Hiroyuki Sekiguchi

Effects of posture on cardiac autonomic nervous activity in patients with congestive heart failure.

OBJECTIVES We aimed to clarify which recumbent position is preferred by patients with congestive heart failure (CHF) and to evaluate whether cardiac autonomic nervous activity is different among three recumbent positions (supine, left lateral decubitus, right lateral decubitus) in patients with CHF. BACKGROUND It remains unclear whether cardiac autonomic nervous activity is different among three recumbent positions in patients with CHF. METHODS We studied 17 male CHF patients (66+/-7 years) and 17 age- and gender-matched healthy subjects (66+/-7 years). Each subject underwent 24-h ambulatory electrocardiographic monitoring. A channel was used to record the CM5 lead, and another to record the signal of the patients posture with use of a newly developed small-sized detector (3.2 cm x 3.2 cm). By using spectral analysis of heart rate variability, frequency-domain measures were calculated and compared among the three recumbent positions. Normalized high-frequency (HF: 0.15 to 0.40 Hz) power was used as an index of vagal activity and the low frequency (0.04 to 0.15 Hz)/HF power ratio was used as an index of sympathovagal balance. RESULTS In patients with CHF, the time for the right lateral decubitus position was two-fold longer than that for the supine and left lateral decubitus positions. The increased cardiac sympathetic activity and decreased vagal tone in CHF patients were normalized in the right lateral decubitus position. CONCLUSIONS The right lateral decubitus position in patients with CHF may be a self-protecting mechanism of attenuating the imbalance of cardiac autonomic nervous activity.

Effects of posture on sympathetic nervous modulation in patients with chronic heart failure

We investigated which recumbent position is preferred by patients with chronic heart failure (CHF) and whether sympathetic nervous modulation differs in three recumbent positions. We assessed 12 patients with CHF by spectral analysis of heart-rate variability and measurement of plasma norepinephrine concentrations. The right lateral decubitus position was preferred for significantly longer periods than the left lateral decubitus and supine positions. Sympathetic nervous modulation was most attenuated in the right lateral decubitus position. The right lateral decubitus position preferred by patients with CHF may be a self-protective mechanism to control increased sympathetic nervous modulation.

Visualization of tumor-related blood vessels in human breast by photoacoustic imaging system with a hemispherical detector array

Noninvasive measurement of the distribution and oxygenation state of hemoglobin (Hb) inside the tissue is strongly required to analyze the tumor-associated vasculatures. We developed a photoacoustic imaging (PAI) system with a hemispherical-shaped detector array (HDA). Here, we show that PAI system with HDA revealed finer vasculature, more detailed blood-vessel branching structures, and more detailed morphological vessel characteristics compared with MRI by the use of breast shape deformation of MRI to PAI and their fused image. Morphologically abnormal peritumoral blood vessel features, including centripetal photoacoustic signals and disruption or narrowing of vessel signals, were observed and intratumoral signals were detected by PAI in breast cancer tissues as a result of the clinical study of 22 malignant cases. Interestingly, it was also possible to analyze anticancer treatment-driven changes in vascular morphological features and function, such as improvement of intratumoral blood perfusion and relevant changes in intravascular hemoglobin saturation of oxygen. This clinical study indicated that PAI appears to be a promising tool for noninvasive analysis of human blood vessels and may contribute to improve cancer diagnosis.

Circadian variation of cardiac autonomic nervous activity is well preserved in patients with mild to moderate chronic heart failure: effect of patient position

BACKGROUND It remains unclear whether circadian variation (CV) of cardiac autonomic nervous activity (CANA) is preserved in patients with chronic heart failure (CHF) as in healthy subjects. We have demonstrated that CANA in CHF patients is largely affected by patient recumbent position. METHODS We studied eight mild to moderate CHF patients and eight age, sex-matched healthy subjects. Each subject underwent 24-h ambulatory ECG monitoring. One channel was used to record the CM5 lead, and another to record the signal of patient position from a newly developed, small-sized detector. By using spectral analysis of heart rate variability, frequency-domain measures were calculated. Normalized high-frequency (HF: 0.15-0.40 Hz) power was used as an index of vagal activity and the low frequency (LF: 0.04-0.15 Hz)/HF power ratio was used as an index of sympathovagal balance. These indexes in the same recumbent position were compared between night (2:00-4:00 a.m.) and morning (6:00-8:00 a.m.). RESULTS In healthy subjects, a definite CV of CANA was observed in each recumbent position. In patients with CHF, in each position, normalized HF power was lower in the morning than at night, whereas LF/HF was higher in the morning than at night. Thus, CANA in CHF patients is influenced not only by patient position but also by the time of day. CONCLUSION CV of CANA in mild to moderate CHF patients is well preserved when taking patient position into consideration.

Label-free photoacoustic imaging of human palmar vessels: a structural morphological analysis

We analysed the vascular morphology of the palm using a photoacoustic tomography (PAT) instrument with a hemispherical detector array. The three-dimensional (3D) morphology of blood vessels was determined noninvasively. Overall, 12 females and 11 males were recruited as healthy volunteers. Their ages were distributed almost evenly from 22 to 59 years. In all cases, many vascular networks were observed just beneath the skin and were determined to be veins anatomically. To analyse the major arteries, the layer containing the subcutaneous venous network was removed from the image. The analysis focused on the common and proper palmar digital arteries. We used the curvature of these arteries as a parameter to analyse their morphologies. There was no significant difference in the curvature between genders when comparing the subjects as a whole. The blood vessel curvature increased with age. Good agreement was found between the 3D numerical analysis results and the subjective evaluation of the two-dimensional (2D) projection image. The PAT system enabled visualization of the 3D features of blood vessels in the palm and noninvasive analysis of arterial tortuousness.

Quantitative analysis of Iaido proficiency by using motion data

The purpose of this research is to make a quantitative analysis of Iaido (the Japanese art of using the Japanese sword) proficiency with multivariate data analysis. We carried out experiments of motion capture on Kirioroshi (a straight overhead slash) movement of Roppon-me (a sword thrust using two hands) in Iaido. We can analyze the proficiency of an Iaido practitioner by conducting PCA (Principal Components Analysis) and cluster analysis of parameters of body movement. In addition, it is expected that our research will help Iaido practitioners and masters with Iaido training through giving new information on Iaido movements.

Body surface detection method for photoacoustic image data using cloth-simulation technique

Photoacoustic tomography (PAT) is a novel modality that can visualize blood vessels without contrast agents. It clearly shows blood vessels near the body surface. However, these vessels obstruct the observation of deep blood vessels. As the existence range of each vessel is determined by the distance from the body surface, they can be separated if the position of the skin is known. However, skin tissue, which does not contain hemoglobin, does not appear in PAT results, therefore, manual estimation is required. As this task is very labor-intensive, its automation is highly desirable. Therefore, we developed a method to estimate the body surface using the cloth-simulation technique, which is a commonly used method to create computer graphics (CG) animations; however, it has not yet been employed for medical image processing. In cloth simulations, the virtual cloth is represented by a two-dimensional array of mass nodes. The nodes are connected with each other by springs. Once the cloth is released from a position away from the body, each node begins to move downwards under the effect of gravity, spring, and other forces; some of the nodes hit the superficial vessels and stop. The cloth position in the stationary state represents the body surface. The body surface estimation, which required approximately 1 h with the manual method, is automated and it takes only approximately 10 s with the proposed method. The proposed method could facilitate the practical use of PAT.

Photoacoustic imaging system visualizes restoration of peripheral oxygenation in psoriatic lesions

Photoacoustic imaging (PAI) is an emerging technology that enables visualization of vasculatures and pigmented tissue in vivo1 . PAI has been used for the detection of cancers such as melanoma, thyroid cancer and breast cancer in pre-clinical studies2,3 . To date, no study has used PAI to assess a systemic, internal disease. Many systemic diseases such as hypertension and diabetes cause atherosclerosis (a macrovascular disease) and arteriosclerosis (a microvascular disease). While atherosclerosis is readily evaluated by clinical tests such as sonographic study of the common carotid arteries, arteriosclerosis cannot be readily assessed. There is a need for modalities that can evaluate pathological changes in small vasculatures noninvasively. This article is protected by copyright. All rights reserved.

A study of computer-aided diagnosis for pulmonary nodule: comparison between classification accuracies using calculated image features and imaging findings annotated by radiologists

PurposeIn our previous study, we developed a computer-aided diagnosis (CADx) system using imaging findings annotated by radiologists. The system, however, requires radiologists to input many imaging findings. In order to reduce such an interaction of radiologists, we further developed a CADx system using derived imaging findings based on calculated image features, in which the system only requires few user operations. The purpose of this study is to check whether calculated image features (CFT) or derived imaging findings (DFD) can represent information in imaging findings annotated by radiologists (AFD).MethodsWe calculate 2282 image features and derive 39 imaging findings by using information on a nodule position and its type (solid or ground-glass). These image features are categorized into shape features, texture features and imaging findings-specific features. Each imaging finding is derived based on each corresponding classifier using random forest. To check whether CFT or DFD can represent information in AFD, under an assumption that the accuracies of classifiers are the same if information included in input is the same, we constructed classifiers by using various types of information (CTT, DFD and AFD) and compared accuracies on an inferred diagnosis of a nodule. We employ SVM with RBF kernel as classifier to infer a diagnosis name.ResultsAccuracies of classifiers using DFD, CFT, AFD and CFT