نتایج جستجو برای: Collimator-detector response

تعداد نتایج: 1033857  

Journal: :iranian journal of nuclear medicine 2011
faraz kalantari hossein rajabi mohsen saghari alireza emami ardekani

introduction: monte carlo (mc) is the most common method for simulating virtual spect projections. it is useful for optimizing procedures, evaluating correction algorithms and more recently image reconstruction as a forward projector in iterative algorithms; however, the main drawback of mc is its long run time. we introduced a model based method considering the effect of body attenuation and i...

Journal: :iranian journal of nuclear medicine 0
hojjat mahani radiation application research school, nuclear science and technology research institute, tehran, iran gholamreza raisali radiation application research school, nuclear science and technology research institute, tehran, iran alireza kamali-asl radiation medicine department, shahid beheshti university, tehran, iran mohammad reza ay research center for molecular and cellular imaging, tehran university of medical science, tehran, iran

introduction:it is well-recognized that collimator-detector response (cdr) is the main image blurring factor in spect.  in this research, we compensated the images for cdr in molecular spect by using stir reconstruction framework. methods: to assess resolution recovery capability of the stir, a phantom containing five point sources along with a micro derenzo phantom were investigated. influence...

2006
Alireza Kargar Andrew M. Jones Walter J. McNeil Mark J. Harrison Douglas S. McGregor

The spatial resolution of a collimated CdZnTe Frisch collar detector was experimentally investigated for two different tungsten collimator designs using a Au gamma-ray source at 412 keV. A two-dimensional model for the detector–collimator–source geometry was developed and applied with some simplifying assumptions. The CdZnTe detector was fabricated from a single crystal using a copper shim as t...

Journal: :Medical physics 2002
Gengsheng L Zeng Daniel Gagnon Christopher G Matthews Jeffery A Kolthammer Jason D Radachy William G Hawkins

A slat collimator in single photon emission computed tomography consists of a set of parallel slats. As the collimator spins, the detector measures a one-dimensional projection data set. A complete data set can be obtained by rotating the detector/collimator assembly around the object (patient) while the collimator spins continuously. The measured projection data are assumed to be weighted plan...

Journal: :iranian journal of nuclear medicine 0
alireza sadremomtaz department of physics, faculty of science, university of guilan, rasht, iran zeinab telikani department of physics, faculty of science, university of guilan, rasht, iran

introduction: image quality and accuracy of in vivo activity quantification in spect are affected by collimator penetration and scatter components, especially in high energy imaging. these phenomena highly depend on the collimator characteristic and photon energy. the presence of penetrated and scattered photons from collimator in spect images degrades spatial resolution, contrast and image qua...

Jalil Pirayesh Islamian, Parvaneh Darkhor Samira Abbaspour

Introduction: In nuclear medicine, the use of a pixelated semiconductor detector such as CZT is an of growing interest for introducing new devices. Especially, the spatial resolution can be improved by using a pixelated parallel-hole collimator with equal holes and pixel sizes based on the pixelated detector. The purpose of this study was to compare the effect of pixelated and ...

Alireza Emami-Ardekani Alireza Mardanshahi, Faraz Kalantari, Mahmoud Bagheri Mohammad Sobhan Ardekani Nasim Namiranian Reza Nafisi-Moghadam Seid Kazem Razavi-Ratki, Seyed Hossein Razavi,

Introduction:In an ideal parallel-hole collimator, thickness of septal material should be sufficient to stop more than 95% of incident photons. However, some photons pass the septa without interaction or experience scattering before they reach the detector. In this study, we determined different contribution of collimator responses consist of geometrical response, septal penetr...

Journal: :Medical physics 2011
Charlotte Robert Guillaume Montémont Véronique Rebuffel Loïck Verger Irène Buvat

PURPOSE Small field-of-view CdZnTe (CZT) gamma cameras are increasingly studied for breast lesion detection to complement mammography or ultrasonographic findings. However, in classical collimation configurations, they remain limited by the trade-off between spatial resolution and sensitivity. The HiSens architecture was proposed to overcome these limitations. Using an accurate 3D localization ...

Journal: :Annals of nuclear medicine 2006
Nobutoku Motomura Kyojiro Nambu Akihiro Kojima Seiji Tomiguchi Koichi Ogawa

Due to the collimator aperture, spatial resolution of SPECT data varies with source-to-detector distance. Since the radius of detector rotation is bigger when scanning larger patients, spatial resolution is degraded in these cases. Emitted gamma rays travel not only along the central axis of the collimator hole but also off-axis due to the collimator aperture. However, an off-axis ray at one an...

2002
Toru GOTO Yu GONG

The problems caused by miniaturization of the goniometer are discussed from the viewpoint of the stress error caused by mis-setting of the specimen and misalignment of the collimator and detector for the Q assembly X-ray stress analyzer using a position sensitive detector. The stress errors were calculated using a model and a simulation method. It was found that they tend to increase with the d...

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