The Monolithic Systems Development Group of the Oak Ridge National Laboratory is developing a new high resolution x-ray computed tomography (MicroCAT) system to generate 3-dimensional images of the internal structure of laboratory animals.  Unlike conventional medical computed tomography systems which have spatial resolutions on the order of 1-2 mm, MicroCAT employs detectors with intrinsic resolutions less than 0.05 mm and produces reconstructed images with spatial resolutions less than 0.1 mm.  With MicroCAT, researchers are able to study the skeleton and internal organs of mice with the same relative accuracy available to physicians studying human physiology.  Additionally, because of the novel detector design employed by the MicroCAT system, researchers will soon be able to simultaneously acquire fully registered x-ray and nuclear medicine images of the same subject.

MicroCAT is expected to greatly enhance the capabilities of ORNL biologists studying genetic mutations in laboratory mice.  ORNL is home to the world's largest experimental mouse colony with more than 70,000 mice representing about 400 mutant strains.  The MOUSE HOUSE is the cornerstone of the ORNL Mammalian Genetics program that was established soon after World War II to assess the biological effects of ionizing radiation in mammals.  More recently the ORNL mutant collection has been used as a resource for analyzing gene function and identifying mouse models of human genetic diseases.

Before the MicroCAT development researchers relied on visible genetic markers and physical examination of the animals to discover the presence of phenotypes (mutations).  The internal structure could only be examined by sacrificing and dissecting the mouse, making it impossible to track the development of a mutation over a period of time in the same animal.  In addition to requiring the destruction of mice, the examination process was expensive and time consuming.  With MicroCAT, researchers can rapidly screen mice for internal phenotypes (mutations) and can monitor the development and treatment of mice found to exhibit phenotypes.

Two versions of the MicroCAT scanner are under development.  The first version employs a digital mammography detector with intrinsic resolution less than 0.05 mm.  With this detector a mouse can be scanned in a few minutes while under a general anesthesia.  This detector may also be used to acquire a traditional radiography image in less than one second.  The design of the first version is complete and a prototype system is being evaluated.

The second version of MicroCAT uses a novel energy sensitive detector to measure both the position and energy of each x-ray.  Initial images have been acquired using a single-pixel energy dependent detector and work is under-way to develop a multi-element detector array and the associated integrated circuits.

The MicroCAT project is sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by Lockheed Martin Energy Research Corp. for the U. S. Department of Energy under Contract No. DE-AC05-96OR22464.