[en] Purpose: To compare the efficacy of low-dose and standard-dose computed tomography (CT) for the diagnosis of ureteral stones. Material and Methods: Unenhanced helical CT was performed with both a standard dose (260 mAs, pitch 1.5) and a low dose (50 mAs, pitch 1.5) in 121 patients suspected of having acute renal colic. The two studies were prospectively and independently interpreted for the presence and location of ureteral stones, abnormalities unrelated to stone disease, identification of secondary signs, i.e. hydronephrosis and perinephric stranding, and tissue rim sign. The standard-dose CT images were interpreted by one reviewer and the low-dose CT images independently by two reviewers unaware of the standard-dose CT findings. The findings of the standard and low-dose CT scans were compared with the exact McNemar test. Interobserver agreements were assessed with kappa analysis. The effective radiation doses resulting from two different protocols were calculated by means of commercially available software to which the Monte-Carlo phantom model was given. Results: The sensitivity, specificity, and accuracy of standard-dose CT for detecting ureteral stones were 99%, 93%, and 98%, respectively, whereas for the two reviewers the sensitivity of low-dose CT was 93% and 95%, specificity 86%, and accuracy 92% and 94%. We found no significant differences between standard-dose and low-dose CT in the sensitivity and specificity for diagnosing ureter stones ( P >0.05 for both). However, the sensitivity of low-dose CT for detection of 19 stones less than or equal to 2 mm in diameter was 79% and 68%, respectively, for the two reviewers. Low-dose CT was comparable to standard-dose CT in visualizing hydronephrosis and the tissue rim sign. Perinephric stranding was far less clear on low-dose CT. Low-dose CT had the same diagnostic performance as standard-dose CT in diagnosing alternative diseases. Interobserver agreement between the two low-dose CT reviewers in the diagnosis of ureter stones and alternative diseases, the identification of secondary signs, and tissue rim sign were high, with kappa values ranging from 0.769 to 0.968. On standard-dose CT scans, the calculated mean effective radiation dose was 7.30 mSv for males and 10.00 mSv for females. On low-dose CT scans, the calculated mean effective radiation dose was 1.40 mSv for males and 1.97 mSv for females. Conclusion: Compared with standard scans using 260 mAs, low-dose unenhanced helical CT using a reduced tube current of 50 mAs results in a concomitant decrease in the radiation dose of 81%. Although low-dose CT was limited in its ability to depict small-sized calculi less than or equal to 2 mm, it is still comparable to standard-dose CT for the diagnosis of ureter stones and alternative disease

[en] We measured neutron total cross-sections of natural niobium in the neutron energy region from 0.05 to 300 eV by using the time-of-flight method at the Pohang Neutron Facility, which consists of an electron linear accelerator, a water-cooled tantalum target with a water moderator, and a 12-m long time-of-flight path. A ⁶Li-ZnS(Ag) scintillator with a diameter of 12.5 cm and a thickness of 1.6 cm was used as a neutron detector, and a high purity natural niobium metallic disc with a diameter of 8.0 cm and a thickness of 15.0 mm thickness was used for the neutron transmission measurement. Notch filters composed of Co, In, Cd were used to estimate the background level and to calculate the length of neutron flight path. In order to reduce the gamma-ray background from bremsstrahlung and from neutron capture, we used a neutron-gamma separation system based on their different pulse shapes. The present measurement was compared with the existing experimental and the evaluated data. The resonance parameters of ⁹³Nb isotope were obtained from the transmission by using the SAMMY code and were compared with other previous results. (author)

[en] We measured isomeric-yield ratios for the ¹⁹⁷Au(γ,n)^196m,gAu reactions with bremsstrahlung energies of 50-, 60-, 70- MeV, and 2.5-GeV at the two different electron linac of the Pohang accelerator laboratory by using the activation method. The photons were produced when a pulsed electron beam hit a thin tungsten target. The well-known photoactivation method was used and hence the induced activities in the irradiated foils were measured with the high-resolution γ-ray spectrometric system consisting of lithium drifted high-purity Germanium detector and a multichannel analyzer. The measured isomeric-yield ratios for the ¹⁹⁷Au(γ,n)^196m,gAu reactions were (4.95 ± 0.51) x 10^-4, (5.72 ± 0.72) x 10^-4, (6.03 ± 0.50) x 10^-4, and (9.27 ± 0.83) x 10^-4 for 50-, 60-, 70-MeV, and 2.5-GeV bremsstrahlung energies, respectively. The present results measured with the bremsstrahlung energy higher than 60-MeV are the first measurement. (author)

[en] We measured isomeric cross-section ratios for the ⁴⁵Sc , (γ,n)^44m,gSc ,gSc, natTi,x)44m,gSc,103Rh ,4n)99m,gRh, and natFe, x)52m,gMn reactions at the 65-MeV electron linac of the Pohang Accelerator Laborator by using the activation method. Samples of natural Sc, Ti, Rh, and Fe metallic foils were irradiated in an uncollimated bremsstrahlung beam. The isomeric crosssection ratios were determined from the activity measurement with a high-purity germanium detector. The measured isomeric ratios were 0.21 ± 0.03, 0.12 ± 0.03, 1.43 ± 0.20, and 0.28 ± 0.04 for the ⁴⁵Sc ,(γ,n)^44m,gSc, ,gSc, natTi ,x)44m,gSc, 103Rh ,4n)99m,gRh, and natFe ,x)52m,gMn reactions, respectively. The present results for the ⁴⁵Sc ,(γ,n)^44m,gSc,gSc and natFe ,x)52m,gMn reactions are in good agreement with other measurements. The present results for natTi ,x)44m,gSc and 103Rh ,4n)99m,gRh reactions are the first such measurements.

[en] The Pohang Neutron Facility based on an electron linear accelerator was operated for the neutron total cross section measurements by using the pulsed neutrons produced in a water-cooled Ta-target with a water moderator. The neutron total cross sections of Ta and Mo were measured in the neutron energy region from 0.01 eV to 100-200 eV by using the time-of-flight method. A ⁶Li-ZnS(Ag) glass scintillator with a diameter of 12.5 cm and a thickness of 1.6 cm was used as a neutron detector. The neutron flight path from the water-cooled Ta target to the neutron detector was 12.1 m. The background level was determined by using notch-filters of Co, In, Ta, and Cd sheets. In order to reduce the gamma rays from Bremsstrahlung and those from neutron capture, we employed a neutron-gamma separation system based on their different pulse shapes. The present measurements of Ta and Mo are in general agreement with the evaluated data in Endf/B-VI. Cross sections for residual radio-nuclide production by proton-induced reactions on natural molybdenum were measured from their respective threshold energies to 42 MeV by using the MC-50 cyclotron at KIRAMS. The activation method and a stacked-foil technique using high-resolution HPGe gamma-ray spectrometry were applied to determine the excitation functions. The reactions induced on Al and Cu foils were used to monitor the parameters of the proton beam. The present results are in generally good agreement with the earlier reported data and with the calculations based on the ACILE-IPPE code. (authors)

[en] The mass-yield distributions of various fission products have been determined in the 50-, 60- and 70-MeV end point bremsstrahlung induced fission of ^natPb using off-line γ-ray spectrometric technique in the electron linac at Pohang Accelerator Laboratory, Korea. The mass-yield distributions are symmetric with average mass of 102.34, 102.25 and 102.03 and FWHM of 21, 22 and 23 mass unit, respectively. From the present data and literature data in the 50-85 MeV bremsstrahlung induced fission of ²⁰⁹Bi the following observations were obtained: (i) The average masses of the yield distributions in the 50-85 MeV bremsstrahlung induced fission of ^natPb and ²⁰⁹Bi are around 102.25 ± 0.25 and 103 ± 0.5, respectively. (ii) The FWHM of the mass-yield distributions increases from about 21 mass units at 50 MeV to 23 mass units at 70-85 MeV, which is explained from the point of increase in multi-chance fission probability with increasing excitation energy. (iii) Within the bremsstrahlung energy range of 50-85 MeV, the role of nuclear structure effect in the mass-yield distribution was observed in the photo-fission of ²⁰⁹Bi, whereas it was not seen in case of ^natPb. This may be due to the presence of so many isotopes in ^natPb unlike mono-isotopic ²⁰⁹Bi. (author)

[en] The isomeric yield ratios for the ^natFe(γ,xn1p)^52m,gMn reactions have been measured by the activation and the γ-ray spectroscopic methods at 50-, 60-, 70-MeV, and 2.5-GeV bremsstrahlung energies. The high purity natural iron foils in disc shape were irradiated with uncollimated bremsstrahlung beams of the Pohang Accelerator Laboratory. The induced activities in the irradiated foils were measured by the high-resolution γ-ray spectrometry with a calibrated high-purity Germanium (HPGe) detector. In order to improve the accuracy of the experimental results the necessary corrections were made in the gamma activity measurements and data analysis. The obtained isomeric yield ratios for the ^natFe(γ,xn1p)^52m,gMn reactions at 50-, 60-, 70-MeV, and 2.5-GeV bremsstrahlung energies are 0.27 ± 0.03, 0.33 ± 0.04, 0.34 ± 0.04, and 1.25 ± 0.15, respectively. The present results at 50-, 60-MeV, and 2.5-GeV bremsstrahlung energies are the first measurements. We found that the isomeric yield ratio of the ^natFe(γ,xn1p)^52m,gMn reaction depends on the incident bremsstrahlung energy and the mass difference between the product and the target nucleus when we compared the present results with other experimental data at different energies. (author)

[en] We measured the isomeric yield ratios for the ^44m,gSc isomeric pairs produced from different reaction channels ⁴⁵Sc(γ,n)^44m,gSc and ^natTi(γ,xnp)^44m,gSc by using the activation method and γ-ray spectroscopic methods at 50-, 60-, and 70-MeV bremsstrahlung energies. The high-purity natural Sc and Ti foils in disc shape were irradiated with uncollimated bremsstrahlung beams generated from an electron linear accelerator at Pohang Accelerator Laboratory. The induced activities in the irradiated foils were measured by the high-resolution γ-ray spectrometric system which consists of a high-purity Germanium detector and a multichannel analyzer. In order to improve the accuracy of the experimental results the necessary corrections were made in the γ-ray activity measurements and data analysis. The measured isomeric yield ratios for the ⁴⁵Sc(γ,n)^44m,gSc reaction are 0.20 ± 0.02, 0.21 ± 0.02, and 0.21 ± 0.02 and those for the ^natTi(γ,xnp)^44m,gSc reaction are 0.063 ± 0.012, 0.079 ± 0.014, and 0.124 ± 0.022 at 50-, 60-, and 70-MeV bremsstrahlung energies, respectively. The obtained results are compared with the corresponding values found in the literature. We observed that the isomeric yield ratios for the ⁴⁵Sc(γ,n)^44m,gSc reaction increase rapidly with the increasing bremsstrahlung energies from the reaction threshold up to giant resonance region, and then those are almost constant in the energy range from about 30 to 2.5 GeV. The isomeric yield ratios for the ^natTi(γ,xnp)^44m,gSc reaction increase with increasing bremsstrahlung energies in a wide range of bremsstrahlung energies from 50 to 2.5 GeV. (author)

[en] We measured the isomeric yield ratios for the photonuclear reactions of ⁹³Nb(γ,4n)^89m,gNb and ^natMo(γ,xnp)^95m,gNb by using the activation method. The high-purity ⁹³Nb and ^natMo metallic foils in disc shape were irradiated with uncollimated bremsstrahlung beams of 50-, 60-, and 70-MeV generated from an electron linear accelerator in Pohang Accelerator Laboratory. The induced activities in the irradiated foils were measured by the high-resolution γ-ray spectrometry with a calibrated high-purity Germanium (HPGe) detector coupled to a PC-based 4 K multichannel analyzer. The reaction ⁹³Nb(γ,4n)^89m,gNb was studied for the first time which has no comparable literature data. The result of ^95m,gNb isomeric pair was measured based on (γ,p), (γ,np), and (γ,2np) reactions which is the first measurement at the intermediate energy region of 50-70-MeV with a ^natMo target. (author)