Publications by authors named "Zhixiong Guo"

16 Publications

  • Page 1 of 1

Open reduction and internal fixation for displaced Salter-Harris type II fractures of the distal tibia: a retrospective study of sixty-five cases in children.

J Orthop Surg Res 2021 Mar 27;16(1):224. Epub 2021 Mar 27.

Children's Hospital of Soochow University, No.92 Zhongnan Street, Suzhou Industiral Park, Suzhou, Jiangsu province, China.

Background: The treatment for displaced Salter-Harris II (S-H II) distal tibia fractures remains controversial. The purpose of this study was to review S-H II distal tibia fractures and evaluate the rate of premature physeal closure (PPC) treated by open reduction and internal fixation (ORIF).

Methods: We reviewed the charts and radiographs of S-H II fractures of the distal tibia with displacement > 3 mm between 2012 and 2019 treated by ORIF. Patients were followed up for a minimum of 6 months. CT scans of injured side or contralateral ankle radiograph were obtained if there was any evidence of PPC. Any angular deformity or shortening of the involved leg was documented. Multivariable logistic regression was performed to identify risk factors for the occurrence of PPC.

Results: A total of 65 patients with a mean age of 11.8 years were included in this study. The mean initial displacement was 8.0 mm. All patients but one were treated within 7 days after injury and the mean interval was 3.7 days. Supination-external rotation injuries occurred in 50 patients, pronation-eversion external rotation in 13, and supination-plantar flexion in two. The residual gap was less than 1 mm in all patients following ORIF and all fractures healed within 4-6 weeks. Superficial skin infection developed in one patient. Ten patients complained of the cosmetic scar. The rate of PPC was 29.2% and two patients with PPC developed a varus deformity of the ankle. Patients with associated fibular fracture had 7 times greater odds of developing PPC. Age, gender, injured side, mechanism of injury, amount of initial displacement, interval from injury to surgery, or energy of injury did not significantly affect the rate of PPC.

Conclusions: ORIF was an effective choice of treatment for S-H II distal tibia fractures with displacement > 3 mm to obtain a satisfactory reduction. PPC is a common complication following ORIF. The presence of concomitant fibula fracture was associated with PPC.
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http://dx.doi.org/10.1186/s13018-021-02359-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8004420PMC
March 2021

A pH-Responsive Polymer-CeO Hybrid to Catalytically Generate Oxidative Stress for Tumor Therapy.

Small 2020 11 2;16(47):e2004654. Epub 2020 Nov 2.

Department of Gastroenterology, Tangdu Hospital, Fourth Military Medical University, No. 1, Xinsi Road, Xi'an, 710038, China.

Catalytic generation of reactive oxygen species has been developed as a promising methodology for tumor therapy. Direct O production from intratumor oxygen exhibits exceptional tumor therapeutic efficacy. Herein, this therapy strategy is demonstrated by a pH-responsive hybrid of porous CeO nanorods and sodium polystyrene sulfonate that delivers high oxidative activity for O generation within acidic tumor microenvironments for chemodynamic therapy and only limited oxidative activity in neutral media to limit damage to healthy organs. The hydrated polymer-nanorod hybrids with large hydrodynamic diameters form nanoreactors that locally trap oxygen and biological substrates inside and improve the charge transfer between the catalysts and substrates in the tumor microenvironment, leading to enhanced catalytic O production and consequent oxidation. Together with successful in vitro and in vivo experiments, these data show that the use of hybrids provides a compelling opportunity for the delivery selective chemodynamic tumor therapy.
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http://dx.doi.org/10.1002/smll.202004654DOI Listing
November 2020

Concurrent ipsilateral Tillaux fracture and medial malleolar fracture in adolescents: management and outcome.

J Orthop Surg Res 2020 Sep 17;15(1):423. Epub 2020 Sep 17.

Children's Hospital of Soochow University, No. 92 Zhongnan street, Suzhou, Industrial Park, Jiangsu, China.

Background: The concurrent ipsilateral Tillaux fracture with medial malleolar fracture in adolescents commonly suffer from high-energy injury, making treatment more difficult. The aim of this study was to discuss the mechanism on injury, diagnosis, and treatment of this complex fracture pattern.

Methods: The charts and radiographs of six patients were reviewed. The function was assessed by the American Orthopedic Foot and Ankle Society ankle-hindfoot scores.

Results: The mean age at operation was 12.8 years. The mean interval from injury to operation was 7.7 days. Five Tillaux fractures and all medial malleolar fractures were shown on AP plain radiographs. One Tillaux fracture and two cases with avulsion of posterolateral tibial aspect were confirmed in axial computerized tomography. There was talar subluxation laterally with medial space widening in three and syndesmotic disruption in one. There were five patients sustaining ipsilateral distal fibular fractures. All fractures, except nonunion in two medial malleolar fractures and in one Tillaux fracture, healed within 6-8 weeks. There was one case of osteoarthritis of ankle joint. The average AOFAS score was 88.7.

Conclusions: Computerized tomography is helpful in identifying the fracture pattern. Anatomic reduction and internal fixation of Tillaux and medial malleolar fracture was recommended to restore the articular surface congruity and ankle stability.
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http://dx.doi.org/10.1186/s13018-020-01961-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7499953PMC
September 2020

Spectral Monte Carlo simulation of collimated solar irradiation transfer in a water-filled prismatic louver.

Appl Opt 2018 Apr;57(12):3021-3030

The Monte Carlo model was developed to simulate the collimated solar irradiation transfer and energy harvest in a hollow louver made of silica glass and filled with water. The full solar spectrum from the air mass 1.5 database was adopted and divided into various discrete bands for spectral calculations. The band-averaged spectral properties for the silica glass and water were obtained. Ray tracing was employed to find the solar energy harvested by the louver. Computational efficiency and accuracy were examined through intensive comparisons of different band partition approaches, various photon numbers, and element divisions. The influence of irradiation direction on the solar energy harvest efficiency was scrutinized. It was found that within a 15° polar angle of incidence, the harvested solar energy in the louver was high, and the total absorption efficiency reached 61.2% under normal incidence for the current louver geometry.
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http://dx.doi.org/10.1364/AO.57.003021DOI Listing
April 2018

Biosensing in a microelectrofluidic system using optical whispering-gallery mode spectroscopy.

Biomicrofluidics 2011 Sep 12;5(3):34114-3411414. Epub 2011 Aug 12.

Department of Mechanical and Aerospace Engineering, Rutgers, the State University of New Jersey, Piscataway, New Jersey 08854, USA.

Label-free detection of biomolecules using an optical whispering-gallery mode sensor in a microelectrofluidic channel is simulated. Negatively charged bovine serum albumin is considered as the model protein analyte. The analyte transport in aqueous solution is controlled by an externally applied electrical field. The finite element method is employed for solving the equations of the charged species transport, the Poisson equation of electric potential, the equations of conservation of momentum and energy, and the Helmholtz equations of electromagnetic waves. The adsorption process of the protein molecules on the microsensor head surface is monitored by the resonance frequency shifts. Frequency shift caused by temperature variation due to Joule heating is analyzed and found to be negligible. The induced shifts behave in a manner similar to Langmuir-like adsorption kinetics; but the time constant increases due to the presence of the external electrical field. A correlation of the frequency shift, the analyte feed concentration in the solution, and the applied voltage gradient is obtained, in which an excellent linear relationship between the frequency shift and the analyte concentration is revealed. The applied voltage gradient enhances significantly the analyte concentration in the vicinity of the sensor surface; thus, the sensor sensitivity which has a power function of the voltage gradient with exponent 2.85 in the controlled voltage range. Simulated detection of extremely low protein concentration to the pico-molar level is carried out.
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http://dx.doi.org/10.1063/1.3615237DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3364829PMC
September 2011

Phase-function normalization for accurate analysis of ultrafast collimated radiative transfer.

Appl Opt 2012 Apr;51(12):2192-201

Department of Mechanical and Aerospace Engineering, Rutgers, the State University of New Jersey, Piscataway, NJ 08854, USA.

The scattering of radiation from collimated irradiation is accurately treated via normalization of phase function. This approach is applicable to any numerical method with directional discretization. In this study it is applied to the transient discrete-ordinates method for ultrafast collimated radiative transfer analysis in turbid media. A technique recently developed by the authors, which conserves a phase-function asymmetry factor as well as scattered energy for the Henyey-Greenstein phase function in steady-state diffuse radiative transfer analysis, is applied to the general Legendre scattering phase function in ultrafast collimated radiative transfer. Heat flux profiles in a model tissue cylinder are generated for various phase functions and compared to those generated when normalization of the collimated phase function is neglected. Energy deposition in the medium is also investigated. Lack of conservation of scattered energy and the asymmetry factor for the collimated scattering phase function causes overpredictions in both heat flux and energy deposition for highly anisotropic scattering media. In addition, a discussion is presented to clarify the time-dependent formulation of divergence of radiative heat flux.
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http://dx.doi.org/10.1364/AO.51.002192DOI Listing
April 2012

Nanofiltration and sensing of picomolar chemical residues in aqueous solution using an optical porous resonator in a microelectrofluidic channel.

Nanotechnology 2012 Feb;23(6):065502

Department of Mechanical and Aerospace Engineering, Rutgers, The State University of New Jersey, Piscataway, NJ 08854, USA.

For the first time the use of a porous microresonator placed in a microelectrofluidic system for integrated functions of nanofiltration and sensing of small biomolecules and chemical analytes in extremely dilute solution was proposed and investigated. As an example, aminoglycosides in drug residues in food and livestock products were considered as the trace chemical analyte. The filtration process of the charged analyte in aqueous solution driven by an applied electrical field and the accompanying optical whispering-gallery modes in the resonator are modeled. The dynamic process of adsorption and desorption of the analyte onto the porous matrix is studied. Deposition of the analyte inside the porous structure will alter the material refractive index of the resonator, and thus induce an optical resonance frequency shift. By measuring the optical frequency shift, the analyte concentration as well as the absorption/desorption process can be analyzed. Through an intensive numerical study, a correlation between the frequency shift and the analyte concentration and the applied electrical voltage gradient was obtained. This reveals a linear relationship between the resonance frequency shift and the analyte concentration. The applied electrical voltage substantially enhances the filtration capability and the magnitude of the optical frequency shift, pushing the porous resonator-based sensor to function at the extremely dilute picomolar concentration level for small bio/chemical molecules down to the sub-nanometer scale. Moreover, use of the second-order whispering-gallery mode is found to provide better sensitivity compared with the first-order mode.
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http://dx.doi.org/10.1088/0957-4484/23/6/065502DOI Listing
February 2012

Ultrashort pulsed laser ablation and stripping of freeze-dried dermis.

Lasers Med Sci 2010 Jul 8;25(4):517-24. Epub 2009 Dec 8.

Department of Mechanical and Aerospace Engineering, Rutgers, The State University of New Jersey, Piscataway, NJ 08854, USA.

Plasma-mediated laser ablation and dissection of freeze-dried human dermis using an ultrashort pulsed laser of pulse width 900 fs and wavelength 1,552 nm were investigated. The surface ablation line width and depth in relation to irradiation fluence and pulse overlap rate were characterized and measured by scanning electron microscopy. The ablation threshold fluence for freeze-dried dermis was determined as 8.32 J/cm(2) and the incubation factor subject to pulse train irradiation was found to be 0.54. Histological examination showed no thermal damage with single line ablation. Even with multiline ablation, thermal damage was insignificant and the lateral damage zone was generally within 10 microm with 100 continuously repeated line scans. Ultrashort pulsed laser ablation of the interior of dry dermal tissue was shown to strip thin dermal slices with different thicknesses ranging from 20 to 40 microm.
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http://dx.doi.org/10.1007/s10103-009-0741-9DOI Listing
July 2010

Thermal interaction of short-pulsed laser focused beams with skin tissues.

Phys Med Biol 2009 Jul 17;54(13):4225-41. Epub 2009 Jun 17.

Department of Mechanical and Aerospace Engineering, Rutgers, The State University of New Jersey, Piscataway, NJ, USA.

Time-dependent thermal interaction is developed in a skin tissue cylinder subjected to the irradiation of a train of short laser pulses. The skin embedded with a small tumor is stratified as three layers: epidermis, dermis and subcutaneous fat with different optical, thermal and physiological properties. The laser beam is focused to the tumor site by an objective lens for thermal therapy. The ultrafast radiation heat transfer of the focused beam is simulated by the transient discrete ordinates method. The transient Pennes bio-heat equation is solved numerically by the finite volume method with alternating direction implicit scheme. Emphasis is placed on the characterization of the focused beam propagation and absorption and the temperature rise in the focal spot. The effects of the focal spot size and location, the laser power, and the bio-heat equation are investigated. Comparisons with collimated irradiation are conducted. The focused beam can penetrate a greater depth and produce higher temperature rise at the target area, and thus reduce the possibility of thermal damage to the surrounding healthy tissue. It is ideal for killing cancerous cells and small tumors.
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http://dx.doi.org/10.1088/0031-9155/54/13/017DOI Listing
July 2009

Multi-time-scale heat transfer modeling of turbid tissues exposed to short-pulsed irradiations.

Comput Methods Programs Biomed 2007 May 1;86(2):112-23. Epub 2007 Mar 1.

Department of Mechanical and Aerospace Engineering, Rutgers, The State University of New Jersey, Piscataway, NJ 08854, USA.

A combined hyperbolic radiation and conduction heat transfer model is developed to simulate multi-time-scale heat transfer in turbid tissues exposed to short-pulsed irradiations. An initial temperature response of a tissue to an ultrashort pulse irradiation is analyzed by the volume-average method in combination with the transient discrete ordinates method for modeling the ultrafast radiation heat transfer. This response is found to reach pseudo steady state within 1 ns for the considered tissues. The single pulse result is then utilized to obtain the temperature response to pulse train irradiation at the microsecond/millisecond time scales. After that, the temperature field is predicted by the hyperbolic heat conduction model which is solved by the MacCormack's scheme with error terms correction. Finally, the hyperbolic conduction is compared with the traditional parabolic heat diffusion model. It is found that the maximum local temperatures are larger in the hyperbolic prediction than the parabolic prediction. In the modeled dermis tissue, a 7% non-dimensional temperature increase is found. After about 10 thermal relaxation times, thermal waves fade away and the predictions between the hyperbolic and parabolic models are consistent.
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http://dx.doi.org/10.1016/j.cmpb.2007.01.009DOI Listing
May 2007

Simulated parametric studies in optical imaging of tumors through temporal log-slope difference mapping.

Med Eng Phys 2007 Dec 30;29(10):1142-8. Epub 2007 Jan 30.

Department of Mechanical and Aerospace Engineering, Rutgers, The State University of New Jersey, 98 Brett Road, Piscataway, NJ 08854, USA.

Numerical studies are conducted to evaluate the noninvasive imaging method of temporal log-slope difference mapping (TLSDM). Emphasis is placed on the parametric examination of tumor's size, enhanced absorption contrast ratio, and embedment depth on the imaging quality and accuracy. It is found that the imaging quality and accuracy are predominantly determined by the tumor size and its embedment depth. The TLSDM method can detect a small tumor of 10mm in size when the tumor is embedded at a shallow depth down to 10mm. With decreasing tumor size and/or increasing embedment depth, both image quality and accuracy worsen. The imaging method requires the enhanced absorption contrast ratio be 20:1 or above.
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http://dx.doi.org/10.1016/j.medengphy.2006.12.002DOI Listing
December 2007

Numerical characterization of whispering-gallery mode optical microcavities.

Appl Opt 2006 Feb;45(4):611-8

Department of Mechanical and Aerospace Engineering, Rutgers, the State University of New Jersey, Piscataway, New Jersey 08854, USA.

We characterize planar microcavities in whispering-gallery mode optical resonances. The microcavity consists of a waveguide and a microdisk, and a nanoscale gap separates the waveguide and the microdisk. The devices can be fabricated on Si-based thin films by using conventional microelectronics techniques. To characterize these types of cavity, we study a broad range of resonator configuration parameters including the size of the microdisk, the width of the gap, and the waveguide dimensions. The finite-element method is used for solving Maxwell's equations. The electric fields and the energy density distributions are obtained and compared between the on-resonance and off-resonance situations. A brilliant ring with a strong electric field and a high-energy density is found inside the periphery of the microdisk under first-order resonance. While under second-order resonance, there are two bright rings, and the light intensity in the inner ring is stronger than that in the outer ring. The resonant frequencies and their free spectral ranges are predominantly determined by the size of the microdisk. The gap effect on the resonant frequencies is observable, although it is minor. The gap strongly affects the full width at half-maximum (FWHM), finesse, and quality factor of the resonances. With an increase in the gap width from 100 to 300 nm, both the Q value and finesse increase substantially, while the FWHM decreases. The waveguide width has a visible influence on the Q value, FWHM, and finesse as well.
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http://dx.doi.org/10.1364/ao.45.000611DOI Listing
February 2006

Optical imaging of breast tumor through temporal log-slope difference mappings.

Comput Biol Med 2006 Feb 23;36(2):209-23. Epub 2004 Dec 23.

Department of Mechanical and Aerospace Engineering, Rutgers, The State University of New Jersey, Piscataway, 08854, USA.

A novel optical temporal log-slope difference mapping approach is proposed for cancerous breast tumor detection. In this method, target tissues are illuminated by near-infrared (700-1000 nm) ultrashort laser pulses from various surface source points, and backscattered time-resolved light signals are collected at the same surface points. By analyzing the log-slopes of decaying signals over all points on the source-detection grid, a log-slope distribution on the surface is obtained. After administration of absorption contrast agents, the presence of cancerous tumors increases the decaying steepness of the transient signals. The mapping of log-slope difference between native tissue and absorption-enhanced cancerous tissue indicates the location and projection of tumors on the detection surface. In this paper, we examine this method in the detection of breast tumors in two model tissue phantoms through computer simulation. The first model has a spherical tumor of 6mm in diameter embedded at the tissue center. The second model is a large tissue phantom embedded with a non-centered spherical tumor 8mm in diameter. Monte Carlo methods were employed to simulate the light transport and signal measurement. It is shown that the tumor in both the tissue models will be accurately projected on the detection surface by the proposed log-slope difference mapping method. The image processing is very fast and does not require any inverse optimization in image reconstruction.
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http://dx.doi.org/10.1016/j.compbiomed.2004.09.003DOI Listing
February 2006

Imaging analysis of digital holography.

Opt Express 2005 Apr;13(7):2444-52

In this study we focus on understanding the system imaging mechanisms given rise to the unique characteristic of discretization in digital holography. Imaging analysis with respect to the system geometries is investigated and the corresponding requirements for reliable holographic imaging are specified. In addition, the imaging capacity of a digital holographic system is analyzed in terms of space-bandwidth product. The impacts due to the discrete features of the CCD sensor that are characterized by the amount of sensitive pixels and the pixel dimension are quantified. The analysis demonstrates the favorable properties of an in-line system arrangement in both the effective field of view and imaging resolution.
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http://dx.doi.org/10.1364/opex.13.002444DOI Listing
April 2005

Fast 3-d optical imaging with transient fluorescence signals.

Opt Express 2004 Feb;12(3):449-57

A fast 3-D optical imaging method with use of exogenous fluorescence agent is proposed and demonstrated by simulation in a model tissue. After administration of fluorescent agent, ultrashort near-infrared laser pulses are used to illuminate the tissue and excite fluorescence emission. The transient fluorescence signals are detected on the tissue boundaries and employed to reconstruct a 3-D image of relative fluorescence emission distribution inside the tissue. A region with greater fluorescence emission represents a diseased tissue if the fluorescent agent has a close affinity with the disease. We successfully demonstrated the feasibility of this method in the imaging of a 4x4x4mm(3) tumor embedded at the center of a cubical tissue phantom with an uptake distribution of fluorescent indocyanine green dye. The image reconstruction does not involve any inverse problem. It took less than 5 minutes in a PC for the model imaging problem.
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http://dx.doi.org/10.1364/opex.12.000449DOI Listing
February 2004

Ultrafast-laser-radiation transfer in heterogeneous tissues with the discrete-ordinates method.

Appl Opt 2003 Jun;42(16):2897-905

Department of Mechanical and Aerospace Engineering, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, USA.

Here light propagation and radiation transfer of ultrafast laser pulses in heterogeneous biological tissues are simulated by use of the discrete-ordinates method (DOM). Formulations for solving the time-dependent radiation-transfer equation are deduced for three-dimensional geometries incorporating the Fresnel specularly reflecting boundary condition and characteristics of ultrafast laser pulses. The present method can treat both the incident laser intensity and the scattered radiation intensity from the walls of the targeted tissue as two components, i.e., a diffuse part and a specular part. Reflectivity at the tissue-air interface is calculated by use of Snell's law and the Fresnel equation. The high-order S10 DOM method is found to be adequate for describing the propagation and transfer of ultrafast laser radiation in heterogeneous tissues. The time-dependent radiation field in the tissue as well as the temporal radiation intensity profiles at the boundaries can be obtained simultaneously. The absolute values of the logarithmic slope of the temporal reflectance and transmittance at various detector positions are found to converge to a constant value in a homogeneous tissue model. With the inclusion of a small inhomogeneity, such a value will change in line with the property of the embedded inhomogeneity. The orientation of heterogeneity of the tissues also substantially affects the radiation intensity at the boundaries. The effect of the Fresnel boundary in the modeling is pronounced. The simulated transmitted signals are broadened and amplified under specularly reflecting boundary condition as compared with those under diffusely reflecting boundary conditions.
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http://dx.doi.org/10.1364/ao.42.002897DOI Listing
June 2003