Several muscles in the neck pivot the skull at the atlanto-occipital joint to make the head flex and extend in a nodding motion. The atlas plays a vital role in the support and movement of the head and neck. Slight depressions on each side of the posterior arch provide room for the C1 spinal nerve to exit the vertebral foramen and allow the vertebral artery to pass into the vertebral foramen before entering the skull at the foramen magnum of the occipital bone. The posterior tubercle is similar in structure and function to the much larger spinous process found in most vertebrae. While it is thin throughout its length, the posterior arch widens slightly at its posterior-most point to form the posterior tubercle. The posterior arch extends posteriorly from the lateral masses and completes the ring of the atlas around the hollow vertebral foramen. The transverse process protects the blood vessels in the transverse foramen and serves as an attachment point for muscles that move the neck. Each transverse process surrounds a tiny transverse foramen, a hole that provides room for the vertebral artery and vein to travel through the neck. The inferior articular facets are extremely smooth on their inferior surfaces and form the lateral atlanto-axial joint between the atlas and the axis.Įxtending laterally from each lateral mass is an irregular ring of bone known as the transverse process.
On the inferior side of each lateral mass is a short, flat, cylindrical projection of bone known as the inferior articular facet. The superior articular facets form the atlanto-occipital joint with the condyles of the occipital bone of the skull, allowing the head to flex and extend at the neck. Each lateral mass has a smooth, oval, cup-like depression known as the superior articular facet on its superior surface. On either side of the anterior arch are the lateral masses, which are the widest regions of the atlas. The posterior of the anterior arch meets the odontoid process of the C2 vertebra (axis) to form the median atlantoaxial joint. The anterior arch curves posteriorly and laterally from the anterior tubercle and has a smooth joint-forming process on its posterior side. Instead, there is a thin band of bone known as the anterior arch and a small mass on its anterior surface known as the anterior tubercle.
Unlike most vertebrae, there is no body or centrum on the anterior end of the atlas. The atlas is the thinnest and most delicate of the cervical vertebrae, consisting of a thin ring of bone with a few small projections. All rights reserved.The atlas is located at the top of the neck, just inferior to the condyles of the occipital bone of the skull and superior to the C2 vertebra. The atlas is publicly available at Copyright © 2011 Elsevier Inc. Also, the resulting 4D atlas can serve as a good representative of the population of interest as it reflects both global and local changes.
#Atlas definition registration
The resulting 4D atlas has greater anatomic definition than currently available 4D atlases created using various affine and non-rigid registration approaches, an important factor in improving registrations between the atlas and individual subjects.
Comparisons between the resulting atlas and atlases constructed using affine and non-rigid registration are presented. This leads to an atlas that retains a consistent level of detail at every time-point. A novelty in our approach is the use of a time-varying kernel width, to overcome the variations in the distribution of subjects at different ages. In addition, kernel regression is used to produce age-dependent anatomical templates. The method used for the creation of the average 4D atlas utilizes non-rigid registration between all pairs of images to eliminate bias in the atlas toward any of the original images. In this paper we present an approach for constructing a 4D atlas of the developing brain, between 28 and 44 weeks post-menstrual age at time of scan, using T1 and T2 weighted MR images from 204 premature neonates. A better understanding of brain development requires a spatio-temporal atlas that characterizes the dynamic changes during this period. Medical imaging has shown that, during early development, the brain undergoes more changes in size, shape and appearance than at any other time in life.