Improvement of image quality using interpolated projection data estimation method in SPECT.
OBJECTIVE
General data acquisition for single photon emission computed tomography (SPECT) is performed in 90 or 60 directions, with a coarse pitch of approximately 4-6 degrees for a rotation of 360 degrees or 180 degrees , using a gamma camera. No data between adjacent projections will be sampled under these circumstances. The aim of the study was to develop a method to improve SPECT image quality by generating lacking projection data through interpolation of data obtained with a coarse pitch such as 6 degrees .


METHODS
The projection data set at each individual degree in 360 directions was generated by a weighted average interpolation method from the projection data acquired with a coarse sampling angle (interpolated projection data estimation processing method, IPDE method). The IPDE method was applied to the numerical digital phantom data, actual phantom data and clinical brain data with Tc-99m ECD. All SPECT images were reconstructed by the filtered back-projection method and compared with the original SPECT images.


RESULTS
The results confirmed that streak artifacts decreased by apparently increasing a sampling number in SPECT after interpolation and also improved S/N ratio of the root mean square uncertainty value. Furthermore, the normalized mean square error values, compared with standard images, had similar ones after interpolation. Moreover, the contrast and concentration ratios increased their effects after interpolation.


CONCLUSIONS
These results indicate that effective improvement of image quality can be expected with interpolation. Thus, image quality and the ability to depict images can be improved while maintaining the present acquisition time and image quality. In addition, this can be achieved more effectively than at present even if the acquisition time is reduced.
Takaki
Akihiro
A
Department of Medical Physics and Engineering, Division of Medical Technology and Science, Course of Health Science, Graduate School of Medicine, Osaka University, Osaka, Japan. taakihiro@ffri.co.jp
Soma
Tsutomu
T
Kojima
Akihiro
A
Asao
Kimie
K
Kamada
Shinya
S
Matsumoto
Masanori
M
Murase
Kenya
K
D001921:Brain / Q000000981:diagnostic imaging; D003545:Cysteine / Q000031:analogs & derivatives; D006801:Humans; D007091:Image Processing, Computer-Assisted; D015609:Organotechnetium Compounds; D019047:Phantoms, Imaging; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*
D015609:Organotechnetium Compounds; C059659:technetium Tc 99m bicisate; D003545:Cysteine