Embossed x-ray computed tomography utilizing pixel-shifted dual-energy subtraction.

To observe fine blood vessels as uneven tomographic images at a high contrast, we performed tentative experiments on embossed x-ray computed tomography (CT). We constructed a cone-beam CT scanner and carried out dual-energy CT with tube voltages of 60 and 100 kV. X-ray photons penetrating through an object were detected using an indirect-conversion flat panel detector, and radiograms were produced and sent to a personal computer to reconstruct tomograms. Embossed CT was performed using pixel-shifted dual-energy subtraction, and blood vessels filled with Gd medium were observed as uneven images at high contrast and spatial resolutions. Using 1.4-time magnification imaging in combination with a 0.1-mm-focus x-ray tube, the diameter of the object visible on the embossed CT was below 100 µm.

Near-infrared-ray computed tomography with an 808 nm laser beam and high spatial resolutions.

To increase the penetrating photons and to improve the spatial resolution in near-infrared-ray computed tomography (NIR-CT), we used an 808 nm laser module. The NIR photons are produced from the laser module, and an object is exposed to the laser beam. The laser power is controlled by the applied voltage, and the photodiode detects photons penetrating through the object. To reduce scattering photons from the object, a 1.0-mm-diameter graphite pinhole is set behind the object. The spatial resolutions were improved using a 1.0-mm-diameter 5.0-mm-length graphite collimator and were ∼1 × 1 mm2. The NIR-CT was accomplished by repeating the object-reciprocating translations and rotations of the object using the turntable, and the ray-sampling-translation and rotation steps were 0.1 mm and 0.5°, respectively. The scanning time was 19.6 min at a total rotation angle of 180°. Triple-sensitivity CT was accomplished using amplifiers, and a graphite rod in the chicken fillet was visible when increasing amplification factor.

Optimization of stereospecific targeting technique for selective production of monoclonal antibodies against native ephrin type-A receptor 2.

High priority stereospecific targeting (SST) featuring selective production of conformation-specific monoclonal antibodies was directed against a native receptor, EphA2 (ephrin type-A receptor 2). A critical point for this technology is selection of sensitized B lymphocytes by antigen-expressing myeloma cells through their B-cell receptors (BCRs). The essential point is that antigens expressed on myeloma cells retain their original three dimensional structures and only these are recognized. Immunization with recombinant plasmid vectors as well as antigen-expressing CHO cells elicits enhanced sensitization of target B lymphocytes generating stereospecific antibodies. More than 24% of hybridoma-positive wells were identified to be cell-ELISA positive, confirming high efficiency. IgG-typed conformation-specific monoclonal antibodies could be also produced by the SST technique. Immunofluorescence analysis confirmed specific binding of sensitized B lymphocytes to antigen-expressing myeloma cells. Furthermore, stereospecific monoclonal antibodies to EphA2 specifically recognized EphA2-expressing cancer cells as demonstrated by Cell-ELISA. In the present study, we were able to develop priority technology for selective production of conformation-specific monoclonal antibodies against an intact receptor EphA2, known to be overexpressed by epithelial tumor cells of multiple cancer types.

Triple-sensitivity high-spatial-resolution X-ray computed tomography using a cadmium-telluride detector and its beam-hardening effect.

To observe blood vessels at high contrasts, we constructed a first-generation triple-sensitivity X-ray computed tomography (TS-CT) scanner using a cadmium-telluride (CdTe) detector and a triple-amplifying system. X-ray photons are absorbed by the CdTe crystal, and the electric charges produced by photons are converted into voltages using a current-to-voltage (I-V) amplifier, and the I-V output is amplified by a voltage-to-voltage (V-V) amplifier. The V-V output 1 is sent to a dual V-V amplifier through a 5.0-m-length coaxial cable and amplified to two-different outputs of 2 and 3. The three outputs 1-3 are sent to a personal computer through an analog-to-digital converter to reconstruct three tomograms simultaneously. In the TS-CT, the scattering photons from the object are extremely reduced using a 0.5-mm-diameter lead pinhole behind the object. The translation and rotation steps were 0.1 mm and 0.5°, respectively, and the spatial resolutions were 0.25 × 0.25 mm2. The scanning time was 19.6 min, and blood vessels were visible using gadolinium contrast media. In particular, the effective photon energy increased with increasing amplification factor of the amplifier caused by beam hardening of the object.

Low-dose low-scattering X-ray computed tomography with high-spatial-energy resolutions using a cooled cadmium telluride detector.

To improve the image quality of photon-counting energy-dispersive X-ray computed tomography (CT) and to reduce the incident dose for the object, we have developed a low-dose low-scattering CT scanner with high-spatial and -energy resolutions using a cooled cadmium telluride (CdTe) detector. X-ray photons are absorbed by the CdTe crystal, and the event pulses from the shaping amplifier are input to a high-speed triple-energy (TE) counter. In the TE-CT, four 3.0-mm-thick lead (Pb) pinholes are used. The line-beam diameter is roughly reduced using the first 2.0-mm-diam pinhole. Using the second 0.5-mm-diam pinhole, the line-beam diameter is reduced again, and the 0.5-mm-diam line beam is exposed to the object. The scattering photon count was reduced using the third 0.5-mm-diam pinhole, and the only penetrating photons are absorbed by the cooled CdTe crystal through the fourth 0.3-mm-diam pinhole for improving the spatial resolution. K-edge tomograms using iodine (I) and gadolinium (Gd) media were obtained simultaneously at two energy ranges of 33-50 and 50-100 keV, respectively. Utilizing I-K-edge CT, coronary arteries filled with I medium were visible. Next, blood vessels filled with Gd medium were observed at high contrasts using Gd-K-edge CT. The maximum count rate was 30 kilocounts per second (kcps) at a tube current of 0.33 mA, and the minimum count rate after penetrating objects was approximately 2 kcps. The maximum incident dose for the object was approximately 0.3 mGy, and the exposure time for TE-CT was 19.6 min at a total rotation angle of 360°. The energy resolution of the detector was 1.1% at 59.5 keV, and the spatial resolutions had values of 0.3 × 0.3 mm2.

Investigation of quad-energy high-rate photon counting for X-ray computed tomography using a cadmium telluride detector.

To obtain four kinds of tomograms at four different X-ray energy ranges simultaneously, we have constructed a quad-energy (QE) X-ray photon counter with a cadmium telluride (CdTe) detector and four sets of comparators and microcomputers (MCs). X-ray photons are detected using the CdTe detector, and the event pulses produced using amplifiers are sent to four comparators simultaneously to regulate four threshold energies of 20, 33, 50 and 65keV. Using this counter, the energy ranges are 20-33, 33-50, 50-65 and 65-100keV; the maximum energy corresponds to the tube voltage. We performed QE computed tomography (QE-CT) at a tube voltage of 100kV. Using a 0.5-mm-diam lead pinhole, four tomograms were obtained simultaneously at four energy ranges. K-edge CT using iodine and gadolinium media was carried out utilizing two energy ranges of 33-50 and 50-65keV, respectively. At a tube voltage of 100kV and a current of 60 µA, the count rate was 15.2 kilocounts per second (kcps), and the minimum count rates after penetrating objects in QE-CT were regulated to approximately 2 kcps by the tube current.

Measurement of X-ray spectra using a Lu2(SiO4)O-multipixel-photon detector with changes in the pixel number.

To measure X-ray spectra with high count rates, we developed a detector consisting of a Lu2(SiO4)O [LSO] crystal with a decay time of 40 ns and a multipixel photon counter (MPPC). The photocurrents flowing through the MPPC are converted into voltages and amplified by a high-speed current-voltage amplifier, and event pulses from the amplifier are sent to a multichannel analyzer to measure spectra. We used three MPPCs of 100, 400 and 1600 pixels/mm(2), and the MPPCs were driven under pre-Geiger mode at a temperature of 20 °C. At a tube voltage of 100 kV and a tube current of 5.0 µA, the maximum count rate was 12.8 kilo-counts per second. The event-pulse widths were 200 ns, and the energy resolution was 53% at 59.5 keV using a 100-pixel MPPC.

Demonstration of enhanced iodine K-edge imaging using an energy-dispersive X-ray computed tomography system with a 25 mm/s-scan linear cadmium telluride detector and a single comparator.

An energy-dispersive (ED) X-ray computed tomography (CT) system is useful for carrying out monochromatic imaging. To perform enhanced iodine K-edge CT, we developed an oscillation linear cadmium telluride (CdTe) detector with a scan velocity of 25 mm/s and an energy resolution of 1.2 keV. CT is performed by repeated linear scans and rotations of an object. Penetrating X-ray photons from the object are detected by the CdTe detector, and event signals of X-ray photons are produced using charge-sensitive and shaping amplifiers. The lower photon energy is determined by a comparator device, and the maximum photon energy of 60 keV corresponds to the tube voltage. Rectangular-shaped comparator outputs are counted by a counter card. In the ED-CT, tube voltage and current were 60 kV and 0.30 mA, respectively, and X-ray intensity was 14.8 µGy/s at 1.0m from the source at a tube voltage of 60 kV. Demonstration of enhanced iodine K-edge X-ray CT for cancer diagnosis was carried out by selecting photons with energies ranging from 34 to 60 keV.

15Mcps photon-counting X-ray computed tomography system using a ZnO-MPPC detector and its application to gadolinium imaging.

15Mcps photon-counting X-ray computed tomography (CT) system is a first-generation type and consists of an X-ray generator, a turntable, a translation stage, a two-stage controller, a detector consisting of a 2mm-thick zinc-oxide (ZnO) single-crystal scintillator and an MPPC (multipixel photon counter) module, a counter card (CC), and a personal computer (PC). High-speed photon counting was carried out using the detector in the X-ray CT system. The maximum count rate was 15Mcps (mega counts per second) at a tube voltage of 100kV and a tube current of 1.95mA. Tomography is accomplished by repeated translations and rotations of an object, and projection curves of the object are obtained by the translation. The pulses of the event signal from the module are counted by the CC in conjunction with the PC. The minimum exposure time for obtaining a tomogram was 15min, and photon-counting CT was accomplished using gadolinium-based contrast media.

100 µA-100 kV Photon-counting X-ray Computed Tomography System Using an LSO-MPPC Detector and a High-Speed Comparator and its Application to Gadolinium Imaging.

A high-sensitive x-ray computed tomography (CT) system is useful for decreasing absorbed dose for patients, and we performed preliminary experiments for first-generation photon-counting CT using a high-sensitive single detector. X-ray photons are detected using an LSO [Lu2(SiO4)O] single crystal scintillator and a multipixel photon counter (MPPC). The photocurrent from the MPPC is amplified by a current-voltage amplifier and an integrator, and the event pulse is sent to a high-speed comparator. Logical pulses are then produced by the comparator and are counted by a counter card. Tomography is accomplished by repeated linear scans and rotations of an object, and projection curves of the object are obtained by the linear scan. The count rate decreased with increase in lower level voltage of the comparator Vl, and the maximum count rate was 265 kcps at a Vl of 0.4 V. The exposure time for obtaining a tomogram was 10 minutes at a scan step of 0.5 mm and a rotation step of 1.0°. The image contrast of gadolinium medium slightly varied with change in Vl. We carried out low-dose-rate photon-counting CT at a tube current of 100 µA and a tube voltage of 100 kV. The energy-dispersive effect of the CT image was confirmed by selecting Vl. The absorbed dose for objects can be reduced using the linear detector consisting of plural LSO-MPPC detectors.

Uncommon dermoid cyst presented in the mandible possibly originating from embryonic epithelial remnants.

A case of an intraosseous dermoid cyst that had developed in the mandible of a 29-year-old-male is reported. The patient was admitted to our dental clinic complaining of pain in the right molar area of the mandible. The patient had no particular history of the present illness. A radiographic examination revealed diffuse bone absorption in the right molar area. A biopsy showed the lesion to be an intraosseous dermoid cyst which was surgically enucleated. Microscopic examination of the excised tissue showed it to be well circumscribed with fibrous tissues, and the cystic space lined by keratinized epithelium. In addition, sweat glands and hair follicle-like skin appendages were identified in the cystic wall, where a daughter cyst was also found. We suggested that this uncommon cyst had developed in the mandible, as a result of embryonic epithelium migration. The patient remained in good health during the three year follow-up.