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Perspective |
1 Both authors: Department of Radiology, Indiana University School of Medicine, 702 N Barnhill Dr., Room 1053, Indianapolis, IN 46202-5200.
Received August 29, 2008; accepted after revision September 26, 2008.
Address correspondence to R. B. Gunderman
(rbgunder{at}iupui.edu).
OBJECTIVE. This article reviews major themes about imaging techniques with which all educators should be familiar.
CONCLUSION. A high-quality introduction to radiologic techniques should provide a basic framework to make good use of radiology in caring for patients. Tomorrow's physicians will need to make effective and efficient use of new imaging techniques. The responsibility for preparing them to do so rests squarely on the shoulders of today's radiology educators.
Keywords: education • imaging techniques • medical students
Medical educators realize that the growing role of radiologic imaging in health care calls for radiology to play a greater role in the medical school curriculum [1]. Issues such as how to develop a medical school radiology course and get it accepted by a curriculum committee have been examined before [2]. A key issue is the content of the course itself: What do medical students most need to learn about radiology [3]? A good course needs to accomplish a number of key objectives, but course developers must bear in mind that most students do not intend to pursue careers in radiology. The course needs to provide a working knowledge of the appropriate radiologic examination for different clinical situations. It needs to cover the basics of image interpretation, including urgent, life-threatening findings such as a pneumothorax or a malpositioned endotracheal tube. Yet before students can grasp what examination to order and what findings to look for, they need to understand the radiologic imaging techniques themselves. The appropriate approach will vary somewhat from institution to institution, but there are major themes about the imaging techniques that all educators should bear in mind. This article reviews these themes.
An effective imaging technique curriculum needs to suit the audience in question. Are the students studying radiology early or late in their medical school careers? Evidence shows that those who receive early instruction in radiology enter their clinical years with heightened familiarity and comfort with ordering radiologic studies, take a greater interest in the field, are more likely to enroll in radiology electives in the future, and have a deeper understanding of basic ideas and concepts that are central to radiology [4]. Yet it is certainly better that students encounter radiology late in medical school than not at all. In general, fourth-year students will grasp the clinical relevance of the imaging techniques more readily than first-year students. At whatever stage of training a radiology course is positioned, an obvious topic concerning the techniques is physics. This includes how x-rays, ultrasound beams, and gamma rays are produced and detected, as well as the differences between such basic imaging parameters as density, acoustic impedance, and T1 relaxation times of human tissues. A deeper understanding of the underlying physics permits more effective and efficient imaging [5]. However, addressing the traditional physics of each imaging technique only scratches the surface. Radiology educators should consider expanding the introduction of the imaging techniques to encompass additional topics.
Ample evidence indicates that many physicians know too little about ionizing radiation and share even less of what they do know with patients. In one study, only 7% of patients undergoing CT stated they were told about the risks and benefits of the study, and only 47% of radiologists, 9% of emergency department physicians, and 3% of patients believed that the ionizing radiation associated with radiologic imaging increases cancer risk [6]. In addition, only small percentages of emergency department physicians (22%) and radiologists (13%) were able to estimate accurately the radiation associated with one CT scan compared with a chest radiograph. Courses in radiology need to bring students up to speed concerning ionizing radiation. What are its biologic effects, and how do the dosage levels in contemporary medicine compare with background levels of exposure? Which imaging techniques involve the greatest doses, which involve relatively low doses, and which involve none at all? What steps can referring physicians take to lower patient exposures, such as forgoing unnecessary examinations, substituting lower-exposure examinations, and avoiding repeat examinations? Students need to realize that they can collaborate with radiologists to reduce exposures and learn how to talk with patients about the risks and benefits of radiologic imaging.
We believe that students should also glimpse the history of the radiologic imaging techniques. The development of radiology includes the stories of some of the greatest scientists and scientific discoveries of modern medicine. Who were Wilhelm Roentgen, Marie and Pierre Curie, and Godfrey Hounsfield? What motivated them, what obstacles did they overcome, what impact did they have, and what price did they pay for their discoveries? Understanding a bit of the history helps make the material more meaningful and therefore more memorable. It also helps students appreciate that the vast contemporary medical armamentarium was not born in a textbook but in the laboratories of great investigators. Seeing how radiology has changed medicine helps prepare students to become innovators in their own right [7].
Students need to grasp the costs involved in radiologic imaging. What are the typical charges for examinations involving radiography, sonography, CT, MRI, and nuclear medicine? How do the costs of the various imaging techniques compare with those of other forms of diagnostic testing, such as blood testing and surgical biopsy? What role should cost play in selecting the most appropriate diagnostic test? In a patient with suspected acute pulmonary thromboembolism, what is the charge for a stat CT pulmonary arteriogram, and how does it compare with keeping the patient a few extra hours in the hospital emergency department or admitting the patient overnight to the hospital? Future physicians should know that avoiding wasteful spending does not always mean choosing the lowest-cost diagnostic alternative [8].
Students also need to learn how to orient themselves to the various types of images. Issues that seem trivial to an experienced radiologist can prove quite vexing to a neophyte. Consider sonography. What are the standard imaging planes, and how are images labeled? Which side or end of the patient is located on the left side of the image? How does the image on the monitor change in response to changes in transducer position? Simple analogies such as slicing a loaf of bread can prove very useful in helping students understand what they are seeing. Students who feel lost when they look at radiologic images may feel less comfortable ordering radiologic examinations and make less-effective use of imaging in the care of their patients.
The same goes for the vocabulary of radiologic imaging. Why is it inappropriate to describe a lesion on CT as "hyperechoic," a lesion on MRI as "hyperdense," or a lesion on sonography as "photopenic"? Failure to use such basic terminology appropriately will expose students to embarrassment. More important, they may misinterpret what they read in a radiology report and perceive on the images, with adverse consequences for patients. For example, a student who thinks that a sonographically bright lesion is hyperdense may suppose that the lesion will be visible on radiographs, leading to an inappropriate workup. Understanding key radiologic terminology promotes effective communication between physicians, a vital and frequently neglected topic in medical education [9]. Today's medical students are tomorrow's referring physicians.
Perhaps even more important, students need to understand the common clinical uses of each imaging technique. What are the five most commonly ordered types of examinations in radiography, sonography, CT, MRI, and nuclear medicine? What are the common clinical situations, such as acute chest pain or extremity pain after trauma, in which radiographs are generally the first radiologic examination to order? What are situations in which radiographs are generally ill advised, such as closed-head trauma and suspected acute cholecystitis? In a patient with neurologic signs and symptoms, when is an unenhanced head CT generally the first examination to order, and when is MRI a better choice? All of these questions address the same general concept in clinical medicine: What is the next step [8]?
The clinical service...enters the radiologic "supermarket," whose shelves are increasingly filled with exotic and expensive studies, and orders tests....It is no indictment of clinical services to say that confusion surrounds the imaging workup.
As medical student educators, we often stress image interpretation when interpretation should probably take more of a back seat to appropriate test ordering. Decision support tools such as the American College of Radiology Appropriateness Criteria can serve as valuable educational resources in this regard [9, 10]. Nevertheless, students certainly need to be able to recognize common and urgent imaging findings, such as intracranial hemorrhage and pneumoperitoneum. Basic image interpretation skills become vital no later than the first year of postgraduate medical training [2, 11]. Students also need to encounter common imaging artifacts and technical factors, such as skin folds and metallic streak artifact, as well as chest radiographs compromised by patient rotation, motion, and underinflation. They need to become acquainted with common mimics of pathology, such as calcifications in the costochondral cartilage, the choroid plexus, and uterine leiomyomata. Just as every headache does not indicate subarachnoid hemorrhage and every rash does not indicate measles, every abnormal bright area on a radiologic image does not indicate a serious abnormality.
Students also need to understand the basics of contrast agents. In one institution, the number of adverse reactions to IV contrast agents went up from 45 in 1999 to 179 in 2005, driven largely by a corresponding increase in the number of cases in which contrast agents were administered [12]. What is a contrast agent, and how do the different contrast agents affect images produced by different techniques? How is the patient's experience affected when an examination is ordered with an oral or IV contrast agent? In what clinical settings are oral and IV contrast agents indicated? In what situations, such as suspected urolithiasis, might the contrast agent obscure important findings? What patient issues, such as a history of adverse reaction and current renal function, need to be addressed before administering IV contrast agents? Students also need a basic sense of how to manage adverse reactions to contrast agents.
Finally, students need to gain a basic understanding of the relative strengths and weaknesses of the various imaging techniques. They need to know which techniques provide the greatest spatial resolution and which offer the most physiologic information. They need to know that sonography is often superb for evaluating superficial soft-tissue lesions but performs poorly in the evaluation of aerated lung and subcortical bone. They need to know that MRI is the preferred imaging technique for nonacute brain imaging and suspected spinal cord compression but is contraindicated in patients with electrical devices such as pacemakers. What are the relative advantages and disadvantages of a radiologic examination such as a barium upper GI study compared with endoscopy?
A high-quality basic introduction to radiologic imaging techniques should not aim to turn medical students into junior radiologists. Instead, it should provide them with a basic framework to make good use of radiology in caring for their patients. Physicians place a premium on understanding, and many will underuse, overuse, or misuse imaging techniques that they feel uncomfortable with. It is in everyone's interest—the referring physician; the radiologist; and, above all, the patient—that tomorrow's physicians make effective and efficient use of each of the radiologic imaging techniques. The responsibility for preparing them to do so rests squarely on the shoulders of today's radiology educators.
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