Usefulness of Serial Dual Isotope SPECT of ¹²³I-BMIPP and ²⁰¹TICI

Abstract

To avoid the influence of cross-talk photons, we developed a new scanning method of ¹²³I-BMIPP and ²⁰¹TlCl myocardial SPECT named“serial dual isotope SPECT”and estimated the usefulness and accuracy of the cross-talk correction. This imaging method consisted of the two serial SPECT : the routine ¹²³I-BMIPP SPECT started at 30 min after the injection of ¹²³I-BMIPP and the dual isotope SPECT started sequentially at 10 min after the injection of ²⁰¹TlCl. The second SPECT provided the ²⁰¹TlCl image (71±7 keV) with scattering photons from ¹²³I-BMIPP. The real ²⁰¹TlCl image without scattering photons was obtained by subtracting the scattering image of the first SPECT from the ²⁰¹TlCl image with scattering photons. To evaluate the accuracy and the usefulness of this method, we carried out a fundamental experiment using filter papers soaked with the individual radiopharmaceutical and an acrylic phantom as a scattering material with the same process. The result showed that the corrected ²⁰¹TlCl image was almost equal to the real ²⁰¹TlCl image in terms of image counts and image profiles. In the myocardial phantom and the clinical study, the correction images showed good agreements with the real ²⁰¹TlCl images of the patient in count profile, polar map, image-contrast and background level. In the phantom study, less than three pixels (about 1.5cm) differences between the first SPECT and the second SPECT were permitted to generate the reliable corrected ²⁰¹TlCl SPECT. The most important advantage of this method is that the difference of photon scattering in individual patients can be corrected perfectly.