two or four needed for other phantoms.

We have developed a simple in vivo scintigraphic technique that permits accurate quantitative comparison of intravascular platelet deposition in blood vessels of similar size. Regional count information from scintigraphic images of In-111 platelets and Tc-99m red blood cells is used to determine the ratio of radioactivity in the thrombus relative to that in the blood. Multiplication of this ratio by the percent injected dose (%ID) of In-111 per ml of blood yields a quantity (%ID index) that is directly proportional to the %ID of In-111 platelets in the thrombus as measured in vitro (r = .879, p less than 0.005). This technique is well suited for quantitative studies of scintigraphically detectable platelet deposition in both animals and in man.

Serial platelet deposition, surface topography, and patency were evaluated in control (N = 28) and endothelial cell-seeded (N = 28) small-diameter (4 mm inner diameter) USCI Dacron grafts implanted in the carotid and femoral arteries of dogs. All dogs received aspirin (325 mg) daily for 2 weeks starting 24 hours prior to graft implantation. Endothelial cell seeding was performed by mixing suspensions of autologous endothelial cells that had been enzymatically harvested from segments of external jugular vein with blood that was used to preclot the prostheses. The platelet deposition on each graft was quantitated by means of indium 111-labeled platelets and technetium 99m-labeled red cells in a dual-isotope platelet-imaging technique. Platelet deposition on seeded grafts 24 hours after implantation was significantly higher than on the controls (p less than 0.05). Two weeks after implantation platelet deposition on seeded prostheses had decreased to a level significantly lower than that on the controls and continued to decline on serial studies up to 7 months. In contrast to seeded grafts, platelet accumulation on control grafts dramatically increased after the withdrawal of aspirin therapy and was associated with a sharp rise in control graft thromboses. Gross and scanning electron microscopic evaluation of endothelial cell-seeded grafts after 1 month indicated complete neointimal coverage, whereas none of the control grafts explanted at 1 month or later exhibited a continuous neointimal lining. Cumulative 7-month patency for seeded prostheses was significantly higher than for the controls (96% and 29%, respectively; p less than 0.001). We conclude that endothelial cell seeding in combination with short-term aspirin therapy is a simple, reliable diameter Dacron prostheses. Abrupt withdrawal of aspirin therapy may be contraindicated in nonseeded control grafts because it results in increased platelet deposition and thrombosis.