scholarly journals The Characteristic Recovery Time as a Novel, Noninvasive Metric for Assessing In Vivo Cartilage Mechanical Function

2020 ◽  
Vol 48 (12) ◽  
pp. 2901-2910 ◽  
Author(s):  
Hattie C. Cutcliffe ◽  
Keithara M. Davis ◽  
Charles E. Spritzer ◽  
Louis DeFrate
Keyword(s):  
Mechanical Property ◽  
Relaxation Time ◽  
Recovery Time ◽  
Mechanical Response ◽  
Ex Vivo ◽  
Cartilage Thickness ◽  
Mechanical Function ◽  
Mechanical State ◽  
T2 Relaxation

AbstractOsteoarthritis (OA) is a disease characterized by the degeneration of cartilage tissue, and is a leading cause of disability in the United States. The clinical diagnosis of OA includes the presence of pain and radiographic imaging findings, which typically do not present until advanced stages of the disease when treatment is difficult. Therefore, identifying new methods of OA detection that are sensitive to earlier pathological changes in cartilage, which may be addressed prior to the development of irreversible OA, is critical for improving OA treatment. A potentially promising avenue for developing early detection methods involves measuring the tissue’s in vivo mechanical response to loading, as changes in mechanical function are commonly observed in ex vivo studies of early OA. However, thus far the mechanical function of cartilage has not been widely assessed in vivo. Therefore, the purpose of this study was to develop a novel methodology that can be used to measure an in vivo mechanical property of cartilage: the characteristic recovery time. Specifically, in this study we quantified the characteristic recovery time of cartilage thickness after exercise in relatively young subjects with asymptomatic cartilage. Additionally, we measured baseline cartilage thickness and T1rho and T2 relaxation times (quantitative MRI) prior to exercise in these subjects to assess whether baseline MRI measures are predictive of the characteristic recovery time, to understand whether or not the characteristic recovery time provides independent information about cartilage’s mechanical state. Our results show that the mean recovery strain response across subjects was well-characterized by an exponential approach with a characteristic time of 25.2 min, similar to literature values of human characteristic times measured ex vivo. Further, we were unable to detect a statistically significant linear relationship between the characteristic recovery time and the baseline metrics measured here (T1rho relaxation time, T2 relaxation time, and cartilage thickness). This might suggest that the characteristic recovery time has the potential to provide additional information about the mechanical state of cartilage not captured by these baseline MRI metrics. Importantly, this study presents a noninvasive methodology for quantifying the characteristic recovery time, an in vivo mechanical property of cartilage. As mechanical response may be indicative of cartilage health, this study underscores the need for future studies investigating the characteristic recovery time and in vivo cartilage mechanical response at various stages of OA.

scholarly journals Alterations in articular cartilage T2 star relaxation time following mechanical disorders: in vivo canine supraspinatus tendon resection models

2020 ◽  
Author(s):  
Dokwan Lee ◽  
Ki-Taek Hong ◽  
Tae Seong Lim ◽  
Eugene Lee ◽  
Ye Hyun Lee ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Articular Cartilage ◽  
Motion Tracking ◽  
Supraspinatus Tendon ◽  
Quantitative Mri ◽  
Joint Mechanics ◽  
T2 Relaxation Time ◽  
T2 Relaxation ◽  
Positive Correlations

Abstract Background: The role of altered joint mechanics on cartilage degeneration in in vivo models has not been studied successfully due to a lack of pre-injury information. We aimed 1) to develop an accurate in vivo canine model to measure the changes in joint loading and T2 star (T2*) relaxation time before and after unilateral supraspinatus tendon resections, and 2) to find the relationship between regional variations in articular cartilage loading patterns and T2* relaxation time distributions.Methods: Rigid markers were implanted in the scapula and humerus of tested dogs. The movement of the shoulder bones were measured by a motion tracking system during normal gaits. In vivo cartilage contact strain was measured by aligning 3D shoulder models with the motion tracking data. Articular cartilage T2* relaxation times were measured by quantitative MRI scans. Articular cartilage contact strain and T2* relaxation time were compared in the shoulders before and three months after the supraspinatus tendon resections.Results: Excellent accuracy and reproducibility were found in our in vivo contact strain measurements with less than 1% errors. Changes in articular cartilage contact strain exhibited similar patterns with the changes in the T2* relaxation time after resection surgeries. Regional changes in the articular cartilage T2* relaxation time exhibited positive correlations with regional contact strain variations three months after the supraspinatus resection surgeries.Conclusion: This is the first study to measure in vivo articular cartilage contact strains with high accuracy and reproducibility. Positive correlations between contact strain and T2* relaxation time suggest that the articular cartilage extracellular matrix may responds to mechanical changes in local areas.

Viscoelastic Characterization of Perfused Liver: Indentation Testing and Preliminary Modeling

2007 ◽  
Author(s):  
Amy E. Kerdok ◽  
Robert D. Howe ◽  
Simona Socrate
Keyword(s):  
Constitutive Model ◽  
Multiple Testing ◽  
Mechanical Response ◽  
Ex Vivo ◽  
Unknown Boundary ◽  
Abdominal Organs ◽  
Rheological Modeling ◽  
Unknown Boundary Conditions ◽  
Surgical Manipulation

Computer-aided medical technologies are currently restricted by the limited understanding of the mechanical response of solid abdominal organs to finite loading conditions typical of surgical manipulation [5]. This limitation is a result of the difficulty in acquiring the necessary data on whole organs. To develop a constitutive model capable of predicting complex surgical scenarios, multiple testing modalities need to be simultaneously obtained to capture the fundamental nature of the tissue’s behavior under such conditions. In vivo tests are essential to obtain a realistic response, but their inherent difficulty and unknown boundary conditions makes them an impractical approach. Ex vivo tests are easy to control, but the response is unrealistic. A perfusion apparatus was previously developed that obtained near in vivo conditions for whole livers while allowing the ease of ex vivo testing [3]. This work presents the results from complete viscoelastic testing of whole-perfused livers with surgically relevant time-dependant indentation loading profiles to 35% nominal strain. These results will aid in the development of a constitutive model for the liver whose parameters can be related to the physical constituents of the tissue. As an intermediate modeling step, a 1D rheological modeling tool was used to identify the form and initial parameters for a constitutive model.

scholarly journals Characterization of rat tail lymphatic contractility and biomechanics: incorporating nitric oxide-mediated vasoregulation

2020 ◽  
Vol 17 (170) ◽  
pp. 20200598 ◽  
Author(s):  
Mohammad S. Razavi ◽  
J. Brandon Dixon ◽  
Rudolph L. Gleason
Keyword(s):  
Nitric Oxide ◽  
Mechanical Response ◽  
Contractile Function ◽  
Ex Vivo ◽  
Biomechanical Model ◽  
Biomechanical Models ◽  
Lymphatic Pumping ◽  
Rat Tail ◽  
Lymphatic Contractility

The lymphatic system transports lymph from the interstitial space back to the great veins via a series of orchestrated contractions of chains of lymphangions. Biomechanical models of lymph transport, validated with ex vivo or in vivo experimental results, have proved useful in revealing novel insight into lymphatic pumping; however, a need remains to characterize the contributions of vasoregulatory compounds in these modelling tools. Nitric oxide (NO) is a key mediator of lymphatic pumping. We quantified the active contractile and passive biaxial biomechanical response of rat tail collecting lymphatics and changes in the contractile response to the exogenous NO administration and integrated these findings into a biomechanical model. The passive mechanical response was characterized with a three-fibre family model. Nonlinear regression and non-parametric bootstrapping were used to identify best-fit material parameters to passive cylindrical biaxial mechanical data, assessing uniqueness and parameter confidence intervals; this model yielded a good fit ( R 2 = 0.90). Exogenous delivery of NO via sodium nitroprusside (SNP) elicited a dose-dependent suppression of contractions; the amplitude of contractions decreased by 30% and the contraction frequency decreased by 70%. Contractile function was characterized with a modified Rachev–Hayashi model, introducing a parameter that is related to SNP concentration; the model provided a good fit ( R 2 = 0.89) to changes in contractile responses to varying concentrations of SNP. These results demonstrated the significant role of NO in lymphatic pumping and provide a predictive biomechanical model to integrate the combined effect of mechanical loading and NO on lymphatic contractility and mechanical response.

P146. T2 Relaxation Time: In Vivo Quantitative Method to Measure Disc Hydration

2007 ◽  
Vol 7 (5) ◽  
pp. 150S
Author(s):  
Paul Anderson ◽  
Victor Haughton ◽  
Donna Blankenbaker ◽  
Nick Marinelli
Keyword(s):  
Relaxation Time ◽  
Quantitative Method ◽  
T2 Relaxation Time ◽  
T2 Relaxation

The Development of Non-Radiative Probes for In Vivo Applications

2003 ◽  
Author(s):  
Andrew Tsourkas ◽  
Lee Josephson ◽  
Ralph Weissleder
Keyword(s):  
Relaxation Time ◽  
Magnetic Relaxation ◽  
Magnetic Particles ◽  
Superparamagnetic Iron Oxide ◽  
Great Promise ◽  
T2 Relaxation Time ◽  
T2 Relaxation ◽  
Fluorescence Measurements

Recently, the field of activatable probes has been extended from fluorescence to magnetic resonance (MR). Magnetic relaxation switches take advantage of the change in T2 relaxation time that occurs upon binding of multiple bioconjugated superparamagnetic iron-oxide nanoparticles to a target. Here, we use a model system to detect biotinilated BSA using switchable magnetic particles. The presence of the biotinilated BSA results in the aggregation of nanoparticles and leas to a substantial decrease in the T2 relaxation time. Magnetic relaxation switches show great promise for clinical in vitro diagnostics and in vivo imaging since changes in T2 are independent of the sample medium. Tests can be performed in turbid solutions without loss of sensitivity, unlike with fluorescence measurements.

In Vivo Evaluation of Wrist Cartilage Integrity Using T2 Relaxation Time After Scapholunate Ligament Injury and Surgical Repair

2012 ◽  
Author(s):  
Isaac D. Chappell ◽  
Phil Lee ◽  
Terence E. McIff ◽  
E. Bruce Toby ◽  
Kenneth J. Fischer
Keyword(s):  
Relaxation Time ◽  
Water Content ◽  
Soft Tissues ◽  
Free Water ◽  
Surrounding Tissue ◽  
Ligament Injury ◽  
T2 Relaxation Time ◽  
T2 Relaxation ◽  
In Vivo Evaluation

Osteoarthritis (OA) is a serious and frequently occuring outcome of untreated scapholunate dissocation, the most common form of carpal instability in the wrist [1]. As cartilage degenerates, the water content of surrounding tissue becomes less bound. Magnetic resonance imaging (MRI) T2 relaxation time is longer when water content is less bound [2]. MRI offers the advantageous combination of detailed images of soft tissues such as cartilage with the ability to evaluate free water content. Contrasting the various T2 relaxation times found in the cartilage of healthy wrist surfaces with those of injured wrists is thereby proposed as a method of evaluating cartilage degeneration. We hypothesized that T2 values obtained would be longer for the cartilage of the injured wrists. Though surgical treatment may relieve pain and restore some function to the wrist, it is hypothesized that T2 relaxation time will remain increased after surgery as cartilage regeneration is a very slow process, if it happens at all. The goal of this research is to provide a method to evaluate the biochemical and infer the biomechanical integrity of cartilage for various cartilage surfaces in a wrist after injury.

In Vivo Observations of Hydraulic Stiffening in the Canine Femoral Head

1997 ◽  
Vol 119 (1) ◽  
pp. 103-108 ◽  
Author(s):  
J. A. Ochoa ◽  
A. P. Sanders ◽  
T. W. Kiesler ◽  
D. A. Heck ◽  
J. P. Toombs ◽  
...  
Keyword(s):  
Femoral Head ◽  
Femoral Neck ◽  
Boundary Conditions ◽  
Mechanical Response ◽  
Ex Vivo ◽  
Femoral Cortex ◽  
Hind Limbs ◽  
Femoral Heads ◽  
Fluid Boundary

The role that intertrabecular contents and their boundary conditions have on the dynamic mechanical response of canine femoral heads was investigated in vivo. Femoral heads from paired intact hind limbs of canine specimens were subjected to a sinusoidal strain excitation, at physiologic frequencies, in the cranio-caudal direction. The fluid boundary conditions for the contralateral limbs were changed by predrilling through the lateral femoral cortex and into the femoral neck. The drilling procedure did not invade the head itself. This femoral head fluid boundary alteration reduced the stiffness by 19 percent for testing at 1 Hz. The results of this study demonstrate that fluid stiffening occurs in vivo as previously observed ex vivo.

scholarly journals Magnetic Resonance Imaging of Atherosclerosis Using CD81-Targeted Microparticles of Iron Oxide in Mice

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Fei Yan ◽  
Wei Yang ◽  
Xiang Li ◽  
Hongmei Liu ◽  
Xiang Nan ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Relaxation Time ◽  
Iron Oxide ◽  
Magnetic Resonance ◽  
T2 Relaxation Time ◽  
Resonance Imaging ◽  
T2 Relaxation ◽  
Atherosclerotic Lesions ◽  
Deficient Mice

The goal of this study is to investigate the feasibility of using CD81- (Cluster of Differentiation 81 protein-) targeted microparticles of iron oxide (CD81-MPIO) for magnetic resonance imaging (MRI) of the murine atherosclerosis. CD81-MPIO and IgG- (Immunoglobulin G-) MPIO were prepared by covalently conjugating, respectively, with anti-CD81 monoclonal and IgG antibodies to the surface of the tosyl activated MPIO. The relevant binding capability of the MPIO was examined by incubating them with murine bEnd.3 cells stimulated with phenazine methosulfate (PMS) and its effect in shortening T2 relaxation time was also examined. MRI in apolipoprotein E-deficient mice was studied in vivo. Our results show that CD81-MPIO, but not IgG-MPIO, can bind to the PMS-stimulated bEnd.3 cells. The T2 relaxation time was significantly shortened for stimulated bEnd.3 cells when compared with IgG-MPIO. In vivo MRI in apolipoprotein E-deficient mice showed highly conspicuous areas of low signal after CD81-MPIO injection. Quantitative analysis of the area of CD81-MPIO contrast effects showed 8.96- and 6.98-fold increase in comparison with IgG-MPIO or plain MPIO, respectively (P<0.01). Histological assay confirmed the expression of CD81 and CD81-MPIO binding onto atherosclerotic lesions. In conclusion, CD81-MPIO allows molecular assessment of murine atherosclerotic lesions by magnetic resonance imaging.

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