Image quality of radiogram were evaluated subjectivity by human's eye. And now that we could be objectifie by technique of Modulation Transfer Function (M.T.F.), many experiment have been reported. But technique of M.T.F. in those experiment was not few inaccurate factor so as to evaluate on various tube-shifting tomogram. In this paper, original pin-hole are used for settlement of this probrem, and M.T.F. of tomographic system of each tube-shifting was found, that was compared. The tomogram was separated to layer plain and other plain, and those M.T.F. were found to each position. As a result of comparison on those M.T.F., we thinked that it were useful tube-shifting to circular motion and hypocycloidal motion.
The commercially available molybdenum target tubes for mammography are usually used with a 30 μ molybdeunm external filter. This filter was modified by the addition of Sn or Ag foil measuring respectively 14 μ and 10 μ in thickness to the 15 μ Mo filter. These composite filters resulted in reducing skin dose and improving image contrast for their absorption edges in the energy range used for mammography. The Ag-Mo composite filter provided optimum contrast at the tube voltage range of 27〜35 kVp. Meanwhile, the Sn-Mo filter resulted in lowering the patient dose in providing optimum contrat over 40 kVp. In these kVp ranges, the both composite filter served to deminish exposure time by 30 per cent and skin dose by 20 percent as compared with the 30 μ Mo filter in producing identical contrast.
The xerox 125 system was used to make a comparative image quality study between xeroradiography (XR) and industrial type MR film which is approximately equivalent to Kodak type AA film. The comparison of the image quality was made by objective and subjective methods at the visual threshold, since diagnostic details in actual mammograms are often marginably detectable. 1) Dependence of the output density distribution on edge gradient is studied in the spatial and the spatial frequency domain. The test objects employed are aluminum rods having square and round cross-sections of 200 μ which simulate calcification in X-ray absorption. The infinite edge gradient of the square alumiunm rod narrows the width at the image with a wide deletion of the powder outside the boundary, while the alumiunm cylinder increases its image width by attracting extra powder inside the boundary. Density distributions of the alminum test objects are converted to spatial frequency spectra by means of Fourier transformation. The use of a square bar results in an excessive decrease of the output amplitude at low spatial frequencies though greater in amplitude in the intermediate to high spatial frequencies than the cylindrical object. 2) RMS granularity σ(D) is determined by a scanning microdensitometer with a 10×150 μ wide scanning slit adjusted with respect to eye's line spread function. Ganularity of the 125 system is dramatically improved than other xeroradiographic systems which have been seen. It may be due to plastic coating on the transfer paper and smaller toner particle size. However, XR is grainiest among the four imaging systems tested. The density fluctuation of the XR is 4 times greater than MR film. This greater density fluctuation may be a result of the high grain pattern contrast since the effective grain sizes are as small as MR film. 3) The concept of "signal-to-noise ratio" is applied to the imaging systems in order to obtain results from objective methods correlated with subjective results or visibility. The output density distributions of alumiunm cylinders ranging from 100 to 1,000 μ in diameter are taken as the inputs to the visual system, and σ(D), as noise. Physiological contrast D/ΔD min. is also taken into consideration for XR in which the surrounding density of an object varies with the magnitude of the edge-effect. The result reveals that XR provides a higher ratio than MR film for aluminum cylinders smaller than 1,000 μ in diameter. XR differs the most from MR film in the radio at 700 μ diameter or so where XR is considered to show the best visibility of calcifications. 4) Visibility is defined here as the adiliity to detect minute calcification in mammary carcinoma ranging 90〜400 μ in diameter, and comparison of visibility between XR and film is made with following factors ; exposure time, radiographic density and geometrical condition. As a whole, XR is superior to film in visibility at both 30 kVp providing additional detectability for smaller calcification by roughly 20 μ in diameter. When visibility of XR is related to varing exposure time, it is far less sensitive than film, but on the contrary more sensitive than film to the radiographic density. Optimum density for XR is very low as 0.3 were the XR print provides the maximum visibility, while 1.5 for film at 7,000 lux rear illumination. XR is less affected by penumbral effects than film, since the visibility of XR depends much more on the contrast than the shapness for the object larger than 100 μ in diameter. It is concluded that the 125 system satisfied an indespensable necessity of mammography for finding small objects in the breast which a patient or her doctor could not find.
In this article, in the first part we discussed about basic point of ^<111>In-DTPA, and in the second part described two cases, in each case we used both ^<169>Yb-DTPA and ^<111>In-DTPA. ^<111>In-DTPA had chemical property of weak acidity (pH 6.0〜6.5) and was stable in human bodies because of good chelating nature. Effective half life of ^<111>In-DTPA was 16 hours, i.e. 6 hours shorter than that of ^<169>Yb-DTPA. It seemed to be slightly longer than that which had been rported. Imaging by using ^<111>In-DTPA and ^<169>Yb-DeTPA were almost the same, though there was a month of duration between the use of two pharmaceuticals. So we concluded that interpretative criteria of ^<169>Yb-DTPA cisternography could be applied to ^<111>In-DTPA cisternography.
RI data processing system is constructed from central processing TEAC-16 which has the performance of 16 kW core memory and cycle time 660 nsec, combined the scintillation camera (Nuclear Chicago Pho/Gamma HP) on line. The matrix of a digital image is used 64×64,and one image transmission time to a magnetic tape is 400 msec. To get better the corrected RI images than the original ones, we are using some correction techniqes as follows. (1) Correction for a counting loss due to a resolving time which occurs in position computation of the camera, in A-D conversion and in memory storage. (2) Correction for a nonuiform sensitivity of the camera detector. (3) In order to eliminate the noise which caused by the stastistical fluctuation of RI decay, we are using 25 points weighted average. (4) In order to correct a blurred image which is due to the poor resolving power of the camera detector, we are using conrast enhancement by the iterative approximation. From these studies it was found that the iterative approximation must be terminated two times to eliminate the noise emphasis.
The gonad exposure dose of radiation in a chest radiography is far lower than that in other radiographies such as a gastric fluoroscopy, a cholecystgraphy, a pelvic roentgenography, & c. However, carried out to the masses by the group examinations, the chest radiography predominates in the rate of the genetically significant dose of the nation. Our department is possessed of five X-ray cars, on which about 72,000 chest radiophoto-graphs are taken annuually. So we have recently developed a gonad protector, which can be operated easily and efficiently, in order to reduce the gonad exposure dose as well as possible and to drive away the citizens'feeling of unrest about the radioactivity. In this paper we describe the protector and the experimental result of its protective effect.
(1) The radiological process and clinical evaluation of radiological image quality were shown and discussed. (2) From the clincal standpoint of view, criteria for evaluation of radiological image quality depend on the aim of diagnosis, location examined. Most suitable recording system should be selected to fit the criteria. (3) Exposure dose is to be reduced considering to keep the appropriate image quality for correct diagnosis. Since grainess tend to deteriorate the image quality, increase in speed of screen is preferable than increase in speed of film. For the examination of the hip of children and the pelvis of pregnant women, however, the recording system of the highest speed is required, considering dose reduction.
Granularity of a screen-film radiographic system was assessed physically and visually by examinig various combination of films and screens. We pointed out that the dominant factor which affects granularity of the system was quantum mottle, and the contribution of this factor to total radiographic granularity can be estimated as about 60%. Then, we tried to get a new high-speed radiographic system of high image quality. The system was designed by making use of green-emitting intensifying screens which contain rare earth phosphors, and combining these screens with a green-sensitive orthochromatic medical X-ray film. The new system provides maximum light emission which can be absorbed efficiently into emulsion layers and enables reduction of X-ray exposure to 1/5 or even to 1/10 in comparison with normal system. The new system gives entirely equal diagnostic information or it gives superior image quality compared with the conventional system.
Several factors are considered nowadays to dominate the image quality of radiographs. Blurs and noises are the most important among them in relation to radiographic equipments. Modern methods to evaluate these two factors are introduced, namely, modulation transfer functions for blurs and signal to noise ratios for noises. Some examples of actual blurs and noises present in radiographs are analised by these methods. Recent progresses and future developments of radiographic image quality are also discussed from the standpoint of radiographic equipments.
In a field of radio-graph, it is important to evaluate quantities of this for diagnosticians. The quantities of a radio-graph are generally sorting a spatial frequency band-width, a signal-to-noise (S-N ratio) and a direct-range. The thresholds of the band-width and the S-N ratio which have been evaluated by visual system of each diagnostician, on individual diagnostic object in the radio-graph, are investigated respectively. On conclusions based on statistics, it is clear that the band-width and the S-N ratio required for the misread probability to be less than 0.5% are approximately 3〜4 line pair/mm and 20〜25 dB. Additionally, the access-time of reading the objects is quasi-hyperbolically increased as the S-N ratio is decreased.
The image quality of radiograph is made of the gradation, sharpness and granularity. In this paper, we describe the sharpness and granularity. In the item of sharpness, the modulation transfer functions of clean-up effects of clean-up equipments are described. In the item of granularity, characteristics of reversal treatments are described. X-ray film emulsion consists of silver halide grains of various sizes. Larger silver grains of higher sensitivity are teken away by bleaching. Therefore, the size of reversal silver grains is smaller than that of negative silver grains. The granularity is improved by reversal development. Therefore, the image guality of reversal development have finer details.