P.J. La Riviere

The University of Chicago Medical Center, Chicago, Illinois, United States

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Publications (110)123.5 Total impact

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    ABSTRACT: Europium-doped yttrium oxide (Y2O3:Eu) has garnered considerable interest recently for its use as a highly efficient, red phosphor in a variety of lighting applications that include fluorescent lamps, plasma, and field emission display panels, light emitting diodes (LEDs), and lasers. In the present work, we describe the development of Y2O3:Eu nanoparticles for a very different application: in situ, in vivo x-ray dosimetry. Spectroscopic analyses of these nanoparticles during x-ray irradiation reveal surprisingly bright and stable radioluminescence at near-infrared wavelengths, with markedly linear response to changes in x-ray flux and energy. Monte Carlo modeling of incident flux and broadband, wide-field imaging of mouse phantoms bearing both Y2O3:Eu nanoparticles and calibrated LEDs of similar spectral emission demonstrated significant transmission of radioluminescence, in agreement with spectroscopic studies; with approximately 15 visible photons being generated for every x-ray photon incident. Unlike the dosimeters currently employed in clinical practice, these nanodosimeters can sample both dose and dose rate rapidly enough as to provide real-time feedback for x-ray based external beam radiotherapy (EBRT). The technique's use of remote sensing and absence of supporting structures enable perturbation-free dosing of the targeted region and complete sampling from any direction. With the conjugation of pathology-targeting ligands onto their surfaces, these nanodosimeters offer a potential paradigm shift in the real-time monitoring and modulation of delivered dose in the EBRT of cancer in situ.
    Applied Physics Letters 11/2014; 105(20):203110. · 3.52 Impact Factor
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    David Rigie, Patrick La Riviere
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    ABSTRACT: We explore the use of the recently proposed "total nuclear variation" (TNV) as a regularizer for reconstructing multi-channel, spectral CT images. This convex penalty is a natural extension of the total variation (TV) to vector-valued images and has the advantage of encouraging common edge locations and a shared gradient direction among image channels. We show how it can be incorporated into a general, data-constrained reconstruction framework and derive update equations based on the first-order, primal-dual algorithm of Chambolle and Pock. Early simulation studies based on the numerical XCAT phantom indicate that the inter-channel coupling introduced by the TNV leads to better preservation of image features at high levels of regularization, compared to independent, channel-by-channel TV reconstructions.
    09/2014;
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    ABSTRACT: We integrate a small and portable medical x-ray device with mechanical testing equipment to enable in-situ, non-invasive measurements of a granular material's response to mechanical loading. We employ an orthopedic C-arm as the x-ray source and detector to image samples mounted in the materials tester. We discuss the design of a custom rotation stage, which allows for sample rotation and tomographic reconstruction under applied compressive stress. We then discuss the calibration of the system for 3d computed tomography, as well as the subsequent image reconstruction process. Using this system to reconstruct packings of 3d-printed particles, we resolve packing features with 0.52 mm resolution in a (60 mm)$^3$ field of view. By analyzing the performance bounds of the system, we demonstrate that the reconstructions exhibit only moderate noise.
    Review of Scientific Instruments 06/2014; 85(8). · 1.58 Impact Factor
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    ABSTRACT: There is a strong need for an accurate and easily available technique for myocardial blood flow (MBF) estimation to aid in the diagnosis and treatment of coronary artery disease (CAD). Dynamic CT would provide a quick and widely available technique to do so. However, its biggest limitation is the dose imparted to the patient. We are exploring techniques to reduce the patient dose by either reducing the tube current or by reducing the number of temporal frames in the dynamic CT sequence. Both of these dose reduction techniques result in very noisy data. In order to extract the myocardial blood flow information from the noisy sinograms, we have been looking at several data-domain smoothing techniques. In our previous work,1 we explored the sinogram restoration technique in both the spatial and temporal domain. In this work, we explore the use of Karhunen-Loeve (KL) transform to provide temporal smoothing in the sinogram domain. This technique has been applied previously to dynamic image sequences in PET.2, 3 We find that the cluster-based KL transform method yields noticeable improvement in the smoothness of time attenuation curves (TAC). We make use of a quantitative blood flow model to estimate MBF from these TACs and determine which smoothing method provides the most accurate MBF estimates.
    SPIE Medical Imaging; 03/2014
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    ABSTRACT: Contrast enhancement on cardiac CT provides valuable information about myocardial perfusion and methods have been proposed to assess perfusion with static and dynamic acquisitions. There is a lack of knowledge and consensus on the appropriate approach to ensure 1) sufficient diagnostic accuracy for clinical decisions and 2) low radiation doses for patient safety. This work developed a thorough dynamic CT simulation and several accepted blood flow estimation techniques to evaluate the performance of perfusion assessment across a range of acquisition and estimation scenarios. Cardiac CT acquisitions were simulated for a range of flow states (Flow = 0.5, 1, 2, 3 ml/g/min, cardiac output = 3,5,8 L/min). CT acquisitions were simulated with a validated CT simulator incorporating polyenergetic data acquisition and realistic x-ray flux levels for dynamic acquisitions with a range of scenarios including 1, 2, 3 sec sampling for 30 sec with 25, 70, 140 mAs. Images were generated using conventional image reconstruction with additional image-based beam hardening correction to account for iodine content. Time attenuation curves were extracted for multiple regions around the myocardium and used to estimate flow. In total, 2,700 independent realizations of dynamic sequences were generated and multiple MBF estimation methods were applied to each of these. Evaluation of quantitative kinetic modeling yielded blood flow estimates with an root mean square error (RMSE) of ∼0.6 ml/g/min averaged across multiple scenarios. Semi-quantitative modeling and qualitative static imaging resulted in significantly more error (RMSE = ∼1.2 and ∼1.2 ml/min/g respectively). For quantitative methods, dose reduction through reduced temporal sampling or reduced tube current had comparable impact on the MBF estimate fidelity. On average, half dose acquisitions increased the RMSE of estimates by only 18% suggesting that substantial dose reductions can be employed in the context of quantitative myocardial blood flow estimation. In conclusion, quantitative model-based dynamic cardiac CT perfusion assessment is capable of accurately estimating MBF across a range of cardiac outputs and tissue perfusion states, outperforms comparable static perfusion estimates, and is relatively robust to noise and temporal subsampling.
    Proceedings - Society of Photo-Optical Instrumentation Engineers 03/2014; 9033:903303.
  • David Rigie, Patrick J. La Riviere
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    ABSTRACT: In this work we propose a fast, model-based restoration scheme for noisy or undersampled spec- tral CT data and demonstrate its potential utility with two simulation studies. First, we show how one can denoise photon counting CT images, post- reconstruction, by using a spectrally averaged im- age formed from all detected photons as a high SNR prior. Next, we consider a slow slew-rate kV switch- ing scheme, where sparse sinograms are obtained at peak voltages of 80 and 140 kVp. We show how the missing views can be restored by using a spectrally av- eraged, composite sinogram containing all of the views as a fully sampled prior. We have chosen these ex- amples to demonstrate the versatility of the proposed approach and because they have been discussed in the literature before3,6 but we hope to convey that it may be applicable to a fairly general class of spectral CT systems. Comparisons to several sparsity-exploiting, iterative reconstructions are provided for reference.
    SPIE Medical Imaging; 03/2014
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    ABSTRACT: Myocardial blood flow (MBF) can be estimated from dynamic contrast enhanced (DCE) cardiac CT acquisitions, leading to quantitative assessment of regional perfusion. The need for low radiation dose and the lack of consensus on MBF estimation methods motivates this study to refine the selection of acquisition protocols and models for CT-derived MBF. DCE cardiac CT acquisitions were simulated for a range of flow states (MBF = 0.5, 1, 2, 3 ml (min g)(-1), cardiac output = 3, 5, 8 L min(-1)). Patient kinetics were generated by a mathematical model of iodine exchange incorporating numerous physiological features including heterogenenous microvascular flow, permeability and capillary contrast gradients. CT acquisitions were simulated for multiple realizations of realistic x-ray flux levels. CT acquisitions that reduce radiation exposure were implemented by varying both temporal sampling (1, 2, and 3 s sampling intervals) and tube currents (140, 70, and 25 mAs). For all acquisitions, we compared three quantitative MBF estimation methods (two-compartment model, an axially-distributed model, and the adiabatic approximation to the tissue homogeneous model) and a qualitative slope-based method. In total, over 11 000 time attenuation curves were used to evaluate MBF estimation in multiple patient and imaging scenarios. After iodine-based beam hardening correction, the slope method consistently underestimated flow by on average 47.5% and the quantitative models provided estimates with less than 6.5% average bias and increasing variance with increasing dose reductions. The three quantitative models performed equally well, offering estimates with essentially identical root mean squared error (RMSE) for matched acquisitions. MBF estimates using the qualitative slope method were inferior in terms of bias and RMSE compared to the quantitative methods. MBF estimate error was equal at matched dose reductions for all quantitative methods and range of techniques evaluated. This suggests that there is no particular advantage between quantitative estimation methods nor to performing dose reduction via tube current reduction compared to temporal sampling reduction. These data are important for optimizing implementation of cardiac dynamic CT in clinical practice and in prospective CT MBF trials.
    Physics in Medicine and Biology 03/2014; 59(7):1533-1556. · 2.92 Impact Factor
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    ABSTRACT: Purpose: X-ray fluorescence computed tomography (XFCT) is an emerging imaging modality that maps the three-dimensional distribution of elements, generally metals, in ex vivo specimens and potentially in living animals and humans. At present, it is generally performed at synchrotrons, taking advantage of the high flux of monochromatic x rays, but recent work has demonstrated the feasibility of using laboratory-based x-ray tube sources. In this paper, the authors report the development and experimental implementation of two novel imaging geometries for mapping of trace metals in biological samples with ∼50-500 μm spatial resolution.Methods: One of the new imaging approaches involves illuminating and scanning a single slice of the object and imaging each slice's x-ray fluorescent emissions using a position-sensitive detector and a pinhole collimator. The other involves illuminating a single line through the object and imaging the emissions using a position-sensitive detector and a slit collimator. They have implemented both of these using synchrotron radiation at the Advanced Photon Source.Results: The authors show that it is possible to achieve 250 eV energy resolution using an electron multiplying CCD operating in a quasiphoton-counting mode. Doing so allowed them to generate elemental images using both of the novel geometries for imaging of phantoms and, for the second geometry, an osmium-stained zebrafish.Conclusions: The authors have demonstrated the feasibility of these two novel approaches to XFCT imaging. While they use synchrotron radiation in this demonstration, the geometries could readily be translated to laboratory systems based on tube sources.
    Medical Physics 06/2013; 40(6):061903. · 3.01 Impact Factor
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    Adam Petschke, Patrick J La Rivière
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    ABSTRACT: We demonstrate the use of task-based image-quality metrics to compare various photoacoustic image-reconstruction algorithms, including a method based on the pseudoinverse of the system matrix, simple backprojection, filtered backprojection, and a method based on the Fourier transform. We use a three-dimensional forward model with a linear transducer array to simulate a photoacoustic imaging system. The reconstructed images correspond with two-dimensional slices of the object and are 128×128 pixels. In order to compare the algorithms, we use channelized Hotelling observers that predict the detection ability of human observers. We use two sets of channels: constant Q and difference of Gaussian spatial frequency channels. We look at three tasks, identification of a point source in a uniform background, identification of a 0.5-mm cube in a uniform background, and identification of a point source in a lumpy background. For the lumpy background task, which is the most realistic of the tasks, the method based on the pseudoinverse performs best according to both sets of channels.
    Journal of Biomedical Optics 02/2013; 18(2):26009. · 2.75 Impact Factor
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    Dimple Modgil, Bradley E Treeby, Patrick J La Rivière
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    ABSTRACT: Attenuation effects can be significant in photoacoustic tomography since the generated pressure signals are broadband, and ignoring them may lead to image artifacts and blurring. La Rivière et al. [Opt. Lett. 31(6), pp. 781-783, (2006)] had previously derived a method for modeling the attenuation effect and correcting for it in the image reconstruction. This was done by relating the ideal, unattenuated pressure signals to the attenuated pressure signals via an integral operator. We derive an integral operator relating the attenuated pressure signals to the absorbed optical energy for a planar measurement geometry. The matrix operator relating the two quantities is a function of the temporal frequency, attenuation coefficient and the two-dimensional spatial frequency. We perform singular-value decomposition (SVD) of this integral operator to study the problem further. We find that the smallest singular values correspond to wavelet-like eigenvectors in which most of the energy is concentrated at times corresponding to greater depths in tissue. This allows us to characterize the ill-posedness of recovering the absorbed optical energy distribution at different depths in an attenuating medium. This integral equation can be inverted using standard SVD methods, and the initial pressure distribution can be recovered. We conduct simulations and derive an algorithm for image reconstruction using SVD for a planar measurement geometry. We also study the noise and resolution properties of this image-reconstruction method.
    Journal of Biomedical Optics 06/2012; 17(6):061204. · 2.75 Impact Factor
  • Adam Petschke, Patrick J. La Rivière
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    ABSTRACT: We discuss a method for using the pseudoinverse of the system matrix to perform photoacoustic image reconstruction. In our method, the regularization levels are set and the pseudoinverse matrices are calculated just once for all possible objects, so the reconstruction step consists only of a matrix-vector multiplication, which is very fast. We expect this method to work well in photoacoustic imaging because the dominant noise mechanism is usually transducer thermal noise, which is object independent. We find that this reconstruction method offers improvements in ideal observer signal-to-noise ratio, resolution, and the length of streak artifacts compared to standard filtered backprojection.
    Proceedings of SPIE - The International Society for Optical Engineering 02/2012; · 0.20 Impact Factor
  • D.S. Rigie, P.J. La Riviere
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    ABSTRACT: Many different approaches to spectral CT, also called dual-energy CT, are being investigated for clinical use, but there is somewhat of a lack of quantitative metrics for evaluating performance with regard to clinical tasks. In this paper we apply a Hotelling Observer model with signal variability to the task of distinguishing two different contrast materials in a known background. The calculation of the associated Hotelling SNR gives a quantitative description of how well a particular spectral CT system performs. Unlike the detectability studies that are carried out in conventional CT, the inclusion of signal variability is key to applying the Hotelling Observer to dual-energy data. This model could be applied to many tasks that are being studied in clinical trials, such as creating virtual non-contrast images, bone removal, or kidney stone identification. Additionally, the proposed model can be adapted to examine the information loss associated with various dual-energy reconstruction algorithms.
    Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2012 IEEE; 01/2012
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    ABSTRACT: Synchrotron-based X-ray imaging is a useful tool in biomedical research because it can nondestructively produce high-resolution, 3D images. In this technique, X-rays impinge upon a thin scintillator and the visible light emission is focused onto a CCD using microscope optics. With this type of detector, sub-micron resolution has been achieved. We have also studied the possibility of extending this detector to have multiple scintillating layers for the purposes of performing spectral microCT with polychromatic sources. When such a multi-layer detector is illuminated by a polychromatic spectrum, the first layer will preferentially stop lower-energy X-rays, and the deeper layers higher-energy X-rays, leading to limited but perfectly registered spectral resolution. This detection setup also has the advantage of efficient use of synchrotron X-rays, short scan times, and the potential adaptation to a bench top system. Here we present some of our preliminary experimental results obtained using a custom multi-layer scintillating detector in conjunction with a color CCD camera. We found that our dual-layer detector does provide a significant amount of spectral separation, which suggests that material decomposition will be possible. This will be useful in identifying the elemental stains in X-ray histology. So far we have only attempted to do the material decomposition in the image domain because it is simpler to implement and does not require very precise calibration data. In the future, we would like to develop a calibration phantom that will enable us to do the decomposition in the sinogram domain. This yields a more quantitatively rigorous decomposition and has the additional advantage of eliminating beam-hardening artifacts caused by the polychromatic spectrum.
    Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2012 IEEE; 01/2012
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    Ling Jian Meng, Nan Li, Patrick J. La Riviere
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    ABSTRACT: This paper presents a feasibility study for using two new imaging geometries for synchrotron X-ray fluorescence emission tomography (XFET) applications. In the proposed approaches, the object is illuminated with synchrotron X-ray beams of various cross-sectional dimensions. The resultant fluorescence photons are detected by high-resolution imaging-spectrometers coupled to collimation apertures. To verify the performance benefits of the proposed methods over the conventional line-by-line scanning approach, we have used both Monte Carlo simulations and an analytical system performance index to compare several different imaging geometries. This study has demonstrated that the proposed XFET approach could lead to a greatly improved imaging speed, which is critical for making XFET a practical imaging modality for a wide range of applications.
    IEEE Transactions on Nuclear Science 12/2011; 58(6):3359-3369. · 1.46 Impact Factor
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    ABSTRACT: PURPOSE To monitor and evaluate pancreatic β-cell activity in the normal and diabetic pancreas using manganese enhanced MRI (MEMRI). METHOD AND MATERIALS Five normal and six diabetic adult Lewis rats were imaged on a 9.4T scanner. Diabetes was induced by streptozotocin treatment (60mg/kg body wt). Mn enhanced axial imaging was acquired on 16 slices through the pancreas using a Magnetization Prepared Rapid Acquisition Gradient Echo pulse sequence pre-contrast and during an IV Mn bolus (3.4g/kg body wt) and an IP glucose bolus (0.75g/kg body wt) at ~30 and ~60 min, respectively. Pancreatic regions of interest (ROIs) were drawn and average signal intensities were calculated. Then, the signal enhancement due to Mn (ΔSm = (Sm-Spre)/Spre) and glucose ( ΔSg = (Sg-Sm)/Spre) were calculated, where Spre, Sm, Sg are pre-contrast, post-Mn, and post-glucose signals, respectively. Finally, a weighted average of the signal enhancement in a volumetric ROI was calculated for each rat. In addition, serum insulin and tissue Mn concentration were measured via ELISA and atomic absorption, respectively. RESULTS Post-Mn relative signal enhancement in diabetic rats (2.7±1.2) was significantly lower than normal rats (5.6±1.5) (p<0.005). Similar results were observed in normal versus diabetic rats (0.93±0.44 vs 0.16±0.43) post-glucose administration (p<0.02). Atomic absorption data revealed that Mn concentrations in the body and tail of pancreas were ~2x greater post-glucose than baseline. Insulin concentration was significantly increased following glucose administration in normal but not in diabetic animals. CONCLUSION Elevated MEMRI contrast in the normal pancreas compared to the diabetic was supported by increased Mn content via atomic absorption. β-cell functionality was not affected by Mn as measured by glucose responsive insulin levels. MRI monitoring of β-cell mass and function is likely to detect a therapeutic window resulting in efficient pharmaceutical response and clinical benefit. CLINICAL RELEVANCE/APPLICATION Functional imaging of the pancreas would be instrumental in the development of novel therapies aimed at maintaining or increasing pancreatic function.
    Radiological Society of North America 2011 Scientific Assembly and Annual Meeting; 11/2011
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    ABSTRACT: Manganese (Mn) is a calcium (Ca) analog that has long been used as a magnetic resonance imaging (MRI) contrast agent for investigating cardiac tissue functionality, for brain mapping and for neuronal tract tracing studies. Recently, we have extended its use to investigate pancreatic β-cells and showed that, in the presence of MnCl(2), glucose-activated pancreatic islets yield significant signal enhancement in T(1)-weigheted MR images. In this study, we exploited for the first time the unique capabilities of X-ray fluorescence microscopy (XFM) to both visualize and quantify the metal in pancreatic β-cells at cellular and subcellular levels. MIN-6 insulinoma cells grown in standard tissue culture conditions had only a trace amount of Mn, 1.14 ± 0.03 × 10(-11)µg/µm(2), homogenously distributed across the cell. Exposure to 2 mM glucose and 50 µM MnCl(2) for 20 min resulted in nonglucose-dependent Mn uptake and the overall cell concentration increased to 8.99 ± 2.69 × 10(-11) µg/µm(2). When cells were activated by incubation in 16 mM glucose in the presence of 50 µM MnCl(2), a significant increase in cytoplasmic Mn was measured, reaching 2.57 ± 1.34 × 10(-10) µg/µm(2). A further rise in intracellular concentration was measured following KCl-induced depolarization, with concentrations totaling 1.25 ± 0.33 × 10(-9) and 4.02 ± 0.71 × 10(-10) µg/µm(2) in the cytoplasm and nuclei, respectively. In both activated conditions Mn was prevalent in the cytoplasm and localized primarily in a perinuclear region, possibly corresponding to the Golgi apparatus and involving the secretory pathway. These data are consistent with our previous MRI findings, confirming that Mn can be used as a functional imaging reporter of pancreatic β-cell activation and also provide a basis for understanding how subcellular localization of Mn will impact MRI contrast.
    Contrast Media & Molecular Imaging 11/2011; 6(6):474-81. · 2.87 Impact Factor
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    Keith C Cheng, Xuying Xin, Darin P Clark, Patrick La Riviere
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    ABSTRACT: Imaging can potentially make a major contribution to the Zebrafish Phenome Project, which will probe the functions of vertebrate genes through the generation and phenotyping of mutants. Imaging of whole animals at different developmental stages through adulthood will be used to infer biological function. Cell resolutions will be required to identify cellular mechanism and to detect a full range of organ effects. Light-based imaging of live zebrafish embryos is practical only up to ∼2 days of development, owing to increasing pigmentation and diminishing tissue lucency with age. The small size of the zebrafish makes possible whole-animal imaging at cell resolutions by histology and micron-scale tomography (microCT). The histological study of larvae is facilitated by the use of arrays, and histology's standard use in the study of human disease enhances its translational value. Synchrotron microCT with X-rays of moderate energy (10-25 keV) is unimpeded by pigmentation or the tissue thicknesses encountered in zebrafish of larval stages and beyond, and is well-suited to detecting phenotypes that may require 3D modeling. The throughput required for this project will require robotic sample preparation and loading, increases in the dimensions and sensitivity of scintillator and CCD chips, increases in computer power, and the development of new approaches to image processing, segmentation, and quantification.
    Current opinion in genetics & development 09/2011; 21(5):620-9. · 8.99 Impact Factor
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    Phillip A Vargas, Patrick J La Rivière
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    ABSTRACT: In recent years, the authors and others have been exploring the use of penalized-likelihood sinogram-domain smoothing and restoration approaches for emission and transmission tomography. The motivation for this strategy was initially pragmatic: to provide a more computationally feasible alternative to fully iterative penalized-likelihood image reconstruction involving expensive backprojections and reprojections, while still obtaining some of the benefits of the statistical modeling employed in penalized-likelihood approaches. In this work, the authors seek to compare the two approaches in greater detail. The sinogram-domain strategy entails estimating the "ideal" line integrals needed for reconstruction of an activity or attenuation distribution from the set of noisy, potentially degraded tomographic measurements by maximizing a penalized-likelihood objective function. The objective function models the data statistics as well as any degradation that can be represented in the sinogram domain. The estimated line integrals can then be input to analytic reconstruction algorithms such as filtered backprojection (FBP). The authors compare this to fully iterative approaches maximizing similar objective functions. The authors present mathematical analyses based on so-called equivalent optimization problems that establish that the approaches can be made precisely equivalent under certain restrictive conditions. More significantly, by use of resolution-variance tradeoff studies, the authors show that they can yield very similar performance under more relaxed, realistic conditions. The sinogram- and image-domain approaches are equivalent under certain restrictive conditions and can perform very similarly under more relaxed conditions. The match is particularly good for fully sampled, high-resolution CT geometries. One limitation of the sinogram-domain approach relative to the image-domain approach is the difficulty of imposing additional constraints, such as image non-negativity.
    Medical Physics 08/2011; 38(8):4811-23. · 3.01 Impact Factor
  • Adam M. Alessio, Patrick J. La Riviere
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    ABSTRACT: Iterative image reconstruction offers improved signal to noise properties for CT imaging. A primary challenge with iterative methods is the substantial computation time. This computation time is even more prohibitive in 4D imaging applications, such as cardiac gated or dynamic acquisition sequences. In this work, we propose only updating the time-varying elements of a 4D image sequence while constraining the static elements to be fixed or slowly varying in time. We test the method with simulations of 4D acquisitions based on measured cardiac patient data from a) a retrospective cardiac-gated CT acquisition and b) a dynamic perfusion CT acquisition. We target the kinetic elements with one of two methods: 1) position a circular ROI on the heart, assuming area outside ROI is essentially static throughout imaging time; and 2) select varying elements from the coefficient of variation image formed from fast analytic reconstruction of all time frames. Targeted kinetic elements are updated with each iteration, while static elements remain fixed at initial image values formed from the reconstruction of data from all time frames. Results confirm that the computation time is proportional to the number of targeted elements; our simulations suggest that 3 times reductions in reconstruction time. The images reconstructed with the proposed method have matched mean square error with full 4D reconstruction. The proposed method is amenable to most optimization algorithms and offers the potential for significant computation improvements, which could be traded off for more sophisticated system models or penalty terms.
    Proceedings of SPIE - The International Society for Optical Engineering 02/2011; · 0.20 Impact Factor
  • Adam Petschke, Patrick J. La Rivière
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    ABSTRACT: We compare imaging systems using continuous-wave (CW) lasers with a chirped intensity modulation frequency to pulsed lasers. We show that the resolution is the same in both cases. We also compare the signal-to-noise ratio (SNR) of the two systems assuming the fluence is set by the American National Standards Institute (ANSI) limits. Although the SNR depends on several parameters, we find that it is about 20 dB to 30 dB larger for pulsed lasers for reasonable values of the parameters. However, CW diode lasers have the advantage of being compact and relatively inexpensive, which may outweigh the slightly lower SNR in many applications.
    Proceedings of SPIE - The International Society for Optical Engineering 02/2011; · 0.20 Impact Factor

Publication Stats

552 Citations
123.50 Total Impact Points

Institutions

  • 2014
    • The University of Chicago Medical Center
      • Department of Radiology
      Chicago, Illinois, United States
  • 1997–2014
    • University of Chicago
      • Department of Radiology
      Chicago, Illinois, United States
  • 2011
    • University of Illinois, Urbana-Champaign
      • Department of Nuclear, Plasma and Radiological Engineering
      Urbana, IL, United States
  • 2001–2011
    • University of Illinois at Chicago
      • Department of Radiology (Chicago)
      Chicago, Illinois, United States