Reduction of small heart effect in pediatric gated myocardial perfusion SPECT

Objectives In pediatric patients ejection fraction (EF) could not be evaluated accurately because of small-heart effect. The purpose of this study was to investigate the optimal reconstruction algorithm and cardiac function evaluation software.

Methods The study group consisted of 66 pediatric patients. The data were reconstructed by using a filtered back projection (FBP) method without the resolution correction (RC) and an iterative method based on ordered subset expectation maximization (OSEM) algorithm with the RC. EF was evaluated using quantitative gated SPECT (QGS) and cardioREPO (FUJIFILM RI Pharma Co. Ltd., Japan; EXINI heart, EXINI Diagnostics, Sweden), which included algorithm for compensating small-heart effect. We compared EF of gated myocardial perfusion SPECT to echocardiographic measurement (Echo).

Results The EF was evaluated using different reconstruction algorithm and cardiac function evaluation software (Table). Small heart (SH) group with end-systolic volume (ESV) < 20ml was 48 of 66 patients and EF was overestimated by the small-heart effect. The effect was suppressed by using OSEM algorithm with RC and cardioREPO. Although no significant difference of EF was observed between Echo and cardioREPO-OSEM with RC in the SH group, the significant difference was observed between Echo and QGS-FBP without RC, QGS-OSEM with RC and cardioREPO-FBP without RC (Fig).

Conclusions Even in pediatric gated myocardial perfusion SPECT, small-heart effect was significantly reduced when OSEM algorithm was used with RC combination with specific algorithm of cardioREPO.