Medical Ultrasound Imaging
Tuesday, 3 December 2024
 Info Sheets  Out- side     | 'Oblique' Searchterm 'Oblique' found in 6 articles 6 definitions [ • ] Result Pages : •
If available, some graphic aids can be helpful to show image orientations. 1) A graphic icon of the labeled primary axes (A, L, H) with relative lengths given by direction sines and orientation as if viewed from the normal to the image plane can help orient the viewer, both to identify image plane orientation and to indicate possible in plane rotation. 2) Ingraphic prescription of obliques from other images, a sample original image with an overlaid line or set of lines indicating the intersection of the original and oblique image planes can help orient the viewer.
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In all cases the scanning surface is assigned to the top of the image. The orientation of single oblique slices can be specified by rotating a slice in one of the basic orientations toward one of the other two basic orthogonal planes about an axis defined by the intersection of the 2 planes. See also Histogram. •
The refraction is the change of the sound direction on passing from one medium to another. In ultrasound, refraction is due to sound velocity mismatches combined with oblique angles of incidence, most commonly with
convex scanheads. When the ultrasound wave crosses at an oblique angle the interface of two materials, through which the waves propagate at different velocities, refraction occurs, caused by bending of the wave beam. See also Refraction Artifact, Acoustic Shadowing, Acoustic Mismatch, and Duplication Artifact. •
Sonography of the gallbladder is a reliable technique for diagnosing e.g., gallstones, cholecystitis, tumors, polyps, or ductal obstruction.
Patient should be examined with empty stomach and on a low fat diet the night before. Barium studies, endoscopy, ERCP, colonoscopy, and abdominal CT should be performed after this examination. Gallbladder ultrasound is best performed with a 5 MHz curved array or a linear array transducer in cases of a very superficial gallbladder. In obese patients or in patients with difficult sonographic access, a 3.5 MHz sector or curved linear transducer is advantageous. Gallbladder and biliary tree are usually imaged in supine and posterior oblique (LPO) positions. Sometimes very small gallstones are better visible in upright and prone position.  Further Reading: Basics:
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(LUS) Diagnostic laparoscopy combined with laparoscopic ultrasound is used for staging tumors and to monitor surgical interventions like for example radiofrequency ablation or cryotherapy. Laparoscopic ultrasound provides direct contact imaging of organs with high frequency ultrasound. Laparoscopic ultrasound identifies and characterizes the tumor, guides the probe, and monitors the progression of the freezing or the thermal destruction. This procedure avoid unnecessary open surgery and improves selection of patients for tumor resection e.g., in liver and pancreas. Challenges of LUS are limitations of the intraoperative acoustic windows and the possible movement of the probe and that standard orientation techniques are difficult to apply with laparoscopic instruments, resulting in images from oblique planes. 3D ultrasound or special navigation systems may be helpful. See also Ultrasound Therapy. •
(MPR) Multiplanar Reconstruction is a post processing technique for reformatting of a 3D data set at any angle; reconstructing e.g. the axial images into coronal, sagittal and oblique anatomical planes.
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[last update: 2023-11-06 01:42:00]