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We present here a direct least-squares estimation (DLSE) method for the determination of renal kinetic parameters from sequences of very fast acquisitions performed with a three-headed single photon emission computed tomography (SPECT) system. A simple linear model for the behavior of the radiopharmaceutical, as well as a spatial model for its spatial distribution are defined. The model enables one to estimate the kinetic parameters directly from the projections, once the plasma concentration function is known. A new technique for the accurate reconstruction of time-radioactivity curves based on the direct reconstruction of the region-of-interest contents from a series of data from three-projections is presented. The technique is used to determine the plasma concentration function with a sub-second time resolution. The spatially-variant geometrical response is also included in the model to compensate for the spatial resolution of the SPECT system. Results obtained from simulations are presented. Basic spatial and time features of the simulations are derived from a patient study. Noise and segmentation errors are also simulated. The DLSE method is compared with the conventional one of deriving kinetic parameters from the time series of reconstructed images. The standard deviation of results given by DLSE is less than 2%, whereas with the conventional method it is between 5% and 6%. Within the limit of statistical fluctuations, DLSE results are unbiased whereas those of the conventional method are overestimated by 24%. Index Terms--Dynamic single photon emission computed tomography (SPECT), kinetic parameter estimation.

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The paper presents the evaluation plan and the first results of DIDeL (Didactics in e-Learning), a research and development project of the University of Florence, aimed at promoting faculty professional development on e-learning methods and technologies. From a theoretical point of view the project is based on a multi-levels model characterized by the combination of methodological approaches and teaching tools. The evaluation plan reflects this articulation with the aim to measure users' satisfaction, the impact of the programme on teachers' techno-didactic competences on the short and medium run, as well as the impact on students' career progression. Specifically, this paper illustrates and discusses the results of a questionnaire administered online to all the teachers who participated in at least one of the project's training activities during the first half of 2018: it was investigated the level of satisfaction of training and teachers' self-perception of learning in terms of knowledge and skills. 166 teachers answered the questionnaire. The results show a high level of appreciation for the various types of training initiatives, which confirms the design hypotheses and the methodologies adopted. [ABSTRACT FROM AUTHOR]

Copyright of Form@re is the property of Firenze University Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Multihole collimators are the most important piece of instrumentation in determining the tradeoff between spatial resolution and noise in nuclear medicine images. Recently, we found that the collimator-to-detector gap greatly influences the hole-pattern artifacts. In addition, we also showed that specific values of the gap exist which minimize the artifacts: here we call this phenomenon ‘penumbral masking’ (PM). In this paper, we study the matter in greater detail and we take PM into account in the problematic context of designing high-energy collimators by, basically, substituting the conventional hole-array pattern constraint with a mathematical expression of the PM effect. With this approach we found that a solution to the problem of maximizing sensitivity for a given spatial resolution always exists while, without the PM concept, in the case of lead (Pb), a solution exists below 300 KeV, a sub-optimal solution can be found within the 300—320 KeV range and no solution at all exists beyond 320 KeV. Thus, one is able to minimize the hole-pattern artifacts while designing high-energy collimators even if a somewhat lower sensitivity has to be accepted: for example, with lead, at 511 KeV, sensitivity is reduced by 20% compared to what it would be without the introduction of PM. When high energies are involved, even with our approach the weight constraint is a major problem, but this does not affect the capability of reducing the hole-pattern artifacts. However, even when the theoretical solution may not be feasible, this approach clarifies the design of high-energy collimators. [ABSTRACT FROM AUTHOR]