How to calculate lead concentration and concentration uncertainty in XRF in vivo bone lead analysis

The authors provide a substantial correction for calculating estimates of lead concentration and uncertainty for in vivo X-ray fluorescent bone analysis with Cd-109 source. Based on general principles, they provide mathematical techniques for propagation of uncertainties in XRF analysis. They give additional considerations for lowering the detection limit and improving spectral data quality.     

Preliminary studies on combining the K and L XRF methods for in vivo bone lead measurement

Lead is a toxic material that invokes irreversible neurological problems. Once ingested, lead accumulates in the bones. To study detailed lead poisoning effects it is essential to have an in vivo bone lead measurement tool with a small minimum detectable concentration (MDC). Both K- and L-based XRF methods for the tibia bone have been suggested and developed in the past and are presently in use. In this work a combined K and L XRF method for the tibia bone is proposed. The proposed system consists of a ¹⁰⁹Cd point source and Ge and Si(Li) detectors for optimum detection of the K and L X-rays, respectively. Experimental and Monte Carlo simulated results are given here for a prototype combined K and L XRF system. This system promises to yield a better MDC and the possibility of obtaining information on the near-surface bone lead content as well as the average lead content throughout the bone.     

Biological tissues analysis by XRF microtomography

The main of this work is to determine the elemental distribution in breast and prostate tissue samples in order to verify the concentration of some elements correlated with characteristics and pathology of each tissue observed by the X-ray transmission microtomography (μCT). The experiments were performed at the X-ray fluorescence beamline of the Brazilian Synchrotron Light Laboratory. The μCT images were reconstructed using a filtered-back-projection algorithm and the XRF microtomographies were reconstructed using a filtered-back-projection algorithm with absorption corrections.     

Corrections to "How to calculate lead concentration and concentration uncertainty in XRF in vivo bone lead analysis" by Kondrashov and Rothenberg.

Kondrashov and Rothenberg (Appl. Radiat. Isot. 55 (2001) 799) have published "a substantial correction for calculating estimates of lead concentration and uncertainty for in vivo X-ray fluorescent bone analysis with Cd-109 source" (sic). Our paper shows that their correction fails to consider two important points that render it (i) a correction to a superseded method and (ii) of limited effect. Also, their approach to a "crude" estimate produces measurement uncertainties that are implausibly small. In order that they not be propagated in the literature, our paper also corrects several misstatements and errors in Kondrashov and Rothenberg.     

发色底物法定量测定重组u-PA产品的总活性和单链比例

目的建立一种发色底物酶水解方法定量分析重组尿激酶型纤溶酶原激活剂(u-PA)中的总活性及其单链酶原比例.方法用嗜热菌蛋白酶激活u-PA转化成具有催化活性的双链尿激酶,再用尿激酶的发色底物S-2444测定u-PA的总活性.在非激活条件下,u-PA产品中的单链酶原不会催化水解S-2444底物,因而可以测定其单链酶原比例.结果优化了嗜热菌蛋白酶激活u-PA的反应条件和尿激酶催化水解S-2444的反应条件.用这种方法测定了用CHO细胞表达的基因重组u-PA产品,单链比例大于98%,比活性约为11×104 U/mg.结论用发色底物法测定重组人u-PA产品中的总活性和单链比例具有很好的重复性和准确性.     

Quantitative CBV measurement from static T1 changes in tissue and correction for intravascular water exchange.

The steady-state (SS) approach has been proposed to measure quantitative cerebral blood volume (CBV). However, it is known that the CBV value in SS (CBVSS) is subject to error resulting from the effects of water diffusion from the intra- to extravascular space. CBVSS measurements were simulated in both fast- and no-water-exchange limits, and compared with measured CBVSS values to determine which limiting case is appropriate. Twenty-eight patients were scanned with a segmented Look-Locker echo-planar imaging (LL-EPI) sequence before and after the injection of 0.1 mmol/kg of a T1-shortening contrast agent. Signal changes and T1 values of brain parenchyma and the blood pool were measured pre- and postcontrast. These signal changes and T1 values, in combination with the simulated results, were used to estimate water-exchange rates. We found that the intra- to extravascular water-exchange rates in white matter (WM) and gray matter (GM) were 0.9 and 1.6 s-1, respectively. With these water-exchange rates, the fast-water-exchange limit of the CBV values showed good agreement with the simulation (r=0.86 in WM, and 0.78 in GM). The CBV values with the correction for water-exchange effects were recalculated as 2.73+/-0.44 and 5.81+/-1.12 of quantitative cerebral blood water volume (%) in WM and GM, respectively.     

Verification of reference samples matching in quantitative XRF analysis

A method for verification of matching of reference samples in quantitative x-ray fluorescence analysis of a given material has been suggested. The concept consists of a comparison of the results obtained in both the x-ray fluorescence and the γ-ray transmission measurements. The method has been applied for the determination of iron in Ivorien clays. The presented procedure can be useful in any case, when reference samples of exactly the same material as that to be analysed, are not available.     

Kinetic analysis of lesions without mass effect on breast MRI using manual and computer-assisted methods

Objective  

To analyse the kinetic characteristics of lesions without mass effect in dynamic breast MRI using manual and computer assisted methods.     

用手动选取和计算机辅助的方法分析乳腺MRI中没有占位效应的病灶的动态强化特性

目的用手动选取和计算机辅助的方法分析动态乳腺MRI中没有占位效应的病灶的动态强化特性。方法在乳腺MRI中用手动放置感兴趣区(ROI)的方法评估82例经组织病理学证实的没有占位效应的病灶(36例恶性,46例良性)的增强模式。用商业性可应用的电脑分析软件来自动评     

Improving the in vivo X-ray fluorescence (XRF) measurement of renal mercury.

In vivo polarised X-ray fluorescence (XRF) measurements of renal mercury have previously been reported (B?rjesson J, Barreg?rd L, S?llsten G, Schütz A, Jonson R, Alpsten M, Mattsson S, 1995. In vivo XRF analysis of mercury: the relation between concentrations in the kidney and the urine. Phys. Med. Biol. 40, 413-426). However, with the detection limit reported therein, this system is limited to measurements in cases of significant mercury exposure. An improvement in detection limit is desirable to produce a tool capable of occupational monitoring in cases of mild to moderate exposure. Therefore, design changes have been investigated to improve system performance. Through Monte Carlo simulation and experiment, optimal parameters were determined with respect to polarisation and filtration, as well as the ideal X-ray tube voltage. The optimal configuration will be discussed. A preliminary comparison in terms of minimum detectable limit (MDL) will be made with the preceding polarised XRF renal mercury system.     

Quantitative computed tomographic measurement of a cross-sectional area of a small pulmonary vessel in nonsmokers without airflow limitation

Purpose  

Pulmonary vascular alterations are not exclusive to pulmonary vascular disorders; they are also present in patients with mild chronic obstructive pulmonary disease (COPD) with normal pulmonary function. Moreover, vascular alteration is closely related to lung ventilation. We hypothesized that pulmonary vascular alterations might occur even in nonsmokers with subtle airflow limitation, and there could be a significant correlation between pulmonary vascular alterations and airflow impairment. The purpose of this study was to evaluate the correlation between the vascular alterations measured by cross-sectional area (CSA) and airflow impairment in nonsmokers with normal pulmonary function.     

Use of compton scattering in quantitative XRF analysis of stained glass

x-Ray fluorescence (XRF) trace quantitative analysis employing a monochromatic excitation source has been used for analysing light, non-directly analysable matrix samples, by a method based on the matrix absorption coefficients from an experimental measurement of the intensity of fixed angle Compton scatter radiation. In this work we discuss the assumptions and limits of this method and show some applications to stained glass and ceramics.     

SPECT Compton-scattering correction by analysis of energy spectra

The hypothesis that energy spectra at individual spatial locations in single photon emission computed tomographic projection images can be analyzed to separate the Compton-scattered component from the unscattered component is tested indirectly. An axially symmetric phantom consisting of a cylinder with a sphere is imaged with either the cylinder or the sphere containing 99mTc. An iterative peak-erosion algorithm and a fitting algorithm are given and employed to analyze the acquired spectra. Adequate separation into an unscattered component and a Compton-scattered component is judged on the basis of filtered-backprojection reconstruction of corrected projections. In the reconstructions, attenuation correction is based on the known geometry and the total attenuation cross section for water. An independent test of the accuracy of separation is not made. For both algorithms, reconstructed slices for the cold-sphere, hot-surround phantom have the correct shape as confirmed by simulation results that take into account the measured dependence of system resolution on depth. For the inverse phantom, a hot sphere in a cold surround, quantitative results with the fitting algorithm are accurate but with a particular number of iterations of the erosion algorithm are less good. (A greater number of iterations would improve the 26% error with the algorithm, however.) These preliminary results encourage us to believe that a method for correcting for Compton-scattering in a wide variety of objects can be found, thus helping to achieve quantitative SPECT.     

PET中散射的测量和校正

PET利用符合探测技术除探测两个同时发生的方向相反的 5 11ke V的发射湮灭光子外 ,由于散射辐射的存在 ,同样也探测到与湮灭光子能量相似的散射光子 ,增加了信噪比和错误事件的计数率 ,结果产生赝像。因此 ,了解散射对 PET测量的影响 ,掌握散射及散射份数的测量和散射的校正方法 ,是提高影像质量及精确测定放射性药物的生物学参数的基础