High-Spatial-Resolution Medical-Imaging System Using a HARPICON Camera Coupled with a Fluorescent Screen

Abstract

A high-sensitivity HARPICON camera was developed for medical X-ray imaging using a fluorescent screen. It is an avalanche-multiplication-type image pick-up tube and is 32 times more sensitive than conventional tubes. The camera also has a wider dynamic range than conventional medical-imaging cameras because a maximum output signal current of 2.3 muA is obtained and, in high-illumination-intensity regions, photocurrent is not proportional to illumination intensity. The fluorescent screen is an intensifying screen of the type used for radiographic screen-film combinations in medical examination. An X-ray image on the screen is focused on the photoconductive layer of the pick-up tube using a coupling lens with f/0.65. Experiments were performed using monochromated X-rays at the Photon Factory. An image of a spatial resolution test chart was taken in a 525 scanning-line mode of the camera. The chart pattern of 5 line-pairs mm(-1 )(spatial resolution of 100 mum) was observed at an X-ray input field of 50 x 50 mm. Real-time digital images of the heart of a 12 kg dog were obtained at a frame rate of 60 images s(-1) after injection of a contrast medium into an artery. The images were stored in digital format at 512 x 480 pixels with 12 bits pixel(-1). High-spatial-resolution and high-contrast images of coronary arteries were obtained in aortography using X-rays with energy above that of the iodine K edge; the image quality was comparable with that of conventional selective coronary angiography.

SYNCHROTRON‐BASED ANGIOGRAPHY FOR INVESTIGATION OF THE REGULATION OF VASOMOTOR FUNCTION IN THE MICROCIRCULATION IN VIVO

“…15 This non-synchrotron system has been used successfully in the laboratory to record the calibre of vessels down to 100 m, albeit with the same limited tissue penetration as other clinical X-ray devices. 16,17 Early studies 11,12 performed at second-generation synchrotron facilities, namely the Photon Factory (KEK) and Tristan Accumulation Ring in Tsukuba (Japan), have achieved 40-140 m vessel resolution with SR of lowerquality radiation than is now available at third-generation facilities. Currently, the highest spatial resolution (6 m pixel size) attained with SR is obtained with the SATICON detector system (NHK and Hitachi, Tokyo Japan) at SPring-8, which can be used for small area imaging (Table 1).…”

“…20 However, as we and others have demonstrated recently, available detector systems permit rapid imaging and spatial resolution for accurate analysis of vessel calibre in the lungs and heart based on individual image frames. [11][12][13][14]22,[24][25][26] Nevertheless, image summation is also used routinely to enhance vessel morphology when vessel calibres are < 50 m and sequential images are not confounded by vessel movement, such as in the brain or skin tumours. [27][28][29][30][31][32] In such cases, image summation is particularly useful when contrast agent dilution or non-uniformity makes vessel edge detection difficult from single frames.…”

“…10 The fluxes recorded at the samples in early SR studies with dogs and humans ranged from 10 8 to 10 10 photons/mm 2 per s. 11,12 More recent animal microangiography studies have used fluxes up to approximately 10 12 photons/mm 2 per s. 13,14 The most significant consequences of this greater light intensity using SR are: (i) greater X-ray penetration of thick tissues; and (ii) greater image contrast for a given volume of contrast agent. X-Ray penetration of any sample is attenuated exponentially with distance according to the elemental composition of the sample.…”

Medical Applications with Synchrotron Radiation in Japan

“…In intravenous CAG, the coronary arteries overlapping on cardiac chambers and the dilution process of contrast material determined by the cardiac function reduced the visibility of arteries. To overcome these problems, aortographic CAG was examined in dogs (Takeda, Umetani et al, 1997Umetani et al, 1996).…”

Ratio-contrast imaging of dual-energy absorption for element mapping with a scanning transmission X-ray microscope

“…Because the change in photon energies is only a few percent or less, the absorption of X-rays by all the other elements in the specimen is negligible, and consequently any observed difference in the transmitted X-ray flux between the two images obtained at the two energies can be attributed to the presence of the element being studied (Rarback et al, 1987). With this method the measurement of elemental spatial distributions has been achieved using various light sources (Houk et al, 1979;Sarnelli et al, 2004Sarnelli et al, , 2006Umetani et al, 1996) and has been widely applied to many science fields, especially in the medical area (Lewis, 1997;Krug et al, 2006;Bewer et al, 2008;Takeda et al, 1998). Among these light sources, synchrotron radiation offers several advantages for absorption-contrast imaging, such as high intensity, high brilliance, natural collimation of the radiation, and energy consecutive tunability of the emitted X-rays, which makes it possible to select a narrow wavelength band with a monochromator (Suortti & Thomlinson, 2003).…”