Hisatake Yokouchi

Laser‐stimulable transparent CsI:Na film for a high quality x‐ray imaging sensor

Transparent films, which can be stimulated by laser beams after x‐ray irradiation, have been searched to improve the spatial resolution of digital x‐ray imaging sensors. As a result, evaporated CsI:Na films are found to be efficiently laser stimulable around 77 K. The modulation transfer function (MTF) of the film is evaluated using a scanning Ga1−xAlxAs semiconductor laser. The high MTF value (57% at 2 1p/mm), strong x‐ray absorption, and high stimulation efficiency of the film ensure a high quality sensor for digital radiography.

Cis-Trans Photoisomerization of Perinaphthothioindigo for Use as a Photo-Imaging Sensor Using Fluorescence under He-Ne Laser Excitation

An imaging sensor based on the cis/trans isomerization of thioindigoid dyes is proposed. A photo-image (~500 nm) is stored as a density distribution of the trans-form in the cis-form material, and read out as fluorescence (~700 nm) from the trans-form by scanning with He-Ne laser (633 nm) excitation. As the fluorescence decay time of perinaphthothioindigo is 1.8 ns, the sensor permits rapid read-out. For light exposure L from 10-4 to 10-1 J/cm2 at 500 nm, the fluorescence intensity under laser excitation varies as L0.8.

High-sensitivity digital radiography using an avalanche-type image pickup tube camera

A medical imaging camera with an avalanche-type image pickup tube (HARPICON) was developed for digital radiography. The camera obtains high quality images even at low doses because its sensitivity is as much as 32 times higher than that of a conventional pickup tube camera. The camera also has a wide dynamic range and a high signal-to-noise ratio because of HARPICONs gamma characteristic.

Development of a 4000-scanning-lines high-resolution TV camera for real-time digital radiography system

We have developed a 4200 scanning lines TV camera using a 2-inch diameter, electrostatic focus and electrostatic deflection type SATICONTM 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.

Hospital-wide PACS with a digital image intensifier TV system

Tokyo Hitachi Hospital, Hitachi Ltd., has used a hospital-wide PACS for over 1 year. The system runs a 100 Mb/s optical fiber network over the whole hospital including wards and outpatient clinic rooms, with 11 image workstations. The network links digital imaging modalities such as X-CT, MRI, computed radiography (CR) and digital radiography (DR) with a 2048 x 2048 (2k x 2k) matrix image intensifier television (I.I.-TV) system. These modalities generate about 200 images/day. The system has managed over 300,000 images of about 8000 patients so far. Although being still under improvement, the system has really been used for routine work. The hospital-wide PACS of a small hospital has been proved to be very useful for both image diagnosis and image management.