Feasibility of a novel IQ-SPECT/CT protocol using thallium-201 acquired in a short time: Comparison with conventional protocols

Objectives An IQ-SPECT protocol using a novel multifocal collimator (Siemens) consists of cardio-centric and 3D iterative SPECT reconstruction. The aims are were to determine the normal uptake in thallium-201 (²⁰¹Tl) SPECT in each acquisition method and to compare the distribution between new and conventional protocols, especially in patients with normal imaging.

Methods Forty patients (male/female: 32/8, mean age of 75 years) who underwent myocardial perfusion imaging were included. All patients who underwent adenosine-stress ²⁰¹Tl perfusion scan in one-day protocol showed normal results. Acquisition was performed with a conventional dual-headed gamma camera system and with an IQ-SPECT system. Imaging was performed with a conventional system followed by IQ-SPECT/computed tomography (CT). Reconstruction was performed with and without X-ray CT-derived attenuation correction (AC). A 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 and QGS software.

Results IQ-SPECT provided good or excellent image quality, although its acquisition time was 6 minutes. 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 decreased significantly in IQ-SPECT with AC (0±0). The apical defect count in IQ-SPECT with AC was lower 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 lower than that from the LEHR collimator (66.9 ±10.7 vs. 62.0 ±13.8, p=0.0009).

Conclusions The images of IQ-SPECT acquired in a short time are equivalent to that of conventional LEHR. The results indicated that the IQ-SPECT system with AC is capable of correcting inferior artifacts in ²⁰¹Tl study with high image quality.

Research Support This study was supported by JSPS Grants-in-Aid for Scientific Research (C) in Japan.