Radiolabelled white blood cells or FDG for imaging of inflammation and infection? A. SIGNORE 1, 2 , V. E. SOROA 3 , E. F. J. DE VRIES 1 N uclear medicine plays an important role in the management of patients with inflammatory and infectious diseases, especially when anatomical changes in inflammatory foci are absent or obscured. Several radiopharmaceuticals methods have been used for scintigraphic imaging of infectious and ster- ile inflammatory foci, including 67 Ga-citrate, labelled white blood cells, antibodies, human immunoglob- ulin and antibiotics. Since the 1970s, scintigraphic imaging with labelled white blood cells has been the most frequently used nuclear imaging method for clinical diagnosis of infection and inflammation worldwide. The success of white blood cell scintig- raphy is primarily due to its superb diagnostic accu- racy. White blood cell scintigraphy comprises the isolation of autologous leukocytes, the ex vivo labelling of these cells with either 99m Tc-HPMAO or 111 In-oxine and reinjection of the labelled cells into the patient. The preparation of the radiopharma- ceutical is the Achilles’s heel of white blood cell imaging, because it requires a trained technician and special facilities. The procedure is laborious and time-consuming and requires the handling of the patient’s blood, which could potentially be contam- inated with pathogens. During the preparation of the radiopharmaceutical care should be taken that the leukocytes are not damaged, as this would result in leakage of the radioactivity from the cells, sticking of the labelled leukocytes to the vascular endothelium (especially in the microvasculature of the lungs) and 1 Department of Nuclear Medicine and Molecular Imaging University Medical Center Groningen University of Groningen, Groningen, the Netherlands 2 Department of Nuclear Medicine, "La Sapienza"University, S. Andrea Hospital, Rome, Italy 2 Center of Nuclear Medicine National Commission of Argentine Atomic Energy Buenos Aires, Argentina loss of motility. Even when the leucocytes are han- dled correctly during labelling, release of 99m Tc- HPMAO from the labelled white blood cells after re- injection into the patient is still observed. The free 99m Tc-HPMAO is excreted via the hepatobiliary sys- tem and the kidneys, which may hamper image inter- pretation. This phenomenon is not observed with 111 In-oxine labelled leukocytes. Still, 99m Tc-HPMAO labelled white blood cells are usually preferred for scintigraphy, because the radiation characteristics of 99m Tc are superior for gamma camera imaging. Despite the aforementioned drawbacks, white blood cell scintigraphy is still considered the method of choice for many applications. Especially when the correct imaging protocol is used ( i.e. early and delayed white blood cell imaging in combination with colloid imaging), the specificity of this method is very high. Further improvement of the diagnostic accuracy of white blood cell imaging can be achieved using hybrid single photon emission computed tomography (SPECT)-CT systems. By combining the anatomical information from the CT with the func- Vol. 53 - No. THE QUARTERLY JOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING 1 Corresponding author: Prof. A. Signore, MD, PhD, Nuclear Medicine, "La Sapienza" University, S. Andrea Hospital, Via di Grottarossa 1035, 00189, Roma, Italy. E-mail: alberto.signore@uniroma1.it 2127 JNU/Original articles Q J NUCL MED MOL IMAGING 2009;53:000-000