Circulation journal : official journal of the Japanese Circulation Society, Jan 3, 2015
The purpose of this study was to apply an artificial neural network (ANN) in patients with corona... more 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 ...
Objectives-We aimed to develop a Japanese normal database for specific acquisition conditions, to... more Objectives-We aimed to develop a Japanese normal database for specific acquisition conditions, to compare US and Japanese normal populations, and to examine effects of camera rotation angle range on the normal limits.
Background. We have developed novel software for semi-automatically measuring heartto-mediastinum... more Background. We have developed novel software for semi-automatically measuring heartto-mediastinum (H/M) ratio in cardiac Iodine-123 ( 123 I)-labeled meta-iodobenzylguanidine (MIBG) imaging. Our aim is to improve the reproducibility of the H/M ratio using the semiautomated method as opposed to the manual method.
Background: To overcome differences in a collimator choice for a 123 I-MIBG heart to mediastinum ... more Background: To overcome differences in a collimator choice for a 123 I-MIBG heart to mediastinum (H/M) ratio, we examined multi-window correction methods with 123 I-dual-window (IDW) and triple-energy-window (TEW) acquisition.
European Journal of Nuclear Medicine and Molecular Imaging, 2013
Purpose In patients with a small heart, defined as an endsystolic volume (ESV) of ≤20 mL calculat... more Purpose In patients with a small heart, defined as an endsystolic 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.
Objective Segmentation with scatter and photopeak window data using attenuation correction (SSPAC... more Objective Segmentation with scatter and photopeak window data using attenuation correction (SSPAC) method can provide a patient-specific non-uniform attenuation coefficient map only by using photopeak and scatter images without X-ray computed tomography (CT). The purpose of this study is to evaluate the performance of attenuation correction (AC) by the SSPAC method on normal myocardial perfusion database. Methods A total of 32 sets of exercise-rest myocardial images with Tc-99 m-sestamibi were acquired in both photopeak (140 keV ± 10%) and scatter (7% of lower side of the photopeak window) energy windows. Myocardial perfusion databases by the SSPAC method and non-AC (NC) were created from 15 female and 17 male subjects with low likelihood of cardiac disease using quantitative perfusion SPECT software. Segmental myocardial counts of a 17-segment model from these databases were compared on the basis of paired t test.
Objective The standard patterns of myocardial radiotracer distribution of 123 I-metaiodobenzylgua... more Objective The standard patterns of myocardial radiotracer distribution of 123 I-metaiodobenzylguanidine (MIBG) and 123 I-b-methyl-p-iodophenyl-pentadecanoic acid (BMIPP) should be defined in a Japanese population. The purpose of this study was to present and provide data on the characteristics of MIBG and BMIPP with respect to myocardial single photon emission computed tomography. Methods The normal database included 123 I-MIBG and 123 I-BMIPP imaging and a 99m Tc-sestamibi/tetrofosmin myocardial perfusion study. The projection images were transferred by digital imaging and communications in medicine (DICOM) format and reconstructed and analyzed with polar maps.
Purpose. The Japanese Society of Nuclear Medicine (JSNM) working group has created a myocardial p... more Purpose. The Japanese Society of Nuclear Medicine (JSNM) working group has created a myocardial perfusion imaging database applicable to standard acquisition protocol. The aim of this study is to validate the diagnostic accuracy of the common normal database compared with the expert interpretation of each institute. Methods. Five institutions participated in this study and used different acquisition settings which included 360°/180° rotation, camera configuration and camera orbits. The software and its version used in each institution also varied. The working group database was applied to detect the culprit coronary territory from a total of 166 patients with coronary artery disease (CAD) and 145 patients with low-likelihood of CAD. Results. When summed stress score ≥4 was defined as significant abnormality, overall sensitivity, specificity and accuracy of patient-based analysis were 77%, 72% and 75%, respectively, based on quantitative analysis using the common database, whereas those by institutional visual expert reading were 72%, 79% and 75%, respectively. Conclusion. The common database, which was created by a multi-center working group and separated between male/female with 180/360° acquisitions, demonstrated comparable diagnostic accuracy to expert interpretation by each institute, and it may be applicable to multi-center studies.
The aim of this study was to characterize the optimal reconstruction parameters for ordered-subse... more The aim of this study was to characterize the optimal reconstruction parameters for ordered-subset expectation 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. 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. 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. 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.
Background: To overcome differences in a collimator choice for a 123 I-MIBG heart to mediastinum ... more Background: To overcome differences in a collimator choice for a 123 I-MIBG heart to mediastinum (H/M) ratio, we examined multi-window correction methods with 123 I-dual-window (IDW) and triple-energy-window (TEW) acquisition. Methods and Results: Standard phantoms which consisted of heart, mediastinum, lung and liver, were generated. Three correction methods were compared: TEW and two IDW methods (IDW 0 and IDW 1 ). Low-energy high-resolution (LEHR), medium-energy (ME) and 123 I specific low-medium-energy high-resolution (LMEHR) collimators were used. Clinical studies were performed in 10 patients. In the phantom study, the H/M ratio was significantly underestimated without correction both with the LEHR and ME collimators (70% and 88% of the true value). When H/M with the LEHR collimator was divided by uncorrected H/M with the ME collimator, the ratio was 80%+/-4%, 98%+/-5%, 104%+/-7%, 98%+/-5% for no correction, TEW, IDW 0 and IDW 1 methods, respectively. Clinical studies with the...
Circulation journal : official journal of the Japanese Circulation Society, Jan 3, 2015
The purpose of this study was to apply an artificial neural network (ANN) in patients with corona... more 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 ...
Objectives-We aimed to develop a Japanese normal database for specific acquisition conditions, to... more Objectives-We aimed to develop a Japanese normal database for specific acquisition conditions, to compare US and Japanese normal populations, and to examine effects of camera rotation angle range on the normal limits.
Background. We have developed novel software for semi-automatically measuring heartto-mediastinum... more Background. We have developed novel software for semi-automatically measuring heartto-mediastinum (H/M) ratio in cardiac Iodine-123 ( 123 I)-labeled meta-iodobenzylguanidine (MIBG) imaging. Our aim is to improve the reproducibility of the H/M ratio using the semiautomated method as opposed to the manual method.
Background: To overcome differences in a collimator choice for a 123 I-MIBG heart to mediastinum ... more Background: To overcome differences in a collimator choice for a 123 I-MIBG heart to mediastinum (H/M) ratio, we examined multi-window correction methods with 123 I-dual-window (IDW) and triple-energy-window (TEW) acquisition.
European Journal of Nuclear Medicine and Molecular Imaging, 2013
Purpose In patients with a small heart, defined as an endsystolic volume (ESV) of ≤20 mL calculat... more Purpose In patients with a small heart, defined as an endsystolic 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.
Objective Segmentation with scatter and photopeak window data using attenuation correction (SSPAC... more Objective Segmentation with scatter and photopeak window data using attenuation correction (SSPAC) method can provide a patient-specific non-uniform attenuation coefficient map only by using photopeak and scatter images without X-ray computed tomography (CT). The purpose of this study is to evaluate the performance of attenuation correction (AC) by the SSPAC method on normal myocardial perfusion database. Methods A total of 32 sets of exercise-rest myocardial images with Tc-99 m-sestamibi were acquired in both photopeak (140 keV ± 10%) and scatter (7% of lower side of the photopeak window) energy windows. Myocardial perfusion databases by the SSPAC method and non-AC (NC) were created from 15 female and 17 male subjects with low likelihood of cardiac disease using quantitative perfusion SPECT software. Segmental myocardial counts of a 17-segment model from these databases were compared on the basis of paired t test.
Objective The standard patterns of myocardial radiotracer distribution of 123 I-metaiodobenzylgua... more Objective The standard patterns of myocardial radiotracer distribution of 123 I-metaiodobenzylguanidine (MIBG) and 123 I-b-methyl-p-iodophenyl-pentadecanoic acid (BMIPP) should be defined in a Japanese population. The purpose of this study was to present and provide data on the characteristics of MIBG and BMIPP with respect to myocardial single photon emission computed tomography. Methods The normal database included 123 I-MIBG and 123 I-BMIPP imaging and a 99m Tc-sestamibi/tetrofosmin myocardial perfusion study. The projection images were transferred by digital imaging and communications in medicine (DICOM) format and reconstructed and analyzed with polar maps.
Purpose. The Japanese Society of Nuclear Medicine (JSNM) working group has created a myocardial p... more Purpose. The Japanese Society of Nuclear Medicine (JSNM) working group has created a myocardial perfusion imaging database applicable to standard acquisition protocol. The aim of this study is to validate the diagnostic accuracy of the common normal database compared with the expert interpretation of each institute. Methods. Five institutions participated in this study and used different acquisition settings which included 360°/180° rotation, camera configuration and camera orbits. The software and its version used in each institution also varied. The working group database was applied to detect the culprit coronary territory from a total of 166 patients with coronary artery disease (CAD) and 145 patients with low-likelihood of CAD. Results. When summed stress score ≥4 was defined as significant abnormality, overall sensitivity, specificity and accuracy of patient-based analysis were 77%, 72% and 75%, respectively, based on quantitative analysis using the common database, whereas those by institutional visual expert reading were 72%, 79% and 75%, respectively. Conclusion. The common database, which was created by a multi-center working group and separated between male/female with 180/360° acquisitions, demonstrated comparable diagnostic accuracy to expert interpretation by each institute, and it may be applicable to multi-center studies.
The aim of this study was to characterize the optimal reconstruction parameters for ordered-subse... more The aim of this study was to characterize the optimal reconstruction parameters for ordered-subset expectation 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. 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. 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. 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.
Background: To overcome differences in a collimator choice for a 123 I-MIBG heart to mediastinum ... more Background: To overcome differences in a collimator choice for a 123 I-MIBG heart to mediastinum (H/M) ratio, we examined multi-window correction methods with 123 I-dual-window (IDW) and triple-energy-window (TEW) acquisition. Methods and Results: Standard phantoms which consisted of heart, mediastinum, lung and liver, were generated. Three correction methods were compared: TEW and two IDW methods (IDW 0 and IDW 1 ). Low-energy high-resolution (LEHR), medium-energy (ME) and 123 I specific low-medium-energy high-resolution (LMEHR) collimators were used. Clinical studies were performed in 10 patients. In the phantom study, the H/M ratio was significantly underestimated without correction both with the LEHR and ME collimators (70% and 88% of the true value). When H/M with the LEHR collimator was divided by uncorrected H/M with the ME collimator, the ratio was 80%+/-4%, 98%+/-5%, 104%+/-7%, 98%+/-5% for no correction, TEW, IDW 0 and IDW 1 methods, respectively. Clinical studies with the...
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Papers by Koichi Okuda