Biomedical subjects

Takahito Nakajima

Publications and source records attributed to Takahito Nakajima.

11 recordsLinked to original sources

PubMed2006

The relativistic complete active-space second-order perturbation theory with the four-component Dirac Hamiltonian.

The relativistic complete active-space second-order perturbation theory (CASPT2) is developed for the four-component relativistic Hamiltonian. The present method can describe the near-degenerated and dissociated electronic states of molecules involving atoms of heavy elements. The present approach is less expensive than the relativistic multireference configuration interaction method. The ground and low-lying excited states of TlH, Tl(2), and PtH molecules are calculated with the Dirac-Coulomb (DC) CASPT2 method and their spectroscopic constants are obtained. These spectroscopic constants are compared with experimental findings and previous theoretical work. For all the molecules, the spectroscopic constants of DC-CASPT2 show good agreement with the experimental or previous theoretical spectroscopic constants. The present theory provides accurate descriptions of bonding or dissociation states and of ground and excited states in a well-balanced way.

Journal Article↗

PubMed2006

Theoretical study of valence photoelectron spectra of Re(CO)5X (X=Cl, Br, and I): a spin-orbit DK3 symmetry-adapted cluster/symmetry-adapted cluster-configuration interaction study.

The valence photoelectron spectra of Re(CO)(5)X (X=Cl, Br, and I) are studied theoretically using symmetry-adapted cluster (SAC)/SAC-configuration interaction (SAC-CI) theory. The relativistic effects are included by the third-order Douglas-Kroll (DK3) method, and the spin-orbit coupling is also considered. Both electron correlation and relativistic effects are significant in assigning the valence photoelectron spectra of Re(CO)(5)X (X=Cl, Br, and I). DK3-SAC/SAC-CI provides values for the relative peak positions in a reasonable agreement with the observed photoelectron spectra. The sequence of ionization energies for Re(CO)(5)Cl, Re(CO)(5)Br, and Re(CO)(5)I are calculated as e(')[a(1)(Cl)]>e(')[e(Re+Cl)] approximately e(")[e(Re+Cl)]>e(")[b(2)(Re)]>e(')[e(Re-Cl)]>e(")[e(Re-Cl)], e(')[a(1)(Br)]>e(')[e(Re+Br)]>e(")[e(Re+Br)+b(2)(Re)]>e(")[b(2)(Re)+e(Re+Br)]>e(')[e(Re-Br)]>e(")[e(Re-Br)], and e(')[e(Re+I)+a(1)(I)]>e(")[b(2)(Re)+e(Re+I)] approximately e(')[a(1)(I)+e(Re+I)]>e(")[e(Re+I)+b(2)(Re)]>e(')[e(Re-I)]>e(")[e(Re-I)], respectively. These assignments are quite new and different from previous assignments.

Journal Article↗

PubMed2006

A dual-level approach to density-functional theory.

An efficient approximate scheme for density-functional theory (DFT) calculations, which eliminates the time-consuming self-consistent-field (SCF) procedure, is proposed using a dual-level DFT approach. In this approach, dual levels of basis sets and exchange-correlation functionals are adopted. The dual-level DFT approach is based on the idea that the total electron density in the ground state can be represented in terms of the density evaluated using the low-quality basis set and the low-cost exchange-correlation functional. Since the SCF procedure is avoided in the total energy evaluation, the dual-level DFT approach drastically reduces the computational cost. The applications of several dual-level DFT calculations to molecular systems show that our approach is more efficient than the self-consistent DFT approach with a moderate accuracy.

Journal Article↗

PubMed2006

Computed tomography-guided transpulmonary radiofrequency ablation for hepatocellular carcinoma located in hepatic dome.

AIM: To determine the feasibility of performing computed tomography (CT)-guided transpulmonary radiofrequency ablation (RFA) for hepatocellular carcinoma (HCC) located in the hepatic dome. METHODS: A total of seven patients with HCC comprising seven nodules located in the hepatic dome were treated from April 2004 to December 2004. CT-guided transpulmonary RFA was performed using a cool-tip type electrode (Radionics Company) based on a standardized energy protocol. All tumors located in the hepatic dome were not detectable by the usual ultrasound (US) methods. The lesion diameters ranged from 15 to 27 mm. RESULTS: RFA was technically feasible in all the patients. The puncture procedure was performed twice or less and the total average performance time was 40.6 min. Local tumor control was achieved in all the patients. The necrosis diameter ranged from 25 to 35 mm. The mean follow-up period was 9.6 (7-14 mo) mo. There was no local recurrence at the follow-up points. Pneumothorax requiring pleural drainage was the main complication, which was observed in two of the seven patients (28.6%). However, it improved with chest drainage tube, and the tube could be removed within 2-3 d. No other major complications were observed. CONCLUSION: CT-guided puncture is useful for the treatment of tumors located in the hepatic dome which are hardly detectable by US, even though pneumothorax sometimes may occur as a complication. In the cases with adhesion in the pleura for which artificial pleural effusion methods are not appropriate, CT-guided RFA is thus considered to be an alternative treatment for HCC located in the hepatic dome.

Aged↗

PubMed2005

A new, accurate and conventional five-point method for quantitative evaluation of ascites using plain computed tomography in cancer patients.

BACKGROUND: To assess the exact response of the malignant ascites to the treatment, the objective measurement of the volume of ascites is essential. We have developed a simple method to measure the volume of ascites by using standard abdomino-pelvic computed tomography (CT). The aim of the study is to validate the accuracy of the measurements by comparing them with the standard volume calculation by using 3D-CT. METHODS: Twelve consecutive patients with cancer who had measurable ascites underwent 15 helical CT examinations. On conventional CT images, the thickness of ascites in centimeters was measured in three planes such as the bilateral subphrenic space (A and B), the bilateral paracolic space (C and D) and the pre-bladder space (E), and the average thickness: (A + B + C + D + E)/5 was then multiplied by the area of standard abdominal cavity in the anterior projection, that was assumed to be 1000 cm(2), to yield the volume of ascites: (A + B + C + D + E) x 200 (ml). The volume of ascites was compared with the exact volume, that was obtained from 3D-CT with the volume rendering method. RESULTS: The volume of ascites measured by the present method and the volume rendering method ranged from 140 to 4040 ml and from 86 to 4279 ml, respectively. The correlation was statistically significant with a correlation coefficient of 0.956 (P < 0.01) using the Spearman's rank correlation. In 13 examinations with the exact volume > or =300 ml, the average ratio of the absolute difference in the volume was 12.9 +/- 13.9% as compared with 62.8 and 162.0% in two examinations with the exact volume < 300 ml. CONCLUSION: The preliminary study indicated that the present five-point method using a conventional CT was accurate in patients with the volume of ascites > or =300 ml. Because this procedure is simple and easy to perform, it should be feasible in many hospitals for the follow-up of ascites after treatment.

Adult↗

PubMed2005

Normal cranial nerves in the cavernous sinuses: contrast-enhanced three-dimensional constructive interference in the steady state MR imaging.

BACKGROUND AND PURPOSE: Three-dimensional (3D) constructive interference in steady state (CISS) MR imaging is useful for demonstrating cranial nerves (CNs) in the cistern. The purpose of this study was to evaluate normal CNs III, IV, V1, V2, and VI in the cavernous sinuses by using contrast-enhanced, three-dimensional (3D), Fourier transformation CISS MR imaging. METHODS: In 76 normal cavernous sinuses from 38 patients, detectability of CNs III-VI in the bilateral cavernous sinuses was evaluated by using contrast-enhanced 3D CISS MR imaging. In 40 cavernous sinuses from 20 patients, contrast-enhanced 3D CISS and contrast-enhanced T1-weighted MR imaging were compared for the detectability of these CNs. RESULTS: Each CN was separately demonstrated, and in 11 patients (29%), all CNs in the cavernous sinuses were identified on contrast-enhanced 3D CISS MR imaging. The images depicted the intracavernous segments of CNs III, IV, V1, V2, and VI in 76 (100%), 46 (61%), 70 (92%), 67 (88%), and 73 (96%) of the 76 sinuses, respectively. In comparison of imaging techniques, contrast-enhanced 3D CISS MR imaging had a detection rate significantly higher than that of enhanced T1-weighting imaging (P < .05) in all CNs except for CN III, which was detected in 100% of cases with both techniques. CONCLUSION: Contrast-enhanced 3D CISS MR imaging provides clear images of each CN in the cavernous segment. This useful method may contribute to the diagnosis of diseases involving the cavernous sinuses, such as Tolosa-Hunt syndrome.

Adolescent↗

PubMed2005

Clinical background and its relation to results of percutaneous needle biopsy of suspected bone metastasis under guidance with CT fluoroscopy.

PURPOSE: To investigate the clinical background of needle biopsy of suspected bone metastasis under guidance with CT fluoroscopy. PATIENTS AND METHODS: During a 3-year period (from April 2000 to March 2003), 103 needle biopsies on 101 lesions of 90 patients were performed for pathological evaluation of suspected bone metastasis. The clinical course of these patients prior to biopsy and its relation to the biopsy results were retrospectively reviewed. RESULTS: Sixty-two patients (69% of total cases) were referred for biopsy from orthopedic surgeons, and 51 of these patients consulted orthopedic surgeons on the initial presentation. Malignancy was pathologically proved in 47 (76%) of the 62 orthopedic patients, and in 19 (68%) of the 28 patients referred from other clinicians. Thirteen (21%) of the orthopedic patients had a history of malignancy, while 22 (78%) of the non-orthopedic patients were cancer patients. Metastasis was pathologically proved in 23 (66%) of the 35 patients with a history of malignancy, while malignancy was pathologically proved in 43 (78%) of the 55 patients without known malignancy. Diagnostic accuracy of the needle bone biopsy was 96%, and its complication rate was 0.7%. CONCLUSION: In the era of CT fluoroscopy, needle biopsy for suspected bone metastasis was most frequently requested for the patients who consulted orthopedic surgeons for the occurrence of local bone pain as the initial symptom of unknown malignancy. Frequency of malignancy proved by the biopsy in those patients was as high as that in the cancer patients referred from other clinicians.

Adolescent↗

PubMed2004

Pseudospectral approach to relativistic molecular theory.

The efficient relativistic Dirac-Hartree-Fock (DHF) and Dirac-Kohn-Sham (DKS) methods are proposed by an application of the pseudospectral (PS) approach. The present PS-DHF/DKS method is a relativistic extension of the PS-HF/KS method of Friesner, though we aim at higher numerical accuracy by elimination of superfluous arbitrariness. The relativistic PS-DHF/DKS method is implemented into our REL4D programs. Several PS applications to molecular systems show that the relativistic PS-DHF/DKS approach is more efficient than the traditional approach without a loss of accuracy. The present PS-DKS method successfully assigns and predicts the photoelectron spectra of hexacarbonyl complexes of tungsten and seaborgium theoretically.

Journal Article↗

PubMed2004

Third-order Douglas-Kroll relativistic coupled-cluster theory through connected single, double, triple, and quadruple substitutions: applications to diatomic and triatomic hydrides.

Coupled-cluster methods including through and up to the connected single, double, triple, and quadruple substitutions have been derived and implemented automatically for sequential and parallel executions by an algebraic and symbolic manipulation program TCE (TENSOR CONTRACTION ENGINE) for use in conjunction with a one-component third-order Douglas-Kroll approximation for relativistic corrections. A combination of the converging electron-correlation methods, the accurate relativistic reference wave functions, and the use of systematic basis sets tailored to the relativistic approximation has been shown to predict the experimental singlet-triplet separations within 0.02 eV (0.5 kcal/mol) for five triatomic hydrides (CH2, NH2+, SiH2, PH2+, and AsH2+), the experimental bond lengths (re or r0) within 0.002 angstroms, rotational constants (Be or B0) within 0.02 cm(-1), vibration-rotation constants (alphae) within 0.01 cm(-1), centrifugal distortion constants (De) within 2%, harmonic vibration frequencies (omegae) within 8 cm(-1) (0.4%), anharmonic vibrational constants (xomegae) within 2 cm(-1), and dissociation energies (D0(0)) within 0.02 eV (0.4 kcal/mol) for twenty diatomic hydrides (BH, CH, NH, OH, FH, AlH, SiH, PH, SH, ClH, GaH, GeH, AsH, SeH, BrH, InH, SnH, SbH, TeH, and IH) containing main-group elements across the second through fifth rows of the periodic table. In these calculations, spin-orbit effects on dissociation energies, which were assumed to be additive, were estimated from the measured spin-orbit coupling constants of atoms and diatomic molecules, and an electronic energy in the complete-basis-set, complete-electron-correlation limit has been extrapolated in two ways to verify the robustness of the results: One assuming Gaussian-exponential dependence of total energies on double through quadruple zeta basis sets and the other assuming n(-3) dependence of correlation energies on double through quintuple zeta basis sets.

Journal Article↗

PubMed2004

Noninvasive determination of regional myocardial perfusion with first-pass magnetic resonance (MR) imaging.

RATIONALE AND OBJECTIVES: To develop a method to provide absolute values of regional myocardial perfusion by means of color maps, and to determine myocardial perfusion reserve using magnetic resonance imaging during the first pass of gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA). MATERIALS AND METHODS: The study population consisted of five patients with hypertrophic cardiomyopathy, two with dilated cardiomyopathy, four with coronary artery disease, and one with normal coronary arteries who presented with mildly abnormal electrocardiogram findings. For each heartbeat, six continuous slices were acquired during the first pass of Gd-DTPA (0.05 mmol/kg body weight) before and during adenosine triphosphate (ATP) **stress using an electrocardiogram-triggered fast low-angle shot (FLASH) sequence on a 1.5-T magnetic resonance unit. Myocardial perfusion images were created and displayed by means of a color scale. The parameters were calculated pixel by pixel, using the upslope method. Myocardial perfusion reserve was then calculated, as the quotient of myocardial perfusion during ATP stress and perfusion before ATP stress. RESULTS: Myocardial perfusion during ATP stress in patients with normal coronary arteries (n = 1) or after successful percutaneous coronary intervention (n = 2) was increased compared with that before ATP stress. However, the patients with coronary artery disease (n = 2) failed to show increased myocardial perfusion. The patients with hypertrophic cardiomyopathy showed increased myocardial perfusion during ATP stress, although two with dilated cardiomyopathy did not. CONCLUSION: Our new technique can provide absolute values of regional myocardial perfusion by means of color maps, and has potential for widespread use for evaluation of ischemic and other types of heart disease.

Adenosine Triphosphate↗

PubMed2002

Relativistic electronic structure theory.

The theoretical and technical foundations are presented for the efficient relativistic electronic structure theories to treat heavy-atomic molecular systems. This review contains two surveys of four-component and two-component quasi-relativistic approaches. First, we review our highly efficient computational scheme for four-component relativistic ab initio molecular orbital (MO) methods over generally contracted spherical harmonic Gaussian-type spinors (GTSs). Illustrative calculations, which are performed with a new four-component relativistic ab initio molecular orbital program package REL4D, clearly show the efficiency of our computational scheme by the Dirac-Hartree-Fock (DHF) and Dirac-Hartree-Fock (DKS) methods. Next, in the two-component quasi-relativistic framework, two relativistic Hamiltonians, RESC and higher order Douglas-Kroll (DK) Hamiltonians, are introduced, and several illustrative calculations are shown. Numerical results for several systems show that good accuracy can be obtained with our third-order DK (DK3) Hamiltonian.

Journal Article↗