Matthias H. Brem MD, Presenter: Nothing to Disclose

Amir A. Zamani MD, Abstract Co-Author: Nothing to Disclose

Kelly H. Zou PhD, Abstract Co-Author: Nothing to Disclose

Roberto Riva MD, Abstract Co-Author: Nothing to Disclose

Alexander M. Norbash MD, Abstract Co-Author: Nothing to Disclose

U. Joseph Schoepf MD, Abstract Co-Author: Nothing to Disclose

To determine the potential for radiation dose reduction at MDCT of the paranasal sinuses by computer simulation of the effects of low-radiation dose acquisition on diagnostic image quality.

A total of 20 patients (age 22-75 years) were scanned with 120kV and 170mAs using 4-slice MDCT (Somatom Sensation4, Siemens)and 4x1-mm slice collimation. Anatomically structured artificial image noise was added to the scan raw data using a dedicated software platform (Syngo Explorer, VAMP). Lower radiation dose acquisitions with 134, 100, 67, and 33mAs were simulated. From each raw data set images with 1.25mm slice thickness were reconstructed with both bone and soft tissue algorithms, resulting in a total of 100 data sets. Two radiologists, blinded to the parameters, reviewed the data independently and in a random fashion. A 5-point rating scale was used to score the diagnostic image quality of bony and soft tissue structures. A two-sided paired Student's t-test was used to compare the mean of the pooled ratings of each reader to determine the least possible radiation dose that still provided diagnostic image quality.

The cut-off tube current settings below which a significant difference in the mean ratings for diagnostic quality was observed compared to the original standard dose acquisition were ≤67mAs for the nasal septum ( p=0.01), ≤67mAs for the middle turbinate (p=0.03), ≤67mAs for the inferior turbinate (p=0.01) and ≤67mAs for the frontal sinus (p=0.004). For soft tissue structures this was the case at ≤100mAs for the optic nerve (p=0.003), ≤100mAs for the inferior rectus muscle (p=0.04), ≤134mAs for the basal ganglia (p=0.002), and ≤134mAs for the capsula interna (p=0.002).

There is considerable potential for reducing radiation dose at MDCT of the paranasal sinus. Based on the results of this study, radiation dose can be lowered by 40-60%(e.g. to 100mAs), without impairing image quality. If only bony structures are to be assessed, even lower radiation doses can be applied without loss of diagnostic information.

Brem, M, Zamani, A, Zou, K, Riva, R, Norbash , A, Schoepf, U, Potential for Radiation Dose Reduction at Multi-Detector Row Computed Tomography (MDCT) of the Paranasal Sinus.  Radiological Society of North America 2004 Scientific Assembly and Annual Meeting, November 28 - December 3, 2004 ,Chicago IL. http://archive.rsna.org/2004/4408379.html