The tomography beamline at the National Synchrotron Light Source

We compared the image contrast of a monochromatic CT, Multiple Energy Computed Tomography (MECT), and conventional CT scanner using phantoms. The experimental results indicate that monochromatic CT, with beam energy tuned just above the iodine K-edge, has about a 3 fold advantage in iodine contrast over conventional CT with a 120 kVp beam. Modeling using the same beams at a 3 rad dose and 3 mm slice height on an 18 cm diameter acrylic phantom, the simulations show a noise of 1.2 HU for MECT and 1.9 HU for CCT. Furthermore, despite the Cupping-effect corrections the bone contrast is lower in CCT and varies by 24 HU moving from the phantom`s center to the edge; this indicates an advantage for MECT in detecting and quantifying lesions differing from surrounding tissue by their mean atomic number

Dual energy iodine contrast CT with monochromatic x-rays

Computed tomography (CT) with monochromatic x-ray beams was used to image phantoms and a live rabbit using the preclinical Multiple Energy Computed Tomography (MECT) system at the National Synchrotron Light Source. MECT has a horizontal fan beam with a subject apparatus rotating about a vertical axis. Images were obtained at 43 keV for single-energy studies, and at energies immediately below and above the 33.17 keV iodine K-edge for dual-energy subtraction CT. Two CdWO{sub 4}-photodiode array detectors were used. The high-resolution detector (0.5 mm pitch, uncollimated) provided 14 line pair/cm in-plane spatial resolution, with lower image noise than conventional CT. Images with the low-resolution detector (1.844-mm pitch, collimated to 0.922 mm detector elements) had a sensitivity for iodine of {approx} 60 {micro}g/cc in 11-mm channels inside a 135 mm-diameter acrylic cylindrical phantom for a slice height of 2.5 mm and a surface does of {approx} 4 cGy. The image noise was {approx} 1 Hounsfield Unit (HU); it was {approx} 3 HU for the same phantom imaged with conventional CT at approximately the same dose, slice height, and spatial resolution ({approx} 7 lp/cm). These results show the potential advantage of MECT, despite present technical limitations

In vivo neutron activation facility at Brookhaven National Laboratory

Seven important body elements, C, N, Ca, P, K, Na, and Cl, can be measured with great precision and accuracy in the in vivo neutron activation facilities at Brookhaven National Laboratory. The facilities include the delayed-gamma neutron activation, the prompt-gamma neutron activation, and the inelastic neutron scattering systems. In conjunction with measurements of total body water by the tritiated-water dilution method several body compartments can be defined from the contents of these elements, also with high precision. In particular, body fat mass is derived from total body carbon together with total body calcium and nitrogen; body protein mass is derived from total body nitrogen; extracellular fluid volume is derived from total body sodium and chlorine; lean body mass and body cell mass are derived from total body potassium; and, skeletal mass is derived from total body calcium. Thus, we suggest that neutron activation analysis may be valuable for calibrating some of the instruments routinely used in clinical studies of body composition. The instruments that would benefit from absolute calibration against neutron activation analysis are bioelectric impedance analysis, infrared interactance, transmission ultrasound, and dual energy x-ray/photon absorptiometry

CT with monochromatic synchrotron x rays and its potential in clinical research

A monochromatic CT for imaging the human head and neck is being developed at the National Synchrotron Light Source. We compared the performance of this system, multiple energy computed tomography [MECT], with that of a conventional CT [CCT] using phantoms. The advantage in image contrast of MECT, with its beam energy turned just above the K-edge of contrast element, over CCT carried out at 120 kVp, was {approx} 3.2-fold for iodine and {approx} 2.2 fold for gadolinium. Image noise was compared by simulations because this comparison requires matching the spatial resolutions of the two systems. Simulations at a 3-rad dose and 3-mm slice height on an 18-cm-diameter acrylic phantom, with MECT operating at 60.5 keV, showed that image noise for MECT was 1.4 HU vs. 1.8 HU for CCT. Simulations in the dual energy quantitative CT [DEQCT] mode showed a two-fold advantage for MECT in image noise, as well as its superior quantification. MECT operated in the planar mode revealed fatty tissue in the body of rat using xenon K-edge subtraction. Our initial plan for clinical application of the system is to image the composition of carotid artery plaques non-invasively, separating the plaques` main constituents: the fatty, fibrous, and calcified tissues

Spatially fractionated microirradiation of normal CNS and gliosarcomas of the rat with synchrotron photons: Cell and tissue lesions; Raeumlich fraktionierte Mikrobestrahlung von normalem ZNS und Gliosarkomen der Ratte mit Synchrotron-Photonen: Zell- und Gewebelaesionen

Rats were implanted intracerebrally with 9L gliosarcoma cells were used to experimentally determine the curative effectiveness of synchrotron radiation produced by the National Synchrotron Radiation Source. Radiation was delivered in beams with each ray 25 micrometers thick and arranged in an array of 4 mm corners. All experimental animals receiving the gliosarcoma cells and not treated died within four weeks. Treated animals surviving 113 days were sacrificed and their brains were examined histologically

gamma. -ray decay and nuclear shapes in /sup 158/Yb

The decay of the entry states in /sup 158/Yb populated in the reactions of 149 MeV /sup 20/Ne with /sup 144/Nd and /sup 146/Nd has been investigated with a 4 ..pi.. multidetector system gated by a Ge counter. The average exitation energy, the ..gamma..-ray spectra and the angular distributions as a function of multiplicity show several changes in the ..gamma..-ray decay. These changes suggest a transition from prolate to particle aligned oblate configuration at I approx. 28. At I 38 to 48 collective transitions with dipole and quadrupole component are observed. Possible explanations for these transitions are discussed in terms of nuclear shapes. Furthermore, above I approx. 48 the dipole component disappears suggesting a further change toward more triaxial shape. 19 references

Research highlights with the spin spectrometer

The excitation energy and angular momentum dependence of the entry states in fusion reactions measured with the spin spectrometer is discussed. A new decay mode involving the onset of localized stretched dipole radiation at half the accompanying stretched E2 collective radiation is found in /sup 157 -161/Yb. The appearance of this mode correlates smoothly with neutron number and spin. Possible interpretations are presented in terms of the evolution of the nuclear shapes from prolate to aligned-quasiparticle oblate to collective oblate and then to triaxial. Evidence for nuclear deformation that increases with spin at very high excitation is presented based on ..cap alpha..-particle angular distributions measured relative to the spin direction, using a new method for deriving the spin alignment

Survey of the population of the entry states in fusion reactons

The population of the entry states from fusion reactions induced by /sup 20/Ne and /sup 50/Ti is investigated for a large number of reaction systems. Entrance channel l-distributions leading to fusion are deduced. The limiting angular momentum imparted to the evaporation residues is investigated as a function of Z and A. Fission plays a dominant role in determining the distributions in the evaporation residues. The effect of other mechanisms is also discussed. Prominent variations in the observed population distributions in (E*, M/sub ..gamma../) space are attributed to nuclear structure effects