Program Information
Fully Automated Evaluation of CT AEC Performance Using a Novel Automated Noise Level Measurement Technique
M Chun*, J Kim , Seoul National University, Seoul, Seoul
Presentations
TU-G-CAMPUS-I-4 (Tuesday, July 14, 2015) 4:30 PM - 5:00 PM Room: Exhibit Hall
Purpose: To assess the performance of CT automatic exposure control (AEC) system by using a newly developed automated noise level measurement technique.
Methods: Twenty pediatric patients’ CT image data of chest routine protocol taken with AEC (CARE Dose4D, Siemens Healthcare) were collected. A newly developed automated noise level measurement technique was applied to assess the noise level consistency across the varying body size. Subcutaneous fat region was segmented by applying thresholding of predefined intensity range followed by morphology operation on noise filtered image. A novel structure feature was calculated by combining sum of gradient and directional entropy of gradient at each pixel within the segmented subcutaneous fat. Five ROIs were randomly selected which have feature values less than 10 percentiles. The representative noise level was determined as an average of the HU standard deviations on 5 ROIs. Variation of noise levels were evaluated for the 20 CT data with the above noise measurements. In addition, 3 body factors such as water-equivalent body diameter (WBD), AP, and LAT diameter were extracted on each slice, and Pearson correlation coefficients between the noise measurements and body factors were compared.
Results: Most of the ROI placement (98%) by automated technique were accepted by an expert observer. Variation of noise standard deviation per patient ranged from 0.83 to 2.17 HU, whereas the mean noise ranged from 5.80 to 12.38 HU. Pearson correlation coefficient was highest between WBD and noise level by showing 0.76±0.06.
Conclusion: Performance of CT AEC system could be assessed with a fully automated technique. Our proposed technique is a potentially useful tool for investigating various characteristics and optimal use of AEC system in clinical setting.
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