Charito Love MD, Presenter: Nothing to Disclose

Gene Tronco MD, Abstract Co-Author: Nothing to Disclose

Scott E. Marwin MD, Abstract Co-Author: Nothing to Disclose

Christopher J. Palestro MD, Abstract Co-Author: Speakers Bureau, Tyco Healthcare (Mallinckrodt Inc) Research Consultant, Palatin Technologies, Inc Research grants, DRAXIS Health Inc Research grants, General Electric Company

Lymph node uptake of labeled leukocytes produces spatially incongruent 111labeled leukocyte and 99mTc-sulfur colloid images, causing false positive results. The objectives of this study were to determine the frequency and appearance of nodal activity on labeled leukocyte images of failed prosthetic hips, in order to reduce the likelihood of study misinterpretation.

Combined 111In-labeled leukocyte and 99mTc-sulfur colloid marrow studies of 88 failed hip prostheses were included in this retrospective investigation. One experienced nuclear physician without knowledge of other test results or final diagnoses reviewed and classified images as spatially congruent or spatially incongruent according to standard criteria (Reading 1). Images were reviewed again and studies in which the spatially incongruent distribution of activity was due only to multiple, discrete foci on labeled leukocyte images, corresponding to the usual distribution of inguinal lymph nodes were classified as negative for infection (Reading 2). Final diagnoses were surgically confirmed in all cases.

Thirty-three (38%)prostheses were infected and 55 (62%) were aseptically loosened. The nodal activity pattern was present on 26/88 (34%) studies, including 8/33 (24%) infected and 18/55 (33%) uninfected prostheses. For Reading 1, sensitivity and specificity of the test were 32/33 (97%)and 37/55 (67%), respectively. For Reading 2, sensitivity and specificity were 32/33 (97%) and 53/55 (96%), respectively.

Multiple, round, discrete foci of activity corresponding to the usual distribution of the inguinal lymph node chain are present in up to about one-third of labeled leukocyte studies of failed hip replacements and produce spatially incongruent leukocyte/marrow images even in the absence of infection. When the spatially incongruent area is due only to this nodal activity, the study should be interpreted as negative for prosthetic infection.

The recognition that spatially incongruent labeled leukocyte/marrow images of hip replacements due only to nodal activity are not indicative of infection reduces the number of false positive results.

Love, C, Tronco, G, Marwin, S, Palestro, C, Lymph Node Activity on Combined Indium-111-Labeled Leukocyte and Technetium-99m-Sulfur Colloid Marrow Imaging of Failed Hip Prostheses: A Potential Pitfall in Image Interpretation.  Radiological Society of North America 2006 Scientific Assembly and Annual Meeting, November 26 - December 1, 2006 ,Chicago IL. http://archive.rsna.org/2006/4434151.html