Facile access to 154Eu, a new reference source for calibration in gamma ray spectrometry.

Europium-154 can be obtained as a by-product from the large-scale production of Samarium-153 and possesses attractive features (t1/2 8.592 yr; Egamma 0.12-1.6 MeV) for use as a reference source similar to 152Eu (t1/2 13.516 yr; Egamma 0.12-1.4 MeV), which is the gold standard for calibration in gamma ray spectrometry. Thermal neutron irradiation of 5mg of 98% enriched 153Sm2O3 target in the reactor led to approximately 200 GBq 153Sm and 1.26 MBq 154Eu. A typical batch control sample of 153SmCl3 solution and final radiopharmaceutical product formulation of 153Sm-phosphonate (153Sm-EDTMP) pooled together contained about 20% of total yield, requiring post decay disposal of 153Sm as radioactive waste. Such spent solutions pooled on quarterly basis led to availing 756 kBq of 154Eu. The radioactivity content and radionuclide purity (approximately 82%) of the recovered 154Eu sample were envisaged as adequate to prepare reference sources for calibration of gamma ray spectrometers. At present, one batch of 153Sm is handled per month at our institution, with the possibility for weekly processing in future. Access to approximately 3.5 MBq of 154Eu on quarterly basis is envisaged, apart from obviating the need for instituting steps to tackle disposal of the long-lived 154Eu in the spent solution. Up to 60-120 units of 20-100 kBq of 154Eu reference sources per year could thus be available by the proposed strategy.     

A deconvolution technique for processing small intestinal transit data

The deconvolution technique can be used to compute small intestinal impulse response curves from scintigraphic data. Previously suggested approaches, however, are sensitive to noise from the data. We investigated whether deconvolution based on a new simple iterative convolving technique can be recommended. Eight healthy volunteers ingested a meal that contained indium-111 diethylene triamine penta-acetic acid labelled water and technetium-99m stannous colloid labelled omelette. Imaging was performed at 30-min intervals until all radioactivity was located in the colon. A Fermi function=(1+e-alphabeta)/(1+e(t-alpha)beta) was chosen to characterize the small intestinal impulse response function. By changing only two parameters, alpha and beta, it is possible to obtain configurations from nearly a square function to nearly a monoexponential function. Small intestinal input function was obtained from the gastric emptying curve and convolved with the Fermi function. The sum of least squares was used to find alpha and beta yielding the best fit of the convolved curve to the observed small intestinal time-activity curve. Finally, a small intestinal mean transit time was calculated from the Fermi function referred to. In all cases, we found an excellent fit of the convolved curve to the observed small intestinal time-activity curve, that is the Fermi function reflected the small intestinal impulse response curve. Small intestinal mean transit time of liquid marker (median 2.02 h) was significantly shorter than that of solid marker (median 2.99 h; P<0.02). The iterative convolving technique seems to be an attractive alternative to ordinary approaches for the processing of small intestinal transit data.     

A deconvolution technique for processing small intestinal transit data

The deconvolution technique can be used to compute small intestinal impulse response curves from scintigraphic data. Previously suggested approaches, however, are sensitive to noise from the data. We investigated whether deconvolution based on a new simple iterative convolving technique can be recommended. Eight healthy volunteers ingested a meal that contained indium-111 diethylene triamine penta-acetic acid labelled water and technetium-99m stannous colloid labelled omelette. Imaging was performed at 30-min intervals until all radioactivity was located in the colon. A Fermi function=(1+e ^−αβ)/(1+e ^(t−α)β ) was chosen to characterize the small intestinal impulse response function. By changing only two parameters, α and β, it is possible to obtain configurations from nearly a square function to nearly a monoexponential function. Small intestinal input function was obtained from the gastric emptying curve and convolved with the Fermi function. The sum of least squares was used to find α and β yielding the best fit of the convolved curve to the oberved small intestinal time-activity curve. Finally, a small intestinal mean transit time was calculated from the Fermi function referred to. In all cases, we found an excellent fit of the convolved curve to the observed small intestinal time-activity curve, that is the Fermi function reflected the small intestinal impulse response curve. Small intestinal mean transit time of liquid marker (median 2.02 h) was significantly shorter than that of solid marker (median 2.99 h; P<0.02). The iterative convolving technique seems to be an attractive alternative to ordinary approaches for the processing of small intestinal transit data. Received 17 August and in revised form 15 November 1998     

核电站周围环境样品的γ谱分析方法

本文作介绍了用锗γ谱仪分析核电站周围低水平环境样品中人工核索和天然核素时所建立的方法。主要描述丁潜仪的刻度:有笑γ符合相加校正和样品舟一旺收曼王的考虑.谱仪探测限计算；一些核素特征蜂面积的计算方法和注意事项；以及误差分析与估算等,提出了充分利用谱数据计算²²⁶Ra、²²⁸Ra、²²⁶Th等核素含量以减少误差的方法。     

Application of gamma ray scattering technique for non-destructive evaluation of voids in concrete

This paper describes application of the gamma ray scattering technique for NDE of concrete voids. A novel nonlinear extrapolation method is employed to correct for self-absorption and multiple scattered intensities. The attenuation data obtained from transmission method is employed for reconstruction of scattered images and the results show a good agreement in size and position of the voids with good spatial resolution. Intercomparison of the results of scattering and transmission techniques shows a good agreement in the position of the voids.     

137Cs measurement uncertainties and detection limits for airborne gamma spectrometry (AGS) data analysed using a spectral windows method.

The uncertainties associated with airborne gamma spectrometry (AGS) measurements analysed using a spectral windows method, and associated detection limits, have been investigated. For individual short measurements over buried 137Cs activity detection limits of 10 kBq m(-2) are achieved. These detection limits are reduced for superficial activity and longer integration times. For superficial activity, detection limits below 1 kBq m(-2) are achievable. A comparison is made with the detection limits for other data processing methods.     

Peak efficiency calibration for attenuation corrected cylindrical sources in gamma ray spectrometry by the use of a point source

A theoretical method of determining the gamma-ray peak efficiency for a cylindrical source, based on a modified expression for point sources is derived. A term for the photon self-attenuation is included in the calculation. The method is valid for any source material as long as the source activity concentration is considered to be homogeneous. Results of this expression are checked against experimental data obtained with ²⁴¹Am, ⁵⁷Co, ¹³⁷Cs, and ⁶⁰Co sources.     

A comparison of alpha and gamma spectrometry for environmental natural radioactivity surveys.

An alpha-spectrometry, using automated borate fusion and sequential extraction and exchange chromatography, was used to determine the uranium and thorium based on environmental radioactivity of 20 soil samples. The same set of the samples was analysed using gamma-spectrometry with an HPGe detector. The two data sets were checked for coherence using Z-score and chi2 statistical tests. We show that gamma-spectrometry is a valid alternative to time-consuming alpha-spectrometry for the determination of natural uranium and thorium activity in soil (activity range: 12.5-58.2 Bq/kg). The measured activities were compared with the theoretical activities to ensure secular equilibrium in the 238U and 232Th series. For 226Ra, a special study was made on deconvolution of the 186 keV multiplet with the Levenberg-Marquardt algorithm. Finally, the combined use of Z-score and chi2-tests was found to be a powerful tool for comparing the results obtained with two different methods.     

A modified scintigrafic technique for amputation level selection in diabetics

A modified ¹²³I-antipyrine cutaneous washout technique for the selection of amputation levels is described. The modifications imply a reduction of time needed for the examination by simultaneous recordings on different levels, and a better patient acceptance by reducing inconvenience. Furthermore, both skin perfusion pressure (SPP) and skin blood flow (SBF) are determined from each clearance curve. In a prospective study among 26 diabetic patients presenting with ulcers or gangrene of the foot, both SPP and SBF were determined preoperatively on the selected level of surgery and on adjacent amputation sites. These 26 patients underwent 12 minor foot amputations and 17 major lower limb amputations. Two of these amputations failed to heal. SBF values appeared indicative for the degree of peripheral vascular disease, as low SBF values were found with low SPP values. SPP determinations revealed good predictive values: all surgical procedures healed when SPP>20mmmHg, but 2 out of 3 failed when SPP < 20 mmHg. If SPP values would have been decisive, the amputation would have been converted to a lower level in 6 out of 17 cases. This modified scintigrafic technique provides accurate objective information for amputation level selection.     

A modified scintigraphic technique for amputation level selection in diabetics

A modified 123I-antipyrine cutaneous washout technique for the selection of amputation levels is described. The modifications imply a reduction of time needed for the examination by simultaneous recordings on different levels, and a better patient acceptance by reducing inconvenience. Furthermore, both skin perfusion pressure (SPP) and skin blood flow (SBF) are determined from each clearance curve. In a prospective study among 26 diabetic patients presenting with ulcers or gangrene of the foot, both SPP and SBF were determined preoperatively on the selected level of surgery and on adjacent amputation sites. These 26 patients underwent 12 minor foot amputations and 17 major lower limb amputations. Two of these amputations failed to heal. SBF values appeared indicative for the degree of peripheral vascular disease, as low SBF values were found with low SPP values. SPP determinations revealed good predictive values: all surgical procedures healed when SPP greater than 20 mmHg, but 2 out of 3 failed when SPP less than 20 mmHg. If SPP values would have been decisive, the amputation would have been converted to a lower level in 6 out of 17 cases. This modified scintigraphic technique provides accurate objective information for amputation level selection.     

A data adaptive reprojection technique for MR angiography.

Inability to detect vessel overlap and vascular loops can compromise the interpretation of magnetic resonance angiograms. A data-adaptive ray tracing (DART) technique was developed to produce the appropriate variations in signal intensity at points of vessel overlap in order to simulate the standard angiographic representation of vessels. In this technique a threshold is utilized to identify vessels in the image slices composing a 3D angiographic data set. A mask, which defines regions slightly larger than the vessel boundaries, is obtained by blurring the vessel information surviving the initial threshold. This mask is converted to binary form prior to multiplication by the original angiographic data set. Following application of an additional threshold to the masked data, line integrals through the regions defined by the mask are performed to obtain an angiographic signal proportional to the integrated vessel signal as in conventional angiography. This integrated reprojection is then uniquely combined with a maximum intensity pixel (MIP) reprojection to produce the final DART image. The application of the DART technique to 2D time-of-flight and 3D phase-contrast angiograms successfully enabled the identification of over-lapping vessels and vascular loops. DART was also found to produce less vessel narrowing than the MIP technique.     

A knowledge-based technique for liver segmentation in CT data

Liver cancer is one of the major death factors in the world. Transplantation and tumor removal are two main therapies in common clinical practice. Both tasks need image assisted planning and quantitative evaluations. Automatic liver segmentation is required for corresponding quantitative evaluations. Conventional approaches in liver segmentation consist of finding the initial liver border followed by tuning the border to the final mask. Finding the liver initial border is of great importance as the latter step largely depends on the initial step. In the previous works, the liver initial border was determined by applying thresholding and morphological filters. In order to estimate the liver initial boundary, we have proposed a technique based on anatomical knowledge of liver, its surrounding tissues as well as the approach that a clinician follows in screening liver in a CT dataset. Based on the above reasoning, we developed a multi-step heuristic technique to segment liver from other tissues in multi-slice CT images. The proposed technique can deal with various shapes, locations, and liver sizes. The method was evaluated in the presence of 50 actual liver data sets and the results were encouraging.     

Development of a low cost, GPS-based upgrade to a standard handheld gamma detector for mapping environmental radioactive contamination.

A low cost extension to a standard handheld radiation monitor was developed, allowing one to perform outdoor georeferenced gamma measurements. It consists of a commercial wireless Bluetooth GPS receiver, a commercial RS-232 to Bluetooth converter combined with a standard Bluetooth enabled pocket personal computer (PPC). The system is intended for use in difficult to access areas, typically for foot campaigns. As the operator walks, a straightforward homemade visual basic program alternately reads GPS position and gamma dose rate into the PPC, creating a data log. This allows a single operator on foot to map between 50 and 200 ha of environmental radiation per day in very rugged areas, depending on the accessibility of the terrain and the detail required. On a test field with known contamination, a spatial precision of about 5-10 m was obtainable. The device was also used to reveal complex contamination patterns in the flooding zones of a radioactively contaminated small river.