Reduced tube voltage for pediatric contrast material-enhanced CT reduces radiation dose and maintains image contrast. Image noise increases, but the effect is minimal in smaller phantoms. An additional reduction in tube current further reduces radiation dose.

An x-ray fluorescence system with a synchrotron radiation source was used to quantify the levels of iron, copper and zinc in breast tissue specimens. Healthy tissue and breast carcinomas were investigated as an aid to understanding the mechanisms of breast cancer and as a possible complementary diagnostic tool. Eighty samples were measured in total. Twenty samples were matched pairs, i.e. 20 tumour samples with 20 corresponding healthy tissue specimens taken at a distance from the tumour. The remaining 40 samples consisted of 20 excised tumours and 20 healthy specimens from breast reduction surgeries. The levels of the elements of interest were quantified via calibration models constructed using the XRF response from standard solutions. The statistical analysis of the results indicates elevation of the levels of all three trace elements in the tumours. The effect is more prominent for copper and zinc while the contrast between healthy and diseased tissue is enhanced when comparing the independent specimens rather than the paired samples. Specifically, the ratio of mean tumour to mean healthy concentration for iron was 1.6 for the paired samples and 2.7 for the non-paired samples. The ratios describing copper content were 3.1 for paired and 3.6 for non-paired samples while for zinc they were 2.4 and 4.4 respectively.

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In vitro neutron activation analysis (NAA) was performed on malignant and adjacent normal tissue from 46 human female breast tumours. The objective was to investigate the chemical environment of the tissues within which microcalcifications develop and to develop a method for discrimination between malignant and normal breast tissue. The elements Al, Br, Ca, Cl, Co, Cs, Fe, K, Mn, Na, Rb and Zn were significantly higher in the cancer tissues (all p < 0.001; except for Co, p < 0.003, Wilcoxon signed-ranks test). In addition, a significant correlation (0.80, Spearman rank correlation) was found for Rb and Zn in tumour tissues. Present results are supported by the findings of others. The relevance of elevated concentrations of these elements in cancer breast tissue remains a matter of conjecture. Evidence suggests that there is a connection both with increased cellular activity and blood supply and the formation of microcalcifications in malignant breast tissues. This study suggests an association between the elemental composition of breast tissues and the formation of breast particles. That is, elevations of elemental concentration and clustered calcifications in breast are possibly related.

Regional variations in collagen arrangement show that the highly ordered layers of the articular cartilage are the most important elements in supporting high variable loads. In lesions changes occur in the deep tissue whilst the overlying cartilage appeared normal. We therefore suggest that the interface region is a key element in the early stages of the disease.

For photon energies encountered in diagnostic radiology the shape of the scattering distributions for low-atomic-number media exhibits peaks in intensity close to the forward direction that are not predicted by conventional theoretical models. The positions and shapes of the peaks depend upon the interatomic and intermolecular configurations of the scatterers. The phenomenon is of particular interest because of its relevance to the understanding and modelling of x-ray imaging processes and the possibility that the peaking may be characteristic of tissue type. In the present study, peaks in the forward scattering distributions have been demonstrated for 19 samples of breast tissue and three tissue substitute materials using a position-sensitive photon detector and a 60 kVp x-ray source. Prominent features were observed for all samples investigated. Large differences were found in the shapes of the distributions between adipose and fibroglandular tissues and only small differences were found between carcinomas and fibroglandular tissues.

It is essential that quality control (QC) techniques are developed to keep pace with modern high dose rate (HDR) brachytherapy. Current QC methods may be insufficient to fully assure the accuracy of 3D-optimized dose delivery. This work presents an evaluation of Gafchromic EBT3 film, with multi-channel analysis, in HDR dose environments for advanced QC and commissioning. 'Film-array in water' and 'three-channel Solid Water block' purpose-designed phantoms are utilized. Dose and dose-rate dependency and practical film usage has been evaluated. EBT3 measurements of dose with radial distance from a HDR source are compared to Monte Carlo data. Semi-3D dose distributions around clinical HDR applicators are compared to treatment plans. The measurement of delivery accuracy for inverse-planned pseudo-clinical test cases, with correct delivery and simulated treatment errors, has also been investigated. Local gamma criteria of 3%, 3 mm is recommended with passing rates of at least 96% typically achieved. The system is sensitive to simulated errors in HDR delivery, with significant reductions of passing rate. It has been demonstrated that EBT3 Gafchromic film, in combination with multi-channel analysis, is appropriate for applicator, treatment unit and planning system commissioning measurements as well as practical routine QC to confirm agreement of planned and delivered complex HDR brachytherapy dose distributions.

We describe a novel approach to the search for solar, near-monochromatic hadronic axions, the latter being suggested to be created in the solar core during M 1 transitions between the first excited level of 7 Li, at 478 keV, and the ground state. As a result of Doppler broadening, in principle these axions can be detected via resonant absorption by the same nuclide on the Earth. Excited nuclei of 7 Li are produced in the solar interior by 7 Be electron capture and thus the axions are accompanied by emission of 7 Be solar neutrinos of energy 384 keV. An experiment was made which has yielded an upper limit on hadronic axion mass of 32 keV at the 95% confidence level.PACS number(s): 14.80. Mz, 24.80.+y, 26.65.+t, 96.60.Vg Axions, neutral, spin-zero pseudoscalar particles that go beyond the Standard Model, arise from spontaneous breaking of the Peccei-Quinn (PQ) chiral symmetry [1], the latter being introduced to resolve the strong CP problem. A non-zero axion mass (m a ) can be interpreted as a mixing of the axion field with pions, and is related to the PQ symmetry breaking scale (f a ) by m a f a ≈ m π f π , where m π = 135 MeV is the pion mass and f π ≈ 93 MeV its decay constant. Generically, all effective coupling constants of axions with ordinary matter and radiation are linear in m a or, equivalently, are inversely proportional to f a . The original suggestion that there existed axions, with f a equal to the scale of electroweak symmetry breaking and hence with m a of a few hundred keV, was quickly ruled out by experiment. New axion models have subsequently been proposed which de-couple the PQ scale from the electroweak scale, and introduce f a at a value much greater than 250 GeV. As such, the axion mass and all couplings become extremely small and therefore axion models of this type are generically referred to as invisible axion models. Two classes of invisible axion models have been developed: KSVZ (Kim, Shifman, Vainshtein, and Zakharov) models [2] and DFSZ (Dine, Fischler, Srednicki, and Zhitnitskiȋ) or grand unified theory (GUT) models [3]. The main difference between KSVZ and DFSZ axions is that the former have no tree-level couplings to ordinary quarks and leptons because new heavy quarks have been introduced that carry the PQ charge while usual quarks and leptons do not. As a result, the interaction of KSVZ-type axions with electrons is strongly suppressed. In spite of this, their coupling to nucleons is not zero due to the generic axion-pion mixing which exists even if the tree-level coupling to ordinary quarks vanishes. Since the KSVZ axions do not couple directly to leptons, they are referred to as hadronic axions. The coupling of invisible axions to photons is described by g aγγ ∝ m a {E/N −2(4+z +w)/ [3(1+z +w)]}, where the value of the parameter, E/N , is model dependent for hadronic axions, being a function of exotic fermion charges, while the other parameter within the brackets is a function of quark mass ratios z ≡ m u /m d ≈ 0.55 and w ≡ m u /m s ≈ 0.029 [4]. Note that in a recent review o...