PET-CT Animal Model for Surveillance of Embedded Metal Fragments

Abstract : Purpose: The purpose of this pilot study was to determine the sensitivity and specificity of small animal Positron Emission Tomography-Computed Tomography (PET-CT) in identifying metabolic changes in muscle tissue surrounding simulated shrapnel injuries and compare this imaging to traditional x-ray images. Design: Experimental design with repeated measures Methods: Fischer 344 male rats randomly assigned to three groups, were implanted with weapons grade heavy metal tungsten alloy (HMTA) pellets, tantalum (Ta) pellets as the control metal or Sham control without pellet implantation. Rats from each metal category received a series of x-rays and 18F fluoro-2-deoxy-D-glucose (FDG) PET-CT scans over 16 weeks. Sacrificed animals at each of five time points over a 16 week period had tissue excised for histopathological examination. Sample: 32 Fischer 344 male rats (2 Sham , 15 Ta, 15 HMTA) Analysis: .Standardized uptake value (SUV) tracer uptake was quantified using the. Image data comparisons were accomplished using Kolmogorov-Smirnov Z, Friedman s ANOVA and Wilcoxon signed-rank tests. Sensitivity and specificity were determined. Receiver Operating Characteristic (ROC) curve and the area under the curve (AUC) were calculated. Significance level was set at p .05. Histopathology was assessed by a pathologist, blinded to treatment groups. Findings: Increased FDG uptake was associated with an aggressive malignancy in the HMTA implanted rats. There was a significant difference in tracer uptake between the Ta and HMTA animals and also in tracer uptake over the sixteen weeks for the HMTA animals. PET-CT imaging had a sensitivity of 86%, specificity of 100% and AUC .938. Implications for Military Nursing: Military nurses have a unique opportunity to educate patients and providers about the possibility of early tissue changes around embedded fragments and the use of PET-CT imaging as a possible surveillance tool. When retained shrapnel is located, monitor patients for fragment