John M. Sabol PhD, Presenter: Employee, General Electric Company

Nahush Rao, Abstract Co-Author: Employee, General Electric Company

Digital tomosynthesis (DTS) imaging is increasingly being used for numerous thoracic indications. In addition to evaluation of the diagnostic capability of this technique, it is important to understand the dose to the patient relative to conventional chest x-ray (CXR) and CT protocols.

An international, multi-center, clinical trial was designed and conducted under IRB approval to compare the performance of DTS to conventional two-view CXR for the detection of lung nodules, using CT as the reference standard. Subjects in the study had a diagnostic CT exam as part of routine care for a variety of thoracic indications, and then received conventional 2-view CXR and DTS exams (GE Healthcare, XR656 with VolumeRAD). Effective dose for CXR and DTS was calculated using the PCXMC Monte Carlo tool (STUK, Finland). Calculation of absorbed dose was based on estimates of incident air kerma from exposure technique data and the assumption of average habitus subjects. CT effective dose was calculated using the ICRP 103 methodology from the DLP determined from reported CTDI values.

Technique data for dose estimation was available for all 158 subjects in the study for some modalities, and for 91 subjects for all modalities. For the 91 cases with valid data for all modalities, the mean effective dose (and standard deviation) was 0.059 (0.033), 0.088 (0.037), and 4.86 (3.2) mSv for CXR, DTS, and CT respectively. The CXR and DTS effective doses were significantly less than CT (p < 0.01), and less than 0.1 mSv (p <0.01). The use of 0.2 mm Cu additional filtration (at 120 kVp) was observed to reduce the effective dose for the DTS subjects. The variation in DTS effective dose was much less than CXR as a result of increased uniformity of delivered mAs per projection in the DTS acquisition.

For the patients in this clinical trial, the average effective dose of a DTS acquisition was only 1.5 times greater than that of a conventional two-view chest radiograph, and significantly less than that of the diagnostic thoracic CT exams. DTS provides tomographic image information, enabling significantly increased nodule detection sensitivity, with less than 0.1 mSv effective dose.

Digital tomosynthesis imaging provides volumetric image data enabling increased lung nodule detection compared to conventional chest x-ray at a similar, minimal, radiation level (less than 0.1 mSv).

Sabol, J, Rao, N, Effective Dose of Chest X-ray, Tomosynthesis, and Thoracic CT in a Multi-Center Clinical Trial.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14006735.html