Hindawi Publishing Corporation BioMed Research International Volume 2013, Article ID 780458, 12 pages http://dx.doi.org/10.1155/2013/780458 Research Article A Partial Volume Effect Correction Tailored for 18 F-FDG-PET Oncological Studies F. Gallivanone, 1 C. Canevari, 2 L. Gianolli, 2 C. Salvatore, 3 P. A. Della Rosa, 1 M. C. Gilardi, 1 and I. Castiglioni 1 1 IBFM-CNR, Via F.lli Cervi 93, 20090 Segrate, Milan, Italy 2 H San Rafaele, Via Olgettina 62, 20090 Segrate, Milan, Italy 3 University of Milan-Bicocca, Milan, Italy Correspondence should be addressed to I. Castiglioni; castiglioni.isabella@hsr.it Received 30 April 2013; Revised 2 August 2013; Accepted 2 August 2013 Academic Editor: Noriyoshi Sawabata Copyright © 2013 F. Gallivanone et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. We have developed, optimized, and validated a method for partial volume efect (PVE) correction of oncological lesions in positron emission tomography (PET) clinical studies, based on recovery coeicients (RC) and on PET measurements of lesion-to- background ratio (/  ) and of lesion metabolic volume. An operator-independent technique, based on an optimised threshold of the maximum lesion uptake, allows to deine an isocontour around the lesion on PET images in order to measure both lesion radioactivity uptake and lesion metabolic volume. RC are experimentally derived from PET measurements of hot spheres in hot background, miming oncological lesions. RC were obtained as a function of PET measured sphere-to-background ratio and PET measured sphere metabolic volume, both resulting from the threshold-isocontour technique. PVE correction of lesions of a diameter ranging from 10 mm to 40 mm and for measured /  from 2 to 30 was performed using measured RC curves tailored at answering the need to quantify a large variety of real oncological lesions by means of PET. Validation of the PVE correction method resulted to be accurate (>89%) in clinical realistic conditions for lesion diameter > 1 cm, recovering >76% of radioactivity for lesion diameter < 1 cm. Results from patient studies showed that the proposed PVE correction method is suitable and feasible and has an impact on a clinical environment. 1. Introduction Molecular imaging by positron emission tomography (PET) and 18 F-luorodeoxyglucose ( 18 F-FDG) radiotracer is cur- rently the most commonly used method for the detection and metabolic characterisation of several oncological pathologies, given the possibility to detect foci with an increased 18 F- FDG metabolism as those characterising tumour cells (e.g., [1, 2]). In the PET clinical environment, diagnosis and tumor staging are commonly assessed by qualitative visual inspec- tion of 18 F-FDG PET images [3–5]. Nevertheless, a quan- titative analysis of 18 F-FDG uptake in oncological lesions has been proven to be useful to diferentiate benign and malignant tissues (e.g., [6]), to assess response to therapy [7– 9], and to predict tumour aggressiveness [10–13]. Despite these beneits, a quantitative approach for the evaluation of PET oncological studies is not a common practice in clinical routine due to the presence of partial volume efect (PVE) on the PET images. PVE is a physical limitation resulting from the poor spatial resolution of PET systems (4-5 mm) that strongly afects the estimation of radioactivity concentration within structures less than two or three times the PET spatial resolution [14, 15]. Several techniques have been advanced to compensate for PVE in PET [15–20]. Among all PVE correction methods, more common ones are based on multiplicative numeri- cal factors (recovery coeicients, RC), recovering the local radioactivity concentration within any small structure which uptakes 18 F-FDG. RC can be derived from PET experimental measurements of small radioactive objects in a priori known object-to-background radioactivity concentration ratio.