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A study on the theoretical and practical accuracy of conoscopic holography-based surface measurements: toward image registration in minimally invasive surgery.
Burgner J, Simpson AL, Fitzpatrick JM, Lathrop RA, Herrell SD, Miga MI, Webster RJ
(2013) Int J Med Robot 9: 190-203
MeSH Terms: Computer-Aided Design, Equipment Design, Equipment Failure Analysis, Holography, Imaging, Three-Dimensional, Laparoscopy, Lasers, Minimally Invasive Surgical Procedures, Reproducibility of Results, Robotics, Sensitivity and Specificity, Subtraction Technique, Surgery, Computer-Assisted
Show Abstract · Added May 27, 2014
BACKGROUND - Registered medical images can assist with surgical navigation and enable image-guided therapy delivery. In soft tissues, surface-based registration is often used and can be facilitated by laser surface scanning. Tracked conoscopic holography (which provides distance measurements) has been recently proposed as a minimally invasive way to obtain surface scans. Moving this technique from concept to clinical use requires a rigorous accuracy evaluation, which is the purpose of our paper.
METHODS - We adapt recent non-homogeneous and anisotropic point-based registration results to provide a theoretical framework for predicting the accuracy of tracked distance measurement systems. Experiments are conducted a complex objects of defined geometry, an anthropomorphic kidney phantom and a human cadaver kidney.
RESULTS - Experiments agree with model predictions, producing point RMS errors consistently < 1 mm, surface-based registration with mean closest point error < 1 mm in the phantom and a RMS target registration error of 0.8 mm in the human cadaver kidney.
CONCLUSIONS - Tracked conoscopic holography is clinically viable; it enables minimally invasive surface scan accuracy comparable to current clinical methods that require open surgery.
Copyright © 2012 John Wiley & Sons, Ltd.
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13 MeSH Terms
Fiber-to-chip coupler designed using an optical transformation.
Markov P, Valentine JG, Weiss SM
(2012) Opt Express 20: 14705-13
MeSH Terms: Electronics, Equipment Design, Equipment Failure Analysis, Fiber Optic Technology, Optical Devices, Silicon, Surface Plasmon Resonance, Transducers
Show Abstract · Added April 27, 2017
An integrated silicon photonics coupler for fiber to waveguide conversion was designed employing a transformation optics approach. Quasi-conformal mapping was used to obtain achievable material properties, which were realized by a distorted hexagonal lattice of air holes in silicon. The coupler, measuring only 10 μm in length and fabricated with a single-step lithography process, exhibits a peak simulated transmission efficiency of nearly 100% for in-plane mode conversion and a factor of 5 improvement over butt coupling for fiber to waveguide mode conversion in experimental testing.
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8 MeSH Terms
Fabrication of a hybrid microfluidic system incorporating both lithographically patterned microchannels and a 3D fiber-formed microfluidic network.
Bellan LM, Kniazeva T, Kim ES, Epshteyn AA, Cropek DM, Langer R, Borenstein JT
(2012) Adv Healthc Mater 1: 164-7
MeSH Terms: Dimethylpolysiloxanes, Equipment Design, Equipment Failure Analysis, Microfluidic Analytical Techniques, Molecular Imprinting, Photography
Show Abstract · Added March 18, 2020
A device containing a 3D microchannel network (fabricated using sacrificial melt-spun microfibers) sandwiched between lithographically patterned microfluidic channels offers improved delivery of soluble compounds to a large volume compared to a simple stack of two microfluidic channel layers. With this improved delivery ability comes an increased fluidic resistance due to the tortuous network of small-diameter channels.
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MeSH Terms
A large volume double channel 1H-X RF probe for hyperpolarized magnetic resonance at 0.0475 T.
Coffey AM, Shchepin RV, Wilkens K, Waddell KW, Chekmenev EY
(2012) J Magn Reson 220: 94-101
MeSH Terms: Equipment Design, Equipment Failure Analysis, Magnetic Resonance Spectroscopy, Magnetics, Protons, Transducers
Show Abstract · Added March 5, 2014
In this work we describe a large volume 340 mL (1)H-X magnetic resonance (MR) probe for studies of hyperpolarized compounds at 0.0475 T. (1)H/(13)C and (1)H/(15)N probe configurations are demonstrated with the potential for extension to (1)H/(129)Xe. The primary applications of this probe are preparation and quality assurance of (13)C and (15)N hyperpolarized contrast agents using PASADENA (parahydrogen and synthesis allow dramatically enhanced nuclear alignment) and other parahydrogen-based methods of hyperpolarization. The probe is efficient and permits 62 μs (13)C excitation pulses at 5.3 W, making it suitable for portable operation. The sensitivity and detection limits of this probe, tuned to (13)C, are compared with a commercial radio frequency (RF) coil operating at 4.7 T. We demonstrate that low field MR of hyperpolarized contrast agents could be as sensitive as conventional high field detection and outline potential improvements and optimization of the probe design for preclinical in vivo MRI. PASADENA application of this low-power probe is exemplified with (13)C hyperpolarized 2-hydroxyethyl propionate-1-(13)C,2,3,3-d(3).
Copyright © 2012 Elsevier Inc. All rights reserved.
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6 MeSH Terms
Design and evaluation of an optically-tracked single-CCD laser range scanner.
Pheiffer TS, Simpson AL, Lennon B, Thompson RC, Miga MI
(2012) Med Phys 39: 636-42
MeSH Terms: Equipment Design, Equipment Failure Analysis, Feedback, Image Enhancement, Imaging, Three-Dimensional, Lasers, Optical Devices, Reproducibility of Results, Sensitivity and Specificity, Signal Processing, Computer-Assisted
Show Abstract · Added May 27, 2014
PURPOSE - Acquisition of laser range scans of an organ surface has the potential to efficiently provide measurements of geometric changes to soft tissue during a surgical procedure. A laser range scanner design is reported here which has been developed to drive intraoperative updates to conventional image-guided neurosurgery systems.
METHODS - The scanner is optically-tracked in the operating room with a multiface passive target. The novel design incorporates both the capture of surface geometry (via laser illumination) and color information (via visible light collection) through a single-lens onto the same charge-coupled device (CCD). The accuracy of the geometric data was evaluated by scanning a high-precision phantom and comparing relative distances between landmarks in the scans with the corresponding ground truth (known) distances. The range-of-motion of the scanner with respect to the optical camera was determined by placing the scanner in common operating room configurations while sampling the visibility of the reflective spheres. The tracking accuracy was then analyzed by fixing the scanner and phantom in place, perturbing the optical camera around the scene, and observing variability in scan locations with respect to a tracked pen probe ground truth as the camera tracked the same scene from different positions.
RESULTS - The geometric accuracy test produced a mean error and standard deviation of 0.25 ± 0.40 mm with an RMS error of 0.47 mm. The tracking tests showed that the scanner could be tracked at virtually all desired orientations required in the OR set up, with an overall tracking error and standard deviation of 2.2 ± 1.0 mm with an RMS error of 2.4 mm. There was no discernible difference between any of the three faces on the lasers range scanner (LRS) with regard to tracking accuracy.
CONCLUSIONS - A single-lens laser range scanner design was successfully developed and implemented with sufficient scanning and tracking accuracy for image-guided surgery.
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10 MeSH Terms
Mapping small intestine bioelectrical activity using high-resolution printed-circuit-board electrodes.
Angeli TR, O'Grady G, Erickson JC, Du P, Paskaranandavadivel N, Bissett IP, Cheng LK, Pullan AJ
(2011) Conf Proc IEEE Eng Med Biol Soc 2011: 4951-4
MeSH Terms: Animals, Electrodes, Electromyography, Equipment Design, Equipment Failure Analysis, Female, Myoelectric Complex, Migrating, Reproducibility of Results, Sensitivity and Specificity, Swine
Show Abstract · Added April 26, 2016
In this study, novel methods were developed for the in-vivo high-resolution recording and analysis of small intestine bioelectrical activity, using flexible printed-circuit-board (PCB) electrode arrays. Up to 256 simultaneous recordings were made at multiple locations along the porcine small intestine. Data analysis was automated through the application and tuning of the Falling-Edge Variable-Threshold algorithm, achieving 92% sensitivity and a 94% positive-predictive value. Slow wave propagation patterns were visualized through the automated generation of animations and isochronal maps. The methods developed and validated in this study are applicable for use in humans, where future studies will serve to improve the clinical understanding of small intestine motility in health and disease.
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10 MeSH Terms
A pulsed injection parahydrogen generator and techniques for quantifying enrichment.
Feng B, Coffey AM, Colon RD, Chekmenev EY, Waddell KW
(2012) J Magn Reson 214: 258-62
MeSH Terms: Equipment Design, Equipment Failure Analysis, Hydrogen, Magnetic Resonance Spectroscopy, Microfluidics
Show Abstract · Added March 5, 2014
A device is presented for efficiently enriching parahydrogen by pulsed injection of ambient hydrogen gas. Hydrogen input to the generator is pulsed at high pressure to a catalyst chamber making thermal contact with the cold head of a closed-cycle cryocooler maintained between 15 and 20K. The system enables fast production (0.9 standard liters per minute) and allows for a wide range of production targets. Production rates can be systematically adjusted by varying the actuation sequence of high-pressure solenoid valves, which are controlled via an open source microcontroller to sample all combinations between fast and thorough enrichment by varying duration of hydrogen contact in the catalyst chamber. The entire enrichment cycle from optimization to quantification and storage kinetics are also described. Conversion of the para spin-isomer to orthohydrogen in borosilicate tubes was measured at 8 min intervals over a period of 64 h with a 12 T NMR spectrometer. These relaxation curves were then used to extract initial enrichment by exploiting the known equilibrium (relaxed) distribution of spin isomers with linear least squares fitting to a single exponential decay curve with an estimated error less than or equal to 1%. This procedure is time-consuming, but requires only one sample pressurized to atmosphere. Given that tedious matching to external references are unnecessary with this procedure, we find it to be useful for periodic inspection of generator performance. The equipment and procedures offer a variation in generator design that eliminate the need to meter flow while enabling access to increased rates of production. These tools for enriching and quantifying parahydrogen have been in steady use for 3 years and should be helpful as a template or as reference material for building and operating a parahydrogen production facility.
Copyright © 2011 Elsevier Inc. All rights reserved.
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5 MeSH Terms
Potential of discrete Gaussian edge feathering method for improving abutment dosimetry in eMLC-delivered segmented-field electron conformal therapy.
Eley JG, Hogstrom KR, Matthews KL, Parker BC, Price MJ
(2011) Med Phys 38: 6610-22
MeSH Terms: Algorithms, Cluster Analysis, Computer-Aided Design, Electrons, Equipment Design, Equipment Failure Analysis, Feasibility Studies, Learning, Normal Distribution, Radiometry, Radiotherapy, Conformal, Reproducibility of Results, Sensitivity and Specificity
Show Abstract · Added March 30, 2020
PURPOSE - The purpose of this work was to investigate the potential of discrete Gaussian edge feathering of the higher energy electron fields for improving abutment dosimetry in the planning volume when using an electron multileaf collimator (eMLC) to deliver segmented-field electron conformal therapy (ECT).
METHODS - A discrete (five-step) Gaussian edge spread function was used to match dose penumbras of differing beam energies (6-20 MeV) at a specified depth in a water phantom. Software was developed to define the leaf eMLC positions of an eMLC that most closely fit each electron field shape. The effect of 1D edge feathering of the higher energy field on dose homogeneity was computed and measured for segmented-field ECT treatment plans for three 2D PTVs in a water phantom, i.e., depth from the water surface to the distal PTV surface varied as a function of the x-axis (parallel to leaf motion) and remained constant along the y-axis (perpendicular to leaf motion). Additionally, the effect of 2D edge feathering was computed and measured for one radially symmetric, 3D PTV in a water phantom, i.e., depth from the water surface to the distal PTV surface varied as a function of both axes. For the 3D PTV, the feathering scheme was evaluated for 0.1-1.0-cm leaf widths. Dose calculations were performed using the pencil beam dose algorithm in the Pinnacle(3) treatment planning system. Dose verification measurements were made using a prototype eMLC (1-cm leaf width).
RESULTS - 1D discrete Gaussian edge feathering reduced the standard deviation of dose in the 2D PTVs by 34, 34, and 39%. In the 3D PTV, the broad leaf width (1 cm) of the eMLC hindered the 2D application of the feathering solution to the 3D PTV, and the standard deviation of dose increased by 10%. However, 2D discrete Gaussian edge feathering with simulated eMLC leaf widths of 0.1-0.5 cm reduced the standard deviation of dose in the 3D PTV by 33-28%, respectively.
CONCLUSIONS - A five-step discrete Gaussian edge spread function applied in 2D improves the abutment dosimetry but requires an eMLC leaf resolution better than 1 cm.
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MeSH Terms
Phase-contrast digital tomosynthesis.
Hammonds JC, Price RR, Donnelly EF, Pickens DR
(2011) Med Phys 38: 2353-8
MeSH Terms: Algorithms, Equipment Design, Equipment Failure Analysis, Image Enhancement, Image Interpretation, Computer-Assisted, Radiographic Image Enhancement, Reproducibility of Results, Sensitivity and Specificity, Tomography, X-Ray Computed
Show Abstract · Added February 28, 2014
PURPOSE - Phase-contrast (PC) edge enhancement occurs at the boundary between different tissues and is an interference effect that results from the differential phase-shifts that the x-rays acquire while traversing the two tissues. While observable in planar phase-contrast radiographs, the impact of digital tomosynthesis on this edge enhancement effect has not been previously reported. The purpose of this work is to demonstrate: (1) that phase-contrast digital tomosynthesis (PC-DTS) is possible with a conventional x-ray source, (2) that the reconstructed tomosynthesis images demonstrate and retain edge enhancement as compared to planar phase-contrast radiographs and (3) tomosynthesis improves object contrast by reducing the effects of superimposed structures.
METHODS - An unmodified, commercially available cabinet x-ray system (Faxitron LX-60) was used. The system contains a tungsten anode x-ray tube that was operated at 24 kVp and 3 mAs for each PC radiographic image taken, with a nominal focal spot size of 0.010 mm. The digital detector uses CsI/CMOS with a pixel size of 0.054 mm x 0.054 mm. Objects to be imaged were attached to a computer-controlled rotating motor and are rotated +/- 25 degrees about a central position in one degree increments. At each increment, three phase-contrast radiographs are taken and then averaged to reduce the effect of noise. These planar images are then used to reconstruct a series of 56 longitudinal tomographic images with an image offset increment of about 0.7 mm.
RESULTS - Tomographic z-plane resolution was measured to be approximately 4 mm. When compared to planar PC images, the tomosynthesis images were shown to retain the PC boundary edge enhancement in addition to an improvement in object contrast.
CONCLUSIONS - Our work demonstrates that PC digital tomosynthesis retains the edge-enhancement observed in planar PC radiograph and further improves soft-tissue conspicuity by reducing the effects of superimposed tissue structure.
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9 MeSH Terms
Integrated system for combined Raman spectroscopy-spectral domain optical coherence tomography.
Patil CA, Kalkman J, Faber DJ, Nyman JS, van Leeuwen TG, Mahadevan-Jansen A
(2011) J Biomed Opt 16: 011007
MeSH Terms: Animals, Computer-Aided Design, Equipment Design, Equipment Failure Analysis, Lighting, Mice, Reproducibility of Results, Sensitivity and Specificity, Spectrum Analysis, Raman, Systems Integration, Tomography, Optical Coherence
Show Abstract · Added March 24, 2014
Raman spectroscopy (RS) and optical coherence tomography (OCT) are powerful tools for optical analysis of tissues with mutually complementary strengths and limitations. OCT excels at visualizing tissue microstructure but lacks molecular specificity, while RS can relay tissue biochemical composition but typically cannot relate microstructure. Previous implementations of combined RS-OCT have utilized a common sample arm while maintaining independent RS and OCT detection arms. We present the design and application of an integrated RS-OCT instrument with a common detection arm for both RS and OCT. The detector is a spectrograph capable of sequential detection of the 855-nm OCT signal and the Raman scatter generated by a 785-nm source. The capabilities of the instrument are demonstrated ex vivo in the calvaria and retina of rodents, as well as in vivo in human skin.
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11 MeSH Terms