A highly sensitive x-ray image pickup device has been developed based on the scintillator and photoreceptor conversion method for a radiation image and the xerographic technique. As compared with the conventional x-ray film with the combination of the phosphor screen, a high sensitivity of nearly 10 times has been obtained. The experimentally made camera houses a scintillator-photoreceptor image plate together with a corotron charger as well as a toner developer, and a x-ray photograph is obtainable in a short time.

An enhanced mammographic imaging process has been developed which is based on the conventional powder-toner selenium technology used in the Xerox 125/126 x-ray imaging system. The process is derived from improvements in the amorphous selenium x-ray photoconductor, the blue powder toner and the aerosol powder dispersion process. Comparisons of image quality and x-ray dose using the Xerox aluminum-wedge breast phantom and the Radiation Measurements Model 152D breast phantom have been made between the new Enhanced Process, the standard Xerox 125/126 System and screen-film at mammographic x-ray exposure parameters typical for each modality. When comparing the Enhanced Xeromammographic Process with the standard 125/126 System, a distinct advantage is seen for the Enhanced equivalent mass detection and superior fiber and speck detection. The broader imaging latitude of enhanced and standard Xeroradiography, in comparison to film, is illustrated in images made using the aluminum-wedge breast phantom.

The development of a large-area amorphous silicon array for x-ray imaging is described. The array comprises pixels made up of amorphous silicon transistors and photodiode sensors with a pixel-to-pixel pitch of 450 micrometers . With a format of 512 X 560 pixels, the array has an area of 23 by 25 cm² making it the largest self-scanning, solid-state, pixelated imaging device ever reported. The first diagnostic x-ray images from such a large area device are demonstrated and a general review of the current state of this technology is given. The properties of such arrays are summarized and future anticipated developments discussed.

A prototype portable gamma ray camera using 32 X 32 channels was developed. An experimental 3 X 3 sub-array of 5 mm X 5 mm CZT detectors was fabricated for use in system checkout and to investigate the applicability of CZT imaging arrays to nuclear medical imaging. Experiments were carried out to make a direct comparison of the imaging capabilities of the CZT sub-array with a state-of-the-art Anger camera. In a linespread study using a Tc-99m source embedded in a tissue equivalent absorber, contrasts of 9.5 for the CZT array and 3.4 for the Anger camera were observed. In a dynamic imaging experiment, the CZT imager appeared to have comparable resolution to and be somewhat more regular than the Anger camera.

By converting the absorbed X-ray image directly to an electrical video signal, the x-ray sensitive video camera offers improved resolution and reduced veiling glare over a conventional x-ray image intensifier for medical fluoroscopy. Unfortunately, currently available x-ray sensitive video cameras are limited to a 1' field of view and poor quantum efficiency. We are developing an x-ray sensitive vidicon for medical use which will have a large field of view (5' or more) and a thicker amorphous selenium target with a quantum efficiency >70%. Due to the larger potential required to bias the thicker a-Se target a problem in maintaining a stable surface potential by means of a scanning electron beam is encountered. This stability problem is overcome by the addition of a suppressor mesh.

We have developed a 4200 scanning lines TV camera using a 2-inch diameter, electrostatic focus and electrostatic deflection type SATICON^TM image pick-up tube which have been newly developed for real-time digital radiography (DR) system. We obtained 23% in AR value at 2600 TV line and 47.4 dB in S/N value at signal current 1200 nA in 4000 lines mode.

We have identified two new noise sources in the real-time portal imaging chain which cause the temporal noise to be higher than the spatial noise. When a vacuum tube camera is used for portal imaging with pulsed linear accelerators, a horizontal banding artifact due to beam pulsation as well as an interface artifact (zig-zag type variation in intensity along vertical direction in a single frame) appears in the images. Frame transfer CCD cameras are only sensitive to the interface artifact. We found that noise due to the X-ray beam pulsation artifacts dominates over other temporal and spatial noise sources in real time portal images, which results in a signal independent SNR. However, when 256 frames are averaged, the pulsation artifact averages out. Further, we found that long term drift in the electronics also contributes excess temporal noise. The SIT camera takes 3 - 4 hours to stabilize its dark current and the frame grabber requires a similar time to stabilize its reference voltages. When sufficient time is allowed for the system to stabilize, and a continuous X-ray source is used, spatial and temporal noise in real time portal images are found to be equal at the 1 standard deviation level up to 256 added frames.

Gamma camera technology has evolved during the past two or three decades and is now a mature product. This paper will show that important gains can still be made at the detection level by modifying some optical components and by considering a new description of the physical phenomena. The first design modification to the detector would be to match the indices of all optical materials, from the crystal to the photomultiplier tube's window. The second and equally important point where improvement is possible is in the elimination of the spatial/spectral distortions. We will show that a complete description of the scintillation process is only possible when taking into account the depth-of-interaction (DOI) of the gamma in the crystal. Finally, the spectral contamination caused by gamma rays undergoing Compton interaction either in the object or in the detector itself is addressed by the Holospectral imaging technique. In this approach, events from the whole spectrum are accepted (as opposed to the energy windowing presently in use) and formatted into a series of energy frames. Statistical analysis is then performed on these multidimensional data to segregate object-related variance and contamination.

We are developing an x-ray microtomographic imaging system ((mu) CT) for imaging small objects at very high (approximately 25 micrometers ) spatial resolution. The detector for this system consists of a CCD array coupled to a phosphor screen through a fiber-optic faceplate. For the purposes of signal and noise analysis, this system is modeled as a multi-stage cascaded imaging system consisting of: (a) conversion of x-ray quanta to optical quanta in the phosphor; (b) collection and transfer of optical quanta from the phosphor to the CCD; and (c) detection of optical quanta by the CCD. We use the model of Rabbani et al. for cascaded systems to theoretically calculate the detective quantum efficiency (DQE) as a function of spatial frequency. We have developed the theoretical basis of a spatial-frequency dependent nomogram in terms of the system DQE. This approach is used to identify any sources of image degradation, and to make optimal design decisions of system parameters such as optical gains or numerical apertures. Using this approach, we show that the spreading of optical photons in the phosphor screen is the most significant factor degrading the MTF.

A prototype of a clinical scanned-slot digital mammography imaging system has been developed, which demonstrates better contrast sensitivity and latitude than current state-of-the- art film-screen mammography systems. The detector consists of a Gd₂O₂S:Tb phosphor screen coupled via a 2-to-1 demagnifying fiber-optic taper to two time-delay integration (TDI) charge-coupled device (CCD) image arrays. Images are obtained by scanning the 4.0 mm wide by 21 cm long detector across the image field. An 18 cm by 21 cm image contains 2900 by 4032 pixels, of dimension 62 micrometers X 52 micrometers at the detector. Currently, images are produced in 7.8 seconds using a 40 kV tungsten-target spectrum with a total heat load of 50 kJ, giving a mean glandular dose of 0.85 mGy (85 mrad) to a 5 cm thick 50% glandular, 50% adipose breast. The detector has a limiting resolution of 9.5 lp/mm. A clinical version of this prototype, which incorporates several improvements, is being constructed.

A preliminary study was conducted to investigate the feasibility of using high resolution computed radiography techniques for dentomaxillofacial imaging. Storage phosphors were cut into various sizes and used with an experimental laser scanning reader for three different imaging procedures: intraoral, cephalometric and panoramic. Both phantom and patient images were obtained for comparing the computed radiography technique with the conventional screen/film or dental film techniques. It has been found that current computed radiography techniques are largely adequate for cephalometric and panoramic imaging but need further improvement on their spatial resolution capability for intraoral imaging. In this paper, the methods of applying the computer radiography techniques to dentomaxillofacial imaging are described and discussed. Images of phantoms, resolution bar patterns and patients are presented and compared. Issues on image quality and cost are discussed.

A large area, flat panel detector is being investigated for digital radiological imaging (radiography and fluoroscopy). The detector consists of an x-ray sensitive photoconductor to interact with x-rays and convert the absorbed energy to electron-hole pairs. The released charge is collected and stored on pixel electrodes and subsequently is read out electronically with an active matrix, i.e. a two dimensional array of thin films transistors (TFTs). The basic properties of the detector based on the characteristics of the photoconductor, the active matrix and the external charge amplifiers are analyzed.

Dual-energy X-ray absorptiometry (DXA) is one of the bone densitometry techniques to diagnose osteoporosis, and has been gradually getting popular due to its high degree of precision. However, DXA involves a time-consuming examination because of its pencil-beam scan, and the equipment is expensive. In this study, we examined a new bone densitometry technique (CR-DXA) utilizing an X-ray imaging system and Computed Radiography (CR) used for medical X-ray image diagnosis. High level of measurement precision and accuracy could be achieved by X-ray rube voltage/filter optimization and various nonuniformity corrections based on simulation and experiment. The phantom study using a bone mineral block showed precision of 0.83% c.v. (coefficient of variation), and accuracy of 0.01 g/cm², suggesting that a practically equivalent degree of measurement precision and accuracy to that of the DXA approach is achieved. CR-DXA is considered to provide bone mineral densitometry to facilitate simple, quick and precise bone mineral density measurement.

A laboratory quantitative CT scanner capable of producing high-resolution images in all three dimensions has been developed. The system uses an x-ray image intensifier (XRII), optically coupled to a time-delay integration (TDI) CCD to obtain low-noise, high-resolution projections from many angles around a rotating sample. The scanner operates in two modes, producing either a single, transverse image through the sample or a three-dimensional image of the sample volume, over a field-of-view (FOV) ranging from 4 to 12 cm. The performance of this quantitative CT system has been characterized with respect to accuracy, precision, and spatial resolution. The average accuracy in attenuation measurements was +/- 0.01 cm^-1 (RMS). Measurement precision varied with voxel size and x-ray exposure, from +/- 0.01 cm^-1 to +/- 0.03 cm^-1. Limiting spatial resolution also varied with scanner FOV, ranging from 2.8 mm^-1 to 1.2 mm^-1 for the 4 and 12 cm FOVs, respectively. Applications of the volume CT scanner in research tasks using live animals and in vitro preparations are discussed.

We have developed a CT scanner with high temporal and spatial resolution which can be used to acquire dynamic images of objects undergoing periodic motion. Our system comprises of an x-ray image intensifier (XRII) optically coupled to a linear photo-diode array (PDA) camera. The XRII has been modified to vary electronically the magnification of the image continuously over fields-of-view (FOV) ranging between 8 and 24 cm, and thus increasing the resolution from 1.4 mm^-1 to 3.8 mm^-1. In this way, we can select a magnification which maximizes the image resolution for a given object.

The construction of the imaging system includes: (1) replacing the linear detector of the CT scanner with an image intensifier coupled to a TV camera, (2) modifying the gantry to mount the image intensifier, (3) replacing the system computer by a PC, (4) designing and constructing the interfacing and data acquisition system and (5) developing software for system control and data acquisition. The system consists of a x-ray tube and an image intensifier that are separately mounted on a gantry. The tube-detector set can be rotated over 360 degree(s) in the gantry. Two sets of images acquired with this imaging system indicate that two types of distortion occur in image intensifiers, S distortion and pincushion distortion. In the future, these two types of distortions need to be corrected prior to three-dimensional (3-D) reconstruction.

We present a method for reconstructing magnetic resonance (MR) images from data acquired using echo-planar imaging (EPI) techniques. All data were acquired from a commercial scanner, the 1.5 Tesla Picker Vista HPQ MR imaging system, equipped with a special, high- performance, gradient system. Blipped echo planar imaging (BEPI) was performed, with and without digitizer pausing during data acquisition. Both sinusoidal and trapezoidal readout gradients were programmed and tested. Samples obtained from the gradient amplifier current monitors were used to calculate the approximate position of every sample obtained in the spatial-frequency (k-space) plane. A convolution function with compact support int he k-space and good rolloff in the image domain was used to resample the data onto a lattice permitting the use of fast transformation methods to the image domain. Strong ghosting was observed in the resulting images due probably to static magnetic field variation, gradient asymmetry and echo asymmetry between data lines. A piecewise-linear function was used to model the introduced ghost and hence to remove pixels in the reconstructed image which were determined to be spurious. Initial results are promising.

Although improved video camera sensitivity has been responsible for reducing the radiation exposure rate in conventional fluoroscopy substantially over the last two decades, considerable further improvement is possible. Over the same period two methods for reducing fluoroscopic exposure have been implemented by various researchers: pulsed X-ray irradiation and progressive video acquisition of the image intensifier output at low frame rate with exposure per frame comparable to conventional fluoroscopy; and continuous irradiation with a combination of low exposure rate, high detector gain and X-ray beam filtration. Neither has come into widespread clinical use. This paper proposes a model of fluoroscopic patient exposure and compares pulsed fluoroscopy with other methods of exposure reduction. The implications of this model for fluoroscopic exposure rate optimization are discussed.

In a TV fluoroscopic system it is generally accepted that there exists somewhat of an inverse relationship between lag and noise integration. This paper will demonstrate techniques used to reduce the appearance of quantum noise while maintaining acceptable lag performance in systems utilizing Plumbicon^TM camera tubes.

A design for a dual-energy Kinestatic Charge Detector (KCD) with segmented charge collection fingers is discussed. The front segment of the KCD charge collectors will produce a digital low-energy image and the back segments will produce a digital high-energy image. A gap between the front and back collectors acts as a mid filter to increase the separation between the mean energies absorbed in the front and back segments. This dual-energy KCD design was optimized by using computer simulations to maximize a figure of merit defined as the square of the signal-to-noise ratio divided by the average absorbed dose. The optimal KCD parameters are presented for a dual-energy KCD designed for mammography. Preliminary experimental data are given for a small non imaging dual-energy KCD research detector.

An experimental study in the area of electronic detector technology for medical imaging applications is in progress, aimed at improving kinestatic charge detector (KCD) performance parameters such as spatial, contrast and temporal resolution. The purpose of this study is to utilize extremely high pressure gas imaging detectors, operating in the saturation mode, aimed at the reduction of the ionic signal pulse width thereby improving spatial resolution.

The spatial resolution of the Kinestatic Charge Detector (KCD) for digital radiography is limited by mobility dispersion when the detector operates with noble gases such as xenon or krypton. The magnitude and dependence on drift distance of the peak widths of ionic signal pulses produced in the KCD provide a measure of mobility dispersion. These parameters have been measured in a KCD filled with krypton gas at a pressure of 60 atm, and in the same gas alternately doped with 1.7% of each of the following amine additives: ammonia, methylamine, dimethylamine and trimethylamine. The ionization potentials of these dopants are 10.2, 9.0, 8.2 and 7.8 ev, respectively. While the undoped medium exhibited significant mobility dispersion, all four of the amine-doped media showed dramatic reduction or elimination of mobility dispersion.

This paper describes experiments performed to determine image quality of three x-ray imaging systems designed for stereotactic breast needle biopsy: A system developed in-house, a LoRad DSM and a Fischer MammoVision. All systems have been successfully used to perform stereotactic breast needle biopsies and preoperative needle localizations. They all successfully decrease the time for stereotactic needle biopsy procedures. The systems are being characterized with respect to image quality for a variety of mammographic x-ray screens. The sensitivity can be as high as 96 ADU/mR and as low as 28 ADU/mR, depending on the phosphor screen and the gain used. The response is linear with respect to x-ray exposure. The highest spatial resolution found was on the order of 10 lp/mm, which is the Nyquist frequency for systems with 1024 pixels at a linear field of 5 cm. The noise at zero spatial frequency was found to be mainly determined by x-ray photon noise.

A liquid nitrogen cooled CCD TV camera from Astromed, Ltd. has been used for quantitative X-ray medical imaging. The CCD camera is coupled to a Kodak Lanex Regular X-ray intensifying screen with a 5:1 macro lens for bone mineral densitometry of the femur of a rat for a study of the development of osteoporosis. As a feasibility study of the use of the CCD for mammography, a 2:1 macro lens has been used to couple the CCD to a clear CsI(Tl) crystal, 100 mm in diameter and 3 mm thick. The spatial resolution and quantum efficiency of the system is significantly improved by replacing the Lanex Regular screen with the CsI(Tl) crystal.

Advanced multiple beam equalization radiography (Amber) has been successfully applied to chest radiography. More recently, the applications have been extended to mammography. The Amber chest unit (Oldelft, Delft, The Netherlands) controls the local X-ray exposure to the patient by means of a feedback loop consisting of a number of detectors in front of the film cassette and the same number of absorbers in front of the X-ray tube. The detector readouts and a predefined compression curve determine the position of the absorbers, while the patient is being scanned by means of a horizontally oriented fan beam. As a consequence, the multiple beam equalization technology has introduced new concepts such as beam profile, compression curve, number of absorbers, and detector weighting function to projection imaging. In order to optimize these different parameters we have developed a computer program, which simulates the multiple beam equalization techniques. Conventionally exposed films are laser scanned resulting in a matrix of optical density values. The program calculates for each pixel the X-ray transmission. These X-ray transmission values are the basis for the simulations with varying beam profile characteristics (i.e. the intensity distribution of the X-ray beam of a channel in horizontal and vertical direction), compression curves, number of channels, detector weighting functions and H&D film curves In order to accurately simulate a particular exposure, the program can be calibrated using optical density and X-ray dose measurements on a conventional X-ray unit or on the Amber unit.

Several different test protocols were used to measure the sensitometric response, the modulation transfer function (MTF), the veiling glare and the Wiener spectrum of two x-ray image intensifier (II) tubes. These data provided the means to calculate summary measures of imaging performance, i.e., the noise equivalent quanta, NEQ, or the detective quantum efficiency, DQE, as a function of spatial frequency. Results are presented to show the differences between an older versus a newer generation II tube, i.e., DQE equals 0.3 +/- 0.03 and 0.6 +/- 0.06 at 0.5 lp/mm, respectively. The eventual goal of this work is to achieve some consensus on methodology for these measurements and to validate the use of algorithmic observers in quantitating imaging performance in the clinical environment.

A computational approach is being developed for the evaluation of mammographic imaging system performance. This approach takes into account both the spatial frequency properties and the x-ray spectral characteristics of the system being evaluated. The initial version of the program that implements the approach has been used to evaluate a conventional mammography source assembly for several breast thicknesses, and to compare the conventional tube and filter combination to alternatives that have been suggested for the imaging of breasts that are thicker or more dense than average. It has also been used to study the effect of varying the thickness of the molybdenum filter in the conventional system. The parameters calculated include contrast, average glandular dose, tube load, and a figure of merit, SNR²/Dose. The calculations confirm the strong dependence of system performance on both tube potential and breast thickness for the standard system, and indicate that alternative designs can improve performance in the imaging of thicker or more dense breasts. The study of filter thickness shows that, of the four parameters calculated, only tube load is strongly affected by filter thickness.

The x-ray excited emission spectra of some well-known phosphor materials is examined using different x-ray beam qualities. Very thick powder samples and thinner coated screens are examined. It is observed that the emission spectra are influenced by the x-ray beam quality used if the samples are very thick. A simple light diffusion model is developed and used to understand the observed effects both qualitatively and quantitatively. It is found that very small changes in the total reflectance of the powder samples is correlated with observed spectral changes.

In this paper we examine the imaging performance of an experimental mechanically-flexible antiscatter grid for use with computed radiography. Bucky factors, contrast improvement factors, and signal-to-noise improvement factors were computed from transmittance measurements made with 5-, 10-, 15-, 20-, and 25-cm uniform-thickness water phantoms. These phantoms were selected to span the range of scatter fractions found in chest radiography.

High efficiency detection of stimulated emissions from photostimulable storage phosphors requires a specialized class of collector design. In addition to collecting as many stimulated photon emissions as possible, the design must minimize the probability of secondary stimulated emissions. The latter, resulting from the stimulating photons, originally scattered by the storage phosphor, whereby reflection, find a secondary path back to the storage phosphor and strike it at a location other than that of the scanning beam. These secondary emissions are referred to as flare light, and will degrade the MTF of the system. Eastman Kodak Company has developed and patented collector designs that are highly suitable for use in computed radiography scanner systems. The design and performance characteristics of this class of collector design will be presented.

A new computed radiography system is described in which a charged selenium photoconductive plate is exposed to x-rays to create an electrostatic latent image, developed with a luminescent toner, and scanned with a stimulating laser beam to produce emitted light, which is filtered and detected. The resulting electronic signals are processed, and converted to hard copy using a laser film printer. The system is characterized by high x-ray sensitivity and by very high spatial resolution, which makes it particularly suitable for applications such as mammography and bone radiography. The image luminescence is bright and its decay time is extremely short, enabling rapid scanning with an inexpensive laser source. Also, the electronic capture of image data permits enhancement of the displayed contrast of image structures by image processing techniques.

As reported in an earlier paper, the characteristics of a film/screen system for chest radiology based on Du Pont's Ultra-Vision^TM technology were initially designed by means of a digital model of the radiation transfer process. This film/screen system has now been made and its image quality characteristics are described and compared with model predictions.

Based on theoretical considerations and simulations of correlated stochastic noise-like fluctuations Shaw and Rabanni have predicted that the calculation of noise power spectra via the physical autocorrelation function may offer significant signal to noise ratio advantage over more conventional methods. In this paper noise power spectra of actual film-screen systems calculated by the standard direct Fourier transform method are compared with those obtained via the autocorrection function. We confirm that noise power spectra derived from the autocorrelation function are less sensitive to non-stochastic perturbations in the data and thus provide a more accurate representation of the noise characteristics of film-screen systems. This is of great importance when attempting to relate measurements to mechanistic models of the screen and film imaging parameters.

Models for characterizing the signal-to-noise ratio for radiographic imaging systems typically ignore the human interface. In this work, images of a calibrated mammographic step wedge and a very low contrast paper step wedge were made with mammography film-screen systems and with direct x-ray exposures. Large and small density differences between adjacent steps were thus obtained over a wide range of film optical densities. Experienced viewers determined large-area threshold contrast sensitivity as a function of film density and viewbox luminance at constant low ambient illuminance with masking to exclude transmission of bright viewbox light through any area other than that portion of the step-wedge image being examined. Then, at high and low levels of viewbox luminance, threshold contrast sensitivity was determined at four different levels of ambient illuminance ranging from lower to higher than levels ordinarily used in clinical practice. threshold contrast sensitivity with and without masking was determined for viewing on a typical radiographic viewbox at a constant luminance level. The resulting data give strong qualitative support to the conclusion that viewing conditions (viewbox luminance, masking, and ambient illuminance) typically used in clinical practice are insufficient for optimum detection of the diagnostic information that can be recorded and displayed with modern mammography film-screen systems.

Digitized mammograms are used as input to a system of feedforward neural networks for determining the presence of clusters of microcalcifications. Rather than presenting the locations of detected suspected pathologies on the digital image itself, the intent is to produce a transparent overlay marking these possible pathologies for later diagnosis by the radiologist. Current results indicate that this method will in general be more efficient than human observers in locating low contrast objects and clusters of small microcalcifications (down to 50 micron diameter).

Region of interest (ROI) fluoroscopic techniques have the potential for improving image quality and reducing radiation doses. Materials for x-ray beam shaping filters for ROI fluoroscopy are evaluated using a computer simulation which determines their transmission and effect on radiographic image contrast. Also a design for a new 'non-hardening' scanning filter consisting of an array of strips of radiopaque material separated by radiolucent spacings is presented. The array is placed close to the x-ray focal spot and scanned or vibrated so as to blur the image of the strips. Also a new dose spreading strategy based upon ROI fluoroscopy is introduced and is shown to have the potential to eliminate the problem of high patient skin exposures common during interventional procedures. Finally, applications of ROI fluoroscopy to continuously variable zoom or micro fluoroscopy and to peripheral vascular interventional procedures using continuously variable ROI size and shape are considered.

A new laser is developed for medical imaging, with the construction based on the new principles of lasing spectrum operation. The output radiation possesses unusual spectral properties that are investigated experimentally. The advantages of this radiation application for imaging in medical and biological investigations by the methods of microscopy, endoscopy, photography and holography are examined.

Charge-Coupled Devices are used as x-ray sensors. For dental purposes it is important to have an image area of roughly 3 X 4 cm². In case of direct imaging with an MOS Charge-Coupled Device one is restricted to image areas of about 1.5 X 2.5 cm². The reason for this is that in commercially available CCDs one aims at getting a high spatial resolution on a small area. This article will show, that Junction Charge-Coupled Devices do not have this restriction, which makes these devices perfectly suited for dental purposes.

A theoretical model was previously developed to evaluate the relationship between the dynamics of ultrasonic speckle and its underlying tissue. The model is divided into an instrumental part represented by the point spread function (in the far field) of the ultrasonic apparatus and a moving tissue component describing the changing tissue acoustical impedance structure as a function of time. In this paper, a theoretical study of the correlation between various linear transformations of the tissue and the corresponding ultrasonic speckle motion is performed, based on a 2-D extension of the envelope crosscorrelation analysis of a narrow- band gaussian noise. In the linear scan case, obviously, tissue translation generates an identical speckle translation. However, tissue/speckle motion correlation decreases with increasing rotation and/or biaxial deformation; lateral deformation (perpendicular to the beam propagation axis) being much less sensitive. With respect to the transducer frequency, the rotation and the axial deformation of the tissue shows a better relationship with their respective speckle motion at lower frequencies while lateral deformation correlation is independent of the pulse frequency. With respect to beam (pulse) size parameters, tissue/speckle correlation decreases with rotation when a wide ultrasonic beam is used while the axial deformation correlation decreases with the axial duration of the pulse. This study sets the ground for the development of an ultrasonic strain gauge particularly useful for the assessment of biomechanical soft tissue properties based on speckle tracking.

An optical pseudocolor specifications of a radiographic image utilizing phase modulation method is suggested for medical diagnosis. With this suggestion the illness can be diagnosed not only referred to the color but also to the chromaticity coordinates of the affected part of the color image taking from a patient. This paper offered a theoretical method to calculate the chromaticity coordinates based on the effective relief thickness corresponding to the affected part of the patient, the result of calculation is in agreement with the gamut observation.

This paper proposes three methods for reconstructing magnetic-source biocurrent distribution. These methods are more effective than the conventional pseudo-inversion-based reconstruction when the signal-to-noise ratio of measured data is low. First, a method of estimating magnetic- source-current covariance matrix using the measured-data covariance matrix is presented, and an averaged current squared-intensity distribution is reconstructed using the diagonal terms of the covariance matrix. The use of its off-diagonal terms leads to the second method that can separate magnetic-source activities correlated to each other from the uncorrelated activities. The third method is the Wiener reconstruction of current distributions based on the estimated source covariance matrix. Results of computer simulation demonstrate the effectiveness of those three methods.

Medical image transmission technique with holographic scanner is described, in which the calculation for making an holographic scanner, such as the width and the arc-length of the scanning area, the scanning radii, the maximum deviation of the scanning curve from a straight line, scanning speed, resolution etc. The opto-electronic converter and the image transmission system is described. A simple experiment shows that this method for medical image transmission is feasible.

Panoramic thermography (PT), a kind of developmental thermography (DT), is a unique thermographic imaging technique, which enables us to capture a continuous thermogram even over the entire surface of a subject. This paper presents the method of PT and discusses the special advantages of this technique. The advantages specific to PT are as follows: (1) Continuous temperature distribution can be captured. (2) The coverage of the panoramic thermogram is variable even over the entire surface of a subject. (3) Image enlargement along the developmental axis is possible. (4) Pattern resolution in PT increases with the enlargement of the panoramic thermogram. (5) Continuous scanning along the center axis in PT lead to high fidelity of the thermogram over the whole coverage. PT is expected to lead an epoch- making thermographic imaging technique.

Multiple aspect thermography (MAT) is a kind of developmental thermography. MAT was designed in order to supplement the shortage of the number of coverage aspects in triple aspect thermography (TAT). TAT allows simultaneous display of numbers of thermograms on various selected aspects of the subject in CRT frame. This paper reports on MAT methodology and discusses some aspects of the problems and the special points of this technique. The data on the thermal images on the entire subject can be recorded in one revolution of the subject. After the measurement is completed all over the subject, thermograms of any selected aspects is composed in a CRT frame in multiple image arrangement by recalling the recorded thermal data using the multi-video processor. Strictly speaking, based on the thermography on the moving target in MAT, distortion and smoothing of the thermal pattern in MAT are essentially unavoidable. The shorter the frame time of the thermocamera is, the less the problems in MAT can be reduced. However, the problems in MAT are negligible under the usual condition for clinical application of MAT.

In order to compensate for the weak points in conventional infrared plane scanning thermography (PST), the authors' efforts toward the technical development of new thermographic imaging since 1968 has led to the following three kinds of developmental thermography (DT): (1) triple aspect thermography (TAT), (2) multiple aspect thermography (MAT) and (3) panoramic thermography (PT). This paper presents the technique for TAT and discusses some aspects of this technique. In TAT a pair of plane surface mirrors are located at either side of a subject at a selected angle to the subject's median plane to reflect the infrared emission from each lateral surface of the subject into the thermocamera. The thermocamera scans the frontal surface directly and both lateral surface of the subject through the reflectors. Consequently, the thermograms of the three different aspects of the subject can be taken simultaneously and displayed in the CRT frame of the thermography in symmetrical arrangement. The viewing angle and coverage of the lateral images are variable according to the reflector angle to the subject's median plane. TAT enables us to observe thermal phenomenon over a wide coverage of a subject surface at one time, especially thermal trace with time on the three aspects of a subject.