system sensitivity
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2022 ◽  
Vol 17 (01) ◽  
pp. P01006
Author(s):  
M. Saed ◽  
A. Sadremomtaz ◽  
H. Mahani

Abstract Background: the need for simultaneous high-sensitivity and high-resolution breast SPECT imaging mandates to design and optimize dedicated scanners. Therefore, this work aims to design and optimize a novel breast-dedicated SPECT system with multi-lofthole collimator. Materials and Methods: in this research, a novel breast-dedicated scanner is designed and then optimized. The scanner is equipped with a single full-ring multi-lofthole collimation long with modular NaI(Tl) detectors. The step-and-shoot data acquisition was considered with two steps. Then, an analytic optimization was conducted to balance the existing sensitivity-resolution tradeoff. To do so, several scanner geometries were investigated. The optimal configuration maximized the system sensitivity at a given system resolution. Furthermore, the scanner was also modeled within the GATE simulator. Then, detector energy resolution, septal penetration and scattering, and system sensitivity were calculated. Analytic findings were also compared with the simulated ones. Results: the results showed that high sensitivity of about 2 cps/kBq can be obtained for a diameter of lofthole 3.05 mm with a 75° opening angle. Results of GATE simulations showed clinically acceptable performance of the system offering 9% energy resolution for a point source. The septal penetration and scattering were approximately 0.5% and 0.2%, respectively, for cylindrical water phantom and tungsten as collimator material. Conclusion: the designed SPECT scanner provides promising results in terms of sensitivity and spatial resolution and therefore outperforms the traditional multi-pinhole collimation by a much higher sensitivity at a given system resolution.


Author(s):  
Karim Hussein ◽  
Dalia Shihab Ahmed

In this century, lung cancer is undoubtedly one of the major serious health problems, and one of the leading causes of death for women and men worldwide. Despite advances in treating lung cancer with unprecedented products of pharmaceutical and technological advances, mortality and morbidity rates remain a major challenge for oncologists and cancer biologists. Thus, there is an urgent need to provide early, accurate, and effective diagnostic techniques to improve the survival rate and reduce morbidity and mortality related to lung cancer patients. Therefore, in this paper, an effective lung cancer screening technique is proposed for the early detection of risk factors for lung cancer. In this proposed technique, the powerful acceleration feature Speeded up robust feature (SURF) was used to extract the features. One of the machine learning methods was used to detect cancer by relying on the k nearest neighbor (KNN ) method, where the experimental results show an effective way to discover SURF features and tumor detection by relying on neighborhoods and calculating the distance using KNN. As a result, a high system sensitivity performance success rate of 96% and a system accuracy of 99% has been achieved.


2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Lanting Wu ◽  
Jianping Sun ◽  
Yuqiang Tong

Deep excavation supported by vertical retaining walls together with strutting system is commonly used in Singapore for the construction of underground infrastructure. In this paper, a series of numerical scenarios simulated by PLAXIS software are carried out to study the influence of different design parameters such as pre-auger loosening effect, the embedded depth of retaining wall into the stiff soil layer, and the elastic modulus of the ground improvement layer on excavation design especially on strut force, retaining wall deflection, and bending moment. The results show that there is high risk if only a single set of parameters are used as input to predict the performance of the retaining system. Sensitivity analysis shall be carried out to evaluate the effects of these parameter variations within a reasonable range on strut force, retaining wall deflection, and bending moment.


2021 ◽  
Author(s):  
Peter O. Passenier

Abstract. In the field of climate-change research a lot of effort is devoted to the ‘narrowing down’ of uncertainties in the estimation of Equilibrium climate sensitivity (ECS), the global mean warming as a result of an instantaneous doubling of the CO2 concentration in the atmosphere. The present study explores possible consequences of this narrowing down of ECS for the long-term Earth system sensitivity (ESS), taking into account ‘slow’ feedbacks due to the cryosphere response (permafrost melting and ice-sheet disintegration) to a warming world. Implications for international policy making, aiming at avoiding 2 degrees Celsius of global warming, are briefly discussed.


2021 ◽  
Author(s):  
Fatme Hoteit ◽  
Debbie Erhmann Feldman ◽  
Lisa C. Carlesso

Purpose: To explore factors associated with intermittent, constant, and mixed pain in people with knee osteoarthritis. Method: We conducted a secondary analysis of a cross-sectional multicenter study with adults ≥ 40 years with knee osteoarthritis. Participants completed questionnaires on personal (e.g., demographics, comorbidities), physical (e.g., physical function), psychological (e.g., depressive symptoms), pain (e.g., qualities), and tests for physical performance and nervous system sensitivity. We qualified patients’ pain as intermittent, constant, or mixed using the Modified painDETECT Questionnaire and assessed associations with the variables using multinomial logistic regression. Results: The 279 participants had an average age of 63.8 years (SD = 9.6), BMI of 31.5 kg/m2 (SD = 8.7), and 58.6% were female. Older age (odds ratio [OR] 0.95; 95% CI: 0.90, 1.00) and higher self-reported physical function ([OR] 0.94; 95% CI: 0.91, 0.98) were associated with a lower likelihood of mixed pain compared with intermittent pain. Higher pain intensity ([OR] 1.25; 95% CI: 1.07, 1.47) was related to a 25% higher likelihood of mixed pain compared with intermittent pain. Conclusions: This study provides initial data for associations of personal, pain, and physical function factors with different pain patterns. Awareness of these factors can help clinicians develop targeted strategies for managing patients’ pain.


2021 ◽  
Vol 8 ◽  
Author(s):  
Marta Freire ◽  
Gabriel Cañizares ◽  
Sara Echegoyen ◽  
Andrea Gonzalez-Montoro ◽  
Antonio J. Gonzalez

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.


Author(s):  
Mara De Rosa ◽  
Davide Crepaldi

AbstractResearch on visual word identification has extensively investigated the role of morphemes, recurrent letter chunks that convey a fairly regular meaning (e.g., lead-er-ship). Masked priming studies highlighted morpheme identification in complex (e.g., sing-er) and pseudo-complex (corn-er) words, as well as in nonwords (e.g., basket-y). The present study investigated whether such sensitivity to morphemes could be rooted in the visual system sensitivity to statistics of letter (co)occurrence. To this aim, we assessed masked priming as induced by nonword primes obtained by combining a stem (e.g., bulb) with (i) naturally frequent, derivational suffixes (e.g., -ment), (ii) non-morphological, equally frequent word-endings (e.g., -idge), and (iii) non-morphological, infrequent word-endings (e.g., -kle). In two additional tasks, we collected interpretability and word-likeness measures for morphologically-structured nonwords, to assess whether priming is modulated by such factors. Results indicate that masked priming is not affected by either the frequency or the morphological status of word-endings, a pattern that was replicated in a second experiment including also lexical primes. Our findings are in line with models of early visual processing based on automatic stem/word extraction, and rule out letter chunk frequency as a main player in the early stages of visual word identification. Nonword interpretability and word-likeness do not affect this pattern.


Author(s):  
Vanessa Nadig ◽  
Ken Herrmann ◽  
Felix M. Mottaghy ◽  
Volkmar Schulz

AbstractPurpose Since the 1990s, PET has been successfully combined with MR or CT systems. In the past years, especially PET systems have seen a trend towards an enlarged axial field of view (FOV), up to a factor of ten. Methods Conducting a thorough literature research, we summarize the status quo of contemporary total-body (TB) PET/CT scanners and give an outlook on possible future developments. Results Currently, three human TB PET/CT systems have been developed: The PennPET Explorer, the uExplorer, and the Biograph Vision Quadra realize aFOVs between 1 and 2 m and show a tremendous increase in system sensitivity related to their longer gantries. Conclusion The increased system sensitivity paves the way for short-term, low-dose, and dynamic TB imaging as well as new examination methods in almost all areas of imaging.


2021 ◽  
Author(s):  
Farid Baskoro ◽  
Bambang Suprianto ◽  
Asri Bekti Pratiwi ◽  
Lilik Anifah ◽  
Aristyawan Putra Nurdiansyah ◽  
...  

Instruments ◽  
2021 ◽  
Vol 5 (3) ◽  
pp. 30
Author(s):  
Andrew M. Polemi ◽  
Annie K. Kogler ◽  
Patrice K. Rehm ◽  
Luke Lancaster ◽  
Heather R. Peppard ◽  
...  

We describe the design and performance of BRPET, a novel dedicated breast PET (dbPET) scanner designed to maximize visualization of posterior regions of the breast. BRPET uses prone imaging geometry and a 12-module detector ring built from pixelated LYSO crystals coupled to position sensitive photomultiplier tubes (PSPMTs). Optical coupling via slanted plastic fiber optic light guides permits partial insertion of the crystals into the exam table’s breast aperture. Image quality testing procedures were adapted from the NEMA NU4-2008 protocol. Two additional phantom tests quantified the posterior extent of the usable volume of view (VoV). BRPET axial, radial, and tangential FWHM spatial resolutions at the isocenter were 1.8, 1.7, and 1.9 mm, respectively. The peak absolute system sensitivity was 0.97% using an energy window of 460–562 keV. The peak noise equivalent counting rate was 5.33 kcps at 21.6 MBq. The scanner VoV extends to within ~6 mm of the plane defining the location of the chest wall. A pilot human study (n = 10) compared the diagnostic performance of FDG-BRPET to that of contrast enhanced MRI (CEMRI), with biopsy as ground truth. Averaged over three expert human observers, the sensitivity/specificity for BRPET was 0.93/1.0, compared to 1.0/0.25 for CEMRI.


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