Author(s)

Susumu Nakabayashi¹, Takashi Chikamatsu², Takao Okamoto³, Tatsuro Kaminaga⁴, Norikazu Arai², Shinobu Kumagai², Kenshiro Shiraishi⁴, Takahide Okamoto¹, Takenori Kobayashi¹, Jun’ichi Kotoku^1,2*

¹Graduate School of Medical Care and Technology, Teikyo University, Tokyo, Japan.
²Central Radiation Division, Teikyo University Hospital, Tokyo, Japan.
³Diagnostic Imaging, PET Center, Musashimurayama Hospital, Tokyo, Japan.
⁴Department of Radiology, Teikyo University School of Medicine, Tokyo, Japan.

Low-count SPECT images are well known to be smoothed strongly by a Butterworth filter for statistical noise reduction. Reconstructed images have a low signal-to-noise ratio (SNR) and spatial resolution because of the removal of high-frequency signal components. Using the developed robust adaptive bilateral filter (RABF), which was designed as a pre-stage filter of the Butterworth filter, this study was conducted to improve SNR without degrading the spatial resolution for low-count SPECT imaging. The filter can remove noise while preserving spatial resolution. To evaluate the proposed method, we extracted SNR and spatial resolution in a phantom study. We also conducted paired comparison for visual image quality evaluation in a clinical study. Results show that SNR was increased 1.4 times without degrading the spatial resolution. Visual image quality was improved significantly (p < 0.01) for clinical low-count data. Moreover, the accumulation structure became sharper. A structure embedded in noise emerged. Our method, which denoises without degrading the spatial resolution for low-count SPECT images, is expected to increase the effectiveness of diagnosis for low-dose scanning and short acquisition time scanning.

Bilateral Filter, Denoising, SPECT, Nuclear Medicine

Nakabayashi, S. , Chikamatsu, T. , Okamoto, T. , Kaminaga, T. , Arai, N. , Kumagai, S. , Shiraishi, K. , Okamoto, T. , Kobayashi, T. and Kotoku, J. (2018) Denoising Projection Data with a Robust Adaptive Bilateral Filter in Low-Count SPECT. International Journal of Medical Physics, Clinical Engineering and Radiation Oncology, 7, 363-375. doi: 10.4236/ijmpcero.2018.73030.