1Dept. of Medical Physics, Tarbiat Modarres University, Tehran, Iran,
2Dept. of Nuclear Medicine, Rajaei Heart Center, Tehran, Iran
*Correspondence to: H. Rajabi, Dept. of Medical Physics, Tarbiat Modarres University, Tehran-Iran Tel: 0098-21-8011001 Fax: 0098-21-8006544, P.O. Box: 14115-331 E-mail: hrajabi@modares.ac.ir
Selection of proper filter is a headache in processing myocardial perfusion SPECT data particularly when filtered back-projection is being used. Two types of filter are generally used, low-pass and resolution recovery filters. Metz and Wiener are two typical restoration recovery filters. Butterworth and Banning are two typical smoothing filters. In the present study we examined these filters to find the one that produces more consistent results compared to angiographical findings.
A total of 55 patients' data were selected. All had angiography report within + 2 weeks of the test. Angiographers determined the locations of abnormality on myocardium. Different filter were applied to the data and contrast at the defected location were calculated. The filter that produced maximum contrast was assumed to be more consistent with angiography.
Calculation of contrast on all the patients' data showed that maximum contrast between normal and defected myocardium could be obtained using the Metz (FWHM 3.5–4.5 pixel, orders of 8–9.5), Wiener (FWHM 3.5–4), Butterworth (cutoff 0.3–0.5, order 3–9) and Hanning (cutoff 0.43–0.5).
The results of Metz filter better matched with the angiography. No relationship observed between the FWHM used in Metz and Wiener filter and systemic FWHM calculated from phantom study.
