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2 results on '"Paolo Turco"'

1. Analytical and experimental FWHM of a gamma camera: theoretical and practical issues

Author

Diego Cecchin, Davide Poggiali, Lucia Riccardi, Paolo Turco, Franco Bui, and Stefano De Marchi

Subjects
Gaussian, Splines, Gamma camera, FWHM, Resolution, Local interpolation, Medicine, Biology (General), QH301-705.5
Abstract

Introduction. It is well known that resolution on a gamma camera varies as a function of distance, scatter and the camera’s characteristics (collimator type, crystal thickness, intrinsic resolution etc). Manufacturers frequently provide only a few pre-calculated resolution values (using a line source in air, 10–15 cm from the collimator surface and without scattering). However, these are typically not obtained in situations resembling a clinical setting. From a diagnostic point of view, it is useful to know the expected resolution of a gamma camera at a given distance from the collimator surface for a particular setting in order to decide whether it is worth scanning patients with “small lesion” or not. When dealing with absolute quantification it is also mandatory to know precisely the expected resolution and its uncertainty in order to make appropriate corrections.Aim. Our aims are: to test a novel mathematical approach, the cubic spline interpolation, for the extraction of the full width at half maximum (FWHM) from the acquisition of a line source (experimental resolution) also considering measurement uncertainty; to compare it with the usually adopted methods such as the gaussian approach; to compare it with the theoretical resolution (analytical resolution) of a gamma camera at different distances; to create a web-based educational program with which to test these theories.Methods. Three mathematical methods (direct calculation, global interpolation using gaussian and local interpolation using splines) for calculating FWHM from a line source (planar scintigraphy) were tested and compared. A NEMA Triple Line Source Phantom was used to obtain static images both in air and with different scattering levels. An advanced, open-source software (MATLAB/Octave and PHP based) was created “ad hoc” to obtain and compare FWHM values and relative uncertainty.Results and Conclusion. Local interpolation using splines proved faster and more reliable than the usually-adopted Gaussian interpolation. The proposed freely available software proved effective in assessing both FWHM and its uncertainty.

Published
2015
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2. A new integrated dual time-point amyloid PET/MRI data analysis method

Author

Davide Poggiali, Osama Sabri, Franco Bui, Paolo Gallo, Paolo Turco, Diego Cecchin, Anna Chiara Frigo, Henryk Barthel, Solveig Tiepolt, Pietro Zucchetta, and Annachiara Cagnin

Subjects
Male, Time Factors, Amyloid, Partial volume, Amyloid pet, Amyloid tracers, Dementia, Dual time-point, PET/MRI, Quantification, Radiology, Nuclear Medicine and Imaging, 030218 nuclear medicine & medical imaging, 03 medical and health sciences, 0302 clinical medicine, Alzheimer Disease, Nuclear Medicine and Imaging, mental disorders, Stilbenes, Image Processing, Computer-Assisted, Medicine, Humans, Radiology, Nuclear Medicine and imaging, Stage (cooking), Analysis method, Aged, Retrospective Studies, Aniline Compounds, business.industry, Brain, General Medicine, Blood flow, Middle Aged, Magnetic Resonance Imaging, Positron-Emission Tomography, Female, business, Nuclear medicine, Radiology, Research setting, 030217 neurology & neurosurgery, Dual time point
Abstract

In the initial evaluation of patients with suspected dementia and Alzheimer’s disease, there is no consensus on how to perform semiquantification of amyloid in such a way that it: (1) facilitates visual qualitative interpretation, (2) takes the kinetic behaviour of the tracer into consideration particularly with regard to at least partially correcting for blood flow dependence, (3) analyses the amyloid load based on accurate parcellation of cortical and subcortical areas, (4) includes partial volume effect correction (PVEC), (5) includes MRI-derived topographical indexes, (6) enables application to PET/MRI images and PET/CT images with separately acquired MR images, and (7) allows automation. A method with all of these characteristics was retrospectively tested in 86 subjects who underwent amyloid (18F-florbetaben) PET/MRI in a clinical setting (using images acquired 90–110 min after injection, 53 were classified visually as amyloid-negative and 33 as amyloid-positive). Early images after tracer administration were acquired between 0 and 10 min after injection, and later images were acquired between 90 and 110 min after injection. PVEC of the PET data was carried out using the geometric transfer matrix method. Parametric images and some regional output parameters, including two innovative “dual time-point” indexes, were obtained. Subjects classified visually as amyloid-positive showed a sparse tracer uptake in the primary sensory, motor and visual areas in accordance with the isocortical stage of the topographic distribution of the amyloid plaque (Braak stages V/VI). In patients classified visually as amyloid-negative, the method revealed detectable levels of tracer uptake in the basal portions of the frontal and temporal lobes, areas that are known to be sites of early deposition of amyloid plaques that probably represented early accumulation (Braak stage A) that is typical of normal ageing. There was a strong correlation between age and the indexes of the new dual time-point amyloid imaging method in amyloid-negative patients. The method can be considered a valuable tool in both routine clinical practice and in the research setting as it will standardize data regarding amyloid deposition. It could potentially also be used to identify early amyloid plaque deposition in younger subjects in whom treatment could theoretically be more effective.

Published
2017

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