Scatter and attenuation correction in technetium-99m brain SPECT.
We propose a practical method for scatter and attenuation compensation in 99mTc-ECD brain SPECT using a simultaneous emission CT (ECT) and transmission CT (TCT) acquisition system that includes the following major components: (a) triple-headed SPECT gamma camera equipped with fanbeam collimators; (b) external line sources containing 99mTc placed at the focal lines of the collimators; and (c) scatter correction by the triple-energy-window (TEW) method.


METHODS
Projection images were obtained over a 360 degrees rotation scan. After acquisition, scatter correction was performed using the TEW method, which corrected scattered photons pixel by pixel in the projection data. Scatter-corrected ECT images were compensated for attenuation using the TCT images with Chang's iterative method, and were converted to activity concentration (kBq/ml) images by obtaining a cross-calibration scan. After validating this method with phantom studies, it was applied to clinical brain imaging using a combination of 925 MBq 99mTc-ECD as a radiopharmaceutical and 222 MBq 99mTc as an external source. ECT and TCT data were acquired separately or simultaneously.


RESULTS
SPECT quantification and image quality were improved by performing this correction. The activity concentration images obtained with the simultaneous acquisition were almost identical to those obtained with the separate acquisition.


CONCLUSIONS
This method was clinically practical and cost-effective for reconstructing quantitative 99mTc brain SPECT images.
Hashimoto
J
J
Department of Radiology, School of Medicine, Keio University, Tokyo, Japan.
Kubo
A
A
Ogawa
K
K
Amano
T
T
Fukuuchi
Y
Y
Motomura
N
N
Ichihara
T
T
D001921:Brain / Q000000981:diagnostic imaging*; D003545:Cysteine / Q000031:analogs & derivatives*; D006801:Humans; D015609:Organotechnetium Compounds; D017785:Photons; D011829:Radiation Dosage; D012542:Scattering, Radiation; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*
D015609:Organotechnetium Compounds; C059659:technetium Tc 99m bicisate; D003545:Cysteine