The discovery of bone-seeking compounds that can be labeled with technetium-99m has increased the clinical application of bone scanning. However, if studies of same patient are done at different time, qualitative representations of tracer distribution can suggest changes unrelated to the patient's condition. These difference may be due to scanning conditions that involve injection dose, waiting time, scan speed, and photo factors (cut off, window width, deviation...). Therefore, if the same set of scanning conditions for a particular patient is always used, serial studies should be comparable. We named these serial scintigrams, that can be comparable, "Normalized Scintigrams." But one can guess that this method is a very inconvenient, particulally it is almost impossible setting same injection dose, waiting time, in a series of studies. So our "Normalized Method" does't fix these two scanning conditions (injection dose, and waiting time), and difference of these from first scanning are supplied by scanning speed. Other scanning conditions, they are "photo factors" are fixed the most suitable condition with bone image, and this is not inconvenient. By this method, Normalized Bone Scanning can be performed easily, and changes in disease condition can be evaluated since disease activity is expressed in terms of density on the scintigrams.
This paper is described a simple method to caculate the dose at inside or outside of any irregularly shaped fields. In this method to calculate the scatter dose an irregular field is divided into several square or rectangular fields. The contributing SAR from a divided field is calculated from the product of SAR per unit area and the area. The SAR per unit area is obtained from differentiating the field radius with respect to TAR of circular fields. The errors by this method are less than 2% for Co-60 γ-radiation.
Transmission of low energy X-and γ-rays through several materials for wearing which are used in X-ray and isotope laboratories has been measured by a X-ray Ge(Li) detector. X-and γ-rays emitted from radioactive sources such as ^<55>Fe ^<109>Cd, ^<241>Am, ^<57>Co, ^<210>Pb, ^<75>Se, ^<153>Gd, etc. were used without collimation. The results obtained are figured as the curves characteristics transmission and mass absorption coefficient vs energy for vinyl sheets, cotton, polyethylene, and rubber gloves, under wears, shirts, working wears, summer and winter lounge suits and white robes. Those materials has been best vinyl sheets for hand shielding.
The absorbed dose distribution for patients undergoing CT whole body scanning with EMI computed tomographic equipment (5005) was measured using thermoluminescence dosimeter. The maximum and the minimum dose in the beam path during CT brain and CT abdomen (level of L2) scanning decreased by more than 30% with using a beans bag. The absorbed doses due to scattered and leakage radiation were measured at various critical organs. A conventional radiation protector reduced these doses by 20 to 30%. The maximum absorbed dose of 10 rads during CT brain scanning was comparable to that of 30 rads in angiographic examination and was higher than of 6 rads in tomography examination of brain.
Recently, the popularization of computerized tomography is remarkable. The fixation of patient is changed from waterbag method to beansbag method. The increase of exposure dose is inevitable by generalization of beansbag method. Results obtained in this experiment are as fllows. 1).The examination time was shorten in beansbag method than in waterbag method, but the exposure dose was increared. 2).The direct exposure to lens was decreased by rotation of X-ray tube from three o'clock to nine o'clock. 3).It is difficult to fix the patient during the examination. But the use of beansbag with sugarbag was effective to fix the patient, because hounsfiled number of sugar is - 120. 4).The scatter distribution at one scanning was max. 920 μR to min. 20 μR at 150 cm from the center of rotation.