The use of 99mTc-HMPAO or 111In-oxine labelled white blood cells (WBC) is still considered the gold standard nuclear imaging technique to diagnose infections in the bone and soft tissue, except for spondylodiscitis. For prosthetic joint infections, there are some discrepancies in the reported diagnostic accuracy that may be related to different image acquisition protocols and different interpretation criteria of scans in absence of precise quantitation method. The recent published guidelines by the Infection Committee of the European Association of Nuclear Medicine (EANM) provide indications, practical aspects, quality controls and safety procedures of this technique. The approach described in the guidelines allows to discriminate sterile inflammation (loosening) from septic inflammation (infection), but also to discriminate between infection and bone-marrow expansion and, in some cases, to differentiate between osteomyelitis and soft tissue infection.
Recently, with the availability of hybrid SPECT/CT cameras, it is now possible to determine the exact localization of the infection can be achieved by analysing fusion SPECT and CT images. In addition, a dedicated software is able to calculate the SUV allowing to quantify the uptake in infected sites.The aim of our study is to analyse retrospectively the SPECT/CT scans, with SUV calculation, of 15 patients with suspected prosthetic infection of the hip and knee, that performed WBC scintigraphy, to evaluate the accuracy of this method in identifying infected and non-infected patients.
In addition, we will prospectively study 15 to 35 consecutive new cases, in 12 months, that will perform 99mTc-HMPAO-WBC scintigraphy for suspected prosthetic infection of the hip and knee, by planar and SPECT/CT imaging.
The results of this study will be published in a peer reviewed journal and will have both high scientific and clinical impact.
From the scientific point of view, we will compare for the first time in patients with suspected joint prosthetic infection, four different methods for image interpretation to evaluate the most accurate one that could be applied all users that have a SPECT gamma camera.
From the clinical point of view, results of this study will hopefully improve the diagnostic accuracy of WBC scan, with benefit for patient¿s care, and will represent a valuable information to be distributed amongst the nuclear medicine community.