H.W.A.M. de Jong

University Medical Center Utrecht, Utrecht, Provincie Utrecht, Netherlands

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Publications (27)28.85 Total impact

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    ABSTRACT: BACKGROUND AND PURPOSE:In CTP, an arterial input function is used for cerebral blood volume measurement. AIFs are often influenced by partial volume effects resulting in overestimated CBV. A venous output function is manually selected to correct for partial volume. This can introduce variability. Our goal was to develop a CTP protocol that enables AIF selection unaffected by partial volume.MATERIALS AND METHODS:First, the effects of partial volume on artery sizes/types including the MCA were estimated by using a CTP phantom with 9 protocols (section thicknesses of 1, 1.8, and 5 mm and image resolutions of 0.5, 1, and 1.5 mm). Next, these protocols were applied to clinical CTP studies from 6 patients. The influence of the partial volume effect was measured by comparison of the time-attenuation curves from different artery locations with reference veins.RESULTS:AIFs from MCAs were unaffected by partial volume effects when using high image resolution (1 mm) and medium section thickness (1.8 mm). For the clinical data, a total of 104 arteries and 60 veins was selected. The data confirmed that high image resolution and thin section thickness enable selection of MCAs for AIFs free of partial volume influences. In addition, we found that large veins were not insusceptible to partial volume effects relative to large arteries, questioning the use of veins for partial volume correction.CONCLUSIONS:A CTP protocol with 1.8-mm section thickness and 1-mm image resolution allows AIF selection unaffected by partial volume effects in MCAs.
    American Journal of Neuroradiology 01/2013; · 3.17 Impact Factor
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    ABSTRACT: For the radiographic evaluation of subchondral bone changes (sclerosis) in osteoarthritis (OA), bone density (BD) is commonly subjectively assessed. BD evaluation using plain digital radiography might be influenced by acquisition and post-processing (PP) settings. Objective of this study was to evaluate the effects of these settings on the measurement of BD using digital radiographs. A bone density standard (BDS) of hydroxyapatite (HA) mimicked a BD range of 1.0-5.75 g/cm(2). Digital radiographs were acquired with variation in acquisition settings, and with clinical and minimal PP. An aluminum step wedge served as an internal reference to express the gray values of the BDS in mm aluminum equivalents (mmAl). The relation (R(2)) between actual BD and BD normalized to the reference wedge was evaluated with linear regression analyses for radiographs with variations in PP and acquisition settings. Precision of BD measurement of the BDS was evaluated for application in clinical practice. The correlation between actual BD and BD normalized to the reference was improved by changing PP from clinical (R(2)=0.96) to minimal (R(2)=0.98). Higher tube voltage [kilovolt (kV)] improved the correlation further. Even for clinical PP, average standard deviation (SD) was 0.97 mmAl, much smaller than the change of 2.51 mmAl clinically observed in early OA, which implies the feasibility of BD measurements on digital radiographs. Changing PP and acquisition settings in clinical practice can have profound effect on outcome. If done with care, accurate BD measurement is feasible using plain digital radiography.
    Osteoarthritis and Cartilage 08/2011; 19(11):1343-8. · 4.26 Impact Factor
  • M Elschot, T C de Wit, H W A M de Jong
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    ABSTRACT: The high energy (511 keV) annihilation photons used in positron emission tomography (PET) imaging generally require a substantial amount of lead to protect personnel and the general public from ionizing radiation. A cost-effective design of the PET facility that ensures radiation does not exceed formal dose limits requires accurate estimation of the necessary PET shielding. The American Association of Physicists in Medicine (AAPM) Task Group 108 recently published broad beam transmission factors based on Monte Carlo calculations of 511 keV photons. In this work, an extension to the AAPM model is presented, based on Monte Carlo simulations including the effects of self-absorption on the photon energy spectrum. Monte Carlo calculations were performed using MCNPX. The photon energy spectrum after self-absorption was computed by simulating a normal 18FDG activity distribution in an anthropomorphic phantom. This spectrum was used to calculate the dose rate transmission factors for various wall thicknesses of lead, concrete, and iron. The method was validated by measurement and corresponding simulation of the transmission factors of an 18FDG source in air and in PMMA. Furthermore, a method to generate 3D area dose rate maps of PET facilities incorporating the calculated transmission tables is presented and applied to several shielding situations. The calculated self-absorption correction factor and the broad beam transmission factors resulting from Monte Carlo simulations of a monoenergetic point source emitting 511 keV photons were in excellent agreement with the results of the AAPM publication (0.66 vs 0.64 and R2 = 0.999, respectively). However, when all radiation physics, i.e., also the effect of self-absorption on the photon energy spectrum, is included in the Monte Carlo calculations, a substantial reduction in required shielding material was found. For example, including all radiation physics leads to 13.3 mm of lead required to obtain a typical transmission factor of 0.1, instead of 16.0 mm of lead when the AAPM data including only the self-absorption correction factor are used. These findings were confirmed by the experimental measurements. The transmission factors produced in this work can be applied in the same manner as those estimated by AAPM to allow for a cost-effective design of PET and PET/CT facilities without violating radiation safety regulations. Taking into account the effect of self-absorption on the photon energy spectrum results in more accurate and cost-effective shielding requirement estimations.
    Medical Physics 06/2010; 37(6):2999-3007. · 2.91 Impact Factor
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    ABSTRACT: To assess the accuracy of a scout dose of holmium-166 poly(L-lactic acid) microspheres ((166)Ho-PLLA-MS) in predicting the distribution of a treatment dose of (166)Ho-PLLA-MS, using single photon emission tomography (SPECT). A scout dose (60 mg) was injected into the hepatic artery of five pigs and SPECT acquired. Subsequently, a 'treatment dose' was administered (540 mg) and SPECT, computed tomography (CT) and magnetic resonance imaging (MRI) of the total dose performed. The two SPECT images of each animal were compared. To validate quantitative SPECT an ex vivo liver was instilled with (166)Ho-PLLA-MS and SPECT acquired. The liver was cut into slices and planar images were acquired, which were registered to the SPECT image. Qualitatively, the scout dose and total dose images were similar, except in one animal because of catheter displacement. Quantitative analysis, feasible in two animals, tended to confirm this similarity (r(2) = 0.34); in the other animal the relation was significantly better (r(2) = 0.66). The relation between the SPECT and planar images acquired from the ex vivo liver was strong (r(2) = 0.90). In the porcine model a scout dose of (166)Ho-PLLA-MS can accurately predict the biodistribution of a treatment dose. Quantitative (166)Ho SPECT was validated for clinical application.
    European Radiology 09/2009; 20(4):862-9. · 4.34 Impact Factor
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    ABSTRACT: The High Resolution Research Tomograph (HRRT) is a dedicated 3D brain positron emission tomograph (PET), designed for a resolution of 3 mm or less. Recent improvements in image reconstruction strategies, such as the implementation of ordinary Poisson OSEM, improved the quantitative accuracy of HRRT PET. Further improvement of its accuracy might be expected using a new randoms estimation method based on coincidence histograms. The purpose of the present study was therefore to further evaluate the accuracy of HRRT studies using these new reconstruction methods. Moreover, data will be compared with those measured on a clinical HR+ PET scanner (Siemens), which has been used most frequently for human brain applications so far. To this end, a number of phantom experiment using, for example, NEMA scatter and attenuation, homogeneous (linearity and uniformity) and anthropomorphic brain phantoms, have been performed on both scanners. When using the new randoms estimation method, HRRT experiments showed a remnant scatter fraction <5%, uniformity <5% and linearity <3% up to 136 MBq. These results were similar of better than those obtained with the HR + HRRT brain phantom studies provided accurate results within 10 and 15% for grey and white matter areas, respectively, for high statistics (>1800 s) scans only. Large under- and overestimations of 20 and 50% in grey and white matter areas, respectively, were observed in case of short acquisition frames (10-30 s). As short acquisition frames of 10-30 s are normally applied in dynamic brain studies, it is concluded that further refinement of image reconstruction strategies [Boellaard, R, et. al., 2004] is required to obtain more accurate results, which are comparable with those of the HR+, for dynamic HRRT PET brain studies.
    Nuclear Science Symposium Conference Record, 2006. IEEE; 12/2006
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    ABSTRACT: In this study the imaging characteristics influencing the quantitative accuracy of <sup>68</sup>Ga, <sup>124</sup>I and <sup>89</sup>Zr were determined and compared to those of <sup>18</sup>F using a 3D high resolution PET (high resolution research tomograph, HRRT) scanner. Although there were large discrepancies found in the sensitivity of these isotopes, which can be explained by their positron abundancy, none of the assessed imaging characteristic prevents the isotopes for usage in (high resolution) quantitative PET imaging. Care has to be taken, however, that accurate correction methods are used for dead time, background and scatter, and partial volume.
    Nuclear Science Symposium Conference Record, 2005 IEEE; 11/2005
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    ABSTRACT: The high resolution research tomograph (HRRT) is one of the most complex existing positron emission tomographs: it is the only human size scanner capable of decoding the depth of the γ-ray interaction in the crystal, using a lutetium LSO/LYSO phoswich detector arrangement. In this study we determined basic scanner hardware characteristics, such as scanner data acquisition stability, and their variability across eleven centres. In addition a subset of the NEMA NU-2001 standards measurements was performed. We found (i) significant variability in the DOI decoding results between centres, (ii) a trend toward an increasing number of detected true coincident events as a function of elapsed time from scanner calibration likely due to a shifting energy spectrum, (iii) a count-rate dependent layer identification, (iv) scatter fraction ranging from ∼ 42% to 54% where the variability was partly related to the shifting of the energy spectrum, (v) sensitivity ranging from ∼5.5% to 6.5% across centres, (vi) resolution of ∼(2.5 mm)<sup>3</sup>, fairly consistent across centres, (vii) image quality which is very comparable to other scanners.
    Nuclear Science Symposium Conference Record, 2005 IEEE; 11/2005
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    ABSTRACT: The high resolution research tomograph (HRRT) is a brain-dedicated scanner manufactured by CPS Innovations using LSO panel detectors. Transmission is measured using a <sup>137</sup>Cs point source, which is moved axially and rotated to cover the FOV. The point source is collimated axially and transaxially to illuminate only a few planes on the heads opposite to the point source location. Pseudo-coincidence events are generated using a given crystal and the source location. The transmission system was previously validated for cold transmissions. For post-injection (hot) transmission, it is not possible to eliminate the emission contamination by raising the lower energy threshold. Since real mock scan is unpractical on HRRT and fake mock scan requires additional data, we developed a new technique to simultaneously measure the transmission and the mock scans. The technique uses a virtual source, axially located at a distance equal to the half of the axial FOV and illuminates a fan separated from the real transmission fan. We validated the shifted-mock scan technique by comparing it to real mock scan one with a <sup>68</sup>Ge phantom and examined its effectiveness with a hot 20 cm phantom filled with <sup>18</sup>F decaying over several half-lives. Local residual bias in μ-map was attributed to transmission scatter and corrected by using partial segmentation in the MAP-TR algorithm, μ-maps from cold and hot transmissions were compared on several clinical patients and a Hoffman brain phantom for which their influence on emission quantification was studied.
    Nuclear Science Symposium Conference Record, 2004 IEEE; 11/2004
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    ABSTRACT: The high resolution research tomograph (HRRT) is the first PET scanner with depth of interaction (DOI) capability. Presently three different versions have been developed: one equipped with two 7.5 mm thick crystal layers (HRRT-DC), the second with only a single 7.5 mm crystal layer (HRRT-S) and the latest HRRT with two 10 mm thick crystal layers (HRRT-D). In this study the performance of the new HRRT-D was assessed and compared with the other two HRRTs. The characteristics were measured according to the NEMA NU2 standards. Similar scatter fractions between all three scanners were observed. NEC rates of the HRRT-D were about 8 and 3 times higher than those of HRRT-S and HRRT-DC, respectively. However, spatial resolution of the new HRRT-D is somewhat lower than that of HRRT-DC and HRRT-S. Use of thicker crystals in the new HRRT-D improved the sensitivity and NECR performance significantly at the cost of only a small deterioration of the spatial resolution compared with the other HRRT designs.
    Nuclear Science Symposium Conference Record, 2004 IEEE; 11/2004
  • H.W.A.M. de Jong, R. Boellaard, C. Michel, A.A. Lammertsma
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    ABSTRACT: The high resolution research tomograph (HRRT) is the first PET scanner with depth of interaction (DOT) capability. Presently three different versions have been developed: one equipped with two 7.5 mm thick crystal layers (HRRT-DC), the second with only a single 7.5 mm crystal layer (HRRT-S) and the latest HRRT with two 10 mm thick crystal layers (HRRT-D). In this study the performance of the new HRRT-D was assessed and compared with the other two HRRTs. The characteristics were measured according to the NEMA NU2 standards. Similar scatter fractions between all three scanners were observed. NEC rates of the HRRT-D were about 8 and 3 times higher than those of HRRT-S and HRRT-DC, respectively. However, spatial resolution of the new HRRT-D is somewhat lower than that of HRRT-DC and HRRT-S. Use of thicker crystals in the new HRRT-D improved the sensitivity and NECR performance significantly at the cost of only a small deterioration of the spatial resolution compared with the other HRRT designs.
    Nuclear Science Symposium Conference Record, 2004 IEEE; 11/2004
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    ABSTRACT: The count rate performance of the single LSO crystal layer high-resolution research tomograph (HRRT-S) PET scanner is limited by the processing speed of its electronics. Therefore, the feasibility of using an in-field-of-view (in-FOV) shield to improve the noise equivalent count rates (NECR) for small animal brain studies was investigated. The in-FOV shield consists of a lead tube of 12 cm length, 6 cm inner diameter and 9 mm wall thickness. It is large enough to shield the activity in the body of a rat or mouse. First, the effect of this shield on NECR was studied. Secondly, a number of experiments were performed to assess the effects of the shield on the accuracy of transmission scan data and, next, on reconstructed activity distribution in the brain. For activities below 150 MBq NECR improved only by 5-10%. For higher activities NECR maxima of 1.2E4 cps at 200 MBq and 2.2E4 cps at 370 MBq were found without and with shield, respectively. Listmode data taken without shield, however, were corrupted for activities above 75 MBq due to data overrun problems (time tag losses) of the electronics. When the shield was used data overrun was avoided up to activities of 150 MBq. For the unshielded part of the phantom, transmission scan data were the same with and without shield. The estimated scatter contribution was approximately 8.5% without and 5.5% with shield. Reconstructed emission data showed a difference up to 5% in the unshielded part of the phantom at 5 mm or more from the edge of the shielding. Of this 5% about 3% results from the difference in the uncorrected scatter contribution. In conclusion, an in-FOV shield can be used successfully in an HRRT PET scanner to improve NECR and accuracy of small animal brain studies. The latter is especially important when high activities are required for tracers with low brain uptake or when multiple animals are scanned simultaneously.
    Physics in Medicine and Biology 01/2004; 48(23):N335-42. · 2.70 Impact Factor
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    ABSTRACT: The High Resolution Research Tomograph PET scanner is equipped with a moving Cs-137 transmission point source emitting 662 keV single photons. During postinjection transmission imaging 511 keV emission photons can be detected in the transmission window leading to gross underestimation of the reconstructed mu-value. Using cylindrical phantoms, methods to compensate for this emission contamination (EC) were investigated including histogram-based scaling and segmentation with varying transmission window settings. Furthermore, the effects of subtracting a uniform or nonuniform EC estimation prior to transmission reconstruction were quantified. In conclusion, EC during HRRT transmission scans can lead to gross underestimation of mu-values, and the most accurate way to compensate for this is to combine nonuniform EC subtraction with image segmentation.
    Nuclear Science Symposium Conference Record, 2003 IEEE; 11/2003
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    ABSTRACT: The high resolution research tomograph (HRRT) is a 3-D PET scanner designed for human brain and small animal imaging. The HRRT consists of eight panel detector heads that are separated by gaps of 17 mm resulting in gaps in the sinogram. Furthermore, gaps can result from detector-block failure. To prevent artifacts in the reconstruction when using Fourier rebinning (FORE), filling the data gaps is required. The purpose of this study was to evaluate the accuracy of three gap filling methods: a) bilinear interpolation of sinogram data; b) a model-based method in which an intermediate volume is reconstructed [2-D ordered subsets expectation maximization (2-D OSEM)] based on direct planes only, after which this image is forward projected to fill the gaps; c) an improved model-based method in which gaps are first filled using interpolation, then reconstructed using FORE + 2-D OSEM and forward projected. The improved model-based method outperforms interpolation, but requires more computation time.
    IEEE Transactions on Nuclear Science 11/2003; · 1.22 Impact Factor
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    ABSTRACT: The purpose of this study was to determine the performance of a single lutetium oxy-orthosilicate (LSO) crystal layer High Resolution Research Tomograph (HRRT) positron emission tomography (PET) scanner. The HRRT is a high resolution PET scanner designed for human brain and small animal imaging. The scanner consists of eight panel detectors, which have one layer of 2.1 x 2.1 x 7.5 mm thick LSO crystals. Several phantom studies were performed to determine scanner characteristics, such as resolution, scatter fraction, count rate and noise equivalent count rates (NECR). NECR curves were measured according to both NEMA NU2-1994 and NU2-2001 for three different energy windows, i.e. lower level discriminators (lld) of 350, 400 and 450 keV and an upper level discriminator (uld) of 650 keV. Accuracy of scatter and single photon attenuation corrections was evaluated according to NU2-1994. Data were acquired using a ring difference of 67 and a span of 9. Reconstructions were performed using FORE + 2D FBP or OSEM. Transaxial resolution varied from 2.7 to 2.9 mm FWHM between I and 10 cm off centre locations, and axial resolution varied from 3.2 to 4.4 mm FWHM. Scatter fractions (NU2-1994) equalled 0.31, 0.42 and 0.54 for lld of 450, 400 and 350 keV, respectively. NECR data were highest for an lid of 400 keV and showed a maximum of 46 kcps at 38 kBq cm(-3). Lower NECR values were observed according to NU2-2001, but were still optimal for an lld of 400 keV. After scatter and attenuation corrections, pixel values within water, air and teflon inserts of the NU2-1994 phantom were 14, 4 and 35% of the background activity, respectively. The single layer LSO HRRT scanner shows excellent spatial resolution, making it suitable for small animal studies. The low count rate performance, due to the small amount of LSO, prohibits studies of the human brain, but is sufficient for studies in small laboratory animals.
    Physics in Medicine and Biology 03/2003; 48(4):429-48. · 2.70 Impact Factor
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    ABSTRACT: Combined acquisition of transmission and emission data in SPECT can be used for accurate correction of non-uniform photon attenuation. However, down-scatter from a higher energy isotope (e.g. Tc-99m, 140 keV) contaminates lower energy transmission data (e.g. Gd-153, 100 keV), resulting in under-estimation of reconstructed attenuation coefficients. Correction for down-scatter by subtraction of down-scatter projections (for example collected in a separate scatter window) is often not very accurate and can increase noise in the attenuation-maps. Therefore, a new correction method has been developed, that is robust to noise, uses accurate scatter modeling and does not require additional energy windows. Statistical reconstruction of the attenuation-map is used, that allows adequate incorporation of model based scatter estimates. The emission images are reconstructed using a fully 3D maximum likelihood algorithm employing Monte Carlo based scatter modeling, attenuation modeling and detector blurring modeling. The correction scheme is as follows: Initially, an approximate attenuation-map is reconstructed using down-scatter contaminated transmission data (Step 1). An emission map is reconstructed based on the approximate attenuation map (Step 2). Based on this approximate Tc-99m reconstruction and the approximate attenuation-map, down-scatter in the Gd-153 window is simulated using an accelerated Monte Carlo simulator (Step 3). This down-scatter estimate is used during reconstruction of a corrected attenuation-map (Step 4). Based on the corrected attenuation-map an improved Tc-99m image is reconstructed (Step 5). Steps 3-5 are repeated to improve the down-scatter correction. The method was tested for simulated projection data of the MCAT thorax phantom with clinically realistic noise levels, assuming a dual-head camera equipped with moving transmission line sources. Typically, four cycles through the correction scheme were required to reduce errors in the attenuation coefficients from about 50% to only a few percent In addition, artifacts due to the corrupted attenuation maps on the Tc-99m emission reconstruction completely disappeared.
    Nuclear Science Symposium Conference Record, 2002 IEEE; 12/2002
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    ABSTRACT: In simultaneous technetium-99m/thallium-201 dual-isotope (DI) single-photon emission tomography (SPET), down-scatter of (99m)Tc photons contaminates the (201)Tl image, which leads to a decrease in lesion contrast and loss of quantitative accuracy. Correction for down-scatter can be achieved by first reconstructing the (99m)Tc activity distribution. Subsequently, the (99m)Tc down-scatter in the (201)Tl photopeak window is simulated and used for correction during iterative reconstruction of the (201)Tl image. In this work, the down-scatter projections are calculated using a dedicated Monte Carlo simulator which is able to efficiently model the detection of lead X-rays from the collimator. An anthropomorphic torso phantom with a cardiac insert with and without cold lesions was used for evaluation of the proposed method. Excellent agreement in lesion contrast and quantitative accuracy was found between the down-scatter corrected DI-SPET (201)Tl image and the virgin (i.e. separately acquired) (201)Tl image, in particular when the effects of lead X-rays were included. Compensation for the noise added by down-scatter to the (201)Tl image can be achieved by using a 15% lower dose of (99m)Tc, a 15% increase in scan time and a 12% increase in (201)Tl dose. In conclusion, the Monte Carlo-based down-scatter correction recovers lesion contrast and quantitative accuracy in DI-SPET (201)Tl images almost perfectly. In addition, degradations due to the added noise of down-scatter in simultaneous DI-SPET can be prevented by slight adaptations to the data acquisition protocol.
    European journal of nuclear medicine and molecular imaging 09/2002; 29(8):1063-71. · 5.11 Impact Factor
  • M. Gieles, H.W.A.M. de Jong, F.J. Beekman
    01/2002;
  • H.W.A.M. de Jong, Wen-Tung Wang, E.C. Frey, F.J. Beekman
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    ABSTRACT: A major image degrading factor in simultaneous dual isotope (DI) SPECT or simultaneous emission-transmission (ECT-TCT) imaging, is the detection of photons emitted by the higher energy isotope in the energy window used for imaging the lower energy isotope. In Tc-99m/Tl-201 DI SPECT typically tens of percents of the total down-scatter is caused by lead X-rays. In Tc-99m/Gd-153 ECT TCT, a comparable fraction of the down-scatter originates from Tc-99m photons which only partly deposit their energy in the detector crystal. When the spatial distribution of the isotope causing down-scatter is known, projections can be estimated using photon transport calculations. Such projections can be used for down-scatter correction. In this paper we extend a previously proposed efficient down-scatter simulation method, by incorporating into the scatter model the interactions of photons with the detector crystal and collimator lead. To this end, point spread function tables including crystal and lead interactions are simulated. Subsequently, photons are traced through the patient body until their last scatter position, and the pre-calculated responses are used to project the photons onto the detector plane, taking photon attenuation into account. The approach is evaluated by comparing calculated Tc-99m down-scatter projections with measured projections. The inclusion of the crystal and lead interactions tremendously increases accuracy of the simulations. Calculating 60 down-scatter projections of an extended distribution on a 64 × 64 × 64 grid takes about 3 minutes on a PC with two 1.2 GHz processors. We conclude that accurate simulation of down-scatter is now possible including all relevant effects of non-uniform density and photon interactions with the crystal and collimator lead.
    Nuclear Science Symposium Conference Record, 2001 IEEE; 12/2001
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    H.W.A.M. de Jong, E.T.P. Slijpen, F.J. Beekman
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    ABSTRACT: Monte Carlo (MC) simulation is an established tool to calculate photon transport through tissue in Emission Computed Tomography (ECT). Since the first appearance of MC a large variety of variance reduction techniques (VRT) have been introduced to speed up these notoriously slow simulations. One example of a very effective and established VRT is known as forced detection (FD). In standard FD the path from the photon's scatter position to the camera is chosen stochastically from the appropriate probability density function (PDF), modeling the distance-dependent detector response. In order to speed up MC the authors propose a convolution-based FD (CFD) which involves replacing the sampling of the PDF by a convolution with a kernel which depends on the position of the scatter event. The authors validated CFD for parallel-hole Single Photon Emission Computed Tomography (SPECT) using a digital thorax phantom. Comparison of projections estimated with CFD and standard FD shows that both estimates converge to practically identical projections (maximum bias 0.9% of peak projection value), despite the slightly different photon paths used in CFD and standard FD. Projections generated with CFD converge, however, to a noise-free projection up to one or two orders of magnitude faster, which is extremely useful in many applications such as model-based image reconstruction
    IEEE Transactions on Nuclear Science 03/2001; · 1.22 Impact Factor
  • M. Gieles, H.W.A.M. de Jong, F.J. Beekman
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    ABSTRACT: The aim of the present work is to accelerate Monte Carlo (MC) simulations of micro-pinhole SPECT projections. To this end, forced detection (FD), a commonly used acceleration technique, is replaced by a kernel-based forced detection (KFD) step. In KFD, instead of tracing individual photons from the source or last scatter position to the detector, a position dependent point spread function (PSF) modeling a channel edge pinhole aperture is projected. The speed-up and accuracy achieved by using KFD were validated by means of digital phantoms. MC simulations with FD and with KFD converge to almost identical projections. However, KFD converges to an equal noise level in the projections one up to four orders of magnitude faster than FD, depending on the number of photons simulated
    Nuclear Science Symposium Conference Record, 2001 IEEE; 02/2001

Publication Stats

173 Citations
28.85 Total Impact Points

Institutions

  • 1999–2013
    • University Medical Center Utrecht
      • • Department of Radiology
      • • Image Sciences Institute
      • • Department of Image Processing
      Utrecht, Provincie Utrecht, Netherlands
  • 2003–2005
    • VU University Medical Center
      • Department of Nuclear Medicine and PET Research
      Amsterdamo, North Holland, Netherlands