The authors discuss the assessment of the contribution of diagnostic imaging to the patient management process. A hierarchical model of efficacy is presented as an organizing structure for appraisal of the literature on efficacy of imaging. Demonstration of efficacy at each lower level in this hierarchy is logically necessary, but not sufficient, to assure efficacy at higher levels. Level 1 concerns technical quality of the images; Level 2 addresses diagnostic accuracy, sensitivity, and specificity associated with interpretation of the images. Next, Level 3 focuses on whether the information produces change in the referring physician's diagnostic thinking. Such a change is a logical prerequisite for Level 4 efficacy, which concerns effect on the patient management plan. Level 5 efficacy studies measure (or compute) effect of the information on patient outcomes. Finally, at Level 6, analyses examine societal costs and benefits of a diagnostic imaging technology. The pioneering contributions of Dr. Lee B. Lusted in the study of diagnostic imaging efficacy are highlighted.

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Abbreviations: BPH = benign prostatic hyperplasia, FLASH = fast low-angle shot, SE « spin echo.

The traditional goal of radiology has been to provide images of the highest technical quality that permit the most accurate diagnoses possible. From a more global perspective, diagnostic radiology is part of a larger system that has as its goal effective and efficient treatment of patients. A six-tiered hierarchical model of efficacy that includes this more global view is presented. This model is intended to improve understanding of the continuum that efficacy is and to conceptually relate efficacy to technology assessment and outcome research. Better understanding of efficacy/technology assessment and outcome research fostered by the model should encourage radiologists to participate actively in federally supported research in these areas. Those radiologists who do so will come to understand better how radiology can help patients and society as a whole. Use of the model's concepts should also aid radiologists in becoming more effective consultants to their clinical colleagues about optimal use of high-technology imaging from the perspectives of clinical efficacy, patient outcome, and societal efficacy.

It is not yet conclusively determined whether preoperative MR staging is appropriate, but results of decision analysis suggest that MR staging is cost-effective for men with moderate or high prior probability of extracapsular disease.