White blood cells (WBC) scintigraphy is widely used for the assessment of suspected bone infection (BI) and joint prosthesis infection (PJI) because of WBC accumulate in time in infection site. Early total-body images (30 min), acquired for the in vivo quality control, delay (3-4h p.i.) and late images (20-24h p.i.) are usually acquired to detect WBC pathological accumulation. In this study we evaluated whether a scintigraphic acquisition at 6h p.i. can substitute lated images acquired at 20-24h p.i.
We studied 50 patients (22 men and 28 women) with suspected bone and joint prosthetic infectious process. The mean age was 65.5 ± 13 years. 39 patients with suspected PJI, 11 with suspected BI. We collected clinical history and laboratory analysis (Erythrocyte Sedimentation Rate, Reactive C Protein, WBC values) of all patients. Final diagnosis was based on microbiological colture or follow-up for at least 12 months. All patients underwent 99mTc-HMPAO WBC scintigraphy. Total-body and planar images (anterior and posterior) of the region of interest were acquired 30 minutes p.i., planar images (anterior and posterior) of the region of interest were acquired 4h, 6h and 22h p.i. using a two-head gamma-camera equipped with an integrated CT scanner (Infinia GE Medical System, Milwaukee). The time of acquisition, corrected on the decay time of the 99mTc, were respectively 300 sec, 476 sec, 600 sec and 3808 sec at 30min, 4h, 6h and 22h p.i.
All images were double-blind evaluated by three nuclear medicine physicians comparing 4h to 22h images and 4h to 6h. Consensus was reached for discordant cases.
Considering all 3 readers, planar scintigraphic images, acquired 4h and 6h p.i. showed 12 TP, 0 FP, 34 TN and 4 FN and planar scintigraphic images, acquired 4h and 22h p.i. showed 11 TP, 0 FP, 34 TN and 5 FN.
Our results suggest that WBC scintigraphy for diagnosis of PJI and BI could be performed in single-day in all patients with positive findings at 6h. The acquisition at 6h p.i. could replace the acquisition at 22h p.i. with less discomfort for the patient. In doubtful and/or negative scintigraphic results after 6h p.i. late images (20-24h p.i.) acquisition remains suggested.