Abstract-The growing class of portable systems, such as personal computing and communication devices, has resulted in a new set of system design requirements, mainly characterized by dominant importance of power minimization and design reuse. The energy efficiency of systems-on-a-chip (SOC) could be much improved if one were to vary the supply voltage dynamically at run time. We develop the design methodology for the lowpower core-based real-time SOC based on dynamically variable voltage hardware. The key challenge is to develop effective scheduling techniques that treat voltage as a variable to be determined, in addition to the conventional task scheduling and allocation. Our synthesis technique also addresses the selection of the processor core and the determination of the instruction and data cache size and configuration so as to fully exploit dynamically variable voltage hardware, which results in significantly lower power consumption for a set of target applications than existing techniques. The highlight of the proposed approach is the nonpreemptive scheduling heuristic, which results in solutions very close to optimal ones for many test cases. The effectiveness of the approach is demonstrated on a variety of modern industrialstrength multimedia and communication applications. Index Terms-High-level synthesis, scheduling, synthesis for low power, system-on-a-chip (SOC).
Remarkable progress in positron emission tomography (PET) development has occurred in recent years, in hardware, software, and computer implementation of image reconstruction. Recent development in PET scanners such as the high-resolution research tomograph (HRRT) developed by CTI (now Siemens) represents such a case and is capable of greatly enhanced resolution as well as sensitivity. In these PET scanners, the amount of coincidence line data collected contains more than 4.5 x 10(9) coincidence lines of response generated by as many nuclear detectors as 120 000. This formidable amount of data and the reconstruction of this data set pose a real problem in HRRT and have also been of the major bottle neck in further developments of high resolution PET scanners as well as their applications. In these classes of PET scanners, therefore, obtaining one set of reconstructed images often requires many hours of image reconstruction. For example, in HRRT with full data collection in a normal brain scan (using SPAN 3), the image reconstruction time is close to 80 min, making it practically impossible to attempt any list-mode-based dynamic imaging since the image reconstruction time would take many days (as much as 43 h or more for 32-frame dynamic image reconstruction). To remedy this data-handling problem in image reconstruction, we developed a new algorithm based on the symmetry properties of the projection and backprojection processes, especially in the 3-D OSEM algorithm where multiples of projection and back-projection are required. In addition, the single-instruction multiple-data (SIMD) technique also allowed us to successfully incorporate the symmetry properties mentioned above, thereby effectively reducing the total image reconstruction time to a few minutes. We refer to this technique as the symmetry and SIMD-based projection-backprojection (SSP) technique or algorithm and the details of the technique will be discussed and an example of the application of the technique to the HRRT's OSEM algorithm will be presented as a demonstration.
We consider the problem of schtifing the mixed worMoad of both sporadic (on-fine) and periodic (off-fine) tasks on variable voltage processor to optimize power consumption while ensuring thatp eriodic tasks meet their destines and to accept as many sporadic tasks, which can be guaranteed to meet their destines, as possible. The proposed efficient dgonthms restit in the scheduling solutions, which are very close to the minimum bound achievable with the dynamictiy variable voltage approach. The effectiventis of the proposed dgonthrns is shown on extensive experiments with rd-fife design examples. hhoductionThe growing class of portable systems, such as persomd computing and communication devices, demands data-and computationintensive tictionrdities with low power consumption. h this paper, we target synthwis of application-specific system-on-chip with variable voltage processor core, mrtitiy focusing on procasor power optimization. The distribution of power dissipation by the components of application-specific system-on-chip depends on the actuã pplications running on the system. However, extensive studies indicate that the power consumption of the processor accounts for significant portion of the oveti power consumption [1].The most effective way to reduce power consumption of a processor core in CMOS technology is to lower the supply voltage level, which exploits the quadratic dependence of power on voltage [2]. Reducing the supply voltage however incraes circuit delay and decrwes clock speed. The restiting processor core consumes lower average power while meeting the deafines. Unfortunately, this technique is ineffective when tight dmtines are present in systems. Another power optimization technique for processor cores is the prdctive system shutdown [7, 14]. The prdctive system shutdown technique, though usable even in the presence of tight deafines, is inferior to the supply voltage reduction technique for the cases when both twhniques can be appfied. The fimitations of the techniques arise due to the fact that systems are designed with a fixed supply voltage. The supply voltage reduction technique attempts to find a sin~e optimal voltage level for the entire processor operation, while the pr~ctive system shutdown technique makw a binary mntime dtision whether to turn on or off the power supply.Recent advances in power supply technology rdong with custom and commercird CMOS chips that are capable of operating reliably over a range of supply voltages make it possible to create processor cores with supply voltage that can be varid at mn time according to application timing constraints [12, 15]. The variable voltage processor core can operate at different optimal points rdong its power vs. speed curve in order to achieve much higher energy efficiency than existing techniques for a wider class of applications.
Abstract£The economic viability of the reusable core-based design paradigm depends on the development of techniques for intellectual property protection. We introduce the first dynamic watermarking technique for protecting the value of intellectual property of CAD and compilation tools and reusable core components. The essence of the new approach is the addition of a set of design and timing constraints which encodes the author's signature. The constraints are selected in such a way that they result in minimal hardware overhead while embedding the signature which is unique and difficult to detect, remove and forge. We establish the first set of relevant metrics which forms the basis for the quantitative analysis, evaluation, and comparison of watermarking techniques. We develop a generic approach for signature data hiding in designs, which is applicable in conjunction with an arbitrary behavioral synthesis task, such as scheduling, assignment, allocation, and transformations. Error correcting codes are used to augment the protection of the signature data from tampering attempts. On a large set of design examples, studies indicate the effectiveness of the new approach in a sense that the signature data, which are highly resilient, difficult to detect and remove, and yet easy to verify, can be embedded in designs with very low hardware overhead.
and 5 Siemens Healthcare MI, Knoxville, TennesseeIntegrated whole-body PET/MR facilitates the implementation of a broad variety of respiratory motion correction strategies, taking advantage of the strengths of both modalities. The goal of this study was the quantitative evaluation with clinical data of different MR-and PET-data-based motion correction strategies for integrated PET/MR. Methods: The PET and MR data of 20 patients were simultaneously acquired for 10 min on an integrated PET/MR system after administration of 18 F-FDG or 68 Ga-DOTANOC. Respiratory traces recorded with a bellows were compared against MR self-gating signals and signals extracted from PET raw data with the sensitivity method, by applying principal component analysis (PCA) or Laplacian eigenmaps and by using a novel variation combining the former and either of the latter two. Gated sinograms and MR images were generated accordingly, followed by image registration to derive MR motion models. Corrected PET images were reconstructed by incorporating this information into the reconstruction. An optical flow algorithm was applied for PETbased motion correction. Gating and motion correction were evaluated by quantitative analysis of apparent tracer uptake, lesion volume, displacement, contrast, and signal-to-noise ratio. Results: The correlation between bellows-and MR-based signals was 0.63 ± 0.19, and that between MR and the sensitivity method was 0.52 ± 0.26. Depending on the PET raw-data compression, the average correlation between MR and PCA ranged from 0.25 ± 0.30 to 0.58 ± 0.33, and the range was 0.25 ± 0.30 to 0.42 ± 0.34 if Laplacian eigenmaps were applied. By combining the sensitivity method and PCA or Laplacian eigenmaps, the maximum average correlation to MR could be increased to 0.74 ± 0.21 and 0.70 ± 0.19, respectively. The selection of the best PET-based signal for each patient yielded an average correlation of 0.80 ± 0.13 with MR. Using the best PET-based respiratory signal for gating, mean tracer uptake increased by 17 ± 19% for gating, 13 ± 10% for MRbased motion correction, and 18 ± 15% for PET-based motion correction, compared with the static images. Lesion volumes were 76 ± 31%, 83 ± 18%, and 74 ± 22% of the sizes in the static images for gating, MR-based motion correction, and PET-based motion correction, respectively. Conclusion: Respiratory traces extracted from MR and PET data are comparable to those based on external sensors. The proposed PET-driven gating method improved respiratory signals and overall stability. Consistent results from MR-and PET-based correction methods enable more flexible PET/MR scan protocols while achieving higher PET image quality.
LSO scintillators (Lu2Sio5:Ce) have a background radiation which originates from the isotope Lu-176 that is present in natural occurring lutetium. The decay that occurs in this isotope is a beta decay that is in coincidence with cascade gamma emissions with energies of 307,202 and 88 keV. The coincidental nature of the beta decay with the gamma emissions allow for separation of emission data originating from a positron annihilation event from transmission type data from the Lu-176 beta decay. By using the time of flight information, and information of the chord length between two LSO pixels in coincidence as a result of a beta emission and emitted gamma, a second time window can be set to observe transmission events simultaneously to emission events. Using the time when the PET scanner is not actively acquiring positron emission data, a continuous blank can be acquired and used to reconstruct a transmission image. With this blank and the measured transmission data, a transmission image can be reconstructed. This reconstructed transmission image can be used to perform emission data corrections such as attenuation correction and scatter corrections or starting images for algorithms that estimate emission and attenuation simultaneously. It is observed that the flux of the background activity is high enough to create useful transmission images with an acquisition time of 10 min.
The growing class of portable systems, such as personal computing and communication devices, has resulted in a new set of system design requirements, mainly characterized by dominant importance of power minimization and design reuse. We develop the design methodology for the low power core-based real-time system-onchip based on dynamically variable voltage hardware. The key challenge is to develop effective scheduling techniques that treat voltage as a variable to be determined, in addition to the conventional task scheduling and allocation. Our synthesis technique also addresses the selection of the processor core and the determination of the instruction and data cache size and configuration so as to fully exploit dynamically variable voltage hardware, which result in significantly lower power consumption for a set of target applications than existing techniques. The highlight of the proposed approach is the non-preemptive scheduling heuristic which results in solutions very close to optimal ones for many test cases. The effectiveness of the approach is demonstrated on a variety of modern industrial-strength multimedia and communication applications.
We have developed a positron emission tomography (PET) and magnetic resonance imaging (MRI) fusion system for the molecular-genetic imaging (MGI) of the in vivo human brain using two high-end imaging devices: the HRRT-PET, a high-resolution research tomograph dedicated to brain imaging on the molecular level, and the 7.0 T-MRI, an ultra-high field version used for morphological imaging. HRRT-PET delivers high-resolution molecular imaging with a resolution down to 2.5 mm full width at half maximum (FWHM), which allows us to observe the brain's molecular changes using the specific reporter genes and probes. On the other front, the 7.0 T-MRI, with submillimeter resolution images of the cortical areas down to 250 mum, allows us to visualize the fine details of the brainstem areas as well as the many cortical and subcortical areas. The new PET-MRI fusion imaging system will provide many answers to the questions on neurological diseases as well as cognitive neurosciences. Some examples of the answers are the quantitative visualization of neuronal functions by clear molecular and genetic bases, as well as diagnoses of many neurological diseases such as Parkinson's and Alzheimer's. The salient point of molecular-genetic imaging and diagnosis is the fact that they precede the morphological manifestations, and hence, the early and specific diagnosis of certain diseases, such as cancers.
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