Presentation: Clinical Utility of Dose Reduction in Suspected Pulmonary Embolism Imaging utilizing SAFIRE

posted by Savvas Nicolaou, M.D. | Jan 10, 2013

Our study aims to compare the image quality, quantitatively and qualitatively, between the standard weighted filtered back projection (wFBP) and a new sinogram affirmed iterative reconstruction (SAFIRE) using CT Pulmonary Angiogram (CTPA) to diagnose pulmonary embolism at a lower dose.

Method and Materials
Retrospective analysis of 106 patients with suspected PE, 52 consecutive patients undergoing CTPA with wFBP reconstruction at 120 kV from June to October 2011, and 54 patients undergoing CTPA with SAFIRE reconstruction at 100kV from October to November 2011 respectively. Qualitative assessment was graded based on image noise texture, quality, sharpness, and diagnostic ability. Quantitative assessment was done by measuring mean and standard deviation of the regions of interest of pulmonary arteries, muscle and air and by calculating signal to noise (SNR) and contrast to noise ratios (CNR).

The SAFIRE group and wFBP group had comparative age, sex, number of pulmonary emboli, and lateral body diameter size. The mean DLP for SAFIRE was 151.1 mGy.cm and 315.3 mGy.cm for the wFBP group (p<0.0001) and the dose was decreased by 50% (2.21mSv versus 4.41mSv using conversion factor of 0.014, p<0.0001). The mean SNR was 23.1 and 18.8 (p=0.007) and mean CNR was 20.11 and 15.43 (p=0.003) for SAFIRE and FBP respectively. Qualitatively, the image noise texture (p= 0.21), quality (p=0.54) and sharpness (p=0.54), and diagnostic ability (p=0.49) were not significantly different.


  • Using 100kVp and ultra-high pitch imaging, significant dose reduction (50%) in the assessment of acute pulmonary embolism can be achieved without compromising diagnostic image quality.
  • The utilization of SAFIRE resulted in a significant reduction of signal to noise and image to noise ratio.

Clinical Relevance/Application
SAFIRE can reduce image noise significantly, which can allow even further dose reduction realization in the assessment of acute pulmonary embolism.
The presentation assesses the utility of SAFIRE (sinogram affirmed iterative reconstruction) to allow a dose reduction in assessment of PE with ultra-high pitch imaging by decreasing the voltage, yet still maintaining diagnostic image quality.

Download presentation (3.6 MB)

Submission Type: Scientific Presentations RSNA 2012

Authors: T Liang, M Homiedan, P McLaughlin, S J Co, K Krzymyk, J Mayo, S Nicolaou

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