Nuclear myocardial perfusion imaging using thallium-201 with a novel multifocal collimators SPECT/CT device: IQ-SPECT versus conventional protocols in normal subjects

Objective: A novel multifocal collimator, IQ-SPECT (Siemens) consists of cardio-centric and 3D iterative SPECT reconstruction and makes it possible to perform MPI scans in a short time. The aims are to delineate the normal uptake in thallium-201 (Tl) SPECT in each acquisition method and to compare the distribution between new and conventional protocol, especially in patients with normal imaging. Methods: Forty patients (eight women, mean age of seventy-five years) who underwent myocardial perfusion imaging were included in the study. All patients underwent one-day protocol perfusion scan after an adenosine-stress test and at rest after administrating Tl and showed normal results. Acquisition was performed on a Symbia T6 equipped with a conventional dual-headed gamma camera system (Siemens ECAM) and with a multifocal collimator called IQ-SPECT. Imaging was performed with a conventional system followed by IQ-SPECT/computed tomography (CT). Reconstruction was performed with or without X-ray CT-derived attenuation correction (AC). Two nuclear physicians blinded to clinical information interpreted all MPI studies. A semi-quantitative myocardial perfusion was analyzed by a 17-segment model with a 5-point visual scoring. The uptake of each segment was measured and left ventricular functions were analyzed by QPS software. Results: IQ-SPECT provided good or excellent image quality. IQ-SPECT images without AC were similar to those of conventional LEHR study. Mid-inferior defect score (0.3±0.5) in conventional LEHR study was increased significantly in IQ-SPECT with AC (0±0). IQ-SPECT (AC) improved the mid-inferior decreased perfusion shown in conventional images. The apex in IQ-SPECT (AC) was decreased compared to that in LEHR (0.1±0.3 vs. 0.5±0.7, p<0.05). The left ventricular ejection fraction from IQ-SPECT was significantly higher than that from the LEHR collimator (p=0.0009). Conclusion: The images of IQ-SPECT acquired in a short time are equivalent with that of conventional LEHR. The results indicated that the IQ-SPECT system with attenuation correction is capable of correcting inferior artifacts with high image quality. (Ann Nucl Med)