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Cardiac sarcoidosis is potentially fatal and hence requires a precise diagnosis. We performed dual 67Ga (Ga)-99mTc-sestamibi (Tc) single-photon emission CT (SPECT) scans by superimposing a Ga-SPECT image on the myocardial outline traced with Tc. The usefulness of this imaging technique in the diagnosis of cardiac sarcoidosis was studied. The subjects in this study were 14 patients with sarcoidosis (mean [± SD] age, 52 ± 16 years; 5 men and 9 women). An IV dose of Tc (74 MBq per 2 mL) was injected into patients 72 h after an IV dose of Ga (111 MBq per 3 mL) was injected. The dual SPECT scan was performed 30 min after the Tc dose was administered. The energy used for collection was 93 keV for Ga and 140 keV for Tc. The myocardial outline was successfully traced in all subjects, allowing us to check for myocardial Ga uptake and to identify its location. Abnormal Ga uptake in the myocardium was observed in 9 of the 14 subjects. In seven of these nine subjects, the location of the abnormal myocardial Ga uptake was identical to the location of reduced Tc uptake. Abnormal Ga uptake disappeared in all cases following steroid therapy. Of the five subjects who were free of abnormal Ga uptake, two showed reduced Tc uptake, and these two subjects had been receiving steroid therapy. These re- suits suggest that dual SPECT scanning using Ga and Tc represents a very useful diagnostic imaging technique since it improves the diagnostic capability of Ga-SPECT to allow the highly specific diagnosis of cardiac sarcoidosis. [ABSTRACT FROM AUTHOR]

Objectives: CT data can be used for both anatomical image and attenuation correction (CTAC) of PET data in PET-CT scanners. The CTAC method is useful for attenuation correction, because the CT scan time is much shorter than the external radionuclide (e.g., (68)Ge) transmission scan time. However, the energy of the X-rays from CT is not monoenergetic and is much lower than that of the external radionuclide source. In this study, we evaluated the differences between emission PET images reconstructed with CT-based and (68)Ge-based attenuation correction., Methods: CT scans and (68)Ge-Transmission scans were acquired and used for attenuation correction (CTAC, MAC, and SAC). The PET emission scan time was 4 min. CT scans were acquired at 10, 20, 40, 80, and 160 mA. (68)Ge-Transmission scans were acquired at 1, 3, 5, 10, 20, 40, 60, and 300 min. The attenuation-corrected emission image using MAC on a 300 min transmission scan was defined as the reference image. Seven cylinders (30 mm diameter) were filled with (18)F-FDG placed in a heart-liver phantom with simulated pulmonary mass lesions. The PET value [counts/cc] was measured in circular regions of interest (ROI) over the cylindrical mass lesion. Averages [counts/cc], coefficients of variation [C.V.(%)], and ratios of difference [%Diff] from the reference value were calculated for all conditions., Results: In the CT-Transmission, analysis of variance revealed no significant effect of CT current on the average and the C.V. In the (68)Ge-Transmission, the average and the C.V. changed in dependence on the acquisition time. All %Diff using CT-Transmission were small. It was shown that CT-Transmission is more appropriate than (68)Ge-Transmission.