Abstract
Quantitative analyses in nuclear medicine are increasingly used, both for diagnostic and therapeutic purposes. The Partial Volume Effect (PVE) is the most important factor of loss of quantification in Nuclear Medicine, especially for evaluation in Region of Interest (ROI) smaller than the Full Width at Half Maximum (FWHM) of the PSF. The aim of this work is to present a new approach for the correction of PVE, using a post-reconstruction process starting from a mathematical expression, which only requires the knowledge of the FWHM of the final PSF of the imaging system used. After the presentation of the theoretical derivation, the experimental evaluation of this method is performed using a PET/CT hybrid system and acquiring the IEC NEMA phantom with six spherical “hot” ROIs (with diameters of 10, 13, 17, 22, 28, and 37 mm) and a homogeneous “colder” background. In order to evaluate the recovery of quantitative data, the effect of statistical noise (different acquisition times), tomographic reconstruction algorithm with and without time-of-flight (TOF) and different signal-to-background activity concentration ratio (3:1 and 10:1) was studied. The application of the corrective method allows recovering the loss of quantification due to PVE for all sizes of spheres acquired, with a final accuracy less than 17%, for lesion dimensions larger than two FWHM and for acquisition times equal to or greater than two minutes.
Highlights
Quantitative positron emission tomography/computed tomography (PET/CT) is currently used as a diagnostic/prognostic tool and for assessing therapy efficacy
It has been reported that PET reconstructions including Point Spread Function (PSF) compensation can increase SUVmax more than 66% in small nodal metastases in breast cancer or for NSCLC [3,4]
The method proposed here takes into account only how the system PSF affects the Partial Volume Effect (PVE) under ideal conditions of uniform radioactive source surrounded by uniform background
Summary
Quantitative positron emission tomography/computed tomography (PET/CT) is currently used as a diagnostic/prognostic tool and for assessing therapy efficacy. Quantification in fluorodeoxyglucose (FDG) PET/CT is mainly performed using standardized uptake value (SUV) [1]. It is well known that there are several sources of errors in SUV measurements, which are usually even poorly standardized between institutions with different PET equipment. Image reconstruction variability seems to have a prominent role in the unreliability of quantitative assessment of PET images mainly because of improvements in PET technology, which significantly affect SUV measurement. It has been reported that PET reconstructions including PSF compensation can increase SUVmax more than 66% in small nodal metastases in breast cancer or for NSCLC [3,4]
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