Image acquisition: Ultrasound, computed tomography, and magnetic resonance imaging

As the transition toward total digital image acquisition continues, radiology is transcending the current standard of two-dimensional (2-D) cross-sectional anatomic imaging to more complex models. Among these are three-dimensional (3-D) anatomic images, constructed either from a synthesis of traditional 2-D data sets, or directly from volumetrically acquired data. However, current trends are moving beyond mere anatomic imaging to include physiological data once mainly obtained via nuclear medicine. Recent magnetic resonance pulse sequences, in addition to Doppler and harmonic ultrasound methods, are providing insight into blood flow, oxygenation, and metabolite concentrations non-invasively. Through image registration techniques, these data (even from differing modalities) are being assembled into 2-D and 3-D "fusion" images that promise to revolutionize diagnosis. Furthermore, with improvements in miniaturization, reliability, speed, built-in intelligence, and ease of use, these new developments are finding their way into use by nonspecialists. For instance, a new hand-held ultrasound unit will likely become 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 of use for both scanning and data interpretation, bringing diagnostic imaging and therapeutic capabilities closer to the patient, rather than the converse.