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• Total Body Irradiation in-vivo dosimetry data over 10 years were analyzed. • Monitor Units' median percentage difference from planned was limited. • Median percentage dose difference at six anatomical locations was inside 10 % range. • The neck region showed the highest dosimetric differences from planned. • In-vivo dosimetry omission impact was evaluated, leading to interesting results. Myeloablative Total Body Irradiation (TBI) used in our Institution, as part of the conditioning scheme for haematopoietic stem cell transplantation, is an extended-distance supine technique that has been implemented using a 15 MV LINAC beam, lead lung compensators, PMMA, and water bolus to improve homogeneity. This study reviews in-vivo dosimetry (IVD) over 10 years of treatments, assessing the technique's robustness, accuracy, and efficiency. A 2-lateral opposite fields plan was calculated from planning CT with validated Oncentra TPS (Elekta AB, Sweden). Monitor units (MUs), lung compensators shape and thickness were calculated to deliver the prescription dose (12 Gy in 6 bi-daily fractions or 9.9 Gy in 3 daily fractions) to the patient's abdomen midline at the umbilical level, maintaining lung dose within ±5 % range of prescription. Data from 103 patients, of which more than 87 % were pediatric, were retrieved and analyzed for a total of 537 treatment fractions. The impact of IVD omission was evaluated, supposing doing it only once or in the first two fractions, if necessary. Median ΔMU from planned was −1.2 %. Median percentage dose deviation from prescription in 6 anatomical regions was below 2 %. IVD omission could have resulted in an increase of 7 patients registering at least one anatomical region outside the ±5 % dose range at the end of treatment. It is possible to confirm the implemented technique's robustness and accuracy in delivering the prescribed dose under IVD monitoring. Nevertheless, this technique and associated IVD are time-consuming and IVD omission could be assessed with limited drawbacks. [ABSTRACT FROM AUTHOR]

Purpose the alignment of transmission and emission images is a crucial requirement in nuclear medicine hybrid scanners (PET/CT and SPECT/CT). EANM and Italian (AIFM-AIMN) guidelines prescribe to perform the alignment test by using specific manufacturer phantoms combined with closed source analysis software packages supplied by the vendor. The purpose of this work was to propose a full independent tool for evaluating CT and PET images alignment by scanning a commercially available phantom. Methods PET/CT data were acquired on a Discovery-IQ PET/CT system (GE Healthcare, Milwaukee, USA) using a dedicated phantom (PET/CT Phantom, Data Spectrum Corporation). A Matlab code was written to perform image analysis. To evaluate translations, 5 coplanar spheres filled with 18F-FDG radioactive solution were considered through these steps: segmentation of the spheres using a region growing algorithm, calculation of the centre of mass for each sphere and comparison of its coordinates in PET and CT set of images. Rotations were assessed by considering the positioning of 3 aluminium rods filled with radioactive solution in PET and CT: the angles shown in figure were calculated in sagittal, coronal and axial views. A series of nominal translations (3–5–8–10 mm in the three spatial directions) and rotations (swivel, tilt and roll, 3.2° up to 6.8°) were simulated to validate the method. Results the sensibility of the method turned out to be less than 1 mm for translations and between 1.0° and 1.7° for rotations. The reproducibility (coefficient of variation over 5 identical acquisitions) was less than 1% both for translations and for rotations. Linearity considered the detected translation/rotation as a function of the nominal one: the angular coefficient for the linear regression ranged from 0.87 (Y-axis translation) to 1.35 (tilt rotation). Conclusions the method proposed represents an alternative to the use of vendor specific phantoms and software analysis, providing a general validity across each type of scanner. [ABSTRACT FROM AUTHOR]

Purpose Aim of this study was to investigate if with new PET/CT technologies (large FOV – Field of View - and High Sensitivity) and reconstruction algorithms (RR – Regularized Reconstruction -) the counts statistic variation in terms of time/FOV can influence quantification and consequently metabolic response evaluation after treatment. Methods 43 target lesions (size ≥ 0.7 cm, median 2.5 cm) were selected in 35 patients with solid tumors. All lesions were evaluated with a baseline PET scan before chemotherapy and/or radiotherapy (1.5 min/FOV, standard iterative algorithm OSEM and RR reconstruction) and a follow up scan after treatment on a Discovery IQ PET/CT scanner (GE Healthcare, Milwaukee, WI, USA, sensitivity 23.3 cps/kBq at centre FOV). Follow up scans were acquired in List Mode at 2 min/FOV and reconstructed at 1.5 and 1 min/FOV both using standard OSEM and RR algorithms. SUL peak (Lean Body Mass SUV) was measured for each target lesion in baseline and follow up PET datasets with dedicated software; statistical analysis was performed to evaluate the difference in quantification obtained from the PET datasets with different time/FOV, both for OSEM and RR reconstructions. For any pair of PET datasets metabolic response for each lesion was assessed on the base of SUL peak variation, with a threshold of 30% considered as significant according to PERCIST criteria [1]. Results Baseline PET/CT scans showed a dependence on the reconstruction algorithm (p < 0.0001, paired t-test), with RR proving better. No statistically significant difference was found comparing SUL peak values associated to different time/FOV: p = 0.9943 and p = 0.9554 for OSEM and RR respectively, using the rank sum test. Target lesion classification for any pair of datasets is reported in the Table 1. Conclusions Quantification and metabolic response assessment were independent on counts statistics (time/FOV), thus on acquisition time, which can be very useful in routine clinical practice when patients disease or clinical workflow could require more flexible protocols, including lower scan duration. [ABSTRACT FROM AUTHOR]

Purpose Quality assurance in advanced and quantitative magnetic resonance techniques is strongly recommended [1–3]. The aim of this study was to propose and validate across various clinical scanner systems a straightforward quality assurance procedure for proton Magnetic Resonance Spectroscopy (MRS). Methods Eighteen clinical 1.5 T and 3 T scanners for MRS were enrolled in the study. The protocol included 3 sets of single voxel PRESS acquisitions without water signal suppression, repeated 4/5 times within approximately 2 months and performed using a standard water phantom supplied to all centres. Water peak linewidth (LW), water peak area (AP) and phantom T2 were estimated. Results LW values ranged from 0.4 Hz to 1.6 Hz, with 3 T and 1.5 T scanner systems showing similar performances. Coefficient of variation (CV) of LW values for repeated measurements were lower than 35% (except for only 3 scanners). AP showed significant (p < 0.05) linear correlation with voxel volume (r > 0.99 and 0.95 for 1.5 T and 3 T scanner systems, respectively). CV of AP for different spatial positions was less than 25%, and no relevant difference was observed between 3 T and 1.5 T scanners. Mean phantom T2 value and CV for repeated measurements were 1147 ms and 4%, respectively, for 1.5 T scanners, and 1010 ms and 9%, respectively, for 3 T scanners. Conclusions We proposed a straightforward multiparametric and not time consuming quality control protocol for MRS, which can be included in routine quality assurance procedures. The protocol has been validated and proven to be feasible in a multicentre intercomparison study of 18 clinical 1.5 T and 3 T scanner systems. [ABSTRACT FROM AUTHOR]

Purpose Important advancements have been made in PET image reconstruction algorithms, among the newest point spread function (PSF) and noise statistics modelling (NSM) can be accounted for. This work presents the preliminary results of the application of these reconstruction techniques on 3 state-of-the-art PET/CT scanners with and without time-of-flight (TOF) technique. Methods A Ge68 NEMA/IEC phantom (Data Spectrum, Durham, NC) filled with 68Ge in an epoxy resin was used. The activity concentrations in the spheres and in the background were measured with a radionuclide calibrator tested against a NIST traceable source and were respectively 40.67 kBq/ml and 10.58 kBq/ml at reference time (uncertainty ± 3)%. Nominal sphere-to-background ratio was 3.84. Total activity in the phantom was 108.4 MBq. The phantom was acquired for a prolonged time according to decay correction equivalent to 1.5 min per frame at the reference date on each PET scanner and reconstructed with clinical reconstruction parameters with traditional (OSEM) and by combining advanced modalities, when present: PSF, TOF, TOF + PSF, NSM. For each PET scanner and each reconstruction modality the maximum Recovery Coefficient (RCmax) values were evaluated for each visible sphere. RCmax were normalised to background activity to cancel calibration bias among scanners. Results The Figure presents the RCmax averaged on the 3 PET/CT scanners together with the RC limits suggested by EARL. Error bars represent one standard deviation. Conclusions the RC obtained with the 3 state-of-the-art non digital PET/CT scanners demonstrate clearly that, independently of the reconstruction method used, modern PET/CT scanner outperforms respect to older one described by EARL curve. Moreover, applying more advanced reconstruction techniques progressively enhances RC, NSM reconstruction being the most promising setup. Even if RCmax of different scanners converge at larger (>22 mm) and smaller (10 mm) spheres, the overestimations observed in the size between 1 and 2 cm are currently under investigation. [ABSTRACT FROM AUTHOR]