Comparative Study between Magnetic Resonance Imaging and Technetium-99m-MDP Bone SPECT in The Evaluation of The Hydroxyapatite Orbital Implant: Report of Two Cases

ABSTRACT

Because of the excellent cosmetic and functional reconstruction compared with other integrated implant, hydroxyaptite is commonly used in recently. This excellent cosmetic effect is acquired by successful integration between hydroxyapatite and normal orbital tissue by fibrovascular tissue. We performed simultanously magnetic resonance imaging and bone scan to two patients undergoing hydroxyapatite orbital implantation after evisceration and evaluating fibrovascular ingrowth into the implant between MRI and bone scan and observed ingrowing pattern of fibrovascular tissue into the hydroxyapatite after evisceration especially. MRI studies are somewhat more valuable imaging than bone scan. Vascularization into the implant were started from inserted portion of extraocular muscle and posterior aspect of implant and slowly progressed to the center of hydroxyapatite sphere. There was no relation between inserted duration and fibrovascular ingrowth due to individual variation. And constrast enhanced MRI appears to be the best imaging method for evaluating the hydroxyapatite orbital implant and its fibrovascular ingrowth. In spite of low specificity compared with MRI, bone scan is also valuable method for the evaluating vascularization of the hydroxyapatite because of low cost and easy follow-up.