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Search Results: 1 - 10 of 325380 matches for " Marios S Pattichis "
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A High-Speed Dynamic Partial Reconfiguration Controller Using Direct Memory Access Through a Multiport Memory Controller and Overclocking with Active Feedback
John C. Hoffman,Marios S. Pattichis
International Journal of Reconfigurable Computing , 2011, DOI: 10.1155/2011/439072
Abstract: Dynamically reconfigurable computing platforms provide promising methods for dynamic management of hardware resources, power, and performance. Yet, progress in dynamically reconfigurable computing is fundamentally limited by the reconfiguration time overhead. Prior research in the development of dynamic partial reconfiguration (DPR) controllers has been limited by its use of the Processor Local Bus (PLB). As a result, the bus was unavailable during DPR. This resulted in significant time overhead. To minimize the overhead, we introduce the use of a multiport memory controller (MPMC) that frees the PLB during the reconfiguration process. The processor is thus allowed to switch to other tasks during the reconfiguration operation. This effectively limits the reconfiguration overhead. An interrupt is used to inform the processor when the operation is complete. Therefore, the system can multitask during the reconfiguration operation. Furthermore, to maximize performance, we introduce the use of overclocking with active feedback. During overclocking, the use of active feedback is used to ensure that the device voltage and temperature are within nominal operating conditions. All of these contributions lead to significant performance improvements over current partial reconfiguration subsystems. The portability of the system, demonstrated on the Virtex-4 and the Virtex-5, consists of four different hardware platforms. 1. Introduction As the speed and size of FPGA reconfigurable fabric has grown, the ability to perform multiple complex parallel applications, using a single device, has become a reality. For example, as early as 2003, the BMW Williams F1 team was running its fifth generation vehicle control and monitoring (VCM) unit with a Texas Instruments DSP and a Xilinx Virtex family of FPGA devices to control mission critical operations [1]. Today, FPGAs have increased product features and decreased product time to market and given system designers abilities that were only possible with the use of custom ASICs. Dynamic partial reconfiguration allows the FPGA programmable fabric to change its mode of operation during run time. Effectively, dynamic partial reconfiguration (DPR) allows for time-division multiplexing portions of the FPGA fabric, while the system is operating. Future systems are likely to benefit from the development of effective systems that use DPR to provide for dynamic performance and power control. Currently, when considering partial reconfiguration, the largest bottleneck is the time it takes to switch hardware resources. When a device is
Optimal compressed sensing reconstructions of fMRI using deterministic and stochastic sampling geometries
Oliver Jeromin, Marios S Pattichis, Vince D Calhoun
BioMedical Engineering OnLine , 2012, DOI: 10.1186/1475-925x-11-25
Abstract: We investigate the use of frequency-space (k-space) sampling based on: (i) 2D deterministic geometries of dyadic phase encoding (DPE) and spiral low pass (SLP) geometries, and (ii) 2D stochastic geometries based on random phase encoding (RPE) and random samples on a PDF (RSP). Overall, we consider over 36 frequency-sampling geometries at different sampling rates. For each geometry, we compute optimal reconstructions of single BOLD fMRI ON & OFF images, as well as BOLD fMRI activity maps based on the difference between the ON and OFF images. We also provide an optimization framework for determining the optimal parameters and sampling geometry prior to scanning.For each geometry, we show that reconstruction parameter optimization converged after just a few iterations. Parameter optimization led to significant image quality improvements. For activity detection, retaining only 20.3% of the samples using SLP gave a mean PSNR value of 57.58 dB. We also validated this result with the use of the Structural Similarity Index Matrix (SSIM) image quality metric. SSIM gave an excellent mean value of 0.9747 (max?=?1). This indicates that excellent reconstruction results can be achieved. Median parameter values also gave excellent reconstruction results for the ON/OFF images using the SLP sampling geometry (mean SSIM?>?=0.93). Here, median parameter values were obtained using mean-SSIM optimization. This approach was also validated using leave-one-out.We have found that compressive sensing parameter optimization can dramatically improve fMRI image reconstruction quality. Furthermore, 2D MRI scanning based on the SLP geometries consistently gave the best image reconstruction results. The implication of this result is that less complex sampling geometries will suffice over random sampling. We have also found that we can obtain stable parameter regions that can be used to achieve specific levels of image reconstruction quality when combined with specific k-space sampling geometries.
A 3D Freehand Ultrasound System for Multi-view Reconstructions from Sparse 2D Scanning Planes
Honggang Yu, Marios S Pattichis, Carla Agurto, M Beth Goens
BioMedical Engineering OnLine , 2011, DOI: 10.1186/1475-925x-10-7
Abstract: We present a low-cost and flexible ultrasound imaging system that integrates several image processing components to allow for 3D reconstructions from limited numbers of 2D image planes and multiple acoustic views. Our approach is based on a 3D freehand ultrasound system that allows users to control the 2D acquisition imaging using conventional 2D probes.For reliable performance, we develop new methods for image segmentation and robust multi-view registration. We first present a new hybrid geometric level-set approach that provides reliable segmentation performance with relatively simple initializations and minimum edge leakage. Optimization of the segmentation model parameters and its effect on performance is carefully discussed. Second, using the segmented images, a new coarse to fine automatic multi-view registration method is introduced. The approach uses a 3D Hotelling transform to initialize an optimization search. Then, the fine scale feature-based registration is performed using a robust, non-linear least squares algorithm. The robustness of the multi-view registration system allows for accurate 3D reconstructions from sparse 2D image planes.Volume measurements from multi-view 3D reconstructions are found to be consistently and significantly more accurate than measurements from single view reconstructions. The volume error of multi-view reconstruction is measured to be less than 5% of the true volume. We show that volume reconstruction accuracy is a function of the total number of 2D image planes and the number of views for calibrated phantom. In clinical in-vivo cardiac experiments, we show that volume estimates of the left ventricle from multi-view reconstructions are found to be in better agreement with clinical measures than measures from single view reconstructions.Multi-view 3D reconstruction from sparse 2D freehand B-mode images leads to more accurate volume quantification compared to single view systems. The flexibility and low-cost of the proposed sy
A standardised protocol for texture feature analysis of endoscopic images in gynaecological cancer
Marios S Neofytou, Vasilis Tanos, Marios S Pattichis, Constantinos S Pattichis, Efthyvoulos C Kyriacou, Dimitris D Koutsouris
BioMedical Engineering OnLine , 2007, DOI: 10.1186/1475-925x-6-44
Abstract: We investigate texture feature variability for a variety of targets encountered in clinical endoscopy. All images were captured at clinically optimum illumination and focus using 720 × 576 pixels and 24 bits color for: (i) a variety of testing targets from a color palette with a known color distribution, (ii) different viewing angles, (iv) two different distances from a calf endometrial and from a chicken cavity. Also, human images from the endometrium were captured and analysed. For texture feature analysis, three different sets were considered: (i) Statistical Features (SF), (ii) Spatial Gray Level Dependence Matrices (SGLDM), and (iii) Gray Level Difference Statistics (GLDS). All images were gamma corrected and the extracted texture feature values were compared against the texture feature values extracted from the uncorrected images. Statistical tests were applied to compare images from different viewing conditions so as to determine any significant differences.For the proposed acquisition procedure, results indicate that there is no significant difference in texture features between the panoramic and close up views and between angles. For a calibrated target image, gamma correction provided an acquired image that was a significantly better approximation to the original target image. In turn, this implies that the texture features extracted from the corrected images provided for better approximations to the original images. Within the proposed protocol, for human ROIs, we have found that there is a large number of texture features that showed significant differences between normal and abnormal endometrium.This study provides a standardized protocol for avoiding any significant texture feature differences that may arise due to variability in the acquisition procedure or the lack of color correction. After applying the protocol, we have found that significant differences in texture features will only be due to the fact that the features were extracted from differen
Tree Image Growth Analysis Using Instantaneous Phase Modulation
Janakiramanan Ramachandran,Marios S. Pattichis,Louis A. Scuderi,Justin S. Baba
EURASIP Journal on Advances in Signal Processing , 2011, DOI: 10.1155/2011/586865
Abstract:
A Self-Reconfigurable Platform for the Implementation of 2D Filterbanks with Real and Complex-Valued Inputs, Outputs, and Filter Coefficients
Daniel Llamocca,Marios Pattichis
VLSI Design , 2014, DOI: 10.1155/2014/651943
Abstract: We introduce a dynamically reconfigurable 2D filterbank that supports both real and complex-valued inputs, outputs, and filter coefficients. This general purpose filterbank allows for the efficient implementation of 2D filterbanks based on separable 2D FIR filters that support all possible combinations of input and output signals. The system relies on the use of dynamic reconfiguration of real/complex one-dimensional filters to minimize the required hardware resources. The system is demonstrated using an equiripple and a Gabor filterbank and the results using both real and complex-valued input images. We summarize the performance of the system in terms of the required processing times, energy, and accuracy. 1. Introduction Filterbank implementations in hardware require significant resources. Each filter in the filterbank is often implemented using multiply-and-add circuitry (modifiable coefficients) or by a fixed-coefficient circuitry. In what follows, we will use the term static implementations to describe filterbank implementations that are based on fixed hardware. A clear limitation of static implementations comes from the fact that hardware resources cannot be adjusted based on the number of coefficients or the number of filters. Furthermore, energy consumption is often a function of the implemented static hardware regardless of whether the hardware resources are actually used. Dynamic partial reconfiguration (DPR) technology is becoming increasingly popular for addressing the aforementioned problems by time-multiplexing FPGA resources [1]. For filterbanks, DPR lets us implement only one filter at a time, which can potentially result in significant power savings over static implementation approaches. In this paper, we introduce a self-reconfigurable implementation for a 2D complex filterbank that only requires one 1D filter to be present on the FPGA at a time. We study all the possible cases as well as providing results in terms of accuracy, energy, and performance. Applications of complex filterbanks can be found in [2, 3]. For efficient hardware realizations, we focus on 2D FIR separable filtering that allows implementations by means of two 1D FIR filters. This separability property allows us to consider a DPR approach that keeps only one filter (row or column) at a time. We presented some related earlier work in [4–7]. In [4], we described an efficient 1D FIR filtering system that combined the distributed arithmetic (DA) technique with DPR. An early 2D real filterbank implementation was presented in [5]. We presented a dynamic real 2D FIR filter
Partial Reconfigurable FIR Filtering System Using Distributed Arithmetic
Daniel Llamocca,Marios Pattichis,G. Alonzo Vera
International Journal of Reconfigurable Computing , 2010, DOI: 10.1155/2010/357978
Abstract: Dynamic partial reconfiguration (DPR) allows us to adapt hardware resources to meet time-varying requirements in power, resources, or performance. In this paper, we present two new DPR systems that allow for efficient implementations of 1D FIR filters on modern FPGA devices. To minimize the required partial reconfiguration region (PRR), both implementations are based on distributed arithmetic. For a smaller required PRR, the first system only allows changes to the filter coefficient values while keeping the rest of the architecture fixed. The second DPR system allows full FIR-filter reconfiguration while requiring a larger PR region. We investigate the proposed system performance in terms of the dynamic reconfiguration rates. At low reconfiguration rates, the DPR systems can maintain much higher throughputs. We also present an example that demonstrates that the system can maintain a throughput of 10 Mega-samples per second while fully reconfiguring about seventy times per second. 1. Introduction Dynamically reconfigurable systems offer unique advantages over nondynamic systems. Dynamic adaptation provides us with the ability to adapt hardware resources to match real-time varying requirements. The majority of the 1D FIR filtering literature is dominated by static implementations. Here, we use the term static to refer to both CMOS implementations (e.g., [1–5]) and reconfigurable hardware (nondynamic) (e.g., [6, 7]). Some implementations use the label reconfigurable in the sense of having the capability to load different filter coefficients on demand (e.g., [2–5]). In the context of this paper, such implementations are considered static since the underlying hardware is not changed or reconfigured. For reconfigurable hardware, the most efficient implementations are based on Distributed Arithmetic (DA) [8]. These filters have coefficients fixed or hardwired within the filter's logic. This approach allows fast and efficient implementations while sacrificing some flexibility, since coefficients cannot be changed at run time. Dynamic partial reconfiguration (DPR) can be used in this scenario to provide the flexibility of coefficients’ values changes without having to turn off the device and only rewriting a section of the configuration memory. The efficiency of DPR over the full reconfiguration alternative and the savings in terms of power and resources is a function of the relative size of the portion being reconfigured [9]. We consider a DPR approach that allows us to change the filter’s structural configuration and/or the number of taps. The proposed
A Dynamic Dual Fixed-Point Arithmetic Architecture for FPGAs
G. Alonzo Vera,Marios Pattichis,James Lyke
International Journal of Reconfigurable Computing , 2011, DOI: 10.1155/2011/518602
Abstract: In FPGA embedded systems, designers usually have to make a compromise between numerical precision and logical resources. Scientific computations in particular, usually require highly accurate calculations and are computing intensive. In this context, a designer is left with the task of implementing several arithmetic cores for parallel processing while supporting high numerical precision with finite logical resources. This paper introduces an arithmetic architecture that uses runtime partial reconfiguration to dynamically adapt its numerical precision, without requiring significant additional logical resources. The paper also quantifies the relationship between reduced logical resources and savings in power consumption, which is particularly important for FPGA implementations. Finally, our results show performance benefits when this approach is compared to alternative static solutions within bounds on the reconfiguration rate. 1. Introduction In the realm of embedded systems, a designer often faces the decision of what numerical representation to use and how to implement it. Particularly, when using programmable logic devices, constraints such as power consumption and area resources must be tradedoff with performance requirements. Floating point is still too expensive in terms of resources to be intensively used in programmable logic devices. Fixed-point is cheaper but lacks the flexibility to represent numbers in a wide range. In order to increase numerical range, several fixed-point units—supporting different number representations—are required. Alternatively, numerical range can be increased by a single fixed-point unit able to change its binary point position. In this paper, runtime partial reconfiguration (RTR) is used to dynamically change an arithmetic unit's precision, operation, or both. This approach requires intensive use of partial reconfiguration making it particularly important to take into consideration the time it takes to reconfigure. This time is commonly referred to as the reconfiguration time overhead. Usually, runtime reconfigurable implementations involve the exchange of relatively large functional units that have large processing times. This, along with low reconfiguration frequencies, significantly reduces the impact of the reconfiguration time overhead on the performance. Unlike common runtime reconfigurable implementations, the exchangeable functional units in this approach are smaller, and reconfiguration frequencies are larger. Smaller exchangeable functional units are possible by using a dual fixed-point (DFX) numerical
Advances in the management of pectus deformities in children  [PDF]
Natalie Swergold, Prasanna Sridharan, Marios Loukas, Ronald S. Chamberlain
Open Journal of Pediatrics (OJPed) , 2013, DOI: 10.4236/ojped.2013.33038
Abstract:

Pectus excavatum (PE) and pectus carinatum (PC) are relatively common deformities involving the anterior chest wall, occurring in 1:1000 and 1:1500 live births, respectively. While the etiology remains an enigma, the association of pectus deformities with other skeletal abnormalities suggests that connective tissue disease may play a role in their pathogenesis. Clinical features of these deformities vary with severity, as determined by the Haller index and Backer ratio, but frequently include cardiac and respiratory abnormalities. Importantly, there exist profound psychosocial implications for children afflicted with these defofrmities, including but not limited to feelings of embarrassment and maladaptive social behaviors. These debilitating characteristics have prompted the development of novel medical and surgical corrective techniques. The correction of pectus deformities reduces the incidence of physiological complications secondary to chest wall malformation, while simultaneously improving body image and psychosocial development in the affected pediatric population. The Ravitch (open) and Nuss (minimally invasive) procedures remain the most frequently employed methods of pectus deformity repair, with no difference in overall complication rates, though individual complication rates vary with treatment. The Nuss procedure is associated with a higher rate of recurrence due to bar migration, hemothorax, and pneumothorax. Postoperative pain management is markedly more difficult in patients who have undergone Nuss repair. Patients undergoing the Ravitch procedure require less postoperative analgesia, but have longer operation times and a larger surgical scar. The cosmetic

results of the Nuss procedure and its minimally invasive nature make it preferable to the Ravitch repair. Newer treatment modalities, including the vacuum bell, magnetic mini-mover procedure (3MP), and dynamic compression bracing (DCB) appear promising, and may ultimately provide effective methods of noninvasive repair. However, these modalities suffer from a lack of extensive published evidence, and the limited number of studies currently published fail to adequately define their long-term effectiveness.

Effect of zooming on texture features of ultrasonic images
Stavros K Kakkos, Andrew N Nicolaides, Efthyvoulos Kyriacou, Constantinos S Pattichis, George Geroulakos
Cardiovascular Ultrasound , 2006, DOI: 10.1186/1476-7120-4-8
Abstract: Eighteen still B-mode images of carotid plaques were zoomed during carotid scanning (zoom factor 1.3) and both images were transferred to a PC and normalised. Using bilinear and bicubic interpolation, the original images were interpolated in a process of simulating off-line zoom using the same interpolation factor. With the aid of the colour-coded image, carotid plaques of the original, zoomed and two resampled images for each case were outlined and histogram, first order and second order statistics were subsequently calculated.Most second order statistics (21/25, 84%) were significantly (p < 0.05) sensitive to image zooming during scanning, in contrast to histogram and first order statistics (4/25, 16%, p < 0.001, Fisher's exact test). Median (interquartile range) change of those features sensitive to zooming was 18.14% (4.94–28.43). Image interpolation restored these changes, the bicubic interpolation being superior compared to bilinear interpolation (p = 0.036).Texture analysis of ultrasonic plaques should be performed under standardised resolution settings; otherwise a resolution normalisation algorithm should be applied.Cross-sectional studies have shown that echolucent and heterogeneous internal carotid artery plaques on B-mode ultrasound scanning are associated with neurological symptoms [1-3]; similarly prospective studies have confirmed that these subjective plaque characteristics predict future neurological symptoms [4,5]. Our group has investigated objective, computer-assisted methods, which involved standardisation of ultrasonic images (normalisation) and echogenicity measurements [6,7]. We have also, like other groups, investigated objective methods of accessing plaque heterogeneity, known also as texture analysis, and found these helpful in separating symptomatic from asymptomatic plaques [8-12].Image resolution has a significant effect on texture analysis results; this has been shown by studies on remote sensing [13-15], and ultrasound [16]. Images ob
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