Filippo Attivissimo

Acquisition Times in Magnetic Resonance Imaging: Optimization in Clinical Use

Nuclear magnetic resonance imaging is a routine clinical system used for whole-body patient scanning that provides 3D images. Recent technological innovations have encouraged the use of this technology for noninvasive coronary, heart, and chest investigation or for research applications, but the image quality of this technique depends on several factors. Some parameters are linked to the apparatus designed to acquire the magnetic resonance image, whereas others can be controlled by the user. In this paper, the authors analyze the software-controlled magnetic-resonance-imaging parameters to reduce the health examination acquisition time by assuring a good quality of the images. This objective is of fundamental importance to both increase the number of clinical tests produced with this equipment and to reduce the radiation doses in the patients. For this purpose, the parameters that influence the time acquisition and the signal-to-noise ratio were investigated, and a software platform for optimizing the imaging acquisition time was developed.

Time Domain Reflectometry Technique for Monitoring of Liquid Characteristics

Time domain reflectometry (TDR) technique is widely used in hydrology and soil science for accurate and flexible soil water content measurements. The most attractive advantages concerning the considered TDR measurement system are: good precision and accuracy, high reliability of the measuring head, a unique approach of pulsing a long coaxial probe and analysing the reflected voltage signature caused by changes in impedance, capability of multiplexing several probes, possibility of remotely acceding, controlling and electronically retrieving and transmitting data through existing telecommunication technologies. A time domain reflectometer transmits the incident signal, an ultra short rise time (200 ps), step voltage pulse, along the transmission line and records the travel time and the magnitude of all reflected signals (echo) returning from the controlled system. Changes in impedance (capacitance, inductance and resistance) causing electromagnetic discontinuities that reflect voltage can be located, particularly, for liquid level and dielectric properties monitoring purposes. The above mentioned discontinuities result from impedance changes produced by changes in the dielectric constant. The time domain reflectometry method used in this research has the purpose to monitor the behavior of different liquid substances, detecting their levels and giving information about their characteristics, such as volumetric content, dielectric constant, electrical conductivity, as well as the identification of different interfaces. Furthermore, the main objective of the present work is to develop an interpretation method for the analysis of TDR signal that, associated with a simple calibration procedure and with a suitable probe design can ensure, at the same time, quantitative and qualitative liquid monitoring

Assessment of the uncertainty associated with systematic errors in digital instruments: an experimental study on offset errors

This paper deals with the assessment of the uncertainty due to systematic errors, particularly in A/D conversion-based instruments. The problem of defining and assessing systematic errors is briefly discussed, and the conceptual scheme of gauge repeatability and reproducibility is adopted. A practical example regarding the evaluation of the uncertainty caused by the systematic offset error is presented. The experimental results, obtained under various ambient conditions, show that modelling the variability of systematic errors is more problematic than suggested by the ISO 5725 norm. Additionally, the paper demonstrates the substantial difference between the type B uncertainty evaluation, obtained via the maximum entropy principle applied to manufacturers specifications, and the type A (experimental) uncertainty evaluation, which reflects actually observable reality. Although it is reasonable to assume a uniform distribution of the offset error, experiments demonstrate that the distribution is not centred and that a correction must be applied. In such a context, this work motivates a more pragmatic and experimental approach to uncertainty, with respect to the directions of supplement 1 of GUM.