Room: Exhibit Hall | Forum 8
Purpose: The purpose of this investigation was to compare water-equivalent thicknesses between fluoroscopic patient image data and phantom image data acquired using the standard ANSI phantom in various anatomic arrangements.
Methods: Fluoroscope-reported water-equivalent thickness were extracted from the DICOM image header for phantom and patient images. The phantom data was acquired using a standard polymethylmethacrylate and aluminum ANSI phantom in several anatomic arrangements (chest, abdomen, skull, and extremity) using a Siemens Artis Zee fluoroscope in a posteroanterior (PA) projection. The patient images were obtained from 7 Siemens fluoroscopes, which included Artis Q, Artis Zee, and Artis Zeego systems. The patient image dataset was parsed to include only projections within Â± 5 degrees of a 0 degrees in the primary and secondary gantry rotational angles. The water-equivalent values using the various ANSI anatomic arrangements were compared to the corresponding data from the patient images.
Results: The average patient water-equivalent thicknesses varied from the phantom data; chest data was approximately 87% larger; abdomen data was approximately 26% larger; extremity data was approximately 117% larger; and the lateral skull data was approximately 6% larger.
Conclusion: At our institution, the ANSI phantom, in all arrangements except the lateral skull, does not adequately represent our current average patient water-equivalent thicknesses. Although the ANSI phantom may be useful for constancy testing, or relative measurements between fluoroscopic imaging systems, the phantom, based on our data, should not be used to represent any typical or average patient attenuation for dosimetric purposes.