Image acquisition: Ultrasound, computed tomography, and magnetic resonanceimaging

As the transition toward total digital image acquisition continues, radiolo gy is transcending the current standard of two-dimensional (2-D) cross-sect ional anatomic imaging to more complex models. Among these are three-dimens ional (3-D) anatomic images, constructed either from a synthesis of traditi onal 2-D data sets, or directly from volumetrically acquired data. However, current trends are moving beyond mere anatomic imaging to include physiolo gical data once mainly obtained via nuclear medicine. Recent magnetic reson ance pulse sequences, in addition to Doppler and harmonic ultrasound method s, are providing insight into blood flow, oxygenation, and metabolite conce ntrations non-invasively. Through image registration techniques, these data (even from differing modalities) are being assembled into 2-D and 3-D "fus ion" images that promise to revolutionize diagnosis. Furthermore, with impr ovements in miniaturization, reliability, speed, built-in intelligence, and ease of use, these new developments are finding their way into use by nons pecialists. For instance, a new hand-held ultrasound unit will likely becom e a common tool among emergency medical teams, military medical teams, and in NASA's manned space program. Portable computed tomography (CT) scanners are already being used in the operating room. The increasing sophistication of imaging instruments will bring about a complementary increase in ease o f use for both scanning and data interpretation, bringing diagnostic imagin g and therapeutic capabilities closer to the patient, rather than the conve rse.