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| 1.
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Shibutani, Takayuki ; Nakajima, Kenichi ; Wakabayashi, Hiroshi ; Mori, Hiroshi ; Matsuo, Shinro ; Yoneyama, Hiroto ; Konishi, Takahiro ; Okuda, Koichi ; Onoguchi, Masahisa ; Kinuya, Seigo ; 澁谷, 孝行 ; 中嶋, 憲一 ; 若林, 大志 ; 松尾, 信郎 ; 米山, 寛人 ; 小野口, 昌久 ; 絹谷, 清剛
概要:
金沢大学医薬保健研究域保健学系<br />ObjectivesThe patient-based diagnosis with an artificial neural network (ANN) has shown potential u
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tility for the detection of coronary artery disease; however, the region-based accuracy of the detected regions has not been fully evaluated. The aim of this study was to demonstrate the accuracy of all detected regions compared with expert interpretation.\nMethodsA total of 109 abnormal regions including 33 regions with stress defects and 76 regions with ischemia were examined, which were derived from 21 patients who underwent myocardial perfusion SPECT within 45 days of coronary angiography. The gray and color scale images, a polar map of stress, rest and difference, and left ventricular function were displayed on the monitor to score the extent and severity of stress defect and ischemia. Two experienced nuclear medicine physicians (Observers A and B) scored the abnormality with a 4-point scale and draw abnormal regions on a polar map. The gold standard was determined by the final judgment of normal or abnormal by the consensus of two other independent expert nuclear cardiologists, and was compared with the stress defect and ischemia derived from ANN.\nResultsThe concordance rate of ANN to the gold standard was higher than that of two observers. Furthermore, the κ coefficient indicated moderate to substantial agreement for stress defect and slight to the fair agreement for ischemia. The area under the curve (AUC) of ANN was the highest for both stress defect and ischemia; in particular, the ANN of ischemia showed significantly higher AUC than Observer A (p = 0.005). The ANN of stress defect showed higher specificity compared with two observers, while the ANN of ischemia showed higher sensitivity. Consequently, the accuracy of ANN showed the highest in this study.\nConclusionThe ANN-based regional diagnosis showed a high concordance rate with the gold standard and comparable or even higher than the interpretation by nuclear medicine physicians.<br />Embargo Period 12 months
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Nakajima, Kenichi ; Okuda, Koichi ; Nyström, Karin ; Richter, Jens ; Minarik, David ; Wakabayashi, Hiroshi ; Matsuo, Shinro ; Kinuya, Seigo ; Edenbrandt, Lars
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Purpose In patients with a small heart, defined as an end-systolic volume (ESV) of ≤20 mL calculated using the Quantitat
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ive 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.
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Nakajima, Kenichi ; Hasegawa, Minoru ; Inaki, Anri ; Wakabayashi, Hiroshi ; Hosoya, Tetsuo ; Takahara, Kazuhiko ; Kinuya, Seigo
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金沢大学医薬保健研究域医学系<br />Purpose: Esophageal complication is common in systemic sclerosis (SSc), but scintigraphic transit pa
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tterns based on each subtype have not been understood well. The aim of this study was to develop a new algorithm for integrating a dynamic esophageal transit study and to apply the method to patients with SSc. Methods: A total of 40 patients suspected of having SSc were examined by a dynamic esophageal transit study. The subtypes included 32 with definite SSc (15 limited cutaneous type and 17 diffuse cutaneous type) and 8 with probable SSc. The serial esophageal images were shifted and summed to a functional image (sliding sum image) and compared to a conventional condensed image analysis. Esophageal retention fraction at 90 s (R90) and half-time (T1/2) of transit were also measured. Results: The four patterns of the sliding sum image and condensed image agreed in all patients. Abnormal retention patterns were observed in none of the 8 (0%) patients with the probable SSc and in 15 of 32 (47%) patients with definite SSc (p = 0.014). The severity of scleroderma assessed by modified Rodnan skin thickness score correlated with that of esophageal retention R90 (p = 0.04). Conclusion: The sliding sum image is a simple and effective method for integrating esophageal transit. Patients with definite SSc and severe scleroderma had significantly higher retention patterns, while probable SSc patients showed no esophageal dysmotility. © 2011 The Japanese Society of Nuclear Medicine.
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Nakajima, Kenichi ; Matsuo, Shinro ; Okuda, Koichi ; Wakabayashi, Hiroshi ; Tsukamoto, Kazumasa ; Nishimura, Tsunehiko
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Background:Myocardial perfusion imaging (MPI) has been used to estimate cardiac event risk. The aim of the present study
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is to achieve stable risk estimation based on perfusion scoring and a multi-center prognostic database. Methods and Results:Multivariate logistic regression analysis was performed to estimate cardiac event risk based on a J-ACCESS study. A stress-MPI was performed in 45 patients with coronary artery disease (CAD) and in 25 non-CAD patients. Perfusion defect scoring of summed stress score (SSS) was performed by 5 methods: (1) visual scoring; (2) automatic scoring of 3 short-axis and 1 vertical long-axis slices; (3) visual modification of Method 2; (4) automatic polar map scoring based on a Japanese multi-center database; and (5) visual modification of Method 4. Agreement of SSS between 2 observers was good (r=0.87-0.97). Agreement of estimated cardiac event risk between observers and among 5 methods was very good (r=0.99-1.00). Regarding diagnostic accuracy for CAD, Method 5 showed optimal diagnostic yields (sensitivity 84%, accuracy 77%). Conclusions:Estimation of cardiac event risk in conjunction with polar map segmentation and common normal databases resulted in stable risk values, and might be used for risk stratification in patients suspected of having CAD. © All rights are reserved to the Japanese Circulation Society.
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Okuda, Koichi ; Nakajima, Kenichi ; Matsuo, Shinro ; Wakabayashi, Hiroshi ; Taki, Junichi ; Kinuya, Seigo
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Objectives: Decreases in apical and apex activities - namely, 'apical thinning' - are a well-known phenomenon in attenua
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tion-corrected (AC) myocardial perfusion. The aim of this study was to compare actual myocardial thickness derived from a multidetector-row computed tomography with AC myocardial perfusion count from a hybrid single-photon emission computed tomography/computed tomography to investigate the cause of apical thinning. Methods: We enrolled 21 participants with a low likelihood of coronary artery disease (mean age 65±21 years, 13 men) from 185 consecutive patients and 11 healthy volunteers, who independently underwent Tc-sestamibi single-photon emission computed tomography/computed tomography and 64-slice multidetector-row computed tomography scans. AC and non-AC myocardial perfusion counts and thickness were measured on the basis of a 17-segment model and averaged at the apex, apical, mid, and basal walls. Results: Myocardial thickness at the apex was significantly thinner than that at the apical and mid walls (5.1±1.3, 7.3±1.3, and 9.9±2.4 mm, respectively; P<0.005). AC count at the apex was significantly lower than that at the apical and mid regions (76.0±5.5, 82.8±4.7, and 85.6±3.8, respectively; P<0.002). Moderate relationship was observed between myocardial thickness and AC count (y=-10.5+0.22x, r=0.54, P<0.0001. No relationship was found between thickness and non-AC count (r=0.16, P=0.263). Conclusion: The low apex and apical counts were caused by anatomical thinning of the myocardium in AC myocardial perfusion imaging. Attenuation correction provided an accurate relationship between myocardial count and thickness because of the partial volume effect. © 2011 Wolters Kluwer Health | Lippincott Williams and Wilkins.
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Nakajima, Kenichi ; Nakajima, Yasuo ; Horikoshi, Hiroyuki ; Ueno, Munehisa ; Wakabayashi, Hiroshi ; Shiga, Tohru ; Yoshimura, Mana ; Ohtake, Eiji ; Sugawara, Yoshifumi ; Matsuyama, Hideyasu ; Edenbrandt, Lars
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Background Artificial neural network (ANN)-based bone scan index (BSI), a marker of the amount of bone metastasis, has b
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een shown to enhance diagnostic accuracy and reproducibility but is potentially affected by training databases. The aims of this study were to revise the software using a large number of Japanese databases and to validate its diagnostic accuracy compared with the original Swedish training database. Methods The BSI was calculated with EXINIbone (EB; EXINI Diagnostics) using the Swedish training database (n = 789). The software using Japanese training databases from a single institution (BONENAVI version 1, BN1, n = 904) and the revised version from nine institutions (version 2, BN2, n = 1,532) were compared. The diagnostic accuracy was validated with another 503 multi-center bone scans including patients with prostate (n = 207), breast (n = 166), and other cancer types. The ANN value (probability of abnormality) and BSI were calculated. Receiver operating characteristic (ROC) and net reclassification improvement (NRI) analyses were performed. Results The ROC analysis based on the ANN value showed significant improvement from EB to BN1 and BN2. In men (n = 296), the area under the curve (AUC) was 0.877 for EB, 0.912 for BN1 (p = not significant (ns) vs. EB) and 0.934 for BN2 (p = 0.007 vs. EB). In women (n = 207), the AUC was 0.831 for EB, 0.910 for BN1 (p = 0.016 vs. EB), and 0.932 for BN2 (p < 0.0001 vs. EB). The optimum sensitivity and specificity based on BN2 was 90% and 84% for men and 93% and 85% for women. In patients with prostate cancer, the AUC was equally high with EB, BN1, and BN2 (0.939, 0.949, and 0.957, p = ns). In patients with breast cancer, the AUC was improved from EB (0.847) to BN1 (0.910, p = ns) and BN2 (0.924, p = 0.039). The NRI using ANN between EB and BN1 was 17.7% (p = 0.0042), and that between EB and BN2 was 29.6% (p < 0.0001). With respect to BSI, the NRI analysis showed downward reclassification with total NRI of 31.9% (p < 0.0001). Conclusion In the software for calculating BSI, the multi-institutional database significantly improved identification of bone metastasis compared with the original database, indicating the importance of a sufficient number of training databases including various types of cancers. © 2013 Nakajima et al.
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| 7.
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Nakajima, Kenichi ; Okuda, Koichi ; Nyström, Karin ; Richter, Jens ; Minarik, David ; Wakabayashi, Hiroshi ; Matsuo, Shinro ; Kinuya, Seigo ; Edenbrandt, Lars
概要:
Purpose: In patients with a small heart, defined as an end-systolic volume (ESV) of ≤20 mL calculated using the Quantita
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tive 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. © 2013 The Author(s).
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| 8.
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Nakajima, Kenichi ; Okuda, Koichi ; Yoshimura, Mana ; Matsuo, Shinro ; Wakabayashi, Hiroshi ; Imanishi, Yasuhiro ; Kinuya, Seigo
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Background The heart-to-mediastinum ratio (HMR) of 123I-metaiodobenzylguanidine (MIBG) showed variations among instituti
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ons 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.
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Nakajima, Kenichi ; Matsuo, Shinro ; Wakabayashi, Hiroshi ; Yokoyama, Kunihiko ; Bunko, Hisashi ; Okuda, Koichi ; Kinuya, Seigo ; Nyström, Karin ; Edenbrandt, Lars
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Background:The purpose of this study was to apply an artificial neural network (ANN) in patients with coronary artery di
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sease (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. (Circ J 2015; 79: 1549–1556)
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Okuda, Koichi ; Nakajima, Kenichi ; Yamada, Masato ; Wakabayashi, Hiroshi ; Ichikawa, Hajime ; Arai, Hiroyuki ; Matsuo, Shinro ; Taki, Junichi ; Hashimoto, Mitsumasa ; Kinuya, Seigo
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Objective: The aim of this study was to characterize the optimal reconstruction parameters for ordered-subset expectatio
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n maximization (OSEM) with attenuation correction, scatter correction, and depth-dependent resolution recovery (OSEMACSCRR). We assessed the optimal parameters for OSEMACSCRR in an anthropomorphic torso phantom study, and evaluated the validity of the reconstruction parameters in the groups of normal volunteers and patients with abnormal perfusion. Methods: Images of the anthropomorphic torso phantom, 9 normal volunteers and 7 patients undergoing myocardial perfusion SPECT were acquired with a SPECT/CT scanner. SPECT data comprised a 64 × 64 matrix with an acquisition pixel size of 6.6 mm. A normalized mean square error (NMSE) of the phantom image was calculated to determine both optimal OSEM update and a full width at half maximum (FWHM) of Gaussian filter. We validated the myocardial count, contrast and noise characteristic for clinical subjects derived from OSEMACSCRR processing. OSEM with depth-dependent resolution recovery (OSEMRR) and filtered back projection (FBP) were simultaneously performed to compare OSEMACSCRR. Results: The combination of OSEMACSCRR with 90-120 OSEM updates and Gaussian filter with 13.2-14.85 mm FWHM yielded low NMSE value in the phantom study. When we used OSEMACSCRR with 120 updates and Gaussian filter with 13.2 mm FWHM in the normal volunteers, myocardial contrast showed significantly higher value than that derived from 120 updates and 14.85 mm FWHM. OSEMACSCRR with the combination of 90-120 OSEM updates and 14.85 mm FWHM produced lowest % root mean square (RMS) noise. Regarding the defect contrast of patients with abnormal perfusion, OSEMACSCRR with the combination of 90-120 OSEM updates and 13.2 mm FWHM produced significantly higher value than that derived from 90-120 OSEM updates and 14.85 mm FWHM. OSEMACSCRR was superior to FBP for the % RMS noise (8.52 ± 1.08 vs. 9.55 ± 1.71, p = 0.02) and defect contrast (0.368 ± 0.061 vs. 0.327 ± 0.052, p = 0.01), respectively. Conclusions: Clinically optimized the number of OSEM updates and FWHM of Gaussian filter were (1) 120 updates and 13.2 mm, and (2) 90-120 updates and 14.85 mm on the OSEMACSCRR processing, respectively. Further assessment may be required to determine the optimal iterative reconstruction parameters in a larger patient population. © 2013 The Japanese Society of Nuclear Medicine.
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