Characteristics of normal myocardial perfusion distribution derived from the IQ-SPECT system: A comparison between gender-combined and specific databases

Objectives Half-time and quarter-time single-photon emission computed tomography (SPECT) scans obtained using the IQ-SPECT system may improve the radiopharmaceutical radiation dose for patients, motion artifacts during SPECT imaging and the patient throughput time. Therefore, nuclear medicine physicians and cardiologists need to be trained additionally for interpretation of the IQ-SPECT image. The aim of this study was to characterize myocardial perfusion distribution derived from the IQ-SPECT.

Methods We have enrolled 159 patients (67 women and 92 men) with a low likelihood of coronary artery disease (CAD). The study was conducted at four hospitals in Japan, where thallium-201 (²⁰¹Tl) based studies were used in practice. All patients underwent ²⁰¹Tl myocardial perfusion SPECT/CT using the IQ-SPECT system and the short-time acquisition protocol. Projection data were reconstructed using ordered subset conjugate gradient minimization (OSCGM) method with or without X-ray CT for attenuation correction (AC) and a dual-energy method for scatter correction (SC). For the evaluation of characteristics of segmental normal myocardial perfusion, polar maps segmented in 17 regions were generated with QPS software. Normal database was created using a database generator.

Results Regarding the normal databases with no correction, gender differences in the mean myocardial count were observed in the inferior and inferoseptal walls (higher in women than in men, p < 0.04). The anterolateral count was higher in men than in women (p < 0.02). Since the IQ-SPECT system with AC and SC provided near-homogeneous myocardial perfusion except in the apex segment (76% for men vs 79% for women, p = 0.046), gender-combined normal database was created. No segmental difference in mean myocardial count was observed between gender-combined and gender-specific normal databases with AC and SC (p = ns in all segments). Concerning segmental differences between gender-combined database and gender-specific normal database without AC and SC, mean myocardial counts at the apex decreased by 15% for men and 19% for women in gender-combined normal database.

Conclusions Although IQ-SPECT system with no correction yielded gender differences in the mean myocardial count, that with AC and SC showed a near-homogeneous myocardial perfusion distribution for both genders. Myocardial perfusion distribution was differed in gender-combined database and gender-specific database without AC and SC. ²⁰¹Tl IQ-SPECT scan could be feasible in a short time acquisition by taking the characteristics of normal myocardial perfusion distribution into consideration.