Filters in 2D and 3D Cardiac SPECT Image Processing

Lyra, Maria; Ploussi, Agapi; Rouchota, Maritina; Synefia, S.

doi:10.1155/2014/963264

Cited by 15 publications

(13 citation statements)

References 24 publications

(35 reference statements)

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“…However, with higher cutoff frequency, the image revealed two more pairs. Furthermore, our results depicted the smoother background which verifies that this filter is a high-smoothing filter, hence the loss in image detail and the degradation of contrast [4,26].…”

Section: International Journal Of Biomedical Imagingsupporting

confidence: 70%

“…Furthermore, it also indicated that the impact on image quality varies with respect to the size of hot regions as well as the count density in the region of interest which is the case in this study. Moreover, higher frequency corresponds to small regions and to abrupt changes in the count density of regions of interest [26][27][28][29].…”

Section: International Journal Of Biomedical Imagingmentioning

confidence: 99%

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Comparison of Low-Pass Filters for SPECT Imaging

Sayed

Ismail

2020

International Journal of Biomedical Imaging

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In single photon emission computed tomography (SPECT) imaging, the choice of a suitable filter and its parameters for noise reduction purposes is a big challenge. Adverse effects on image quality arise if an improper filter is selected. Filtered back projection (FBP) is the most popular technique for image reconstruction in SPECT. With this technique, different types of reconstruction filters are used, such as the Butterworth and the Hamming. In this study, the effects on the quality of reconstructed images of the Butterworth filter were compared with the ones of the Hamming filter. A Philips ADAC forte gamma camera was used. A low-energy, high-resolution collimator was installed on the gamma camera. SPECT data were acquired by scanning a phantom with an insert composed of hot and cold regions. A Technetium-99m radioactive solution was homogenously mixed into the phantom. Furthermore, a symmetrical energy window (20%) centered at 140 keV was adjusted. Images were reconstructed by the FBP method. Various cutoff frequency values, namely, 0.35, 0.40, 0.45, and 0.50 cycles/cm, were selected for both filters, whereas for the Butterworth filter, the order was set at 7. Images of hot and cold regions were analyzed in terms of detectability, contrast, and signal-to-noise ratio (SNR). The findings of our study indicate that the Butterworth filter was able to expose more hot and cold regions in reconstructed images. In addition, higher contrast values were recorded, as compared to the Hamming filter. However, with the Butterworth filter, the decrease in SNR for both types of regions with the increase in cutoff frequency as compared to the Hamming filter was obtained. Overall, the Butterworth filter under investigation provided superior results than the Hamming filter. Effects of both filters on the quality of hot and cold region images varied with the change in cutoff frequency.

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Section: International Journal Of Biomedical Imagingsupporting

confidence: 70%

Section: International Journal Of Biomedical Imagingmentioning

confidence: 99%

Comparison of Low-Pass Filters for SPECT Imaging

Sayed

Ismail

2020

International Journal of Biomedical Imaging

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“…In this study, 120 projections were taken instead of 64 projections as recommended by IAEA. [11] Also stated by [12] that high number of projections could prevent formation of the star artefact and blurring of the image. For reconstruction of images, all acquired SPECT image data (with and without material filter) were processed by using filtered back projection technique.…”

Section: Methodsmentioning

confidence: 99%

Flat sheet of Zinc material as a filter for gamma photons in Tc-99mm SPECT imaging

Abdullah¹,

Syed²,

Zakaria³

2018

IJET

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Purpose of the Study: Scattered gamma photons in single photon emission computed tomography (SPECT) is one of the main issues that degrade the image quality. There are several types of scatter correction methods. However, none of the technique is applied in routine clinical Tc-99m SPECT imaging. Therefore, Zinc (Zn) material filter was constructed for pre-filtration of scattered gamma photons in Tc-99m single photon emission computed tomography (SPECT).Materials and Methods: Tc-99m radioactivity was administered into the Carlson’s phantom. Planar and tomographic data were acquired with and without hot regions insert, respectively, with and without material filter. Scatter to non-scatter ratio was measured from the photopeak region of Tc-99m spectra. Tomographic images were generated using filtered back projection method. Contours on images were drawn with ImageJ software. Images obtained with and without material filter were analysed in terms of detectability of hot regions.Results: Remarkable decrease (≈ 21%) in the ratio of scattered to non-scattered gamma photons with material filter was achieved. Detectability of smaller hot regions with material filter was enhanced. In terms of sizes of all hot regions, material filter results appear closer to the original sizes.Conclusion: Material filter technique could be applied in Tc-99m clinical SPECT, while organ phantom studies are needed.

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“…However, the image quality is limited by a number of reasons; among them is noise [1]- [5]. Therefore, it is essential to carefully tackle this issue.…”

Section: Introductionmentioning

confidence: 99%

“…A higher order results in a sharper fall. However, both functions have a significant role to play in achieving a better quality image [5]- [7].…”

Section: Introductionmentioning

confidence: 99%

Effect of Cut-Off Frequency of Butterworth Filter on Detectability and Contrast of Hot and Cold Regions in Tc-99m SPECT

Sayed¹,

Nasrudin²

2016

IJMPCERO

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In SPECT, noise is one of the major limitations that degrade image quality. To suppress the noisy signals in an image, digital filters are most commonly applied. However, in SPECT image reconstruction, selection of an appropriate filter and its functions has always remained a difficult task. In this work an attempt was made to investigate the effects of varying cut-off frequencies and in keeping the order of Butterworth filter constant on detectability and contrast of hot and cold regions images. A new insert simulating hot and cold regions which provides similar views in a reconstructed image was placed in the phantom's cylindrical source tank and imaged. Tc-99m radionuclide was distributed uniformly in the phantom. SPECT data were collected in a 20% energy window centered at 140 keV by a Philips ADAC Forte dual head gamma camera mounted with a LEHR collimator. Images were generated by using the filtered backprojection technique. A Butterworth filter of order 5 with cut-off frequencies 0.35 and 0.45 cycles•cm −1 was applied. Images were examined in terms of hot and cold regions, detectability and contrast. Results show that the hot and cold regions' detectability and contrast vary with the change of cut-off frequency. With a 0.45 cycles•cm −1 cut-off frequency, a significant enhancement in contrast of cold regions was achieved as compared to a 0.35 cycles•cm −1 cut-off frequency. Furthermore, the detectability of hot and cold regions improved with the use of a 0.45 cycles•cm −1 cut-off frequency. In conclusion, image quality of hot and cold regions affected in a different way with a change of cut-off frequency. Thus, care should be taken in selecting the filter cut-off frequency prior to reconstruction of images; particularly, when both types of regions are expected in the reconstructed image.

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Filters in 2D and 3D Cardiac SPECT Image Processing

Cited by 15 publications

References 24 publications

Comparison of Low-Pass Filters for SPECT Imaging

Comparison of Low-Pass Filters for SPECT Imaging

Flat sheet of Zinc material as a filter for gamma photons in Tc-99mm SPECT imaging

Effect of Cut-Off Frequency of Butterworth Filter on Detectability and Contrast of Hot and Cold Regions in Tc-99m SPECT

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