We consider Petri net models of discrete event systems with faulty behaviors which are triggered by the firing of failure transitions. We extend a necessary and sufficient, condition for diagnosability shown by Sampath et al. to unbounded Petri nets. But it is algorithmically impossible to check the condition in general. We introiduce methods for modification of coverability trees in order to detect failure transitions. By using such approximated sets, we propose two kinds of diagnosers called a difference marking wdiagncser and an w-refined diagncser. For o b servable places whose token numbers are replaced by w in the coverability trees, the former diagnoser calculates difference between token numbers before and after partially observed markings change, and detects failures. In the latter diagnoser, we refine the symbol w, and modify the coverability tree in order to distinguish markings reachable by normal behaviors from those reachable by faulty behaviors.
BackgroundThe heart-to-mediastinum ratio (HMR) of 123I-metaiodobenzylguanidine (MIBG) showed variations among institutions and needs to be standardized among various scinticamera-collimator combinations.MethodsA 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.ResultsThe 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).ConclusionBy 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.
As a 2-year project of the Japanese Society of Nuclear Medicine working group activity, normal myocardial imaging databases were accumulated and summarized. Stress-rest with gated and non-gated image sets were accumulated for myocardial perfusion imaging and could be used for perfusion defect scoring and normal left ventricular (LV) function analysis. For single-photon emission computed tomography (SPECT) with multi-focal collimator design, databases of supine and prone positions and computed tomography (CT)-based attenuation correction were created. The CT-based correction provided similar perfusion patterns between genders. In phase analysis of gated myocardial perfusion SPECT, a new approach for analyzing dyssynchrony, normal ranges of parameters for phase bandwidth, standard deviation and entropy were determined in four software programs. Although the results were not interchangeable, dependency on gender, ejection fraction and volumes were common characteristics of these parameters. Standardization of 123I-MIBG sympathetic imaging was performed regarding heart-to-mediastinum ratio (HMR) using a calibration phantom method. The HMRs from any collimator types could be converted to the value with medium-energy comparable collimators. Appropriate quantification based on common normal databases and standard technology could play a pivotal role for clinical practice and researches.
The H/M ratio with the ME collimator, after application of the TEW or IDW methods, was close to the theoretical value in the phantom study. However, the corrected H/M ratios with the LEHR collimator provided comparable H/M ratios to the uncorrected ME data in phantom and clinical studies.
PurposeArtificial 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.MethodsThe 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.ResultsThe 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.ConclusionThe 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.
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-tomediastinum (H/M) ratio in cardiac metaiodobenzylguanidine (MIBG) imaging.Method. 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 to the ME-comparable H/M ratio was examined in two settings: a Japanese standard MIBG database (n=62) and multi-center studies (n=49). In a multi-center study, probable Alzheimer 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 a 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 2 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 multicenter comparison of H/M ratios.Key Words: 123 I-metaiodobenzylguanidine; heart-to-mediastinum ratio; calibration phantom; Lewy-body disease; standardization Introduction123 I-metaiodobenzylguanidine (MIBG) has been used extensively in fields of cardiology and neurology as a unique imaging method to evaluate sympathetic nerve activity and its integrity [1][2][3][4][5][6][7]. Inter-institutional differences in MIBG quantification using the heart-tomediastinum ratio (H/M) have hampered multi-center comparison of the H/M ratio, and single-center results could not easily be extrapolated to other hospitals [8]. Since the difference in collimator type has been investigated and found to be one of the major confounders of the results, a practical standardization method for quantification has been sought [9][10][11][12].In neurological studies, patients with Parkinson disease and dementia with Lewy bodies (DLB), which is categorized as Lewy-body disease demonstrated significantly lower H/ M ratios both in early and late imaging [4][5][6][7]. Since the patients with Lewy-body disease showed lower H/M values compared with those of normal populations, we used this patient group for a pilot study of the procedure for correction of H/M ratios. In addition, since a multi-center study including DLB and MIBG imaging has started in Japan, an a...
The H/M ratio using the semi-automated method showed high reproducibility in both early and delayed imaging.
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