A method for calculating the dose length product from CT DICOM images.

OBJECTIVE The dosimetric calculations in CT examinations are currently based on two quantities: the volume weighted CT dose index (CTDI(vol)) and the dose-length product (DLP). The first quantity is dependent on the exposure factors, scan field of view, collimation and pitch factor selections, whereas the second is additionally dependent on the scan length. METHODS In this study a method for the calculation of these quantities from digital imaging and communication in medicine (DICOM) CT images is presented that allows an objective audit of patient doses. This method was based on software that has been developed to enable the automatic extraction of the DICOM header information of each image (relating to the parameters that affect the aforementioned quantities) into a spreadsheet with embedded functions for calculating the contribution of each image to the CTDI(vol) and DLP values. The applicability and accuracy of this method was investigated using data from actual examinations carried out in three different multislice CT scanners. These examinations have been performed with the automatic exposure control systems activated, and therefore the tube current and tube loading values varied during the scans. RESULTS The calculated DLP values were in good agreement (±5%) with the displayed values. The calculated average CDTI(vol) values were in similar agreement with the displayed CTDI(vol) values but only for two of the three scanners. In the other scanner the displayed CTDI(vol) values were found to be overestimated by about 25%. As an additional application of this method the differences among the tube modulation techniques used by the three CT scanners were investigated. CONCLUSION This method is a useful tool for radiation dose surveys.

[1]  Virginia Tsapaki,et al.  CT-guided interventional procedures without CT fluoroscopy assistance: patient effective dose and absorbed dose considerations. , 2007, AJR. American journal of roentgenology.

[2]  E. Garelli,et al.  Patient dose evaluation by means of DICOM images for a direct radiography system , 2008, La radiologia medica.

[3]  Margarita Chevalier,et al.  Patient dose in digital mammography. , 2004, Medical physics.

[4]  S. Edyvean,et al.  Patient dose reduction in CT. , 2005, The British journal of radiology.

[5]  H. Bosmans,et al.  Results of a European dose survey for mammography. , 2008, Radiation protection dosimetry.

[6]  C. McCollough,et al.  CT dose reduction and dose management tools: overview of available options. , 2006, Radiographics : a review publication of the Radiological Society of North America, Inc.

[7]  Comparison of measured and calculated skin doses in CT-guided interventional procedures. , 2008, AJR. American journal of roentgenology.

[8]  R. Nicholson,et al.  Primary radiation outside the imaged volume of a multislice helical CT scan. , 2002, The British journal of radiology.

[9]  Jin Mo Goo,et al.  Radiation dose modulation techniques in the multidetector CT era: from basics to practice. , 2008, Radiographics : a review publication of the Radiological Society of North America, Inc.