MO-EE-A4-04: Extraction of Tube Current Values from DICOM CT Images for Patient Dose Calculations

Abstract

Purpose: When CT examinations are conducted with automatic mA‐modulation, the tube current (mA) may vary from one CT slice to next; i.e., mA is no longer a fixed constant. Patient dose calculation is no longer a straight forward process. The purpose of this presentation is to show how the mA information may be extracted from DICOM CTimages without having to manually read off “mAvalues” from the displayed images.Method and Materials: A statistical programming language “R”, which is capable of reading DICOM files, is employed to extract the mA‐values from a series of DICOM CTimages. This task is carried out with a “script” designed to read the mA‐values from the DICOM CTimages and generate a “file” in “delimited ASCII” format. This “file” can be imported into Excel (a Microsoft spreadsheet program) for further processing, calculation and chart production. A CT examination of chest was selected to carry out this operation for demonstration purposes. Results: The “script” generated a delimited ASCII “file” which is a two column data sheet with the slice location and its corresponding mA‐values. After the “file” is imported into Excel for calculation, and with other pertinent scan parameters, the average mA can now be plugged into a CTdosimetry calculation program such as ImPACT for calculation of CTDIw, CTDIvol, Dose‐Length‐Product and critical organ dose. Furthermore, a graphical presentation of the “mA” vs. slice location can be produced with Excel. The chart generated by Excel is supplied as supporting material for review. Conclusion: The script we have written is able to extract mA‐values from DICOM CTimages, generating a delimited ASCII file for further processing with Microsoft Excel spreadsheet program. This semi‐automated process of extracting mA‐values enabled us to perform dose calculation for patients undergoing CT examination scanned with automatic mA‐modulation control.