Count outcomes, rate ratios and rate differences.

Performance assessment of self-interrogation neutron resonance densitometry for spent nuclear fuel assay

This tutorial focuses on trials that assess outcomes by counting events that can occur zero, one, or more than one time in each participant. Trials and meta‐analyses can estimate treatment effects for count outcomes using rate differences or rate ratios. We explain why it may be appropriate to meta‐analyze count data to estimate rate ratios rather than odds ratios, risk ratios, or risk differences. We explain what count data are, how trials may estimate treatment effects, how to interpret such estimates, and how to extract data from trials that use count outcomes for meta‐analysis. Finally, we discuss some common misunderstandings and subtleties. Supplementary materials include an Excel file for performing calculations, mathematical background, and additional advice.

There is a growing interest in using biomonitoring of tooth and bone specimens to assess human exposure to manganese (Mn). Information on historical exposure to Mn can be obtained through micro-spatial analysis of such specimens by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The principal aim of this study was to compare several calibration strategies for determining Mn content in tooth and bone by LA-ICP-MS including: (a) a six-point calibration curve based on synthesized hydroxyapatite (HA) materials, and single-point calibrations based on (b) NIST SRM 1400 Bone Ash, (c) NIST SRM 1486 Bone Meal, and (d) NIST SRM 612 Trace Elements in Glass. Performance was similar between different ICP-MS platforms (quadrupole ICP-MS, dynamic reaction cell ICP-MS, and sector field ICP-MS). Data based on calibration using the 55Mn count rate were compared to that based on using the 55Mn/43Ca count rate ratio to obtain results as the Mn mass fraction. Reasonable performance was obtained by calibration using either SRM 612 or SRM 1400, in combination with the 55Mn/43Ca count rate ratio and using either the synthesized HA standards or SRM 1400 as calibrators, combined with 55Mn count rate. By contrast, calibration based on SRM 1486 resulted in a systematic low bias. While there are several options for quantifying the Mn content of tooth and bone using LA-ICP-MS, users should be aware of the potential for strong matrix effects that may affect results. Overall, determining the 55Mn/43Ca count rate ratio, rather than the mass fraction, may represent a better approach for reporting the content of Mn in tooth and bone by LA-ICP-MS.

Assessment of inflammatory bowel disease activity by technetium 99m phagocyte scanning

Summary Compensated neutron logging (CNLSM) uses a two-detector system that was developed to reduce borehole effects. The ratio of counting rates from the detectors provides the basic tool response from which a porosity index is obtained. Each detector in this system has a different vertical resolution because of its spacing. A new method of processing the counting rates has been developed to enhance the vertical resolution capabilities of the neutron porosity index by exploiting the better vertical resolution of the near detector. Because no additional or new measurements are required, data from older wells can easily be re-evaluated. Results from the new method have been compared with microspherically focused logs (MicroSFLSM) and electromagnetic propagation logs (EPTSM). They show repeatable thin-bed resolution on the order of 1 ft [0.3 m] for data sampled at 6-in. [15-cm] intervals; the typical vertical resolution from ratio processing is approximately 2 ft [0.6 m]. The statistical precision of the high-resolution processing is superior to that of the standard ratio method. An additional parameter, obtained with the new processing method, provides information about borehole effects. This parameter can be used for qualitative indications of gas when invasion is not deep and environmental effects are not large. The new method has been applied successfully in carbonate and laminated sand formations. Studies show that thin beds can be detected in high-porosity formations where normal processing has significant statistical variations resulting from reduced counting rates.

Calibration of parent and fragment ion detection rates in Rosettas ROSINA/DFMS mass spectrometer

Technetium 99m pertechnetate (99mTcO4−) is a useful radioactive label for thyroid scanning. It is of particular merit when emphasis is placed upon a low dose of thyroid radiation, optimal resolution, and scanning of thyroid glands in which function is decreased or partly blocked. Harper et at. (4) reported the first pertechnetate scan of the thyroid in 1964, and the next year the same group published a paper on pertechnetate thyroid scans in a series of 86 patients (1). Recently, Quinn and Brand (6) reported on 767 patients in whom pertechnetate scans were obtained of the thyroid gland, incidental to brain scans. Certain aspects of this method of thyroid labeling deserve further elucidation and are described in the present report. Material and Method During a six-month period, the thyroid glands of 41 selected patients were scanned with pertechnetate. All patients with hypothyroidism or iatrogenically suppressed thyroid function who had insufficient uptake for 131I thyroid scanning were included in the series. Pertechnetate scans were done in euthyroid patients for three reasons: (a) The dosimetry in children is favorable. (b) The high count rates and ease of collimation allow better evaluation of small thyroid nodules. (c) In patients not able to return the following day for a twenty-four-hour, 131I thyroid scan, scanning is possible within an hour after administration of the label. 99mTcO4 −was administered intravenously in doses of 1 to 5 mCi. The usual dose in adults was 2 mCi and in children 1 mCi. After a period of thirty to sixty minutes, both dot and photoscans were obtained with a 3-inch rectilinear scanner.2 The pulse-height analyzer was set for a 126-to-154-keV window, the time constant at 0.02 second, and scanning speed at 30 or 44 em per minute. A 127-hole, finefocus collimator was employed. The correct setting of background suppression, which is of critical importance to the success of this method, is discussed later. The suppression levels were set at 10 to 70 per cent, allowing only a minimal imaging of nontarget areas. 131I thyroid scans are generally performed after twenty-four hours. By that time most of the labeled iodide in the thyroid gland has been organified, as thyroid hormone and serum levels of iodide are negligible. In contrast, scanning of the thyroid gland with pertechneta.te is performed about one hour after its intravenous administration, when relatively high nontarget count rates are always present. Selection of background suppression depends on the ratio of count rates over the gland to nontarget rates adjacent to it. Figure 1 illustrates some typical examples of target and nontarget count ratios found during programming of a pertechnetate thyroid scan. The background suppression in each instance was set appropriately. In practice, the background suppression is set just high enough to eliminate most of the nontarget counting from the scan.

Neutron monitors of standard design (IGY or NM64) are employed worldwide to study variations in the flux of galactic cosmic rays and solar energetic particles in the GeV range. The design minimizes detector response to neutrons below ∼10 MeV produced by cosmic ray interactions in the ambient medium. Increasingly, however, such neutrons are of interest as a means of obtaining spectral information on cosmic rays, for studies of soil moisture, and for nuclear threat detection. Bare neutron counters, a type of lead-free neutron monitor, can detect such neutrons, but comparatively little work has been done to characterize the dependence of their count rate on cutoff rigidity. We analyze data from three bare neutron counters operated on a ship together with a three-tube NM64 monitor from November 1995 to March 1996 over a wide range of magnetic latitude, that is, a latitude survey. The bare counter design used foamed-in-place polyurethane insulation to keep the temperature uniform and to some extent moderate high-energy neutrons. When the ship was near land, the bare/NM64 count rate ratio was dramatically higher. Considering only data from open sea, the bare and NM64 pressure coefficients are not significantly different. We determine the response function of these bare counters, which is weighted to Galactic cosmic rays of lower energy than the NM64. This measurement of the response function may improve determination of the spectral index of solar energetic particles and Galactic cosmic rays from a comparison of bare and NM64 count rates.

Feasibility study of β-ray detection system for small leakage from reactor coolant system

Neutron monitors of standard design (IGY or NM64) are employed worldwide to study variations in the flux of galactic cosmic rays and solar energetic particles in the GeV range. The design minimizes detector response to neutrons below ∼10 MeV produced by cosmic ray interactions in the ambient medium. Increasingly, however, such neutrons are of interest as a means of obtaining spectral information on cosmic rays, for studies of soil moisture, and for nuclear threat detection. Bare neutron counters, a type of lead‐free neutron monitor, can detect such neutrons, but comparatively little work has been done to characterize the dependence of their count rate on cutoff rigidity. We analyze data from three bare neutron counters operated on a ship together with a three‐tube NM64 monitor from November 1995 to March 1996 over a wide range of magnetic latitude, that is, a latitude survey. The bare counter design used foamed‐in‐place polyurethane insulation to keep the temperature uniform and to some extent moderate high‐energy neutrons. When the ship was near land, the bare/NM64 count rate ratio was dramatically higher. Considering only data from open sea, the bare and NM64 pressure coefficients are not significantly different. We determine the response function of these bare counters, which is weighted to Galactic cosmic rays of lower energy than the NM64. This measurement of the response function may improve determination of the spectral index of solar energetic particles and Galactic cosmic rays from a comparison of bare and NM64 count rates.

Our purpose was to compare the performance of an initial ventilation-perfusion (V/Q) scan protocol with that of a data-driven modified protocol to improve diagnostic quality without increasing radiation dose to the patient. The initial V/Q scan protocol consisted of a ventilation scan after inhalation of (99m)Tc-diethylenetriaminepentaacetic acid (DTPA) aerosol for 5 min followed by a (99m)Tc-macroaggregated albumin perfusion scan. Interim analysis after 34 scans under an initial protocol included calculations of ventilation efficiency, perfusion efficiency, and perfusion-to-ventilation counting rate ratio (Q:V). Ventilation efficiency was defined as ventilation counting rate divided by ventilation dose, perfusion efficiency as perfusion counting rate divided by perfusion dose, and Q:V as perfusion counting rate divided by ventilation counting rate. From these data, the protocol was modified to improve the Q:V ratio and was applied to 60 patients. Results from the 94 scans were tabulated, and a comparison of ventilation efficiency, perfusion efficiency, and Q:V between the 2 protocols was statistically analyzed. The initial protocol returned a mean ventilation efficiency of 7.8% (SD, 4.6%; range, 1.4%-19%), mean perfusion efficiency of 100% (SD, 31%; range, 39%-160%), and mean Q:V of 2.4 (SD, 1.9; range, 0.51-9.0). All 3 parameters displayed a wide range. Fifty-four percent of these cases demonstrated an unacceptable Q:V (≤2) indicating that the perfusion dose did not overwhelm the ventilation dose. To improve Q:V, options included decreasing ventilation dose, increasing perfusion dose, or performing the ventilation scan with a much higher dose after the perfusion scan. To minimize radiation, the protocol was modified to decrease the ventilation from 5 min to 2.5 min. The modified protocol yielded a mean ventilation efficiency of 5.1% (SD, 1.8; range, 2.0-11), mean perfusion efficiency of 120% (SD, 27%; range, 65%-170%), and mean Q:V of 3.6 (SD, 1.7; range, 1.2-12). Differences between protocols were statistically significant for ventilation efficiency, perfusion efficiency, and Q:V (P < 0.02). Less than 8% of cases under the modified protocol exhibited an unacceptable Q:V. The initial V/Q scan protocol was successfully modified to improve image quality with less radiation. By decreasing the ventilation time by half, the percentage of studies with an unacceptable Q:V decreased from 54% to 8%. This analysis may help others to optimize their V/Q protocols.

Novel interpretation approaches for remaining hydrocarbon saturation evaluation were developed from our study and presented in this paper. Innovative power law relationships and algorithms are used for evaluating oil saturation from Carbon/Oxygen (C/O) logs and gas saturation from capture-to-inelastic count rate ratios, based on the principle of the modern multi-detector pulsed neutron tool responses and the total porosity rock model. C/O log interpretation parameters are determined from the crossplot of near detector against far detector C/O logs, and gas saturation interpretation parameters are obtained from the crossplot of near detector versus far detector capture-to-inelastic count rate ratios. An alternative fixed response line method is proposed based on a simplified C/O log response rock model. Integrated interpretation is applied through the post processing combining the interpretations of C/O logs and capture-to-inelastic count rate ratios, to derive the final result. The developed approaches have been applied to wells from Nigeria Delta and North Sea. Example results have successfully demonstrated greater advantages over the traditional methodologies. These new approaches have markedly reduced the saturation uncertainty related to wellbore effects, especially for wells with complex well completions and borehole fluid phase change. These results were subsequently useful information for the dynamic reservoir simulation models.

Proton intensities and energy spectrums in the inner Van Allen belt have been measured with shielded plastic scintillators on three satellites and an Atlas pod. Omnidirectional fluxes of protons above 59, 95, and 148 Mev are given at the equator for L values of 1.25 and 1.48–1.60, and isoflux contours are given in B, L space for protons above 59 Mev. The counting rates of three scintillation counters having threshold energies of 46, 76, and 128 Mev have been analyzed in terms of assumed energy spectrums of the form dф/dE = AE−n and dф/dE = Ae−E/E0. The second form produces a dependence on the geomagnetic parameter L given by E0 = 460L−4.8 Mev. For the theoretical spectral shapes of Lenchek and Singer, cutoff energies have been derived from the ratios of counting rates in the three detectors. The results are in moderately good agreement with the calculations of Singer (in which, because of nonadiabatic effects, the cutoff momentum was found to be of the form Pmax = POL−2), with a best fit value PO = 2000 Mev/c.

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation R. Stephen White; BATSE requirements for a colliding comet source of gamma‐ray bursts. AIP Conf. Proc. 1 July 1994; 307 (1): 620–624. https://doi.org/10.1063/1.45815 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioAIP Conference Proceedings Search Advanced Search |Citation Search

Validation of Geant4’s G4NRF module against nuclear resonance fluorescence data from 238U and 27Al