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Result : Searchterm 'Anterior Posterior' found in 1 term [ ] and 0 definition [ ], (+ 4 Boolean[ ] results
| | 1 - 5 (of 5) Result Pages : [1] | | | | | | | |  | Searchterm 'Anterior Posterior' was also found in the following service: | | | | |
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A large network of interconnecting blood vessels at the base of the brain that when visualized resembles a circle, the arteries effectively act as anastomoses for each other. This means that if any one of the communicating arteries becomes blocked, blood can flow from another part of the circle to ensure that blood flow is not compromised.
The circle of Willis is formed by both the internal carotid arteries, entering the brain from each side and the basilar artery, entering posteriorly. The connection of the vertebral arteries forms the basilar artery. The basilar artery divides into the right and left posterior cerebral arteries.
The internal carotid arteries trifurcate into the anterior cerebral artery, middle cerebral artery, and posterior communicating artery.
The two anterior cerebral arteries are joined together anteriorly by the anterior communicating artery. The posterior communicating arteries join the posterior cerebral arteries, completing the circle of Willis.
The time of flight angiography MRI technique allows imaging of the circle of Willis without the need of a contrast medium (best results with high field MRI). A cerebrovasular contrast enhanced magnetic resonance angiography (MRA) depicts the circle of Willis in addition to the vessels of the neck (carotid and vertebral arteries) with one bolus injection of a contrast agent.
For Ultrasound Imaging (USI) see Cerebrovascular Ultrasonography at US-TIP.com.
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• View the DATABASE results for 'Circle of Willis' (5).
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• View the DATABASE results for 'Coronal' (6).
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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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The 3 basic orthogonal slice orientations are:
transversal (T), sagittal (S) and coronal (C). |
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The basic anatomical directions are:
right(R) to left (L), posterior (P) to anterior (A), and feet (F) to head (H). |
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A standard display orientation for images in the basic slice orientation is:
1) transverse: A to top of image and L to right,
2) coronal: H to top of image and L to right and
3) sagittal: H to top of image and A to left.
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The location in the R/L and P/A directions can be specified relative to the axis of the magnet.
The F/H location can be specified relative to a convenient patient structure.
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.
Double oblique slices can be specified as the result of tipping a single oblique plane toward the remaining basic orientation plane, about an axis defined by the intersection of the oblique plane and the remaining basic plane. In double oblique angulations, the first rotation is chosen about the vertical image axis and the second about the (new) horizontal axis.
Angles are chosen to have magnitudes less than 90° (for single oblique slices less than 45°); the sign of the angle is taken to be positive when the rotation brings positive axes closer together. |
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• View the DATABASE results for 'Orientation' (16).
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| | | Searchterm 'Anterior Posterior' was also found in the following service: | | | | |
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| | | 1 - 5 (of 5) Result Pages : [1] |
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