In Vivo Dual-Isotope SPECT Imaging with Improved Energy Resolution

Wagenaar, Douglas J.; Zhang, J.; Kazules, Tim; Vandehei, T.; Bolle, E.; Chowdhury, S.; Parnham, K.; Patt, Bradley E.

doi:10.1109/nssmic.2006.353824

Cited by 24 publications

(18 citation statements)

References 3 publications

(1 reference statement)

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“…C OMPOUND semiconductors such as CdZnTe that operate at room temperature with high sensitivity and high stopping power are being utilized in many applications including industrial gauging, nuclear safeguards, transportation security, medical and industrial imaging, along with a range of scientific applications including astrophysics [1]- [4]. Recently there is a growing interest to use the detectors for high flux multi-energy binning imaging [5].…”

Section: Introductionmentioning

confidence: 99%

Dynamic Lateral Polarization in CdZnTe Under High Flux X-Ray Irradiation

Soldner

Bale

Szeles

2007

IEEE Trans. Nucl. Sci.

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The dynamic lateral polarization and charge steering effect was studied in 2D pixilated CdZnTe monolithic detector arrays designed for high flux x-ray imaging applications. While these detectors have shown the ability to work at 15 10 6 counts/s/mm 2 and higher count-rates in pulse mode, we observed some detectors that exhibited a dynamic lateral polarization and charge steering effect causing non-uniform spatial response to the radiation field. The dynamic nature of the effect is shown by its flux dependence and reversibility upon changing the x-ray flux without a requirement to turn off the bias voltage. The effect causes the induced charge that would normally move from the cathode towards the anode to instead move laterally causing counts to shift away from a flux boundary. We show that the effect is not related to the physical boundary of the detector but rather related to the boundary of the irradiated area of the device. The dynamic polarization and charge steering effect can be attributed to the limited hole transport in the bulk material causing a buildup of a dynamic space-charge region under the irradiated area. The resulting lateral (perpendicular to the irradiation direction) electric field causes the lateral drift (steering) of the x-ray injected charge clouds. The static version of such lateral steering is often observed for charged structural defects in CdZnTe crystals. The studied 2D CdZnTe monolithic arrays were 16 16 pixel devices having 0.4 mm 0.4 mm area pixels on a 0.5 mm pitch and were fabricated using 8.7 mm 8.7 mm 3.0 mm CdZnTe single crystals grown by the high-pressure electro-dynamic gradient freeze technique. The devices were probe tested in a system consisting of a custom 16 16 pin probe head, 256 channel read-out electronics utilizing 8-channel fast bipolar ASIC chips, and a computer controlled 120 kVp x-ray source.

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Section: Introductionmentioning

confidence: 99%

Dynamic Lateral Polarization in CdZnTe Under High Flux X-Ray Irradiation

Soldner

Bale

Szeles

2007

IEEE Trans. Nucl. Sci.

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“…All images were acquired on a General Electric Triumph Trimodality (SPECT/PET/CT) pre-clinical scanner. This scanner uses CZT based SPECT technology [1] and the APD based PET technology with LYSO and LGSO crystals [2]. The mating of these systems in one scanner allows the investigation of the acquisition of PET and SPECT images with both modality radiotracers in the field of view (FOV) while eliminating any inherent image registration issues.…”

Section: Methodsmentioning

confidence: 99%

Mixed isotope effects: Image quality in multimodality PET/SPECT preclinical imaging

Tainter

Lokitz

Vascoe

et al. 2009

2009 IEEE Nuclear Science Symposium Conference Record (NSS/MIC)

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The recent availability of pre-clinical PET/SPECT/CT tri-modality systems provides an opportunity to image animals injected with mixed modality (PET/SPECT) isotopes. However, before these procedures can be truly useful, some understanding of the effect of different modality radiotracers on image quality and the resulting noise characteristics must be investigated. Our goal in this study was to characterize effects on image resolution that might arise in one modality because of the presence of another (different modality) isotope. A phantom, consisting of a set of side-by-side microcapillary tubes, were imaged on a trimodality (SPECT/PET/CT) pre-clinical scanner. Each tube was filled with a SPECT isotope and imaged while varying acquisition time, amount of activity, and distance between line sources. Images were evaluated to determine the visualization threshold at which objects became apparent in cross-sectional and MIP images (both that the objects were line sources and that the lines were two separate objects). These experiments were repeated in the presence of a PET isotope. After re-evaluating resolution, the signal to noise characteristics of the image as a whole were assessed and related to amounts of each isotope as well as total activity in the field of view. PET acquisition in the presence of SPECT isotopes was investigated using a contrast phantom with spheres filled with PET, SPECT, and mixed isotopes in backgrounds of mixed SPECT and PET isotopes. The noise properties of the background and spheres were measured as well as the visibility of the spheres. Finally, SPECT, PET, and CT images were acquired of a mouse after injection of both a PET and SPECT isotope. Acquisition of SPECT and PET images in the presence of different modality tracers (with careful considerations of the activity and acquisition parameters) seems feasible.

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“…The remaining deviations are mainly due to fluorescence escapes between adjacent pixels. Despite the fact that the pixel aperture has been more than halved, charge sharing plays only a minor role compared to the effects of optical cross-talk 3 . The Detector Response Functions of the indirect and direct conversion detector set-ups are shown in Figs.…”

Section: ) Electronic Read-outmentioning

confidence: 99%

“…SPECT prototypes in cardiology, scintimammography and small animal imaging have been presented, [1]- [3]. The authors report improved spectral resolution and underline the potential to perform dual-isotope imaging.…”

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confidence: 99%

Spectral and spatial resolution of semiconductor detectors in medical X- and gamma ray imaging

Heismann

Henseler

Niederloehner

et al. 2008

2008 IEEE Nuclear Science Symposium Conference Record

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Abstract-In X-and gamma ray based medical systems, detector performance is a key driver for diagnostic quality. Over the last years and decades, indirect conversion scintillator detectors have become the standard for many medical applications including X-ray Radiography, Computed Tomography and SPECT. Recently, direct conversion semiconductor detectors based on CdTe and CdZnTe (CZT) have come into focus, as they might offer improved or additional performance for specific applications. In this paper we use generic physical models to compare the spatial and spectral resolution of both detector types. The spatial resolution is quantified by the Modulation Transfer Function (MTF). We find that the direct conversion of quanta leads to an approximately sinc-like MTF. In comparison, the MTF of a pixelized scintillator detector shows a mid-frequency drop due to optical signal cross-talk.The spectral resolution of both detector types is described by the Detector Response Function (DRF). It yields the probability density D(E, E ) to measure an incoming quantum of energy E as the output energy E . As a general result we find that fluorescence X-ray cross-talk on one hand and charge sharing and optical cross-talk on the other hand significantly influence the DRF in both detector types. We compare the two detector types in a Computed Tomography application. For an integrating scintillator detector, a Poisson excess noise is observed and quantified. For a counting semiconductor detector, we describe the signficant low-energy shift in D(E, E ). The weighting functions of a two bin counting detctor are analyzed and compared to tube-based approaches. The results are summarized to show the trade-off between spectral and spatial resolution in medical imaging with direct conversion detectors.

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In Vivo Dual-Isotope SPECT Imaging with Improved Energy Resolution

Cited by 24 publications

References 3 publications

Dynamic Lateral Polarization in CdZnTe Under High Flux X-Ray Irradiation

Dynamic Lateral Polarization in CdZnTe Under High Flux X-Ray Irradiation

Mixed isotope effects: Image quality in multimodality PET/SPECT preclinical imaging

Spectral and spatial resolution of semiconductor detectors in medical X- and gamma ray imaging

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