Virtual magnetic resonance lumbar spine images generated from computed tomography images using conditional generative adversarial networks.

INTRODUCTION: The aim of this study was to generate virtual Magnetic resonance (MR) from computed tomography (CT) using conditional generative adversarial networks (cGAN). METHODS: We selected examinations from 22 adults who obtained their CT and MR lumbar spine examinations. Overall, 4 examinations were used as test data, and 18 examinations were used as training data. A cGAN was trained to generate virtual MR images from the CT images using the corresponding MR images as targets. After training, the generated virtual MR images from test data in epochs 1, 10, 50, 100, 500, and 1000 were compared with the original ones using the mean square error (MSE) and structural similarity index (SSIM). Additionally, two radiologists also performed qualitative assessments. RESULTS: The MSE of the virtual MR images decreased as the epoch of the cGANs increased from the original CT images: 8876.7 ± 1192.9 (original CT), 1567.5 ± 433.9 (Epoch 1), 1242.4 ± 442.0 (Epoch 10), 1065.8 ± 478.1 (Epoch 50), 1276.1 ± 718.9 (Epoch 100), 1046.7 ± 488.2 (Epoch 500), and 1031.7 ± 400.0 (Epoch 1000). No considerable differences were observed in the qualitative evaluation between the virtual MR images and the original ones, except in the structure of the spinal canal. CONCLUSION: Virtual MR lumbar spine images using cGANs could be a feasible technique to generate near-MR images from CT without MR examinations for evaluation of the vertebral body and intervertebral disc. IMPLICATIONS FOR PRACTICE: Virtual MR lumbar spine images using cGANs can offer virtual CT images with sufficient quality for attenuation correction for PET or dose planning in radiotherapy.

Coexistence of the Kondo effect and spin glass physics in Fe-doped NbS2.

We report the coexistence of the Kondo effect and spin glass behavior in Fe-doped NbS2 single crystals. The Fe x NbS2 shows the resistance minimum and negative magnetoresistance due to the Kondo effect, and exhibits no superconducting behavior at low temperatures. The resistance curve follows a numerical renormalization-group theory using the Kondo temperature [Formula: see text] K for x = 0.01 as evidence of Kondo effect. Scanning tunneling microscope/spectroscopy (STM/STS) revealed the presence of Fe atoms near sulfur atoms and asymmetric spectra. The magnetic susceptibility exhibits a feature of spin glass. The static critical exponents determined by the universal scaling of the nonlinear part of the susceptibility suggest a three-dimensional Heisenberg spin glass. The doped-Fe atoms in the intra- and inter-layers revealed by the x-ray result can realize the coexistence of the Kondo effect and spin glass.

Metal Artifact Reduction in Head CT Performed for Patients with Deep Brain Stimulation Devices: Effectiveness of a Single-Energy Metal Artifact Reduction Algorithm.

BACKGROUND AND PURPOSE: Deep brain stimulation electrodes induce massive artifacts on CT images, deteriorating the diagnostic value of examinations. We aimed to investigate the usefulness and potential limitations of a single-energy metal artifact reduction algorithm in head CT performed in patients with implanted deep brain stimulation devices. MATERIALS AND METHODS: Thirty-four patients with deep brain stimulation (bilateral, n = 28) who underwent head CT on a 320-detector row scanner and whose images were reconstructed with and without single-energy metal artifact reduction at the examinations were retrospectively included. The severity of artifacts around electrodes was assessed objectively using SDs and an artifact index. Two radiologists subjectively evaluated the severity of artifacts from electrodes, the visibility of electrode localization and surrounding structures, and overall diagnostic confidence on 4-point scales. Background image quality (GM-WM contrast and image noise) was subjectively and objectively assessed. The presence and location of artifacts newly produced by single-energy metal artifact reduction were analyzed. RESULTS: Single-energy metal artifact reduction provided lower objective and subjective metal artifacts and improved visualization of electrode localization and surrounding structures and diagnostic confidence compared with non-single-energy metal artifact reduction images, with statistical significance (all, P < .01). No significant differences were observed in GM-WM contrast and image noise (all, P ≥ .11). The new artifacts from single-energy metal artifact reduction were prominently observed in patients with bilateral deep brain stimulation at high convexity, possibly induced by deep brain stimulation leads placed under the parietal scalp. CONCLUSIONS: Single-energy metal artifact reduction substantially reduces the metal artifacts from deep brain stimulation electrodes and improves the visibility of intracranial structures without affecting background image quality. However, non-single-energy metal artifact reduction images should be simultaneously reviewed to accurately assess the entire intracranial area, particularly in patients with bilateral deep brain stimulation.

Dual-layer detector CT of chest, abdomen, and pelvis with a one-third iodine dose: image quality, radiation dose, and optimal monoenergetic settings.

AIM: To compare the image quality and radiation dose of reduced iodine dose dual-layer detector (DL) computed tomography (CT) with those of a conventional 120 kVp protocol for chest-abdomen-pelvis CT (CAP-CT). MATERIALS AND METHODS: Forty patients with renal dysfunction (estimated glomerular filtrating ratio <45 ml/min/1.73 m2) underwent reduced iodine dose CAP-CT (120 kVp, 200 mg iodine/kg) on DLCT. Virtual monochromatic images (VMI) at 40-70 keV (5 keV interval) were reconstructed retrospectively. Forty matched patients who underwent conventional CAP-CT (120 kVp, 600 mg iodine/kg, iterative reconstruction) were included as controls. The size-specific dose estimate (SSDE), image noise, CT attenuation, and contrast-to-noise ratio (CNR) were compared between the protocols. Two radiologists rated image contrast, image noise, streak artefact, and diagnostic confidence on a five-point scale. RESULTS: The SSDE of the DLCT group was approximately 20% lower than that of the 120 kVp group (15.4±1.9 versus 19.4±2.3 mGy, p<0.01). DLCT-VMI provided almost constant image noise throughout the range of energies (differences of ≤13%), with the noise being equivalent or lower than 120 kVp in the abdomen. CT attenuation and CNR gradually increased as the energy decreased, with values comparable to 120 kVp being attained at around 45-50 keV. Although streak artefact was accentuated at 40-50 keV (p<0.01), the highest scores for diagnostic confidence were assigned at 40 and 45 keV, both of which were equivalent to 120 kVp (p=1.0). CONCLUSION: For CAP-CT with a one-third iodine dose, DLCT-VMI at 40-45 keV allows for a 20% reduction in radiation dose, while preserving image quality comparable to that of conventional 120 kVp protocol.

Anaerobic Threshold by Mathematical Model in Healthy and Post-Myocardial Infarction Men.

The aim of this study was to determine the anaerobic threshold (AT) in a population of healthy and post-myocardial infarction men by applying Hinkley's mathematical method and comparing its performance to the ventilatory visual method. This mathematical model, in lieu of observer-dependent visual determination, can produce more reliable results due to the uniformity of the procedure. 17 middle-aged men (55±3 years) were studied in 2 groups: 9 healthy men (54±2 years); and 8 men with previous myocardial infarction (57±3 years). All subjects underwent an incremental ramp exercise test until physical exhaustion. Breath-by-breath ventilatory variables, heart rate (HR), and vastus lateralis surface electromyography (sEMG) signal were collected throughout the test. Carbon dioxide output (V˙CO2), HR, and sEMG were studied, and the AT determination methods were compared using correlation coefficients and Bland-Altman plots. Parametric statistical tests were applied with significance level set at 5%. No significant differences were found in the HR, sEMG, and ventilatory variables at AT between the different methods, such as the intensity of effort relative to AT. Moreover, important concordance and significant correlations were observed between the methods. We concluded that the mathematical model was suitable for detecting the AT in both healthy and myocardial infarction subjects.

Análise dos índices espectrais da variabilidade da freqüência cardíaca em homens de meia idade e mulheres na pós-menopausa / Analysis of spectral indexes for heart rate variability in middle-aged men and postmenopausal women

OBJETIVO: Analisar e comparar a variabilidade da freqüência cardíaca (VFC), em repouso, de homens e mulheres de meia-idade. MÉTODOS: Foram estudados 10 homens (54 ± 3,2 anos) e 14 mulheres na pós-menopausa (56 ± 2,6 anos) que não faziam uso de terapia hormonal. A freqüência cardíaca (FC) e os intervalos R-R foram obtidos a partir do eletrocardiograma, batimento a batimento, durante 8 minutos em repouso, nas posições supina e sentada. A VFC foi analisada no domínio da freqüência, usando a transformada rápida de Fourier, por meio da qual foram obtidas as bandas de baixa (BF) e alta freqüência (AF), as quais foram expressas em unidades normalizadas (AFun) e (BFun) e na razão BF/AF. Foram utilizados os testes estatísticos não-paramétricos de Mann-Whitney e de Wilcoxon, com nível de significância de alfa= 5 por cento. RESULTADOS: Na comparação intergrupo, as mulheres apresentaram maiores valores da banda AFun e menores valores da banda BFun e da razão BF/AF em relação aos homens, diferenças essas significativas (p<0,05). Na comparação intragrupo, não foram observadas diferenças significativas nos índices de VFC entre as posições supina e sentada para os 2 grupos estudados. CONCLUSÃO: Nossos resultados mostram uma maior modulação vagal e menor simpática no controle autonômico da FC para as mulheres em comparação aos homens de mesma idade, o que sugere que as diferenças autonômicas relacionadas ao gênero não se devem unicamente aos níveis hormonais de estrogênio, uma vez que as mulheres estudadas já se encontravam na fase pós-menopausa. Outros fatores podem estar contribuindo para essas diferenças.

OBJECTIVE: To analyze and compare heart rate variability (HRV) in middle-aged men and women under resting conditions. METHOD: Ten men (54 ± 3.2 years) and fourteen postmenopausal women (56 ± 2.6 years) who were not using hormonal therapy were studied. Heart rates (HR) and R-R intervals (iR-R) on a beat-to-beat basis were obtained from electrocardiograms over an eight-minute period under resting conditions, in the supine and sitting positions. The HRV was analyzed in the frequency domain by means of fast Fourier transforms and the low (LF) and high (HF) frequency bands were obtained and presented as normalized units (LFnu and HFnu) and the LF/HF ratio. Wilcoxon and Mann-Whitney non-parametric statistical tests were used, with the significance level set at 5 percent. RESULTS: Comparing between the groups, the women presented significantly higher HFnu and lower LFnu and LF/HF ratios than did the men (p<0.05). Comparing within the groups, no significant differences (p>0.05) were found in the HRV indexes between the supine and sitting positions for either study group. CONCLUSION: Our results show greater vagal modulation and lower sympathetic activity in autonomic heart rate control among women than among men of similar age. This suggests that the gender-related autonomic differences are not solely dependent on estrogen levels, since the women studied were already postmenopausal. Other factors may be contributing towards these differences.

Avaliação do controle autonomico da frequencia cardiaca e determinação do limiar de anaerobiose em homens saudaveis e coronariopatias / Evaluation of autonomic heart rate control and determination of anaerobic threshold among healthy and coronary heart-disead men

Avaliar a frequencia cardiaca (FC) e sua variabilidade (VFC) em repouso e durante teste de exercicio fisico dinamico descontinuo tipo degrau (TEFDD-d) em homens saudaveis sedentarios (SS) e infartados ativos (IA); determinar e comparar o limiar de anaerobiose (LA) dos grupos estudados. Metodologia: forma estudados 10 SS (52,5 anos)e 6 IA (59,2 anos) em repouso nas posicoes supino e sentado e em TEFDD-d realizado em cicloergometro, iniciando na potencia com decrescimo de 5 W e acrescimo de 5 W. A Fc (bpm) e os intervalos R-R (iR-R) em ms foram captados batimento a batimento em repouso e em TEFDD-d. Foram calculados os indices RMSSD dos iR_r e a FC media das condicoes de repouso e do trecho estavel de cada nivel de potencia. O LA foi determinado aplicando o modelo semiparametrico aos dados de Fc. Os testes estatisticos utilizados forma Wilcoxon, Mann Whitney e Friedmann, nivel de significancia p < 0,05. Resultados: Em repouso os valores de RMSSD dos iR-R e da FC nao atingiram diferencas estatisticas significativas entre os grupos, ja os SS apresentaram diferencas significativas nos valores de Fc durante a mudanca postural. No nivel potencia do LA ambos os grupos nao apresentaram reducoes significativas da VFC em comparacao com 25 W. Conclusao: nossos resultados sugerem que a atividade fisica regular realizada pelos IA contribuiu para manter a capacidade aerobica como modulacao autonomica da FC similares a dos SS

Comparação dos niveis de potencia e da frequencia cardiaca no limiar de anaerobiose determinado por dois metodos indiretos / Comparasion of power output and heart rate levels in anaerobic threshold determinations by two indirect methods

Analisar se protocolos individualizados do tipo rampa podem ser melhor que os do tipo degrau na determinacao do limiar de anaerobiose (LA). Metodo: 10 homens de meia idade (54+-3,25 anos) saudaveis e sedentarios foram submetidos a 2 testes de exercicio fisico dinamico em cicloergometro de frenagem eletromagnetica (Quinton Corival 400). O primeiro teste foi continuo do tipo rampa (TC-R), com incrementos de 15 W/min, ate a exaustao fisica. O segundo teste foi descontinuo do tipo degrau (TD-D). A frequencia cardiaca (FC) foi captada batimento a batimento e as variaveis ventilatorias e metabolicas, respiracao a respiracao, em tempo real. No TC-R o LA foi determinado pela metodlogia visual (media de 3 observadores) de analise das variaveis ventilatorias e metabolicas. Para determinacao do LA no TD-D foi aplicado o modelo matematico e estatistico semiparametrico ao conjunto de dados da FC. Analise estatistica Teste de wilcoxon para amostras pareadas com nivel de significancia (= 5 por cento). Resultados: foi observada diferenca estatisticamente significativa (p< 0,05) entre os valores de potencia no LA determinando no TC-R (66,5w) e no TD-D (45w). Os valores de FC nao foram estatisticamente diferentes (p > 0,05) entre 2 protocolos. Conclusoes: nossos dados mostram que no protocolo com cargas descontinuas, os voluntarios atingem o LA em niveis de potencia inferiores, porem com resposta do trabalho ardiaco similar a do exercicio realizado com protocolo continuo do tipo rampa. Isso sugere que a carga de trabalho durante o treinamento fisico para esses voluntarios devem ser a do protocolo descontinuo

Avaliação da variabilidade da frequencia cardíaca em repouso de homens saudáveis sedentários e de hipertensos e coronariopatias em treinamento físico / Resting heart rate variability in sedentary healthy men and in in trained men with hipertension and coronary heart disease

O objetivo deste estudo foi avaliar e comparar a variabilidade da frequencia cardiaca(VFC) em repouso supino e sentado de 10 homens de meia idade saudaveis (SA), 9 hipertensos (HA) e 9 com infarto do miocardio (IM), com idade media de 52, 62 e 56 anos, respectivamente. Os voluntarios SA nao praticavam atividade fisica frequentemente e os voluntarios HA e IM participavam de um programa de treinamento fisico aerobico (TFA) ha aproximadamente 3 anos. A frequencia cardiaca (FC) e os intervalos R-R(iR-R - ms) foram coletdos durante 900 s nas posicoes supina e sentada, e os voluntarios foram orientados a manter-se em repouso. Para a analise dos dados de dominio do tempo (DT), foi utilizado o indice RMSSD dos iR-R (ms). Para o dominio da frequencia (DF), foi aplicado um modelo auto-regressivo e obtidas as bandas de frequencia muito baixa (MBF), baixa (BF) e alta (AF), sendo os componentes BF e AF expressos em unidades normalizadas e na razao BF/AF. Foram utilizados os testes estatisticos nao-parametricos de Wilcoxon, de kruskall-Wallis e pos-hoc de Dunn. O nivel de significancia foi de a=5(por cento). Nao foram observadas diferencas estatisticamente significativas nos indices de VFC, avaliados no DT e no DF nas condicoes supino e sentado, nas comparacoes inter e intragrupo. Os resultados que a ausencia de diferencas entre os grupos estudados pode estar relacionada aos efeitos do do TFA realizadopelos HA e IM, comparativamente aos SA

Future doctors and brain death: what is the prognosis?

OBJECTIVE: To evaluate the knowledge and the opinion of medical students at the Pontifical Catholic University of São Paulo related to the general aspects of donation, organ and tissue procurement, and basic concepts of brain death (BD). MATERIALS AND METHODS: Questionnaires of 24 items were distributed among all students related to the concept and diagnosis of BD, personal aspects of tissue and organ donation, and general question concerning organ donation. The answers classified students as good versus bad experts of the concept and the diagnosis of BD. RESULTS: Of a total of 580 students, 361 (62.24%) answered the questionnaire. Although the concept of BD was known to 70%, only 35% had a good knowledge of the diagnosis. One percent of the students were opposed to the organ donation and 76% of them were donors. Approximately 90% would authorize organ retrieval from their family members but 27% had never discussed organ donation with their families. Most students were interested in the general aspects of donation and organ procurement (88.36%). CONCLUSION: The majority of the students know the concept of BD. General aspects regarding tissue and organ donation and diagnosis of BD might be improved with the continued education on the subject.

Portal vein aneurysm as late complication of liver transplantation: a case report.

OBJECTIVE: A case of intrahepatic portal vein aneurysm in the late postoperative period after liver transplantation, as well its complications, is reported. CASE REPORT: A 59-year-old man underwent orthotopic liver transplantation in 1996 for treatment of hepatitis C virus cirrhosis. The patient received a graft from a 10-year-old child. During the follow-up from 1996 to 1998, the patient did not show any alterations. In 1999, during an annual routine exam, a portal vein aneurysm was identified; however, it had no impact on graft function. In November 2002, the patient developed jaundice and serious graft dysfunction requiring hospital admission. Helicoidal CT scan showed an intrahepatic image compatible with a portal vein aneurysm without biliary tract dilatation. During the same hospitalization, he developed upper gastrointestinal bleeding due to variceal rupture as well as kidney and liver failure, and expired on December 31, 2002. The necropsy demonstrated an intrahepatic portal vein aneurysm with portal vein thrombosis and chronic liver disease. The evolution in this case suggests that if there is an intrahepatic portal vein aneurysm after liver transplantation, the patient is likely to experience an eventual recurrence of portal hypertension; retransplant may be an alternative.

Analise da modulacao autonomica do coracao durante condicoes de repouso em homens de meia idade e mulheres pos-menopausa / Analysis of heart autonomic modulation during resting conditions in middle-aged men and postmenopausal women

O controle autonomico do coracao pode ser investigado a partir da analise da variabilidade da requencia cardiaca (VFC). Sabe-se que o aparecimento de doencas cardiovasculares (DCV) em mulheres aumenta com a idade, principalmente apos a menopausa, quando o risco torna-se similar ao observado em homens. Assim, o objetivo deste trabalho e analisar e comparar a VFC de homens de meia-idade e de mulheres pos-menopausa em condicoes de repouso. Foram estudados dois grupos saudaveis e sedentarios, sendo 10 homens de meia-idade (52,6 +- 2,63 anos) e 10 mulheres pos-menopausa (56,8+-5,09 anos) que nao faziam uso de terapia de reposicao hormonal. A frequencia cardiaca e os intervalos R-R (iR-R) foram obtidos a partir de eletrocardiograma em tempo real, batimento a batimento, durante 6 minutos em condicoes de repouso, nas posicoes supina(S) e sentada(SE). Para analise da VFC foram calculados os indices RMSM e RMSSD dos iR-R em milissegundo(ms). Nao foram observadas diferencas estatisticamente significativas nos valores dos indices RMSM e RMSSD entre os homens e as mulheres e entre as posicoes supina e sentada de ambos os grupos. A reducao da VFC observada em ambos os grupos estudados sugere similar decrescimo da modulacao parasimpatica sobre o coracao, fato que pode contribuir para o aumento do risco de DCV observado nessa faixa etaria em ambos os sexos