184 research outputs found
A self-adjusting constant-current source follower for CMOS preamplifiers of semiconductor detector signals
No full textA class A-B CMOS output stage, conceived for low-noise integrated preamplifiers of X- and gamma-ray detector signals, is proposed. It is based on a negative-feedback loop which stabilizes the working current of the output transistor. As a result we obtained both a low output impedance and a large voltage swing. We realized the output stage in a 5V 0.8um CMOS technology. The obtained output voltage swing on a 100 ohm load resistor is -2.5V against a negative power supply of -3V. We inserted the output stage into a charge-sensitive preamplifier for germanium detectors to prove its functionality, obtaining the same large negative voltage swing and a signal rise time as fast as 12.8ns on a terminated 50-ohm cable (equivalent to a load resistor of 100 ohm), as well as a negligible additional noise. The detector capacitance for these measurements was 15pF
A configurable digital processor for scintillation detector events
No full textThe paper presents a digital configurable instrument for processing signals from scintillation detectors. We discuss design, realization and engineering of the system. The main feature of the architecture is the possibility to adapt to a wide range of different operative conditions by changing configuration of both the digital and the analog section. In particular digital configurable devices, i.e. digital signal processor (DSP) and field programmable gate array (FPGA), guarantee versatility, evolution prospects and easiness of customization of the system
Design criteria for the optimization of hybrid charge-sensitive preamplifiers for high resolution gamma-ray spectroscopy
No full textDesign criteria for the optimization of hybrid charge-sensitive preamplifiers for germanium high resolution gamma-ray detectors are presented. In particular we studied the optimization of the Transimpedance Amplifier (T.A.) following the input JFET and realized with Bipolar Junction Transistors. Our aim was to highlight and adjust the key parameters of the T.A. in order to maximize the loop gain of the charge-sensing stage while maintaining at the same time an adequate low noise. We analytically studied the expression of the open-loop gain, focusing our attention on the upper limit that can be reached according to the physical parameters of the chosen devices. We analyzed the role played by the Miller effect acting on the input JFET gate-drain capacitance, which reduces the loop gain of the charge-sensing stage, and we proposed a solution to address this issue. We studied the optimization of the folded cascode BJT bias current in order to minimize the T.A. noise. Analytical study is reported and simulation results for typical structures are shown
De-oscillating preamplifier signals through digital filtering techniques
No full textWe present a time-domain digital filtering technique able to eliminate the ringing of preamplifier signals. The preamplifier signal is sampled by an ADC and then processed by a digital filter, whose aim is to eliminate the ringing while minimizing the loss of high-frequency information. We developed such a filtering technique for the case of a charge-sensitive preamplifier for gamma-ray spectroscopy installed far away from the detector/FET cryogenic assembly. With such a setup a damped oscillation is caused by the long connection cable acting as a delay line along the feedback loop. We could completely eliminate the ringing in the output signals and maintain, at the same time, a large bandwidth and a high loop gain. Experimental results are shown
Simultaneous X-ray and gamma-ray observations of CYG X-1 in the hard state by GINGA and OSSE
No full textA fast VLSI preamplifier for segmented HPGe gamma-ray detectors
No full textWe developed and realized a fast integrated charge-sensitive preamplifier for segmented High Purity Germanium (HPGe) detectors, able to directly drive long 50-ohm coaxial cables. The circuit is realized in a 5V 0.8um CMOS technology. It includes an external input FET, mod. BF862, which can be easily replaced if necessary. The charge-to-voltage gain and the fall time are set by an external RC feedback network, and can be changed in a broad range of values. The preamplifier works both at room and at cryogenic temperatures. The area occupancy of the chip is (366 x 275)um^2 and the static power consumption is 8mW excluding the FET. The preamplifier is optimized for hole signals, i.e. negative output voltage swings. With a 100O-ohm output load it is able to provide an output swing of -2.4V, against a negative power supply of -3V. The transition time for such a large pulse is 12.8ns. The noise performance with a 15pF detector capacitance is 110 r.m.s. electrons both at 300K and at 77K, at a quasi-Gaussian shaping time of 10us. The obtained performance is adequate for gamma-ray spectroscopy and pulse-shape analysis with HPGe segmented detectors
Multiplexed Imaging Reveals the Spatial Relationship of the Extracellular Acidity-Targeting pHLIP with Necrosis, Hypoxia, and the Integrin-Targeting cRGD Peptide
No full textpH (low) insertion peptides (pHLIPs) have been developed for cancer imaging and therapy targeting the acidic extracellular microenvironment. However, the characteristics of intratumoral distribution (ITD) of pHLIPs are not yet fully understood. This study aimed to reveal the details of the ITD of pHLIPs and their spatial relationship with other tumor features of concern. The fluorescent dye-labeled pHLIPs were intravenously administered to subcutaneous xenograft mouse models of U87MG and IGR-OV1 expressing αVβ3 integrins (using large necrotic tumors). The αVβ3 integrin-targeting Cy5.5-RAFT-c(-RGDfK-)4 was used as a reference. In vivo and ex vivo fluorescence imaging, whole-tumor section imaging, fluorescence microscopy, and multiplexed fluorescence colocalization analysis were performed. The ITD of fluorescent dye-labeled pHLIPs was heterogeneous, having a high degree of colocalization with necrosis. A direct one-to-one comparison of highly magnified images revealed the cellular localization of pHLIP in pyknotic, karyorrhexis, and karyolytic necrotic cells. pHLIP and hypoxia were spatially contiguous but not overlapping cellularly. The hypoxic region was found between the ITDs of pHLIP and the cRGD peptide and the Ki-67 proliferative activity remained detectable in the pHLIP-accumulated regions. The results provide a better understanding of the characteristics of ITD of pHLIPs, leading to new insights into the theranostic applications of pHLIPs
External radiotherapy of thyroid cancer
No full textDifferentiated thyroid cancer comprises papillary, mixed papillary-follicular and follicular adenocarcinomas. They are mostly hormone-sensitive and respond to thyroid-stimulating hormone (TSH) suppression. The standard treatment is total thyroidectomy. I-131 therapy and thyroid hormone suppression therapy. Adjuvant external radiotherapy is discussed controversially Most authors recommend adjuvant external radiotherapy for extracapsular tumor extension. Decision on an individual basis should be made for patients with lymph node involvement. In the case of incomplete surgical resection, external radiotherapy should be applied if second surgery is not possible. For medullary thyroid cancer, external beam radiotherapy seems to be beneficial for patients with surgically inaccessible disease, with microscopic residual or gross tumor after surgery, with recurrent locoregional disease, or with surgically unmanageable metastases. Patients suffering from anaplastic thyroid cancer should receive combined treatment consisting of extensive surgery, external irradiation with total doses up to 60 Gy, and chemotherapy. The combined treatment modality leads to higher local control rates and prolongs survival
A charge sensitive preamplifier with an active ultra fast recovery circuit for experiments at neutron time-of-flight facilities
No full textIn Neutron time-of-flight facilities an intense flux of gamma-rays and high-energy particles commonly called gamma-flash is generated in the neutron production. Due to the high energy deposited, the gamma-flash often results in a saturated pulse, which may make the detectors blind for a long time and event produced by neutrons above few MeV cannot be detected. In order to decrease this effect we have developed a Charge sensitive preamplifier with an active circuit for an ultra fast de-saturation
Partial volume correction for image-generated arterial input functions
No full textWe propose a method for Partial Volume correction and intensity recovery that models blood vessels as small cylinders of known diameter. We use a Bayesian classifier that explicitly models the effects of the point spread function on these cylinders. Although the method requires prior knowledge of the cylinder/arterial width, there is no requirement for any registration. A further advantage is that Region Of Interest (ROI) definition can be limited to only a few axial slices, thus minimizing time averaging. Furthermore, ROI selection requires only approximate placement around the target artery, encompassing both artery and background tissue, so that recovered data values are not operator-dependent. We present results for classifier performance on simulated phantom data of hot cylindrical inserts in a warm background with different contrast to noise ratios. © 2006 IEEE
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