For the purpose of the echo pattern classification at maxillofacial regions, 99 samples histopathologically examined at the Hospital attached to Nihon University School at Matsudo were classified by ultrasonography.
The classification was to analyze the ultrasonographic images of each diseases into the following seven factors.
1. Shapes
2. Contours
3. Borders
4. Internal echoes
5. Boundary echoes
6. Posterior echoes
7. Acoustic shadows
As a result, lymphadenitis showed the hypoechoic homogeneous solid pattern with the unclear contours. It is also recognized that the internal echoes and boundary echoes of mixed pattern strong appeared irregulary on the malignant tumor.

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Orthopantomography which is currently used extensively in clinical practice developmented by Paatero in 1961.In 1939 Heckmann first described slit X-ray beam techniqe for radiography curved surface. It is suggested that the principle of the currently used orthopantomography might come from this curved surface tomography method.A number of papers have been published which attempted to elucidate orthopantomography theoretically.
Welander derived a theoretical formula in 1974. His formula agrees with that given by the present authors as well as that given by Tammisalo in respect to mathematical expression.
The size of the blurring image can be estimated by these formulae when the size of an object can be described by rectangle function, although the size of output image can't be calculated when the size of an object is the function of continuous distribution. By theoretical analyses on orthopantomography we have succeeded in deriving a theoretical formura which is almost satisfactory, and in demonstrating it in a experimental study.
Welander derived the following equation on the relation between the real size of an object(d_o) and that of image of the object(d_f) reflected on the film.
Here each element stands for:
R; the radius of the film, r; the radius of the object,
w_o; angular velocity of the X-ray beam or the angular velocity of the object
w_f; the angular velocity of the film, b'_f; the width of beam on the film
D; the distance from the tube target to the object, A; the distance from the target to the film.
Welander's equation (1) can be expressed as follows
Here W is the angle formed by the rotating center and the points where the X-ray beam width crosses the circumference of a circle on which the object is placed.
According to the equation (2), when the slit width becomes closer to infinitely small one, namely b'_f→0, the output image size can be expressed as a multiple of d_f by the factor of Rw_f/rw_o without any blurring components. When the size of an object becomes infinitely small, namely d_o→0, the equation (2) corresponds to Line Spread Function (LSF).
In other words, according to the equation proposed by Welander as well as by authors, the size of the blurring image of an object is expressed as the sum of LSF and the enlarged components which are determined by the rotating radius of an object and film. Mathematically this is a theoretical approximaoe equation although incomplete.
By theoretical analysis of image production of orthopantomography, we have succeeded in deriving our theoretical equation as described below.
Here, each element stand for; d_f(x); X-ray intensity distribution function of the output image,
d_o(x); X-ray intensity distribution function of the object,
R and r; radius of the film and that of the object respectively, w_f and w_o; angular velocity of the film and that of the object (or X-ray beam)
W; angle formed by the points where the X-ray crosses the circumference of the radius r and the rotating center,
b'_f; slit width on the film,
*; convolution integral,
II; rectangle function,

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The optimum X-ray energy distribution in intra-oral radiography was investigated by computer analysis. In this investigation, a simplified mathematical model of oral tissues was used in order to make quantitative evaluation of the contrast producability of X-rays depending on photon energy.
This computerized model consists of three parts of oral tissues such as cortical bone, cancellous bone and soft tissues. The thickness of cortical and cancellous bone were variable in this model in order to correspond to any part of oral tissues. Radiographic cotrast produced by adding cancellous bone as a signal at each thickness of cortical bone with 3cm thick water was calculated under various X-ray energy and exposure. In this model, an available diagnostic area in which X-ray image had resonable contrast and density for interpretation was considered for the X-ray energyevaluation.
Practical optimization of X-ray energy distribution was also investigated using rare earth elements as a radiation filter.
The results were as follows:
1) This computerized model was useful not only for quantitative investigation of the optimum X-ray energy distribution but also for quantitative diagnosis.
2) Changes of the available diagnostic area depending on various X-ray energys were compared. In this comparison, these areas of 25, 35 and 40 keV monoenergetic X-rays were similar to those of conventional wide-range X-rays generated with 30, 60 and 90kVp tube voltage respectively.
3) The use of monoenergetic X-rays reduced the skin exposure by 50 percent and the total absorbed energy by 30 percent as compared with the use of conventional X-rays.
4) Photons in the 28 to 40keV range were best suited for intra-oral radiography from the view point of the image forming quality and the radiation protection.
5) X-rays distributed widely within this range were more suitable to increase the latitude than monoenergetic one.
6) In practical optimization of X-ray energy distribution, an aluminum filtration was effective for conventional X-rays generated with 50-55kVp tube voltage, but for more high kVp region, filtrations of rare earth elements were more effective.
7) Using a sheet of 0.25mm thick neodymium as a filter, reduced the skin exposure by 50 percent and slightly increased radiographic contrast as compared with using 2mm thick aluminum filter at 60kVp conventional X-rays.
8) It is desirable to increase the out put of conventional dental X-ray equipment about two or three times and to make reasonable filtration of the rare earth elements.

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The first study on double-contrast arthrotomography of TMJ was reported by Westesson, Sweden (1982). There has been no report on this from other institutes. We have obtained good results on this clinical study for the double-contrast arthrotomographic examination of TMJ.
The evaluation period was July, 1984 through November, 1985. 44 cases were examined, which clinically diagnosed as arthrosis of TMJ. 2 cases were evaluated as normal arthrogram, and 42 cases were diagnosed as anterior disk displacement. Any clinical symptom was found for all of the cases of anterior disk displacements in TMJ.
Of the cases of anterior disk displacements, 22 cases were found anterior disk displacement with reduction, one of these cases was found the perforation in the posterior attachment. 20 cases were anterior disk displacement without reduction, 3 cases were found the perforation in the posterior attachment and the disk.
On the disk configurations, of 22 cases with anterior disk displacement with reduction, 12 cases were biconcave and 10 cases were enlargement of posterior band. Of the cases without reduction, 13 cases were biconvex and 4 cases were even thickness. The disk configurations of 2 cases were not evaluated because of the perforation.
2 cases, over 40mm opening mouth and clinically diagnosed as no limitation of mouth opening, were found anterior disk displacement without reduction.
Using the airway pressure manometer, injection pressure of negative contrast medium were standardized 30 cmH₂O for the upper joint compartment in the closing and opening mouth. For the lower joint compartment, 30 cmH₂O in the opening mouth and 40 cmH₂O in the closing mouth.
To standardize the injection pressure is not only able to minimize the technical differences by operators, but also to compare among arthrograms each other under the same conditions. Therefore, this method brings a good and constant arthrograms.

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The ICRP Publication in 1982 recommended that “When using panoramic equipment, the alignment of tube (with slit beam-limiting device) and film shield (again with its slit) is critical, and this shall be checked at suitable intervals.” However there was no simple method for estimating the increased radiation dose of a patient from incomplete slit alignment in rotational panoramic radiography.
The purpose of this investigation was to obtain the data on the integral absorbed dose (energy imparted) received by the patient when using rotational panoramic radiography at several different incomplete slit alignments. The integral absorbed doses were calculated by the energy fluence method. The alignment of the first slit and the second slit were checked using dental film and a fine wire. The dental films were placed on the second slit either on the side nearest to the X-ray source or on the side behind the slit, and a fine wire was positioned on the film surface. The densitometric traces were measured by means of a microdensitometer in a direction perpendicular to the slit image. The X-ray intensity distribution of the first slit and second slit was obtained by determining the film density when the film was place in front of and behind the second slit, and applying H-D curves.
The results were as follows:
1) Using rotational panoramic radiography with incomplete slit alignments, the patient exposure dose should be increased from 1. 2 to 2 compared with complete alignment.
2) The increased radiation dose can be estimated by the following expression
In the second slit position, X₁ is an area of X-ray intensity distribution from the first slit and X₂ is a similar value of the second slit when slit alignment is complete, similary X'₁ and X'₂ are the values obtained with an incomplete slit alignment. The value of k is a valiable factor of beam quality dependent on the kVp.

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The purpose of this paper is to evaluate the newly composed Image Processing System as a method for analyzing radiographic trabecular pattern of dental films objectively by use of First Fourier Transform (FFT).
In this Image Processing System, TV-camera was used for data sampling of radiographic images of alveolar trabecula of dental films. These sampling data were digitized and memorized in IMAGE MEMORY UNIT (IMU-6008). These digitized data were prepared by Low Cutoff Filter to remove TREND and by HANNING WINDOW FUNCTION for reproduction. Then the two dimensional Power Spectra which reflected the information of trabecular pattern were selected by image reconstruction used Band Pass Filter.
The following results were obtained.
1) In this Image Processing System, the optical resolving power of TV-camera was less than 8.0LP/mm in spatial frequency. The linearity of the film density and the brightness were obtained in the range of density from 0.68 to 1.80.
2) Pretreatment by TREND and HANNING was useful for analzing of the data.
3) The radiographic information of alveolar trabecular pattern of dental films could be expressed as the sum of Power Spectrum between 0.5 and 3.0LP/mm in spatial frequency.
4) Clinical application of this Image Processing System were used for analyzing radiographic alveolar trabecular pattern of the patients with renal osteodystrophy. Radiological changes of trabecular pattern were classified into 5 groups based on the value of Power Spectra.

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