Lina Vieira

Influence of Reconstruction Parameters During Filtered Backprojection and Ordered-Subset Expectation Maximization in the Measurement of the Left-Ventricular Volumes and Function During Gated SPECT

A crucial method for investigating patients with coronary artery disease (CAD) is the calculation of the left ventricular ejection fraction (LVEF). It is, consequently, imperative to precisely estimate the value of LVEF—a process that can be done with myocardial perfusion scintigraphy. Therefore, the present study aimed to establish and compare the estimation performance of the quantitative parameters of the reconstruction methods filtered backprojection (FBP) and ordered-subset expectation maximization (OSEM). Methods: A beating-heart phantom with known values of end-diastolic volume, end-systolic volume, and LVEF was used. Quantitative gated SPECT/quantitative perfusion SPECT software was used to obtain these quantitative parameters in a semiautomatic mode. The Butterworth filter was used in FBP, with the cutoff frequencies between 0.2 and 0.8 cycles per pixel combined with the orders of 5, 10, 15, and 20. Sixty-three reconstructions were performed using 2, 4, 6, 8, 10, 12, and 16 OSEM subsets, combined with several iterations: 2, 4, 6, 8, 10, 12, 16, 32, and 64. Results: With FBP, the values of end-diastolic, end-systolic, and the stroke volumes rise as the cutoff frequency increases, whereas the value of LVEF diminishes. This same pattern is verified with the OSEM reconstruction. However, with OSEM there is a more precise estimation of the quantitative parameters, especially with the combinations 2 iterations × 10 subsets and 2 iterations × 12 subsets. Conclusion: The OSEM reconstruction presents better estimations of the quantitative parameters than does FBP. This study recommends the use of 2 iterations with 10 or 12 subsets for OSEM and a cutoff frequency of 0.5 cycles per pixel with the orders 5, 10, or 15 for FBP as the best estimations for the left ventricular volumes and ejection fraction quantification in myocardial perfusion scintigraphy.

Monte Carlo simulation of the basic features of the GE Millennium MG single photon emission computed tomography gamma camera

OBJECTIVE To describe and validate the simulation of the basic features of GE Millennium MG gamma camera using the GATE Monte Carlo platform. MATERIAL AND METHODS Crystal size and thickness, parallel-hole collimation and a realistic energy acquisition window were simulated in the GATE platform. GATE results were compared to experimental data in the following imaging conditions: a point source of (99m)Tc at different positions during static imaging and tomographic acquisitions using two different energy windows. The accuracy between the events expected and detected by simulation was obtained with the Mann-Whitney-Wilcoxon test. Comparisons were made regarding the measurement of sensitivity and spatial resolution, static and tomographic. Simulated and experimental spatial resolutions for tomographic data were compared with the Kruskal-Wallis test to assess simulation accuracy for this parameter. RESULTS There was good agreement between simulated and experimental data. The number of decays expected when compared with the number of decays registered, showed small deviation (≤ 0.007%). The sensitivity comparisons between static acquisitions for different distances from source to collimator (1, 5, 10, 20, 30 cm) with energy windows of 126-154 keV and 130-158 keV showed differences of 4.4%, 5.5%, 4.2%, 5.5%, 4.5% and 5.4%, 6.3%, 6.3%, 5.8%, 5.3%, respectively. For the tomographic acquisitions, the mean differences were 7.5% and 9.8% for the energy window 126-154 keV and 130-158 keV. Comparison of simulated and experimental spatial resolutions for tomographic data showed no statistically significant differences with 95% confidence interval. CONCLUSIONS Adequate simulation of the system basic features using GATE Monte Carlo simulation platform was achieved and validated.

Influência da escala de cores na avaliação qualitativa em cintigrafia de perfusão cerebral

Since 2004, formaldehyde (FA) has been classified by the International Agency for Cancer Research as a carcinogen. The FA ranks 25th in the overall United States chemical production, with more than 5 million tons produced each year. Due to its economic importance and varied use, many individuals are exposed to FA at their occupational settings. This study aimed to assess the exposure to FA in two occupational settings – FA production factory and pathology anatomy (PA) laboratories – and relate it to possible health effects by comparing frequency of micronuclei (MN) in peripheral bloodIntroducao: As desigualdades em saude sao reconhecidamente um problema de saude publica. A relacao entre determinantes sociais e as desigualdades em saude sao um achado robusto. Enquanto nos adultos e claro que estas desigualdades socioeconomicas se manifestam no seu estado de saude, a situacao e menos clara nas criancas e adolescentes. Foi entao efetuada uma revisao da literatura sobre a influencia dos determinantes sociais na saude na idade pediatrica. De forma a contribuir para um melhor conhecimento sobre a materia. Metodologia: A pesquisa foi efetuada segundo as normas PRISMA, com base nos termos MeSH: Social Class, Pediatric, Hospital, Emergency Treatment, Socioeconomic factor e Healthcare Disparities, na PubMed, Scielo e nas bases de dados da Cochrane. Foram excluidos artigos de revisao, opiniao bem como artigos que tratavam de questoes de acesso aos cuidados. Foi efetuada uma descricao quantitativa e qualitativa dos resultados. Resultados: Foram selecionadas 17 publicacoes, exceto uma do tipo descritiva, todas referentes a estudos observacionais analiticos, a maioria usando dados retrospetivos. Encontrou-se forte evidencia na relacao entre desigualdades em saude e os fatores socio economicos na idade pediatrica. Conclusao: Apesar de nenhuma das publicacoes selecionadas apresentar dados colhidos em Portugal, e seguro afirmar que e possivel encontrar a mesma relacao na idade pediatrica. E importante estudar mais esta area, identificar os determinantes sociais mais importantes bem como as populacoes mais vulneraveis, para melhor poder planear os cuidados de saude e combater as desigualdades. Palavras-Chave: Desigualdades em Saude, Determinantes Sociais da Saude, Fatores Socio-economicos, Pediatria

Imagej's contribution to left ventricular segmentation in myocardial perfusion imaging

Introduction The Myocardial Perfusion Imaging (MPI) is a non-invasive image test that allows the assessment of perfusion, function and viability of the Left Ventricle (LV). The quantitative parameters obtained post-reconstruction requires an accurate segmentation of the LV. ImageJ is an open-source software that provides segmentation techniques that may contribute to the segmentation of the LV in the MPI.The purpose of this study was to study the influence of the different segmentation methods provided by ImageJ, in MPI, depending on the administered activity. Material and methods We carried out an experimental research with 4 MPI studies simulated with 275, 385, 500 and 750 Bq/voxel in the myocardium, whose short-axis (SA) slices were segmented with ImageJ by the threshold default, OTSU and k-means Plugin Toolkit methods (k=2, k=3). To analyze the most appropriate segmentation method, the signal-to-noise ratio (SNR) for each short-axis (SA) slice was calculated, in accordance with the slices obtained from the software Quantitative Perfusion Single Photon Emission Computed Tomography® (QPS®) and by manual segmentation using ImageJ. To analyze the SNR with ImageJ and QPS® segmentation methods in the same simulated study, and to compare with the same segmentation method in different simulated studies, the Friedman and Kruskal-Wallis tests were applied. Results and discussion The method k-means with k=3 is the most suitable method for the segmentation of the LV, regardless of the administered activity. Conclusion This study may contribute to the clinical implementation of open-source based segmentation methods of the LV in MPI, according to the activity in the myocardium. Correspondence to: Sousa CLD, Instituto Politécnico de Lisboa, Lisbon 1990096, Portugal, Email:carlota.leonardo.sousa@gmail.com

Influência da escala de cores na avaliação qualitativa das imagens de cintigrafia de perfusão do miocárdio

Since 2004, formaldehyde (FA) has been classified by the International Agency for Cancer Research as a carcinogen. The FA ranks 25th in the overall United States chemical production, with more than 5 million tons produced each year. Due to its economic importance and varied use, many individuals are exposed to FA at their occupational settings. This study aimed to assess the exposure to FA in two occupational settings – FA production factory and pathology anatomy (PA) laboratories – and relate it to possible health effects by comparing frequency of micronuclei (MN) in peripheral bloodIntroducao: As desigualdades em saude sao reconhecidamente um problema de saude publica. A relacao entre determinantes sociais e as desigualdades em saude sao um achado robusto. Enquanto nos adultos e claro que estas desigualdades socioeconomicas se manifestam no seu estado de saude, a situacao e menos clara nas criancas e adolescentes. Foi entao efetuada uma revisao da literatura sobre a influencia dos determinantes sociais na saude na idade pediatrica. De forma a contribuir para um melhor conhecimento sobre a materia. Metodologia: A pesquisa foi efetuada segundo as normas PRISMA, com base nos termos MeSH: Social Class, Pediatric, Hospital, Emergency Treatment, Socioeconomic factor e Healthcare Disparities, na PubMed, Scielo e nas bases de dados da Cochrane. Foram excluidos artigos de revisao, opiniao bem como artigos que tratavam de questoes de acesso aos cuidados. Foi efetuada uma descricao quantitativa e qualitativa dos resultados. Resultados: Foram selecionadas 17 publicacoes, exceto uma do tipo descritiva, todas referentes a estudos observacionais analiticos, a maioria usando dados retrospetivos. Encontrou-se forte evidencia na relacao entre desigualdades em saude e os fatores socio economicos na idade pediatrica. Conclusao: Apesar de nenhuma das publicacoes selecionadas apresentar dados colhidos em Portugal, e seguro afirmar que e possivel encontrar a mesma relacao na idade pediatrica. E importante estudar mais esta area, identificar os determinantes sociais mais importantes bem como as populacoes mais vulneraveis, para melhor poder planear os cuidados de saude e combater as desigualdades. Palavras-Chave: Desigualdades em Saude, Determinantes Sociais da Saude, Fatores Socio-economicos, Pediatria

The influence of number of counts in the myocardium in the determination of reproducible functional parameters in gated-SPECT studies simulated with GATE

UNLABELLED Myocardial perfusion gated-single photon emission computed tomography (gated-SPECT) imaging is used for the combined evaluation of myocardial perfusion and left ventricular (LV) function. The aim of this study is to analyze the influence of counts/pixel and concomitantly the total counts in the myocardium for the calculation of myocardial functional parameters. MATERIAL AND METHODS Gated-SPECT studies were performed using a Monte Carlo GATE simulation package and the NCAT phantom. The simulations of these studies use the radiopharmaceutical (99m)Tc-labeled tracers (250, 350, 450 and 680 MBq) for standard patient types, effectively corresponding to the following activities of myocardium: 3, 4.2, 5.4-8.2 MBq. All studies were simulated using 15 and 30s/projection. The simulated data were reconstructed and processed by quantitative-gated-SPECT software, and the analysis of functional parameters in gated-SPECT images was done by using Bland-Altman test and Mann-Whitney-Wilcoxon test. RESULTS In studies simulated using different times (15 and 30s/projection), it was noted that for the activities for full body: 250 and 350 MBq, there were statistically significant differences in parameters Motility and Thickness. For the left ventricular ejection fractio n (LVEF), end-systolic volume (ESV) it was only for 250 MBq, and 350 MBq in the end-diastolic volume (EDV), while the simulated studies with 450 and 680MBq showed no statistically significant differences for global functional parameters: LVEF, EDV and ESV. CONCLUSION The number of counts/pixel and, concomitantly, the total counts per simulation do not significantly interfere with the determination of gated-SPECT functional parameters, when using the administered average activity of 450 MBq, corresponding to the 5.4 MBq of the myocardium, for standard patient types.