Keio University · Medicine
Professor Yoshitake Yamada's research lab specializes in diagnostic radiology and medical imaging, with a focus on optimizing low-dose and low-radiation CT techniques to improve diagnostic accuracy while minimizing radiation exposure. The lab investigates advanced image reconstruction methods such as statistical iterative reconstruction (MBIR) and dual-energy imaging to enhance image quality and detect subtle pulmonary and hepatic lesions. Key research directions include evaluating respiratory and postural effects on lung volume and function using low-dose CT, and advancing tomosynthesis and dynamic radiography for improved nodule detection and functional assessment of the diaphragm in lung diseases like COPD.
Figures are computed from collected data and may differ slightly.
As compared with FBP, MBIR enables significant reduction of the image noise and artifacts and also better detection of noncalcified pulmonary nodules on ULDCT of the lung. Compared with LDCT-FBP images, ULDCT-MBIR images showed significantly reduced objective noise and comparable subjective image noise. Almost all of the noncalcified nodules and all of the calcified nodules could be detected on the ULDCT-MBIR images, when LDCT-FBP images were used as the reference.
VMS imaging at approximately 70 keV (69-70 keV) yielded the lowest image noise of the liver parenchyma and a high CNR for hypovascular hepatic metastases in the portal-dominant phase.
Currently, no clinical studies have compared the inspiratory and expiratory volumes of unilateral lung or of each lobe among supine, standing, and sitting positions. In this prospective study, 100 asymptomatic volunteers underwent both low-radiation-dose conventional (supine position, with arms raised) and upright computed tomography (CT) (standing and sitting positions, with arms down) during inspiration and expiration breath-holds and pulmonary function test (PFT) on the same day. We compared
While the volumes of the bilateral upper and lower lobes and bilateral lungs were significantly greater in the standing than in the supine position, with lower lobes showing larger changes, the right middle lobe volume did not change significantly between positions. The total lung volume on upright CT in the standing position was more similar to TLC on PFT than that in the supine position.
: The diagnostic performance of fast scanning tomosynthesis for the detection of pulmonary nodules was significantly superior to that of radiography. The TPF was affected by the size, CT attenuation value, and location of the nodule, in both fast scanning tomosynthesis and radiography.
Time-resolved quantitative evaluation of the diaphragm using dynamic chest radiography demonstrated that the diaphragmatic motion during tidal breathing in a standing position is larger and faster in COPD patients than in normal subjects.
The average excursions of the diaphragms are 11.0 mm (right) and 14.9 mm (left) during tidal breathing in a standing position. The diaphragmatic motion of the left is significantly larger and faster than that of the right. Higher BMI and tidal volume are associated with increased excursions of the bilateral diaphragm.
In IPAH patients, the RVEDVI predicts both hospitalization for right heart failure and mortality before initiating intravenous prostacyclin therapy.
The present study showed that angular rotations and positions of the clavicle and scapula change significantly with position due to the effect of gravity.
The purpose of this study was to compare renal cyst pseudoenhancement between virtual monochromatic spectral (VMS) and conventional polychromatic 120-kVp images obtained during the same abdominal computed tomography (CT) examination and among images reconstructed using filtered back projection (FBP), adaptive statistical iterative reconstruction (ASIR), and model-based iterative reconstruction (MBIR). Our institutional review board approved this prospective study; each participant provided writt
A decrease of the craniocaudal gradient of MPCR was observed in COPD patients. The craniocaudal gradient was lower in severe COPD patients than in mild COPD patients.
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