Luís Fernando de Oliveira

3D histomorphometric quantification of trabecular bones by computed microtomography using synchrotron radiation.

Conventional bone histomorphometry is an important method for quantitative evaluation of bone microstructure. X-ray computed microtomography is a non-invasive technique, which can be used to evaluate histomorphometric indices in trabecular bones (BV/TV, BS/BV, Tb.N, Tb.Th, Tb.Sp). In this technique, 3D images are used to quantify the whole sample, differently from the conventional one, in which the quantification is performed in 2D slices and extrapolated for 3D case. In this work, histomorphometric quantification using synchrotron 3D X-ray computed microtomography was performed to quantify the bone structure at different skeletal sites as well as to investigate the effects of bone diseases on quantitative understanding of bone architecture. The images were obtained at Synchrotron Radiation for MEdical Physics (SYRMEP) beamline, at ELETTRA synchrotron radiation facility, Italy. Concerning the obtained results for normal and pathological bones from same skeletal sites and individuals, from our results, a certain declining bone volume fraction was achieved. The results obtained could be used in forming the basis for comparison of the bone microarchitecture and can be a valuable tool for predicting bone fragility.

TOFPET2: a high-performance ASIC for time and amplitude measurements of SiPM signals in time-of-flight applications

We present a readout and digitization ASIC featuring low-noise and low-power for time-of flight (TOF) applications using SiPMs. The circuit is designed in standard CMOS 110 nm technology, has 64 independent channels and is optimized for time-of-flight measurement in Positron Emission Tomography (TOF-PET). The input amplifier is a low impedance current conveyor based on a regulated common-gate topology. Each channel has quad-buffered analogue interpolation TDCs (time binning 20 ps) and charge integration ADCs with linear response at full scale (1500 pC). The signal amplitude can also be derived from the measurement of time-over-threshold (ToT). Simulation results show that for a single photo-electron signal with charge 200 (550) fC generated by a SiPM with 320 pF capacitance the circuit has 24 (30) dB SNR, 75(39) ps r.m.s. resolution, and 4(8) mW power consumption. The event rate is 600 kHz per channel, with up to 2 MHz dark counts rejection.

Artificial neural networks applied to bone recognition in X-Ray computer microtomography imaging for histomorphometric analysis

Bone Histomorphometry is an important analysis in preventing and treatment of cancer and osteoporosis patients, providing quantitative information about the bone structure. X-Ray Micro-Computer Tomography is a non-invasive and non-destructive imaging technique, with a high space resolution that enables magnified images. In the histomorphometric analysis of such images, it is possible to use filters and binarization, nevertheless these techniques may cause loss of information. In this paper we describe the usage of Artificial Neural Networks (ANNs) in Microtomography X-Ray imaging bone recognition as a part of a histomorphometric analysis research with raw images obtained at the Synchrotron Radiation for Medical Physics (SYRMEP) beamline of the ELETTRA Laboratory at Trieste, Italy. A Multilayer Perceptron Model for the ANNs with Error Back-Propagation and supervised learning has been used in the recognition task. The classification of bone subimages yielded a Receiver Operating Characteristic Curve with an area under curve of 1.000, which means that the ANN is able to distinguish successfully the bone mass. The images obtained are also depicted herein. The quality and characteristics of the X-Ray Computer Microtomography are compatible with the ANN-based proposed methodology, avoiding the loss of information due to image manipulation.

Mapping lead distribution in bones by dual-energy computed microtomography with synchrotron radiation

We investigated the feasibility of the micro computed tomography dual-energy imaging to map of lead deposition inside bone. Femora of Wistar rats were imaged at the SYRMEP beamline at the ELETTRA synchrotron facility at Trieste, Italy, using two different energies, one just below (15.75 keV) and other just above (16.10 keV) the L-edge absorption energy of lead. By utilizing dual-energy micro-tomography the distribution-map of lead in the specimens was obtained. On the three-dimensional subtraction images, lead distribution could be clearly visualized over trabecular and cortical bone tissues.

Phosphorus migration analysis using synchrotron radiation in soil treated with Brazilian granular fertilizers

The aim of this study was to evaluate the phosphorus (P) mobility in a tropical Brazilian soil type red Oxisol treated with three different forms of granular fertilizer. Total Reflection X-Ray Fluorescence (TXRF) was applied to determine the concentration of P at different distances from granular fertilizer application point. The results showed that most of the P from fertilizers tends to concentrate in a region of up to 10mm around the place of the fertilizer deposition.