Usability of the lateral decubitus position on four-dimensional ultra-low-dose computed tomography for the detection of localized pleural adhesion in the pulmonary apical region.

BACKGROUND: Localized pleural adhesion (LPA) evaluation in the apical region is difficult even with four-dimensional ultra-low-dose computed tomography (4D-ULDCT) in the supine position due to smaller pleural movements. PURPOSE: To assess usability of 4D-ULDCT in the lateral decubitus (LD) position for LPA detection in the apical region. MATERIAL AND METHODS: Forty-seven patients underwent 4D-ULDCT of a single respiration cycle with 16-cm coverage of body axis in supine and LD positions with the affected lung uppermost. Intraoperative thoracoscopic findings confirmed LPA presence. A pleural point and a corresponding point on costal outer edge were placed in identical axial planes at end-inspiration. Pleuro-chest wall distance between two points (PCD) was calculated at each respiratory phase. In the affected lung, average change in amount of PCD (PCDACA) was compared between patients with and without LPA in total and two sub-groups (non-COPD and COPD, non-emphysematous and emphysematous patients) in supine and non-dependent (ND) LD positions. Receiver operating characteristic (ROC) curve analysis was performed to determine optimal thresholds in PCDACA for differentiating patients with LPA from those without. RESULTS: In COPD/emphysematous patients and total population, PCDACA with LPA was smaller than in those without in the supine and NDLD positions for overall, lateral, and dorsal regions. For the lateral region in COPD patients, area under ROC curve (AUC) increased from supine (0.64) to NDLD position (0.81). For the dorsal region in emphysematous patients, AUC increased from supine (0.76) to NDLD position (0.96). CONCLUSION: 4D-ULDCT in LD position may be useful for LPA detection in apical regions for COPD and/or emphysematous patients.

Correlation between musculoskeletal structure of the hand and primate locomotion: Morphometric and mechanical analysis in prehension using the cross- and triple-ratios.

Biometric ratios of the relative length of the rays in the hand have been analyzed between primate species in the light of their hand function or phylogeny. However, how relative lengths among phalanges are mechanically linked to the grasping function of primates with different locomotor behaviors remains unclear. To clarify this, we calculated cross and triple-ratios, which are related to the torque distribution, and the torque generation mode at different joint angles using the lengths of the phalanges and metacarpal bones in 52 primates belonging to 25 species. The torque exerted on the finger joint and traction force of the flexor tendons necessary for a cylindrical grip and a suspensory hand posture were calculated using the moment arm of flexor tendons measured on magnetic resonance images, and were compared among Hylobates spp., Ateles sp., and Papio hamadryas. Finally, the torques calculated from the model were validated by a mechanical study detecting the force exerted on the phalanx by pulling the digital flexor muscles during suspension in these three species. Canonical discriminant analysis of cross and triple-ratios classified primates almost in accordance with their current classification based on locomotor behavior. The traction force was markedly reduced with flexion of the MCP joint parallel to the torque in brachiating primates; this was notably lower in the terrestrial quadrupedal primates than in the arboreal primates at mild flexion. Our mechanical study supported these features in the torque and traction force generation efficiencies. Our results suggest that suspensory or terrestrial quadrupedal primates have hand structures that can exert more torque at a suspensory posture, or palmigrade and digitigrade locomotion, respectively. Furthermore, our study suggests availability of the cross and triple-ratios as one of the indicators to estimate the hand function from the skeletal structure.

Peripheral bronchial luminal conspicuity on dynamic-ventilation computed tomography: association with radiation doses and temporal resolution by using an ex vivo porcine lung phantom.

BACKGROUND: It is still unclear which image reconstruction algorithm is appropriate for peripheral bronchial luminal conspicuity (PBLC) on dynamic-ventilation computed tomography (DVCT). PURPOSE: To assess the influence of radiation doses and temporal resolution (TR) on the association between movement velocity (MV) and PBLC on DVCT. MATERIAL AND METHODS: An ex vivo porcine lung phantom with simulated respiratory movement was scanned by 320-row CT at 240 mA and 10 mA. Peak and dip CT density and luminal area adjusted by values at end-inspiration (CTDpeak and CTDdip, luminal area ratio [LAR]) for PBLC and MVs were measured and visual scores (VS) were obtained at 12 measurement points on 13 frame images obtained at half and full reconstructions (TR 340 and 190 ms) during expiration. Size-specific dose estimate (SSDE) was applied to presume radiation dose. VS, CTDpeak, CTDdip, LAR, and their cross-correlation coefficients with MV (CCC) were compared among four methods with combinations of two reconstruction algorithms and two doses. RESULTS: The dose at 10 mA was presumed as 26 mA by SSDE for standard proportion adults. VS, CTDdip, CTDpeak, and LAR with half reconstruction at 10 mA (2.52 ± 0.59, 1.016 ± 0.221, 0.948 ± 0.103, and 0.990 ± 0.527) were similar to those at 240 mA except for VS, and different from those with full reconstruction at both doses (2.24 ± 0.85, 0.830 ± 0.209, 0.986 ± 0.065, and 1.012 ± 0.438 at 240 mA) (P < 0.05). CCC for CTDdip with half reconstruction (-0.024 ± 0.552) at 10 mA was higher compared with full reconstruction (-0.503 ± 0.291) (P < 0.05). CONCLUSION: PBLC with half reconstruction at 10 mA was comparable to that at 240 mA and better than those with full reconstruction on DVCT.

Continuous quantitative measurement of the main bronchial dimensions and lung density in the lateral position by four-dimensional dynamic-ventilation CT in smokers and COPD patients.

PURPOSE: The purpose of this study was to measure changes in lung density and airway dimension in smokers in the lateral position using four-dimensional dynamic-ventilation computed tomography (CT) during free breathing and to evaluate their correlations with spirometric values. MATERIALS AND METHODS: Preoperative pleural adhesion assessments included dynamic-ventilation CT of 42 smokers (including 22 patients with COPD) in the lateral position, with the unoperated lung beneath (dependent lung). The scanned lungs' mean lung density (MLD) and the bilateral main bronchi's luminal areas (Ai) were measured automatically (13-18 continuous image frames, 0.35 seconds/frame). Calculations included cross-correlation coefficients (CCCs) between the MLD and Ai time curves, and correlations between the quantitative measurements and spirometric values were evaluated by using Spearman's rank coefficient. RESULTS: The ΔMLD1.05 (from the peak inspiration frame to the third expiratory frame, 1.05 seconds later) in the nondependent lung negatively correlated with FEV1/FVC (r=-0.417, P<0.01), suggesting that large expiratory movement of the nondependent lung would compensate limited expiratory movement of the dependent lung due to COPD. The ΔAi1.05 negatively correlated with the FEV1/FVC predicted in both the lungs (r=-0.465 and -0.311, P<0.05), suggesting that early expiratory collapses of the main bronchi indicate severe airflow limitation. The CCC correlated with FEV1/FVC in the dependent lung (r=-0.474, P<0.01), suggesting that reduced synchrony between the proximal airway and lung occurs in patients with severe airflow limitation. CONCLUSION: In COPD patients, in the lateral position, the following abnormal dynamic-ventilation CT findings are associated with airflow limitation: enhanced complementary ventilation in the nondependent lung, early expiratory airway collapses, and reduced synchrony between airway and lung movements in the dependent lung.

Sub-solid nodule detectability in seven observers of seventy-nine clinical cases: comparison between ultra-low-dose chest digital tomosynthesis with iterative reconstruction and chest radiography by receiver-operating characteristics analysis.

PURPOSE: To compare sub-solid nodules detectability (SSND) between ultra-low-dose chest digital tomosynthesis (ULD-CDT) with/without iterative reconstruction (IR) and chest radiography (CR) by using low-dose computed tomography (LDCT) as the standard of reference (SOR). MATERIALS AND METHODS: Institutional Review Board approved this study and written informed consent was obtained. In a single visit, 79 subjects underwent ULD-CDT at 120 kV and 10 mA, CR and LDCT (effective dose: 0.171, 0.117 and 3.52 mSv, respectively). Sixty-three coronal images were reconstructed using CDT with/without IR. SOR as to SSN presence was determined based on LDCT images. Seven radiologists recorded SSN presence and locations by continuously-distributed rating. Receiver-operating characteristic (ROC) analysis was used to compare SSND of ULD-CDT with/without IR and CR, in total and subgroups classified by nodular longest diameter (LD) (> or < 9 mm) and mean CT attenuation value (CTAV) (> or < -600 Hounsfield of Unit (HU)). Detection sensitivity (DS) was compared among 4 groups classified by combination of the identical thresholds: nodular LD (9 mm) and mean CTAV (-600 HU) in each of ULD-CDT with/without IR and CR with Friedman and Wilcoxon signed rank test. RESULTS: SSND for total 105 SSNs as well as larger SSNs with nodular LD of 9 mm or more at ULD-CDT with IR was higher than either that at ULD-CDT without IR or CR, as the areas under the ROC curve were 0.66 ± 0.02, 0.59 ± 0.01 and 0.52 ± 0.01, respectively (p < 0.05). DS at ULD-CDT with IR was 69.5 ± 10.8% in groups with larger (LD > 9 mm) and more-attenuated (>-600 HU) SSNs, and higher than in the other 3 groups (p < 0.05). CONCLUSION: ULD-CDT with IR demonstrated better SSND than that without IR or CR, with increased DS for larger and more-attenuated SSNs compared with the remaining ones.

Preoperative assessment of pleural adhesion by Four-Dimensional Ultra-Low-Dose Computed Tomography (4D-ULDCT) with Adaptive Iterative Dose Reduction using Three-Dimensional processing (AIDR-3D).

PURPOSE: To assess the feasibility of Four-Dimensional Ultra-Low-Dose Computed Tomography (4D-ULDCT) for distinguishing pleural aspects with localized pleural adhesion (LPA) from those without. METHODS: Twenty-seven patients underwent 4D-ULDCT during a single respiration with a 16cm-coverage of the body axis. The presence and severity of LPA was confirmed by their intraoperative thoracoscopic findings. A point on the pleura and a corresponding point on the outer edge of the costal bone were placed in identical axial planes at end-inspiration. The distance of the two points (PCD), traced by automatic tracking functions respectively, was calculated at each respiratory phase. The maximal and average change amounts in PCD (PCDMCA and PCDACA) were compared among 110 measurement points (MPs) without LPA, 16MPs with mild LPA and 10MPs with severe LPA in upper lung field cranial to the bronchial bifurcation (ULF), and 150MPs without LPA, 17MPs with mild LPA and 9MPs with severe LPA in lower lung field caudal to the bronchial bifurcation (LLF) using the Mann-Whitney U test. RESULTS: In the LLF, PCDACA as well as PCDMCA demonstrated a significant difference among non-LPA, mild LPA and severe LPA (18.1±9.2, 12.3±6.2 and 5.0±3.3mm) (p<0.05). Also in the ULF, PCDACA showed a significant difference among three conditions (9.2±5.5, 5.7±2.8 and 2.2±0.4mm, respectively) (p<0.05), whereas PCDMCA for mild LPA was similar to that for non-LPA (12.3±5.9 and 17.5±11.0mm). CONCLUSIONS: Four D-ULDCT could be a useful non-invasive preoperative assessment modality for the detection of the presence or severity of LPA.

Maternal undernutrition during early pregnancy inhibits postnatal growth of the tibia in the female offspring of rats by alteration of chondrogenesis.

Epidemiological research has suggested that birth weights are correlated with adult leg lengths. However, the relationship between prenatal undernutrition (UN) and postnatal leg growth remains controversial. We investigated the effects of UN during early pregnancy on postnatal hindlimb growth and determined whether early embryonic malnutrition affects the functions of postnatal chondrocytes in rats. Undernourished Wistar dams were fed 40% of the daily intake of rats in the control groups from gestational days 5.5-11.5, and femurs, tibias, and trunks or spinal columns were morphologically measured at birth and at 16 weeks of age in control and undernourished offspring of both sexes. We evaluated cell proliferation and differentiation of cultured chondrocytes derived from neonatal tibias of female offspring and determined chondrocyte-related gene expression levels in neonatal epiphysis and embryonic limb buds. Tibial lengths of undernourished female, but not male, offspring were longer at birth and shorter at 16 weeks of age (p < .05) compared with those of control rats. In chondrocyte culture studies, stimulating effects of IGF-1 on cell proliferation (p < .01) were significantly decreased and levels of type II collagen were lower in female undernourished offspring (p < .05). These phenomena were accompanied by decreased expression levels of Col2a1 and Igf1r and increased expression levels of Fgfr3 (p < .05), which might be attributable to the decreased expression of specificity protein 1 (p < .05), a key transactivator of Col2a1 and Igf1r. In conclusion, UN stress during early pregnancy reduces postnatal tibial growth in female offspring by altering the function of chondrocytes, likely reflecting altered expression of gene transactivators.

Data set for renal sinus fat volume and visceral adipose tissue volume on computed tomography.

Renal sinus fat is partially characteristic of peri-vascular adipose tissue, however, RSF volume (RSFV) is associated with visceral adipose tissue (VATV). Therefore, the ratio of RSFV to VATV (RSFV/VATV ratio) can distinguish the importance of RSF as an extension of VAT versus its perivascular effects. We assessed the association of RSFV/VATV ratio with coronary artery calcification score (CACS) in 189 patients with suspected coronary artery disease. RSFV of the right kidney and VATV were quantified by using image data of unenhanced abdominal CT. CACS were measured on unenhanced ECG-gated CT images. This article contains data on explanatory scheme of how to measure RSFV on unenhanced abdominal CT, CT indication and exclusion criteria of study population, sex-adjusted association between RSFV with risk factors of coronary vascular diseases and metabolic indices, multivariate linear regression analysis with CACS as the dependent variable in the total study population. The data are supplemental to our original research article describing detailed association between RSFV/VATV ratio and CACS including sub-groups analyses classified by the age of 70 "Renal sinus fat volume on computed tomography in middle-aged patients at risk for cardiovascular disease and its association with coronary artery calcification" Murakami et al. [1].

Renal sinus fat volume on computed tomography in middle-aged patients at risk for cardiovascular disease and its association with coronary artery calcification.

OBJECTIVE: Renal sinus fat (RSF) behaves as one of the perivascular fats, however RSF volume (RSFV) is considerably affected by visceral adipose tissue volume (VTAV). The ratio of RSFV to VATV (RSFV/VATV ratio) can be an index of regional perivascular fat accumulation corrected for the influence of VATV. The aim of this study was to investigate the relation between RSFV/VATV ratio and coronary artery calcium (CAC) in patients with suspected coronary artery disease. METHODS: One hundred and eighty-nine patients (mean age 66.7 ± 10.2; 72% men) underwent ECG-gated cardiac computed tomography (CT) and unenhanced abdominal CT. CAC score (CACS) was assessed using axial CT images. RSFV was measured by partially manipulated segmentation of the right kidney. VATV was automatically quantified in the upper abdomen. Logistic and correlation analyses were performed to examine the correlations between CAC, RSFV/VATV ratio, and risk factors of cardiovascular diseases in total and subgroups classified by the patients' age. RESULTS: Log-transformed RSFV/VATV ratio was associated with CAC presence in 112 middle-aged patients less than 69 years of age as well as total. This association remained significant after multivariate adjustment only in the middle-aged patients (OR 15.9, 95% CI 1.15-218.8). In total, RSFV/VATV ratio (r = 0.228, p = 0.002) and age (r = 0.316, p < 0.001) correlated with CACS on univariate analyses, but only age correlated on multivariate analyses. RSFV/VATV ratio correlated with CACS in the middle-aged patients (r = 0.418, p < 0.001), as well as on multivariate analyses. CONCLUSIONS: We demonstrated that RSFV/VATV could be an independent risk indicator of CAC in the middle-aged patients.

Evaluation of the quality of CT images acquired with the single energy metal artifact reduction (SEMAR) algorithm in patients with hip and dental prostheses and aneurysm embolization coils.

PURPOSE: We compared the quality of the images acquired with single energy metal artifact reduction (SEMAR) on CT scans of three different human body areas. MATERIALS AND METHODS: Our institutional review board approved the study protocol. CT studies of 58 patients (hip prosthesis, n = 20; iliac artery aneurysm embolization, n = 20; dental prosthesis, n = 18) were retrospectively reconstructed using interactive reconstruction (IR) and IR plus SEMAR. Two radiologists independently evaluated the images for the reduction of metal artifacts at three sites, i.e., 0-1, 1-5, and 5-10 cm from their edges, and recorded their findings on a 100-mm-long line that corresponded to the Likert scale and ranged from 0 (invisible) to 100 mm (clearly visible). The standard deviation in Hounsfield units was used as the noise assessment tool. Statistical analysis was performed with the t test and the Wilcoxon signed-rank test. RESULTS: The image quality of scans of hip prostheses and metal embolization coils was significantly improved when SEMAR was used (p < 0.05). On scans of dental prostheses, SEMAR did not contribute significantly, especially in the area 1 cm from the edge of the implant. CONCLUSION: Visual subjective evaluation showed that SEMAR improved the image quality.

320-detector-row computed tomography arteriography using CO2 gas to detect malignant liver tumors.

PURPOSE: We present the initial steps for 320-detector-row computed tomography arteriography using CO2 gas (320-MDCT CO2 arteriography) to detect the vascular area of malignant liver tumors. MATERIAL AND METHODS: This study was approved by the Ethics Committee of our institution. Written prior informed consent was obtained from all patients. We studied six patients with primary and metastatic liver tumors (n = 26) and allergic reactions to iodinated contrast media or a tendency for renal failure. CO2 was injected at 1 ml/sec (volume 8 ml) into the common hepatic artery and a CT scan was acquired 12 seconds after the start of injection. The detection of the vascular area of the tumor or of intratumor air was evaluated with respect to the relationship between the size and location of the tumors. Cramer's V statistic was performed to explore the relationship (p < 0.05). RESULTS: The vascular area was detected in 17 of the 26 tumors (65.4%). There was a correlation between the detection of the adjacent vascular area on CTA images acquired with the use of CO2 and the tumor site observed on previously-acquired MRI or CT images. CONCLUSION: 320-MDCT CO2 arteriography with microcatheters may be useful for the detection of the vascular area.

Negatively charged superparamagnetic iron oxide nanoparticles: a new blood-pooling magnetic resonance contrast agent.

PURPOSE: Our purpose was to investigate the utility of superparamagnetic iron-oxide nanoparticles (SPIO) as a blood-pooling contrast agent at magnetic resonance imaging (MRI). MATERIALS AND METHODS: We studied four contrast agents: carboxymethyl-diethylaminoethyl dextran magnetite SPIO (CMEADM-S, diameter 54 nm), negatively charged CMEADM ultrasmall SPIO (CMEADM-U, 32 nm), alkali-treated dextran magnetite SPIO (ATDM-S, 55 nm), and ATDM ultrasmall SPIO (ATDM-U, 28 nm) carrying a neutral charge. Each contrast agent (80 µmol/kg) was injected intraperitoneally into apolipoprotein E (apoE) mice and the tissue iron concentration was measured 30-, 60-, 180-, and 300-min later by nuclear MR. For MR angiographic (MRA) evaluation, we injected the agents into the auricular vein of four groups of 15 rabbits. Immediately and 30-, 60-, 180-, and 300-min later, three rabbits from each group were subjected to MRI. The organ/background signal ratio (SR) was calculated. Statistical analyses were performed with Tukey's honestly significant difference (HSD) test. RESULTS: At 60 and 180 min, blood-iron concentration of CMEADM-U was significantly different from other contrast agents. In the abdominal aorta and inferior vena cava, SR of CMEADM-U was higher at 180 and 300 min than of the other contrast agents. In the thoracic aorta, there was no difference in SR at 300 min between CMEADM-U and CMEADM-S. CONCLUSION: Negatively charged SPIO nanoparticles may be useful as a blood-pooling contrast agent.

Quantitative assessment of arterial stiffness by multiphase analysis in retrospectively electrocardiogram-gated multidetector row computed tomography: comparison between patients under chronic hemodialysis and age-matched controls.

PURPOSE: To determine the feasibility of assessment of arterial stiffness with multiphase analysis of data sets of retrospectively electrocardiogram (ECG)-gated multidetector row computed tomography (MDCT) coronary angiography by comparing wall stiffness of the descending aorta between patients under chronic hemodialysis and age-matched controls undergoing imaging for by-pass graft. MATERIALS AND METHODS: We retrospectively assessed 33 patients composed of 10 hemodialysis patients and 23 age-matched control subjects, who underwent MDCT to evaluate the coronary arterial lesions and pulse wave velocity (PWV) measurement. Scan data were reconstructed at 25 phases between 0% and 96% of the R-R intervals with an increment of 4%. Pixel-based measurements of arterial dimensions were performed at 1 cross-section of the descending aorta in a transaxial plane including the aortic valve at its widest. Aortic distensibility (AD) was calculated as follows: AD = (maximal dimension -- minimal dimension)/minimal dimension x pulse pressure. Comparison in the AD was performed between the hemodialysis patients and control subjects. Correlation between the AD and PWV were assessed separately in the patients under hemodialysis and age-matched controls. RESULTS: AD was significantly smaller in patients under hemodialysis than in age-matched controls. The square of PWV correlated better with the inverse of the AD in the control subjects compared to patients on hemodialysis. CONCLUSION: Multiphase analysis in ECG-gated MDCT enables us to assess stiffness of the descending aorta objectively and noninvasively.

Detection of mediastinal and hilar lymph nodes by 16-row MDCT: is contrast material needed?

PURPOSE: To retrospectively evaluate whether contrast administration is necessary in the detection of mediastinal and hilar lymph nodes when thin slice axial and coronal MDCT images are used. MATERIALS AND METHOD: This study was approved by our Institutional Review Board, informed consent was not required. Thirty-five patients who needed a chest CT (0.75 mm x 16) for various reasons were included. Four different image sets were reconstructed for each patient: non-enhanced axial (N-Ax), non-enhanced coronal MPR (N-Co), enhanced axial (E-Ax) and enhanced coronal MPR (E-Co). All the images were 1mm thick and interval. Two board-certified chest radiologists independently evaluated whether a lymph node with a short diameter, larger than 5mm, existed in each nodal station of the mediastinum and hilum. Two different board-certified chest radiologists assessed all four image sets together and established a reference standard by consensus. Interobserver agreement between the two readers was assessed by kappa statistics. Accuracy was calculated on each image set and compared to each other by McNemar's test. RESULTS: A total of 211 nodal stations, including 113 mediastinal and 98 hilar, were defined to be present and this was the reference standard. Except for N-Ax, the kappa values were within moderate to substantial (0.53-0.81). The accuracy for hilar nodes detection was significantly higher for the contrast enhanced images both in the axial (p<0.001) and coronal (p<0.01) data sets. The addition of contrast material did not significantly increase accuracy for the detection of mediastinal nodes (axial: p=0.542, coronal p=0.727). CONCLUSION: Contrast administration is recommended in the detection of hilar lymph nodes both on axial and MPR views, however, for assessment of mediastinal lymph nodes its contribution is low.

Resolution of pulmonary multiplanar reconstruction images from 0.5-mm theoretical isotropic data: a fundamental study using an inflated and fixed lung specimen.

The aim of the present study was to define the resolution of multiplanar reconstruction (MPR) of the lung from "theoretical isotropic data." Using inflated and fixed lung specimens of the pig placed in the chest wall phantom, 0.5-mm isotropic data were obtained with 2 different helical pitches: 1:7 (high-quality mode) or 1:13, (high-speed mode), and 2 different tube currents: 250 mAs (high-tube-current mode) or 100 mAs (low-tube-current mode), with or without overlapping reconstruction. MPRs were created from these axial data. The diameter of the smallest visible pulmonary artery and bronchi of these CT images were measured on the corresponding slices of the specimen. The high-speed and low-tube-current mode significantly degraded the image quality due to increased noise. The smallest visible pulmonary artery and bronchus resolved on MPRs from axial-spiral data with 0.5-mm collimation were approximately 100 micrometer and 1,000 micrometer in diameter, respectively. In conclusion, helical pitch and tube current influence the resolution of MPR of the lung.

Multidetector-row computed tomography coronary angiography: optimization of image reconstruction phase according to the heart rate.

BACKGROUND: To optimize the image reconstruction phase of multidetector-row computed tomography (MDCT) coronary angiography according to the heart rate is crucial. METHODS AND RESULTS: Scan data were reconstructed for 10 different phases in 58 sequential patients who underwent 8-row cardiac MDCT. The obtained images were scored and compared in terms of motion artifacts and visibility of the vessels, and moreover, ECG record-based evaluations were added for clarification of the temporal relationships among these 10 phases. In the cases with lower heart rates (<65 beats/min), the best quality images were obtained when the end of the image reconstruction phase was positioned at the peak of the P wave. In some cases with higher heart rates (>65 beats/min), they were obtained in the late systolic period. CONCLUSION: As the heart rate increased, the optimal image reconstruction phase changed from mid diastole to late systole. However, it is recommended to try to decrease the heart rate of patients before data acquisition.