Edge AI Model Deployed for Real-Time Detection of Atrial Fibrillation Risk during Sinus Rhythm.

Objectives: The study aimed to develop a deep learning-based edge AI model deployed on electrocardiograph (ECG) devices for the real-time detection of atrial fibrillation (AF) risk during sinus rhythm (SR) using standard 10 s, 12-lead electrocardiograms (ECGs). Methods: A novel approach was used to convert standard 12-lead ECGs into binary images for model input, and a lightweight convolutional neural network (CNN)-based model was trained using data collected by the Japan Agency for Medical and Research Development (AMED) between 2019 and 2022. Patients over 40 years old with digital, SR ECGs were retrospectively enrolled and divided into AF and non-AF groups. The data labeling was supervised by cardiologists. The dataset was randomly allocated into training, validation, and internal testing datasets. External testing was conducted on data collected from other hospitals. Results: The best-trained model achieved an AUC of 0.82 and 0.80, sensitivity of 79.5% and 72.3%, specificity of 77.8% and 77.7%, precision of 78.2% and 76.4%, and overall accuracy of 78.6% and 75.0% in the internal and external testing datasets, respectively. The deployed model and app package utilized 2.5 MB and 40 MB of the available ROM and RAM capacity on the edge ECG device, correspondingly. The processing time for AF risk detection was approximately 2 s. Conclusions: The model maintains comparable performance and improves its suitability for deployment on resource-constrained ECG devices, thereby expanding its potential impact to a wide range of healthcare settings. Its successful deployment enables real-time AF risk detection during SR, allowing for timely intervention to prevent AF-related serious consequences like stroke and premature death.

Phantom-Based Standardization Method for 123I-metaiodobenzylguanidine Heart-to-Mediastinum Ratio Validated by D-SPECT Versus Anger Camera.

Background: The 123I-metaiodobenzylguanidine heart-to-mediastinum ratios (HMRs) have been standardized between D-SPECT and Anger cameras in a small patient cohort using a phantom-based conversion method. This study aimed to determine the validity of this method and compare the diagnostic performance of the two cameras in a larger patient cohort. Methods: We retrospectively calculated HMRs from early and late anterior-planar equivalent and planar images acquired from 173 patients in 177 studies using D-SPECT and Anger cameras, respectively. The D-SPECT HMRs were cross-calibrated to an Anger camera using conversion coefficients based on previous phantom findings, then standardized to medium-energy general-purpose collimator conditions. Relationships between HMRs before and after corrections were investigated. Late HMRs were classified into four cardiac mortality risk groups and divided into two groups using a threshold of 2.2 to verify diagnostic performance concordance. Results: Correction improved linear regression lines and differences in HMRs among the groups. The overall ratios of perfect concordance were (134 [75.7%] of 177), and higher in groups with very low (49 [80.3%] of 61) and high (51 [86.4%] of 59) HMRs when the standardized HMR was classified according to cardiac mortality risk. That between the systems was the highest (164 [92.7%] of 177) when the HMR was divided by a threshold value of 2.2. Conclusions: Phantom-based conversion can standardize HMRs between D-SPECT and Anger cameras because the standardized HMR provided comparable diagnostic performance. Our findings indicated that this conversion could be applied to multicenter studies that include both D-SPECT and Anger cameras.

Modified signal-to-noise ratio in the liver using the background-to-lung activity ratio to assess image quality of whole-body 18F-fluorodeoxyglucose positron emission tomography.

The signal-to-noise ratio in the liver (SNR liver) is commonly used to assess the quality of positron emission tomography (PET) images; however, it is weakly correlated with visual assessments. Conversely, the noise equivalent count (NEC) density showed a strong correlation with visual assessment but did not consider the effects of image reconstruction conditions. Therefore, we propose a new indicator, the modified SNR liver, and plan to verify its usefulness by comparing it with conventional indicators. We retrospectively analyzed 103 patients who underwent whole-body PET/computed tomography (CT). Approximately 60 min after the intravenous injection of 18F-fluorodeoxyglucose (FDG), the participants were scanned for 2 min/bed. The SNR liver and NEC density were calculated according to the Japanese guidelines for oncology FDG-PET/CT. The modified SNR live was calculated by multiplying the background-to-lung activity ratio by the SNR liver. Patients were classified into groups based on body mass index (BMI) and visual scores. Subsequently, the relationships between these physical indicators, BMI, and visual scores were evaluated. Although the relationship between the modified SNR liver and BMI was inferior to that of NEC density and BMI, the modified SNR liver distinguished the BMI groups more clearly than the conventional SNR liver. Additionally, the modified SNR liver distinguished low visual scores from high scores more accurately than the conventional SNR liver and NEC density. Whether the modified SNR liver is more suitable than the NEC density remains equivocal; however, the modified SNR liver may be superior to the conventional SNR liver for image-quality assessment.

Clinical Validation of Japanese Normal Myocardial Perfusion Imaging Databases Using Semi-conductor Gamma Camera (D-SPECT): Japanese Society of Nuclear Cardiology Working Group Reports.

Objective: A working group (WG) of the Japanese Society of Nuclear Cardiology (JSNC) determined Japanese normal databases of myocardial perfusion single-photon emission computed tomography (SPECT) on semi-conductor gamma camera (D-SPECT), and the aim of this study was to validate its clinical utility. Materials and methods: The normal myocardial perfusion SPECT (MPS) databases of Japanese patients in the 201Tl stress/redistribution protocol (201Tl protocol), 99mTc stress/rest or rest/stress protocol (99mTc protocol), and rest 99mTc/stress 201Tl simultaneous acquisition dual-isotope protocol (SDI protocol) were created by JSNC WG. The WG collected clinical cases for the 201Tl protocol (male/female [m/f], 8/8), 99mTc protocol (m/f, 9/7), and SDI protocol (m/f, 10/10) from WG participating hospitals. Four WG members read those clinical cases on a 17-segment and 5-point scale (0-4). Using the most frequent values as the score for each segment, weighted κ values were calculated with the scores obtained from quantitative perfusion software (QPS). Results: Weighted κ values were as follows; 201Tl stress/female, 0.77; 201Tl rest/female, 0.74; 201Tl stress/male, 0.81; 201Tl rest/male, 0.68; 99mTc stress/female, 0.77; 99mTc rest/female, 0.62; 99mTc stress/male, 0.77; 99mTc rest/male, 0.75; SDI stress/female, 0.87; SDI rest/female, 0.82; SDI stress/male, 0.87; SDI rest/male, 0.85. Conclusions: The diagnostic accuracy of Japanese MPS normal databases on D-SPECT were comparable with nuclear cardiology expert reading and further clinical applications are expected.

Electrocardiographic Diagnosis of Hypertrophic Cardiomyopathy in the Pre- and Post-Diagnostic Phases in Children and Adolescents.

BACKGROUND: The usefulness of electrocardiographic (ECG) voltage criteria for diagnosing hypertrophic cardiomyopathy (HCM) in pediatric patients is poorly defined.Methods and Results:ECGs at the 1st grade (mean [±SD] age 6.6±0.3 years) were available for 11 patients diagnosed with HCM at around the 7th grade (13.2±0.3 years). ECGs were available for another 64 patients diagnosed with HCM in the 1st (n=15), 7th (n=32), and 10th (n=17) grades. Fifty-one voltage criteria were developed by grade and sex using 62,841 ECGs from the general population. Voltage criteria were set at the 99.95th percentile (1/2,000) point based on the estimated prevalence of childhood HCM (2.9 per 100,000 [1/34,483]) to decrease false negatives. Conventional criteria were from guidelines for school-aged children in Japan. Of 11 patients before diagnosis, 2 satisfied conventional criteria in 1st grade; 5 (56%) of the remaining 9 patients fulfilled 2 voltage criteria (R wave in limb-lead I [RI]+S wave in lead V3 [SV3] and R wave in lead V3 [RV3]+SV3). Robustness analysis for sensitivity showed RV3+SV3 was superior to RI+SV3. For all patients after diagnosis, RI+SV4 was the main candidate. However, conventional criteria were more useful than voltage criteria. CONCLUSIONS: Early HCM prediction was possible using RV3+SV3 in >50% of patients in 1st grade. Voltage criteria may help diagnose prediagnostic or early HCM, and prevent tragic accidents, although further prospective studies are required.

Superior mediastinal lymphadenopathy by silicosis mimicking metastasis of papillary thyroid carcinoma - Case report and literature review.

Silicosis is caused by inhalation of silica dust and is the most common type of pneumoconiosis. The characteristics of silicosis are inflammation of lung tissue and calcified lymphadenopathy of pulmonary hilum, mediastinum and paratrachea. We present a papillary thyroid carcinoma (PTC) case with paratracheal and superior mediastinal calcified lymphadenopathy caused by silicosis. The patient did not exhibit any respiratory symptoms or abnormal chest x-ray findings due to early phase silicosis. The lymph nodes were thought to be metastasis of PTC before surgery. Patient underwent total thyroidectomy with neck and superior mediastinum dissection. Post-surgery pathological examination exhibited coexistence of silica nodules and micrometastasis of PTC in paratracheal lymph nodes, but only silica nodules were observed in superior mediastinum lymph nodes. Patient's occupation was office worker but had worked as a stonemason for several decades prior. This is a first observed case of superior mediastinal lymphadenopathy by silicosis mimicking metastasis of PTC. Benign calcified lymphadenopathy may mimic metastasis of PTC in the evaluation of neck or mediastinal lesions.

Electrocardiographic ST-T Area Assessed by a Computerized Quantitative Method and Its Relation to Cardiovascular Events: The J-HOP Study.

BACKGROUND: Although many studies have reported that the presence of minor or major ST-T change of electrocardiography (ECG) was associated with a risk of cardiovascular events, it is not clear whether there is a difference in the prognostic power depending on the summation of ST-T area (ST-Tarea) assessed by a quantitative method. METHODS: Electrocardiograms were performed in 834 clinical patients with one or more cardiovascular risks. ST-Tarea was assessed as the area enclosed by the baseline from the end of the QRS complex to the end of the ST-T segment using a computerized quantitative method. We used the lower magnitude of ST-Tarea in the V5 or V6 lead for the analysis. RESULTS: After a mean follow-up 8.4 ± 2.9 years (7,001 person-years), there were 92 cardiovascular events. With adjustment for covariates, the results from Cox proportional hazards models (Model 1) suggested that the lowest quartile of ST-Tarea was associated with a higher risk for cardiovascular outcome compared with the remaining quartile groups (hazard ratio, 2.08; 95% confidence interval, 1.36-3.16, P < 0.01). Even when adding the ECG left ventricular hypertrophy by Cornell voltage (Model 2) and Cornell product (Model 3) to Model 1, the significance remained (both P < 0.01). When we used ST-Tarea as a continuous variable substitute for the lowest quartile of ST-Tarea, these associations were similar in all models (all P < 0.01). CONCLUSION: The lower summations of ST-T area assessed by a computerized quantitative method were associated with increased risk of cardiovascular disease incidence in a clinical population.

Standard Values and Characteristics of Electrocardiographic Findings in Children and Adolescents.

BACKGROUND: Reference values and the characteristics of the electrocardiographic (ECG) findings using a large number of subjects are lacking for children and adolescents.Methods and Results:A total of 56,753 digitally stored ECGs of participants in a school-based ECG screening system were obtained between 2006 and 2009 in Kagoshima, Japan. Each ECG was manually reviewed by 2 pediatric cardiologists and only ECGs with sinus rhythm were included. A final total of 48,401 ECGs from 16,773 1st (6 years old, 50% girls), 18,126 7th (12 years old, 51% girls), and 13,502 10th graders (15 years old, 52% girls) were selected. ECG variables showed differences in age and sex. However, the effects of age and sex on ECG variables such as the PQ interval, QRS voltage, and STJ segment were also different. The 98th percentile values of well-known surrogate parameters for ventricular hypertrophy in the present study were much higher than the conventional criteria. CONCLUSIONS: The present study of a large number of pediatric subjects showed that the effects of age and sex on ECG parameters are different, and that criteria for ventricular hypertrophy should be newly determined by age and sex. We have developed reference data for STJ segment elevation for children and adolescents. These findings are useful for creating guidelines and recommendations for interpretation of pediatric ECG.

Comparison of image quality between step-and-shoot and continuous bed motion techniques in whole-body 18F-fluorodeoxyglucose positron emission tomography with the same acquisition duration.

OBJECTIVE: This study aimed to compare the qualities of whole-body positron emission tomography (PET) images acquired by the step-and-shoot (SS) and continuous bed motion (CBM) techniques with approximately the same acquisition duration, through phantom and clinical studies. METHODS: A body phantom with 10-37 mm spheres was filled with 18F-fluorodeoxyglucose (FDG) solution at a sphere-to-background radioactivity ratio of 4:1 and acquired by both techniques. Reconstructed images were evaluated by visual assessment, percentages of contrast (%Q H) and background variability (%N) in accordance with the Japanese guideline for oncology FDG-PET/computed tomography (CT). To evaluate the variability of the standardized uptake value (SUV), the coefficient of variation (CV) for both maximum SUV and peak SUV was examined. Both the SUV values were additionally compared with those of standard images acquired for 30 min, and their accuracy was evaluated by the %difference (%Diff). In the clinical study, whole-body 18F-FDG PET/CT images of 60 patients acquired by both techniques were compared for liver signal-to-noise ratio (SNRliver), CV at end planes, and both SUV values. RESULTS: In the phantom study, the visual assessment and %Q H values of the two techniques did not differ from each other. However, the %N values of the CBM technique were significantly higher than those of the SS technique. Additionally, the CV and %Diff for both SUV values in the CBM images tended to be slightly higher than those in SS images. In the clinical study, the SNRliver values of CBM images were significantly lower than those of SS images, although the CV at the end planes in CBM images was significantly lower than those in SS images. In the Bland-Altman analysis for both SUV values, the mean differences were close to 0, and most lesions exhibited SUVs within the limits of agreement. CONCLUSIONS: The CBM technique exhibited slightly lesser uniformity in the center plane than the SS technique. Additionally, in the phantom study, the CV and %Diff of SUV values in CBM images tended to be slightly higher than those of SS images. However, since these differences were subtle, they might be negligible in clinical settings.

Cross calibration of 123I-meta-iodobenzylguanidine heart-to-mediastinum ratio with D-SPECT planogram and Anger camera.

BACKGROUND: Cardiac 123I-meta-iodobenzylguanidine (MIBG) uptake is quantified using the heart-to-mediastinum ratio (HMR) with an Anger camera. The relationship between HMR determined using D-SPECT with a cadmium-zinc-telluride detector and an Anger camera is not fully understood. Therefore, the present study aimed to define this relationship using images derived from a phantom and from patients. METHODS: Cross-calibration phantom studies using an Anger camera with a low-energy high-resolution (LEHR) collimator and D-SPECT, and clinical 123I-MIBG studies proceeded in 40 consecutive patients (80 studies). In the phantom study, a conversion coefficient (CC) was defined based on phantom experiments and applied to the Anger camera and the D-SPECT detector. The HMR was calculated using anterior images with the Anger camera and anterior planograms with D-SPECT. First, the HMR from D-SPECT was cross-calibrated to the Anger camera, and then, the HMR from both cameras were converted to the medium-energy general-purpose collimator condition (CC 0.88; ME88 condition). The relationship between HMR and corrected and uncorrected methods was examined. A 123I-MIBG washout rate was calculated using both methods with and without background subtraction. RESULTS: Based on the phantom experiments, the CC of the Anger camera with an LEHR collimator and of D-SPECT using an anterior planogram was 0.55 and 0.63, respectively. The original HMR from the Anger camera and D-SPECT was 1.76 ± 0.42 and 1.86 ± 0.55, respectively (p < 0.0001). After D-SPECT HMR was converted to the Anger camera condition, the corrected D-SPECT HMR became comparable to the values under the Anger camera condition (1.75 ± 0.48, p = n. s.). When the HMR measured using the two cameras were converted under the ME88 condition, the average standardized HMR from the Anger camera and D-SPECT became comparable (2.21 ± 0.65 vs. 2.20 ± 0.75, p = n. s.). After standardization to the ME88 condition, a systematic difference in the linear regression lines disappeared, and the HMR from both the Anger (StdHMRAnger) and D-SPECT (StdHMRDSPECT) became comparable. Additional correction using a regression line further improved the relationship between both HMR [StdHMRDSPECT = 0.09 + 0.98 × StdHMRAnger (R 2 = 0.91)]. The washout rate closely correlated with and without background correction between both methods (R 2 = 0.83 and 0.65, respectively). CONCLUSION: The phantom-based conversion method is applicable to D-SPECT and enables the common application of HMR irrespective of D-SPECT and the Anger camera.

Importance of (123)I-ioflupane SPECT and Myocardial MIBG Scintigraphy to Determine the Candidate of Deep Brain Stimulation for Parkinson's Disease.

(123)I-ioflupane SPECT (DaTscan) is an examination that detects presynaptic dopamine neuronal dysfunction, and has been used as a diagnostic tool to identify degenerative parkinsonism. Additionally, myocardial (123)I-metaiodobenzyl guanidine (MIBG) scintigraphy measures the concentration of cardiac sympathetic nerve fibers and is used to diagnose Parkinson's disease (PD). These exams are used as adjuncts in the diagnosis of parkinsonism, however, the relationship of these two examinations are not well-known. We investigated the relationship of these two scanning results specifically for determining the use of deep brain stimulation therapy (DBS). Subjects were Japanese patients with suspected striatonigral degeneration, including PD; DaTscans and myocardial MIBG scintigraphy were performed. The mean values of the left-right specific binding ratios (SBRs) from the DaTscan, and the early/delayed heart-to-mediastinum ratios (HMRs) from the MIBG scintigraphy were calculated. Using simple linear regression analysis, we compared the SBR and early/delayed HMR values. Twenty-four patients were enrolled in this study. Twenty-one patients were positive via the DaTscan, and the MIBG scintigraphy results showed 14 patients were positive. SBR and both early and delayed HMR were positively correlated in cases of PD, but negative in non-PD cases. A mean SBR value less than 3.0 and a delayed HMR value less than 1.7 indicated a Hoehn-Yahr stage 3 or 4 for PD, which is commonly regarded as a level appropriate for initiating DBS therapy. Our results indicate that performing both DaTscan and MIBG scintigraphy is useful for the evaluation of surgical intervention in PD.

Thyroid remnant ablation using 1,110 MBq of I-131 after total thyroidectomy: regulatory considerations on release of patients after unsealed radioiodine therapy.

OBJECTIVES: This study was undertaken to measure the radiation exposure level of caregivers following outpatient NaI (I-131) 1,110 MBq therapy for remnant thyroid ablation after total thyroidectomy in patients with differentiated thyroid cancer, and to evaluate the influence of activities of daily living on radiation exposure level, with the goal of proposing an optimum method of I-131 therapy. METHODS: The study included 37 patients with differentiated thyroid cancer, who had undergone total thyroidectomy and received outpatient based remnant thyroid ablation using NaI (I-131) 1,110 MBq, who were satisfying the following requirements: (1) patients who have no evidence of distant metastases, (2) whose living environments were appropriate for outpatient I-131 (1,110 MBq) therapy, and (3) patients who gave written informed consent. The dose rate at a distance of 1 m from the body surface of the patient at the moment of release was measured using survey meters of the GM type or ionization chamber type. The dose level for the caregiver was measured with a personal dosimeter in all cases. RESULTS: The dose rate at a distance of 1 m from the patient's body surface 1 h after I-131 administration was in the range of 29-115 µSv/h (mean 63.8 µSv/h). The 7-day cumulative effective dose of caregivers was 0.11 ± 0.08 mSv, on an average, in 34 dosimeters. In 31 of 34 dosimeters, cumulative effective dose of caregivers was below 0.2 mSv. Dose levels exceeding 0.2 mSv were recorded in 3 cases (0.21, 0.35 and 0.43 mSv in one case each). These results suggest that the exposure level of family members (caregiver and others) was minimal and is lower than the radiation levels affecting human environments. CONCLUSION: Outpatient-based remnant thyroid ablation with I-131 (1,110 MBq) performed after total thyroidectomy in patients with differentiated thyroid cancer is safe if applied in accordance with the appropriate supervision and guidance by experts with certain qualifications.

Regional wall thickening in gated myocardial perfusion SPECT in a Japanese population: effect of sex, radiotracer, rotation angles and frame rates.

PURPOSE: Gated single-photon emission computed tomography (SPECT) imaging of myocardium by (99m)Tc and (201)Tl is used extensively to measure quantitative cardiac functional parameters. However, factors affecting normal values for myocardial functional parameters and population-specific standards have not yet been established. The aim of the study was to determine the effect of sex, radiotracer, rotation angles and frame rates on resting myocardial wall thickening (WT) and to develop a Japanese standard of normal values for WT. METHODS: Data from a total of 202 patients with low possibility of having cardiac problems were collected from nine hospitals throughout Japan. Patients were divided into five groups according to study protocol, and WT was evaluated according to the 17-segment and four-region (basal, mid and apical regions and the apex) polar map distribution. RESULT: WT was generally higher in women than in men irrespective of the use of radiotracers, rotation angles or frame rates, and the difference was highly significant in the mid and apical regions. In any protocol used, resting myocardial thickening in the apex was higher than in the mid and apical regions, and thickening was lowest in the basal region, suggesting heterogeneous regional myocardial thickening (%) in normal subjects. Different rotation angles showed no significant change on WT, but different frame rates and tracers showed significant WT change in both sexes. Percent thickening of the myocardium was significantly higher in imaging by (99m)Tc-labelled tracers than in (201)Tl. CONCLUSION: Sex, radiotracers and frame rates had a significant effect on myocardial thickening, and the importance of population-specific standards should be emphasized. A normal database can serve as a standard for gated SPECT evaluation of myocardial thickening in a Japanese population and might be applicable to Asian populations having a similar physique.

Airway complication occurring during radioiodine treatment for Graves' disease.

Airway complications rarely occur in 131I radioiodine therapy for Graves' disease. This study presents two cases in which 131I therapy caused this acute complication. The patients complained of the symptom 6 h and 33 h after administration of 131I. A histamine H1 receptor antagonist and hydrocortisone rapidly resolved symptoms in both cases. These two cases remind physicians that 131I therapy for Graves' disease may cause potentially life-threatening complications.

Fluctuation of adenosine concentration by modes of intravenous infusion based on mathematical simulation and experiments.

OBJECTIVE: Adenosine, which has been used for a myocardial perfusion scan, shows rapid clearance from blood because of its short half-life of <10 seconds. This simulation study evaluates influences of modes of radionuclide injection on ventricular adenosine concentration when one intravenous injection line is used. METHODS: Assuming that radionuclide injection is a unit impulse, time-activity curves were measured in the left ventricle (LV) and fitted by a gamma function. Typical patterns of concentration fluctuation when adenosine infusion was temporarily modified were calculated by the convolution integral of input function and unit impulse response. Variation of concentration was measured by experiments using continuous 99mTc injection and co-infusion of water via a three-way stopcock. Modes of co-infusion with various infusion speeds and volumes were examined. RESULTS: Intermission of adenosine infusion and rapid displacement by radionuclide co-injection significantly influenced the adenosine concentration in LV. Intermission of adenosine infusion for 2 seconds caused a 15% decrease in the adenosine concentration in the left ventricle. When a square-shaped input was assumed, a three-fold higher concentration of adenosine for 3 seconds created by radionuclide injection resulted in a +42% increase in the LV concentration. Based on a measured input function, radionuclide injection using three-way stopcock through one route caused a two- to three-fold increase in the steady concentration in the vein just after injection. When 0.5 ml of radionuclide was slowly co-injected, with three ways opened, it caused a relatively low fluctuation, creating a +34% to -47% change in concentration of LV. A flush of radionuclide with physiological saline significantly increased the adenosine concentration in LV, when short half-lives were assumed. CONCLUSION: An intravenous adenosine and radiopharmaceutical injection in the same line is feasible. However, the fluctuation of concentration depends significantly on the mode of injection. To minimize the fluctuation, a slow injection of a small volume of a myocardial imaging agent via a co-injection route, with three ways opened, is recommended.

Effect of left ventricular function on diagnostic accuracy of FDG SPECT.

OBJECTIVES: Fluorine-18 fluorodeoxyglucose (FDG) SPECT has emerged as an alternative to dedicated PET imaging. However, it remains uncertain whether FDG SPECT is an as accurate for viability assessment as FDG PET in patients with severely reduced left ventricular function. The aim of the study was to assess the diagnostic accuracy of FDG SPECT in a head-to-head comparison with FDG PET, and divide the patients according to the severity of left ventricular dysfunction. METHODS: A total of 47 patients, with a history of myocardial infarction underwent FDG/perfusion (99mTc-sestamibi or 201Tl) SPECT as well as FDG/13N-ammonia PET. The patients were divided into 2 subgroups based on the left ventricular ejection fraction (LVEF) (35% cutoff). The left ventricular myocardium was divided into 13 segments, and each segment was classified as viable or scar using a semi-quantitative scoring system based on defect severity and the presence or absence of perfusion-FDG mismatch. RESULTS: Of the 47 patients studied, 23 had LVEF < 35% (low LVEF group; mean 25 +/- 7%), whereas the remaining 24 had LVEF > or = 35% (high LVEF group; mean 47 +/- 6%). In the low LVEF group, 213 segments (71%) were dysfunctional, as compared to 102 (33%) in the high LVEF group. The agreement for detection of viability between PET and SPECT in the low LVEF group was 82% (kappa 0.63), which was not different from the agreement in the high LVEF group (85%, kappa 0.66, p = 0.42 versus low LVEF group). CONCLUSIONS: The results indicate that FDG SPECT can be used for tissue viability assessment regardless of the severity of left ventricular dysfunction.

Accuracy of cardiac PET imaging using post-injection transmission scan.

UNLABELLED: The purpose of this study was to investigate the accuracy of cardiac PET with post-injection transmission scans. METHODS: We performed a phantom study using 18F solution as well as 13N-ammonia PET study of ten patients. The average activities of no myocardial defect phantom model were estimated, and myocardial defect sizes of 12 phantom models were measured by pre- and post-injection transmission methods at various 18F activities. In 13N-ammonia PET at rest and during adenosine triphosphate (ATP) stress studies, measured defect sizes were compared between both methods. RESULTS: The ratios of average activity estimated by both methods (post/pre value) were almost 1.00 at each 18F activity and segment. Measured defect sizes by both methods showed an excellent correlation with true defect sizes (r = 0.98, p < 0.01 for pre vs. true value: r = 0.98, p < 0.01 for post vs. true value). The mean absolute errors of measurements were minimal up to 3.5% LV, and were similar between both methods. In 13N-ammonia PET, measured defect sizes by both methods also showed a good correlation (r = 0.97, p < 0.01). CONCLUSION: The results indicate that cardiac PET imaging with post-injection transmission scan provides information on myocardial tracer activity as well as myocardial defect size as does conventional pre-injection transmission method.

Assessment of global and regional left ventricular function by electrocardiographic gated N-13 ammonia positron emission tomography in patients with coronary artery disease.

BACKGROUND: Electrocardiographic gated 13N-ammonia positron emission tomography (PET) enables simultaneous assessment of myocardial blood flow and left ventricular (LV) function. The aim of this study was to assess the accuracy of gated 13N-ammonia PET for evaluating global and regional LV function in patients with coronary artery disease (CAD) in comparison with conventional left ventriculography (LVG). METHODS AND RESULTS: Fifty-four patients with CAD underwent gated 13N-ammonia PET and LVG. The LV end-diastolic and end-systolic volumes (LVEDV, LVESV) and ejection fraction (LVEF) by gated 13N-ammonia PET were calculated using Cedars-Sinai automated quantitative gated single photon emission computed tomography (QGS) and compared with those obtained by LVG. The regional wall motion (RWM) was visually scored, and compared with that on LVG. There were good correlations between the 2 methods for LVEF, LVEDV and LVESV (R=0.828, R=0.821 and R=0.874 respectively). The RWM assessed by gated 13N-ammonia PET also agreed well with that by LVG (complete agreement was 70.4%, kappa=0.58). CONCLUSIONS: Gated 13N-ammonia PET combined with QGS works reasonably well for the assessment of both global and regional LV function in CAD patients, although additional calibration may be necessary.

Electrocardiographic-gated dual-isotope simultaneous acquisition SPECT using 18F-FDG and 99mTc-sestamibi to assess myocardial viability and function in a single study.

PURPOSE: Dual-isotope simultaneous acquisition single-photon emission computed tomography (DISA SPECT) with 18F-fluorodeoxyglucose (FDG) and (99m)Tc-sestamibi appears attractive for the detection of viable myocardium because it permits simultaneous assessment of glucose utilisation and perfusion. Another potential benefit of this approach is that the measurement of left ventricular (LV) function may be possible by ECG gating. The aim of this study was to test the hypothesis that both myocardial viability and LV function can be assessed by a single ECG-gated 18F-FDG/(99m)Tc-sestamibi DISA SPECT study, based on comparison with 18F-FDG/13N-ammonia positron emission tomography (PET) and magnetic resonance imaging (MRI) as reference techniques. METHODS: Thirty-three patients with prior myocardial infarction underwent ECG-gated 18F-FDG/(99m)Tc-sestamibi DISA SPECT and 18F-FDG/13N-ammonia PET on a single day. Of these, 25 patients also underwent cine-MRI to assess LV function. The LV myocardium was divided into nine regions, and each region was classified as viable or scar using a semiquantitative visual scoring system as well as quantitative analysis. The global and regional LV function measured by gated SPECT was compared with the results of MRI. RESULTS: There was good agreement in respect of viability (90-96%, kappa 0.74-0.85) between DISA SPECT and PET by either visual or quantitative analysis. Furthermore, although both global and regional LV function measured by gated SPECT agreed with those by MRI, (99m)Tc-sestamibi showed a closer correlation with MRI than did 18F-FDG. CONCLUSION: In conclusion, ECG-gated DISA SPECT provides information on myocardial viability, as well as global and regional LV function, similar to that obtained by PET and MRI.

Myocardial distribution of (18)F-FDG and (99m)Tc-sestamibi on dual-isotope simultaneous acquisition SPET compared with PET.

A dual-isotope simultaneous acquisition (DISA) single-photon emission tomography (SPET) protocol with fluorine-18 fluorodeoxyglucose ((18)F-FDG) and a technetium-99m labelled flow tracer is attractive because it permits assessment of both myocardial glucose utilisation and flow within a single study. Differences in physical and physiological characteristics between (18)F-FDG and the (99m)Tc-labelled flow tracer, however, may cause differences in myocardial activity distribution between the agents. The aim of this study was to investigate the relation between the myocardial distribution of (18)F-FDG and a (99m)Tc-labelled flow tracer on DISA SPET in comparison with nitrogen-13 ammonia/(18)F-FDG positron emission tomography (PET). Nine normal volunteers without cardiac disease and ten patients with known coronary artery disease (CAD) underwent (13)N-ammonia/(18)F-FDG PET and (99m)Tc-sestamibi/(18)F-FDG DISA SPET. Using a semiquantitative polar map approach, the left ventricular myocardium was divided into nine segments, and relative regional activity was calculated for each segment. A segment was considered to have concordant uptake between (18)F-FDG and flow tracer if the difference in measured regional activity between the tracers was < or =10% of peak activity, and the percentage of concordant segments was calculated for each subject. There was a good overall concordance of myocardial activity between the agents on DISA SPET (84.0%+/-14.8%) in normals, which was comparable to that seen on PET (86.4%+/-14.5%, NS vs DISA SPET). However, the myocardial activity distributions of (18)F-FDG and flow tracer were not identical in that reduced flow tracer activity was seen in the basal segments on DISA SPET in both normals and CAD patients. It is concluded that there is good overall concordance of activity between (18)F-FDG and flow tracer in normal myocardium on DISA SPET, which is comparable to that on PET, supporting the use of combined (99m)Tc-flow tracer/(18)F-FDG imaging for the detection of viable myocardium. However, there is a difference in the myocardial activity distribution between the agents in both normals and CAD patients, the difference being particularly evident in the basal segments. Therefore, careful image interpretation that takes into consideration the different normal activity distribution between the tracers and/or a tracer-specific normal database is necessary for comparison with patient studies.