Browsing by Author "Chen, Shih-Hao"

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Biomechanical comparison between lumbar disc arthroplasty and fusion
(2009-03-01)
Chen, Shih-Hao
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Zhong, Zheng-Cheng
;
Chen, Chen-Sheng
;
Chen, Wen-Jer
;
Hung, Chinghua
The artificial disc is a mobile implant for degenerative disc replacement that attempts to lessen the degeneration of the adjacent elements. However, inconsistent biomechanical results for the neighboring elements have been reported in a number of studies. The present study used finite element (FE) analysis to explore the biomechanical differences at the surgical and both adjacent levels following artificial disc replacement and interbody fusion procedures. First, a three-dimensional FE model of a five-level lumbar spine was established by the commercially available medical imaging software Amira 3.1.1, and FE software ANSYS 9.0. After validating the five-level intact (INT) model with previous in vitro studies, the L3/L4 level of the INT model was modified to either insert an artificial disc (ProDisc II; ADR) or incorporate bilateral posterior lumbar interbody fusion (PLIF) cages with a pedicle screw fixation system. All models were constrained at the bottom of the L5 vertebra and subjected to 150 N preload and 10 N m moments under four physiological motions. The ADR model demonstrated higher range of motion (ROM), annulus stress, and facet contact pressure at the surgical level compared to the non-modified INT model. At both adjacent levels, ROM and annulus stress were similar to that of the INT model and varied less than 7%. In addition, the greatest displacement of posterior annulus occurred at the superior-lateral region. Conversely, the PLIF model showed less ROM, less annulus stress, and no facet contact pressure at the surgical level compared to the INT model. The adjacent levels had obviously high ROM, annulus stress, and facet contact pressure, especially at the adjacent L2/3 level. In conclusion, the artificial disc replacement revealed no adjacent-level instability. However, instability was found at the surgical level, which might accelerate degeneration at the highly stressed annulus and facet joint. In contrast to disc replacement results, the posterior interbody fusion procedure revealed possibly accelerative degeneration of the annulus and facet joint at both adjacent levels. (C) 2008 IPEM. Published by Elsevier Ltd. All rights reserved.
Biomechanical comparison of three stand-alone lumbar cages - a three-dimensional finite element analysis
(2013-10-02)
Chen, Shih-Hao
;
Chiang, Ming-Chieh
;
Lin, Jin-Fu
;
Lin, Shang-Chih
;
Hung, Ching-Hua
Background: For anterior lumbar interbody fusion (ALIF), stand-alone cages can be supplemented with vertebral plate, locking screws, or threaded cylinder to avoid the use of posterior fixation. Intuitively, the plate, screw, and cylinder aim to be embedded into the vertebral bodies to effectively immobilize the cage itself. The kinematic and mechanical effects of these integrated components on the lumbar construct have not been extensively studied. A nonlinearly lumbar finite-element model was developed and validated to investigate the biomechanical differences between three stand-alone (Latero, SynFix, and Stabilis) and SynCage-Open plus transpedicular fixation. All four cages were instrumented at the L3-4 level. Methods: The lumbar models were subjected to the follower load along the lumbar column and the moment at the lumbar top to produce flexion (FL), extension (EX), left/right lateral bending (LLB, RLB), and left/right axial rotation (LAR, RAR). A 10 Nm moment was applied to obtain the six physiological motions in all models. The comparison indices included disc range of motion (ROM), facet contact force, and stresses of the annulus and implants. Results: At the surgical level, the SynCage-open model supplemented with transpedicular fixation decreased ROM (>76%) greatly; while the SynFix model decreased ROM 56-72%, the Latero model decreased ROM 36-91%, in all motions as compared with the INT model. However, the Stabilis model decreased ROM slightly in extension (11%), lateral bending (21%), and axial rotation (34%). At the adjacent levels, there were no obvious differences in ROM and annulus stress among all instrumented models. Conclusions: ALIF instrumentation with the Latero or SynFix cage provides an acceptable stability for clinical use without the requirement of additional posterior fixation. However, the Stabilis cage is not favored in extension and lateral bending because of insufficient stabilization.
Biomechanical comparison of unilateral and bilateral pedicle screws fixation for transforaminal lumbar interbody fusion after decompressive surgery - a finite element analysis
(2012-05-16)
Chen, Shih-Hao
;
Lin, Shang-Chih
;
Tsai, Wen-Chi
;
Wang, Chih-Wei
;
Chao, Shih-Heng
Background: Little is known about the biomechanical effectiveness of transforaminal lumbar interbody fusion (TLIF) cages in different positioning and various posterior implants used after decompressive surgery. The use of the various implants will induce the kinematic and mechanical changes in range of motion (ROM) and stresses at the surgical and adjacent segments. Unilateral pedicle screw with or without supplementary facet screw fixation in the minimally invasive TLIF procedure has not been ascertained to provide adequate stability without the need to expose on the contralateral side. This study used finite element (FE) models to investigate biomechanical differences in ROM and stress on the neighboring structures after TLIF cages insertion in conjunction with posterior fixation. Methods: A validated finite-element (FE) model of L1-S1 was established to implant three types of cages (TLIF with a single moon-shaped cage in the anterior or middle portion of vertebral bodies, and TLIF with a left diagonally placed ogival-shaped cage) from the left L4-5 level after unilateral decompressive surgery. Further, the effects of unilateral versus bilateral pedicle screw fixation (UPSF vs. BPSF) in each TLIF cage model was compared to analyze parameters, including stresses and ROM on the neighboring annulus, cage-vertebral interface and pedicle screws. Results: All the TLIF cages positioned with BPSF showed similar ROM (<5%) at surgical and adjacent levels, except TLIF with an anterior cage in flexion (61% lower) and TLIF with a left diagonal cage in left lateral bending (33% lower) at surgical level. On the other hand, the TLIF cage models with left UPSF showed varying changes of ROM and annulus stress in extension, right lateral bending and right axial rotation at surgical level. In particular, the TLIF model with a diagonal cage, UPSF, and contralateral facet screw fixation stabilize segmental motion of the surgical level mostly in extension and contralaterally axial rotation. Prominent stress shielded to the contralateral annulus, cage-vertebral interface, and pedicle screw at surgical level. A supplementary facet screw fixation shared stresses around the neighboring tissues and revealed similar ROM and stress patterns to those models with BPSF. Conclusions: TLIF surgery is not favored for asymmetrical positioning of a diagonal cage and UPSF used in contralateral axial rotation or lateral bending. Supplementation of a contralateral facet screw is recommended for the TLIF construct.
Biomechanical differences of Coflex-F and pedicle screw fixation combined with TLIF or ALIF - a finite element study
(2011)
Lo, Cheng-Chan
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Tsai, Kai-Jow
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Zhong, Zheng-Cheng
;
Chen, Shih-Hao
;
Hung, Chinghua
Lumbar interbody fusion is a common procedure for treating lower back pain related to degenerative disc diseases. The Coflex-F is a recently developed interspinous spacer, the makers of which claim that it can provide stabilisation similar to pedicle screw fixation. Therefore, this study compares the biomechanical behaviour of the Coflex-F device and pedicle screw fixation with transforaminal lumbar interbody fusion (TLIF) or anterior lumbar interbody fusion (ALIF) surgeries by using finite element analysis. The results show that the Coflex-F device combined with ALIF surgery can provide stability similar to the pedicle screw fixation combined with TLIF or ALIF surgery. Also, the posterior instrumentations (Coflex-F and pedicle screw fixation) combined with TLIF surgery had lower stability than when combined with ALIF surgery.
Biomechanical effect after Coflex and Coflex rivet implantation for segmental instability at surgical and adjacent segments: a finite element analysis
(2011)
Lo, Cheng-Chan
;
Tsai, Kai-Jow
;
Chen, Shih-Hao
;
Zhong, Zheng-Cheng
;
Hung, Chinghua
The Coflex device may provide stability to the surgical segment in extension but does not restore stability in other motion. Recently, a modified version called the Coflex rivet has been developed. The effects of Coflex and Coflex rivet implantation on the adjacent segments are still not clear; therefore, the purpose of this study was to investigate the biomechanical differences between Coflex and Coflex rivet implantation by using finite element analyses. The results show that the Coflex implantation can provide stability in extension, lateral bending, and axial rotation at the surgical segment, and it had no influence at adjacent segments except for extension. The Coflex rivet implantation can provide stability in all motions and reduce disc annulus stress at the surgical segment. Therefore, the higher range of motion and stress induced by the Coflex rivet at both adjacent discs may result in adjacent segment degeneration in flexion and extension.
Color-filter-free spatial visible light communication using RGB-LED and mobile-phone camera
(2014-12-15)
Chen, Shih-Hao
;
Chow, Chi-Wai
;
光電工程學系
;
光電工程研究所
;
Department of Photonics
A novel color-filter-free visible-light communication (VLC) system using red-green-blue (RGB) light emitting diode (LED) and mobile-phone camera is proposed and demonstrated for the first time. A feature matching method, which is based on the scale-invariant feature transform (SIFT) algorithm for the received grayscale image is used instead of the chromatic information decoding method. The proposed method is simple and saves the computation complexity. The signal processing is based on the grayscale image computation; hence neither color-filter nor chromatic channel information is required. A proof-of-concept experiment is performed and high performance channel recognition is achieved. (C) 2014 Optical Society of America
COLOR-FILTER-FREE WDM MIMO RGB-LED VISIBLE LIGHT COMMUNICATION SYSTEM USING MOBILE-PHONE CAMERA
(2014-01-01)
Chen, Shih-Hao
;
Chow, Chi-Wai
;
光電工程學系
;
Department of Photonics
Color-Filter-Free wavelength division multiplexing (WDM) Multiple-input and multiple-output (MIMO) Red-Green-Blue (RGB)-light emitting diode (LED) visible light communication (VLC) system using mobile-phone camera is proposed and demonstrated. Neither color filter nor chromatic color information is required in the proposed receiver (Rx). All image signal processing is based on the grayscale image, which can greatly simplify the WDM MIMO RGB-LED VLC system and save the cost of color splitting process. A proof-of-concept experiment is conducted. Optimized Scale-invariant feature transform (SIFT) algorithm is used to achieve the design.
Color-Shift Keying and Code-Division Multiple-Access Transmission for RGB-LED Visible Light Communications Using Mobile Phone Camera
(2014-12-01)
Chen, Shih-Hao
;
Chow, Chi-Wai
;
光電工程學系
;
光電工程研究所
;
Department of Photonics
Light-emitting diodes (LEDs) have been deployed for various applications in our daily lives. Similarly, image sensors or cameras integrated into mobile phones have become common. Hence, visible light communication (VLC) using LED and mobile phone cameras is attractive and provides low-cost wireless communication. In this paper, we propose and demonstrate a VLC system using color-shift-keying (CSK) modulation and code-division multiple-access (CDMA) technology simultaneously for the first time; a mobile phone camera is used as the receiver (Rx). CSK is used to enhance the VLC system capacity and to mitigate the single color light interference, whereas CDMA allows multiple users to access the network. The system design and operation mechanism of the proposed CSK-CDMA VLC system are discussed. A proof-of-concept demonstration is performed, and error-free transmission is achieved for multiple-access users. A 3-dB transmission gain is also obtained in each user when compared with the traditional on-off keying (OOK) modulation.
Color-Shift Keying and Code-Division Multiple-Access Transmission for RGB-LED Visible Light Communications Using Mobile Phone Camera
(2014-12)
Chen, Shih-Hao
;
Chow, Chi-Wai
;
光電工程學系
;
Department of Photonics
Light-emitting diodes (LEDs) have been deployed for various applications in our daily lives. Similarly, image sensors or cameras integrated into mobile phones have become common. Hence, visible light communication (VLC) using LED and mobile phone cameras is attractive and provides low-cost wireless communication. In this paper, we propose and demonstrate a VLC system using color-shift-keying (CSK) modulation and code-division multiple-access (CDMA) technology simultaneously for the first time; a mobile phone camera is used as the receiver (Rx). CSK is used to enhance the VLC system capacity and to mitigate the single color light interference, whereas CDMA allows multiple users to access the network. The system design and operation mechanism of the proposed CSK-CDMA VLC system are discussed. A proof-of-concept demonstration is performed, and error-free transmission is achieved for multiple-access users. A 3-dB transmission gain is also obtained in each user when compared with the traditional on-off keying (OOK) modulation.
Color-Shift Keying and Code-Division Multiple-Access Transmission for RGB-LED Visible Light Communications Using Mobile Phone Camera
(2014-12-01)
Chen, Shih-Hao
;
Chow, Chi-Wai
;
光電工程學系
;
Department of Photonics
Light-emitting diodes (LEDs) have been deployed for various applications in our daily lives. Similarly, image sensors or cameras integrated into mobile phones have become common. Hence, visible light communication (VLC) using LED and mobile phone cameras is attractive and provides low-cost wireless communication. In this paper, we propose and demonstrate a VLC system using color-shift-keying (CSK) modulation and code-division multiple-access (CDMA) technology simultaneously for the first time; a mobile phone camera is used as the receiver (Rx). CSK is used to enhance the VLC system capacity and to mitigate the single color light interference, whereas CDMA allows multiple users to access the network. The system design and operation mechanism of the proposed CSK-CDMA VLC system are discussed. A proof-of-concept demonstration is performed, and error-free transmission is achieved for multiple-access users. A 3-dB transmission gain is also obtained in each user when compared with the traditional on-off keying (OOK) modulation.
Color-Shift Keying and Code-Division Multiple-Access Transmission for RGB-LED Visible Light Communications Using Mobile Phone Camera
(2014-12-01)
Chen, Shih-Hao
;
Chow, Chi-Wai
;
光電工程學系
;
Department of Photonics
Light-emitting diodes (LEDs) have been deployed for various applications in our daily lives. Similarly, image sensors or cameras integrated into mobile phones have become common. Hence, visible light communication (VLC) using LED and mobile phone cameras is attractive and provides low-cost wireless communication. In this paper, we propose and demonstrate a VLC system using color-shift-keying (CSK) modulation and code-division multiple-access (CDMA) technology simultaneously for the first time; a mobile phone camera is used as the receiver (Rx). CSK is used to enhance the VLC system capacity and to mitigate the single color light interference, whereas CDMA allows multiple users to access the network. The system design and operation mechanism of the proposed CSK-CDMA VLC system are discussed. A proof-of-concept demonstration is performed, and error-free transmission is achieved for multiple-access users. A 3-dB transmission gain is also obtained in each user when compared with the traditional on-off keying (OOK) modulation.
Comparison of thresholding schemes for visible light communication using mobile-phone image sensor
(2016-02-08)
Liu, Yang
;
Chow, Chi-Wai
;
Liang, Kevin
;
Chen, Hung-Yu
;
Hsu, Chin-Wei
Based on the rolling shutter effect of the complementary metal-oxide-semiconductor (CMOS) image sensor, bright and dark fringes can be observed in each received frame. By demodulating the bright and dark fringes, the visible light communication (VLC) data logic can be retrieved. However, demodulating the bright and dark fringes is challenging as there is a high data fluctuation and large extinction ratio (ER) variation in each frame due. Hence proper thresholding scheme is needed. In this work, we propose and compare experimentally three thresholding schemes; including third-order polynomial curve fitting, iterative scheme and quick adaptive scheme. The evaluation of these three thresholding schemes is performed. (C) 2016 Optical Society of America
Differential signaling spread-spectrum modulation of the LED visible light wireless communications using a mobile-phone camera
(2015-02-01)
Chen, Shih-Hao
;
Chow, Chi-Wai
;
光電工程學系
;
Department of Photonics
Visible light communication (VLC) using spread spectrum modulation (SSM) and differential signaling (DS), detected by a mobile-phone camera is proposed and demonstrated for the first time to provide high immunity to background ambient light interference. The SSM signal provides the coding gain while the DS scheme enhances the clock recovery particular under high background ambient light. Experiment results confirm the feasibility of the proposed scheme, showing that the proposed system has 6-dB gain comparing with the traditional on-off keying (OOK) modulation under background ambient light of 3000 lux. The direct incident ambient light to the mobile-phone camera is 520 lux. (C) 2014 Elsevier B.V. All rights reserved.
DIRECT-DETECTION ALL-OPTICAL OFDM SUPERCHANNEL FOR LONG-REACH PON
(2014-01-01)
Chow, Chi-Wai
;
Yeh, Chien-Hung
;
Sung, Jiun-Yu
;
Chen, Shih-Hao
;
光電工程學系
Orthogonal-frequency-division-multiplexing (OFDM) is a promising candidate for the future high-speed optical access networks. As the OFDM signal is electronically generated and demodulated by fast Fourier transform (FFT) in the digital domain via electronic digital-to-analog and analog-to-digital converters (DAC/ADC) respectively, the OFDM signal bandwidth is limited by the sampling rate of the DAC/ADC. In this work, we present the feasibility of using all-optical OFDM for the future high-speed PON. All-optical OFDM is another class of optical multiple carrier transmission that relies on all-optically generated or demodulated orthogonal subcarriers. Hence, high data rate can be easily achieved. A 200 Gb/s OFDMA-LR-PON using all-optical OFDM super-channel (SC) is demonstrated. Apart from the optical wired transmission, w-band (100-GHz) millimeter-wave (MMW) wireless transmission is also demonstrated to support the in-building mobile broadband services.
Enhancement of Signal Performance in LED Visible Light Communications Using Mobile Phone Camera
(2015-10-01)
Chow, Chi-Wai
;
Chen, Chung-Yen
;
Chen, Shih-Hao
;
光電工程學系
;
光電工程研究所
Visible light communication (VLC) is attractive as a supplementary method for future fifth-generation (5G) wireless communication owing to the shortage of radio-frequency bandwidth in conventional wireless communications. The VLC systems reported in the literature are mainly based on PIN receivers (Rxs). It is highly desirable if these VLC signals can be detected by using built-in complementary metal-oxide-semiconductor (CMOS) cameras as Rxs to provide flexible and low-cost wireless communications. However, using the CMOS camera is challenging. In this paper, we propose and demonstrate a VLC link using a CMOS mobile phone camera as Rx. By using the rolling shutter effect of the CMOS sensor, the VLC data rate can be significantly enhanced. We first use a second-order polynomial fitting to mitigate the "blooming effect" (saturation of pixels) of the CMOS sensor. In order to extend the VLC transmission distance and mitigate the influence of the background noise, we also propose and demonstrate using histogram equalization and Sobel filter to enhance VLC signal performance. Finally, a third-order polynomial fitting is used to define the threshold. The experimental results show that significant improvement of bit error rate (BER) for about an order of magnitude under different illuminances can be achieved.
Finite element comparison of retrograde intramedullary nailing and locking plate fixation with/without an intramedullary allograft for distal femur fracture following total knee arthroplasty
(2014-01-01)
Chen, Shih-Hao
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Chiang, Ming-Chieh
;
Hung, Ching-Hua
;
Lin, Shang-Chih
;
Chang, Hsiao-Wei
Purpose: Periprosthetic distal femur fracture after total knee arthroplasty due to the stress-shielding phenomenon is a challenging problem. Retrograde intramedullary nail (RIMN) or locking plate (LP) fixation with/without a strut allograft has been clinically used via less invasive stabilization surgery (LISS) for the treatment of these periprosthetic fractures. However, their biomechanical differences in construct stability and implant stress have not been extensively studied, especially for the osteoporotic femur. Methods: This study used a finite-element method to evaluate the differences between RIMN, LP, and LP/allograft fixation in treating periprosthetic distal femur fractures. There were sixteen variations of two fracture angles (transverse and oblique), two loading conditions (compression and rotation), and four bony conditions (one normal and three osteoporotic). Construct stiffness, fracture micromotion, and implant stress were chosen as the comparison indices. Results: The LP/allograft construct provides both lateral and middle supports to the displaced femur. Comparatively, the LP and RIMN constructs, respectively, transmit the loads through the lateral and middle paths, thus providing more unstable support to the construct and high stressing on the implants. The fracture pattern plays a minor role in the construct stabilization of the three implants. In general, the biomechanical performances of the RIMN and LP constructs were comparable and significantly inferior to those of the LP/allograft construct. The bone quality should be evaluated prior to the selection of internal fixators. Conclusions: The LP/allograft construct significantly stabilizes the fracture gap, reduces the implant stress, and serves as the recommended fixation for periprosthetic distal femur fracture. (C) 2013 Elsevier B.V. All rights reserved.
Hierarchical scheme for detecting the rotating MIMO transmission of the in-door RGB-LED visible light wireless communications using mobile-phone camera
(2015-01-15)
Chen, Shih-Hao
;
Chow, Chi-Wai
;
光電工程學系
;
Department of Photonics
Multiple-input and multiple-output (MIMO) scheme can extend the transmission capacity for the lightemitting-diode (LED) based visible light communication (VLC) systems. The MIMO VLC system that uses the mobile-phone camera as the optical receiver (Rx) to receive MIMO signal from the n x n Red-GreenBlue (RGB) LED array is desirable. The key step of decoding this signal is to detect the signal direction. If the LED transmitter (Tx) is rotated, the Rx may not realize the rotation and transmission error can occur. In this work, we propose and demonstrate a novel hierarchical transmission scheme which can reduce the computation complexity of rotation detection in LED array VLC system. We use the n x n RGB LED array as the MIMO Tx. In our study, a novel two dimensional Hadamard coding scheme is proposed. Using the different LED color layers to indicate the rotation, a low complexity rotation detection method can be used for improving the quality of received signal. The detection correction rate is above 95% in the indoor usage distance. Experimental results confirm the feasibility of the proposed scheme. (C) 2014 Elsevier B.V. All rights reserved
HIERARCHICAL SCHEME FOR DETECTION OF ROTATING MIMO VISIBLE LIGHT COMMUNICATION SYSTEMS USING MOBILE-PHONE CAMERA
(2014-01-01)
Chen, Shih-Hao
;
Chow, Chi-Wai
;
光電工程學系
;
Department of Photonics
Multiple-input and multiple-output (MIMO) scheme can extend the transmission capacity for the light-emitting-diode (LED) visible light communication (VLC) system. The MIMO VLC system using the popular mobile-phone camera as the optical receiver (Rx) to receive MIMO signal from n x n Red-Green-Blue (RGB) LED array is desirable. The key step of decoding the received RGB LED array signals is detecting the direction of received array signals. If the LED transmitter (Tx) is rotated, the signal may not be received correctly and cause an error in the received signal. In this work, we propose and demonstrate a novel hierarchical transmission scheme which can reduce the computation complexity of rotation detection in LED array VLC system. We use the n x n RGB LED array as the MIMO Tx. A novel two dimension Hadamard coding scheme is proposed and demonstrated. The detection correction rate is above 95% in the indoor usage distance. Experimental results confirm the feasibility of the proposed scheme.
Passive Optical Receiver for Visible Light Communication (VLC)
(2015-01-01)
Chen, Hung-Yu
;
Liang, Kevin
;
Chen, Chung-Yen
;
Chen, Shih-Hao
;
Chow, Chi-Wai
We demonstrate using solar cell as optical receiver (Rx) for visible light communication (VLC). The solar cell is low cost and can convert the VLC optical signal into electrical signal without external power supply. As the response of the solar cell is very limited; we also propose and demonstrate using pre-distortion to significantly enhance the response of the solar cell Rx. A VLC capacity of 0.4 Mbit/s at bit-error-rate (BER) of 10(-9) under wireless transmission distance of 75 cm; and a capacity of 0.3 Mbit/s at BER of 10(-9) under wireless transmission distance of 125 cm can be achieved.
Passive Optical Receiver for Visible Light Communication (VLC)
(2015-01-01)
Chen, Hung-Yu
;
Liang, Kevin
;
Chen, Chung-Yen
;
Chen, Shih-Hao
;
Chow, Chi-Wai
We demonstrate using solar cell as optical receiver (Rx) for visible light communication (VLC). The solar cell is low cost and can convert the VLC optical signal into electrical signal without external power supply. As the response of the solar cell is very limited; we also propose and demonstrate using predistortion to significantly enhance the response of the solar cell Rx. A VLC capacity of 0.4 Mbit/s at bit-error-rate (BER) of 10(-9) under wireless transmission distance of 75 cm; and a capacity of 0.3 Mbit/s at BER of 10-9 under wireless transmission distance of 125 cm can be achieved.