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1
Hu, Hongchang. "QML Estimators in Linear Regression Models with Functional Coefficient Autoregressive Processes." Mathematical Problems in Engineering 2010 (2010): 1–30. http://dx.doi.org/10.1155/2010/956907.
Анотація:
This paper studies a linear regression model, whose errors are functional coefficient autoregressive processes. Firstly, the quasi-maximum likelihood (QML) estimators of some unknown parameters are given. Secondly, under general conditions, the asymptotic properties (existence, consistency, and asymptotic distributions) of the QML estimators are investigated. These results extend those of Maller (2003), White (1959), Brockwell and Davis (1987), and so on. Lastly, the validity and feasibility of the method are illuminated by a simulation example and a real example.
2
Francq, Christian, and Le Quyen Thieu. "QML INFERENCE FOR VOLATILITY MODELS WITH COVARIATES." Econometric Theory 35, no. 1 (February 1, 2018): 37–72. http://dx.doi.org/10.1017/s0266466617000512.
Анотація:
The asymptotic distribution of the Gaussian quasi-maximum likelihood estimator (QMLE) is obtained for a wide class of asymmetric GARCH models with exogenous covariates. The true value of the parameter is not restricted to belong to the interior of the parameter space, which allows us to derive tests for the significance of the parameters. In particular, the relevance of the exogenous variables can be assessed. The results are obtained without assuming that the innovations are independent, which allows conditioning on different information sets. Monte Carlo experiments and applications to financial series illustrate the asymptotic results. In particular, an empirical study demonstrates that the realized volatility can be a helpful covariate for predicting squared returns.
3
Meitz, Mika, and Pentti Saikkonen. "PARAMETER ESTIMATION IN NONLINEAR AR–GARCH MODELS." Econometric Theory 27, no. 6 (May 31, 2011): 1236–78. http://dx.doi.org/10.1017/s0266466611000041.
Анотація:
This paper develops an asymptotic estimation theory for nonlinear autoregressive models with conditionally heteroskedastic errors. We consider a general nonlinear autoregression of order p (AR(p)) with the conditional variance specified as a general nonlinear first-order generalized autoregressive conditional heteroskedasticity (GARCH(1,1)) model. We do not require the rescaled errors to be independent, but instead only to form a stationary and ergodic martingale difference sequence. Strong consistency and asymptotic normality of the global Gaussian quasi-maximum likelihood (QML) estimator are established under conditions comparable to those recently used in the corresponding linear case. To the best of our knowledge, this paper provides the first results on consistency and asymptotic normality of the QML estimator in nonlinear autoregressive models with GARCH errors.
4
Francq, Christian, and Jean-Michel Zakoïan. "QML ESTIMATION OF A CLASS OF MULTIVARIATE ASYMMETRIC GARCH MODELS." Econometric Theory 28, no. 1 (August 3, 2011): 179–206. http://dx.doi.org/10.1017/s0266466611000156.
Анотація:
We establish the strong consistency and asymptotic normality of the quasi-maximum likelihood estimator (QMLE) of the parameters of a class of multivariate asymmetric generalized autoregressive conditionally heteroskedastic processes, allowing for cross leverage effects. The conditions required to establish the asymptotic properties of the QMLE are mild and coincide with the minimal ones in the univariate case. In particular, no moment assumption is made on the observed process. Instead, we require strict stationarity, for which a necessary and sufficient condition is established. The asymptotic results are illustrated by Monte Carlo experiments, and an application to a bivariate exchange rates series is proposed.
5
Zhang, Mengqi, and Boping Tian. "Profile Maximum Likelihood Estimation of Single-Index Spatial Dynamic Panel Data Model." Mathematics 11, no. 13 (July 1, 2023): 2947. http://dx.doi.org/10.3390/math11132947.
Анотація:
In this paper, the spatial dynamic panel data (SDPD) model is extended to the single-index spatial dynamic panel data (Si-SDPD) model by introducing a nonlinear connection function to reflect the interaction between explanatory variables. The Si-SDPD model not only retains the advantages of the parametric SDPD model in dealing with spatial and temporal interaction effects and spatio-temporal dependencies, but also solves the limitations of the parametric SDPD model that may lead to missed bias. It reduces the data dimension of non-parametric models and enhances the practicability and explanatory power of parametric models. Since the parts of the model to be estimated contain unknown functions, we propose a new estimation method, a profile maximum likelihood (PML) method, to solve the problem of incidental parameters in the estimation. Under the assumption that the spatial coefficients are known, we preliminarily estimate the unknown function by carrying out local polynomial estimation, so as to transform the model into the parametric form for solving purposes. We then solve the dynamic panel parametric model via quasi-maximum likelihood (QML) estimation. We derive the asymptotic properties of profile maximum likelihood estimators (PMLEs) and find that, under certain regularity conditions, both parametric and non-parametric estimators are consistent. Monte Carlo results show that PMLEs have good finite sample performance.
6
Hussein Jasim, Ahmed, Haider Mehdi Moeen, and Ali Hussein Alwan. "Asymptomatic Thyroid dysfunction in patients of chronic renal failure." AL-QADISIYAH MEDICAL JOURNAL 11, no. 19 (July 25, 2017): 203–10. http://dx.doi.org/10.28922/qmj.2015.11.19.203-210.
Анотація:
Fifty patients with chronic renal insufficiency underwent clinical evaluation & studies of thyroid function the results were compared with age & sex-matched controls. (20%) of patients had biochemical hypothyroidism with low serum T3, T4, & high serum TSH. All the members of the control group were biochemically euthyroid. The mean values of serum T3, T4 were significantly lower & mean serum TSH was significantly higher as compared to controls. There was no correlation of thyroid functions with decrease in renal function. To conclude thyroid dysfunction occurs both clinically & biochemically in patients with chronic renal insufficiency.
7
A. Abbas, Yahya, Adnan H. Aubaid, and Bushra J. Hamad. "Determination of Hepatitis C Viral Load and Genotypes by Real-Time and RT-PCR at Thi_Qar Province." AL-QADISIYAH MEDICAL JOURNAL 9, no. 15 (August 2, 2017): 250–64. http://dx.doi.org/10.28922/qmj.2013.9.15.250-264.
Анотація:
The present study was carried out from Sept. 2010 to Jul. 2011 to detect the viral load and genotypes of HCV infections among asymptomatic peoples and patients referred to the central blood bank, center of thalassemia /AL-Haboby Hospital, renal dialysis unit/Al- Hussein Teaching Hospital and public health laboratory at Thi-Qar province.
Real-Time Polymerase Chain Reaction Technique (RT-qPCR) was implemented on 90 individuals of anti-HCV seropositive by ELISA III assay. The results revealed that 51(56.66%) were gave positive results for HCV. The RT-qPCR analyses of the positive samples were showed that the viral loads were ranged from 1.19 × 103 to 4.3 × 106 IU/ml of blood .The mean of viral load was 5.9 × 105 IU/ml of blood, whilst, the median was 2.6 × 105 IU/ml. Three genotypes of HCV were detected in patients serum by RT-PCR technique. Genotype 1a (33.33%), genotype 1b (37.25%) and genotype 4 (86.27%) with significant differences (p>0.05). Genotype 4 was the predominant and found in 44 of 51 cases, of those 21(41.18%) as single infections. Mixed infections with genotype 4 and each of 1a and 1b was found in 21.57% and 11.76% respectively. Mixed infections with genotype 4 and both 1a and 1b was found in 11.76%. Single infections with genotype 1b only was found in 13.73%, while genotype 1a was detected only in mixed infections. This study was the first at Thi-Qar province which involved the searching for HCV viral load and genotypes by using of Real-Time and RT-PCR technique.
8
B. Alawadi, Najlaa. "Interleukin-6 Level among Iraqi Patients with Chronic Lymphocytic Leukemia from Babil Province." AL-QADISIYAH MEDICAL JOURNAL 12, no. 21 (July 16, 2017): 113–23. http://dx.doi.org/10.28922/qmj.2016.12.21.113-123.
Анотація:
Introduction: Interleukin-6 (IL-6) is a pro-inflammatory cytokine and an anti-inflammatory myokine. Chronic lymphocytic leukemia (CLL) is the most common type of leukemia in adults. The exact role of IL-6 in CLL is still contraversial and needs alot of research.
Aim of the study: To measure serum level of interleukin-6 among Iraqi patients from Babil province with a newly diagnosed untreated chronic lymphocytic leukemia and to assess it's association with the stage of the disease and peripheral blood indices.
Materials and methods: This is a case-control study included 106 Iraqi patients with a newly diagnosed untreated chronic lymphocytic leukemia (CLL). They were from Babil province and attended the hospital during the period from 1st of November 2012 to 30th of October 2015, while the control group included 106 age and sex matched healthy individuals. CBC, blood film and serum IL-6 (Human IL-6 ELISA kit ) were done for both groups, and bone marrow exam was performed for the patients only.
Results: The age of the patients ranged from 44 to 82 years with mean age of 61.8 ±6.14 years. Male:Female ratio was 1.8:1 and 57.5% of them were asymptomatic. Serum IL-6 was undetected in 39.6% (42/106) of the control cases and in 13.2% (14/106) of the patients; all of them were in CLL stages 0 and 1. Mean serum IL-6 in the patient group was 12.6 ±5.1 pg/ml, while it was 6.2 ±2.3 pg/ml in the control group (P-value was 0.001). Higher levels were documented in stages 3 and 4 (P-value 0.0001).
Conclusion and recommendations: Elevated serum IL-6 was found among Iraqi patients with newly diagnosed untreated CLL, and higher levels were documented in advanced stage disease. Further studies are needed to assess exact role of IL-6 in CLL as it may have prognostic and/or therapeutic implications.
9
Asai, Manabu, and Michael McAleer. "Multivariate Hyper-Rotated GARCH-BEKK." Journal of Time Series Econometrics, January 10, 2022. http://dx.doi.org/10.1515/jtse-2021-0006.
Анотація:
Abstract For large multivariate models of generalized autoregressive conditional heteroskedasticity (GARCH), it is important to reduce the number of parameters to cope with the ‘curse of dimensionality’. Recently, Laurent, Rombouts and Violante (2014 “Multivariate Rotated ARCH Models” Journal of Econometrics 179: 16–30) developed the rotated multivariate GARCH model, which focuses on the parameters for standardized variables. This paper extends the rotated multivariate GARCH model by considering a hyper-rotation, which uses a more flexible structure for the rotation matrix. The paper shows an alternative representation based on a random coefficient vector autoregressive and moving-average (VARMA) process, and provides the regularity conditions for the consistency and asymptotic normality of the quasi-maximum likelihood (QML) estimator for VARMA with hyper-rotated multivariate GARCH. The paper investigates the finite sample properties of the QML estimator for the new model. Empirical results for four exchange rate returns show the new specifications works satisfactory for reducing the number of parameters.
10
Hu, Jianhua, Hao Ding, and Xiaoqian Liu. "Arbitrage Pricing with Heterogeneous Spatial Effects and Heteroscedastic Disturbances." Journal of Financial Econometrics, February 17, 2022. http://dx.doi.org/10.1093/jjfinec/nbab032.
Анотація:
Abstract We develop a heterogeneous spatial arbit and regression coefficients, and heteroscedastic variances, and further establish identification of parameters and asymptotic normality of the conditional QML estimators under some mild conditions. We apply the proposed model to study a real data set of 11 eurozone stock index returns and extend the Fama–French five-factor model to regional stock indices, in which heterogeneous spatial effects and heteroscedastic disturbances are highly significant and they both play very important roles in explaining distinct endogenous effects and distinct risks of the 11 eurozone stock markets. Our empirical results reveal unique characteristics of each of 11 eurozone stock markets and their inner connections.
11
Slimani, Walid, Ines Lescheb, and Mouloud Cherfaoui. "QMLE for periodic absolute value GARCH models." Random Operators and Stochastic Equations, February 1, 2024. http://dx.doi.org/10.1515/rose-2023-2027.
Анотація:
Abstract Periodic generalized autoregressive conditionally heteroscedastic (PGARCH) models were introduced by Bollerslev and Ghysels [T. Bollerslev and E. Ghysels, Periodic autoregressive conditional heteroscedasticity, J. Bus. Econom. Statist. 14 1996, 2, 139–151]; these models have gained considerable interest and continued to attract the attention of researchers. This paper is devoted to extensions of the standard absolute value GARCH (AVGARCH) model to the periodically time-varying coefficients (PAVGARCH) one. In this class of models, the parameters are allowed to switch between different regimes. Moreover, these models allow to integrate asymmetric effects in the volatility, Firstly, we give necessary and sufficient conditions ensuring the existence of stationary solutions (in the periodic sense). Secondary, a quasi-maximum likelihood (QML) estimation approach for estimating the PAVGARCH model is developed. The strong consistency and the asymptotic normality of the estimator are studied given mild regularity conditions, requiring strict stationarity and the finiteness of moments of some order for the errors term. Next, we present a set of numerical experiments illustrating the practical relevance of our theoretical results. Finally, we apply our model to two foreign exchange rates: of Algerian Dinar to the European currency Euro (Euro/Dinar) and the American currency Dollar (Dollar/Dinar). This empirical work shows that our approach also outperforms and fits the data well.
12
Alattar, Rand A., Shahd H. Shaar, Muftah Othman, Sulieman H. Abu Jarir, Samar M. Hashim, Fatima Iqbal, Fatima Rustom, Muna A. Almaslamani, and Ali S. Omrani. "Coronavirus disease 2019 in solid organ transplant recipients in the setting of proactive screening and contact tracing of Qatar." Qatar Medical Journal 2021, no. 2 (September 16, 2021). http://dx.doi.org/10.5339/qmj.2021.23.
Анотація:
Background: Clinical data on Coronavirus Disease 2019 (COVID-19) in solid organ transplant (SOT) recipients are limited. We herein report the initial clinical experience with COVID-19 in SOT recipients in Qatar. Methods: All SOT recipients with laboratory-confirmed COVID-19 up to May 23, 2020 were included. Demographic and clinical data were extracted retrospectively from the hospital’s electronic health records. Categorical data are presented as frequency and percentages, while continuous variables are summarized as medians and ranges. Results: Twenty-four SOT recipients with COVID-19 were identified (kidney 16, liver 6, heart 1, and liver and kidney 1). Organ transplantation preceded COVID-19 by a median of 60 months (range 1.7–184). The median age was 57 years (range 24–72), and 9 (37.5%) transplant recipients were females. Five (21%) asymptomatic patients were diagnosed through proactive screening. For the rest, fever (15/19) and cough (13/19) were the most frequent presenting symptoms. Five (20.8%) patients required invasive mechanical ventilation in the intensive care unit (ICU). Eleven (46%) patients developed acute kidney injury, including three in association with drug-drug interactions involving investigational COVID-19 therapies. Maintenance immunosuppressive therapy was modified in 18 (75%) patients, but systemic corticosteroids were not discontinued in any. After a median follow-up of 226 days (26–272), 20 (83.3%) patients had been discharged home, 2 (8.3%) were still hospitalized, 1 (4.2%) was still in the ICU, and 1 (4.2%) had died. Conclusions: Our results suggest that asymptomatic COVID-19 is possible in SOT recipients and that overall outcomes are not uniformly worse than those in the general population. The results require confirmation in large, international cohorts.
13
Dhillon, Navjot Kaur, Rajat Rana, sucheta Duhan, Sakshi Gautam, and Rajeev K. Puri. "Probing onset of nuclear vaporization in heavy ion collisions." Journal of Physics G: Nuclear and Particle Physics, March 27, 2023. http://dx.doi.org/10.1088/1361-6471/acc7bc.
Анотація:
Abstract The onset of nuclear vaporization in heavy-ion collisions is examined in the present study. For this, we perform Quantum Molecular Dynamics (QMD) model calculations supplemented with clusterisation algorithm for fragment identification, namely Simulated Annealing Clusterization Algorithm (SACA) approach. Our results with much sophisticated SACA method show a nice agreement with experimental findings of vaporization (predicted by asymptotic behaviour of average fragment charge) in $^{16}$\textrm{O} $+$ $^{80}$\textrm{Br} and $^{16}$\textrm{O} $+$ $^{10
7}$\textrm{Ag} collisions. Further, we predicted the energy of onset of vaporization for $^{40}$\textrm{Ca} $+$ $^{40}$\textrm{Ca}, $^{84}$\textrm{Kr} $+$ $^{84}$\textrm{Kr}, $^{132}$\textrm{Xe} $+$ $^{132}$\textrm{Xe} and $^{197}$\textrm{Au} $+$ $^{197}$\textrm{Au} collisions by investigating gas/liquid content and probability of vaporization (and it's derivative) \emph{vs} incident energy behaviour. These two observables probe the critical point of nuclear vaporization in much sophisticated manner, relative to average fragment charge. Our findings on these two novel variables to predict the energy of onset of vaporization are verifiable in experiments. The influence of colliding geometry as well as role of the Coulomb interactions is also studied to understand the system size effects on the nuclear vaporization.
14
Iqbal, Yousaf, Majid Alabdulla, Javed Latoo, Rajeev Kumar, Sultan Albrahim, Ovais Wadoo, and Peter M Haddad. "Mania and hypomania associated with COVID-19: a series of 15 cases seen by the consultation-liaison psychiatry service in Qatar." Qatar Medical Journal 2021, no. 3 (December 13, 2021). http://dx.doi.org/10.5339/qmj.2021.65.
Анотація:
Background: A range of neuropsychiatric diagnoses have been reported in association with coronavirus disease 2019 (COVID-19). However, only sporadic cases of mania or hypomania have been reported in patients with COVID-19. This study aimed to report clinical characteristics of 15 consecutive cases of COVID-19-associated mania or hypomania seen in three general hospitals in Qatar in the early months of the pandemic in 2020. Methods: This study is a retrospective case-note review of 15 cases of COVID-19-associated mania or hypomania (confirmed by polymerase chain reaction test), seen as inpatient consultations out of the first 100 consecutive patients managed by consultation-liaison psychiatric teams in Qatar between 2 March 2020 and 7 July 2020. Results: The mean age of the 15 patients was 40 years. Twelve patients had mania, and three had hypomania. Regarding the physical severity of COVID-19, 10 patients were asymptomatic, two had upper respiratory tract symptoms alone and three had pneumonia. None of the patients were intubated. Potential risk factors for mania/hypomania included pandemic-related psychosocial stress before admission (n = 9), past history of mania/bipolar disorder (n = 6) or psychosis (n = 2), raised inflammatory markers (n = 7) and steroid use (n = 3). None had a history of recent substance misuse. Other than one patient with advanced cancer, none had comorbidity regarded as likely to have caused mania or hypomania. Three patients had mild white matter ischaemic changes on brain imaging. Standard pharmacological treatment for mania (i.e. antipsychotic medication supplemented by prn benzodiazepines) was effective. Ten patients were discharged home from the COVID-19 facility where they presented, but five required transfer to Qatar's psychiatric hospital for further treatment of mania. Conclusion: The association of mania or hypomania with COVID-19 may be spurious (e.g. representing an initial presentation of bipolar disorder) or causal. The reported cases illustrate a range of potential aetiological mechanisms by which COVID-19 could cause mania or hypomania. Cohort studies are necessary to determine the incidence, aetiology and prognosis of COVID-19-associated mania/hypomania.
15
Lun, Xuekun, Pinghua Zhang, Yanjun Zhang, Pan Su, and Bojun Ma. "First Report of Leaf Blight Caused by Botryosphaeria dothidea on Aucuba japonica in Zhejiang Province, China." Plant Disease, April 28, 2024. http://dx.doi.org/10.1094/pdis-11-23-2400-pdn.
Анотація:
Aucuba japonica var. variegata Dombrain is a common evergreen cultivated ornamental in China (Li et al. 2016). In December 2022, severe leaf blight on A. japonica was observed next to the Meishiyuan of Zhejiang Normal University (29°8′4″N, 119°37′54″E) in Jinhua City, Zhejiang Province, China. There were seven plants in the surveyed area, and over 50% of leaves were affected. The early symptoms were small gray spot parts with brown borders on the tip of the leaves. Then the grey parts gradually expanded and became brownish black. In severe cases, the whole leaves became black and blighted. To identify the pathogen, 5 symptomatic leaves were randomly collected from 5 plants and cut into small pieces (5 mm × 5 mm), surface disinfected in 1% sodium hypochlorite solution for 3 min, followed by 75% alcohol for 30 s, then rinsed in sterile distilled water thrice. Tissues were cultured on potato dextrose agar (PDA) and incubated at 28°C for 7 days. Pure cultures were obtained by the single-spore method. Thirteen strains were isolates from the tissues, and nine of them showed similar morphological characteristics. Colonies were white initially, then became gray. The undersides of the colonies became black gradually. Hyaline, fusiform conidia (n = 30) were 17.1 to 24.76 µm (average 20.39 ± 1.906 µm) in length and 5.4 to 6.61 µm (average 6.19 ± 0.434 µm) in width. The DNA of nine isolates were extracted by Ezup Column Bacteria Genomic DNA Purification Kit, and their sequences were identical, so they were named QM1. The internal transcribed spacer (ITS) region, translation elongation factor 1-α (TEF1), and β-tubulin (TUB2) genes were amplified with primer pairs ITS1/ITS4, TEF1-728F/TEF1-986R and βt2a/βt2b (Slippers et al. 2004), respectively. The BLAST analysis indicated that ITS (OR215464), TEF1 (OR243689), and TUB2 (OR243688) of the isolate QM1 were 99 to 100% identical to those of Botryosphaeria dothidea (GenBank accession nos. MH329646 for ITS sequences; OL891702 for TEF1 sequences; MK511445 for TUB2 sequences). In addition, the phylogenetic tree based on sequences from ITS, TEF1 and TUB2 was constructed with MEGA 11 by use of the maximum likelihood method with 1,000 bootstrapping iterations. Based on the multi-locus phylogeny and morphological features, the isolate QM1 was identified as B. dothidea. To test the Koch’s postulates, ten leaves from three healthy two- to three-year-old A. japonica plants were surface disinfested with 75% ethanol for 30 s, rinsed with ddH2O three times. The leaves were wounded with a sterile needle and inoculated with 2ml drop of the isolate QM1 conidial suspension (106 spores/mL), with sterile distilled water as a control. All plants were placed in a greenhouse at 28°C, >70% relative humidity and 12 h light/day. The experiment was repeated three times. After 7 days, leaves of the inoculated group showed symptoms similar to those observed on the naturally infected leaves, while leaves of the control group remained asymptomatic. The pathogen was reisolated from inoculated leaves and was confirmed as B. dothidea based on morphological and molecular analyses. It has been reported B. dothidea cause leaf disease in a wide range of hosts in China, such as Camellia oleifera (Hao et al. 2023), Kadsura coccinea (Su et al. 2021). To our knowledge, this is the first report of Botryosphaeria dothidea causing leaf blight on Aucuba japonica in Zhejiang Province of China. B. dothidea are usually secondary invaders and are known to cause diseases in stressed plants. The results further expand the host-range of B. dothidea, and would help to establish control strategy against the disease.
16
Ali, Tamer A., Abdelwahed Samir Abougazia, Ahmed Sameer Alnuaimi, and Mona A. M. Mohammed. "Prevalence and risk factors of gallbladder polyps in primary health care centers among patients examined by abdominal ultrasonography in Qatar: a case–control study." Qatar Medical Journal 2021, no. 3 (December 13, 2021). http://dx.doi.org/10.5339/qmj.2021.48.
Анотація:
Background: Gallbladder (GB) polyps are raised lesions from the GB wall and projected into its lumen. The prevalence of GB polyps ranged between 4.3% and 12.3%. The clinical presentation of GB polypoid lesions vary, can be nonspecific and vague, and may be asymptomatic. Identifying malignant and premalignant polyps is important to provide treatment early and prevent cancer spread or development of malignancy. Ultrasonography (US) is the first imaging modality widely used in abdominal imaging. It is a noninvasive, rapid, painless, and safe imaging technique, with no radiation; thus, it is considered the best available examination with good sensitivity and specificity for GB polyps. Aim of the work: This study aimed to determine the relative frequency of the GB polyps and its risk factors among patients who underwent abdominal US in Primary Health Care Corporation, Qatar. Materials and methods: This was quantitative multicenter observational case–control study nested in a cross-sectional design. For the cross-sectional top-level study, the first step was to assess available abdominal ultrasound studies for the presence of GB polyps and stones. The second step was to perform a case–control study with three groups (a case group and two control groups; first, participants without GB stones and GB polyps; second, patients with GB stones but without GB polyps). Results: The study evaluated the GB images of 7156 individuals. The overall prevalence of GB polyps was 7.4% in the study population. Specifically, the overall prevalence of solitary GB polyp was 4.2% and that of multiple GB polyps was 3.2%. Regarding the size distribution of GB polyps in positive cases, 89.4% were < 6 mm, 9.3% were 69 mm, and 1.3% were ≥ 10 mm. Prevalence rate of selected comorbidities were as follows: liver disease, 1.8%; diabetes mellitus, 25.5%; hypertension, 25.5%; and dyslipidemia, 29.8%. The prevalence in male and female patients was 7.7% and 7%, respectively. The prevalence of GB polyps was higher in south-eastern patients (21.4% of positive cases) and was the highest in the overweight group (8.8%). A higher prevalence was noted in the hypertensive group (hypertensive group, 9.8%; non-hypertensive group, 6.6%) and dyslipidemia group (dyslipidemia group, 7.8%; no dyslipidemia group, 7.2%). Moreover, a higher prevalence was noted in hepatitis B surface (HBS)-positive group (15%) than in the HBS-negative group (8.2%) and slightly higher in Helicobacter pylori antigen positive group than in the negative group. Conclusion: Abdominal US is an important and commonly used imaging modality in the detection of GB polyps. In this study, the prevalence of GB polyps was approximately 7.4%, with higher prevalence in participants who were overweight and had diabetes mellitus, hypertension, and dyslipidemia.
17
Sneed, Penny K., Jason W. Chan, Lijun Ma, Steve E. Braunstein, Philip V. Theodosopoulos, Shannon E. Fogh, Jean L. Nakamura, et al. "Adverse radiation effect and freedom from progression following repeat stereotactic radiosurgery for brain metastases." Journal of Neurosurgery, May 1, 2022, 1–9. http://dx.doi.org/10.3171/2022.4.jns212597.
Анотація:
OBJECTIVE The authors previously evaluated risk and time course of adverse radiation effects (AREs) following stereotactic radiosurgery (SRS) for brain metastases, excluding lesions treated after prior SRS. In the present analysis they focus specifically on single-fraction salvage SRS to brain metastases previously treated with SRS or hypofractionated SRS (HFSRS), evaluating freedom from progression (FFP) and the risk and time course of AREs. METHODS Brain metastases treated from September 1998 to May 2019 with single-fraction SRS after prior SRS or HFSRS were analyzed. Serial follow-up magnetic resonance imaging (MRI) and surgical pathology reports were reviewed to score local treatment failure and AREs. The Kaplan-Meier method was used to estimate FFP and risk of ARE measured from the date of repeat SRS with censoring at the last brain MRI. RESULTS A total of 229 retreated brain metastases in 124 patients were evaluable. The most common primary cancers were breast, lung, and melanoma. The median interval from prior SRS/HFSRS to repeat SRS was 15.4 months, the median prescription dose was 18 Gy, and the median duration of follow-up imaging was 14.5 months. At 1 year after repeat SRS, FFP was 80% and the risk of symptomatic ARE was 11%. The 1-year risk of imaging changes, including asymptomatic RE and symptomatic ARE, was 30%. Among lesions that demonstrated RE, the median time to onset was 6.7 months (IQR 4.7–9.9 months) and the median time to peak imaging changes was 10.1 months (IQR 5.6–13.6 months). Lesion size by quadratic mean diameter (QMD) showed similar results for QMDs ranging from 0.75 to 2.0 cm (1-year FFP 82%, 1-year risk of symptomatic ARE 11%). For QMD < 0.75 cm, the 1-year FFP was 86% and the 1-year risk of symptomatic ARE was only 2%. Outcomes were worse for QMDs 2.01–3.0 cm (1-year FFP 65%, 1-year risk of symptomatic ARE 24%). The risk of symptomatic ARE was not increased with tyrosine kinase inhibitors or immunotherapy before or after repeat SRS. CONCLUSIONS RE on imaging was common after repeat SRS (30% at 1 year), but the risk of a symptomatic ARE was much less (11% at 1 year). The results of repeat single-fraction SRS were good for brain metastases ≤ 2 cm. The authors recommend an interval ≥ 6 months from prior SRS and a prescription dose ≥ 18 Gy. Alternatives such as HFSRS, laser interstitial thermal therapy, or resection with adjuvant radiation should be considered for recurrent brain metastases > 2 cm.