N Tamaki

Hokkaido University, Sapporo, Hokkaidō, Japan

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Publications (559)1150.11 Total impact

  • Nagara Tamaki · Kenji Hirata
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    ABSTRACT: Tumor hypoxia is associated with tumor progression and resistance to various treatments. Noninvasive imaging using positron emission tomography (PET) and F-18-labeled fluoromisonidazole (FMISO) was recently introduced in order to define and quantify tumor hypoxia. The FMISO uptake was closely correlated with pimonidazole immunohistochemistry and hypoxia-inducible factor 1 expression in basic studies. Tumor hypoxia in head and neck cancers and other tumors in a clinical setting may also indicate resistance to radiation and/or chemotherapy. Hypoxic imaging may thus play a new and important role for suitable radiation planning, including dose escalation and dose reduction based on the image findings. Such radiation-dose painting based on the findings of hypoxia may require high-performance PET imaging to provide high target-to-background ratio images and an optimal quantitative parameter to define the hypoxic region. A multicenter prospective study using data from a large number of patients is also warranted to test the clinical value of hypoxic imaging.
    No preview · Article · Nov 2015 · International Journal of Clinical Oncology

  • No preview · Article · Nov 2015 · International journal of radiation oncology, biology, physics

  • No preview · Article · Nov 2015 · International journal of radiation oncology, biology, physics
  • Kenji Hirata · Nagara Tamaki

    No preview · Article · Oct 2015 · Journal of Nuclear Medicine

  • No preview · Article · Oct 2015 · International Journal of Oral and Maxillofacial Surgery
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    ABSTRACT: A 55-year-old woman underwent radiosurgery for a left cerebral hemisphere arteriovenous malformation (AVM) and developed radiation-induced necrosis causing a massive edema in the surrounding brain tissues. Despite various therapies, the edema expanded to the ipsilateral hemisphere and induced neurological symptoms. The radiation-induced necrotic lesion was surgically removed 4 years after radiosurgery. While the preoperative FDG PET revealed severe hypometabolism in the left cerebrum, the necrotomy significantly ameliorated the brain edema, glucose metabolism (postoperative FDG PET), and symptoms. This case indicates that radiation necrosis-induced neurological deficits may be associated with brain edema and hypometabolism, which could be reversed by appropriate necrotomy.
    Full-text · Article · Jun 2015
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    ABSTRACT: Cardiovascular diseases (CVDs) are the principal cause of death in the world, (WHO database). Among CVDs, coronary artery diseases (CAD) are the most common diseases which are responsible for more than 38% of deaths. Also, CAD therapeutic strategy, patient based, may vary from basic useful with limited expenses to very complex non useful and very expensive. In Developing countries, such avoidable and non useful expenditures are greatly needed to be saved in order to be allocated for other country priorities. Recently, CAD has started to decline in developed countries thanks to prevention. Nuclear cardiac imaging is an important tool and part of the prevention strategy as well as a discriminate imaging for choosing the appropriate therapy for each patient especially when limited budget is a reality like in developing countries. Medical treatment, and the two primary modalities bypass grafting (CABG) and percutaneous coronary intervention (PCI) are the main pillars of therapeutic strategy of CAD. The local experience has showed that when SPECT MPI is used extensively for CAD assessment, the reduction of the cost of management of CAD is palpable and real. A limited study targeting almost 5500 patients referred for SPECT MPI in order to assist for defining the best therapy for suspected or confirmed CAD. This study has been conducted between 2010 and 2014. Patients with more than 2 vessels diseases were excluded from the study. From 5560 patients, 1752 patients have had a normal SPECT MPI and therefore declared not clearly eligible for revascularization approach. 2050 patients have had a minor to moderate abnormalities and revascularization was discussed but not systematically done. In the rest of 1645 patients with moderate to severe abnormalities revascularization was done in most cases. In developing world, SPECT MPI is an important tool not only for secondary prevention but also for defining appropriate therapeutic strategy.
    Full-text · Conference Paper · May 2015
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    ABSTRACT: Background: Impairment of myocardial fatty acid metabolism assessed by nuclear imaging is associated with increased cardiac mortality for patients undergoing hemodialysis. The reanalysis of beta-methyl- p-iodophenyl pentadecanoic acid (BMIPP) SPECT Analysis for Decreasing Cardiac Events in Hemodialysis Patients (B-SAFE) tried to identify determinants of sudden cardiac death (SCD) for future establishment of prophylactic strategy against SCD. Methods and Results: This study analyzed clinical and scintigraphic data from 677 B-SAFE patients, who had undergone cardiac I-123-BMIPP imaging then had been prospectively followed up, to identify determinants of all-cause mortality. During a 3-year interval, 20 SCDs were observed. SCD patients had a greater C-reactive protein level, more frequently abnormal Q-wave and increased BMIPP abnormality compared to non-SCD patients. There, however, was no significant difference in other clinical, laboratory or hemodialysis parameters between them. Univariate Cox regression analysis identified greater C-reactive protein level (>2.38mg/dl), abnormal Q-wave and greater BMIPP abnormality (summed score>16) as significant prognostic factors for SCD with hazards ratios of 6.83 (95% confidence interval (CI): 1.76–26.47, P=0.005), 17.73 (95%CI: 4.91–63.98, P<0.001) and 10.58 (95%CI, 3.84–29.14, P<0.001), respectively. The patients who had two of the three identified conditions had lower SCD-free rates (log-rank test, P<0.001). Similarly, in multivariate Cox analysis, it showed the maximal hazard ratio of 145.22 (95%CI: 30.34–695.10, P<0.0001) and ROC-AUC of 0.677, when patients had two or all of the SCD risks such as a C-reactive protein level more than 2.38mg/dl, abnormal Q-wave and BMIPP score more than 16. Conclusions: In addition to electrocardiographic abnormality, an increased C-reactive protein level and impaired myocardial fatty acid metabolism are closely and incrementally related to SCD risks in patients undergoing hemodialysis, contributing to appropriate selection of high-risk patients for SCD who could benefit most from a prophylactic approach against SCD.
    No preview · Article · May 2015 · European Heart Journal Cardiovascular Imaging
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    Nagara Tamaki
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    ABSTRACT: A significant progress in positron emission tomography (PET) system has recently been seen which may improve sensitivity, spatial resolution, and noise reduction. Such progress has provided better quality of myocardial perfusion images with lower injected dose, and thus lower radiation to the patient. In addition, better quantification of myocardial blood flow (MBF) and coronary flow reserve (CFR) is expected.1-7Many of new PET cameras have three-dimensional (3D) mode acquisition with time-of-flight (TOF) technology. The system sensitivity in 3D acquisition is much greater than 2D acquisition. On the other hand, the fraction of background activity is also higher in 3D.8 TOF, on the other hand, may significantly increase signal-to-noise ratio by decreasing noise.8 TOF can estimate the arrival time of the 511 keV photons, and therefore, the location of the emission point may be constrained along a line-of-response between the two detector pairs.9,10 In order to perform adequate effects o ...
    Preview · Article · Mar 2015 · Journal of Nuclear Cardiology
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    ABSTRACT: Purpose: The staging of endometrial cancer requires surgery which carries the risk of morbidity. FDG PET/CT combined with anatomical imaging may reduce the number of unnecessary lymphadenectomies by demonstrating the risk of extrapelvic infiltration. The purpose of this study was to optimize FDG PET/CT diagnostic criteria for risk assessment in endometrial cancer after first-line risk triage with MRI. Methods: The study population comprised 37 patients who underwent curative surgery for the treatment of endometrial cancer. First, the risk of extrapelvic infiltration was triaged using MRI. Second, multiple glucose metabolic profiles of the primary lesion were assessed with FDG PET/CT, and these were correlated with the histopathological risk of extrapelvic infiltration including lymphovascular space invasion (LVSI) and high-grade malignancy (grades 2 and 3). The results of histological correlation were used to adjust FDG PET/CT diagnostic criteria. Results: Presurgical assessment using MRI was positive for deep (>50 %) myometrial invasion in 17 patients. The optimal FDG PET/CT diagnostic criteria vary depending on the results of MRI. Specifically, SUVmax (≥16.0) was used to indicate LVSI risk with an overall diagnostic accuracy of 88.2 % in patients with MRI findings showing myometrial invasion. High-grade malignancy did not correlate with any of metabolic profiles in this patient group. In the remaining patients without myometrial invasion, lesion glycolysis (LG) or metabolic volume were better indicators of LVSI than SUVmax with the same diagnostic accuracy of 80.0 %. In addition, LG (≥26.9) predicted high-grade malignancy with an accuracy of 72.2 %. Using the optimized cut-off criteria for LVSI, glucose metabolic profiling of primary lesions correctly predicted lymph node metastasis with an accuracy of 73.0 %, which was comparable with the accuracy of visual assessment for lymph node metastasis using MRI and FDG PET/CT. Conclusion: FDG PET/CT diagnostic criteria may need adjustment based on the anatomical information provided by MRI. The optimized criteria can predict the risk of pathology-proven LVSI correctly in 83.8 % of patients before surgery, and thus would improve presurgical treatment planning.
    No preview · Article · Dec 2014 · European journal of nuclear medicine and molecular imaging
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    ABSTRACT: Although histological diagnosis is indispensable in treating primary central nervous system lymphoma (PCNSL), we sometimes face an intractable situation in which tissue can be obtained only from a deep-seated brain lesion. In place of a histological diagnosis, the diagnostic adequacy of the combined use of 18 F-FDG PET and corticosteroid administration for PCNSL located in a deep-seated brain structure is reported. Patients with a deep-seated tumor were treated as having PCNSL without histological confirmation, based on the following criteria: (1) there was no evidence of systemic malignancy; (2) the tumor showed an extremely high FDG uptake relative to normal gray matter on pretreatment 18 F-FDG PET; (3) the tumor decreased in size 1 week after diagnostic therapy by corticosteroid administration on contrast-enhanced T1-weighted magnetic resonance imaging (MRI). FDG uptake of the lesion was evaluated by the maximum of standardized uptake values (SUVmax) and tumor-to-normal ratio of the SUV (T/N ratio). The extent of the tumor reduction was calculated by volumetric analysis for the treatment response to corticosteroid administration. Ten patients (4 males and 6 females) matched these criteria. On pretreatment 18 F-FDG PET, mean SUVmax in the tumor was 24.8 (8.75-60.75), and mean T/N ratio was 3.24 (2.17-5.12). The extent of tumor volume reduction was shown to be 21 to 68 % 1 week after diagnostic therapy by corticosteroids. Mean total dose and duration of corticosteroids were 719 mg as prednisolone and 6.5 days, respectively. Nine patients achieved complete response and one patient achieved partial response on MRI after standard treatment for PCNSL with high-dose methotrexate and/or whole-brain irradiation. Although the value of biopsy is universal, combining 18 F-FDG PET and corticosteroid administration is an important alternative method that may lead to the diagnosis of deep-seated PCNSLs in cases with intractable histopathological confirmations.
    No preview · Article · Dec 2014 · Acta Neurochirurgica

  • No preview · Conference Paper · Oct 2014
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    ABSTRACT: Background: Surgical debridement is often required to treat spinal infections. Successful surgery requires accurate localization of the active infections, however, current imaging technique still requires surgeons' experience to narrow the surgical fields to achieve less invasive procedures. Purpose: To investigate the use of F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) for successful surgical planning. Material and methods: Nine patients with suspected spinal infection underwent magnetic resonance imaging (MRI) and FDG-PET/CT before surgery to locate active foci of infections. The spinal structures were divided into seven compartments at each intervertebral disc level for a total of 315 compartments investigated. The same classification system was used to design operating fields for histological correlation. Results: FDG-PET/CT diagnosed fewer compartments as active infection (34 compartments, 10.8%) than MRI (62 compartments, 19.7%, P = 0.002). Surgical exploration was performed in 49 compartments, and demonstrated active infection in 25 compartments. The sensitivity / specificity of FDG-PET/CT was 100% / 79%, respectively, which was superior to those of MRI, 76% / 42%. Foci of active infection showed hypermetabolic activity with a SUVmax of 7.1 ± 2.6 (range, 3.0-12.7). Receiver operating characteristic (ROC) analysis indicated an optimal threshold for active spinal infection at a SUVmax of 4.2, corresponding to a sensitivity of 90.3% and specificity of 91.2%. Conclusion: FDG-PET/CT demonstrated limited areas of abnormality allowing accurate delineation, and is thus useful to narrow the surgical fields. Since overall diagnostic accuracy of FDG-PET/CT was superior to that of MRI, FDG-PET/CT is a useful technique to narrow the surgical field for successful less invasive surgery.
    No preview · Article · Jul 2014 · Acta Radiologica
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    ABSTRACT: Purpose Hypoxia, a prognostic factor in many types of cancer, can be detected by 18F-fluoromisonidazole (FMISO) positron emission tomography (PET). It is unclear whether hypoxia reflects the response to chemotherapy in patients with oral squamous cell carcinoma (OSCC). The correlations of FMISO-PET and FDG-PET with histological response to preoperative chemotherapy were therefore assessed in patients with OSCC. Methods This study enrolled 22 patients with OSCC undergoing preoperative chemotherapy. The T-stages were T2 in 6 patients, T3 in 3, and T4a in 13, and the N-stages were N0 in 14 patients, N1 in 3, and N2 in 5. Each patient was evaluated by both FMISO-PET and FDG-PET before surgery, and the maximum standardized uptake value (SUVmax) of FDG- and FMISO-PET and tumor-muscle ratio (TMR) of FMISO-PET were measured. The threshold for the hypoxic volume based on TMR was set at 1.25. The histological response to preoperative chemotherapy was evaluated using operative materials. Results FMISO-PET and FDG-PET detected uptake by primary OSCCs in 15 (68 %) and 21 (95 %) patients, respectively, and median SUVmaxs of FMISO- and FDG-PET in the primary site were 2.0 (range, 1.3–3.5) and 16.0 (range, 1.0–32.2), respectively. The median of FMISO TMR was 1.5 (range, 0.99–2.96). There were five cases whose FMISO TMR was less than 1.25. Histological evaluation showed good response to preoperative chemotherapy in 7 patients (32 %) and poor response in 15 (68 %). Good response was significantly more prevalent in patients with negative than positive FMISO uptake (P
    Full-text · Article · May 2014 · European journal of nuclear medicine and molecular imaging

  • No preview · Article · Oct 2013 · International Journal of Radiation OncologyBiologyPhysics
  • M. Yi · H. Tao · M. Kohanawa · S. Zhao · Y. Kuge · N. Tamaki
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    ABSTRACT: Introduction The health drink Pairogen mainly consists of ferrous ferric chloride (FFC) water that appears to perform multiple biological functions by regulating intracellular redox reactions in living organisms (1). With respect to its contribution to host defense, FFC water reportedly protects plant against fungal infection (2). However, little is known regarding the capability of FFC water and Pairogen to regulate the defense mechanisms in animals or humans in order to respond properly to pathogenic organisms. Herein, we investigated whether Pairogen regulates inflammatory response to Rhodococcus aurantiacus (R. aurantiacus) infection in mice. Methods We assessed survival, organ bacterial load, and inflammation (cytokine production and histomorphological changes) in Pairogen-treated mice (F0) and first-generation mice (F1) following infection. Cytokine response to heat-killed R. aurantiacus was further explored in the peritoneal macrophages of Pairogen-treated F1 mice. Results Longitudinal ingestion of Pairogen improved survival of infected mice in a concentration-dependent manner. Rapid elimination of bacteria from the organs (such as livers and spleens), accompanied by decreased production of tumor necrosis factor-alpha and interleukin-6 and elevated release of interleukin-10, was observed in F0 mice treated with 10-fold-diluted Pairogen. Histological studies also exhibited a significant reduction in granuloma number and size as well as amelioration in the oxidative status in mouse livers at day 14 following infection. The effects of Pairogen were further pronounced in F1 mice treated with 10-fold-diluted Pairogen. Stimulating the peritoneal macrophages from these mice with heat-killed R. aurantiacus induced the production of three cytokines similar to those detected in vivo, whereas gene expression of these cytokines was down-regulated, suggesting an inhibitory role of Pairogen in cytokine expression and the mutual antagonistic relationship among the cytokines. Conclusion The present study reveals that longitudinal ingestion of Pairogen improves survival, accelerates bacterial clearance and suppresses the over-expression of inflammation-related cytokines by regulating cellular redox reactions, and consequently results in depression of granulomatous inflammation in R. aurantiacus-infected mice. Moreover, these effects of Pairogen were enhanced in their offspring when they continued to ingest Pairogen. Pairogen is thought to be a useful redox regulator that contributes to the regulation of inflammatory and immune responses. It may also be expected to improve the quality of human life by heightening the defense functions against infection.
    No preview · Article · Sep 2012 · Cytokine
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    ABSTRACT: After myocardial infarction (MI), left ventricular (LV) remodelling is observed in noninfarcted LV myocardium. LV remodelling is closely associated with systolic heart failure. Since myocardial dysfunction is related to the downregulation of cardiac postsynaptic beta-adrenergic receptors (β-AR), we hypothesized that a reduction in β-AR density may be manifested in the remote noninfarcted region and such reduction may be related to myocardial systolic dysfunction. Accordingly, we assessed β-AR density with a focus on the remote noninfarcted region. Cardiac PET was performed in 15 patients with a prior MI and 10 age-matched healthy controls using (11)C-CGP 12177, a radioligand for β-receptors. The maximum number of available specific (11)C-CGP 12177 binding sites per gram of tissue was calculated in regions of interest using an established graphical method. LV regional systolic function was assessed based on peak systolic myocardial strain on the LV wall in the longitudinal direction using two-dimensional ultrasound speckle tracking imaging. LV volumes and LV ejection fraction (EF) were also measured. The LV end-diastolic volume index was significantly larger in patients than in controls (67.8 ± 16.9 vs. 49.1 ± 12.3 ml/m(2), p < 0.01). Significant differences in β-AR density were observed among three areas: the apical area in controls (where the lowest β-AR density was observed), the remote noninfarcted region of patients and LVEF ≥ 55 %, and the remote noninfarcted region of patients and LVEF <55 % (5.8 ± 2.1 vs. 4.2 ± 0.7 vs. 3.3 ± 0.7 pmol/ml, p < 0.01, ANOVA). Peak systolic myocardial strain was significantly reduced in the remote noninfarcted LV wall in patients with a prior anterior wall MI compared with that in the corresponding wall in controls (-15.5 ± 2.5 vs. -20.1 ± 2.2 %, p < 0.001). A similar finding was also observed in patients with a prior inferior wall MI. In the remote noninfarcted region in patients, β-AR downregulation was observed, which was related to deterioration of local myocardial systolic function.
    Full-text · Article · May 2012 · European Journal of Nuclear Medicine
  • K. Sakurai · T. Shiga · T. Kurita · Y. Takeda · N. Tamaki · T. Koyama
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    ABSTRACT: Simple partial status epilepticus occurs more rarely than other forms of status epilepticus. This report describes two patients with temporal lobe epilepsy who experienced simple partial status epilepticus. Results show that basal ganglia and the mid-brain are activated during simple partial status epilepticus by blood perfusion single-photon emission computed tomography (SPECT) and subtraction ictal SPECT coregistered to MRI (SISCOM).
    No preview · Article · Jan 2012 · Neurology Asia
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    ABSTRACT: Targeting improved spatial resolution, a three-dimensional positron-emission-tomography (PET) scanner employing CdTe semiconductor detectors and using depth-of-interaction (DOI) information was developed, and its physical performance was evaluated. This PET scanner is the first to use semiconductor detectors dedicated to the human brain and head-and-neck region. Imaging performance of the scanner used for <sup>18</sup>F -fluorodeoxy glucose (FDG) scans of phantoms and human brains was evaluated. The gantry of the scanner has a 35.0-cm-diameter patient port, the trans-axial field of view (FOV) is 31.0 cm, and the axial FOV is 24.6 cm. The energy resolution averaged over all detector channels and timing resolution were 4.1% and 6.8 ns (each in FWHM), respectively. Spatial resolution measured at the center of FOV was 2.3-mm FWHM-which is one of the best resolutions achieved by human PET scanners. Noise-equivalent count ratio (NEC2R) has a maximum in the energy window of 390 to 540 keV and is 36 kcps/Bq/cm<sup>3</sup> at 3.7 kBq/cm<sup>3</sup> . The sensitivity of the system according to NEMA 1994 was 25.9 cps/Bq/cm<sup>3</sup>. Scatter fraction of the scanner is 37% for the energy window of 390 to 540 keV and 23% for 450 to 540 keV. Images of a hot-rod phantom and images of brain glucose metabolism show that the structural accuracy of the images obtained with the semiconductor PET scanner is higher than that possible with a conventional Bismuth Germanium Oxide (BGO) PET scanner. In addition, the developed scanner permits better delineation of the head-and-neck cancer. These results show that the semiconductor PET scanner will play a major role in the upcoming era of personalized medicine.
    No preview · Article · Nov 2011 · IEEE Transactions on Nuclear Science

  • No preview · Article · Oct 2011 · Fuel and Energy Abstracts

Publication Stats

7k Citations
1,150.11 Total Impact Points


  • 1995-2015
    • Hokkaido University
      • • Department of Nuclear Medicine
      • • Graduate School of Medicine
      • • Department of Medicine II
      Sapporo, Hokkaidō, Japan
  • 2004
    • Health Sciences University of Hokkaido
      Tōbetsu, Hokkaidō, Japan
  • 2001
    • Kyoto Prefectural University of Medicine
      Kioto, Kyōto, Japan
  • 1996-2001
    • Hokkaido University Hospital
      • Division of Nuclear Medicine
      Sapporo, Hokkaidō, Japan
  • 1982-2001
    • Kyoto University
      • • Department of Diagnostic Imaging and Nuclear Medicine
      • • Department of Cardiovascular Medicine
      Kyoto, Kyoto-fu, Japan
  • 2000
    • Research Institute for Brain and Blood Vessels-Akita
      Akita, Akita, Japan
  • 1976-2000
    • Kobe University
      • • Division of Neurosurgery
      • • Department of Medicine
      Kōbe, Hyōgo, Japan
  • 1993
    • The University of Tokyo
      • Department of Radiology
      白山, Tōkyō, Japan
  • 1992
    • Mitsubishi Kyoto Hospital
      Kioto, Kyōto, Japan
  • 1985-1991
    • Massachusetts General Hospital
      • Department of Radiology
      Boston, Massachusetts, United States
  • 1988
    • Social Insurance Chukyo Hospital
      Nagoya, Aichi, Japan
    • University of Massachusetts Boston
      Boston, Massachusetts, United States