Computed tomography in clinical practice

doi:10.1136/bmj.324.7345.1077

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Conall J Garvey, consultant radiologist (Conall.garvey@rlbuh-tr.nwest.nhs.uk),
Rebecca Hanlon, specialist registrar in radiology

Royal Liverpool University Hospital, Liverpool L7 8XP

Correspondence to: C J Garvey

Since it was first introduced three decades ago, computed tomography has become an important investigative tool. Conall Garvey and Rebecca Hanlon explain different types of scanners and what they are used for

Computed tomography was first introduced 30 years ago and has since become an integral part of clinical practice.1 Because of rapid advances in technology few clinicians are aware of the scope and limitations of the different types of scanners. This review describes the three main types of computed tomographic scanner that are used in routine clinical practice and discusses their use in the investigation of a wide range of different conditions. It also flags up differing views on the relative merits of computed tomography versus magnetic resonance imaging.

Summary points

The role of “conventional” computed tomography is declining and has been superseded by spiral scanning

Multislice scanning is faster and more versatile than spiral scanning and facilitates newer applications, particularly in vascular, cardiac, and colonic imaging

Multislice computed tomography is expensive and has implications for workload and data storage

Concern has been raised about the increasing radiation dose from examinations by computed tomography

As magnetic resonance scanners become faster and availability increases, considerations of dose may relegate computed tomography to a secondary role for many applications

Methods

The information contained in this review was gathered from several sources. These include many years of personal experience using computed tomography and magnetic resonance imaging, discussions with manufacturers of equipment, and knowledge of radiation dosimetry issues, supported by a search of Medline and the Cochrane databases for systematic reviews comparing computed tomography and magnetic resonance imaging.

Evolution of computed tomographic scanners

By today's standards early computed tomographic scanners were extremely slow and required enormous computer facilities to generate comparatively crude scans. Improvements in tube technology and computer hardware and software have shortened scan times and improved the resolution …