Dawson, Christopher

Hanger, Christopher C

Haworth, Steven

Johnson, R. H.

Karau, Kelly Lynn

Molthen, Robert C.

English

epublications@Marquette

Marquette Universitye-Publications@MarquetteBiomedical Engineering Faculty Research andPublications Biomedical Engineering, Department of11-28-19993D Micro-CT for Functional GenomicsR. H. JohnsonMarquette UniversityRobert C. MolthenMarquette University, robert.molthen@marquette.eduChristopher C. HangerMedical College of WisconsinKelly Lynn KarauMarquette UniversitySteven HaworthMarquette UniversitySee next page for additional authorsPublished version. Published as part of the proceedings of the conference Radiological Society ofNorth America 1999 Scientific Assembly and Annual Meeting, Chicago, IL, (November 28 - December3, 1999): 194. Publisher link. © 1999 Radiological Society of North America, Inc. (RSNA). Usedwith permission.AuthorsR. H. Johnson, Robert C. Molthen, Christopher C. Hanger, Kelly Lynn Karau, Steven Haworth, andChristopher DawsonThis abstract is available at e-Publications@Marquette: https://epublications.marquette.edu/bioengin_fac/403I ' . Mond~y ~ftem~n. Room ~1AB • Physics (CT: Technical Developme~ts) m' jOint sponsorship with the American Association of Physicists in Medicine PRESIDING: Norbert J. Pelc, ScO, Stanford, CA Computer Code: G01 • 1.% hours To receive credit, relinquish attendance voucher at end of session . . 414 • 2:30 PM High Spatial Resolution 3D X-ray Cone-Beam Mlcrotomography - K. Engelke, PhD, Erfangen, Germany· M. Karolczak, PhD· A. Lutz, Dipl Phys· U. Seibert· S. Schaller, PhD· w.A. Kalender, PhD . PURPOSE: To develop a micro tomography scanner for 3D in-vitro scan-ning of soft tissue and bone samples. . . METHOD AND MATERIALS: A cone be'!ffi microtomography imaging system with variable magnification has been developed. The system components are: - a microfocus X-ray tube with transmission target, <5-pm focus diameter, 0-100kV anode voltage, and 3W output power - a 2D CCO square detector with 1024z elements of (19-pm)2 size each, 3:1 magnifying fiber-optic taper, phosphor plate, Peltier cooling and 16 bit dynamic range -a flexible positioning system - software for raw data volume reconstruc-tion, simulation, and image analysis The scanner exploits the advantages of cone beam geometry. The object apd the detector can be independently translated with respect to the tube with a maximum tube-detector distance of 1000mm providing a maximum object image magnification of 20:1. The smallest voxel size is 2.5-pm and the maximum object diameter is SOmm. Positioning ~tages allow for acquiring data using circular and complex trajectories, including spiral cone-beam and a combination of rotation and translation: For volume reconstruction approximate and accurate algo-rithms can be used. A variety of samples has been scanned, the tube focal spot stability has been measured, and sample alignment requirements have been determined. RESULTS: - Acquisiton times of approx. 3h (lOs exposure time, 720 projections) are sufficient for high contrast objects. Longer times are required for low contrast objects. - A .spatial resolution of lOpm has been achieved (determined by thin tungsten wire phantoms). This requires the determination of the misalignment of the axis of rotation with very high accuracy (tilt :50.1° and center-of-rotation shift :5i]llll.). Correction can be done either by mechanical realigriment or inclusion of the misalignment coefficients in the reconstruction algorithm. - Reconstruction using Feld-kamp algorithm takes =2h for a 5123 volume reconstructed from 720 projections on a Pentium ill computer. - MeasureII;lents of the tube focal spot properties (using thin wire method) have been performed, and S5-pm focal spot position stability has been found. CONCLUSIONS: - A spatial resolution of a few micrometers is achievable, but requires very thorough scanner mechanical alignment. - A small focal spot size of the X-ray tube is essential, though n<?t sufficient to achieve a high spatial resolution. Critical is also focal spot po~ition stability during scan. Misalignment of axis of rotation due to this instability remains the main limitation for spatial resolution and cannot be easily corrected for. 415 - 2:39 PM 3D Mlcro-CT for Functional Genomic. R.H. Johnson, PhD, Milwaukee, WI· R.M. Molthen, PhD - C.G. Hanger, MD· K.L. Karau, BS · S. T. Haworth, PhD· C.A. Dawson, PhD PURPOSE: With the sequencing of the human genome nearing completion, emphasis is being brought to bear on research methodology and appropri-ate technology to reliably and rapidly quantify phenotypes in genetically-engineered mice and other animal models relevant to human disease. These methods should be nondestructive and preferably noninvasive, low-cost and capable of high throughput. METHOD AND MATERIALS: We have developed a special purpose micro-CT scanner capable of imaging objects ranging from one millimeter to several centimeters in size, including small animals and excised organs. Conebeam reconstruction algorithms are employed to directly reconstruct 3D image volumes from uncollimated 20 projection images acquired from many angles around the object using an image intensifier/CCO camera imaging chain. Analysis software was developed to extract dimensional and other measurements from the imaged volumes in a semiautomated fashion. RESULTS: We have analyzed images of excised mouse, rat and dog lungs, dog hearts and of live anesthetized mice, with emphasis on contrast-enhanced arterial tree structures. Seeded 3D region growing techniques were used to segment vascular structures, with the imposition of connectiv-ity constraints to preserve tree topology. Segment lengths and diameters 194 were measured by interactive and semiautomated methods. !"10rphometric parameters derivable from the quantit~tive image metrics were sensitive to interspecies differences ill arterial tree structures. CONCLUSIONS: Imaging provides a class of methods to noninvasively extract phenotypes relevant tQ complex manifestations of gene expression. Automation of segmentation, feature extraction and classification algo-rithms remains a challenge, important for achieving the throug~put and . low costs required for more widespre~d application. Ongoing stud~es will assess the sensitivity of the method to vascular pathologies. Augmentation of the high-resolution structural' information provided by transmission CT with .the insigi}.ts into functions like metabolism, elimination and messen-ger systems provide<;l .with exquisite sensitivity by emission CT would expand the power and applicability of tomography to functional gencmics. . We acknowledge support from the Whitaker Foundation, the Keck Founda-tion, the Falk Medical Trust, NHLBI ill-19298, and the Veterans Adminis-tration. ·416 - 2:48 PM 3D Acetabular Models: Accuracy and Reliability of CT, Volume Rendering, CAD Modeling, and Rapid Prototyplng , D.O. Robertson, MD, PhD, Saint Louis, MO· P.K. Commean, BEE· K.E. Smith, AAS PURPOSE: CT-based 3D volume rendering, CAD modeling and rapid prototyping (~) realistically ·depict acetabular morphology and have potential to assist preoperative planning of complex surgeries. We sought . to validate the accuracy and reliability of these techniques for depicting acetabular morphology with and without unilateral total hip prostheses in place. , METHOD AND MATERIALS: Spherical fiducial markers were placed on hemipelvi of three cadavers. Spiral (helical) and conventional CT were performed prior to and following insertion of unilateral total hip replace-ments. 3D volume renderings, CAD and RP models were created from cr image sets obtained at 2 different times. Accuracy and reliability were calculated by comparing repeated measures of direct (caliper) inter-fiducial marker measurements with repeated measures made from CT, volume renderings, CAD and RP mpdels. RESULTS: CT, volume rendering, CAD modeling, and rapid protC?typing were accurate and reliable, with and without unilateral hip prostheses present. CT and 3D visualization and modeling methods, as compared to direct caliper measurements, underestimated caliper measurements by less than 1 mm. Test-retest reliability for CT and 3D methods was excellent, averaging 0.5 mm. CONCLUSIONS: CT may be used to create accurate and reliable 3D volume renderings or CAD and rapid prototyping models of the acetabu-lum, even in the presence ot unilateral total hip replacements. 417 - 2:57 PM Development of a SubJect-standlng-type Cone-Beam CT for Chest and OrthopediC Imaging @) . R. Baba, MS, Kokubunji, Japan· K. Ueda, MS· A. Kuba, BS· E. Kohda, MD· N. Shiraga, MD· T. Sanmiya, RT PURPOSE: A new 3D-imaging modality for subjects sitting or standing naturally is desirable especially for 'chest and orthopedic imaging. Cone-beam CT can acquire a full set of projection images during a single rotation scan and reconstructs an isotropic high-spatial-resolution 3D image. Our purpose is to develop a ~ubject-standing-type cone-beam CT with high spatial resolution and a high SIN ratio. , METHOD AND MATERIALS: The developed system includes a turntable having a backrest. The subject may stand against the backrest, or can sit on chair placed on the turntable. The x-ray tube and the imaging detector are adjusted according to the subject imaging position and remain stationary during·the scan. The detector consists of a 16-ihch x-ray image-intensifier CCD camera. The camera acquires a 12-bit 5122-pixel projection at 60 f / s, the rotation period is 4.8 s for 288 projections and 9.6 s for 576 projections. To reduce image noise, the system controls the x-ray-pulse duration and iris-opening area for each projection through real-time analysis of the projection image: pulse duration is controlled for subject transmittance compensation, and the opening area adjusts the light level to suit the CCD camera. To improve CT-value accuracy and eliminate artifacts, the veiling glare of the image intensifier and scattered x-rays are corrected by a newly developed method: blur-image components of glare and scatter are estimated and subtracted from each projection image. Human chest and orthopedic studies with 24 patients were conducted. RESULTS: 3D images with sphere field of view (FOV) with a diameter of 21-2Scm, 0.4- to O.S-mm voxels, and a 5123 matrix were obtained. During one rotation scan of geniculum, the typical x-ray exposure varied in the range of 1.8-4.4 ms depending on the imaging direction, which enabled high image quality at a low dose (30 mAs). In coronal, sagittal, and volume rendering images, the surface of arthrosis was visualized sp100thly with a higher resolution than with conventional CT. In the case of gonarthrosis, narrowing of the clearance at the surface of arthrosis, an abnormal tum of patella, and dislocation of the thigh were visualized clearly; these abnor--

3D Micro-CT for Functional Genomics

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3D Micro-CT for Functional Genomics

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