| Research Abstract |
Diagnostic unaging of the mediastinum is based on the anatomical analysis of the images. Transverse sectional imaging anatomy of the mediastinum by X-ray CT has been established. Reconstructed longitudinal sectional image of the mediastinum from transverse sectional images by CT is not suitable for fine anatomical analysis. Longitudinal sectional image is obtainable by MRI for diagnostic unaging of the mediastinum. However, MRI does not have sufficient spatial resolution power for analysis due to motion artifact. Real-time dynamic image by transesophageal endoscopic ultrasonography(EUS)is applied for analysis of imaging anatomy of the longitudinal sectional plane of the mediastinum.
For X-ray CT, type CT/T-9800(General Electric), and type TCT-60A or TCT-70A(Toshiba)was used with 10 mm slice thickness, 10 mm slice spacing, window width of 400, and window level at 50 HU. VISTA-0.5HP(Picker), MRT-15A(Toshiba), or Signa(General electric)was used for MRI with short spin echo method. Transeso
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phageal EUS was performed by EPB-503FS(5 MHz)linear array ultrasound endoscope with SAL-50A(Toshiba), EPE-707FS(7.5 MHz)linear array with SSA-90A(Toshiba), or UST936-5(5 MHz)convex endosonographic probe with SSD-650(Aloka)was used. Under mucosal surface anaesthesia, EUS was performed through the esophagus with sliding and tilting the ultrasound endoscope. Images were recorded by VTR and still photographs. Images of these 3 modalities were compared, and anatomically analyzed.
Directions of the longitudinal planes for MRI and EUS were determined by transverse sectional images of CT and MRI on the various levels. MR images on the longitudinal sectional plane through the esophagus were compared to the images by the transesophageal EUS. Outline of the mediastinal structures were revealed on the MRI. Motion artifacts were frequently appeared on the MRI. Resolution power of MRI and CT for static objects were clinically acceptable. However, resolution power for moving target was poor. Fine analysis with the resolution power at mm order was possible by real-time transesophageal ultrasonography. Following anatomical structures were identified by transesophageal EUS : esophageal wall, vertebra, lung, left brachiocephalic vein, brachiocephalic trunk, left common carotid artery, lest subclavian artery, ascending aorta, aortic arch, descending aorta, superior vena cava, azygos vein, right auricle, tricuspid valve, right ventricle, pulmonary valve, pulmonary trunk, right pulmonary artery, left pulmonary artery, trachea, main bronchi, left auricle, right upper-, right lower-, left upper-, and left lower-pulmonary vein, mitral valve, left ventricle, aortic valve, coronary artery, coronary sinus, inferior vena cava, hepatic vein, lever, heart, pleural space, and diaphragm. Dead angles by transesophageal EUS because of the air, and the bones were covered by MRI. Schematic illustrations of sectional images of the mediastinum through the esophagus were made based on typical images of longitudinal sectional plane at different direction.
Fundamental knowledge was established to understand dynamic imaging anatomy of the mediastinum by CT, MRI, and transesophageal real-time EUS. Extensive continuing study for mediastinal imaging anatomy must be achieved by future technical development, of these three modalities. Less
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