Riparian forests along streams and rivers are diverse in species, structure, and regeneration processes, and have important ecological functions in maintaining landscape and biodiversity. This book ...discusses riparian forests from subpolar to warm-temperate zones, covering headwater streams, braided rivers on alluvial fans, and low-gradient meandering rivers. It presents the dynamics and mechanisms that govern the coexistence of riparian tree species, tree demography, the response to water stress of trees, and the conservation of endangered species, and focuses on natural disturbances, life-history strategies, and the ecophysiology of trees. Because many riparian landscapes have been degraded and are disappearing at an alarming rate, the regeneration of the remaining riparian ecosystems is urgent. With contributions by more than 20 experts in diverse fields, this book offers useful information for the conservation, restoration, and rehabilitation of riparian ecosystems that remain in world streams and rivers.
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FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
purpose: To devise a new calibration method to measure intracranial aneurysm size on digital subtraction angiograms. Methods: Calibration planes were independently established at the upper and lower ...sides of a rotation center of the C-arm, and a calibration scale was placed in one of two calibration planes. One pair of digital subtraction angiograms of the aneurysm is taken from different rotation angles of the C-arm. The projection size of the aneurysm on the calibration plane and the three-dimensional coordinates of the aneurysm are calculated with a calibration scale from these angiograms. Thus, the aneurysm's size is calculated from the geometrical arrangement of the DSA system. To examine precision, we measured the size of seven vessel phantoms (caliber 1.77-12.00 mm) by both the catheter method and the new calibration method. Clinically, the digital subtraction angiograms of 22 cerebral aneurysms treated by endovascular occlusion with the Gugliclmi detachable coil were analyzed by the new calibration method. Results: The new calibration method correlated well with the catheter method (y=0.9726_x+0.0023,R^2=1). The error of the catheter method was 4.40%±3.29% (n=245), while that of the new calibration method was 3.63%±2.14% (n=1470), indicating that the new calibration method was significantly more precise (p<0.0001). It was found that aneurysmal size measured by the new calibration method correlated well with the maximum diameter of the Guglielmi detachable coil. Conclusion: Accurate digital subtraction angiographic measurements of intracranial aneurysm size could be obtained in most aneurysms. The measurements of intracranial aneurysm size measured by the new calibration method are highly useful as an index for the Guglielmi detachable coil technique.
Purpose : To estimate scattered dose rates from phantom measurements during interventional radiology(IVR)and to establish methods to reduce the angiographer's exposure in IVR. Materials and methods : ...Scattered dose rates were measured in lines parallel in space to the central ray of the x-ray beam, at lateral distances of 50 cm. They were measured by the ionization chamber dosimeter, which was made to have directivity by a lead slit. New radiation protective devices for angiographers were developed and their effects evaluated. Results : The scattered dose rates to which the angiographer was exposed during IVR were scattered from a collimator and a patient. The abdominal area was almost completely exposed by the scattered dose from the patient. The head and neck area were exposed by the commensurate scattered dose from the collimator and the patient. The scatter exposure rates of the abdominal area were reduced to 5-20% by a lead curtain attached beneath the tissue table and a lead barrier next to the patient's trunk. And the scattered dose rates of the head and neck area were reduced to 50-70% by shielding a surface of the tissue table between the angiographer and the patient. Conclusion : To reduce exposure of the head and neck area, it is necessary to shield the surface of the tissue table between the angiographer and the patient. To reduce exposure of the abdominal area, it is necessary to shield beneath the tissue table and next to the patient's trunk. The new radiation protective devices were considered very useful and effective in reducing the angiographer's exposure rates.
Scattered radiation levels near ana imaging system commonly used in angiography were measured with a 200 mm thick water phantom. The scattered radiation exposure rate was measured in lines parallel ...in space to the central ray of the x-ray beam, at lateral distances of 30-100 cm. The effects of an x-ray beam limiting device, geometric and electric magnification, and rotation angle of the C-arm were also determined. The results indicated that the highest scattered radiation levels occurred near the surface of the phantom where the x-ray beam enters. In P-A geometry, the highest radiation levels occurred below the angiographer's waist. These areas of the body corresponded to the gonads of the angiographer. It has been suggested that angiographers' exposure rates are higher near the gonads than near the chest. However, lead aprons efficiently protect these areas. When smaller field sizes were limited by a variable x-ray beam limiting device, the volume of irradiated tissue was reduced, and the scattered radiation exposure rate was decreased. Further, when larger magnification factors were chosen for the analogue magnification method, the volume of irradiated tissue was reduced by the automatic x-ray beam limiting device, and the scattered radiation exposure rate was decreased. However, smaller field sizes markedly increased patient exposure by auto brightness control. To mitigate the angiographer's exposure, smaller field sizes with x-ray limiting devices are required. However, a larger field size should by used whenever possible to minimize patient exposure. The angiographer's exposure rate was influenced by the incidence direction of the x-ray beam when the C-arm had been rotated around the phantom. Consequently, the angiographer's exposure rate was maximum when the x-ray tube most closely approached the angiographer and was minimum when the image intensifier most closely approached the angigrapher. Therefore, to mitigate the angiographer's exposure, attention needs to be given to the incidence direction of the x-ray beam.
Measurement of the pituitary height was performed on magnetic resonance (MR) images of 213 subjects with no known or suspected pituitary and/or hypothalamic disorders. Midsagittal, T1-weighted images ...were used for measurements and mean heights in each age and sex group were obtained. In the 10 to 69 year range, the pituitary heights were greater in females than in males. The groups of 0-9 years of both genders showed the minimum mean pituitary height. The maximum of the mean height was observed in the 10 to 19 year age groups of both genders. The height gradually decreased with increasing age after age 20 years. There were no subjects with a height of greater than or equal to 9.0 mm in females or greater than or equal to 8.0 mm in males. There was a marked discrepancy between MR and autopsy findings in the older subjects, probably related to the upward concavity that is often encountered in the aged gland. Because of this concavity, the midsagittal MR measurement will induce underestimation of the whole gland.
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