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[en] Magnetic particle imaging (MPI) is a tracer-based imaging technique that can be used for imaging vessels and organ perfusion with high temporal resolution. Background signals are a major source for image artifacts and in turn restrict the sensitivity of the method in practice. While static background signals can be removed from the measured signal by taking a dedicated background scan and performing subtraction, this simple procedure is not applicable in case of non-stationary background signals that occur in practice due to e.g. temperature drifts in the electromagnetic coils of the MPI scanner. Within this work we will investigate a dynamic background subtraction method that is based on two background measurements taken before and after the object measurement. Using first-order interpolation it is possible to remove linear background changes and in turn significantly suppress artifacts. The method is evaluated using static and dynamic phantom measurements and it is shown that dynamic background subtraction is capable of reducing the artifact level approximately by a factor of four. (paper)
[en] Ischemic cardiomyopathy (ICM) and non-ICM (NICM) causes of dilated cardiomyopathy with similar clinical presentation have different management and prognosis. This study employed myocardial perfusion imaging (MPI) to differentiate between the two using quantitative parameters in Indian population. Fifty patients prospectively underwent MPI and 18F-fluorodeoxyglucose metabolism studies. P values (0.05 as significant) were calculated for the left ventricular ejection fraction (EF), end diastolic volume (EDV) at rest and stress, end systolic volume (ESV) at rest and stress, summed rest score (SRS), summed difference score (SDS), and eccentricity. On 6-month follow-up, rate of hospital admission, change in management and death was correlated for ICM and NICM. Coronary angiography (CAG) being gold standard, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and level of agreement were calculated for MPI. MPI and CAG had a moderate level of agreement (κ = 0.463) for differentiating ICM and NICM. The sensitivity, specificity, PPV, NPV, and diagnostic accuracy were 79.31%, 66.67%, 76.67%, 70.0%, and 74% for ICM and 66.67%, 79.31%, 70%, 76.67%, and 74% for NICM, respectively. Significant differences were seen in EDV stress (P = 0.045), EDV rest (P = 0.031), ESV rest (P = 0.034), SRS (P = 0.004), Left ventricular EF rest (P = 0.049) and SDS in ICM and NICM, respectively. EDV at rest and stress, ESV at rest, SRS, SDS, and EF at rest obtained using MPI provides precise quantitative information to differentiate ICM and NICM. It is wide and easy availability, noninvasiveness, objectivity, and near absence of complications favors it as a preferable diagnostic tool with its given sensitivity, specificity, and accuracy for the purpose.
[en] The data in the Annex to the EURATOM Basic Standards give rise to criticism in the following points: the classification of radionuclides does not correspond to that of the relative radiotoxicity for some nuclides. The derived limit of tritium concentration in air does not make allowance for elemental tritium autooxidation. The limits of annual intake are in some cases higher than permissible due to the chemical toxicity. (author)
[en] Phase analysis can be easily performed by different software to assess the left ventricular dyssynchrony from gated single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) with high precision. However, the normal values of histogram bandwidth (HBW) and phase standard deviation (PSD) and their comparison using different programs have not been fully elucidated and actively being evaluated at present. The aim of this study was to determine the phase analysis parameters values and to compare the phase indices of two commonly used programs in a group of patients with normal gated SPECT-MPI. Phase parameters were retrospectively evaluated in 138 consecutive nondiabetic patients having a normal gated SPECT-MPI using the quantitative gated SPECT (QGS) and Emory Cardiac Toolbox (ECTb) software. HBW, PSD, and phase entropy were calculated separately using both programs. The fair correlation between software programs was observed. HBW and PSD in QGS and ECTb were 26.20 ± 9.7 and 25.46 ± 8.0 (r-value. 56, SEE 6.65) and 6.64 ± 2.5 and 7.65 ± 2.5 (r = 0.54, SEE 2.14), respectively. The value of phase entropy in QGS program was 45.08 ± 6.3. A fair correlation between phase entropy and PSD in QGS was observed (r = 0.44, 95% confidence interval-0.29–0.56). Phase analysis parameters derived from gated SPECT-MPI in patients with normal myocardial perfusion are program dependent and may differ. The results cannot be interchangeably used in the same patients.
[en] Fresh, commercial cattle bones containing 600 pCi 90Sr per kilogram were cooked in waters of different degrees of hardness according to an usual beef-tea recipe. After cooking, 90Sr was also detected in the leftover meat (about 40 pCi per kilogram) adhering to the bones. The beef-tea contained about 1 pCi 90Sr per litre corresponding to 0.5 to 0.7% of the total amount of 90Sr which were found in fresh bones. Assuming a weekly consumption of 1 litre beef-tea and 50 g leftover meat, the annual ingestion of 90Sr would be 160 pCi corresponding to 0.1 to 0.2% of the maximum permissible annual intake, or to 5% of the total 90Sr dietary intake in 1974, respectively. (author)
[en] This paper reviews briefly the limits for the intake of natural U. It is concluded that intake of soluble compounds of natural uranium should be limited by considerations of chemical toxicity to the kidney. An inhalation limit of 1.2 mg/day and an ingestion limit of 12 mg/day for occupational exposure to soluble U were derived
[en] The International Commission on Radiological Protection (ICRP) held its annual meeting in Stockholm in May 1978, together with its four expert committees. The Commission reviewed its 1977 recommendations (ICRP Publication 26) and identified some points that require clarification. These are discussed and textual revisions to certain paragraphs of ICRP publication 26 are listed. (author)
[en] Magnetic particle imaging (MPI) is an imaging modality that detects the response of a distribution of magnetic nanoparticle tracers to alternating magnetic fields. There has recently been exploration into multi-contrast MPI, in which the signal from different tracer materials or environments is separately reconstructed, resulting in multi-channel images that could enable temperature or viscosity quantification. In this work, we apply a multi-contrast reconstruction technique to discriminate between nanoparticle tracers of different core sizes. Three nanoparticle types with core diameters of 21.9 nm, 25.3 nm and 27.7 nm were each imaged at 21 different locations within the scanner field of view. Multi-channel images were reconstructed for each sample and location, with each channel corresponding to one of the three core sizes. For each image, signal weight vectors were calculated, which were then used to classify each image by core size. With a block averaging length of 10 000, the median signal-to-noise ratio was 40 or higher for all three sample types, and a correct prediction rate of 96.7% was achieved, indicating that core size can effectively be predicted using signal weight vector classification with close to 100% accuracy while retaining high MPI image quality. The discrimination of the core size was reliable even when multiple samples of different core sizes were placed in the measuring field. (paper)
[en] Ionizing radiation is now showing new promise of contributing to the feeding of hungry populations, solving solid and liquid waste disposal problems, providing safer medical supplies, pharmaceuticals, and other commodities, and at the same time reducing energy consumption in industrial processing in general. (author)