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Published online before print May 15, 2003, 10.1148/radiol.2281020606
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Can Noise Reduction Filters Improve Low-Radiation-Dose Chest CT Images? Pilot Study1

Mannudeep K. Kalra, MD, Conrad Wittram, MB, ChB, Michael M. Maher, MD, FFR (RCSI), FRCR, Amita Sharma, MD, Gopal B. Avinash, PhD, Kelly Karau, PhD, Thomas L. Toth, AAS, Elkan Halpern, PhD, Sanjay Saini, MD and Jo-Anne Shepard, MD

1 From the Department of Radiology, Founders 202, Massachusetts General Hospital and Harvard Medical School, 32 Fruit St, Boston, MA 02114 (M.K.K., C.W., M.M.M., A.S., E.H., S.S., J.S.), and GE Medical Systems, Waukesha, Wis (G.B.A., K.K., T.L.T.). Supported in part by a grant from GE Medical Systems. Received May 23, 2002; revision requested July 16; final revision received October 11; accepted October 23. Address correspondence to J.S. (e-mail: jshepard@partners.org).



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  		Figure 1a. Contrast material-enhanced transverse CT images of the chest obtained with 140 kVp, 110 mA, and 0.8-second gantry rotation time in a 65-year-old man. (a) Baseline image. (b) Same baseline image postprocessed with filter F. Note deterioration of sharpness of lung vascular marking and conspicuity of peripheral vascular markings (arrows) on b in comparison with a.

 


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  		Figure 1b. Contrast material-enhanced transverse CT images of the chest obtained with 140 kVp, 110 mA, and 0.8-second gantry rotation time in a 65-year-old man. (a) Baseline image. (b) Same baseline image postprocessed with filter F. Note deterioration of sharpness of lung vascular marking and conspicuity of peripheral vascular markings (arrows) on b in comparison with a.

 


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  		Figure 2a. Contrast-enhanced transverse CT images of the chest obtained with 140 kVp, 120 mA, and 0.8-second gantry rotation time in a 70-year-old man. (a) Baseline image. (b) Same baseline image postprocessed with filter C. (c) Same baseline image postprocessed with filter F. Note improvement of mediastinal and chest wall noise and deterioration of chest wall sharpness (arrow) in b and c in comparison with a.

 


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  		Figure 2b. Contrast-enhanced transverse CT images of the chest obtained with 140 kVp, 120 mA, and 0.8-second gantry rotation time in a 70-year-old man. (a) Baseline image. (b) Same baseline image postprocessed with filter C. (c) Same baseline image postprocessed with filter F. Note improvement of mediastinal and chest wall noise and deterioration of chest wall sharpness (arrow) in b and c in comparison with a.

 


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  		Figure 2c. Contrast-enhanced transverse CT images of the chest obtained with 140 kVp, 120 mA, and 0.8-second gantry rotation time in a 70-year-old man. (a) Baseline image. (b) Same baseline image postprocessed with filter C. (c) Same baseline image postprocessed with filter F. Note improvement of mediastinal and chest wall noise and deterioration of chest wall sharpness (arrow) in b and c in comparison with a.

 


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  		Figure 3. Graph shows image noise on corresponding original and postprocessed images of line-wire phantom. Note the similar trends with qualitative and quantitative noise reduction, compared with patients’ data shown in Tables 1 and 2.

 


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  		Figure 4. Graph shows MTF with line-wire phantom for original images and images postprocessed with filters A-F. lp/cm = line pairs per centimeter.

 


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  		Figure 5. Graph shows spatial resolution at 10% ({blacktriangleup}) and 50% ({bullet}) MTF for original images and images postprocessed with filters A-F. lp/cm = line pairs per centimeter.

 


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  		Figure A1. Schematic depicts main steps of filtering algorithms used in this study. I1 = input image, I2 = intermediate image, I3 = filtered image, I4 = image formed by expansion by factor x, I5 = final filtered output image.

 




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