Improved quantification of small hearts for gated myocardial perfusion imaging

Abstract

PurposeIn patients with a small heart, defined as an end-systolic volume (ESV) of ≤20 mL calculated using the Quantitative Gated SPECT (QGS) program, underestimation of ESV and overestimation of ejection fraction (EF) using gated myocardial perfusion imaging are considered errors caused by inappropriate delineation of the left ventricle (LV). The aim of this study was to develop a new method for delineation of the LV and to evaluate it in studies using a digital phantom, normal subjects and patients.MethodsThe active shape-based method for LV delineation, EXINI heart (ExH), was adjusted to more accurately process small hearts. In small hearts, due to the partial volume effect and the short distance to the opposite ventricular wall, the endocardial and the epicardial surfaces are shifted in the epicardial direction depending on the midventricular volume. The adjusted method was evaluated using digital XCAT phantoms with Monte Carlo simulation (8 virtual patients), a Japanese multicentre normal database (69 patients) and consecutive Japanese patients (116 patients). The LV volumes, EF and diastolic parameters derived from ExH and QGS were compared.ResultsThe digital phantom studies showed a mean ESV of 87 % ± 9 % of the true volume calculated using ExH and 22 % ± 18 % calculated using QGS. In the normal database, QGS gave higher EFs in women than in men (71.4 ± 6.0 % vs. 67.2 ± 6.0 %, p = 0.0058), but ExH gave comparable EFs (70.7 ± 4.9 % and 71.4 ± 5 % in men and women, respectively, p = ns). QGS gave higher EFs in subjects with a small heart than in those with a normal-sized heart (74.5 ± 5.1 % vs. 66.1 ± 4.9 %), but ExH gave comparable values (70.0 ± 5.9 % vs. 71.6 ± 4.2 %, respectively, p = ns). In consecutive patients, the average EFs with QGS in patients with ESV >20 mL, 11–20 mL and ≤10 mL were 57.9 %, 71.9 % and 83.2 %, but with ExH the differences among these groups were smaller (65.2 %, 67.8 % and 71.5 %, respectively).ConclusionThe volume-dependent edge correction algorithm was able to effectively reduce the effects on ESV and EF of a small heart. The uniform normal values might be applicable to both men and women and to both small and normal-sized hearts.

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

“…LV delineation in diastole using IQ-SPECT underestimates EDV and resulted in decreased LVEF. The relatively higher frequency of small hearts in this study population might be one of the factors [28]. The finding of this study suggested that this technical problem requires further investigation [28][29].…”

The effect of end-systolic volume on ejection fraction in gated myocardial perfusion scintigraphy

“…However, it is hard to explain why were ESV values so small (even zero) in some patients in our study. Nakajima et al 16 compared EF, EDV and ESV values of patients with small hearts, using QGS and EXINI programs, with that of a digital phantom and with the data analysis results of the Japanese Society of Nuclear Medicine (JSNM) group, performed in 2007. The main outcome of the study was that the EF values calculated by the QGS program were found to be higher than those calculated by the EXINI program.…”

Ready, shoot, aim? Summary justice for small hearts in nuclear cardiology

“…The shift is inversely proportional to the measured midventricular LV cavity volume, ranging from 3.5 mm at 0 mL (effectively ''guessing'' a cavity where one cannot be seen) to 0 mm at 85 mL, where spillover is deemed to have abated (see Figure 1 and Ref. 12).…”