Effects Of Reconstruction Filters Research Articles

Quantitative gated SPECT: the effect of reconstruction filter on calculated left ventricular ejection fractions and volumes

Gated SPECT (GSPECT) offers the possibility of obtaining additional functional information from perfusion studies, including calculation of left ventricular ejection fraction (LVEF). The calculation of LVEF relies upon the identification of the endocardial surface, which will be affected by the spatial resolution and statistical noise in the reconstructed images. The aim of this study was to compare LVEFs and ventricular volumes calculated from GSPECT using six reconstruction filters. GSPECT and radionuclide ventriculography (RNVG) were performed on 40 patients; filtered back projection was used to reconstruct the datasets with each filter. LVEFs and volumes were calculated using the Cedars–Sinai QGS package.The correlation coefficient between RNVG and GSPECT ranged from 0.81 to 0.86 with higher correlations for smoother filters. The narrowest prediction interval was 111 ± 2%. There was a trend towards higher LVEF values with smoother filters, the ramp filter yielding LVEFs 2.55 ± 3.10% (p < 0.001) lower than the Hann filter. There was an overall fall in ventricular volumes with smoother filters with a mean difference of 13.98 ± 10.15 ml (p < 0.001) in EDV between the Butterworth-0.5 and Butterworth-0.3 filters.In conclusion, smoother reconstruction filters lead to lower volumes and higher ejection fractions with the QGS algorithm, with the Butterworth-0.4 filter giving the highest correlation with LVEFs from RNVG. Even if the optimal filter is chosen the uncertainty in the measured ejection fractions is still too great to be clinically acceptable.

P6. The effect of reconstruction filter on ejection fractions and volumes calculated from gated SPECT

P6. The effect of reconstruction filter on ejection fractions and volumes calculated from gated SPECT

The effect of reconstruction filters on direct upconversion in a multichannel environment

The effect of reconstruction filters on direct upconversion is analyzed in a multichannel environment. It is shown that the reconstruction filters cause gain and phase imbalances to be frequency dependent, a significant issue when considering the stringent adjacent channel interference (ACI) requirements for radio communication systems. The paper introduces an adaptive compensation technique as a means of overcoming these frequency dependent imbalances. Additionally the error vector between the mismatched filters is shown to be directly related to the amount of sideband rejection. This analysis is then used to develop a methodology for analysing the performance of the novel compensation technique with respect to the mismatched filters. Analysis of the classical all-pole filter algorithms reveal the sensitivity of direct upconversion in a multichannel environment to filter order, type, percentage mismatch and differing ACI level.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Effects of reconstruction filters in digital predistortion linearizers for RF power amplifiers

The reconstruction filters are a major source of error in digital predistortion linearizers for RF power amplifiers. This paper presents a method that enables these filters to be designed for lowest filter complexity and minimum degradation of the linearizer performance. Furthermore, a method to choose an appropriate sampling rate for the predistorter is presented. Different filter approximations and orders are examined for different amplifier configurations by means of simulation. Of the filters tried, low-ripple Chebyshev and Butterworth filters perform best. It is demonstrated that it is possible to account for reasonable filter misalignment with only a small degradation in performance. It is also shown that the effect on the modulation is small with respect to intersymbol interference. >

Effects of reconstruction filters and sampling rate for a digital signal component separator on LINC transmitter performance

The authors investigate how reconstruction filters and sampling rate for a digital signal component separator affect the performance of an LINC transmitter. A method is described that, for a specified adjacent channel interference level, finds a nearly optimal cutoff frequency for a given filter approximation and the minimum sampling rate.

443. 小児腹部 MRI 検査における画像再構成フィルタの効果(MR-10 画像処理)

443. 小児腹部 MRI 検査における画像再構成フィルタの効果(MR-10 画像処理)

443. 小児腹部 MRI 検査における画像再構成フィルタの効果(第 48 回総会学術大会一般研究発表予稿)

443. 小児腹部 MRI 検査における画像再構成フィルタの効果(第 48 回総会学術大会一般研究発表予稿)

Detection of small focal lesions in CT images: effects of reconstruction filters and visual display windows.

The detectability of small, high-contrast lesions was measured on CT images, simulations of those obtained by the EMI Mark I scanner. Images were reconstructed using five reconstruction filters (kernels), which varied the image sharpness and noise level. Different sets of images were produced using various CT display windows, six different window sizes and four different display level settings. The measured lesion detectability for observers increased from 1.6 to 2.4 as the reconstruction kernel became smoother, and it decreased only slightly at the largest display window (1000 CT numbers wide). These effects were predicted by changes in the signal-to-noise ratio, as calculated for the lesion-matched filter applied to each set of physical CT images. This filter computes the cross-correlation of the CT image and the lesion profile at the specified possible locations for the lesion.