New approach for attenuation correction in SPECT images, using linear optimization

Background: Photon attenuation as an inevitable physical phenomenon influences on the diagnostic information of SPECT images and results to errors in accuracy of quantitative measurements. This can be corrected via different physical or mathematical approaches. As the correction equation in mathematical approaches is nonlinear, in this study a new method of linearization called ‘Piece Wise Linearization’ (PWL) is introduced and to substantiate its validity for SPECT image reconstructions, a phantom study is performed. Material and Methods: A SPECT scan of a homemade heart phantom filled with 2 mCi 99mTc was acquired by dual head Siemens E.Cam gamma camera equipped with LEHR collimator. Row data of the scan were transferred in DICOM format to a pc computer for reconstruction of the images using MLEM iterative algorithm in Matlab software. Result: Attenuation map of the phantom were derived using PWL with linear optimization approach. Based on that, the attenuation corrected SPECT image of the phantom were reconstructed and compared with non-corrected image, using MLEM iterative algorithm. Comparison of the corrected and non-corrected images confirmed with CT attenuation correction method. Conclusion: Attenuation correction in SPECT image can be achieved successfully, using emission data and piecewise linearization with linear optimization approach. The corrected image of and attenuation map of the heart phantom using this approach promise acceptable image quality for diagnostic clinical use. Iran. J. Radiat. Res., 2010; 8 (2): 111­116