Yutaka Yamashita

Daiwa House Central Research Laboratory, Edo, Tōkyō, Japan

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Publications (36)61.56 Total impact

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    ABSTRACT: Background: Optical imaging and spectroscopy using near-infrared light have great potential in the assessment of tumor vasculature. We previously measured hemoglobin concentrations in breast cancer using a near-infrared time-resolved spectroscopy system. The purpose of the present study was to evaluate the effect of the chest wall on the measurement of hemoglobin concentrations in normal breast tissue and cancer. Methods: We measured total hemoglobin (tHb) concentration in both cancer and contralateral normal breast using a near-infrared time-resolved spectroscopy system in 24 female patients with breast cancer. Patients were divided into two groups based on menopausal state. The skin-to-chest wall distance was determined using ultrasound images obtained with an ultrasound probe attached to the spectroscopy probe. Results: The apparent tHb concentration of normal breast increased when the skin-to-chest wall distance was less than 20 mm. The tHb concentration in pre-menopausal patients was higher than that in post-menopausal patients. Although the concentration of tHb in cancer tissue was statistically higher than that in normal breast, the contralateral normal breast showed higher tHb concentration than cancer in 9 of 46 datasets. When the curves of tHb concentrations as a function of the skin-to-chest wall distance in normal breast were applied for pre- and post-menopausal patients separately, all the cancer lesions plotted above the curves. Conclusions: The skin-to-chest wall distance affected the measurement of tHb concentration of breast tissue by near-infrared time-resolved spectroscopy. The tHb concentration of breast cancer tissue was more precisely evaluated by considering the skin-to-chest wall distance.
    Breast Cancer 10/2015; DOI:10.1007/s12282-015-0650-7 · 1.59 Impact Factor

  • Cancer Research 05/2015; 75(9 Supplement):P5-01-13-P5-01-13. DOI:10.1158/1538-7445.SABCS14-P5-01-13 · 9.33 Impact Factor
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    ABSTRACT: Near-infrared spectroscopy (NIRS) has been used for noninvasive assessment of oxygenation in living tissue. For muscle measurements by NIRS, the measurement sensitivity to muscle (SM) is strongly influenced by fat thickness (FT). In this study, we investigated the influence of FT and developed a correction curve for SM with an optode distance (3 cm) sufficiently large to probe the muscle. First, we measured the hemoglobin concentration in the forearm (n=36) and thigh (n=6) during arterial occlusion using a time-resolved spectroscopy (TRS) system, and then FT was measured by ultrasound. The correction curve was derived from the ratio of partial mean optical path length of the muscle layer 〈LM〉 to observed mean optical path length 〈L〉. There was good correlation between FT and 〈L〉 at rest, and 〈L〉 could be used to estimate FT. The estimated FT was used to validate the correction curve by measuring the forearm blood flow (FBF) by strain-gauge plethysmography (SGP_FBF) and TRS (TRS_FBF) simultaneously during a reactive hyperemia test with 16 volunteers. The corrected TRS_FBF results were similar to the SGP_FBF results. This is a simple method for sensitivity correction that does not require use of ultrasound.
    Journal of Biomedical Optics 06/2014; 19(6):67005. DOI:10.1117/1.JBO.19.6.067005 · 2.86 Impact Factor
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    ABSTRACT: Using near-infrared time-resolved spectroscopy (TRS), we measured the human head in transmittance mode to obtain the optical properties, tissue oxygenation, and hemodynamics of deep brain tissues in 50 healthy adult volunteers. The right ear canal was irradiated with 3-wavelengths of pulsed light (760, 795, and 835nm), and the photons passing through the human head were collected at the left ear canal. Optical signals with sufficient intensity could be obtained from 46 of the 50 volunteers. By analyzing the temporal profiles based on the photon diffusion theory, we successfully obtained absorption coefficients for each wavelength. The levels of oxygenated hemoglobin (HbO2), deoxygenated hemoglobin (Hb), total hemoglobin (tHb), and tissue oxygen saturation (SO2) were then determined by referring to the hemoglobin spectroscopic data. Compared with the SO2 values for the forehead measurements in reflectance mode, the SO2 values of the transmittance measurements of the human head were approximately 10% lower, and tHb values of the transmittance measurements were always lower than those of the forehead reflectance measurements. Moreover, the level of hemoglobin and the SO2 were strongly correlated between the human head measurements in transmittance mode and the forehead measurements in the reflectance mode, respectively. These results demonstrated a potential application of this TRS system in examining deep brain tissues of humans.
    Proceedings of SPIE - The International Society for Optical Engineering 02/2014; 8928. DOI:10.1117/12.2038689 · 0.20 Impact Factor
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    ABSTRACT: Near-infrared optical imaging targeting the intrinsic contrast of tissue hemoglobin has emerged as a promising approach for visualization of vascularity in cancer research. We evaluated the usefulness of diffuse optical spectroscopy using time-resolved spectroscopic (TRS) measurements for functional imaging of primary breast cancer. Fifty-five consecutive TNM stageI/II patients with histologically proven invasive ductal carcinoma and operable breast tumors (<5 cm) who underwent TRS measurements were enrolled. Thirty (54.5%) patients underwent 18F-fluoro-deoxy-glucose (FDG) positron emission tomography with measurement of maximum tumor uptake. TRS was used to obtain oxyhemoglobin, deoxyhemoglobin, and total hemoglobin (tHb) levels from the lesions, surrounding normal tissue, and contralateral normal tissue. Lesions with tHb levels 20% higher than those present in normal tissue were defined as "hotspots," while others were considered "uniform." The findings in either tumor type were compared with clinicopathological factors. "Hotspot" tumors were significantly larger (P = 0.002) and exhibited significantly more advanced TNM stage (P = 0.01), higher mitotic counts (P = 0.01) and higher levels of FDG uptake (P = 0.0004) compared with "uniform" tumors; however, other pathological variables were not significantly different between the two groups. Optical imaging for determination of tHb levels allowed for measurement of tumor vascularity as a function of proliferation and glucose metabolism, which may be useful for prediction of patient prognosis and potential response to treatment.
    BMC Cancer 10/2013; 13(1):514. DOI:10.1186/1471-2407-13-514 · 3.36 Impact Factor

  • Clinical Neurophysiology 08/2013; 124(8):e23. DOI:10.1016/j.clinph.2013.02.044 · 3.10 Impact Factor
  • Masatsugu Niwayama · Yutaka Yamashita ·
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    ABSTRACT: Although many researchers have attempted to determine the absolute value of tissue oxygenation using near infrared spectroscopy (NIRS): time-resolved spectroscopy, spatially resolved spectroscopy (SRS), phase-modulated spectroscopy, and continuous-wave spectroscopy (CWS), correction methods are still necessary for quantitative measurement. Overlying tissues, such as skulls and subcutaneous adipose tissues, can greatly affect the measurement sensitivity and accuracy. Therefore, analysis of photon migration is important in obtaining accurate absolute measurements. Several researchers have derived equations for the temporal and spatial dependence of diffusely reflected light in a turbid medium. Analytical solutions of diffusion theory are widely used to quantify the optical properties of homogeneous media. Propagation in a two-layered medium using a diffusion theory and Monte Carlo methods are frequently used to simulate photon migration. Various models are also used to simulate actual tissue structure.
    Application of Near Infrared Spectroscopy in Biomedicine, 01/2013: pages 21-35; , ISBN: 978-1-4614-6251-4
  • Yutaka Yamashita · Masatsugu Niwayama ·
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    ABSTRACT: Four major experimental techniques exist in the field of near infrared spectroscopy (NIRS). The simplest one is continuous-wave spectroscopy (CWS) in which a light of constant intensity is injected into tissue, and then the attenuated transmitted/reflected light signal is measured at a distance from the light source. The CWS technique has the limitation of obtaining only changes in optical density. More elaborate approaches such as spatially resolved spectroscopy (SRS), time-resolved spectroscopy (TRS), and phase-modulated spectroscopy (PMS) have certain advantages. The principles of these techniques are described in the chapter.
    Application of Near Infrared Spectroscopy in Biomedicine, 01/2013: pages 1-19; , ISBN: 978-1-4614-6251-4
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    ABSTRACT: We have been developing time-resolved spectroscopy (TRS) systems for breast cancer diagnosis. Its principle is based on the optical properties of the patient’s breast obtained by TRS measurements.
    Biomedical Optics; 04/2012
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    ABSTRACT: To determine the alterations in optical characteristics and cerebral blood oxygenation (CBO) in the frontal lobe during language tasks, we evaluated the changes in mean optical pathlength (MOP) and CBO induced by a verbal fluency task (VFT) in the right and left frontal lobes in normal adults (n = 9, mean age = 29.6 +/- 4.8 years). We employed a newly developed 8-channel time-resolved near-infrared spectroscopy (TRS) instrument. The results demonstrated differences in MOP in the fronto-temporal areas with subject and wavelength; however, there was no significant difference between the right and left sides (p > 0.05). Also, the VFT did not affect the MOP significantly as compared to that before the tasks (p > 0.05). In all of the recording regions, the VFT caused increases in concentration of oxyhemoglobin and total hemoglobin associated with a decrease in deoxyhemoglobin concentration, indicating that these cortical areas were activated by the VFT. However, the mean concentration changes of oxyhemoglobin and total hemoglobin on the left side were larger than those on the right side. In addition, functional MRI demonstrated that the inferior frontal gyrus on the left side was activated in the subjects who exhibited increases in oxyhemoglobin concentration in these areas. These results suggest that TRS may be useful to study language function and to assess hemispheric dominance for language.
    Advances in Experimental Medicine and Biology 01/2010; 662:213-8. DOI:10.1007/978-1-4419-1241-1_30 · 1.96 Impact Factor
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    ABSTRACT: We examined the usefulness of near infrared time-resolved spectroscopy (TRS) for detection of vasospasm in subarachnoid hemorrhage (SAH). We investigated seven aneurysmal SAH patients with poor clinical conditions (WFNS grade V) who underwent endovascular coil embolization. Employing TRS, we measured the oxygen saturation (SO(2)) and baseline hemoglobin concentrations in the cortices. Measurements of TRS and transcranial Doppler sonography (TCD) were performed repeatedly for 14 days after SAH. In four of the seven patients, the SO(2) and hemoglobin concentrations measured in the brain tissue of the middle cerebral artery territory remained stable after SAH. However, in three patients, TRS revealed abrupt decreases in SO(2) and total hemoglobin between 5 and 9 days after SAH. Cerebral angiography performed on the same day revealed severe vasospasms in these patients. Although TCD detected the vasospasm in two of three cases, it failed to do so in one case. TRS could detect vasospasms after SAH by evaluating the cortical blood oxygenation.
    Advances in Experimental Medicine and Biology 01/2010; 662:505-11. DOI:10.1007/978-1-4419-1241-1_73 · 1.96 Impact Factor
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    ABSTRACT: We developed a three-wavelength time-resolved spectroscopy (TRS) system, which allows quantitative measurement of hemodynamics within relatively large living tissue. We clinically evaluated this TRS system by monitoring cerebral circulation during cardiopulmonary bypass surgery. Oxyhemoglobin, deoxyhemoglobin, total hemoglobin and oxygen saturation (SO(2)) were determined by TRS on the left forehead attached with an optode spacing of 4 cm. We also simultaneously monitored jugular venous oxygen saturation (SjvO(2)) and arterial blood hematocrit (Hct) using conventional methods. The validity and usefulness of the TRS system were assessed by comparing parameters obtained with the TRS and conventional methods. Although the changes in SO(2) were lower than those in SjvO(2), SO(2) obtained by TRS paralleled the fluctuations in SjvO(2), and a good correlation between these values was observed. The only exceptions occurred during the perfusion period. Moreover, there was a good correlation between tHb and Hct values (r(2)=0.63). We concluded that time-resolved spectroscopy reflected the conditions of cerebral hemodynamics of patients during surgical operations.
    Journal of Biomedical Optics 11/2007; 12(6):062112. DOI:10.1117/1.2804931 · 2.86 Impact Factor
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    ABSTRACT: To determine the alterations in optical characteristics and cerebral blood oxygenation (CBO) during activation and deactivation, we evaluated the changes in mean optical pathlength (MOP) and CBO induced by a verbal fluency task (VFT) and driving simulation in the right and left prefrontal cortex (PFC), employing a newly developed time-resolved near infrared spectroscopy, which allows quantitative measurements of the evoked-CBO changes by determining the MOP with a sampling time of 1 s. The results demonstrated differences in MOP in the foreheads with the subjects and wavelength; however, there was no significant difference between the right and left foreheads (p > 0.05). Also, both the VFT and driving simulation task did not affect the MOP significantly as compared to that before the tasks (p > 0.05). In the bilateral PFCs, the VFT caused increases of oxyhemoglobin and total hemoglobin associated with a decrease of deoxyhemoglobin, while the driving simulation task caused decreases of oxyhemoglobin and total hemoglobin associated with an increase of deoxyhemoglobin; there were no significant differences in evoked-CBO changes between the right and left PFC. The present results will be useful for quantitative measurement of hemodynamic changes during activation and deactivation in the adults by near infrared spectroscopy.
    Life Sciences 06/2006; 78(23):2734-41. DOI:10.1016/j.lfs.2005.10.045 · 2.70 Impact Factor
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    ABSTRACT: We compared pharmacologically-perturbed hemodynamic parameters (cerebral blood volume; CBV, and flow; CBF) by acetazolamide administration in six healthy human subjects studied with positron emission tomography (PET) and near-infrared (NIR) time-resolved spectroscopy (TRS) simultaneously to investigate whether NIR-TRS could measure in vivo hemodynamics in the brain tissue quantitatively. Simultaneously with the PET measurements, TRS measurements were performed at the forehead with four different optode spacing from 2 cm to 5 cm. Total hemoglobin and oxygen saturation (SO2) measured by TRS significantly increased after administration of acetazolamide at any optode spacing in all subjects. In PET study, CBV and CBF were estimated in the following three volumes of interest (VOIs) determined on magnetic resonance images, VOI1: scalp and skull, VOI2: gray matter region, VOI3: gray and white matter regions. Acetazolamide treatment elevated CBF and CBV significantly in VOI2 and VOI3 but VOI1. TRS-derived CBV was more strongly correlated with PET-derived counterpart in VOI2 and VOI3 when the optode spacing was above 4 cm, although optical signal from cerebral tissue could be caught with any optode spacing. As to increase of the CBV, 4 cm of optode spacing correlated best with VOI2. To support the result of TRS-PET experiment, we also estimated the contribution ratios of intracerebral tissue to observed absorption change based on diffusion theory. The contribution ratios at 4 cm were estimated as follows: 761 nm: 50%, 791 nm: 72%, 836 nm: 70%. These results demonstrated that NIR-TRS with 4 cm of optode spacing could measure cerebral hemodynamic responses optimally and quantitatively.
    NeuroImage 03/2006; 29(3):697-705. DOI:10.1016/j.neuroimage.2005.08.008 · 6.36 Impact Factor
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    ABSTRACT: We report the successful application of reflectance diffuse optical tomography (DOT) using near-infrared light with the new reconstruction algorithm that we developed to the observation of regional hemodynamic changes in the brain under specific mental tasks. Our results reveal the heterogeneous distribution of oxyhemoglobin and deoxyhemoglobin in the brain, showing complementary images of oxyhemoglobin and deoxyhemoglobin changes in certain regions. We conclude that our reflectance DOT has practical potential for human brain mapping, as well as in the diagnostic imaging of brain diseases.
    Japanese Journal of Applied Physics 09/2005; 44(37-41). DOI:10.1143/JJAP.44.L1203 · 1.13 Impact Factor
  • Yukio Ueda · Kazuyoshi Ohta · Yutaka Yamashita ·
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    ABSTRACT: Our research goal is to develop diffuse optical tomography (DOT) capable of quantitative measurement. Information on optical pathlength is essential for reconstructing images with quantitative properties, and we have performed image reconstruction with a simulation model using a time-resolved photon path distribution (time-resolved PPD). The results showed that a DOT image reconstruction algorithm using this PPD is effective in quantifying the absorbers in a scattering medium such as human tissue. This algorithm uses a photon distribution independent of absorption by simply assuming that the measurement object is homogeneous, which means that PPD needs to be calculated only once. Our technique is therefore applicable to short-time imaging of measurement objects for which absorption changes flatness such as that in human tissue.
    Optical Review 06/2005; 12(4):334-337. DOI:10.1007/s10043-005-0334-1 · 0.66 Impact Factor
  • Yutaka Yamashita · D Yamashita · T Yamanaka · T Suzuki · E Ohmae · Y Ueda · M Oda ·
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    ABSTRACT: A near infrared multi-channel time-resolved spectroscopy system has been developed. This system acquires the data with 0.2sec sampling time at 16 points, simultaneously. Absorption change can be determined within 3 % accuracy.
  • Yukio Ueda · Kazuyoshi Ohta · Yutaka Yamashita · Yutaka Tsuchiya ·
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    ABSTRACT: We calculated the photon path distribution (PPD) in a scattering medium based on a theoretical analysis, which utilizes the relationship between the photon intensity and photon pathlength. This PPD is defined by local photon pathlengths for photons having total pathlengths of l between the light input points and detection points. The PPD of photons that consist of the impulse response at time t (= l/c) was calculated for a 2-D model. Precise analysis of photon migration in the scattering medium is essential in order to carry out image reconstruction of diffuse optical tomography (DOT). We show the PPD at time t (the total pathlength l = ct) and demonstrate its effectiveness. Our method for describing photon migration is intuitive and allows finding weight functions in DOT.
    Optical Review 09/2003; 10(5):444-446. DOI:10.1007/s10043-003-0444-6 · 0.66 Impact Factor
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    ABSTRACT: Three-dimensional imaging of three small absorbers embedded in a tissuelike cylindrical solid phantom was conducted by diffusion optical tomography. Each absorber, which was 10 mm in diameter and 10 mm high, was located on the same plane in a phantom, which was 80 mm in diameter and 140 mm high. The optical properties of the phantom were similar to those of the human breast; that is, one absorber had lower absorption and the other two absorbers had higher absorption than that of the phantom. Reemission from the phantom was measured with a multichannel photon counting system. Image reconstruction was performed by our average value method. We were able to distinguish lower and higher absorbers quantitatively. This result shows that our method can diagnose not only the existence of but also a morbid state of breast cancer.
    Applied Optics 01/2002; 40(34):6349-55. DOI:10.1364/AO.40.006349 · 1.78 Impact Factor
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    ABSTRACT: We have developed a three-wavelength (759,797, and 833 nm) time-resolved spectroscopy (TRS) system as a tissue oxygenation monitor employing a time-correlated single photon counting method. This system achieved a high data acquisition rate and system miniaturization maintaining a high sensitivity and time resolution. Our system succeeded in accurately measuring concentrations of oxy-(HbO2) and deoxyhemoglobin (Hb) by means of TRS data observation through studies using a phantom model and living tissue.
    Proceedings of SPIE - The International Society for Optical Engineering 11/2000; 3579. DOI:10.1117/12.356809 · 0.20 Impact Factor