Superconductivity in thin films of boron-doped carbon nanotubes.

Superconductivity in carbon nanotubes (CNTs) is attracting considerable attention. However, its correlation with carrier doping has not been reported. We report on the Meissner effect found in thin films consisting of assembled boron (B)-doped single-walled CNTs (B-SWNTs). We find that only B-SWNT films consisting of low boron concentration leads to evident Meissner effect with Tc=12 K and also that a highly homogeneous ensemble of the B-SWNTs is crucial. The first-principles electronic-structure study of the B-SWNTs strongly supports these results.

Epitope analysis of myeloperoxidase-specific antineutrophil cytoplasmic autoantibodies (MPO-ANCA) in childhood onset Graves' disease treated with propylthiouracil.

AIM: This study aimed to elucidate the relationship between epitope profiles and clinical manifestations of patients with myeloperoxidase antineutrophil cytoplasmic autoantibodies-(MPO-ANCA) positive childhood onset Graves' disease treated with propylthiouracil (PTU). METHODS: Sixteen patients were studied. The patients were grouped into ten without clinical vasculitis and nephritis (non-vasculitis group) and six with biopsy-proven pauci-immune necrotizing crescentic glomerulonephritis (vasculitis group). Epitope analysis was performed on serum samples by an enzyme-linked immunosorbent assay (ELISA) using a panel of recombinant deletion mutants of MPO. RESULTS: The high frequency sites were region upstream of Met341 (Ha region) near the N-terminus of the heavy chain, and regions downstream of Gly598 (Hf and Hg regions) near the C-terminus. Most patients in the non-vasculitis group had polyclonal MPO-ANCA recognizing both the above linear sites and other epitope sites of the heavy chain of MPO. Only one of ten patients in the non-vasculitis group, and four of six patients in the vasculitis group had MPO-ANCA recognizing only the linear sites of the heavy chain of the MPO molecule (Ha, Hf and/or Hg). Of the four patients in the vasculitis group, two had nephritis, like rapidly progressive glomerulonephritis and one had alveolar hemorrhage. CONCLUSION: These findings suggest that most patients with childhood onset Graves' disease treated with PTU who manifest no vasculitis have polyclonal MPO-ANCA recognizing both the linear and other epitope sites of the heavy chain of MPO. However, some patients who develop nephritis have MPO-ANCA recognizing only the linear sites of the heavy chain of MPO. This clonality of MPO-ANCA may be a risk factor that induces clinical vasculitis and nephritis in patients treated with PTU. Therefore, patients exposed to PTU should be monitored for MPO-ANCA level and epitopes.

Phantom studies for estimation of defect size on cardiac (18)F SPECT and PET: implications for myocardial viability assessment.

UNLABELLED: SPECT with (18)F-FDG has emerged as an alternative to dedicated PET for the assessment of myocardial viability. However, whether FDG SPECT can reliably quantify the extent of viable and scarred myocardium is uncertain. The aim of this study was to investigate whether SPECT with an (18)F-labeled agent would provide information on defect size similar to that provided by dedicated PET. METHODS: Imaging was performed using an elliptic cylinder chest phantom with simulated bone, lung, mediastinum, liver, and heart. (18)F was administered into the myocardium, mediastinum, right and left ventricular cavities, and liver. Plastic inserts (n = 11) ranging in size from 2% to 60% of the myocardium were used to simulate transmural myocardial infarctions. The chest phantom was imaged with a dedicated PET camera and with a double-head SPECT camera equipped with ultra-high-energy collimators. Both SPECT and PET data were analyzed using a semiquantitative polar map approach. Defects were quantified using various cutoff thresholds ranging from 30% to 80% of peak activity and were expressed as a percentage of the left ventricular myocardium. Defect size as measured by SPECT or PET was compared with true defect size. RESULTS: The measured SPECT defect size was highly variable depending on the cutoff used, whereas PET defect size was relatively constant over the range of cutoffs tested. The mean absolute difference between measured and true defect sizes was minimal at a cutoff of 50% of peak activity for both SPECT (3.3% +/- 3.3%) and PET (2.7% +/- 2.5%). For this threshold, both SPECT and PET measurements showed an excellent correlation with true defect size (r = 0.98 for SPECT and 0.99 for PET). The correlation between SPECT and PET measurements was also excellent (r = 0.99; P < 0.01). CONCLUSION: If an appropriate threshold is used to define a defect, SPECT with an (18)F-labeled agent can accurately measure defect size similarly to the manner of PET.

[Dual isotope SPECT with 99mTc and 123I using four-energy-window (FEW) method].

We devised "four-energy-window" (FEW) method which permits simultaneous acquisition for dual isotope single photon emission tomography (SPECT) studies using 99mTc and 123I of which photopeak is in close vicinity to each other. This acquisition method requires a total of four energy windows: two main windows for 99mTc (126-143 keV) and 123I (156-175 keV), respectively, and two 5% sub-windows which are set below the 99mTc window and above the 123I window, respectively. Two virtual windows (5%) are additionally set above the 99mTc and below the 123I window, respectively, to apply the triple-energy-window (TEW) method for the scatter correction. A phantom study demonstrated that photocounts from the two radionuclides could be completely separated from each other and that SPECT images obtained had preferable property for quantitative analysis. This method was applied to clinical, dual-radionuclide myocardial studies using 99mTc-MIBI and 123I-BMIPP, and was found to provide excellent images each tracer.

[A new approach to eliminate background count from gated blood pool image (iterative constant subtraction method). Part 1: Principle and technique].

It is important for obtaining a left ventricular volume curve and ejection fraction from a multigated blood pool image (MGBP image) to accurately subtract the background (BG) from the image. We devised a new method of accurately subtracting the BG with good reproducibility. This method (tentatively called the ICS method) is as follows. An image, on which n times (n = 0, 1, 2, 3,..., N-1) an adequately low constant (k) is subtracted from the MGBP image at every pixel of the image matrix, is prepared. When n equals 0, constant is not subtracted from the image, therefore it is original MGBP image. Then the original (n = 0) and constant (nk: n = 1, 2, 3,..., N-1) subtraction MGBP images were prepared. The constant was defined as about 5% of the maximum pixel count in the end-diastole of the left ventricle. Rough region of interest (ROI) were set at the left ventricle on these MGBP images, and time activity curves (TACs, left ventricular volume curves) on each image were prepared. These N kinds of curves are shifted in parallel for normalization in the first frame (end-diastole). The first frame count on the original MGBP image is normalized. As a result, TACs obtained by inadequate subtraction in which subtraction of the constant does not reach the BG count, overlap completely, while TACs obtained by subtraction over the BG gradually separate from the overlapping curves. The MGBP image including a curve located in the border between the overlapping curve and the separated curve is regarded as the image accurately subtracting the BG, and the constant of subtraction (nk) as the BG count for each pixel. The border is obtained by analyzing changes in count of the end-systolic frame of each TAC normalized. The ICS method provides computer software that is performed automatically within a short time by setting a rough ROI at the left ventricle on the end-diastolic MGBP image.

Clothing microclimate temperatures during thermal comfort in boys, young and older men.

To examine the effects of age-related differences in thermoregulatory function on the clothing microclimate temperature (Tm) and Tm fluctuations while maintaining thermal comfort in daily life, 5 boys (group B, 10-11 years), 5 young men (group Y, 20-21 years) and 5 older men (group O, 60-65 years) volunteered to take part in this study. The subjects were asked to maintain thermal comfort as closely as possible in their daily lives. Tm (temperatures between the skin surface and the innermost garment) at four sites (chest, back, upper arm, and thigh), skin temperature on the chest (Tchest) and ambient temperature (Ta) were measured over a period of 8-12 h from morning to evening on one day in each of the seasons, spring, summer, autumn, and winter. Records of ability to maintain thermal comfort and of adjustment of their clothes were kept by each subject. Ta during periods of thermal comfort did not differ among the groups in any of the seasons. In group Y, Tm was significantly lower at the thigh than at the other sites in spring, autumn, and winter (P < 0.05) and fluctuations (CV) of Tm were significantly larger at the thigh than at other sites in autumn and winter (P < 0.05). Similar tendencies were observed for Tm and CV of Tm in group B. However, Tm and CV of Tm in group O did not differ by site except for the autumn Tm. Group O had a smaller CV at the thigh in winter (P < 0.05), compared to groups B and Y, suggesting a smaller regional difference in Tm fluctuation in group O. Group O adjusted their clothes even on the lower limbs (together with upper body) in order to maintain thermal comfort in accordance with changes in Ta, while groups B and Y did so only on their upper bodies. These results suggest that compared to boys and young men, lower thermoregulatory function in older men may affect Tm and CV of Tm as a result of clothing on lower limbs being adjusted differently in order to maintain thermal comfort.

[Effect of scatter correction on quantification of myocardial SPECT and application to dual-energy acquisition using triple-energy window method].

Triple-energy window (TEW) method is a simple and practical approach for correcting Compton scatter in single-photon emission tracer studies. The fraction of scatter correction, with a point source or 30 ml-syringe placed under the camera, was measured by the TEW method. The scatter fraction was 55% for 201Tl, 29% for 99mTc, 57% for 123I. Composite energy spectra were generated and separated by the TEW method. Combination of 99mTc and 201Tl was separated well, and 201Tl and 123I were separated within an error of 10%; whereas asymmetric photopeak energy window was necessary for separating 123I and 99mTc. By applying this method to myocardial SPECT study, the effect of scatter elimination was investigated in each myocardial wall by polar may and profile curve analysis. The effect of scatter was higher in the septum and the inferior wall. The count ratio relative to the anterior wall including scatter was 9% higher in 123I, 7-8% higher in 99mTc and 6% higher in 201Tl. Apparent count loss after scatter correction was 30% for 123I, 13% for 99mTc and 38% for 201Tl. Image contrast, as defined myocardium-to-left ventricular cavity count ratio, improved by scatter correction. Since the influence of Compton scatter was significant in cardiac planar and SPECT studies; the degree of scatter fraction should be kept in mind both in quantification and visual interpretation.

High-resolution cardiac SPET study using fanbeam collimators in infants.

High-resolution three-headed single photon emission computed tomography (SPET) equipped with fan-beam collimators was applied to myocardial perfusion imaging in infants aged from 1 to 11 months (n = 5). A tabletop designed specifically for infants was fixed on the SPET couch to reduce the radius of camera rotation to 13.2 cm. Significant improvement in resolution was achieved with the fan-beam collimators compared to parallel-hole high-resolution collimators. With the administration of approximately 37 MBq (26-44 MBq) 201Tl, 5 min acquisition time was possible for SPET imaging, which provided good image quality in all patients. Thus, a smaller administration dose is possible within a practical short acquisition time. High-resolution fan-beam SPET imaging can be a routine diagnostic method for heart disease in newborn babies and infants.

Dynamic acquisition with a three-headed SPECT system: application to technetium 99m-SQ30217 myocardial imaging.

A method for SPECT data acquisition, "continuous repetitive rotation acquisition," was developed with a high-sensitivity three-headed SPECT system. The method was applied to the dynamic imaging of 99mTc-SQ30217, a new myocardial imaging agent. After acquisition and reconstruction of SPECT data every minute, projection images at arbitrary intervals were used for tomographic reconstruction to determine the best timing of SPECT imaging in 99mTc-SQ30217. Based on a comparison of several possible acquisition intervals, SPECT data acquisition within 9 min after injection is recommended because of high myocardial uptake (myocardium-to-lung ratio, 2.83 +/- 0.42 (mean +/- s.e.m.) at 3-6 min) and relatively low hepatic uptake (myocardium-to-liver ratio, 0.85 +/- 0.13 at 3-6 min). The rate constant of the clearance of 99mTc-SQ30217 from the myocardium obtained by SPECT was: k1 = 0.249 +/- 0.050 per min (average half-life = 2.8 min) and k2 = 0.012 +/- 0.004/min (average half-life = 58 min). The continuous repetitive rotation acquisition SPECT study appears useful for imaging SQ30217 with its rapidly changing myocardial distribution.

[A three-headed SPECT system with high resolution and high sensitivity: application to myocardial imaging].

A three-headed single-photon emission computed tomography (SPECT) system was developed, and the fundamental SPECT performance and clinical applications were investigated. The full width at half maximum (FWHM) of the SPECT system is 10.8 mm at the center of rotation with a radius of 20 cm. In clinical applications, 201Tl myocardial images with the three-headed system demonstrated a distincter and thinner myocardium compared to those with the dual-headed system. The right ventricular wall was observed even in patients without right ventricular overload. Owing to both the increased sensitivity and resolution, the three-headed system has high performance capability in clinical use such as ECG-gating and dynamic studies.