This study was approved by the Institutional Review Board of our institution (approval number: 20150128).

All methods described here have been approved by the Institutional Review Board of Keio University School of Medicine.
NOTE: Joint kinematics are measured by reconstructing the motion of a moving bone around a fixed bone. For knee joint kinematics, the femur is defined as the fixed bone and the tibia is defined as the moving bone.
1. CT imaging protocol
<ol>
	<li>Set up the CT machine. Acquire CT examinations with a 320-detector-row CT system to allow for multiple phases of 3D volume data with 160 mm craniocaudal coverage. For example, in the analysis of knee kinematics, the image acquisition consists of 51 volume scans with a rotation time of 0.275 s, and all images are reconstructed using half reconstruction, so that the temporal resolution is approximately 0.16 s.</li>
	<li>Use the following scanning parameters: peak tube voltage = 100 kVp; tube current = 40 mA; scan coverage = 160 mm; matrix size= 512 x 512 pixels; and reconstruction section thickness and section interval = 0.5 mm.</li>
	<li>Place the target joint of the subject inside the CT gantry in the starting position of the 4DCT exam (Figure 1).</li>
	<li>Before the CT exam, rehearse movements of the joint from the start position to the end position within the required examination time. Ask the subject to move the joint during the 10.275 s scan time and obtain a series of volume data. Store the sequential volume data in DICOM format.</li>
	<li>Perform static 3DCT of all the target bones and store the data in DICOM format.</li>
</ol>
2. Surface reconstruction
<ol>
	<li>Perform semiautomatic segmentation of 3DCT data (Figure 2A).
	<ol>
		<li>Load CT DICOM data by selecting all DICOM files of the static 3DCT data.</li>
		<li>Open the label field by clicking Edit New Label Field and check which threshold CT attenuation value is appropriate to extract cortical bone from the source bone. Select materials with CT attenuation values above the threshold. For example, the bone cortex threshold for a young subject is set as 250. Check the label for bone cortex selection and manually modify the demarcation using an editing tool for consistency with the shape of the bone.</li>
		<li>Generate the surface data (triangle meshes) from the labeled bone cortex position data (point cloud in the software). Store the surface data by exporting data in Standard Triangulated Language (STL) format.</li>
		<li>Click Generate Surface|Apply on the label of the cortical bone. Click File|Export Data As|STL Binary Little Endian to save the surface data in STL format.</li>
	</ol>
	</li>
	<li>Perform automatic segmentation of 4DCT volume data (Figure 2B). 
	NOTE: Each frame of the DICOM data includes the distribution of the CT attenuation values in the CT gantry.
	<ol>
		<li>Set the threshold of the bone cortex as in static CT, and extract geometric data showing CT attenuation values above the threshold from all 51 frames of the 4DCT data using the DICOM reading module in the programming software. Adjust the threshold according to the bone density of the source bone. For example, for the osteoporotic bone, set the threshold lower.</li>
		<li>Translate all positional data that have already been obtained in the previous step into a format that can be interpreted by image processing software (e.g., Avizo). In the image processing software, reconstruct all surface data of the point cloud with higher CT attenuation values than the threshold for all 4DCT frames using a batch processing script. The image processing software contains the function to read the script and export the surface data from the DICOM series data automatically. The batch script is shown in the Supplemental Coding File.</li>
	</ol>
	</li>
</ol>
3. Image registration
NOTE: In this step, reconstruct the motions of the moving bone with respect to the fixed bone from the raw 4DCT DICOM data.
<ol>
	<li>Perform surface registration from static 3DCT to the first frame of the 4DCT.
	<ol>
		<li>Trim the bones in a static 3DCT into partial segment data that are included in all frames of 4DCT for use with the iterative closest point (ICP) algorithm11 in the 3D mesh editing software using the Selecting Face function (Figure 3A) by referring 4DCT movie data. The surface data from 4DCT are only partial segments that are included in each volume imagebecause surface registration requires that one surface data point is included in another surface.</li>
		<li>Pick three landmarks in the fixed and moving bones that can be easily identified from the trimmed 3DCT surface and the surface data of the first frame of 4DCT in the 3D mesh editing software using the PickPoints function (Figure 3B).</li>
		<li>Match the partial fixed and moving bones roughly on the first frame of the 4DCT surface data (Figure 3C) according to the picked landmarks in 3.1.2. Next, perform surface registration using the ICP algorithm11 using the open source software (e.g., VTK). 
		NOTE: This process provides homogeneous transformation matrices of the fixed and moving bones from the static 3DCT to the first frame of 4DCT (Figure 3D). These matrices are 4 x 4 matrices consisting of rotation and translation, as shown in Figure 4. The transformation matrix causing the reverse action can also be calculated.</li>
	</ol>
	</li>
	<li>Perform sequential surface registration (Figure 5).
	<ol>
		<li>Match the partial surfaces of the fixed and moving bone in the first 4DCT frame onto the surface data of the second frame. Next, match the partial surfaces of the ith frame onto the (i + 1)th frame of 4DCT sequentially. Repeat this process until the last frame of the 4DCT by programming with use of the ICP module in the open source software.</li>
	</ol>
	</li>
	<li>Calculate transformation matrices from the static 3DCT to all frames in 4DCT according to the results of 3.1 and 3.2.</li>
	<li>Reconstruct moving bone motion with respect to the fixed bone (Figure 6).
	<ol>
		<li>Reconstruct the kinematics of the moving bone with respect to the fixed bone from the matrices that represent the transformation from the static 3DCT to each 4DCT frame. Define the coordinate systems of the fixed and moving bones when the rotation parameters are measured (e.g., flexion angle or rotation angle calculated by the Euler/Cardan angle)12,13,14.</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Andriacchi, T. P., Alexander, E. J., Toney, M. K., Dyrby, C., Sum, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+point+cluster+method+for+in+vivo+motion+analysis:+applied+to+a+study+of+knee+kinematics.">A point cluster method for in vivo motion analysis: applied to a study of knee kinematics.</a> Journal of Biomechanical Engineering. 120 (6), 743-749 (1998).</li><li>Corazza, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+markerless+motion+capture+system+to+study+musculoskeletal+biomechanics:+visual+hull+and+simulated+annealing+approach.">A markerless motion capture system to study musculoskeletal biomechanics: visual hull and simulated annealing approach.</a> Annals of Biomedical Engineering. 34 (6), 1019-1029 (2006).</li><li>Reinschmidt, C., van den Bogert, A. J., Nigg, B. M., Lundberg, A., Murphy, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+skin+movement+on+the+analysis+of+skeletal+knee+joint+motion+during+running.">Effect of skin movement on the analysis of skeletal knee joint motion during running.</a> Journal of Biomechanics. 30 (7), 729-732 (1997).</li><li>Burgess, R. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effect+of+a+simulated+scaphoid+malunion+on+wrist+motion.">The effect of a simulated scaphoid malunion on wrist motion.</a> Journal of Hand Surgery. 12 (5 Pt 1), 774-776 (1987).</li><li>Shoemaker, S. C., Markolf, K. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+joint+load+on+the+stiffness+and+laxity+of+ligament-deficient+knees.+An+in+vitro+study+of+the+anterior+cruciate+and+medial+collateral+ligaments.">Effects of joint load on the stiffness and laxity of ligament-deficient knees. An in vitro study of the anterior cruciate and medial collateral ligaments.</a> Journal of Bone and Joint Surgery (American Volume). 67 (1), 136-146 (1985).</li><li>Eckstein, F., Lohe, F., Muller-Gerbl, M., Steinlechner, M., Putz, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stress+distribution+in+the+trochlear+notch.+A+model+of+bicentric+load+transmission+through+joints.">Stress distribution in the trochlear notch. A model of bicentric load transmission through joints.</a> Journal of Bone and Joint Surgery (British Volume). 76 (4), 647-653 (1994).</li><li>Omid, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biomechanical+analysis+of+latissimus+dorsi+tendon+transfer+with+and+without+superior+capsule+reconstruction+using+dermal+allograft.">Biomechanical analysis of latissimus dorsi tendon transfer with and without superior capsule reconstruction using dermal allograft.</a> Journal of Shoulder and Elbow Surgery. 28 (8), 1523-1530 (2019).</li><li>Tsai, T. Y., Lu, T. W., Chen, C. M., Kuo, M. Y., Hsu, H. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+volumetric+model-based+2D+to+3D+registration+method+for+measuring+kinematics+of+natural+knees+with+single-plane+fluoroscopy.">A volumetric model-based 2D to 3D registration method for measuring kinematics of natural knees with single-plane fluoroscopy.</a> Medical Physics. 37 (3), 1273-1284 (2010).</li><li>Ohnishi, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three-dimensional+motion+study+of+femur,+tibia,+and+patella+at+the+knee+joint+from+bi-plane+fluoroscopy+and+CT+images.">Three-dimensional motion study of femur, tibia, and patella at the knee joint from bi-plane fluoroscopy and CT images.</a> Radiological Physics and Technology. 3 (2), 151-158 (2010).</li><li>Dobbe, J. G. G., de Roo, M. G. A., Visschers, J. C., Strackee, S. D., Streekstra, G. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+a+Quantitative+Method+for+Carpal+Motion+Analysis+Using+Clinical+3-D+and+4-D+CT+Protocols.">Evaluation of a Quantitative Method for Carpal Motion Analysis Using Clinical 3-D and 4-D CT Protocols.</a> IEEE Transactions on Medical Imaging. 38 (4), 1048-1057 (2019).</li><li>Besl, P. J., McKay, N. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+method+for+registration+of+3-D+shapes.">A method for registration of 3-D shapes.</a> IEEE Transactions on Pattern Analysis and Machine Intelligence. 14 (2), 239-256 (1992).</li><li>Wu, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ISB+recommendation+on+definitions+of+joint+coordinate+system+of+various+joints+for+the+reporting+of+human+joint+motion--part+I:+ankle,+hip,+and+spine.">ISB recommendation on definitions of joint coordinate system of various joints for the reporting of human joint motion--part I: ankle, hip, and spine.</a> Journal of Biomechanics. 35 (4), 543-548 (2002).</li><li>Wu, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ISB+recommendation+on+definitions+of+joint+coordinate+systems+of+various+joints+for+the+reporting+of+human+joint+motion--Part+II:+shoulder,+elbow,+wrist+and+hand.">ISB recommendation on definitions of joint coordinate systems of various joints for the reporting of human joint motion--Part II: shoulder, elbow, wrist and hand.</a> Journal of Biomechanics. 38 (5), 981-992 (2005).</li><li>Crawford, N. R., Yamaguchi, G. T., Dickman, C. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+technique+for+determining+3-D+joint+angles:+the+tilt/twist+method.">A new technique for determining 3-D joint angles: the tilt/twist method.</a> Clinical Biomechanics (Bristol, Avon). 14 (3), 153-165 (1999).</li><li>Sato, T., Koga, Y., Omori, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three-dimensional+lower+extremity+alignment+assessment+system:+application+to+evaluation+of+component+position+after+total+knee+arthroplasty.">Three-dimensional lower extremity alignment assessment system: application to evaluation of component position after total knee arthroplasty.</a> Journal of Arthroplasty. 19 (5), 620-628 (2004).</li><li>Ishii, Y., Terajima, K., Terashima, S., Koga, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three-dimensional+kinematics+of+the+human+knee+with+intracortical+pin+fixation.">Three-dimensional kinematics of the human knee with intracortical pin fixation.</a> Clinical Orthopaedics and Related Research. (343), 144-150 (1997).</li><li>Asano, T., Akagi, M., Tanaka, K., Tamura, J., Nakamura, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+three-dimensional+knee+kinematics+using+a+biplanar+image-matching+technique.">In vivo three-dimensional knee kinematics using a biplanar image-matching technique.</a> Clinical Orthopaedics and Related Research. (388), 157-166 (2001).</li><li>Saltybaeva, N., Jafari, M. E., Hupfer, M., Kalender, W. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Estimates+of+effective+dose+for+CT+scans+of+the+lower+extremities.">Estimates of effective dose for CT scans of the lower extremities.</a> Radiology. 273 (1), 153-159 (2014).</li><li>Mat Jais, I. S., Tay, S. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Kinematic+analysis+of+the+scaphoid+using+gated+four-dimensional+CT.">Kinematic analysis of the scaphoid using gated four-dimensional CT.</a> Clinical Radiology. 72 (9), e791-e799 (2017).</li><li>Tanaka, M. J., Elias, J. J., Williams, A. A., Demehri, S., Cosgarea, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+patellar+maltracking+using+dynamic+kinematic+CT+imaging+in+patients+with+patellar+instability.">Characterization of patellar maltracking using dynamic kinematic CT imaging in patients with patellar instability.</a> Knee Surgery, Sports Traumatology, Arthroscopy. 24 (11), 3634-3641 (2016).</li><li>Troupis, J. M., Amis, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Four-dimensional+computed+tomography+and+trigger+lunate+syndrome.">Four-dimensional computed tomography and trigger lunate syndrome.</a> Journal of Computer Assisted Tomography. 37 (4), 639-643 (2013).</li><li>Kakar, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Role+of+Dynamic+(4D)+CT+in+the+Detection+of+Scapholunate+Ligament+Injury.">The Role of Dynamic (4D) CT in the Detection of Scapholunate Ligament Injury.</a> Journal of Wrist Surgery. 5 (4), 306-310 (2016).</li><li>Zhao, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+technique+for+quantifying+wrist+motion+using+four-dimensional+computed+tomography:+approach+and+validation.">A technique for quantifying wrist motion using four-dimensional computed tomography: approach and validation.</a> Journal of Biomechanical Engineering. 137 (7), (2015).</li><li>Breighner, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Relative+accuracy+of+spin-image-based+registration+of+partial+capitate+bones.">Relative accuracy of spin-image-based registration of partial capitate bones.</a> in 4DCT of the wrist. Computer Methods in Biomechanics and Biomedical Engineering: Imaging &amp; Visualization. 4 (6), 360-367 (2016).</li><li>Goto, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+pilot+study+evaluating+the+thumb+carpometacarpal+joint+during+circumduction.">In vivo pilot study evaluating the thumb carpometacarpal joint during circumduction.</a> Clinical Orthopaedics and Related Research. 472 (4), 1106-1113 (2014).</li><li>Zhang, X., Jian, L., Xu, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Robust+3D+point+cloud+registration+based+on+bidirectional+Maximum+Correntropy+Criterion.">Robust 3D point cloud registration based on bidirectional Maximum Correntropy Criterion.</a> PloS One. 13 (5), e0197542 (2018).</li><li>Baker, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ISB+recommendation+on+definition+of+joint+coordinate+systems+for+the+reporting+of+human+joint+motion-part+I:+ankle,+hip+and+spine.">ISB recommendation on definition of joint coordinate systems for the reporting of human joint motion-part I: ankle, hip and spine.</a> Journal of Biomechanics. 36 (2), 300-302 (2003).</li><li>Qiu, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Automatic+segmentation+of+the+mandible+from+computed+tomography+scans+for+3D+virtual+surgical+planning+using+the+convolutional+neural+network.">Automatic segmentation of the mandible from computed tomography scans for 3D virtual surgical planning using the convolutional neural network.</a> Physics in Medicine and Biology. , (2019).</li><li>Hemke, R., Buckless, C. G., Tsao, A., Wang, B., Torriani, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Deep+learning+for+automated+segmentation+of+pelvic+muscles,+fat,+and+bone+from+CT+studies+for+body+composition+assessment.">Deep learning for automated segmentation of pelvic muscles, fat, and bone from CT studies for body composition assessment.</a> Skeletal Radiology. , (2019).</li><li>Lee, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Impact+of+scanning+parameters+and+breathing+patterns+on+image+quality+and+accuracy+of+tumor+motion+reconstruction+in+4D+CBCT:+a+phantom+study.">Impact of scanning parameters and breathing patterns on image quality and accuracy of tumor motion reconstruction in 4D CBCT: a phantom study.</a> Journal of Applied Clinical Medical Physics. 16 (6), 195-212 (2015).</li></ol>

The authors have no competing financial interests.

Our method allows visualization and quantification of the motions of whole bones and provides numerical positional data of the moving bone with respect to the fixed bone from 4DCT data. Many tools have been suggested for measuring joint kinematics. Motion skin markers can analyze total body motions over a long time. However, this method contains skin motion errors3. Joint kinematics should be estimated from the motion of adjacent bones. The 2D-3D registration method uses fluoroscopy and infers 3D ...

Joint kinematics have been described using a number of methodologies, such as motion capture sensors, 2D-3D registration, and cadaveric studies. Each method has specific advantages and disadvantages. For example, motion capture sensors can measure fast, large-scale motions using infrared cameras with or without sensors on the subject1,2. However, these methods measure skin motion to infer joint kinematics, and therefore contain skin motion errors3.
Cadaveric studies have been used to evaluate ranges of motion, instability, and contact areas4,5,6. This approach can measure small changes in small joints using CT or optical sensors attached directly to bone using pins or screws. Cadaveric models can mainly evaluate passive motions, although multiple actuators have been used to apply external forces to tendons to simulate dynamic motion7. Active joint motion can be measured by 2D-3D registration techniques, matching 3DCT images to 2D fluoroscopy images. Although the accuracy of the registration process remains controversial, the reported accuracy is generally high enough for large joint kinematics8,9. However, this method cannot be applied to small bones or multiple bones in narrow spaces.
In contrast, 4DCT is a dynamic CT method that obtains a series of volumetric data. Active joint motions can be analyzed using this approach10. This technology provides precise 3D positional data of all substances inside the CT gantry. The 3D joint motions are clearly visualized in a viewer. However, describing joint kinematics from such a series of volume data is still difficult, because all the bones are moving and no landmarks can be traced during the active motions in vivo.
We developed a method for 4DCT analysis that provides the in vivo joint kinematics of the whole bones around the joint during active motions. The aim of this article is to present our method, the sequential 3D-3D registration technique for 4DCT analysis, and show representative results obtained using this method.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>4DCT scanner</td>
			<td>Canon medical systems (Tochigi, Japan)</td>
			<td>N/A</td>
			<td>4DCT scan, Static 3DCT scan</td>
		</tr>
		<tr>
			<td>AVIZO(9.3.0)*</td>
			<td>Thermo Fisher Scientific (OR, USA)</td>
			<td></td>
			<td>Image processing software. 
			Surface reconstruction from CT DICOM data and point cloud data. 
			* Ryan, T. M. &#38; Walker, A. Trabecular bone structure in the humeral and femoral heads of anthropoid primates. Anat Rec (Hoboken). 293 (4), 719-729, doi:10.1002/ar.21139, (2010).</td>
		</tr>
		<tr>
			<td>Meshlab**</td>
			<td>ISTI (Pisa, Italy)</td>
			<td>N/A</td>
			<td>Surface trimming and landmark picking 
			** MeshLab: an Open-Source Mesh Processing Tool. Sixth Eurographics Italian Chapter Conference, page 129-136, 2008. 
			P. Cignoni, M. Callieri, M. Corsini, M. Dellepiane, F. Ganovelli, G. Ranzuglia</td>
		</tr>
		<tr>
			<td>VTK(6.3.0)***</td>
			<td>Kitware (New York, USA)</td>
			<td>N/A</td>
			<td>Iterative Closest Points algorithm. Used in python language programming. 
			*** https://vtk.org</td>
		</tr>
		<tr>
			<td>Python(3.6.1)</td>
			<td>Python Software Foundation</td>
			<td>N/A</td>
			<td>DICOM file processing to extract the point cloud from the bone cortex (&#39;dicom.py&#39; module). 
			Calculation of the rotation matrices. (Numpy module) 
			Sequential image regestration using ICP algorithm</td>
		</tr>
	</tbody>
</table>

four-dimensional ct analysis using sequential 3d-3d registration

Four-dimensional computed tomography (4DCT) provides a series of volume data and visualizes joint motions. However, numerical analysis of 4DCT data remains difficult because segmentation in all volumetric frames is time-consuming. We aimed to analyze joint kinematics using a sequential 3D-3D registration technique to provide the kinematics of the moving bone with respect to the fixed bone semiautomatically using 4DCT DICOM data and existing software. Surface data of the source bones are reconstructed from 3DCT. The trimmed surface data are respectively matched with surface data from the first frame in 4DCT. These trimmed surfaces are sequentially matched until the last frame. These processes provide positional information for target bones in all frames of the 4DCT. Once the coordinate systems of the target bones are decided, translation and rotation angles between any two bones can be calculated. This 4DCT analysis offers advantages in kinematic analyses of complex structures such as carpal or tarsal bones. However, fast or large-scale motions cannot be traced because of motion artifacts.

We describe the motion of the tibia during knee extension. The knee joint was positioned in the CT gantry. A triangle pillow was used to support the femur at the starting position. The knee was extended to a straight position over the course of 10 s. Radiation exposure was measured. In addition to 4DCT, static 3DCT of the whole femur, tibia, and patella was performed. Surface data of the whole femur and tibia were reconstructed. The threshold for HU numbers of the bone cortex was set as 2...

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Four-Dimensional CT Analysis Using Sequential 3D-3D Registration

We analyzed joint kinematics from four-dimensional computed tomography data. The sequential 3D-3D registration method semiautomatically provides the kinematics of the moving bone with respect to the subject bone from four-dimensional computed tomography data.

Four-dimensional computed tomography (4DCT) provides a series of volume data and visualizes joint motions. However, numerical analysis of 4DCT data ...

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7.7K Views.  Keio University School of Medicine. We analyzed joint kinematics from four-dimensional computed tomography data. The sequential 3D-3D registration method semiautomatically provides the kinematics of the moving bone with respect to the subject bone from four-dimensional computed tomography data.

Video: Four-Dimensional CT Analysis Using Sequential 3D-3D Registration

Improved Visualization and Quantitative Analysis of Drug Effects Using Micropatterned Cells

To date, most HCA (High Content Analysis) studies are carried out with adherent cell lines grown on a homogenous substrate in tissue-culture treated micro-plates. Under these conditions, cells spread and divide in all directions resulting in an inherent variability in cell shape, morphology and behavior. The high cell-to-cell variance of the overall population impedes the success of HCA, especially for drug development. The ability of micropatterns to normalize the shape and internal polarity of every individual cell provides a tremendous opportunity for solving this critical bottleneck 1-2.
To facilitate access and use of the micropatterning technology, CYTOO has developed a range of ready to use micropatterns, available in coverslip and microwell formats. In this video article, we provide detailed protocols of all the procedures from cell seeding on CYTOOchip micropatterns, drug treatment, fixation and staining to automated acquisition, automated image processing and final data analysis. With this example, we illustrate how micropatterns can facilitate cell-based assays. Alterations of the cell cytoskeleton are difficult to quantify in cells cultured on homogenous substrates, but culturing cells on micropatterns results in a reproducible organization of the actin meshwork due to systematic positioning of the cell adhesion contacts in every cell. Such normalization of the intracellular architecture allows quantification of even small effects on the actin cytoskeleton as demonstrated in these set of protocols using blebbistatin, an inhibitor of the actin-myosin interaction.

Adhesive micropatterns that normalize cellular architecture can be used to increase sensitivity in the detection of drug effects, improve reproducibility and simplify automated image acquisition and analysis. Such technology will benefit drug/siRNA screening assays, performed on conventional cell culture supports and consequently suffering from excessive cell-to-cell variability.

To date, most HCA (High Content Analysis) studies are carried out with adherent cell lines grown on a homogenous substrate in tissue-culture treated ...

Bioluminescence Imaging for Assessment of Immune Responses Following Implantation of Engineered Heart Tissue (EHT)

Various techniques of cardiac tissue engineering have been pursued in the past decades including scaffolding strategies using either native or bioartificial scaffold materials, entrapment of cardiac myocytes in hydrogels such as fibrin or collagen and stacking of myocyte monolayers 1. These concepts aim at restoration of compromised cardiac function (e.g. after myocardial infarction) or as experimental models (e.g. predictive toxicology and substance screening or disease modelling). Precise monitoring of cell survival after implantation of engineered heart tissue (EHT) has now become possible using in-vivo bioluminescence imaging (BLI) techniques 2. Here we describe the generation of fibrin-based EHT from a transgenic rat strain with ubiquitous expression of firefly luciferase (ROSA/luciferase-LEW Tg; 3). Implantation is performed into the greater omentum of different rat strains to assess immune responses of the recipient organism following EHT implantation. Comparison of results generated by BLI and the Enzyme Linked Immuno Spot Technique (ELISPOT) confirm the usability of BLI for the assessment of immune responses.

Bioluminescence Imaging for Assessment of Immune Responses Following Implantation of Engineered Heart Tissue EHT

This video demonstrates the use of in vivo bioluminescence imaging to study immune responses after implantation of Engineered Heart Tissue (EHT) in rats.

Various techniques of cardiac tissue engineering have been pursued in the past decades including scaffolding strategies using either native or ...

High Resolution 3D Imaging of Ex-Vivo Biological Samples by Micro CT

Non-destructive volume visualization can be achieved only by tomographic techniques, of which the most efficient is the x-ray micro computerized tomography (&mu;CT).
High resolution &mu;CT is a very versatile yet accurate (1-2 microns of resolution) technique for 3D examination of ex-vivo biological samples1, 2. As opposed to electron tomography, the &mu;CT allows the examination of up to 4 cm thick samples. This technique requires only few hours of measurement as compared to weeks in histology. In addition, &mu;CT does not rely on 2D stereologic models, thus it may complement and in some cases can even replace histological methods3, 4, which are both time consuming and destructive. Sample conditioning and positioning in &mu;CT is straightforward and does not require high vacuum or low temperatures, which may adversely affect the structure. The sample is positioned and rotated 180&deg; or 360&deg;between a microfocused x-ray source and a detector, which includes a scintillator and an accurate CCD camera, For each angle a 2D image is taken, and then the entire volume is reconstructed using one of the different available algorithms5-7. The 3D resolution increases with the decrease of the rotation step. The present video protocol shows the main steps in preparation, immobilization and positioning of the sample followed by imaging at high resolution.

High Resolution 3D Imaging of Ex-Vivo Biological Samples by Micro CT

Non-destructive volume visualization can be achieved only by tomographic techniques, of which the most efficient is the x-ray micro computerized tomography ( CT).

Non-destructive volume visualization can be achieved only by tomographic techniques, of which the most efficient is the x-ray micro computerized ...

Self-reporting Scaffolds for 3-Dimensional Cell Culture

Culturing cells in 3D on appropriate scaffolds is thought to better mimic the in vivo microenvironment and increase cell-cell interactions. The resulting 3D cellular construct can often be more relevant to studying the molecular events and cell-cell interactions than similar experiments studied in 2D. To create effective 3D cultures with high cell viability throughout the scaffold the culture conditions such as oxygen and pH need to be carefully controlled as gradients in analyte concentration can exist throughout the 3D construct. Here we describe the methods of preparing biocompatible pH responsive sol-gel nanosensors and their incorporation into poly(lactic-co-glycolic acid) (PLGA) electrospun scaffolds along with their subsequent preparation for the culture of mammalian cells. The pH responsive scaffolds can be used as tools to determine microenvironmental pH within a 3D cellular construct. Furthermore, we detail the delivery of pH responsive nanosensors to the intracellular environment of mammalian cells whose growth was supported by electrospun PLGA scaffolds. The cytoplasmic location of the pH responsive nanosensors can be utilized to monitor intracellular pH (pHi) during ongoing experimentation.

Biocompatible pH responsive sol-gel nanosensors can be incorporated into poly(lactic-co-glycolic acid) (PLGA) electrospun scaffolds. The produced self-reporting scaffolds can be used for in&#160;situ monitoring of microenvironmental conditions whilst culturing cells upon the scaffold. This is beneficial as the 3D cellular construct can be monitored in real-time without disturbing the experiment.

Culturing cells in 3D on appropriate scaffolds is thought to better mimic the in vivo microenvironment and increase cell-cell interactions. The resulting ...

Characterization Of Multi-layered Fish Scales (Atractosteus spatula) Using Nanoindentation, X-ray CT, FTIR, and SEM

The hierarchical architecture of protective biological materials such as mineralized fish scales, gastropod shells, ram&#8217;s horn, antlers, and turtle shells provides unique design principles with potentials for guiding the design of protective materials and systems in the future. Understanding the structure-property relationships for these material systems at the microscale and nanoscale where failure initiates is essential. Currently, experimental techniques such as nanoindentation, X-ray CT, and SEM provide researchers with a way to correlate the mechanical behavior with hierarchical microstructures of these material systems1-6. However, a well-defined standard procedure for specimen preparation of mineralized biomaterials is not currently available. In this study, the methods for probing spatially correlated chemical, structural, and mechanical properties of the multilayered scale of A. spatula using nanoindentation, FTIR, SEM, with energy-dispersive X-ray (EDX) microanalysis, and X-ray CT are presented.

Characterization Of Multi-layered Fish Scales Atractosteus spatula Using Nanoindentation, X-ray CT, FTIR, and SEM

This paper presents the methods used for probing spatially correlated chemical, structural, and mechanical properties of the multilayered scale of Atractosteus spatula (A. spatula) using nanoindentation, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and X-ray computed tomography (X-ray CT). The experimental results have been used to investigate the design principles of protective biological materials.

The hierarchical architecture of protective biological materials such as mineralized fish scales, gastropod shells, ram&#8217;s horn, antlers, and turtle ...

Microscale Vortex-assisted Electroporator for Sequential Molecular Delivery

Electroporation has received increasing attention in the past years, because it is a very powerful technique for physically introducing non-permeant exogenous molecular probes into cells. This work reports a microfluidic electroporation platform capable of performing multiple molecule delivery to mammalian cells with precise and molecular-dependent parameter control. The system&#8217;s ability to isolate cells with uniform size distribution allows for less variation in electroporation efficiency per given electric field strength; hence enhanced sample viability. Moreover, its process visualization feature allows for observation of the fluorescent molecular uptake process in real-time, which permits prompt molecular delivery parameter adjustments in situ for efficiency enhancement. To show the vast capabilities of the reported platform, macromolecules with different sizes and electrical charges (e.g., Dextran with MW of 3,000 and 70,000 Da) were delivered to metastatic breast cancer cells with high delivery efficiencies (&#62;70%) for all tested molecules. The developed platform has proven its potential for use in the expansion of research fields where on-chip electroporation techniques can be beneficial.

A microfluidic vortex assisted electroporation platform was developed for sequential delivery of multiple molecules into identical cell populations with precise and independent dosage control. The system&#8217;s size based target cell purification step preceding electroporation aided to enhance molecular delivery efficiency and processed cell viability.

Electroporation has received increasing attention in the past years, because it is a very powerful technique for physically introducing non-permeant ...

Fabricating Complex Culture Substrates Using Robotic Microcontact Printing (R-&#181;CP) and Sequential Nucleophilic Substitution

In tissue engineering, it is desirable to exhibit spatial control of tissue morphology and cell fate in culture on the micron scale. Culture substrates presenting grafted poly(ethylene glycol) (PEG) brushes can be used to achieve this task by creating microscale, non-fouling and cell adhesion resistant regions as well as regions where cells participate in biospecific interactions with covalently tethered ligands. To engineer complex tissues using such substrates, it will be necessary to sequentially pattern multiple PEG brushes functionalized to confer differential bioactivities and aligned in microscale orientations that mimic in vivo niches. Microcontact printing (&#956;CP) is a versatile technique to pattern such grafted PEG brushes, but manual &#956;CP cannot be performed with microscale precision. Thus, we combined advanced robotics with soft-lithography techniques and emerging surface chemistry reactions to develop a robotic microcontact printing (R-&#956;CP)-assisted method for fabricating culture substrates with complex, microscale, and highly ordered patterns of PEG brushes presenting orthogonal &#8216;click&#8217; chemistries. Here, we describe in detail the workflow to manufacture such substrates.

Fabricating Complex Culture Substrates Using Robotic Microcontact Printing R- &amp;#181;CP and Sequential Nucleophilic Substitution

Cell culture substrates functionalized with microscale patterns of biological ligands have immense utility in the field of tissue engineering. Here, we demonstrate the versatile and automated manufacture of tissue culture substrates with multiple, micropatterned poly(ethylene glycol) brushes presenting orthogonal chemistries that enable spatially precise and site-specific immobilization of biological ligands.

In tissue engineering, it is desirable to exhibit spatial control of tissue morphology and cell fate in culture on the micron scale. Culture substrates ...

Substructure Analyzer: A User-Friendly Workflow for Rapid Exploration and Accurate Analysis of Cellular Bodies in Fluorescence Microscopy Images

The last decade has been characterized by breakthroughs in fluorescence microscopy techniques illustrated by spatial resolution improvement but also in live-cell imaging and high-throughput microscopy techniques. This led to a constant increase in the amount and complexity of the microscopy data for a single experiment. Because manual analysis of microscopy data is very time consuming, subjective, and prohibits quantitative analyses, automation of bioimage analysis is becoming almost unavoidable. We built an informatics workflow called Substructure Analyzer to fully automate signal analysis in bioimages from fluorescent microscopy. This workflow is developed on the user-friendly open-source platform Icy and is completed by functionalities from ImageJ. It includes the pre-processing of images to improve the signal to noise ratio, the individual segmentation of cells (detection of cell boundaries) and the detection/quantification of cell bodies enriched in specific cell compartments. The main advantage of this workflow is to propose complex bio-imaging functionalities to users without image analysis expertise through a user-friendly interface. Moreover, it is highly modular and adapted to several issues from the characterization of nuclear/cytoplasmic translocation to the comparative analysis of different cell bodies in different cellular sub-structures. The functionality of this workflow is illustrated through the study of the Cajal (coiled) Bodies under oxidative stress (OS) conditions. Data from fluorescence microscopy show that their integrity in human cells is impacted a few hours after the induction of OS. This effect is characterized by a decrease of coilin nucleation into characteristic Cajal Bodies, associated with a nucleoplasmic redistribution of coilin into an increased number of smaller foci. The central role of coilin in the exchange between CB components and the surrounding nucleoplasm suggests that OS induced redistribution of coilin could affect the composition and the functionality of Cajal Bodies.

We present a freely available workflow built for rapid exploration and accurate analysis of cellular bodies in specific cell compartments in fluorescence microscopy images. This user-friendly workflow is designed on the open-source software Icy and also uses ImageJ functionalities. The pipeline is affordable without knowledge in image analysis.

The last decade has been characterized by breakthroughs in fluorescence microscopy techniques illustrated by spatial resolution improvement but also in ...

Effective Co-Registration of Two Preclinical Imaging Modalities Across Devices

Multimodal Cross-Device and Marker-Free Co-Registration of Preclinical Imaging Modalities

Integrated preclinical multimodal imaging systems, such as X-ray computed tomography (CT) combined with positron emission tomography (PET) or magnetic resonance imaging (MRI) combined with PET, are widely available and typically provide robustly co-registered volumes. However, separate devices are often needed to combine a standalone MRI with an existing PET-CT or to incorporate additional data from optical tomography or high-resolution X-ray microtomography. This necessitates image co-registration, which involves complex aspects such as multimodal mouse bed design, fiducial marker inclusion, image reconstruction, and software-based image fusion. Fiducial markers often pose problems for in vivo data due to dynamic range issues, limitations on the imaging field of view, difficulties in marker placement, or marker signal loss over time (e.g., from drying or decay). These challenges must be understood and addressed by each research group requiring image co-registration, resulting in repeated efforts, as the relevant details are rarely described in existing publications.
This protocol outlines a general workflow that overcomes these issues. Although a differential transformation is initially created using fiducial markers or visual structures, such markers are not required in production scans. The requirements for the volume data and the metadata generated by the reconstruction software are detailed. The discussion covers achieving and verifying requirements separately for each modality. A phantom-based approach is described to generate a differential transformation between the coordinate systems of two imaging modalities. This method showcases how to co-register production scans without fiducial markers. Each step is illustrated using available software, with recommendations for commercially available phantoms. The feasibility of this approach with different combinations of imaging modalities installed at various sites is showcased.

Author Spotlight: An Efficient and Robust Software for Automated Fusion of Multiple Preclinical Imaging Modalities

The combination of multiple imaging modalities is often necessary to gain a comprehensive understanding of pathophysiology. This approach utilizes phantoms to generate a differential transformation between the coordinate systems of two modalities, which is then applied for co-registration. This method eliminates the need for fiducials in production scans.

Integrated preclinical multimodal imaging systems, such as X-ray computed tomography (CT) combined with positron emission tomography (PET) or magnetic ...

Semi-Automated Mechanical-Enzymatic Tissue Dissociation for Single-Cell Analysis

Mechanical Dissociation of Tissues for Single Cell Analysis Using a Motorized Device

Being able to isolate and prepare single cells for the analysis of tissue samples has rapidly become crucial for new biomedical discoveries and research. Manual protocols for single-cell isolations are highly time-consuming and prone to user variability. Automated mechanical protocols are able to reduce processing time and sample variability but aren't easily accessible or cost-effective in lower-resourced research settings. The device described here was designed for semi-automated tissue dissociation using commercially available materials as a low-cost alternative for academic laboratories. Instructions to fabricate, assemble, and operate the device design have been provided. The dissociation protocol reliably produces single-cell suspensions with comparable cell yields and sample viability to manual preparations across multiple mouse tissues. The protocol provides the ability to process up to 12 tissue samples simultaneously per device, making studies requiring large sample sizes more manageable. The accompanying software also allows for customization of the device protocol to accommodate varying tissues and experimental constraints.

Author Spotlight: Advancements in Nanoparticle Technology for Drug Delivery and Immunotherapy

A general protocol for the combined enzymatic and semi-automated mechanical dissociation of tissues to generate single-cell suspensions for downstream analyses, such as flow cytometry, is provided. Instructions for the fabrication, assembly, and operation of the low-cost mechanical device developed for this protocol are included.

Being able to isolate and prepare single cells for the analysis of tissue samples has rapidly become crucial for new biomedical discoveries and research. ...