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Title: The multi-module, multi-resolution system (M{sup 3}R): A novel small-animal SPECT system

Abstract

We have designed and built an inexpensive, high-resolution, tomographic imaging system, dubbed the multi-module, multi-resolution system, or M{sup 3}R. Slots machined into the system shielding allow for the interchange of pinhole plates, enabling the system to operate over a wide range of magnifications and with virtually any desired pinhole configuration. The flexibility of the system allows system optimization for specific imaging tasks and also allows for modifications necessary due to improved detectors, electronics, and knowledge of system construction (e.g., system sensitivity optimization). We provide an overview of M{sup 3}R, focusing primarily on system design and construction, aperture construction, and calibration methods. Reconstruction algorithms will be described and reconstructed images presented.

Authors:
; ; ; ;  [1];  [2];  [2];  [2]
  1. College of Optical Sciences, University of Arizona, 1630 E. University Blvd., Tucson, Arizona 85721 (United States)
  2. (United States)
Publication Date:
OSTI Identifier:
20951112
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 34; Journal Issue: 3; Other Information: DOI: 10.1118/1.2432071; (c) 2007 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; ALGORITHMS; APERTURES; CALIBRATION; FLEXIBILITY; IMAGE PROCESSING; IMAGES; OPTIMIZATION; SENSITIVITY; SHIELDING; SINGLE PHOTON EMISSION COMPUTED TOMOGRAPHY; SPATIAL RESOLUTION

Citation Formats

Hesterman, Jacob Y., Kupinski, Matthew A., Furenlid, Lars R., Wilson, Donald W., Barrett, Harrison H., College of Optical Sciences and Department of Radiology, University of Arizona, 1630 E. University Blvd., Tucson, Arizona 85721, Department of Radiology, University of Arizona, 1609 N. Warren Ave., Bldg 211, Tucson, Arizona 85724, and College of Optical Sciences and Department of Radiology, University of Arizona, 1630 E. University Blvd., Tucson, Arizona 85721. The multi-module, multi-resolution system (M{sup 3}R): A novel small-animal SPECT system. United States: N. p., 2007. Web. doi:10.1118/1.2432071.
Hesterman, Jacob Y., Kupinski, Matthew A., Furenlid, Lars R., Wilson, Donald W., Barrett, Harrison H., College of Optical Sciences and Department of Radiology, University of Arizona, 1630 E. University Blvd., Tucson, Arizona 85721, Department of Radiology, University of Arizona, 1609 N. Warren Ave., Bldg 211, Tucson, Arizona 85724, & College of Optical Sciences and Department of Radiology, University of Arizona, 1630 E. University Blvd., Tucson, Arizona 85721. The multi-module, multi-resolution system (M{sup 3}R): A novel small-animal SPECT system. United States. doi:10.1118/1.2432071.
Hesterman, Jacob Y., Kupinski, Matthew A., Furenlid, Lars R., Wilson, Donald W., Barrett, Harrison H., College of Optical Sciences and Department of Radiology, University of Arizona, 1630 E. University Blvd., Tucson, Arizona 85721, Department of Radiology, University of Arizona, 1609 N. Warren Ave., Bldg 211, Tucson, Arizona 85724, and College of Optical Sciences and Department of Radiology, University of Arizona, 1630 E. University Blvd., Tucson, Arizona 85721. Thu . "The multi-module, multi-resolution system (M{sup 3}R): A novel small-animal SPECT system". United States. doi:10.1118/1.2432071.
@article{osti_20951112,
title = {The multi-module, multi-resolution system (M{sup 3}R): A novel small-animal SPECT system},
author = {Hesterman, Jacob Y. and Kupinski, Matthew A. and Furenlid, Lars R. and Wilson, Donald W. and Barrett, Harrison H. and College of Optical Sciences and Department of Radiology, University of Arizona, 1630 E. University Blvd., Tucson, Arizona 85721 and Department of Radiology, University of Arizona, 1609 N. Warren Ave., Bldg 211, Tucson, Arizona 85724 and College of Optical Sciences and Department of Radiology, University of Arizona, 1630 E. University Blvd., Tucson, Arizona 85721},
abstractNote = {We have designed and built an inexpensive, high-resolution, tomographic imaging system, dubbed the multi-module, multi-resolution system, or M{sup 3}R. Slots machined into the system shielding allow for the interchange of pinhole plates, enabling the system to operate over a wide range of magnifications and with virtually any desired pinhole configuration. The flexibility of the system allows system optimization for specific imaging tasks and also allows for modifications necessary due to improved detectors, electronics, and knowledge of system construction (e.g., system sensitivity optimization). We provide an overview of M{sup 3}R, focusing primarily on system design and construction, aperture construction, and calibration methods. Reconstruction algorithms will be described and reconstructed images presented.},
doi = {10.1118/1.2432071},
journal = {Medical Physics},
number = 3,
volume = 34,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}
  • We propose a design for a high-resolution single-photon emission computed tomography (SPECT) system for in vivo {sup 125}I imaging in small animal using pixellated lithium-drifted silicon (Si(Li)) detectors. The proposed detectors are expected to have high interaction probability (>90%), good energy resolution (<15% FWHM), and good intrinsic spatial resolution ({approx}1 mm FWHM). The SPECT system will consist of a dual head detector geometry with the distance between the detectors ranging 30-50 mm to minimize the imaging distance between the mouse and the detectors. The detectors, each with an active area of 64 mm x 40 mm (64 x 40 arraymore » of 1 mm{sup 2} pixels and a 6 mm thick Si(Li) detector), will be mounted on a rotating gantry with an axial field-of-view of 64 mm. The detector signals will be read out by custom application-specific integrated circuits (ASICs). Using a high-resolution parallel-hole collimator, the expected spatial resolution is 1.6 mm FWHM at an imaging distance of 20 mm, and sensitivity is 6.7 cps/{micro}Ci. {sup 125}I is a readily available radioisotope with a long half-life of 59.4 days and it is commonly used to label biological compounds in molecular biology. Conventional gamma cameras are not optimized to detect the low emission energies (27 to 35 keV) of {sup 125}I. However, Si(Li) detector provides an ideal solution for detecting the low-energy emissions of {sup 125}I. In addition to presenting the design of the system, this paper presents a feasibility study of using Si(Li) detectors to detect the emissions of {sup 125}I.« less
  • Single photon emission computed tomography (SPECT) is an important technology for molecular imaging studies of small animals. In this arena, there is an increasing demand for high performance imaging systems that offer improved spatial resolution and detection efficiency. We have designed a multipinhole small animal imaging system based on position sensitive avalanche photodiode (PSAPD) detectors with the goal of submillimeter spatial resolution and high detection efficiency, which will allow us to minimize the radiation dose to the animal and to shorten the time needed for the imaging study. Our design will use 8x24 mm{sup 2} PSAPD detector modules coupled tomore » thallium-doped cesium iodide [CsI(Tl)] scintillators, which can achieve an intrinsic spatial resolution of 0.5 mm at 140 keV. These detectors will be arranged in rings of 24 modules each; the animal is positioned in the center of the 9 stationary detector rings which capture projection data from the animal with a cylindrical tungsten multipinhole collimator. The animal is supported on a bed which can be rocked about the central axis to increase angular sampling of the object. In contrast to conventional SPECT pinhole systems, in our design each pinhole views only a portion of the object. However, the ensemble of projection data from all of the multipinhole detectors provide angular sampling that is sufficient to reconstruct tomographic data from the object. The performance of this multipinhole PSAPD imaging system was simulated using a ray tracing program that models the appropriate point spread functions and then was compared against the performance of a dual-headed pinhole SPECT system. The detection efficiency of both systems was simulated and projection data of a hot rod phantom were generated and reconstructed to assess spatial resolution. Appropriate Poisson noise was added to the data to simulate an acquisition time of 15 min and an activity of 18.5 MBq distributed in the phantom. Both sets of data were reconstructed with an ML-EM reconstruction algorithm. In addition, the imaging performance of both systems was evaluated with a uniformity phantom and a realistic digital mouse phantom. Simulations show that our proposed system produces a spatial resolution of 0.8 mm and an average detection efficiency of 630 cps/MBq. In contrast, simulations of the dual-headed pinhole SPECT system produce a spatial resolution of 1.1 mm and an average detection efficiency of 53 cps/MBq. These results suggest that our novel design will achieve high spatial resolution and will improve the detection efficiency by more than an order of magnitude compared to a dual-headed pinhole SPECT system. We expect that this system can perform SPECT with submillimeter spatial resolution, high throughput, and low radiation dose suitable for in vivo imaging of small animals.« less
  • Purpose: In a previous work, output ratio (OR{sub det}) measurements were performed for the 800 MU/min CyberKnife{sup ®} at the Oscar Lambret Center (COL, France) using several commercially available detectors as well as using two passive dosimeters (EBT2 radiochromic film and micro-LiF TLD-700). The primary aim of the present work was to determine by Monte Carlo calculations the output factor in water (OF{sub MC,w}) and the k{sub Q{sub c{sub l{sub i{sub n,Q{sub m{sub s{sub r}{sup f{sub c}{sub l}{sub i}{sub n},f{sub m}{sub s}{sub r}}}}}}}}} correction factors. The secondary aim was to study the detector response in small beams using Monte Carlomore » simulation. Methods: The LINAC head of the CyberKnife{sup ®} was modeled using the PENELOPE Monte Carlo code system. The primary electron beam was modeled using a monoenergetic source with a radial gaussian distribution. The model was adjusted by comparisons between calculated and measured lateral profiles and tissue-phantom ratios obtained with the largest field. In addition, the PTW 60016 and 60017 diodes, PTW 60003 diamond, and micro-LiF were modeled. Output ratios with modeled detectors (OR{sub MC,det}) and OF{sub MC,w} were calculated and compared to measurements, in order to validate the model for smallest fields and to calculate k{sub Q{sub c{sub l{sub i{sub n,Q{sub m{sub s{sub r}{sup f{sub c}{sub l}{sub i}{sub n},f{sub m}{sub s}{sub r}}}}}}}}} correction factors, respectively. For the study of the influence of detector characteristics on their response in small beams; first, the impact of the atomic composition and the mass density of silicon, LiF, and diamond materials were investigated; second, the material, the volume averaging, and the coating effects of detecting material on the detector responses were estimated. Finally, the influence of the size of silicon chip on diode response was investigated. Results: Looking at measurement ratios (uncorrected output factors) compared to the OF{sub MC,w}, the PTW 60016, 60017 and Sun Nuclear EDGE diodes systematically over-responded (about +6% for the 5 mm field), whereas the PTW 31014 Pinpoint chamber systematically under-responded (about −12% for the 5 mm field). OR{sub det} measured with the SFD diode and PTW 60003 diamond detectors were in good agreement with OF{sub MC,w} except for the 5 mm field size (about −7.5% for the diamond and +3% for the SFD). A good agreement with OF{sub MC,w} was obtained with the EBT2 film and micro-LiF dosimeters (deviation less than 1.4% for all fields investigated). k{sub Q{sub c{sub l{sub i{sub n,Q{sub m{sub s{sub r}{sup f{sub c}{sub l}{sub i}{sub n},f{sub m}{sub s}{sub r}}}}}}}}} correction factors for several detectors used in this work have been calculated. The impact of atomic composition on the dosimetric response of detectors was found to be insignificant, unlike the mass density and size of the detecting material. Conclusions: The results obtained with the passive dosimeters showed that they can be used for small beam OF measurements without correction factors. The study of detector response showed that OR{sub det} is depending on the mass density, the volume averaging, and the coating effects of the detecting material. Each effect was quantified for the PTW 60016 and 60017 diodes, the micro-LiF, and the PTW 60003 diamond detectors. None of the active detectors used in this work can be recommended as a reference for small field dosimetry, but an improved diode detector with a smaller silicon chip coated with tissue-equivalent material is anticipated (by simulation) to be a reliable small field dosimetric detector in a nonequilibrium field.« less
  • The lack of anatomical information in SPECT and PET images is one of the major factors limiting the ability to localize and accurately quantify radionuclide uptake in small regions of interest. This problem could be resolved by using multi-modality scanners having the capability to acquire anatomical and functional images simultaneously. The feasibility of a novel detector suitable for measuring high-energy annihilation radiation in PET, medium-energy {gamma}-rays in SPECT and low-energy X-rays in transmission CT is demonstrated and its performance is evaluated for potential use in multi-modality PET/SPECT/CT imaging. The proposed detector consists of a thin CsI(Tl) scintillator sitting on topmore » of a deep GSO/LSO pair read out by an avalanche photodiode. The GSO/LOS pair provides depth-of-interaction information for 511 keV detection in PET, while the thin CsI(Tl) that is essentially transparent to annihilation radiation is used for detecting lower energy X- and {gamma}-rays. The detector performance is compared to that of an LSO/YSO phoswich. Although the implementation of the proposed GSO/LSO/CsI(Tl) detector raises special problems that increase complexity, it generally outperforms the LSO/YSO phoswich for simultaneous PET, SPECT and CT imaging.« less
  • The reactions of Nb(C{sub 5}H{sub 3}RR{prime}){sub 2}Cl{sub 2} with Red-Al followed by hydrolysis yield Nb(C{sub 5}H{sub 3}RR{prime}){sub 2}H{sub 3} (R=R{prime} = H, 1; R = H, R{prime} = SiMe{sub 3}, 2; R = R{prime} = SiMe{sub 3}, 3). These compounds react with Lewis acidic coinage cationic species, namely, [Cu(MeCN){sub 4}]PF{sub 6}, AgBF{sub 4}, and {open_quotes}Au(THT)PF{sub 6}{close_quotes}, prepared in situ from AuCl(THT) and TIPF{sub 6} in a 2 to 1 ratio to yield the adducts [(Nb(C{sub 5}H{sub 3}RR{prime}){sub 2}H{sub 3}){sub 2}M]{sup +} (M = Cu, R = R{prime} = H, 7; R = H, R{prime} = SiMe{sub 3}, 8; R =more » R{prime} = SiMe{sub 3}, 9; M = Ag, R = H, R{prime} = SiMe{sub 3}, 10; R = R{prime} = SiMe{sub 3}, 11; M = Au, R = R{prime} = H, 12; R = H, R{prime} = SiMe{sub 3}, 13; R = R{prime} = SiMe{sub 3}, 14). Like 1, but unlike the corresponding tantalum derivatives Ta(C{sub 5}H{sub 3}RR{prime}){sub 2}H{sub 3} (R = R{prime} = H, 4; R = H, R{prime} = SiMe{sub 3}, 5; R = R{prime} SiMe{sub 3}, 6), 2 and 3 show exchange couplings in their high-field {sup 1}H NMR spectra due to a hydride tunneling phenomenon. The magnitudes of exchange couplings are larger in the cases of 2 and 3 than in the case of 1 as a result of the decrease of electron density upon increasing the number of SiMe{sub 3} substituents on the Cp ring. The addition of a Lewis acidic cation results in the observation of an AB{sub 2} pattern for the hydrides at room temperature, which splits at low temperature into an ABC one in agreement with a fluxional behavior of the cation which binds to two hydrides of each niobium center.« less