John R. Mayo MD, Presenter: Nothing to Disclose

1) The contribution medical radiation dose to population radiation dose. 2) Understand the contribution of CT radiation dose to medical radiation dose. 3) Educate participants on the two components of CT radiation dose reduction, optimization and justification. 4) Illustrate techniques for CT radiation dose optimization. 5) Demonstrate approaches for CT examination justification.

NRCP radiation dose survey data of the United States from the mid 1980's to 2006 shows a dramatic rise in population radiation dose from 3.6 mSv to 6.2 mSv.  The overwhelming majority of this radiation dose increase is secondary to the use of ionizing radiation for medical imaging.  The imaging modality accounting for the largest component of this increase is CT.  The large radiation dose impact of CT arises from the relatively high dose of the exam and its widespread utilization.  The high dose per CT exam can be explained by examing the information provided by the modality.  CT scans calculate point attenuation values within the patient, giving a cross section view of gross anatomy.  To calculate point attenuation, CT obtains 800-1400 views around the patient.  Since each view requires some radiation, the large number of views translates into high radiation dose when compared to the single view of the plain radiograph.  This high dose, combined with the high utilization rate, has led to the high population radiation dose of CT.  Radiation dose reduction in CT has two components, optimal matching of the radiation dose of the CT exam to the specific patient clinical question (optimization) and tailoring the frequency of CT examinations (justification) to the patient's age, stage of disease and impact on disease management (justification). Examples of thoracic CT dose optimization will be provided including; tube current modulation, scan length optimization, over range artifact reduction, BMI based kVp selection, ECG modulation and organ specific tube current modulation.  Improvements in chest CT justification through exam specific radiation dose monitoring and physician education will also be illustrated .

Mayo, J, Fleischner Guidelines for Radiation Dose in Thoracic CT.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9000100.html