Segmental and global left ventricular function assessment using gated SPECT with a semiconductor Cadmium Zinc Telluride (CZT) camera: Phantom study and clinical validation vs cardiac magnetic resonance

Background

We evaluated gated-SPECT using a Cadmium-Zinc-Telluride (CZT) camera for assessing global and regional left ventricular (LV) function.

Methods

A phantom study evaluated the accuracy of wall thickening assessment using systolic count increase on both Anger and CZT (Discovery 530NMc) cameras. The refillable phantom simulated variable myocardial wall thicknesses. The apparent count increase (%CI) was compared to the thickness increase (%Th). CZT gated-SPECT was compared to cardiac magnetic resonance (CMR) in 27 patients. Global and regional LV function (wall thickening and motion) were quantified and compared between SPECT and CMR data.

Results

In the phantom study using a 5-mm object, the regression between %CI and %Th was significantly closer to the line of identity (y = x) with the CZT (R ² = 0.9955) than the Anger (R ² = 0.9995, P = .03). There was a weaker correlation for larger objects (P = .003). In patients, there was a high concordance between CZT and CMR for ESV, EDV, and LVEF (all CCC >0.80, P < .001). CZT underestimated %CI and wall motion (WM) compared to CMR (P < .001). The agreement to CMR was better for WM than wall thickening.

Conclusion

The Discovery 530NMc provided accurate measurements of global LV function but underestimated regional wall thickening, especially in patients with increased wall thickness.     

Characterization of mechanical dyssynchrony measured by gated single photon emission computed tomography phase analysis after acute ST-elevation myocardial infarction

Background

Left ventricular dyssynchrony is an adverse consequence of ST-elevation myocardial infarction (STEMI) and bears an unfavorable prognosis. Mechanical dyssynchrony as measured by phase analysis from gated single photon emission computed tomography (GSPECT) correlates well with other imaging methods of assessing dyssynchrony but has not been studied in STEMI. We hypothesized that systolic dyssynchrony as measured by GSPECT would correlate with adverse remodeling after STEMI.

Methods

In 28 subjects suffering STEMI, GSPECT with technetium-99m sestamibi was performed immediately after presentation (day 5) and remotely (6 months). Parameters of left ventricular dyssynchrony (QRS width, histogram bandwidth (HBW) and phase standard deviation (PSD)) were measured from GSPECT using the Emory Cardiac Toolbox. Left ventricular volumes, ejection fraction (LVEF) and infarct size were also assessed.

Results

After successful primary percutaneous coronary intervention to the infarct-related artery, subjects had an LVEF of 46.4% ± 11% and a resting perfusion defect of 27.4% ± 16% at baseline. Baseline QRS width was normal (91.5 ± 17.5 ms). Subjects with STEMI had dyssynchrony compared with a cohort of 22 normal subjects (age 57.2 ± 10.6 years, <5% perfusion defect) by both HBW (100.3° ± 70.7° vs 26.5° ± 5.3°, P < .0001) and PSD (35.3° ± 16.9° vs 7.9° ± 2.1°, P < .0001). Baseline HBW correlated with resting perfusion defect size (r = 0.67, P < .001), end-systolic volume (r = 0.72, P < .001), end-diastolic volume (r = 0.63, P = .001), and inversely with LVEF (r = ?0.74, P < .001). HBW and PSD improved over the follow-up period (?24.1 ± 35.9 degrees, P = .003 and ?8.7° ± 14.6°, P = .006, respectively), and improvement in HBW correlated with reduction in LV end-systolic volumes (r = 0.43, P = .034). Baseline HBW and PSD, however, did not independently predict LVEF at 6 months follow-up.

Conclusions

After STEMI, subjects exhibit mechanical dyssynchrony as measured by GSPECT phase analysis without evidence of electrical dyssynchrony. Improvement in mechanical dyssynchrony correlates with beneficial ventricular remodeling. The full predictive value of this measure in post-infarct patients warrants further study.     

Hybrid cardiac SPECT/64-slice CTA-derived LV function parameters: Correlation and reproducibility assessment

The purpose of this study is to define the relationship between SPECT and CTA measured parameters of left ventricular (LV) function and volumes obtained in a single session using SPECT/64-slice CT hybrid imaging device, and in addition, to assess the reproducibility of LV parameters measured using 64-slice CTA.

Materials and methods

Seventy-six patients with suspected or known coronary artery disease underwent cardiac CTA and GSPECT in one session using a hybrid SPECT/CT device.LV end-diastolic volume (EDV), end-systolic volume (ESV) and ejection fraction (EF) were measured on each component of the hybrid device. For the CTA component, these parameters were re-measured by the same investigator and by a second investigator with an interval of 3-54 weeks. Corresponding GSPECT and CTA measured parameters were compared. For CTA, intra-observer and inter-observer variability of LV function and volume measurements were calculated.

Results

A very good correlation was found between the GSPECT and CTA measured LVEF (r = 0.81), ESV (r = 0.90) and EDV (r = 0.82). There was a small positive difference by CTA measured LVEF (3.9 ± 14.2%), and more prominent positive differences by CTA measured ESV and EDV (9.8 ± 14.8 and 44.9 ± 23.1 cm³, respectively). There was excellent reproducibility in the measurements of all parameters with very low intra- and inter-observer variability (r = 0.93 for EF and 0.98 for EDV and ESV).

Conclusions

Although a good correlation was found between the EF measurements obtained from CTA and SPECT, interchangeable use of EF measurements between the two modalities should be done cautiously and interchangeable use of LV EDV and ESV should be avoided.     

Performance of OSEM and depth-dependent resolution recovery algorithms for the evaluation of global left ventricular function in 201Tl gated myocardial perfusion SPECT.

It is unknown whether the use of ordered-subsets expectation maximization (OSEM) and depth-dependent resolution recovery (RR) will increase the accuracy of (201)Tl electrocardiogram-gated SPECT (GSPECT) for the measurement of global left ventricular (LV) function. METHODS: Fifty-six patients having both rest (201)Tl GSPECT and planar equilibrium radionuclide angiography (planar(RNA)) on the same day were studied. Twenty-nine patients also had LV conventional contrast angiography (Rx). LV ejection fraction (LVEF), end-diastolic volume (EDV), and end-systolic volume (ESV) were calculated with the quantitative gated SPECT software (QGS) using 4 different processing methods: filtered backprojection (FBP), OSEM, RR + FBP, and RR + OSEM. LVEF calculated with planar(RNA) and LV EDV and ESV calculated with Rx were considered gold standards. LVEF and volumes provided with the GSPECT methods were compared with the gold standard methods. RESULTS: LVEF calculated with GSPECT methods (FBP, OSEM, RR + FBP, and RR + OSEM) were similar (not statistically significant) and correlated well with planar(RNA). On Bland-Altman analysis, the mean +/- SD of absolute difference in LVEF with GSPECT FBP, OSEM, RR + FBP, and RR + OSEM methods versus planar(RNA) were similar, with relatively large limits of agreement. LV volumes calculated with the 4 GSPECT methods were significantly lower but correlated well with Rx LV volumes. LV volumes calculated with FBP and OSEM were lower than those calculated with RR + FBP and RR + OSEM (P < 0.01). On Bland-Altman analysis, the mean +/- SD of absolute difference in LV volumes with FBP, OSEM, RR + FBP, and RR + OSEM versus Rx was, respectively, 56 +/- 45 mL (P < 0.01 vs. the other 3 methods), 57 +/- 45 mL (P < 0.01 vs. the other 3 methods), 43 +/- 48 mL, and 46 +/- 47 mL, with correspondingly large limits of agreement. The variance of random error did not differ between FBP, OSEM, RR + FBP, and RR + OSEM for either LVEF or volumes. CONCLUSION: OSEM and FBP presented similar accuracy for LVEF and volume measured with the QGS software. Their combination with depth-dependent RR provided similar LVEF but more accurate LV volumes.     

Detection of post-exercise stunning by early gated SPECT myocardial perfusion imaging: Results from the IAEA multi-center study

Background

Transient post-ischemic LV dysfunction due to myocardial stunning in patients with coronary artery disease can be missed by conventional gated SPECT (GSPECT) acquisitions. The aim of this IAEA-sponsored multi-center study was to determine whether early post-exercise imaging is more likely to detect stunning than conventional without adversely affecting image quality or perfusion information.

Methods and Results

Patients undergoing exercise/rest GSPECT were enrolled in this international multicenter study. Post-exercise studies were acquired at 15 ± 5 minutes after radiotracer injection (Stress-1) and repeated at 60 ± 15 minutes (Stress-2). Rest studies (R) were acquired at 60 minutes post injection. A core laboratory quantitatively assessed perfusion pattern and LV blinded to the acquisition time. Ischemia was defined as summed stress score (SDS) ≥4, and stunning was defined as the difference between rest and post-stress LVEF (Δ-LVEF). In the 229 patients enrolled into the study, both image quality and perfusion information were similar between Stress-1 and Stress-2. Post-stress LVEF was associated with both ischemia and time of acquisition, with a significant correlation between SDS and Δ-LVEF, which was stronger at Stress-1 than Stress-2 in the ischemic compared to the non-ischemic population (r = 0.23 vs 0.08, P = 0.10).

Conclusions

Early post-exercise imaging is feasible, and can potentially improve the detection of post-ischemic stunning without compromising image quality and perfusion data     

Comparison of two three-dimensional gated SPECT methods with thallium in patients with large myocardial infarction

BACKGROUND: Two different commercially available gated single photon emission computed tomography (GSPECT) methods were compared in a population of patients with a major myocardial infarction. METHODS: Rest thallium GSPECT was performed with a 90-degree dual-detector camera, 4 hours after injection of thallium-201 (Tl-201; 185 MBq) in 43 patients (mean age, 62+/-12 years) with a large myocardial infarction (mean defect size, 33%+/-16%). End-diastolic volume (EDV), end-systolic volume (ESV), and left ventricular ejection fraction (LVEF) were calculated by using QGS (Cedars Sinai) and MultiDim (Sopha Medical Vision International, Buc, France). Images were reconstructed by using a 2.5 zoom and a Butterworth filter (order, 5; cut-off frequency, 0.20). LVEF was calculated in all patients by using equilibrium radionuclide angiocardiography (ERNA). EDV, ESV, and LVEF were also measured by using left ventriculography (LVG). RESULTS: Compared with LVG, QGS underestimated LVEF by means of an underestimation of mean EDV. MultiDim overestimated EDV and ESV. GSPECT EDV and ESV overestimation was demonstrated by means of Bland-Altman analysis to increase with left ventricular volume size (P<.05). The difference between LVG and GSPECT volumes was demonstrated by means of regression analysis to be correlated with infarction size. This effect was particularly important with MultiDim (P<.0001). CONCLUSION: In Tl-201 GSPECT, LVEF and volume measurements will vary according to the type of software used.     

Evaluation of ECG-gated [<Superscript>11</Superscript>C]acetate PET for measuring left ventricular volumes,mass, and myocardial external efficiency

Background

Noninvasive estimation of myocardial external efficiency (MEE) requires measurements of left ventricular (LV) oxygen consumption with [¹¹C]acetate PET in addition to LV stroke volume and mass with cardiovascular magnetic resonance (CMR). Measuring LV geometry directly from ECG-gated [¹¹C]acetate PET might enable MEE evaluation from a single PET scan. Therefore, we sought to establish the accuracy of measuring LV volumes, mass, and MEE directly from ECG-gated [¹¹C]acetate PET.

Methods

Thirty-five subjects with aortic valve stenosis underwent ECG-gated [¹¹C]acetate PET and CMR. List mode PET data were rebinned into 16-bin ECG-gated uptake images before measuring LV volumes and mass using commercial software and compared to CMR. Dynamic datasets were used for calculation of mean LV oxygen consumption and MEE.

Results

LV mass, volumes, and ejection fraction measured by CMR and PET correlated strongly (r = 0.86-0.92, P < .001 for all), but were underestimated by PET (P < .001 for all except ESV P = .79). PET-based MEE, corrected for bias, correlated fairly with PET/CMR-based MEE (r = 0.60, P < .001, bias ?3 ± 21%, P = .56). PET-based MEE bias was strongly associated with LV wall thickness.

Conclusions

Although analysis-related improvements in accuracy are recommended, LV geometry estimated from ECG-gated [¹¹C]acetate PET correlate excellently with CMR and can indeed be used to evaluate MEE.

     

Repeatability of automatic left ventricular cavity volume measurements from myocardial perfusion SPECT

Background

This study sought to assess the repeatability of automatic quantitative measurements of left ventricular (LV) cavity volumes in a large patient population (N=926), to correlate those measurements to similarly obtained LV ejection fraction (LVEF) measurements, and to investigate the relationship between ungated and gated volumes.

Methods

All 926 patients underwent ungated single photon emission computed tomography (SPECT) immediately followed by 8-frame gated SPECT. LV cavity volumes were automatically measured from ungated (V), summed gated (SUMV), end-systolic (ESV) and end-diastolic (EDV) images, and LVEFs derived from the latter 2.

Results

Repeatability (SUMV vs V) was very good overall (6.4%±6.6%), further improving for volumes >25 mL (5.7%±5.5%) and >40 mL (5.2%±5.0%). Exponential regression between ESV and LVEF (r=0.925, SEE=15.0 mL) EDV and LVEF (r=0.802, SEE=24.2 mL), and SUMV and LVEF (r=0.867, SEE=19.7 mL) was also very good. Summed gated volumes were closer to ESV than to EDV (43.3%±8.8% of EDV-ESV range). SUMV <50 mL and SUMV >110 mL were good substitutes for LVEF >50% and LVEF <40% (93.4% and 97.1%, respectively).

Conclusion

Automatic quantitative measurements of gated and ungated volumes with our algorithm are repeatable, correlate well with other global myocardial parameters, and may contribute important additional information to that conventionally provided by myocardial perfusion SPECT studies.     

The agreement of left ventricular function parameters between 99mTc-tetrofosmin gated myocardial SPECT and gated myocardial MRI

Objective

The aim is to compare and evaluate the agreement of quantification of left ventricular functional parameters obtained by two different methods, ^99mTc-tetrofosmin gated myocardial perfusion SPECT (MPS) and cardiac magnetic resonance imaging (CMR).

Methods

Ten healthy male volunteers participated. Gated MPS data were acquired using 32 frames, which were also combined into 16- and 8-frame data set for the investigation. Gated CMR data were acquired using 8, 16 and 32-frame for the different sets. All examinations were conducted in resting and at exercise conditions. Quantitative measurements of end-diastolic volume (EDV), end-systolic volume (ESV), left ventricular ejection fraction (LVEF), peak ejection rate (PER), peak filling rate (PFR) and time to peak filling (TTPF) were done for each study, respectively. Finally, we evaluated the concordance of parameters between gated MPS and gated CMR by % difference and Bland?CAltman plot analysis.

Results

LVEF showed favorable concordance in both rest and exercise conditions (% differences were around 10%). PER, PFR and TTPF also showed good concordances in rest conditions, under 32-frame gated collections particularly (% differences were around 10%). In exercise conditions, although the concordances were relatively good, certain variances were noted (% differences were around 20?C25%). Regarding left ventricular volumes, the concordance were worse in both conditions (% differences were around 30?C40%).

Conclusions

In quantifying of left ventricular function parameter, gated CMR provides similar quantitative values comparing with gated MPS except for ventricular volumes in rest conditions. In contrast, there were certain variations except for LVEF in exercised examinations. When we follow patients by the same cardiac parameters with CMR and MPS, using parameters across the two modalities proved to be possible under rest condition. However, it is limited at exercise condition.     

Cardiac MRI: evaluation of phonocardiogram-gated cine imaging for the assessment of global und regional left ventricular function in clinical routine

Objectives

To validate a phonocardiogram (PCG)-gated cine imaging approach for the assessment of left ventricular (LV) function.

Methods

In this prospective study, cine MR imaging of the LV was performed twice in 79 patients by using retrospectively PCG- and retrospectively ECG-gated cine SSFP sequences at 1.5?T. End-diastolic volumes (EDV), end-systolic volumes (ESV), stroke volumes (SV), ejection fraction (EF), muscle mass (MM), as well as regional wall motion were assessed. Subgroup analyses were performed for patients with valvular defects and for patients with dysrhythmia.

Results

PCG-gated imaging was feasible in 75 (95%) patients, ECG-gating in all patients. Excellent correlations were observed for all volumetric parameters (r?>?0.98 for all variables analysed). No significant differences were observed for EDV (?0.24?±?3.14?mL, P?=?0.5133), ESV (?0.04?±?2.36?mL, P?=?0.8951), SV (?0.20?±?3.41?mL, P?=?0.6083), EF (?0.16?±?1.98%, P?=?0.4910), or MM (0.31?±?4.2?g, P?=?0.7067) for the entire study cohort, nor for either of the subgroups. PCG- and ECG-gated cine imaging revealed similar results for regional wall motion analyses (115 vs. 119 segments with wall motion abnormalities, P?=?0.3652).

Conclusion

The present study demonstrates that PCG-gated cine imaging enables accurate assessment of global and regional LV function in the vast majority of patients in clinical routine.

Key Points

• Phonocardiogram-gating is an alternative to electrocardiographic-gating in cardiac MR.
• Phonocardiogram-gated imaging allows reliable assessment of global and regional left-ventricular function.
• Phonocardiogram-gating is feasible in patients with valvular lesions or cardiac dysrhythmia.
• Because phonocardiogram-gating is insensitive to magneto-hydrodynamic effects, it is suitable for ultra-high field.

     

Does the amplatzer septal occluder device alter ventricular contraction pattern? A ventricular motion analysis by MR tagging

Purpose:

To assess by cardiovascular magnetic resonance (CMR) and CMR tagging if the Amplatzer Septal Occluder affects right ventricular (RV) and left ventricular (LV) motion pattern.

Materials and Methods:

Sixteen consecutive patients with significant atrial septal defect (ASD) and nine consecutive patients with persistent foramen ovale (PFO) as controls were studied before and a median of 14 days after defect closure by an Amplatzer occluder. By CMR end‐diastolic (EDV) and end‐systolic (ESV) RV and LV volumes were determined. Aortic and pulmonary artery flow was measured for assessment of left‐to‐right shunt (Qp/Qs). By CMR tagging circumferential strain and radial shortening, maximal rotation and torsion were measured,

Results:

In ASD patients RV‐EDV and RV‐ESV decreased (P < 0.05). LV‐EDV and LV‐ESV increased after ASD closure (P < 0.005). Qp/Qs dropped from 1.8 to 1.0 (P < 0.001). PFO patients showed no ventricular volume change after PFO closure. In ASD patients circumferential strain and radial shortening and maximal rotation of the RV decreased by ASD closure (P < 0.01). In LV only maximal rotation at the base and apex decreased significantly (P < 0.05). Torsion remained constant. In PFO patients no tagging parameter changed after defect closure.

Conclusion:

The Amplatzer occluder itself does not change the ventricular contraction pattern. All volume and myocardial deformation changes were caused by ventricular loading shifts. J. Magn. Reson. Imaging 2012;35:949–956. © 2012 Wiley Periodicals, Inc.     

Cardiovascular magnetic resonance imaging assessment of diastolic dysfunction in a population without heart disease: a gender-based study

Objectives

Asymptomatic left ventricular (LV) diastolic dysfunction is increasingly recognised as an important diagnosis. Our goal was to study the prevalence and gender differences in subclinical LV diastolic dysfunction, using cardiovascular magnetic resonance imaging (CMR) at 3 T.

Methods

We prospectively studied 48 volunteers (19 male and 29 female, mean age 49?±?7 years) with no evidence of cardiovascular disease. We used CMR to measure left atrium (LA) and LV volumes, LV peak filling rate and transmitral flow.

Results

The overall prevalence of LV diastolic dysfunction in our cohort varied between 20 % (based on evaluation of LV filing profiles) and 24 % (based on the evaluation of the transmitral flow). The prevalence of diastolic dysfunction was higher in men than in women, independently of the criteria used (P between 0.004 and 0.022). Indexed LV end-diastolic volume, indexed LV stroke volume, indexed LV mass, indexed LA minimum volume and indexed LA maximum volume were significantly greater in men than in women (P?<?0.05). All the subjects had LV ejection fractions within the normal range.

Conclusions

It is clinically feasible to study diastolic flow and LV filling with CMR. CMR detected diastolic dysfunction in asymptomatic men and women.

Key Points

? CMR imaging offers new possibilities in assessing left ventricular diastolic function. ? The prevalence of diastolic dysfunction is higher in men than in women. ? The prevalence of some diastolic dysfunction in a normal population is 24 %.     

Use of gated 13N-NH3 micro-PET to examine left ventricular function in rats

IntroductionMyocardial perfusion gating techniques offer the possibility of measurement of left ventricular end-systolic (ESV) and end-diastolic volume (EDV) and left ventricular ejection fraction (LVEF) in clinical and preclinical trials. The aim of this study was to evaluate left ventricular volumes (LVV) and LVEF with ¹³N-NH₃ in comparison with the reference ¹⁸F-FDG in different rat models.MethodsIn this study, 18 male Wistar rats, 12 control rats and 6 rats with myocardial infarction (MI) were imaged with micro-PET. The ratswere scanned with gated ¹³N-NH₃ and ¹⁸F-FDG sequentially for the assessment of LVV and LVEF. A validated three-dimensional segmentation algorithm was used to calculate LVV and LVEF.ResultsMean LVEF measured with ¹³N-NH₃ was 45.6±8.9 and 75.3±9.4%, mean ESV was 0.40±0.12 and 0.14±0.11 ml, and mean EDVwas 0.53±16 and 0.75±0.18 ml for MI and control rats, respectively. Moderate to good correlations were observed between values of ¹³N-NH₃ and ¹⁸F-FDG for calculation of ESV [r=0.80, P<.0001, standard error of estimate (SEE)=0.10], EDV (r=0.63, P=.005, SEE=0.14) and LVEF (r=0.84, P<.0001, SEE=9.5). LVEF measured with ¹³N-NH₃ was significantly lower in MI rats in comparison to measurement with ¹⁸F-FDG (45.6±8.9 vs 54.9±9.3 %; P=.04).ConclusionCorrelations were moderate to good for the assessment of ESV, EDV and LVEF between gated ¹³N-NH₃ and ¹⁸F-FDG. LVEF was underestimated with gated ¹³N-NH₃ in rats with myocardial infarction. In healthy rats, LV volumes and LVEF can be measured reproducibly with either approach.     

Single breath-hold magnetic resonance cine imaging for fast assessment of global and regional left ventricular function in clinical routine

Objective:

To evaluate a TGRAPPA (temporal parallel acquisition technique)-accelerated, single breath-hold multi-slice cine imaging approach for the assessment of left ventricular (LV) function.

Methods:

One hundred eleven patients were examined at 1.5 T. Cine imaging was performed with single-slice breath-hold acquisitions in short-axis orientation using a SSFP (TR 2.63 ms, TE 1.12 ms, FA 72°) sequence and a TGRAPPA SSFP (TR 2.66 ms, TE 1.11 ms, FA 72°, AF 3) sequence, which covered the entire LV in multiple short-axis slices during a single breath-hold. End-diastolic (EDV), end-systolic (ESV), stroke volumes (SV), ejection fraction (EF), muscle mass (MM) and regional wall motion were assessed for both data sets.

Results:

Single breath-hold imaging was feasible in 108 patients. Excellent correlations were observed for all volumetric parameters derived from both data sets (all r?>?0.97). While EDV and ESV showed marginally lower values for single breath-hold imaging (EDV: ?1.6?±?7.9 ml; ESV: ?1.8?±?6.0 ml, p?<?0.05), no differences were observed for SV, EF, MM and regional wall motion assessment. Single breath-hold imaging required significant shorter acquisition times (28?±?6 s vs. 335?±?87 s).

Conclusion:

TGRAPPA-accelerated multi-slice SSPF imaging allows for fast and accurate assessment of regional and global LV function within a single breath-hold.     

Improved quantification of small hearts for gated myocardial perfusion imaging

Purpose

In 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.

Methods

The 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.

Results

The 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).

Conclusion

The 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.     

Normal biventricular function,volumes, and mass in children aged 8 to 17 years

Purpose

To assess normal values for biventricular function, volumes, and mass with current cardiovascular magnetic resonance (CMR) imaging sequences in children.

Materials and Methods

Included in the study were 60 healthy children aged 8–17 years. A short axis set of contiguous slices was acquired with CMR imaging employing steady‐state free precession. Biventricular end‐diastolic volume (EDV), end‐systolic volume (ESV), ejection fraction (EF), and mass were determined. Uni‐ and multivariate linear regression analyses were performed to study the interrelation of age, gender, and body surface area (BSA) on biventricular volumes and mass. The coefficient of variation was calculated for intra‐ and interobserver variability.

Results

EF did not differ between boys and girls (mean LV‐EF 69 ± (SD) 5%, mean RV‐EF 65 ± 5%). BSA had good (EDV, mass) and modest (ESV) correlation with biventricular measurements. Gender appeared a significant modifier of these relations, whereas age had no independent contribution. The intra‐ and interobserver coefficient of variation was in the range 2.1%–13.9% for biventricular EDV, ESV, and mass.

Conclusion

This study reveals gender‐specific normative data for biventricular function, volumes, and mass in children age 8–17 years that can be used as reference data in the follow‐up of pediatric cardiac patients. J. Magn. Reson. Imaging 2009;29:552–559. © 2009 Wiley‐Liss, Inc.     

Electrocardiographically gated 11C-hydroxyephedrine PET for the simultaneous assessment of cardiac sympathetic and contractile functions

Objective

Application of the electrocardiographically (ECG) gated positron emission tomography (PET) technique with ¹¹C-hydroxyephedrine (HED) would allow the simultaneous assessment of cardiac sympathetic and contractile functions. However, there are uncertainties regarding the diagnostic accuracy of left ventricular (LV) volume measurements using ECG-gated HED-PET. The purpose of this study was to clarify the minimal requirement of count statistics to measure LV volumes with ECG-gated HED-PET and to investigate the reliability of the measurements.

Methods

Five healthy volunteers and 11 patients with heart failure underwent a 40-min list-mode PET scan after an injection of HED (197 ± 35 MBq). The list-mode data were histogrammed into multiple sets of acquisition periods at 0.5, 1.0, 2.0, 4.0, 6.0, 8.0, 12.0 Mcount/bin and reconstructed into corresponding gated images using an iterative algorithm. The LV end-diastolic volume (LVEDV), the LV end-systolic volume (LVESV), and the LV ejection fraction (LVEF) were calculated in each acquisition period. These values were compared with those obtained by cardiac magnetic resonance imaging (MRI). Possible effects of HED retention on the accuracy of the volume measurements were investigated.

Results

Collecting less than 4.0 Mcount/bin resulted in noisy cardiac images. The lower counts resulted in underestimation in the volume measurements. Reasonably accurate volume measurements required equal to or greater than 6.0 Mcount/bin. This corresponded to 7.0 ± 1.9 min (range, 4.0–10.3 min) for the acquisition period. Volumetric results using the 6.0 Mcount/bin data highly correlated with cardiac MRI (LVEDV: r = 0.85, p < 0.0001; LVESV: r = 0.89, p < 0.0001; LVEF: r = 0.77, p < 0.01). The HED retention did not affect the volumetric results compared to the MRI volumetry.

Conclusions

The volumetric accuracy with ECG-gated HED-PET was affected by the count statistics rather than the HED retention. LV volume measurements were feasible with 10-min acquisition period for most of the patients. This technique allows the simultaneous assessment of cardiac sympathetic and contractile functions without the need for an additional injection or scanning time, thus reducing overall costs for diagnostic imaging.     

Quantitative assessment of right ventricular function and pulmonary regurgitation in surgically repaired tetralogy of Fallot using 256-slice CT: comparison with 3-Tesla MRI

Objectives

To compare 256-slice cardiac computed tomography (CCT) with cardiac magnetic resonance (CMR) imaging to assess right ventricular (RV) function and pulmonary regurgitant fraction (PRF) in patients with repaired tetralogy of Fallot (TOF).

Methods

Thirty-three consecutive patients with repaired TOF underwent retrospective ECG-gated CCT and 3-Tesla CMR. RV and left ventricular (LV) end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV) and ejection fraction (EF) were measured using CCT and CMR. PRF-CCT (%) was defined as (RVSV???LVSV)/RVSV. PRF-CMR (%) was measured by the phase-contrast method. Repeated measurements were performed to determine intra- and interobserver variability.

Results

CCT measurements, including PRF, correlated highly with the CMR reference (r?=?0.71–0.96). CCT overestimated RVEDV (mean difference, 17.1?±?2.9 ml), RVESV (12.9?±?2.1 ml) and RVSV (4.2?±?2.0 ml), and underestimated RVEF (?2.6?±?1.0 %) and PRF (?9.1?±?2.0 %) compared with CMR. The limits of agreement between CCT and CMR were in a good range for all measurements. The variability in CCT measurements was lower than those in CMR. The estimated effective radiation dose was 7.6?±?2.6 mSv.

Conclusions

256-slice CCT can assess RV function and PRF with relatively low dose radiation exposure in patients with repaired TOF, but overestimates RV volume and underestimates PRF.

Key points

? 256-slice CT assessment of RV function is highly reproducible in repaired TOF. ? Pulmonary regurgitation can be evaluated by biventricular systolic volume difference. ? CT overestimates RV volume and underestimates pulmonary regurgitation, compared with MRI.     

Abnormalities of myocardial perfusion and glucose metabolism in patients with isolated left ventricular non-compaction

Background

The prevalence of myocardial perfusion and glucose metabolic abnormalities and their significance in patients with isolated left ventricular non-compaction (ILVNC) have not been well investigated.

Methods

Seventeen ILVNC patients who underwent cardiac magnetic resonance (CMR) and ^99mTc-sestamibi SPECT/fluorine-18 deoxyglucose (¹⁸F-FDG) PET imaging were included. Left ventricular non-compaction, regional wall motion abnormalities, left ventricular ejection fraction (LVEF), and delayed enhancement (DE) were estimated using CMR. Myocardial perfusion and metabolism were evaluated with SPECT/PET.

Results

Ninety-five (32.9%) segments were considered non-compacted. DE was present in 52 (18.0%) segments and 10 (58.8%) patients. The rate of occurrence of DE was significantly higher in compacted segments than in non-compacted segments (22.7% vs 8.4%, P = .003). Myocardial perfusion abnormalities were present in 92 (31.8%) segments, of which 66 were perfusion/metabolism match and 26 were perfusion/metabolism mismatch. The rate of occurrence of perfusion abnormality was similar between compacted and non-compacted segments (32.0% vs 31.6%, P = .948), but it was significantly higher in segments with DE than in those without DE (51.9% vs 27.4%, P = .001). None of the imaging features alone (non-compaction, DE, perfusion abnormalities, match or mismatch) showed significant correlations with LVEF (all P > .05).

Conclusion

In the current study, myocardial perfusion/metabolism mismatch and match were observed in both non-compacted and compacted myocardium in ILVNC patients. Further research is warranted to determine their pathologic and clinical significance.     

Left ventricular function in response to dipyridamole stress: head-to-head comparison between <Superscript>82</Superscript>Rubidium PET and <Superscript>99m</Superscript>Tc-sestamibi SPECT ECG-gated myocardial perfusion imaging

Purpose

Myocardial perfusion imaging (MPI) with ^99mTc-sestamibi (sestamibi) SPECT and rubidium-82 (⁸²Rb) PET both allow for combined assessment of perfusion and left ventricular (LV) function. We sought to compare parameters of LV function obtained with both methods using a single dipyridamole stress dose.

Materials and methods

A group of 221 consecutive patients (65.2?±?10.4 years, 52.9% male) underwent consecutive sestamibi and ⁸²Rb MPI after a single dipyridamole stress dose. Sestamibi and ⁸²Rb summed rest (SRS), stress (SSS) and difference (SDS) scores, and LV end-diastolic (EDV) and end-systolic (ESV) volumes and left ventricular ejection fraction (LVEF) were compared.

Results

Bland-Altman analysis showed that with increasing ESV and EDV the difference between the two perfusion tracers increased both at rest and post-stress. The mean difference in EDV and ESV between the two perfusion tracers at rest could both be independently explained by the ⁸²Rb SDS and the sestamibi SRS. The combined models explained approximately 30% of the variation in these volumes between the two perfusion tracers (R²?=?0.261, p?=?0.005; R²?=?0.296, p?<?0.001, for EDV and ESV respectively). However, the mean difference in LVEF between sestamibi and ⁸²Rb showed no significant trend post-stress (R²?=?0.001, p?=?0.70) and only a modest linear increase with increasing LVEF values at rest (R²?=?0.032, p?=?0.009).

Conclusions

Differences in left ventricular volumes between sestamibi and ⁸²Rb MPI increase with increasing volumes. However, these differences did only marginally affect LVEF between sestamibi and ⁸²Rb. In clinical practice these results should be taken into account when comparing functional derived parameters between sestamibi and ⁸²Rb MPI.