Comparative study between two distinct methods for attenuation correction and the use of no-attenuation correction for the assessment of relative uptake of 99mTc-DMSA on pediatric patients

Introduction: Although relative uptake values aren’t the most important objective of a 99mTc-DMSA scan, they are important quantitative information. In most of the dynamic renal scintigraphies attenuation correction is essential if one wants to obtain a reliable result of the quantification process. Although in DMSA scans the absent of significant background and the lesser attenuation in pediatric patients, makes that this attenuation correction techniques are actually not applied. The geometric mean is the most common method, but that includes the acquisition of an anterior (extra) projection, which it is not acquired by a large number of NM departments. This method and the attenuation factors proposed by Tonnesen will be correlated with the absence of attenuation correction procedures. Material and Methods: Images from 20 individuals (aged 3 years +/- 2) were used and the two attenuation correction methods applied. The mean time of acquisition (time post DMSA administration) was 3.5 hours +/- 0.8h. Results: The absence of attenuation correction showed a good correlation with both attenuation methods (r=0.73 +/- 0.11) and the mean difference verified on the uptake values between the different methods were 4 +/- 3. The correlation was higher when the age was lower. The attenuation correction methods correlation was higher between them two than with the “no attenuation correction” method (r=0.82 +/- 0.8), and the mean differences of the uptake values were 2 +/- 2. Conclusion: The decision of not doing any kind of attenuation correction method can be justified by the minor differences verified on the relative kidney uptake values. Nevertheless, if it is recognized that there is a need for an accurate value of the relative kidney uptake, then an attenuation correction method should be used. Attenuation correction factors proposed by Tonnesen can be easily implemented and so become a practical and easy to implement alternative, namely when the anterior projection - needed for the geometric mean methodology – is not acquired.

Phase correction for passive radar using targets of opportunity

This paper presents a novel phase correction technique for Passive Radar which uses targets of opportunity present in the target area as references. The proposed methodology is quite simple and enables the use of low cost hardware with independent oscillators for the reference and surveillance channels which can be geographically distributed. © 2014 IEEE.

Paired indices for clustering evaluation correction for agreement by chance

In the present paper we focus on the performance of clustering algorithms using indices of paired agreement to measure the accordance between clusters and an a priori known structure. We specifically propose a method to correct all indices considered for agreement by chance - the adjusted indices are meant to provide a realistic measure of clustering performance. The proposed method enables the correction of virtually any index - overcoming previous limitations known in the literature - and provides very precise results. We use simulated datasets under diverse scenarios and discuss the pertinence of our proposal which is particularly relevant when poorly separated clusters are considered. Finally we compare the performance of EM and KMeans algorithms, within each of the simulated scenarios and generally conclude that EM generally yields best results.

Influence of computed tomography attenuation correction in myocardial perfusion imaging in obese population

Marked regional variations in myocardial activity that are not related to myocardial perfusion defects.Verify the influence of CT-AC inMPI results in patients with BMI between 30 and 35 and higher than 30 for male and female population.

Influence of attenuation correction in the MPI image reconstructed by the ‘Evolution for Cardiac’™

The acquisition of a Myocardial Perfusion image (MPI) is of great importance for the diagnosis of the coronary artery disease, since it allows to evaluate which areas of the heart aren’t being properly perfused, in rest and stress situations. This exam is greatly influenced by photon attenuation which creates image artifacts and affects quantification. The acquisition of a Computerized Tomography (CT) image makes it possible to get an atomic images which can be used to perform high-quality attenuation corrections of the radiopharmaceutical distribution, in the MPI image. Studies show that by using hybrid imaging to perform diagnosis of the coronary artery disease, there is an increase on the specificity when evaluating the perfusion of the right coronary artery (RCA). Using an iterative algorithm with a resolution recovery software for the reconstruction, which balances the image quality, the administered activity and the scanning time, we aim to evaluate the influence of attenuation correction on the MPI image and the outcome in perfusion quantification and imaging quality.

Multiple sequence alignment correction using constraints

Trabalho apresentado no âmbito do European Master in Computational Logics, como requisito parcial para obtenção do grau de Mestre em Computational Logics

Correction of spatial distortion in magnetic resonance imaging

Dissertation to Obtain the Degree of Master in Biomedical Engineering

Sensitivity correction of images obtained with the prototype Clear-PEM in pre-clinical environment

Dissertation presented at Faculdade de Ciências e Tecnologia Universidade Nova de Lisboa to obtain a Master Degree in Biomedical Engineering

Cement-cork mortars for thermal bridges correction. Comparison with cement-EPS mortars performance

Construction and Building Materials 49 (2013), 315-327

Correction of the anisotropy in resistivity: application to pore pressure prediction

Dissertação para obtenção do Grau de Mestre em Engenharia Geológica (Georrecursos)

The efficacy of the old way/new way methodology on the correction of an automated technical error and its impact on the athlete’s psychological skills : Case study in tennis

The aim of this study was to evaluated the efficacy of the Old Way/New Way methodology (Lyndon, 1989/2000) with regard to the permanent correction of a consolidated and automated technical error experienced by a tennis athlete (who is 18 years old and has been engaged in practice mode for about 6 years) in the execution of serves. Additionally, the study assessed the impact of intervention on the athlete’s psychological skills. An individualized intervention was designed using strategies that aimed to produce a) a detailed analysis of the error using video images; b) an increased kinaesthetic awareness; c) a reactivation of memory error; d) the discrimination and generalization of the correct motor action. The athlete’s psychological skills were measured with a Portuguese version of the Psychological Skills Inventory for Sports (Cruz & Viana, 1993). After the intervention, the technical error was corrected with great efficacy and an increase in the athlete’s psychological skills was verified. This study demonstrates the methodology’s efficacy, which is consistent with the effects of this type of intervention in different contexts.

Correction of the initial conditions

"Series title: Springerbriefs in applied sciences and technology, ISSN 2191-530X"

Anomalous origin of the left pulmonary artery from the ascending aorta: successful surgical correction in an infant with fallot's tetralogy

We describe the case of a 40-day-old female patient with a history of breathlessness since birth who was referred to our hospital for surgical correction of common arterial trunk. The invasive investigation disclosed a Fallot¢s tetralogy anatomy associated with an anomalous origin of the left pulmonary artery from the ascending aorta. Immediately after diagnosis, the patient underwent a successful total surgical correction of the defect, including simultaneous anastomosis of the left pulmonary artery to the pulmonary trunk.