Tsutomu Gomi PhD, Presenter: Nothing to Disclose

Masahiro Nakajima BSC, Abstract Co-Author: Nothing to Disclose

Tokuo Umeda PhD, Abstract Co-Author: Nothing to Disclose

Tohoru Takeda MD, PhD, Abstract Co-Author: Nothing to Disclose

Akiko Okawa MBBS, Abstract Co-Author: Nothing to Disclose

Kazuya Sakaguchi, Abstract Co-Author: Nothing to Disclose

To investigate the application of pre-reconstruction wavelet denoising processing (WDP) to selectively remove quantum noise structures from projected images and the possibility of reducing the exposure dose for chest digital tomosynthesis (DT).

Noise differentiation is based on an a priori knowledge of quantum noise production. Therefore, we used a hybrid technique that exploits both deterministic nature of quantum noise generation and signal locality of the wavelet domain. This technique was implemented on a DT system (SonialVision Safire II; Shimadzu Co.) and was experimentally evaluated through chest phantom measurements (artificial nodule at 8-mm diameter ground–glass opacity) compared with existing WDP algorithm [Badea et al. Comp. Med. Imaging Graph. 22, 309 (1998)]. To improve detection and potential quantum noise reduction in DT, DT was evaluated using different doses (reference, 2.752 mSv; standard, 0.215 mSv; low, 0.075 mSv). In this study, WDP parameters, such as contrast-to-noise ratio (CNR), root-mean-square error (RMSE, comparison between with and without WDP), and modulation transfer function (MTF) were evaluated for the in-focus plane.

Pre-reconstruction WDP effectively reduced quantum noise compared with processing at an existing algorithm, as determined by CNR (reference, 6.04; standard pre-WDP, 5.11; low pre-WDP, 1.26; standard existing WDP, 3.84; low existing WDP, 0.64). The quantum noise structure reductions in the images were slightly smooth with pre-reconstruction WDP, as determined by RMSE (standard pre-reconstruction, 6.66; low pre-reconstruction, 6.47; standard existing algorithm, 2.51; low existing algorithm, 3.97). There was no variation in MTF between with and without pre-reconstruction WDP (preserving normal structure), but existing WDP was deteriorating. These results suggest a possibility that the exposure dose can be reduced by the pre-reconstruction WDP method.

An approach for quantum noise removal in DT that involved a WDP application dedicated to DT projection images proved effective for certain classes of objects having features of high-frequency components.

We believe that this technique can improve the clinical applications of chest DT in medical imaging fields where objects having features of high-frequency components are the focus of interest.

Gomi, T, Nakajima, M, Umeda, T, Takeda, T, Okawa, A, Sakaguchi, K, Pre-Reconstruction of Wavelet Denoising Processing for Removing Quantum Noise in Digital Tomosynthesis of the Chest.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12043856.html