Prognostic value of normal stress myocardial perfusion imaging and ventricular function in Japanese patients with chronic kidney disease: a study based on the J-ACCESS-3 database.

BACKGROUND: The purpose of this study is to test the hypothesis that a normal myocardial perfusion imaging (MPI) study in chronic kidney disease (CKD) can provide benign prognostic information for the prediction of major cardiovascular events. METHODS: The study group consisted of 431 CKD patients (males, 64%; mean age, 72 ± 11 years) with normal SPECT imaging. Based on SPECT image and QGS data, 331 had a summed stress score of 3 or less, a summed difference score of 1 or less and normal cardiac function (males; end-systolic volume (ESV) ≤ 60 ml, females; ESV ≤ 40 ml, males, ejection fraction (EF) ≥ 49%; females, EF ≥ 50%). RESULTS: During a 3-year follow-up period, there were a total of 27 major cardiovascular events, including cardiac death (n = 3), sudden death (n = 3), and acute coronary syndrome (n = 3), and 19 were hospitalized because of congestive heart failure. Kaplan-Meier analysis showed that the number of major cardiovascular events in patients with higher eGFR of ≥ 15 ml/min) were very few, and regarded as low risk. According to the eGFR status, namely < 15 (n = 58), 15 to < 30 (n = 97), 30 to < 45 (n = 131), ≥ 45 (n = 45), the higher cardiac event rate was observed in patients with eGFR of < 15 ml/min among the four groups. The major cardiovascular event rate in patients with the lowest eGFR (< 15) was twice as much than that in patients with eGFR of ≥ 30 ml/min. Lower hemoglobin (males, < 12 g/dl; females, < 11 g/dl) and higher CRP (CPR ≥ 0.3 mg/dl) were also the predictors of increased risk. CONCLUSIONS: Normal stress SPECT images confer a benign prognosis in patients with CKD, but care must be taken for severely reduced renal function, which was associated with higher cardiac event.

Creation and characterization of normal myocardial perfusion imaging databases using the IQ·SPECT system.

BACKGROUND: Image acquisition by short-time single-photon emission-computed tomography (SPECT) has been made feasible by IQ·SPECT. The aim of this study was to generate normal databases (NDBs) of thallium-201 (201Tl) myocardial perfusion imaging for IQ·SPECT, and characterize myocardial perfusion distribution. METHODS AND RESULTS: We retrospectively enrolled 159 patients with a low likelihood of cardiac diseases from four hospitals in Japan. All patients underwent short-time 201Tl myocardial perfusion IQ·SPECT with or without attenuation and scatter correction (ACSC) in either supine or prone position. The mean myocardial counts were calculated using 17-segment polar maps. Three NDBs were derived from supine and prone images as well as supine images with ACSC. Differences between the supine and prone positions were observed in the uncorrected sex-segregated NDBs in the mid-inferolateral counts (p ≤ 0.016 for males and p ≤ 0.002 for females). Differences between IQ·SPECT and conventional SPECT were also observed in the mid-anterior, inferolateral, and apical lateral counts (p ≤ 0.009 for males and p ≤ 0.003 for females). Apical low counts attributed to myocardial thinning were observed in the apical anterior and apex segments in the supine IQ·SPECT NDB with ACSC. CONCLUSIONS: There were significant differences between uncorrected supine and prone NDBs, between uncorrected supine NDB and supine NDB with ACSC, and between uncorrected supine NDB and conventional SPECT NDB. Understanding the pattern of normal distribution in IQ-SPECT short-time acquisitions with and without ACSC will be helpful for interpretation of imaging findings in patients with coronary artery disease (CAD) or low likelihood of CAD and the NDBs will aid in quantitative analysis.

Diagnostic accuracy of an artificial neural network compared with statistical quantitation of myocardial perfusion images: a Japanese multicenter study.

PURPOSE: Artificial neural networks (ANN) might help to diagnose coronary artery disease. This study aimed to determine whether the diagnostic accuracy of an ANN-based diagnostic system and conventional quantitation are comparable. METHODS: The ANN was trained to classify potentially abnormal areas as true or false based on the nuclear cardiology expert interpretation of 1001 gated stress/rest 99mTc-MIBI images at 12 hospitals. The diagnostic accuracy of the ANN was compared with 364 expert interpretations that served as the gold standard of abnormality for the validation study. Conventional summed stress/rest/difference scores (SSS/SRS/SDS) were calculated and compared with receiver operating characteristics (ROC) analysis. RESULTS: The ANN generated a better area under the ROC curves (AUC) than SSS (0.92 vs. 0.82, p < 0.0001), indicating better identification of stress defects. The ANN also generated a better AUC than SDS (0.90 vs. 0.75, p < 0.0001) for stress-induced ischemia. The AUC for patients with old myocardial infarction based on rest defects was 0.97 (0.91 for SRS, p = 0.0061), and that for patients with and without a history of revascularization based on stress defects was 0.94 and 0.90 (p = 0.0055 and p < 0.0001 vs. SSS, respectively). The SSS/SRS/SDS steeply increased when ANN values (probability of abnormality) were >0.80. CONCLUSION: The ANN was diagnostically accurate in various clinical settings, including that of patients with previous myocardial infarction and coronary revascularization. The ANN could help to diagnose coronary artery disease.

Comparison of phase dyssynchrony analysis using gated myocardial perfusion imaging with four software programs: Based on the Japanese Society of Nuclear Medicine working group normal database.

PURPOSE: Left ventricular (LV) phase dyssynchrony parameters based on gated myocardial perfusion imaging varied among software programs. The aim of this study was to determine normal ranges and factors affecting phase parameters. METHODS: Normal databases were derived from the Japanese Society of Nuclear Medicine working group (n = 69). The programs were Emory Cardiac Toolbox with SyncTool (ECTb), Quantitative Gated SPECT (QGS), Heart Function View (HFV), and cardioREPO (cREPO); parameters of phase standard deviation (PSD), 95% bandwidth, and entropy were compared with parameters with ECTb as a reference. RESULTS: PSD (degree) was 5.3 ± 3.3 for QGS (P < .0001), 5.4 ± 2.5 for HFV (P < .0001), and 10.3 ± 3.2 for cREPO (P = n. s.) compared with 11.5 ± 5.5 for ECTb. Phase bandwidth with three programs differed significantly from ECTb. Gender differences were significant for all programs, indicating larger variation in males. After adjustment of LV volumes between genders, the difference disappeared except for QGS. The phase parameters showed wider variations in patients with the lower ejection fraction (EF) and larger LV volumes, depending on software types. CONCLUSION: Based on normal ranges of phase dyssynchrony parameters in four software programs, dependency on genders, LV volume, and EF should be considered, indicating the need for careful comparison among different software programs.

Reducing the small-heart effect in pediatric gated myocardial perfusion single-photon emission computed tomography.

BACKGROUND: We compared two reconstruction algorisms and two cardiac functional evaluation software programs in terms of their accuracy for estimating ejection fraction (EF) of small hearts (SH). METHODS: The study group consisted of 66 pediatric patients. Data were reconstructed using a filtered back projection (FBP) method without the resolution correction (RC) and an iterative method based on an ordered subset expectation maximization (OSEM) algorithm with the RC. EF was evaluated using two software programs of quantitative gated single-photon emission computed tomography (SPECT) (QGS) and cardioREPO. We compared the EF of gated myocardial perfusion SPECT to echocardiographic measurement (Echo). RESULTS: Forty-eight of 66 patients had an end-systolic volume < 20 mL which was used as the criterion for being included in the SH group, and the SH effect led to an overestimation of EF. While significant differences were observed between Echo (66.9 ± 5.0%) and QGS-FBP without RC (76.9 ± 8.4%, P < .0001), QGS-OSEM with RC (76.6 ± 8.6%, P < .0001), and cardioREPO-FBP without RC (72.1 ± 10.0%, P = .0011), no significant difference was observed between Echo and cardioREPO-OSEM with RC (67.4 ± 6.1%) in SH group. CONCLUSIONS: In pediatric gated myocardial perfusion SPECT, the SH effect can be significantly reduced when an OSEM algorithm is used with RC in combination with the specific cardioREPO algorithm.

Significant correlation between renal 123I-metaiodobenzylguanidine scintigraphy and muscle sympathetic nerve activity in patients with primary hypertension.

BACKGROUND: Iodine-123 metaiodobenzylguanidine (123I-MIBG) scintigraphy is used as a noninvasive imaging method for assessing cardiac sympathetic nerve activity. We tested the hypothesis that renal 123I-MIBG imaging is correlated with muscle sympathetic nerve activity (MSNA) in patients with primary hypertension. METHODS: Thirty-one consecutive patients with primary hypertension were included. Multiunit MSNA was recorded from the peroneal nerve to evaluate direct efferent sympathetic nerve activity. Planar renal and cardiac 123I-MIBG images were acquired. Early and delayed kidney-to-mediastinum ratio (K/M), early and delayed heart-to-mediastinum ratio (H/M), and washout rates (WR) were calculated. RESULTS: In 27 of 31 patients, blood pressure was controlled on antihypertensive medication. Mean systolic and diastolic blood pressures were 118 ± 18 and 67 ± 15 mmHg, respectively. Although early and late K/M and H/M were not significantly correlated with MSNA, both cardiac and average renal WR were significantly correlated with MSNA (r = 0.45, P = .0035 and r = 0.68, P < .001, respectively). Right and left renal WR were similarly correlated with MSNA. Renal WR was significantly higher than cardiac WR (43.2% vs 25.8%, P < .001) in these patients with hypertension. CONCLUSIONS: Renal 123I-MIBG WR was significantly associated with multiunit MSNA. Renal 123I-MIBG imaging offers a noninvasive clinical methodology for assessing renal sympathetic nerve function.

Development and validation of a direct-comparison method for cardiac (123)I-metaiodobenzylguanidine washout rates derived from late 3-hour and 4-hour imaging.

PURPOSE: The washout rate (WR) has been used in (123)I-metaiodobenzylguanidine (MIBG) imaging to evaluate cardiac sympathetic innervation. However, WR varies depending on the time between the early and late MIBG scans. Late scans are performed at either 3 or 4 hours after injection of MIBG. The aim of this study was to directly compare the WR at 3 hours (WR3h) with the WR at 4 hours (WR4h). METHODS: We hypothesized that the cardiac count would reduce linearly between the 3-hour and 4-hour scans. A linear regression model for cardiac counts at two time-points was generated. We enrolled a total of 96 patients who underwent planar (123)I-MIBG scintigraphy early (15 min) and during the late phase at both 3 and 4 hours. Patients were randomly divided into two groups: a model-creation group (group 1) and a clinical validation group (group 2). Cardiac counts at 15 minutes (countearly), 3 hours (count3h) and 4 hours (count4h) were measured. Cardiac count4h was mathematically estimated using the linear regression model from countearly and count3h. RESULTS: In group 1, the actual cardiac count4h/countearly was highly significantly correlated with count3h/countearly (r = 0.979). In group 2, the average estimated count4h was 92.8 ± 31.9, and there was no significant difference between this value and the actual count4h (91.9 ± 31.9). Bland-Altman analysis revealed a small bias of -0.9 with 95 % limits of agreement of -6.2 and +4.3. WR4h calculated using the estimated cardiac count4h was comparable to the actual WR4h (24.3 ± 9.6 % vs. 25.1 ± 9.7 %, p = ns). Bland-Altman analysis and the intraclass correlation coefficient showed that there was excellent agreement between the estimated and actual WR4h. CONCLUSION: The linear regression model that we used accurately estimated cardiac count4h using countearly and count3h. Moreover, WR4h that was mathematically calculated using the estimated count4h was comparable to the actual WR4h.

Prognostic Value of Cardiac Sympathetic Nerve Imaging Using Long-Term Follow-up Data - Ischemic vs. Non-Ischemic Heart Failure Etiology.

BACKGROUND: Although there are several known prognostic determinants in heart failure (HF), individual risk profiles can vary, in particular between ischemic and non-ischemic HF background. This study investigated the difference in prognostic efficacy of cardiac (123)I-meta-iodobenzylguanidine (MIBG) imaging between the 2 etiologies. METHODS AND RESULTS: All 1,322 patients with HF were enrolled and followed up at most after 10 years. The HF patients were divided into 2 groups: an ischemic group (n=362) and non-ischemic group (n=960), and Cox proportional hazards model was used for data analysis. During 10 years of follow-up, 296 (22.4%) of 1,322 patients died; the mortality rates were 21.8% and 22.6% for the ischemic and non-ischemic groups, respectively. The ischemic group had greater prevalence of sudden death and lethal acute myocardial infarction, and the non-ischemic group had a higher rate of pump failure death. On multivariate Cox proportional hazards analysis using categorized variables, in the ischemic group, delayed heart-to-mediastinum ratio (HMR; P<0.0001), age (P=0.0002) and LVEF (P=0.03) were the independent significant predictors of lethal events. In the non-ischemic group, delayed HMR (P<0.0001), NYHA class (P<0.0001) and age (P<0.0001) were significant determinants of lethal outcome. CONCLUSIONS: Cardiac MIBG imaging has nearly identical prognostic value in both ischemic and non-ischemic HF, independent of cause of cardiac death.

Diagnostic Performance of Artificial Neural Network for Detecting Ischemia in Myocardial Perfusion Imaging.

BACKGROUND: The purpose of this study was to apply an artificial neural network (ANN) in patients with coronary artery disease (CAD) and to characterize its diagnostic ability compared with conventional visual and quantitative methods in myocardial perfusion imaging (MPI). METHODS AND RESULTS: A total of 106 patients with CAD were studied with MPI, including multiple vessel disease (49%), history of myocardial infarction (27%) and coronary intervention (30%). The ANN detected abnormal areas with a probability of stress defect and ischemia. The consensus diagnosis based on expert interpretation and coronary stenosis was used as the gold standard. The left ventricular ANN value was higher in the stress-defect group than in the no-defect group (0.92±0.11 vs. 0.25±0.32, P<0.0001) and higher in the ischemia group than in the no-ischemia group (0.70±0.40 vs. 0.004±0.032, P<0.0001). Receiver-operating characteristics curve analysis showed comparable diagnostic accuracy between ANN and the scoring methods (0.971 vs. 0.980 for stress defect, and 0.882 vs. 0.937 for ischemia, both P=NS). The relationship between the ANN and defect scores was non-linear, with the ANN rapidly increased in ranges of summed stress score of 2-7 and summed defect score of 2-4. CONCLUSIONS: Although the diagnostic ability of ANN was similar to that of conventional scoring methods, the ANN could provide a different viewpoint for judging abnormality, and thus is a promising method for evaluating abnormality in MPI.

[The Optimal Reconstruction Parameters by Scatter and Attenuation Corrections Using Multi-focus Collimator System in Thallium-201 Myocardial Perfusion SPECT Study].

The aim of this study was to reveal the optimal reconstruction parameters of ordered subset conjugates gradient minimizer (OSCGM) by no correction (NC), attenuation correction (AC), and AC+scatter correction (ACSC) using IQ-single photon emission computed tomography (SPECT) system in thallium-201 myocardial perfusion SPECT. Myocardial phantom acquired two patterns, with or without defect. Myocardial images were performed 5-point scale visual score and quantitative evaluations using contrast, uptake, and uniformity about the subset and update (subset×iteration) of OSCGM and the full width at half maximum (FWHM) of Gaussian filter by three corrections. We decided on optimal reconstruction parameters of OSCGM by three corrections. The number of subsets to create suitable images were 3 or 5 for NC and AC, 2 or 3 for ACSC. The updates to create suitable images were 30 or 40 for NC, 40 or 60 for AC, and 30 for ACSC. Furthermore, the FWHM of Gaussian filters were 9.6 mm or 12 mm for NC and ACSC, 7.2 mm or 9.6 mm for AC. In conclusion, the following optimal reconstruction parameters of OSCGM were decided; NC: subset 5, iteration 8 and FWHM 9.6 mm, AC: subset 5, iteration 8 and FWHM 7.2 mm, ACSC: subset 3, iteration 10 and FWHM 9.6 mm.

A prediction model for 5-year cardiac mortality in patients with chronic heart failure using ¹²³I-metaiodobenzylguanidine imaging.

PURPOSE: Prediction of mortality risk is important in the management of chronic heart failure (CHF). The aim of this study was to create a prediction model for 5-year cardiac death including assessment of cardiac sympathetic innervation using data from a multicenter cohort study in Japan. METHODS: The original pooled database consisted of cohort studies from six sites in Japan. A total of 933 CHF patients who underwent (123)I-metaiodobenzylguanidine (MIBG) imaging and whose 5-year outcomes were known were selected from this database. The late MIBG heart-to-mediastinum ratio (HMR) was used for quantification of cardiac uptake. Cox proportional hazard and logistic regression analyses were used to select appropriate variables for predicting 5-year cardiac mortality. The formula for predicting 5-year mortality was created using a logistic regression model. RESULTS: During the 5-year follow-up, 205 patients (22 %) died of a cardiac event including heart failure death, sudden cardiac death and fatal acute myocardial infarction (64 %, 30 % and 6 %, respectively). Multivariate logistic analysis selected four parameters, including New York Heart Association (NYHA) functional class, age, gender and left ventricular ejection fraction, without HMR (model 1) and five parameters with the addition of HMR (model 2). The net reclassification improvement analysis for all subjects was 13.8 % (p < 0.0001) by including HMR and its inclusion was most effective in the downward reclassification of low-risk patients. Nomograms for predicting 5-year cardiac mortality were created from the five-parameter regression model. CONCLUSION: Cardiac MIBG imaging had a significant additive value for predicting cardiac mortality. The prediction formula and nomograms can be used for risk stratifying in patients with CHF.

Multicenter cross-calibration of I-123 metaiodobenzylguanidine heart-to-mediastinum ratios to overcome camera-collimator variations.

BACKGROUND: The heart-to-mediastinum ratio (HMR) of (123)I-metaiodobenzylguanidine (MIBG) showed variations among institutions and needs to be standardized among various scinticamera-collimator combinations. METHODS: A total of 225 phantom experiments were performed in 84 institutions to calculate cross-calibration coefficients of HMR. Based on phantom studies, a conversion coefficient for each camera-collimator system was created, including low-energy (LE, n = 125) and a medium-energy (ME, n = 100) collimators. An average conversion coefficient from the most common ME group was used to calculate the standard HMR. In clinical MIBG studies (n = 52) from three institutions, HMRs were standardized from both LE- and ME-type collimators and classified into risk groups of <1.60, 1.60-2.19, and ≥2.20. RESULTS: The average conversion coefficients from the individual camera-collimator condition to the mathematically calculated reference HMR ranged from 0.55 to 0.75 for LE groups and from 0.83 to 0.95 for ME groups. The conversion coefficient of 0.88 was used to unify HMRs from all acquisition conditions. Using the standardized HMR, clinical studies (n = 52) showed good agreement between LE and ME types regarding three risk groups (κ = 0.83, P < .0001, complete agreement in 90%, 42% of the patients reclassified into the same risk group). CONCLUSION: By using the reference HMR and conversion coefficients for the system, HMRs with various conditions can be converted to the standard HMRs in a range of normal to low HMRs.

Area of ischemia assessed by physicians and software packages from myocardial perfusion scintigrams.

BACKGROUND: The European Society of Cardiology recommends that patients with >10% area of ischemia should receive revascularization. We investigated inter-observer variability for the extent of ischemic defects reported by different physicians and by different software tools, and if inter-observer variability was reduced when the physicians were provided with a computerized suggestion of the defects. METHODS: Twenty-five myocardial perfusion single photon emission computed tomography (SPECT) patients who were regarded as ischemic according to the final report were included. Eleven physicians in nuclear medicine delineated the extent of the ischemic defects. After at least two weeks, they delineated the defects again, and were this time provided a suggestion of the defect delineation by EXINI HeartTM (EXINI). Summed difference scores and ischemic extent values were obtained from four software programs. RESULTS: The median extent values obtained from the 11 physicians varied between 8% and 34%, and between 9% and 16% for the software programs. For all 25 patients, mean extent obtained from EXINI was 17.0% (± standard deviation (SD) 14.6%). Mean extent for physicians was 22.6% (± 15.6%) for the first delineation and 19.1% (± 14.9%) for the evaluation where they were provided computerized suggestion. Intra-class correlation (ICC) increased from 0.56 (95% confidence interval (CI) 0.41-0.72) to 0.81 (95% CI 0.71-0.90) between the first and the second delineation, and SD between physicians were 7.8 (first) and 5.9 (second delineation). CONCLUSIONS: There was large variability in the estimated ischemic defect size obtained both from different physicians and from different software packages. When the physicians were provided with a suggested delineation, the inter-observer variability decreased significantly.

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.

Metabolic syndrome is not a predictor for cardiovascular events in Japanese patients with diabetes mellitus asymptomatic for coronary artery disease: a retrospective analysis of the J-ACCESS-2 study.

PURPOSE: Patients with metabolic syndrome (MetS) have potentially higher risk for cardiovascular events. The aim of this study was to evaluate the effect of MetS on cardiac events in type-2 diabetic patients asymptomatic for coronary artery disease (CAD) in a Japanese population. METHODS: A total of 485 patients from a J-ACCESS-2 investigation with stress-gated myocardial perfusion imaging (MPI) and quantitative-gated MPI analysis were examined. Cardiovascular hard events (cardiac death and acute coronary syndrome) and total events during a 3-year follow-up were analyzed. RESULTS: The MetS group (n = 229) had higher incidence of hypertension, dyslipidemia, and ventricular dilatation than the non-MetS group (n = 256). The hard events were 8 and 12 for the MetS and non-MetS groups (P = n.s.), and total events were 31 and 31 for each of these groups, respectively (P = n.s.). Significant variables related to total cardiovascular events included age, current smoking, insulin use, total cholesterol, ejection fraction, summed stress score ≥ 9, and summed difference score ≥ 2. Cox proportional hazard analysis and Kaplan-Meier survival analysis showed that only the summed stress score was related to total events (P = .01), and the presence and the number of items for MetS criteria were not. CONCLUSION: In patients with type 2 diabetes asymptomatic for CAD, cardiovascular events and ischemia are as common in diabetic patients without MetS as in those with MetS. A high MPI defect score is related to total events including cardiac and cerebrovascular events.

Standardization of metaiodobenzylguanidine heart to mediastinum ratio using a calibration phantom: effects of correction on normal databases and a multicentre study.

PURPOSE: This study was performed to demonstrate that the results obtained with a calibration phantom could be used as a tool for standardizing measurement of heart to mediastinum (H/M) ratio in cardiac metaiodobenzylguanidine (MIBG) imaging. METHODS: Images of the phantom containing (123)I-MIBG were acquired on the cameras in 10 hospitals (11 camera types) to determine the relationship between H/M ratios using different collimators: low-energy (LE) and medium-energy (ME)/low-medium-energy (LME) collimators. The effect of standardization on the ME-comparable H/M ratio was examined in two settings: a Japanese standard MIBG database (n = 62) and multicentre studies (n = 49). In a multicentre study, probable Alzheimer's disease (AD, n = 18) and probable dementia with Lewy bodies (DLB, n = 31) were studied and standardized by the calibration phantom method. RESULTS: Linear regression equations between LE and ME collimators were obtained for the phantom study in all institutions. When the H/M ratio with an LE collimator was corrected based upon the calibration phantom, the corrected values were comparable to those obtained using ME collimators. The standard database also exhibited a normal distribution after standardization as determined by skewness and goodness-of-fit test. A mixture of the populations by LE and ME collimators showed significant separation of AD and DLB groups (F ratio = 24.9 for the late H/M), but the corrected values resulted in higher F ratios for both early and late H/M (F ratio = 34.9 for the late H/M). CONCLUSION: Standardization of H/M ratios by the heart-chest calibration phantom method is feasible among different collimator types. This method could be practically used for multicentre comparison of H/M ratios.

Cardiac event risk in Japanese subjects estimated using gated myocardial perfusion imaging, in conjunction with diabetes mellitus and chronic kidney disease.

BACKGROUND: Cardiac event risk is estimated using quantitative gated myocardial perfusion imaging (MPI) and clinical background in patients with ischemic heart disease. The aim of the present study was to calculate major cardiac event risk and tabulate it in the Heart Risk Table for clinical use of risk stratification. METHODS AND RESULTS: Multivariate logistic regression was performed based on a multicenter prognostic database (Japanese Assessment of Cardiac Events and Survival Study by Quantitative Gated Single-photon emission computed tomography [J-ACCESS investigation]) using MPI (n=2,395). The risk of major cardiac events (cardiac death, non-fatal myocardial infarction and heart failure requiring hospitalization) was estimated using age, ejection fraction (EF), estimated glomerular filtration rate (eGFR) and presence of diabetes mellitus (DM). Age-matched standard eGFR was determined in 77 subjects. Major cardiac event risk was calculated using the equation: risk (%/3 years)=1/(1+Exp(-(-4.699-0.0151×eGFR+0.7998×DM+0.0582×age+0.697×SSS-0.0359×EF))×100, where SSS refers to summed stress scores. Risk was determined without eGFR (the initial version) and using the present formula with eGFR (revised version), with consistent results. DM and chronic kidney disease were major determinants of cardiac events. CONCLUSIONS: Cardiac event risk was estimated using MPI defect score and left ventricular EF in conjunction with eGFR and the presence of DM. The risk table might be used for risk evaluation in Japanese patients undergoing MPI.

Semi-automated algorithm for calculating heart-to-mediastinum ratio in cardiac Iodine-123 MIBG imaging.

BACKGROUND: We have developed novel software for semi-automatically measuring heart-to-mediastinum (H/M) ratio in cardiac Iodine-123 (¹²³I)-labeled meta-iodobenzylguanidine (MIBG) imaging. Our aim is to improve the reproducibility of the H/M ratio using the semi-automated method as opposed to the manual method. METHODS AND RESULTS: The software algorithm automatically determined the mediastinal region of interest (ROI) using information from ¹²³I-MIBG uptake of the heart, lung, liver, and thyroid after a cardiac circular ROI was manually set. A total of 37 patients who underwent both early and delayed ¹²³I-MIBG imaging was retrospectively selected. The heart-to-mediastinum (H/M) ratios were calculated by both semi-automated and manual methods and assessed for the intra- and inter-observer variability. All H/M ratios were classified into three groups: normal, slight abnormality, and severe abnormality. The H/M ratios with the new method were higher than those obtained manually (P < .001). In the test-retest reliability, the intra-class correlation coefficient from the semi-automated method showed excellent reproducibility for early (0.99) and delayed (0.99) imaging. The Bland-Altman plots demonstrated better agreement using the semi-automated method (a range of 95% limits -0.11 to 0.10) than that in the manual method (-0.34 to 0.27). The inter-observer agreement was also good using the semi-automated method (κ = 0.866). CONCLUSIONS: The H/M ratio using the semi-automated method showed high reproducibility in both early and delayed imaging.