What's New in AIR 2.0

The AIR package has been extensively rewritten for the version 2.0 release. A number of enhancements have been incorporated that should result in greater speed, accuracy, and flexibility.

Intersubject Registration

In addition to the rigid body model used in AIR 1.0, a variety of models appropriate for intersubject registration have now been incorporated into the AIR package. These models allow images from different subjects to be aligned to one another or to an atlas template. These models may also be useful for intrasubject registration of nonbrain structures that are subject to nonrigid deformations.

Full Support for 2D and 3D Models

In contrast to AIR 1.0 where 2D models were implemented relatively inefficiently as special cases of the corresponding 3D models, the 2D models are now implemented independently.

Alternative Cost Functions

In addition to the intensity independent cost function used by AIR 1.0, AIR 2.0 provides the option to use a least squares cost function for situations where intensity scaling is not required.

Alternative Interpolation Models

In addition to tri-linear interpolation, nearest neighbor and sinc interpolation options are now available.

Improved Minimization Procedure

The minimization procedure used in AIR 1.0 has been replaced by a multi-variate Newtonian minimization procedure that provides greater flexibility and optimizes the efficiency of the minimization process when the cost function is close to the minimum.

No restrictions on voxel proportions

The requirement that pixels be square has been eliminated. This should greatly simplify the use of coronal and sagittal MRI data.

Lower RAM Requirements

The RAM requirements of the alignment programs have been significantly reduced.

World Wide Web Documentation

The printed AIR user's manual has been replaced by a World Wide Web site. The documentation has been extensively revised and supplemented with equations and figures. Maintenance of a centralized documentation site will allow corrections and clarifications to be communicated to users more efficiently.

Internet Distribution

AIR 2.0 will be distributed exclusively through the internet. Please note that AIR is protected by copyright and use of AIR is subject to compliance to the terms of the AIR license agreement.

Modified: December 15, 1995