Radiology studies - X-ray

Background

Conventional radiography is the most frequently used modality for evaluating bone and joint disorders, particularly those involving trauma. In general, the orthopedic radiologist should obtain at least two views of the bone(s) involved, at 90° angles to each other and each view showing two adjacent joints.¹

Historical Overview

The first radiograph was produced in 1895, when Wilhelm Roentgen took an x-ray image of his wife’s hand. To date, conventional radiography plays a critical role in diagnostic imaging. Until recently, all x-rays were produced using a film cassette on which to project the image. The film is then processed and printed. Computed radiography (CR) is a filmless system that substitutes a phosphor imaging plate for the film cassette. The resulting digital images are transferred to a computerized picture archiving and communication system (PACS), which uses computer networks to store and transmit the images to physicians for immediate access and in diverse locations. Digital radiography (DR) substitutes a fixed electronic detector, or charge-coupled device for the film cassette and phosphor plate.²

Description

X-rays are a form of radiant energy with a wavelength that is significantly shorter than that of visible light. Thus, x-rays can penetrate many substances that are opaque to light. The x-ray beam is produced by bombarding a tungsten target with an electron beam within an x-ray tube. As the x-rays pass through the body, they are attenuated via absorption and scatter by different bodily tissues. There are five radiographic densities ranked by the ability to attenuate the x-ray beam: air, fat, soft tissue, bone and metal. Substances that have little attenuating effects (eg, air, fat) appear darker than those that have large attenuating effects (eg, bone, metal). Thick structures attenuate more radiation than do thin structures of the same composition.²

Most radiographic views are named based on the direction the beam passes through the patient. The most common views are anteroposterior (AP; front to back), posteroanterior (PA; back to front), lateral (from the side) and oblique (at an angle). Radiographs are also named according to the position of the patient, including erect, supine and prone.²

The table below provides a summary of the conditions for which conventional radiography may help in diagnosis and includes a list of the routine and special views typically obtained.

Table. Conventional radiography: summary of diagnoses by recommended routine and special views

AP, anteroposterior; CMC, carpometacarpal; SLAC, scapholunate advanced collapse.

*Note: according to OrthoBullets, radiography is not needed for these diagnoses.