scholarly journals Reducing Calibration Time in PET Systems Based on Monolithic Crystals

2021 ◽  
Vol 8 ◽  
Author(s):  
Marta Freire ◽  
Gabriel Cañizares ◽  
Sara Echegoyen ◽  
Andrea Gonzalez-Montoro ◽  
Antonio J. Gonzalez
Keyword(s):  
High Performance ◽  
Gamma Ray ◽  
Simulated Data ◽  
Calibration Procedure ◽  
Packing Fraction ◽  
System Sensitivity ◽  
Standard Calibration ◽  
Pet System ◽  
Gamma Ray Detector ◽  
Calibration Time

In the past years, the gamma-ray detector designs based on the monolithic crystals have demonstrated to be excellent candidates for the design of high-performance PET systems. The monolithic crystals allow to achieve the intrinsic detector resolutions well below state-of-the-art; to increase packing fraction thus, increasing the system sensitivity; and to improve lesion detectability at the edges of the scanner field of view (FOV) because of their intrinsic depth of interaction (DOI) capabilities. The bottleneck to translate to the clinical PET systems based on a large number of monolithic detectors is eventually the requirement of mechanically complex and time-consuming calibration processes. To mitigate this drawback, several methods have been already proposed, such as using non-physically collimated radioactive sources or implementing the neuronal networks (NN) algorithms trained with simulated data. In this work, we aimed to simplify and fasten a calibration process of the monolithic based systems. The Normal procedure consists of individually acquiring a 11 × 11 22Na source array for all the detectors composing the PET system and obtaining the calibration map for each module using a method based on the Voronoi diagrams. Two reducing time methodologies are presented: (i) TEST1, where the calibration map of one detector is estimated and shared among all others, and (ii) TEST2, where the calibration map is slightly modified for each module as a function of their detector uniformity map. The experimental data from a dedicated prostate PET system was used to compare the standard calibration procedure with both the proposed methods. A greater similarity was exhibited between the TEST2 methodology and the Normal procedure; obtaining spatial resolution variances within 0.1 mm error bars and count rate deviations as small as 0.2%. Moreover, the negligible reconstructed image differences (13% deviation at most in the contrast-to-noise ratio) and almost identical contrast values were reported. Therefore, this proposed method allows us to calibrate the PET systems based on the monolithic crystals reducing the calibration time by approximately 80% compared with the Normal procedure.

Bayesian deconvolution of gamma‐ray logs

Geophysics ◽  
1987 ◽  
Vol 52 (11) ◽  
pp. 1535-1546 ◽  
Author(s):  
Ping Sheng ◽  
Benjamin White ◽  
Balan Nair ◽  
Sandra Kerford
Keyword(s):  
High Frequency ◽  
Gamma Ray ◽  
Simulated Data ◽  
Field Measurements ◽  
Bayesian Optimization ◽  
Frequency Noise ◽  
High Frequency Noise ◽  
Data Application ◽  
Gamma Ray Detector ◽  
Gamma Ray Log

The spatial resolution of gamma‐ray logs is defined by the length 𝓁 of the gamma‐ray detector. To resolve thin beds whose thickness is less than 𝓁, it is generally desirable to deconvolve the data to reduce the averaging effect of the detector. However, inherent in the deconvolution operation is an amplification of high‐frequency noise, which can be a detriment to the intended goal of increased resolution. We propose a Bayesian statistical approach to gamma‐ray log deconvolution which is based on optimization of a probability function which takes into account the statistics of gamma‐ray log measurements as well as the empirical information derived from the data. Application of this method to simulated data and to field measurements shows that it is effective in suppressing high‐frequency noise encountered in the deconvolution of gamma‐ray logs. In particular, a comparison with the least‐squares deconvolution approach indicates that the incorporation of physical and statistical information in the Bayesian optimization process results in optimal filtering of the deconvolved results.

F-18-FDG Positron Imaging in Oncological Patients: Gamma Camera Coincidence Detection versus Dedicated PET

1999 ◽  
Vol 38 (04) ◽  
pp. 108-114 ◽  
Author(s):  
H.-J. Kaiser ◽  
U. Cremerius ◽  
O. Sabri ◽  
M. Schreckenberger ◽  
P. Reinartz ◽  
...  
Keyword(s):  
Attenuation Correction ◽  
Spatial Resolution ◽  
Gamma Camera ◽  
Lesion Detection ◽  
Coincidence Detection ◽  
System Sensitivity ◽  
Oncological Patients ◽  
Phantom Studies ◽  
Pet System ◽  
Dedicated Pet

Summary Aim of the present study was to investigate the feasibility of 2-[fluorine-18]-fluoro-2-deoxy-D-glucose (FDG) imaging in oncological patients with a dual head gamma camera modified for coincidence detection (MCD). Methods: Phantom studies were done to determine lesion detection at various lesion-to-background ratios, system sensitivity and spatial resolution. Thirty-two patients with suspected or known malignant disease were first studied with a dedicated full-ring PET system (DPET) applying measured attenuation correction and subsequently with an MCD system without attenuation correction. MCD images were first interpreted without knowledge of the DPET findings. In a second reading, MCD and DPET were evaluated simultaneously. Results: The phantom studies revealed a comparable spatial resolution for DPET and MCD (5.9 × 6.3 × 4.2 mm vs. 5.9 × 6.5 × 6.0 mm). System sensitivity of MCD was less compared to DPET (91 cps/Bq/ml/cmF0V vs. 231 cps/ Bq/ml/cmFOv). At a lesion-to-background ratio of 4:1, DPET depicted a minimal phantom lesion of 1.0 cm in diameter, MCD a minimal lesion of 1.6 cm. With DPET, a total of 91 lesions in 27 patients were classified as malignant. MCD without knowledge of DPET results revealed increased FDG uptake in all patients with positive DPET findings. MCD detected 72 out of 91 DPET lesions (79.1 %). With knowledge of the DPET findings, 11 additional lesions were detected (+12%). MCD missed lesions in six patients with relevance for staging in two patients. All lesions with a diameter above 18 mm were detected. Conclusion: MCD FDG imaging yielded results comparable to dedicated PET in most patients. However, a considerable number of small lesions clearly detectable with DPET were not detected by MCD alone. Therefore, MCD cannot yet replace dedicated PET in all oncological FDG studies. Further technical refinement of this new method is needed to improve image quality (e.g. attenuation correction).

scholarly journals The STACEE ground-based gamma-ray detector

2005 ◽  
Author(s):  
D.M. Gingrich ◽  
L.M. Boone ◽  
D. Bramel ◽  
J. Carson ◽  
C.E. Covault ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Gamma Ray Detector

scholarly journals Constructing Large-Scale Genetic Maps Using an Evolutionary Strategy Algorithm

Genetics ◽  
2003 ◽  
Vol 165 (4) ◽  
pp. 2269-2282
Author(s):  
D Mester ◽  
Y Ronin ◽  
D Minkov ◽  
E Nevo ◽  
A Korol
Keyword(s):  
Discrete Optimization ◽  
High Performance ◽  
Large Scale ◽  
Simulated Data ◽  
Real Data ◽  
Genetic Maps ◽  
Chromosome 1 ◽  
Evolutionary Strategy ◽  
Group A ◽  
The One

Abstract This article is devoted to the problem of ordering in linkage groups with many dozens or even hundreds of markers. The ordering problem belongs to the field of discrete optimization on a set of all possible orders, amounting to n!/2 for n loci; hence it is considered an NP-hard problem. Several authors attempted to employ the methods developed in the well-known traveling salesman problem (TSP) for multilocus ordering, using the assumption that for a set of linked loci the true order will be the one that minimizes the total length of the linkage group. A novel, fast, and reliable algorithm developed for the TSP and based on evolution-strategy discrete optimization was applied in this study for multilocus ordering on the basis of pairwise recombination frequencies. The quality of derived maps under various complications (dominant vs. codominant markers, marker misclassification, negative and positive interference, and missing data) was analyzed using simulated data with ∼50-400 markers. High performance of the employed algorithm allows systematic treatment of the problem of verification of the obtained multilocus orders on the basis of computing-intensive bootstrap and/or jackknife approaches for detecting and removing questionable marker scores, thereby stabilizing the resulting maps. Parallel calculation technology can easily be adopted for further acceleration of the proposed algorithm. Real data analysis (on maize chromosome 1 with 230 markers) is provided to illustrate the proposed methodology.

Application of the variable projection scheme for frequency-domain full-waveform inversion

Geophysics ◽  
2013 ◽  
Vol 78 (6) ◽  
pp. R249-R257 ◽  
Author(s):  
Maokun Li ◽  
James Rickett ◽  
Aria Abubakar
Keyword(s):  
Frequency Domain ◽  
Waveform Inversion ◽  
Simulated Data ◽  
Calibration Procedure ◽  
Full Waveform Inversion ◽  
Inversion Algorithm ◽  
Unknown Parameters ◽  
Variable Projection ◽  
Full Waveform ◽  
Data Calibration

We found a data calibration scheme for frequency-domain full-waveform inversion (FWI). The scheme is based on the variable projection technique. With this scheme, the FWI algorithm can incorporate the data calibration procedure into the inversion process without introducing additional unknown parameters. The calibration variable for each frequency is computed using a minimum norm solution between the measured and simulated data. This process is directly included in the data misfit cost function. Therefore, the inversion algorithm becomes source independent. Moreover, because all the data points are considered in the calibration process, this scheme increases the robustness of the algorithm. Numerical tests determined that the FWI algorithm can reconstruct velocity distributions accurately without the source waveform information.

scholarly journals Soft gamma-ray detector for the ASTRO-H Mission

2012 ◽  
Author(s):  
Shin Watanabe ◽  
Hiroyasu Tajima ◽  
Yasushi Fukazawa ◽  
Roger Blandford ◽  
Teruaki Enoto ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Gamma Ray Detector

High Performance Liquid Chromatography Determination of Fentin Acetate Residue in Beet and Soil

2012 ◽  
Vol 550-553 ◽  
pp. 1173-1176
Author(s):  
Hui Qing Sun ◽  
Yi Qiang Li ◽  
Guang Jun Xu ◽  
Xiao Zhen ◽  
Jin Li Xu ◽  
...  
Keyword(s):  
High Performance Liquid Chromatography ◽  
Liquid Chromatography ◽  
High Performance ◽  
Detectable Level ◽  
Relative Standard ◽  
External Standard ◽  
Detectable Concentration ◽  
Acid Aqueous Solution ◽  
Standard Calibration

Abstract. [Aims] A high performance liquid chromatography (HPLC) was presented for determination of fentin acetate residue in beet and soils. [Methods] Fentin acetate was extracted from beet plants and soils with hydrochloric acid and acetonitrile, followed by a second extraction in dichloromethane, purified by acid aluminium oxide with methanol eluting, then dissolved by concentration and dilution with acetoneitrile. A HPLC with UV detection at 220 nm and a Waters Sun FireTM-C18 column, which was eluted with methanol and 0.5% phosphoric acid aqueous solution and was used based on an external standard calibration curve. [Results] The results showed that the average recoveries were 88.4-95.6% for beet plants and 91.2-91.8% for soils. The relative standard deviations were 2.0-4.5% and 4.3-5.3% respectively. The minimum detectable level was 1.6×10-10g, the lowest detectable concentration was 0.02mg/kg. [Conclusions] The method is convenient and can meet the requirement of residual analysis and also provide reference for other crops.

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