Sabrina Morzenti

Performance measurements for the PET/CT Discovery-600 using NEMA NU 2-2007 standards.

PURPOSEnThe aim of this study was to assess the performance measurements of the new PET/CT system Discovery-600 (D-600, GEMS, Milwaukee, WI).nnnMETHODSnPerformance measures were obtained with the National Electrical Manufacturers Association (NEMA) NU 2-2007 procedures.nnnRESULTSnThe transverse (axial) spatial resolution FWHMs were 4.9 (5.6) mm and 5.6 (6.4) mm at 1 and 10 cm off axis, respectively. The sensitivity (average at 0 and 10 cm) was 9.6 cps/kBq. The scatter fraction was 36.6% (low energy threshold: 425 keV). The NEC peak rate (k=1) was 75.2 kcps at 12.9 kBq/cc. The hot contrasts for 10, 13, 17, and 22 mm spheres were 41%, 51%, 62%, and 73% and the cold contrasts for 28 and 37 mm spheres were 68% and 72%.nnnCONCLUSIONSnThe Discovery-600 has good performance for the NEMA NU 2-2007 parameters, particularly in improved sensitivity compared to the scanners of the same Discovery family, D-ST and D-STE.

Comparative analysis of iterative reconstruction algorithms with resolution recovery for cardiac SPECT studies. A multi-center phantom study

BackgroundThis investigation used image data generated by a physical phantom over a wide range of count statistics to evaluate the effectiveness of several of the newer commercially available SPECT reconstruction iterative algorithms (IRR) in improving perfusion defect contrast and spatial resolution, while controlling image noise.MethodsA cardiac phantom was imaged using four different gamma cameras over a wide range of counts statistics (from 6 to 0.8 Mcounts). Images were reconstructed with FBP, OSEM, and the IRR available on site. IRR were applied without corrections (IRR NC), with attenuation correction (IRR AC), scatter correction (IRR SC), and attenuationxa0+xa0scatter corrections (IRR SCAC). Four image performance indices related to spatial resolution, contrast, and image noise were analyzed.ResultsIRR NC always determined significant improvements in all indices in comparison to FBP or OSEM. Improvements were emphasized with IRR SC and IRR SCAC. Count reduction from 6 to 1.5 Mcounts did not impair the performances of any of the considered indices.ConclusionsThis is the first study comparing the relative performance of different, commercially available, IRR software, over a wide range of count statistics; the additional effect of scatter and attenuation corrections, alone or in combination, was also evaluated. Our results confirm that IRR algorithms produce substantial benefits with respect to conventional FBP or OSEM reconstruction methods, as assessed through different figures of merit, in particular when SC and/or SCAC are also included.

Comparative evaluation of CT-based and respiratory-gated PET/CT-based planning target volume (PTV) in the definition of radiation treatment planning in lung cancer: preliminary results

PurposeThe aim of this study was to compare planning target volume (PTV) defined on respiratory-gated positron emission tomography (PET)/CT (RG-PET/CT) to PTV based on ungated free-breathing CT and to evaluate if RG-PET/CT can be useful to personalize PTV by tailoring the target volume to the lesion motion in lung cancer patients.MethodsThirteen lung cancer patients (six men, mean age 70.0xa0years, 1 small cell lung cancer, 12 non-small cell lung cancer) who were candidates for radiation therapy were prospectively enrolled and submitted to RG-PET/CT. Ungated free-breathing CT images obtained during a PET/CT study were visually contoured by the radiation oncologist to define standard clinical target volumes (CTV1). Standard PTV (PTV1) resulted from CTV1 with the addition of 1-cm expansion of margins in all directions. RG-PET/CT images were contoured by the nuclear medicine physician and radiation oncologist according to a standardized institutional protocol for contouring gated images. Each CT and PET image of the patient’s respiratory cycle phases was contoured to obtain the RG-CT-based CTV (CTV2) and the RG-PET/CT-based CTV (CTV3), respectively. RG-CT-based and RG-PET/CT-based PTV (PTV2 and PTV3, respectively) were then derived from gated CTVs with a margin expansion of 7–8xa0mm in head to feet direction and 5xa0mm in anterior to posterior and left to right direction. The portions of gated PTV2 and PTV3 geometrically not encompassed in PTV1 (PTV2 out PTV1 and PTV3 out PTV1) were also calculated.ResultsMean ± SD CTV1, CTV2 and CTV3 were 30.5u2009±u200933.2, 43.1u2009±u200943.2 and 44.8u2009±u200945.2xa0ml, respectively. CTV1 was significantly smaller than CTV2 and CTV3 (pu2009=u20090.017 and 0.009 with Student’s t test, respectively). No significant difference was found between CTV2 and CTV3. Mean ± SD of PTV1, PTV2 and PTV3 were 118.7u2009±u200994.1, 93.8u2009±u200980.2 and 97.0u2009±u200983.9xa0ml, respectively. PTV1 was significantly larger than PTV2 and PTV3 (pu2009=u20090.038 and 0.043 with Student’s t test, respectively). No significant difference was found between PTV2 and PTV3. Mean ± SD values of PTV2 out PTV1 and PTV3 out PTV1 were 12.8u2009±u200925.4 and 14.3u2009±u200925.9xa0ml, respectively. The percentage values of PTV2 out PTV1 and PTV3 out PTV1 were not lower than 10xa0% of PTV1 in 6/13 cases (46.2xa0%) and than 20xa0% in 3/13 cases (23.1xa0%).ConclusionOur preliminary data showed that RG-PET/CT in lung cancer can affect not only the volume of PTV but also its shape, as demonstrated by the assessment of gated PTVs outside standard PTV. The use of a gating technique is thus crucial for better delineating PTV by tailoring the target volume to the lesion motion in lung cancer patients.

Impact of speed and magnitude of weight loss on the development of brain trophic changes in adolescents with anorexia nervosa: a case control study

BackgroundAnorexia nervosa commonly arises during adolescence and is associated with more than one medical morbidity. Abnormalities in brain structure (defined as “pseudoatrophy”) are common in adolescents with anorexia nervosa; however, their correlations with endocrinological profiles and clinical parameters are still unclear. In particular, no study has described the impact of BMI (body mass index) variations (speed and magnitude of weight loss) on cerebral trophism changes.MethodsEleven adolescents with anorexia nervosa and 8 healthy controls underwent cerebral MRI (magnetic resonance imaging) examination to obtain global and partial volumes (gray matter, white matter and cerebrospinal fluid) and clinical evaluation. The Mann-Whitney U test was used to compare partial volumes and clinical variables between cases and controls. The Spearman non-parametric test was performed in order to explore correlations between the variables studied.ResultsThe patients diagnosed with AN showed significantly increased cerebrospinal fluid (CSF) volumes and decreased total gray (GM) and white matter (WM) volumes. The degree of weight loss (deltaBMI) correlated inversely with the GM volume; the increase of CSF compartment correlated directly with the rapidity of weight loss (DeltaBMI/disease duration).ConclusionsThis study suggests a correlation between cerebral alterations in AN and the speed and magnitude of weight loss, and outlines its importance for the therapeutic treatment.

Survey on retinopathy of prematurity (ROP) in Italy

BackgroundThis study aims to investigate the incidence and the relative risk factors of retinopathy of prematurity (ROP) and posterior-ROP (P-ROP): ROP in Zone I and posterior Zone II, as well as to analyze the occurrence of surgical treatment of ROP and to evaluate the short term outcome of the disease in Italy.MethodsIt is a prospective multicenter observational study; all infants with a birth weight (BW)u2009≤u2009750xa0g and/or a gestational age (GA) ≤27xa0weeks born between January 1st 2008 and December 31st 2009 in 25 III level Italian neonatal intensive care units were eligible for the study.Results421 infants were examined: 265 (62.9%) developed ROP and 102 (24.2%) P-ROP.Following the multivariate analysis erythropoietin-therapy (pu2009<u20090.0001) and intraventricular hemorrhage (IVH) (pu2009=u20090.003) were significantly associated with ROP while gestational age ≤24xa0weeks (pu2009=u20090.011) and sepsis (pu2009=u20090.002) were associated with the onset of P-ROP. Eighty nine infants (34%) required surgical treatment; following the multivariate analysis P-ROP was an independent factor associated with the need of surgical treatment (pu2009<u20090.0001). A favorable outcome was reported in 251 (94.7%) newborns affected by ROP. Adverse outcome occurred in 14 patients: all of them underwent surgery and showed P-ROP.ConclusionsP-ROP is the most aggressive type of ROP. It associates with lower GA and sepsis. Obstetricians and Neonatologists must focus on the reduction of severe preterm births and on the prevention of neonatal early and late onset sepsis in order to reduce the incidence of P-ROP.

Respiratory motion management in PET/CT: applications and clinical usefulness

BACKGROUND AND OBJECTIVEnBreathing movement can introduce heavy bias in both image quality and quantitation in PET/CT. The aim of this paper is a review of the literature to evaluate the benefit of respiratory gating in terms of image quality, quantification and lesion detectability.nnnMETHODSnA review of the literature published in the last 10 years and dealing with gated PET/CT technique has been performed, focusing on improvement in quantification, lesion detectability and diagnostic accuracy in neoplastic lesion. In addition, the improvement in the definition of radiotherapy planning has been evaluated.nnnRESULTSnThere is a consistent increase of the Standardized Uptake Value (SUV) in gated PET images when compared to ungated ones, particularly for lesions located in liver and in lung. Respiratory gating can also increase sensitivity, specificity and accuracy of PET/CT. Gated PET/CT can be used for radiation therapy planning, reducing the uncertainty in target definition, optimizing the volume to be treated and reducing the possibility of missing during the dose delivery. Moreover, new technologies, able to define the movement of lesions and organs directly from the PET sinogram, can solve some problems that currently are limiting the clinical use of gated PET/CT (i.e.: extended acquisition time, radiation exposure).nnnCONCLUSIONnThe published literature demonstrated that respiratory gating PET/CT is a valid technique to improve quantification, lesion detectability of lung and liver tumors and can better define the radiotherapy planning of moving lesions and organs. If new technical improvements for motion compensation will be clinically validated, gated technique could be applied routinely in any PET/CT scan.

An Adaptive Thresholding Method for BTV Estimation Incorporating PET Reconstruction Parameters: A Multicenter Study of the Robustness and the Reliability

Objective. The aim of this work was to assess robustness and reliability of an adaptive thresholding algorithm for the biological target volume estimation incorporating reconstruction parameters. Method. In a multicenter study, a phantom with spheres of different diameters (6.5–57.4u2009mm) was filled with 18F-FDG at different target-to-background ratios (TBR: 2.5–70) and scanned for different acquisition periods (2–5u2009min). Image reconstruction algorithms were used varying number of iterations and postreconstruction transaxial smoothing. Optimal thresholds (TS) for volume estimation were determined as percentage of the maximum intensity in the cross section area of the spheres. Multiple regression techniques were used to identify relevant predictors of TS. Results. The goodness of the model fit was high (R 2: 0.74–0.92). TBR was the most significant predictor of TS. For all scanners, except the Gemini scanners, FWHM was an independent predictor of TS. Significant differences were observed between scanners of different models, but not between different scanners of the same model. The shrinkage on cross validation was small and indicative of excellent reliability of model estimation. Conclusions. Incorporation of postreconstruction filtering FWHM in an adaptive thresholding algorithm for the BTV estimation allows obtaining a robust and reliable method to be applied to a variety of different scanners, without scanner-specific individual calibration.

Added diagnostic value of respiratory-gated 4D 18F–FDG PET/CT in the detection of liver lesions: a multicenter study

PurposeThe aim of the present study was to evaluate the added diagnostic value of respiratory-gated 4D18F–FDG PET/CT in liver lesion detection and characterization in a European multicenter retrospective study.MethodsFifty-six oncological patients (29 males and 27 females, mean age, 61.2 ± 11.2xa0years) from five European centers, submitted to standard 3D–PET/CT and liver 4D–PET/CT were retrospectively evaluated. Based on visual analysis, liver PET/CT findings were scored as positive, negative, or equivocal both in 3D and 4D PET/CT. The impact of 4D–PET/CT on the confidence in classifying liver lesions was assessed. PET/CT findings were compared to histology and clinical follow-up as standard reference and diagnostic accuracy was calculated for both techniques. At semi-quantitative analysis, SUVmax was calculated for each detected lesion in 3D and 4D–PET/CT.ResultsOverall, 72 liver lesions were considered for the analysis. Based on visual analysis in 3D–PET/CT, 32/72 (44.4%) lesions were considered positive, 21/72 (29.2%) negative, and 19/72 (26.4%) equivocal, while in 4D–PET/CT 48/72 (66.7%) lesions were defined positive, 23/72 (31.9%) negative, and 1/72 (1.4%) equivocal. 4D–PET/CT findings increased the confidence in lesion definition in 37/72 lesions (51.4%). Considering 3D equivocal lesions as positive, sensitivity, specificity, and accuracy were 88.9, 70.0, and 83.1%, respectively, while the same figures were 67.7, 90.0, and 73.8% if 3D equivocal findings were included as negative. 4D–PET/CT sensitivity, specificity, and accuracy were 97.8, 90.0, and 95.4%, respectively, considering equivocal lesions as positive and 95.6, 90.0, and 93.8% considering equivocal lesions as negative. The SUVmax of the liver lesions in 4D–PET (meanxa0±xa0SD, 6.9xa0±xa03.2) was significantly higher (pxa0<xa00.001) than SUVmax in 3D–PET (meanxa0±xa0SD, 5.2xa0±xa02.3).ConclusionsRespiratory-gated PET/CT technique is a valuable clinical tool in diagnosing liver lesions, reducing 3D undetermined findings, improving diagnostic accuracy, and confidence in reporting. 4D–PET/CT also improved the quantification of SUVmax of liver lesions.

[OA143] Application of new algorithms in PET image reconstruction: Preliminary results

Purpose Important advancements have been made in PET image reconstruction algorithms, among the newest modelling of the point spread function (PSF) and noise statistics modelling (NSM) can be accounted for. Quantitative 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 are presented. Methods and materials A 68Ge-NEMA phantom based on a standard IQ body phantom (Data Spectrum, Durham, NC) filled with 68Ge in an epoxy resin was used. The activity concentrations in the spheres (internal diameter-IDu202f=u202f6, 10, 13, 17, 22, 28, 37u202fmm) and in the background were measured with a radionuclide calibrator tested against a NIST traceable source and were respectively 40.67kBq/ml and 10.58u202fkBq/ml at reference time (uncertainty ± 3%). Nominal sphere-to-background ratio was 3.84. Total activity in the phantom was 108.4u202fMBq at calibration. Acquisition time was adjusted according to the age of the phantom to meet 1.5u202fmin per frame at the reference date on each PET scanner and reconstructed with variable reconstruction parameters (iterations: 48, 72; amplitude of Gaussian filter: 5, 6.4, 8u202fmm) with traditional (OSEM) and by combining advanced modalities, when present: PSF, TOF, TOF+PSF, NSM. For each PET scanner and each reconstruction modality maximum Recovery Coefficient (RCmax) values were evaluated for each visible sphere. RCmax were normalised to 37u202fmm ID sphere result. Results For each reconstructed modality, RCmax (mean ± sd) were averaged on different reconstruction parameters and PET scanners and for increasing sphere ID respectively 6, 10, 13, 17, 22, 28, 37u202fmm resulted: - OSEM: (0.31u202f ± u202f0.03), (0.51u202f ± u202f0.05), (0.63u202f ± u202f0.03), (0.82u202f ± u202f0.03), (0.89u202f ± u202f0.03), (0.95u202f ± u202f0.04), (1u202f ± u202f0) - OSEM+TOF: (0.32u202f ± u202f0.01), (0.56u202f ± u202f0.08), (0.64u202f ± u202f0.07), (0.84u202f ± u202f0.03), (0.91u202f ± u202f0.00), (0.97u202f ± u202f0.04), (1u202f ± u202f0) - OSEM+PSF: (0.30u202f ± u202f0.01), (0.50u202f ± u202f0.04), (0.65u202f ± u202f0.05), (0.88u202f ± u202f0.04),(0.93u202f ± u202f0.02), (0.95u202f ± u202f0.04), (1u202f ± u202f0) - OSEM+PSF+TOF: (0.30u202f ± u202f0.01), (0.56u202f ± u202f0.08), (0.70u202f ± u202f0.11), (0.91u202f ± u202f0.03), (0.94u202f ± u202f0.00), (0.97u202f ± u202f0.04), (1u202f ± u202f0) - NSM: (0.30u202f ± u202f0.02), (0.67u202f ± u202f0.19), (0.84u202f ± u202f0.14), (0.94u202f ± u202f0.05), (0.98u202f ± u202f0.03), (0.98u202f ± u202f0.06), (1u202f ± u202f0) Conclusion 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. Higher differences are recorded for smaller spheres. Moreover, applying more advanced reconstruction techniques progressively enhances RC, NSM reconstruction being the most promising algorithm. Even if RCmax of different scanners converge at larger ( > 22u202fmm) and smaller (10u202fmm) spheres, the overestimations observed in the size between 1 and 2u202fcm are currently under investigation.

Motion Management in PET/CT: Technological Solutions

BACKGROUND AND OBJECTIVEnMotion due to patients breathing can introduce heavy bias in PET/CT, both in image quality and quantitation. This paper is a review of the main technical solutions available to manage movement in PET/CT studies: a) Respiratory Gated (RG), b) Motion Free (MF), c) End Expiration (EE), d) Banana Artefact Management (BAM) and e) Data Driven Gating (DDG).nnnMETHODSnThe most diffused solutions (RG, MF and EE) are based on LIST mode acquisition of a PET Field of View (4D FOV), centered on the anatomical region of interest; to link PET data not only to time and to spatial position but also to the corresponding breathing phase, the synchronized acquisition of the patients breathing curve is performed by an external tracking device. Different commercial tools to track and to record patient breathing cycle are available to associate the internal organ motion with a measurable external parameter; for example these systems can measure the pressure on a chest elastic belt, the air flow trough patient nose, the breath-in and breath-out air temperature or the markers movement on the thorax/ abdominal region. Recently DDG techniques are developed to correct respiratory motion without the help of external motion tracking devices and to obtain a comparable result to that based on standard RG protocols.nnnRESULTSnThe final result of an RG or DDG protocol is a sequence of 3D images showing organs and lesions movement; using the other motion management options a single 3D motion-free image is obtained without motion artefacts and degradation. Compared to the previously described options the BAM solution is not a real motion management protocol but just a Banana Artefact correction technique obtained using an Attenuation Correction Map calculated merging the Whole Body Helical CT with a Cine CT on the diaphragm area.nnnCONCLUSIONnThe motion management in PET/CT imaging shows benefits in terms of image quality, quantification and lesion detectability and it is useful both in diagnostic and radiotherapy planning.