Effect of Voxel Size on Finite-Element Analysis of Micro-CT Derived Bone Sample

Introduction: Bone strength is dependent on the structural parameters of thetrabecular micro-architecture1. A method to estimate bone strength is finite element(FE) analysis of the bone micro-architecture2. Quantification of structural parameters3and FE analysis results are dependent on the image resolution2. This study used microcomputedtomography (micro-CT) to investigate how voxel size affects the accuracy oftrabecular bone measurements, particularly regarding how it relates to FE modelingprediction of bone strength.Methods: Cadaveric bovine cubic bones were imaged at an isotropic voxel sizeof 20mm using a micro-CT scanner (Micro-CT35). Images were segmented using athreshold based technique and re-scaled to voxel sizes 2-4 times larger (40mm-80mm)than the original images. Three-dimensional analyses of trabecular bone propertieswere quantified within the images of the bone cubes. Image voxels were converted tohexahedral elements for FE analysis. Uniaxial 1% compression test was performed onall data (FAIM 5.4). Nodes on the bottom surface were fixed while the top surface wassubjected to compression. No constraints were applied to the x and y directions.Results: Trabecular number (TbN) measurements increased linearly with increasingresolution. There was a 22.11% difference between trabecular number values at20mm versus 80mm. All other structural parameters were not statistically significantbetween different image resolutions (p > 0.05). For FE analysis, there was a 3.05%percent difference for mean von-Mises Stress at 20mm versus 80mm. Total reactionforce between 20mm and 80mm differed by 0.484%. Maximum von-Mises stress wasstatistically significantly different between 20mm and 80mm.Conclusion: All structural parameters except TbN measured at 20mm are comparableto 80mm. Similarly, bone strength estimates through FE analysis at 20mm arecomparable to 80mm. It is unlikely that TbN influenced the bone strength estimates.These results will allow for non-invasive estimate of bone strength with advancedclinical CT scanners

Development of a Tissue Oxygen Saturation Detection System for Improving Surgical Training

Delicate tissue encountered in surgery is prone to ischemic damage from grasping and retracting especially by novice surgeons. Currently, there are no existing techniques to quantitatively assess tissue health during surgical maneuver. A transmission and reflectance mode tissue oxygenation (StO2) sensor was developed and integrated into a standard laparoscopic tool and custom forceps to continuously measure tissue oxygenation during surgery. Numerous wavelengths including 470nm, 500nm, 510nm, 560nm, 570nm, 586nm, 660nm and 940nm were tested in reflection mode while 660nm and 940nm were tested in transmission mode. StO2 sensor successfully detected oxygenation changes on the finger and during ex vivo experiment conducted on arterial and venous blood samples. StO2 sensor was unable to monitor changes when grasping small intestine and liver using surgical instruments. Various factors including lack of hemoglobin at the site of measurement, tissue thickness changes during grasps, and motion artifacts limited the use of this technology.M.H.Sc

Development of a Tissue Oxygen Saturation Detection System for Improving Surgical Training

Delicate tissue encountered in surgery is prone to ischemic damage from grasping and retracting especially by novice surgeons. Currently, there are no existing techniques to quantitatively assess tissue health during surgical maneuver. A transmission and reflectance mode tissue oxygenation (StO2) sensor was developed and integrated into a standard laparoscopic tool and custom forceps to continuously measure tissue oxygenation during surgery. Numerous wavelengths including 470nm, 500nm, 510nm, 560nm, 570nm, 586nm, 660nm and 940nm were tested in reflection mode while 660nm and 940nm were tested in transmission mode. StO2 sensor successfully detected oxygenation changes on the finger and during ex vivo experiment conducted on arterial and venous blood samples. StO2 sensor was unable to monitor changes when grasping small intestine and liver using surgical instruments. Various factors including lack of hemoglobin at the site of measurement, tissue thickness changes during grasps, and motion artifacts limited the use of this technology.M.H.Sc

Development of a Tissue Oxygen Saturation Detection System for Improving Surgical Training

Delicate tissue encountered in surgery is prone to ischemic damage from grasping and retracting especially by novice surgeons. Currently, there are no existing techniques to quantitatively assess tissue health during surgical maneuver. A transmission and reflectance mode tissue oxygenation (StO2) sensor was developed and integrated into a standard laparoscopic tool and custom forceps to continuously measure tissue oxygenation during surgery. Numerous wavelengths including 470nm, 500nm, 510nm, 560nm, 570nm, 586nm, 660nm and 940nm were tested in reflection mode while 660nm and 940nm were tested in transmission mode. StO2 sensor successfully detected oxygenation changes on the finger and during ex vivo experiment conducted on arterial and venous blood samples. StO2 sensor was unable to monitor changes when grasping small intestine and liver using surgical instruments. Various factors including lack of hemoglobin at the site of measurement, tissue thickness changes during grasps, and motion artifacts limited the use of this technology.M.H.Sc

Development of a Tissue Oxygen Saturation Detection System for Improving Surgical Training

Delicate tissue encountered in surgery is prone to ischemic damage from grasping and retracting especially by novice surgeons. Currently, there are no existing techniques to quantitatively assess tissue health during surgical maneuver. A transmission and reflectance mode tissue oxygenation (StO2) sensor was developed and integrated into a standard laparoscopic tool and custom forceps to continuously measure tissue oxygenation during surgery. Numerous wavelengths including 470nm, 500nm, 510nm, 560nm, 570nm, 586nm, 660nm and 940nm were tested in reflection mode while 660nm and 940nm were tested in transmission mode. StO2 sensor successfully detected oxygenation changes on the finger and during ex vivo experiment conducted on arterial and venous blood samples. StO2 sensor was unable to monitor changes when grasping small intestine and liver using surgical instruments. Various factors including lack of hemoglobin at the site of measurement, tissue thickness changes during grasps, and motion artifacts limited the use of this technology.M.H.Sc

A Miniaturized Platform for Multiplexed Drug Response Imaging in Live Tumors

By observing the activity of anti-cancer agents directly in tumors, there is potential to greatly expand our understanding of drug response and develop more personalized cancer treatments. Implantable microdevices (IMD) have been recently developed to deliver microdoses of chemotherapeutic agents locally into confined regions of live tumors; the tissue can be subsequently removed and analyzed to evaluate drug response. This method has the potential to rapidly screen multiple drugs, but requires surgical tissue removal and only evaluates drug response at a single timepoint when the tissue is excised. Here, we describe a “lab-in-a-tumor” implantable microdevice (LIT-IMD) platform to image cell-death drug response within a live tumor, without requiring surgical resection or tissue processing. The LIT-IMD is inserted into a live tumor and delivers multiple drug microdoses into spatially discrete locations. In parallel, it locally delivers microdose levels of a fluorescent cell-death assay, which diffuses into drug-exposed tissues and accumulates at sites of cell death. An integrated miniaturized fluorescence imaging probe images each region to evaluate drug-induced cell death. We demonstrate ability to evaluate multi-drug response over 8 h using murine tumor models and show correlation with gold-standard conventional fluorescence microscopy and histopathology. This is the first demonstration of a fully integrated platform for evaluating multiple chemotherapy responses in situ. This approach could enable a more complete understanding of drug activity in live tumors, and could expand the utility of drug-response measurements to a wide range of settings where surgery is not feasible

A Miniaturized Platform for Multiplexed Drug Response Imaging in Live Tumors

By observing the activity of anti-cancer agents directly in tumors, there is potential to greatly expand our understanding of drug response and develop more personalized cancer treatments. Implantable microdevices (IMD) have been recently developed to deliver microdoses of chemotherapeutic agents locally into confined regions of live tumors; the tissue can be subsequently removed and analyzed to evaluate drug response. This method has the potential to rapidly screen multiple drugs, but requires surgical tissue removal and only evaluates drug response at a single timepoint when the tissue is excised. Here, we describe a “lab-in-a-tumor” implantable microdevice (LIT-IMD) platform to image cell-death drug response within a live tumor, without requiring surgical resection or tissue processing. The LIT-IMD is inserted into a live tumor and delivers multiple drug microdoses into spatially discrete locations. In parallel, it locally delivers microdose levels of a fluorescent cell-death assay, which diffuses into drug-exposed tissues and accumulates at sites of cell death. An integrated miniaturized fluorescence imaging probe images each region to evaluate drug-induced cell death. We demonstrate ability to evaluate multi-drug response over 8 h using murine tumor models and show correlation with gold-standard conventional fluorescence microscopy and histopathology. This is the first demonstration of a fully integrated platform for evaluating multiple chemotherapy responses in situ. This approach could enable a more complete understanding of drug activity in live tumors, and could expand the utility of drug-response measurements to a wide range of settings where surgery is not feasible