Akihiro Osawa

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.

Energy-Discriminating Gadolinium K-Edge X-ray Computed Tomography System

An energy-discriminating K-edge X-ray computed tomography (CT) system is useful for increasing the contrast resolution of a target region utilizing contrast media and for reducing the absorbed dose for patients. The CT system is of the first-generation type of detector using cadmium telluride (CdTe). CT is performed by repeated translations and rotations of an object. Penetrating X-ray photons from the object are detected by a CdTe detector, and event signals of X-ray photons are produced using charge-sensitive and shaping amplifiers. Both photon energy and energy width are selected out using a multichannel analyzer, and the number of photons is counted by a countercard. To perform energy discrimination, a low-dose-rate X-ray generator for photon counting was developed. Its maximum tube voltage and minimum tube current were 110 kV and 1 µA, respectively. In energy-discriminating CT, the tube voltage and tube current were 100 kV and 20 µA, respectively, and the X-ray intensity was 2.98 µGy/s at a distance of 1.0 m from the source and a tube voltage of 100 kV. The demonstration of enhanced gadolinium K-edge X-ray CT was carried out by selecting photons with energies just beyond the gadolinium K-edge energy of 50.3 keV.

Energy discriminating x-ray camera utilizing a cadmium telluride detector

An energy-discriminating x-ray camera is useful for performing monochromatic radiography using polychromatic x rays. This x-ray camera was developed to carry out K-edge radiography using iodine-based contrast media. In this camera, objects are exposed by a cone beam from a cerium x-ray generator, and penetrating x-ray photons are detected by a cadmium telluride detector with an amplifier unit. The optimal x-ray photon energy and the energy width are selected out using a multichannel analyzer, and the photon number is counted by a counter card. Radiography was performed by the detector scanning using an x-y stage driven by a two-stage controller, and radiograms obtained by energy discriminating are shown on a personal computer monitor. In radiography, the tube voltage and current were 60 kV and 36 µA, respectively, and the x-ray intensity was 4.7 µGy/s. Cerium K-series characteristic x rays are absorbed effectively by iodine-based contrast media, and iodine K-edge radiography was performed using x rays with energies just beyond iodine K-edge energy 33.2 keV.

Investigation of dual-energy X-ray photon counting using a cadmium telluride detector and two comparators and its application to photon-count energy subtraction

To obtain two tomograms with two different photon energy ranges simultaneously, we have performed dual-energy X-ray photon counting using a cadmium telluride (CdTe) detector, two comparators, two frequency–voltage converters (FVCs), and an analog digital converter (ADC). X-ray photons are detected using the CdTe detector with an energy resolution of 1% at 122 keV, and the event pulses from a shaping amplifier are sent to two comparators simultaneously to regulate two thresholds of photon energy. The logical pulses from a comparator are sent to an FVC consisting of two integrators, a microcomputer, and a voltage–voltage amplifier. The smoothed outputs from the two FVCs are input to the ADC to carry out dual-energy imaging. To observe contrast variations with changes in threshold energy, we performed energy-dispersive computed tomography utilizing the dual-energy photon counting at a tube voltage of 70 kV and a current of 25 µA. Two tomograms were obtained simultaneously at two energy ranges of 20.0–70.0 keV and 33.2–70.0 keV. The photon-count subtraction was carried out using photon energies ranging from 20.0 to 33.2 keV. The maximum count rate was 5.4 kilocounts per second with energies of 20.0–70.0 keV, and the exposure time for tomography was 10 min.

Combined hepatic resection with the inferior vena cava and diaphragm and reconstruction using an equine pericardial patch: Report of a case

We herein report a case of combined hepatic resection with inferior vena cava (IVC) and diaphragm resection, and reconstruction using an equine pericardial patch. A 54-year-old woman showed hepatic cancer recurrence on radiological imaging, with invasion to the caudate lobe of the liver, IVC, diaphragm, and adrenal gland. We resected 10 × 5 cm of the diaphragm. After dissecting the hepatic parenchyma, the caudate lobe was connected only to the IVC. Clamping of the IVC was performed between the IVC below the confluence of the hepatic vein and the suprarenal IVC. A 6 × 3-cm segment of the IVC was then resected. The IVC and diaphragm were reconstructed using an equine pericardial patch, as both defects were too large to repair without a patch. The equine pericardium represents a suitable graft material for repairing both the IVC and diaphragm. Further investigation is needed to determine the durability and anti-infection properties of equine pericardial grafts.

Energy-discriminating K-edge x-ray computed tomography system

An energy-discriminating K-edge x-ray Computed Tomography (CT) system is useful for increasing contrast resolution of a target region and for diagnosing cancers utilizing a drug delivery system. The CT system is of the first generation type and consists of an x-ray generator, a turn table, a translation stage, a two-stage controller, a cadmium telluride (CdTe) detector, a charge amplifier, a shaping amplifier, a multi-channel analyzer (MCA), a counter board (CB), and a personal computer (PC). The K-edge CT is accomplished by repeating translation and rotation of an object. Penetrating x-ray spectra from the object are measured by a spectrometer utilizing the CdTe detector, amplifiers, and MCA. Both the photon energy and the energy width are selected by the MCA for discriminating photon energy. Enhanced iodine K-edge x-ray CT was performed by selecting photons with energies just beyond iodine K-edge energy of 33.2 keV.

Investigation of Energy-Dispersive X-ray Computed Tomography System with CdTe Scan Detector and Comparing-Differentiator and Its Application to Gadolinium K-Edge Imaging

An energy-dispersive (ED) X-ray computed tomography (CT) system is useful for carrying out monochromatic imaging by selecting optimal energy photons. CT is performed by repeated linear scans and rotations of an object. X-ray photons from the object are detected by the cadmium telluride (CdTe) detector, and event pulses of X-ray photons are produced using charge-sensitive and shaping amplifiers. The lower photon energy is determined by a comparator, and the maximum photon energy of 70 keV corresponds to the tube voltage. Logical pulses from the comparator are counted by a counter card through a differentiator to reduce pulse width and rise time. In the ED-CT system, tube voltage and current were 70 kV and 0.30 mA, respectively, and X-ray intensity was 18.2 µGy/s at 1.0 m from the source at a tube voltage of 70 kV. Demonstration of gadolinium K-edge CT for cancer diagnosis was carried out by selecting photons with energies ranging from 50.4 to 70 keV, and photon-count energy subtraction imaging from 30 to 50.3 keV was also performed.

Low-Dose-Rate Computed Tomography System Utilizing 25 mm/s-Scan Silicon X-ray Diode and Its Application to Iodine K-Edge Imaging Using Filtered Bremsstrahlung Photons

A low-dose-rate X-ray computed tomography (CT) system is useful for reducing absorbed dose for patients. The CT system with a tube current of sub-mA was developed using a silicon X-ray diode (Si-XD). The Si-XD is a high-sensitivity Si photodiode (PD) selected for detecting X-ray photons, and the X-ray sensitivity of the Si-XD was twice as high as that of Si-PD cerium-doped yttrium aluminum perovskite [YAP(Ce)]. X-ray photons are directly detected using the Si-XD without a scintillator, and the photocurrent from the diode is amplified using current–voltage and voltage–voltage amplifiers. The output voltage is converted into logical pulses using a voltage–frequency converter with a maximum frequency of 500 kHz, and the frequency is proportional to the voltage. The pulses from the converter are sent to the differentiator with a time constant of 500 ns to generate short positive pulses for counting, and the pulses are counted using 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 exposure time for obtaining a tomogram was 5 min at a scan step of 0.5 mm and a rotation step of 3.0°. The tube current and voltage were 0.55 mA and 60 kV, respectively, and iodine K-edge CT was carried out using filtered bremsstrahlung X-ray spectra with a peak energy of 38 keV.

Pancreatic adenosquamous carcinoma presenting as splenic rupture: Report of a case

A 58-year-old female patient presented with the sudden onset of left upper quadrant pain. The physical examination revealed the presence of shock status. Abdominal computed tomography revealed splenomegaly with a huge mass inside the spleen, and massive fluid collection in the abdominal cavity. After splenic artery embolization, laparotomy was performed. The operative findings revealed intra-abdominal hemorrhage and rupture of the lower pole of the spleen. Furthermore, a palpable solid mass was observed at the splenic hilum, and distal pancreatectomy with splenectomy was performed. The macroscopic findings revealed a pancreatic tail tumor at the splenic hilum directly invading the splenic parenchyma. Microscopic examinations showed the tumor to consist of squamous cell carcinoma. Furthermore, old and new thrombi were observed inside small splenic arteries. These findings were considered to represent invasion of pancreatic adenosquamous carcinoma to the spleen, and rupture of the spleen was attributed to splenic ischemia resulting from cancer invasion and splenic vein obstruction.