Enhancement of positron emission tomography-computed tomography image quality using the principle of stochastic resonance.
OBJECTIVE
Acquisition of higher counts improves visual perception of positron emission tomography-computed tomography (PET-CT) image. Larger radiopharmaceutical doses (implies more radiation dose) are administered to acquire this count in a short time period. However, diagnostic information does not increase after a certain threshold of counts. This study was conducted to develop a post processing method based on principle of "stochastic resonance" to improve visual perception of the PET-CT image having a required threshold counts.


METHODS
PET-CT images (JPEG file format) with low, medium, and high counts in the image were included in this study. The image was corrupted with the addition of Poisson noise. The amplitude of the Poisson noise was adjusted by dividing each pixel by a constant 1, 2, 4, 8, 16, and 32. The best amplitude of the noise that gave best images quality was selected based on high value of entropy of the output image, high value of structural similarity index and feature similarity index. Visual perception of the image was evaluated by two nuclear medicine physicians.


RESULTS
The variation in structural and feature similarity of the image was not appreciable visually, but statistically images deteriorated as the noise amplitude increases although maintaining structural (above 70%) and feature (above 80%) similarity of input images in all cases. We obtained the best image quality at noise amplitude "4" in which 88% structural and 95% feature similarity of the input images was retained.


CONCLUSIONS
This method of stochastic resonance can be used to improve the visual perception of the PET-CT image. This can indirectly lead to reduction of radiation dose.
Department of Nuclear Medicine, All India Institute of Medical Sciences, New Delhi, India.
Anil Kumar
AK
Pandey
Department of Nuclear Medicine, All India Institute of Medical Sciences, New Delhi, India.
Sanjay Kumar
SK
Sharma
Department of Nuclear Medicine, All India Institute of Medical Sciences, New Delhi, India.
Punit
P
Sharma
Department of Nuclear Medicine, All India Institute of Medical Sciences, New Delhi, India.
Harmandeep
H
Singh
Department of Nuclear Medicine, All India Institute of Medical Sciences, New Delhi, India.
Chetan
C
Patel
Department of Electronics and Communication Engineering, Narula Institute of Technology, Agarpara, Kolkata, West Bengal, India.
Kaushik
K
Sarkar
Department of Nuclear Medicine, All India Institute of Medical Sciences, New Delhi, India.
Rakesh
R
Kumar
Department of Nuclear Medicine, All India Institute of Medical Sciences, New Delhi, India.
Chandra Sekhar
CS
Bal
Image quality; Poisson noise; positron emission tomography-computed tomography; stochastic resonance