Application of Ga(68) -DOTA-exendin-4 PET/CT to localise an occult insulinoma

A 49 year old female presented to our Neuroendocrine Tumour (NET) centre with recurrent severe and disabling hypoglycaemia. She had previously been extensively investigated with a clinical and biochemical diagnosis of endogenous hyperinsulinemic hypoglycaemia although the source of hormonal hypersecretion could not be localised with MRI, EUS and (111) In-Octreotide scans. After extensive discussion the patient opted for blind surgical resection undergoing a pylorus-preserving pancreaticoduodenectomy in December 2010. Histological examination of the resected operative specimen demonstrated a normal pancreas with no evidence of neuroendocrine tumour. Consistent with this, post-surgery her hypoglycaemic symptoms persisted with fasting capillary blood glucose of 2.1-6.0 mmol/l with increasing hypoglycaemia unawareness. Consequently she sought alternative clinical opinions from two European Neuroendocrine Tumour Society (ENETS) Centres of Excellence who investigated her collaboratively. This article is protected by copyright. All rights reserved.

The potential role of endometrial nerve fibers in the pathogenesis of pain during endometrial biopsy at office hysteroscopy

We aimed to evaluate whether nerve fibers are present in the endometrial layer of patients submitted to office hysteroscopy and their potential contribution to the pathogenesis of pain during that procedure. Through a prospective case-control study performed in tertiary centers for women's health, endometrium samples were collected during operative office hysteroscopy from 198 cycling women who previously underwent laparoscopy and/or magnetic resonance imaging investigation for infertility assessment. Samples were classified according to the degree of the pain patients experienced and scored from values ranging from 0 (absence of discomfort/pain) to 10 (intolerable pain) on a 10-cm visual analog scale (VAS). The presence of nerve fiber markers (S100, NSE, SP, VIP, NPY, NKA, NKB, NKR1, NKR2, and NKR3) in the endometrium was also evaluated by morphologic and immunohistochemical analyses. We found that S-100, NSE, NKR1, NK-A, NK-B, VIP, and NPY, were immunolocalized in samples of endometrium, in significantly (P < .01, for all) higher levels in samples collected from patients with VAS score > 5 (group A) than ≤ 5 (group B) and significantly (P < .0001 for all) positively correlated with VAS levels. A statistically significant (P = .018) higher prevalence of endometriosis and/or adenomyosis was depicted in patients of group A than group B. Data from the present study led us to conclude that nerve fibers are expressed at the level of the functional layer of the endometrium and may contribute to pain generation during office hysteroscopy, mainly in women affected by endometriosis and adenomyosis.

Angraecum sesquipedale Pet. Th. : nebst Angabe seiner Kultur

vom Obergärtner Kraus

Design, Calibration, and Evaluation of Depth-of-Interaction-Capable PET Detector Modules

High-resolution, small-bore PET systems suffer from a tradeoff between system sensitivity, and image quality degradation. In these systems long crystals allow mispositioning of the line of response due to parallax error and this mispositioning causes resolution blurring, but long crystals are necessary for high system sensitivity. One means to allow long crystals without introducing parallax errors is to determine the depth of interaction (DOI) of the gamma ray interaction within the detector module. While DOI has been investigated previously, newly available solid state photomultipliers (SSPMs) well-suited to PET applications and allow new modules for investigation. Depth of interaction in full modules is a relatively new field, and so even if high performance DOI capable modules were available, the appropriate means to characterize and calibrate the modules are not. This work presents an investigation of DOI capable arrays and techniques for characterizing and calibrating those modules. The methods introduced here accurately and reliably characterize and calibrate energy, timing, and event interaction positioning. Additionally presented is a characterization of the spatial resolution of DOI capable modules and a measurement of DOI effects for different angles between detector modules. These arrays have been built into a prototype PET system that delivers better than 2.0 mm resolution with a single-sided-stopping-power in excess of 95% for 511 keV g's. The noise properties of SSPMs scale with the active area of the detector face, and so the best signal-to-noise ratio is possible with parallel readout of each SSPM photodetector pixel rather than multiplexing signals together. This work additionally investigates several algorithms for improving timing performance using timing information from multiple SSPM pixels when light is distributed among several photodetectors.

FDG-PET Intra-tratamiento como valor pronóstico en el tratamiento del linfoma Hodgkin

Introducción: La utilización de regímenes de tratamiento más individualizados requiere de mejores sistemas de estratificación temprana en Linfoma Hodgkin (LH). El estudio Tomografía por Emisión de Positrones utilizando 2-[18F] fluoro-2-deoxi-Dglucosa (FDG-PET) intra-tratamiento podría jugar un rol muy importante en esta evaluación. Objetivo: Determinar el valor pronóstico del FDG-PET intra-tratamiento en pacientes con LH para predecir sobrevida libre de progresión y sobrevida global. Material y método: El estudio fue llevado a cabo en el Servicio de Hematología del Hospital Central de Mendoza incluyendo pacientes con diagnóstico de LH confirmados por histología. De acuerdo al estadio y sitio de presentación, los pacientes recibieron quimioterapia sola o la combinación de radioterapia y quimioterapia, con el uso del esquema ABVD (adriamicina, bleomicina, vinblastina y dacarbazina) como protocolo estándar. Los estudios FDG-PET fueron practicados como parte de la evaluación intra-tratamiento y a la finalización. Resultados: En total fueron evaluados 8 pacientes, Sexo: F/M: 4/4, Edad: 18-58 años (Mediana: 29 años), Estadios: IIB:1, IIIA:2, IIIB:1, IVA:1, IVB:3, regiones nodales: 2-10 (Mediana:4), compromiso extranodal: 4/8, síntomas B: 5/8, enfermedad bulky 2/8 . Subtipos: Escleronodular: 6/8, Celularidad mixta: 1/8, Depleción linfocítica: 1/8. IPS: 1: 3/8 2: 3/8 3: 1/8 4: 0/8 ≥ 5: 1/8. Tratamientos: ABVD x 6: 6/8, ABVD x 6 + Radioterapia: 2/8. PET intermedio: 8/8 negativos (6/8 PET 3, 2/8 PET 2). PET final: 7/8 PET negativo, 1/8 PET positivo. Recaída: 1/8 (10° mes). Seguimiento: 11-37 meses (mediana de 24 meses). Discusión y Conclusiones: Al momento actual el FDG-PET intra-tratamiento demostró tener un importante valor predictivo negativo dado que todos los pacientes, menos uno, se encuentran en remisión completa sin progresión de enfermedad. Resta aún determinar el rol que esta herramienta pueda tener en el futuro en la terapia adaptada al riesgo de pacientes con LH.

Effect of fibers and whole grain content on quality attributes

Incorporation of fiber in cereals may lead to quality issues, thus decreasing consumer acceptance. This is partially due to deterioration of the microstructure, one of the primary quality attributes of cereals. The objective of this study was to better understand the mechanisms by which dietary fibers affect the quality of cereal products during extrusioncooking. The study quantified the effect of amount and type of fiber and whole grain on (i) texture, (ii) structure, and (iii) rehydration properties of extruded cereals. New innovative methods were applied and combined with traditional techniques to characterize both the structure and the rehydration properties. Extruded cereals were produced using a starch-based recipe (whole and wheat flours) and two sources of fibers (oat bran concentrate and wheat bran). The oat and wheat bran levels used in this study were 0, 10, and 20%. The different mixtures were extruded in a pilot twinscrew extruder BC21 (Clextral) and then sugar coated after drying. Mechanical properties of extruded cereals were investigated by compression test. The cellular structure was observed by X-ray tomography. The quality of coating (thickness, homogeneity) was analyzed by optical coherence tomography. The rehydration properties of such cereals in milk were evaluated by magnetic resonance imaging and optical coherence tomography. This work revealed that structure assessment of extruded cereals may lead to a better understanding of the effect of fiber addition on texture and rehydration properties. The application of innovative methods, such as optical coherence tomography and magnetic resonance imaging, was found to be useful to quantify the structural properties.

Evaluation of APD and SiPM Matrices as Sensors for Monolithic PET Detector Block

Gamma detectors based on monolithic scintillator blocks coupled to APDs matrices have proved to be a good alternative to pixelated ones for PET scanners. They provide comparable spatial resolution, improve the sensitivity and make easier the mechanical design of the system. In this study we evaluate by means of Geant4-based simulations the possibility of replacing the APDs by SiPMs. Several commercial matrices of light sensors coupled to LYSO:Ce monolithic blocks have been simulated and compared. Regarding the spatial resolution and linearity of the detector, SiPMs with high photo detection efficiency could become an advantageous replacement for the APDs

Evaluation of a PET Prototype Using LYSO:Ce Monolithic Detector Block

We have analyzed the performance of a PET demonstrator formed by two sectors of four monolithic detector blocks placed face-to-face. Both front-end and read-out electronics have been evaluated by means of coincidence measurements using a rotating 22Na source placed at the center of the sectors in order to emulate the behavior of a complete full ring. A continuous training method based on neural network (NN) algorithms has been carried out to determine the entrance points over the surface of the detectors. Reconstructed images from 1 MBq 22Na point source and 22Na Derenzo phantom have been obtained using both filtered back projection (FBP) analytic methods and the OSEM 3D iterative algorithm available in the STIR software package [1]. Preliminary data on image reconstruction from a 22Na point source with Ø = 0.25 mm show spatial resolutions from 1.7 to 2.1 mm FWHM in the transverse plane. The results confirm the viability of this design for the development of a full-ring brain PET scanner compatible with magnetic resonance imaging for human studies.

Characterization and Test of a Data Acquisition System for PET

A small Positron Emission Tomography demonstrator based on LYSO slabs and Silicon Photomultiplier matrices is under construction at the University and INFN of Pisa. In this paper we present the characterization results of the read-out electronics and of the detection system. Two SiPM matrices, composed by 8 × 8 SiPM pixels, 1.5 mm pitch, have been coupled one to one to a LYSO crystals array. Custom Front-End ASICs were used to read the 64 channels of each matrix. Data from each Front-End were multiplexed and sent to a DAQ board for the digital conversion; a motherboard collects the data and communicates with a host computer through a USB port. Specific tests were carried out on the system in order to assess its performance. Futhermore we have measured some of the most important parameters of the system for PET application.

Projector Model for Efficient List-Mode Reconstruction in PET Scanners with Parallel Planar Detectors

We have developed a new projector model specifically tailored for fast list-mode tomographic reconstructions in Positron emission tomography (PET) scanners with parallel planar detectors. The model provides an accurate estimation of the probability distribution of coincidence events defined by pairs of scintillating crystals. This distribution is parameterized with 2D elliptical Gaussian functions defined in planes perpendicular to the main axis of the tube of response (TOR). The parameters of these Gaussian functions have been obtained by fitting Monte Carlo simulations that include positron range, acolinearity of gamma rays, as well as detector attenuation and scatter effects. The proposed model has been applied efficiently to list-mode reconstruction algorithms. Evaluation with Monte Carlo simulations over a rotating high resolution PET scanner indicates that this model allows to obtain better recovery to noise ratio in OSEM (ordered-subsets, expectation-maximization) reconstruction, if compared to list-mode reconstruction with symmetric circular Gaussian TOR model, and histogram-based OSEM with precalculated system matrix using Monte Carlo simulated models and symmetries.

Silicon Photomultipliers (SiPM) as novel photodetectors for PET

Next generation PET scanners should fulfill very high requirements in terms of spatial, energy and timing resolution. Modern scanner performances are inherently limited by the use of standard photomultiplier tubes. The use of Silicon Photomultipliers (SiPMs) is proposed for the construction of a 4D-PET module of 4.8×4.8 cm2 aimed to replace the standard PMT based PET block detector. The module will be based on a LYSO continuous crystal read on two faces by Silicon Photomultipliers. A high granularity detection surface made by SiPM matrices of 1.5 mm pitch will be used for the x–y photon hit position determination with submillimetric accuracy, while a low granularity surface constituted by 16 mm2 SiPM pixels will provide the fast timing information (t) that will be used to implement the Time of Flight technique (TOF). The spatial information collected by the two detector layers will be combined in order to measure the Depth of Interaction (DOI) of each event (z). The use of large area multi-pixel Silicon Photomultiplier (SiPM) detectors requires the development of a multichannel Data Acquisition system (DAQ) as well as of a dedicated front-end in order not to degrade the intrinsic detector capabilities and to manage many channels. The paper describes the progress made on the development of the proof of principle module under construction at the University of Pisa.

Correlation Between Processing Conditions, Microstructure and Mechanical Behavior in Regenerated Silkworm Silk Fibers

Regenerated silkworm fibers spun through a wet-spinning process followed by an immersion postspinning drawing step show a work to fracture comparable with that of natural silkworm silk fibers in a wide range of spinning conditions. The mechanical behavior and microstructure of these high performance fibers have been characterized, and compared with those fibers produced through conventional spinning conditions. The comparison reveals that both sets of fibers share a common semicrystalline microstructure, but significant differences are apparent in the amorphous region. Besides, high performance fibers show a ground state and the possibility of tuning their tensile behavior. These properties are characteristic of spider silk and not of natural silkworm silk, despite both regenerated and natural silkworm silk share a common composition different from that of spider silk.