Simple technique for calibrating imaging geometries

Kenneth R. Hoffmann, Jacqueline Esthappan, Shidong Li, Charles A. Pelizzari

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

13 Scopus citations


We have developed a new, simple technique for accurate determination of the imaging geometry for calibration of projection imaging systems. Images of a phantom containing lead beads were obtained after it was placed at arbitrary, unknown locations which were near the isocenter of a radiation therapy simulator. The location of the lead beads were identified in the images. A computer model of the phantom was generated and positioned at an arbitrary location. Projection images of the model were generated and compared with the actual image locations. A modified projection-Procrustes algorithm was then used to translate and rotate the phantom model until it aligned optimally with the set of lines connecting the focal spot with the corresponding image points. The rotation matrix and translation vector relating the multiple projection geometries were then determined using a Procrustes algorithm and the calculated positions of the phantom for each projection. For a wide range of starting points, the technique converged to 3D locations with an approximate precision of 0.1 cm in position and approximately 0.2 degrees in orientation. The calculated angles and distances agreed with the readouts on the imaging systems to within approximately 0.25 degrees.

Original languageEnglish
Title of host publicationProceedings of SPIE - The International Society for Optical Engineering
EditorsRichard L. Van Metter, Jacob Beutel
Number of pages6
StatePublished - 1996
EventMedical Imaging 1996: Physics of Medical Imaging - Newport Beach, CA, USA
Duration: Feb 11 1996Feb 13 1996

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X


ConferenceMedical Imaging 1996: Physics of Medical Imaging
CityNewport Beach, CA, USA


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