Chapter 105. Introduction to Radiology

1. What determines the ability of plain films to differentiate between various substances and tissues? What are the limitations of a single radiographic view?

2. What are the limitations of ultrasound?

3. In addition to the five categories of density, computed tomography (CT) technology is able to detect what differences? What are Hounsfield units?

4. What are the limitations of magnetic resonance imaging (MRI)?

5. What are the advantages of nuclear imaging?

The radiology examination that provides the required data with the least amount of radiation, expense, and need for extraneous follow-up supports the best practices of patient care. Although radiologic examinations have become vital adjuncts to clinical problem-solving, they should not replace the process of developing a coherent problem list generated by the patient's concerns, medical history, and physical examination. The ordering physician critically contributes to the process of radiology interpretation not only by asking the right questions of individual patients, but by selecting the right examination and effectively communicating the questions that need to be answered by imaging to patients, technologists, and radiologists. The physician should request only those studies that will influence management, continually filter the results in the context of the patient, and ensure appropriate follow-up of abnormal and incidental findings. Practitioners must not only balance risks and benefits of a specific study for an individual patient but also be mindful of the impact of clinical decision-making on populations of patients even if the test is readily available.

Ever-expanding technologies will always require the expertise of radiologists in interpretation; however, physicians must have a basic understanding of various imaging modalities, their limitations, risks, and relative costs in order to select the right examination for a specific patient.

This chapter will introduce general concepts for different imaging modalities, how to “interpret” the radiology report, and what to do about “incidental findings” in the context of care transitions and handoffs. Chapter 106 will review principles of patient safety—risks of contrast, radiation exposure, and gadolinium. Subsequent chapters will cover the application of specific imaging modalities.