Method for reducing background artifacts from images in single-photon emission computed tomography with a uniformly redundant array coded aperture

Vassilieva, Olga; Chaney, Roy C.

doi:10.1364/ao.41.001454

Cited by 20 publications

(18 citation statements)

References 8 publications

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“…The ideal CM has negligible thickness, but real CMs are designed with the minimum thickness that allows to achieve a good absorption. This fact produces partial collimation effect 16,17 in the holes, originating artifacts in images. These problems have been extensively investigated [18][19][20][21][22] and some progress and improvements were achieved in some cases, that are reflected in invention patents.…”

Section: Introductionmentioning

confidence: 99%

Stereoscopic full aperture imaging in nuclear medicine

Strocovsky

Otero

2011

AIP Advances

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Images of planar scintigraphy and single photon emission computerized tomography (SPECT) used in nuclear medicine are often low quality. They usually appear to be blurred and noisy. This problem is due to the low spatial resolution and poor sensitivity of the acquisition technique with the gamma camera (GC). Other techniques, such as coded aperture imaging (CAI) reach higher spatial resolutions than GC. However, CAI is not frequently used for imaging in nuclear medicine, due to the decoding complexity of some images and the difficulty in controlling the noise magnitude. Summing up, the images obtained through GC are low quality and it is still difficult to implement CAI technique. A novel technique, full aperture Imaging (FAI), also uses gamma ray-encoding to obtain images, but the coding system and the method of images reconstruction are simpler than those used in CAI. In addition, FAI also reaches higher spatial resolution than GC. In this work, the principles of FAI technique and the method of images reconstruction are explained in detail. The FAI technique is tested by means of Monte Carlo simulations with filiform and spherical sources. Spatial resolution tests of GC versus FAI were performed using two different sourcedetector distances. First, simulations were made without interposing any material between the sources and the detector. Then, other more realistic simulations were made. In these, the sources were placed in the centre of a rectangular prismatic region, filled with water. A rigorous comparison was made between GC and FAI images of the linear filiform sources, by means of two methods: mean fluence profile graphs and correlation tests. Finally, three-dimensional capacity of FAI was tested with two spherical sources. The results show that FAI technique has greater sensitivity (>100 times) and greater spatial resolution (>2.6 times) than that of GC with LEHR collimator, in both cases, with and without attenuating material and long and shortdistance configurations. The FAI decoding algorithm reconstructs simultaneously four different projections which are located in separate image fields on the detector plane, while GC produces only one projection per acquisition. Simulations have allowed comparison of both techniques under ideal identical conditions. Our results show it is possible to apply an extremely simple encoded imaging technique, and get three-dimensional radioactivity information for simplistic geometry sources. The results are promising enough to evaluate the possibility of future research with more complex sources typical of nuclear medicine imaging.

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Section: Introductionmentioning

confidence: 99%

Stereoscopic full aperture imaging in nuclear medicine

Strocovsky

Otero

2011

AIP Advances

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“…They are initially expected to be equally successful in tomography. Unfortunately, the contribution of higher background of their autocorrelation function (about 1/2 of peak intensity) creates artifacts in the reconstructed image, which significantly reduce the SNR in the reconstructed image and lead to false images [2,12]. When noises considerations are made, nonredundant arrays (NRAs) are endowed with many advantages which URAs do not possess.…”

Section: Introductionmentioning

confidence: 99%

Design of NRAs having higher aperture opening ratio and autocorrelation compression ratio by means of a global optimization method

Lang

Liu

Yang

2007

Optik

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“…Although imaging technologies are critically important in medical research and practice, coded masks for γ -ray imaging are not used here, because three-dimensional imagery by other techniques (e.g., computer assisted tomography) is substantially superior. For example, Vassilieva and Chaney (2002) noted that after 20 years of research, coded imaging has not been successfully migrated from astronomy to medicine, because medical images behave as distributed sources (near-to-source imaging), and coded mask imaging is optimal when applied to images that behave as point sources. van Eijk (2002) offered a comprehensive review of medical imaging technologies with no mention of coded mask techniques.…”

Section: Introductionmentioning

confidence: 99%

Detection and Location of Gamma-Ray Sources With a Modulating Coded Mask

Anderson¹,

Stromswold²,

Wunschel³

et al. 2006

Technometrics

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The detection of high-energy γ -ray sources is vitally important to national security for numerous reasons, particularly nuclear materials smuggling interdiction and threat detection. This article presents two methods of detecting and locating a concealed nuclear γ -ray source by analyzing detector data of emissions that have been modulated with a coded mask. The advantages of each method, derived from a simulation study and experimental data, are discussed. Energetic γ -rays readily penetrate moderate amounts of shielding material and can be detected at distances of many meters. Coded masks are spatial configurations of shielding material (e.g., small squares formed from plates of lead or tungsten) placed in front of a detector array to modulate the radiation distribution. A coded mask system provides improved detection through an increased signal-to-noise ratio. In a search scenario it is impossible to obtain a comparison background run without the presence of a potential concealed source. The developed analysis methods simultaneously estimate background and source emissions and thus provide the capability to detect and locate a concealed high-energy radiological source in near real time. An accurate source location estimate is critically important to expedite the investigation of a high-probability γ -ray source. The experimental examples presented use a proof-of-concept coded mask system of a 4 × 4 array of NaI detectors directed at a γ -ray source in a field-of-view roughly 4 m wide × 3 m high (approximately the size of the side panel of a small freight truck). Test results demonstrate that the correct location of a radiologic source could be determined in as little as 100 seconds when the source was 6 m from the detector.

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Method for reducing background artifacts from images in single-photon emission computed tomography with a uniformly redundant array coded aperture

Cited by 20 publications

References 8 publications

Stereoscopic full aperture imaging in nuclear medicine

Stereoscopic full aperture imaging in nuclear medicine

Design of NRAs having higher aperture opening ratio and autocorrelation compression ratio by means of a global optimization method

Detection and Location of Gamma-Ray Sources With a Modulating Coded Mask

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