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(Radiology. 2000;216:1-7.)
© RSNA, 2000

Reflections

Gastrointestinal Radiology in the United States: An Overview of the Past 50 Years1

Henry I. Goldberg, MD and Alexander R. Margulis, MD 2

1 From the Department of Radiology, University of California San Francisco, San Francisco, CA 94143-0628. Received October 29, 1999; revision requested December 7; revision received January 14, 2000; accepted January 27. Address correspondence to H.I.G. (e-mail: henry.goldberg@radiology.ucsf.edu).

ABSTRACT

Gastrointestinal radiology has expanded its scope beyond conventional abdominal radiography, barium studies, and cholecystography. Ultrasonography allows imaging of solid abdominal organs and the intestine without the use of radiation. Computed tomography now allows comprehensive assessment of abdominal and pelvic inflammatory and infectious processes, obstruction, tumor detection and staging, and display of vasculature and blunt trauma effects that were not possible 50 years ago. Magnetic resonance imaging provides multiplanar imaging to the same degree, without the use of radiation. Barium studies of the gastrointestinal tract, enteroclysis for small-bowel assessment, and conventional radiography still have a role, despite the extensive use of fiberoptic endoscopy. Fluoroscopy is still important, but great advances in technologies have changed gastrointestinal radiology irrevocably.

Index terms: Gastrointestinal tract, CT, 70.12111, 70.12112, 70.12113, 70.12114, 70.12115 • Gastrointestinal tract, MR, 70.121411, 70.121412, 70.12142 • Gastrointestinal tract, radiography, 70.123, 70.127, 70.128 • Gastrointestinal tract, US, 70.12981, 70.12983, 70.12988 • Radiology and radiologists, history • Reflections

With the arrival of the new century, the field of gastrointestinal imaging bears only a vague resemblance to gastrointestinal radiology in 1950. Fifty years of technical developments, organizational changes, and educational advances have inexorably altered the nature and composition of gastrointestinal radiology. No attempt will be made to mention every advance in gastrointestinal radiology in this review, but rather we provide an overview of the changes in the past 50 years.

The 1950s

In the 1950s, gastrointestinal radiology consisted of two methods to assess the digestive tract—conventional radiography and single-contrast barium examination. Fluoroscopy was considered to be a "special" technique, and a substantial portion of all residents' training in gastrointestinal radiology services was devoted to learning this high-technology procedure. Fluoroscopy units were equipped with fluorescent screens, which required radiologists to wear red goggles for 10–15 minutes to dark adapt their vision. The anatomy and pathology of the gastrointestinal tract had been catalogued on the basis of these single-contrast studies.

Few radiologists were considered to be specialists in gastrointestinal radiology and the fine art of fluoroscopy. All staff radiologists at university and private hospitals performed some gastrointestinal fluoroscopy. A few professors of radiology explored the specialty in detail and taught the general radiologists of that time. These teachers and investigators included Carman, Hampton, Hodges, Schatzki, Rigler, Wolf, Marshak, Singleton, and Margulis (1–8). No specialty society of gastrointestinal radiologists existed, however, and there were no special trainee grants or fellowships in gastrointestinal radiology.

In the everyday hospital setting, the "plain film" (the term "conventional radiograph" came much later) was the mainstay of nonsurgical diagnosis of abdominal disease. In the diagnosis of diseases of the esophagus, stomach, small bowel, and colon, single-contrast gastrointestinal studies were considered to be the reference standard, since endoscopy was performed by using a straight, nonflexible, metal endoscope, which limited its use. The gastroenterologists and surgeons depended heavily on gastrointestinal radiologic studies.

The only gastrointestinal organs outside the digestive tract that were specifically imaged in the 1950s were the gallbladder and bile ducts. Cholecystography with oral contrast material, which had been introduced as a clinical study in 1925 by Graham et al (9), was used to help diagnose gallstones in the 1950s. Hoppe and Archer (10) introduced iopanoic acid in 1957, which became a model compound for opacifying the gallbladder. It was not until almost 20 years later that B-mode ultrasonography (US) was introduced as a method to help detect gallstones. Cholangiography with intravenously administered contrast material was in its infancy, and adipiodine, a precursor to iodipamide, was the contrast agent.

The 1960s

Major changes in the techniques, equipment, academic focus, and training in gastrointestinal radiology occurred in the 1960s. Double-contrast techniques with air and barium sulfate came into their own. Major contributors to the introduction of this technique came from Sweden, the United States, and Japan and included Welin (11), Miller (12), and Shirakabe (13). These techniques resulted in a redefinition of radiographic detection of diseases of the gastrointestinal tract. Small ulcers, early carcinomas, early findings of Crohn disease, and small colonic polyps were subsequently characterized as a result of air-barium double-contrast studies (14–16).

Air-barium techniques could not have been successfully applied to the study of the gastrointestinal tract in the 1960s without the concurrent development of image intensifiers. These replaced "green screen" fluoroscopes and permitted better resolution for visual inspection of the gastrointestinal tract (17). Although the introduction of the multiple-film multiple-panel alternator was not as dramatic as the advent of the image intensifier, it too influenced gastrointestinal radiology by permitting the rapid display and comparison of large numbers of images.

In the middle 1960s, the National Institutes of Health initiated training grants in diagnostic radiology. These grants permitted academic radiology departments to support fellowships in specialty areas, including gastrointestinal radiology. Many of the National Institutes of Health trainees in gastrointestinal radiology in the 1960s and early 1970s became leaders in the field. These grants provided a critical mass of gastrointestinal radiologists with both clinical and research talents, which led to the eventual establishment of the Society of Gastrointestinal Radiologists.

The 1970s

In the 1970s, the Society of Gastrointestinal Radiologists was founded by Drs Alexander Margulis, Richard Marshak, William Seaman, Walter Whitehouse, and H. Joachim Burhenne. The society's goals were to advance the specialty, promote research, and develop guidelines for quality training of residents and fellows in gastrointestinal radiology. The society now has 365 members, 39 of whom are international members.

By the middle to late 1970s, major advances in imaging of the gastrointestinal tract had occurred because of technical innovations. With these innovations came the need for more focused specialized training in gastrointestinal radiology.

The major influence of B-mode US in gastrointestinal radiology was in the assessment of gallstones and gallbladder abnormalities (18,19). During the 1970s, US became more disseminated and, therefore, became a major competitor with cholecystography for evaluation of gallstones. Refinements in US resulted in the preeminence of gallbladder US, as compared with cholecystography, so that by the end of the decade, the use of cholecystography was greatly diminished (Fig 1).



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  		Figure 1a. (a) Cholecystogram obtained after oral administration of contrast material demonstrates excellent opacification of the gallbladder without evidence of stones. (b) US image obtained 1 day after a illustrates the increased sensitivity of US for detection of stones (curved arrow) in the presence of an otherwise normal-appearing gallbladder (straight arrow). The cholecystogram has become a "museum piece" in the United States as the result of US. This may be related more to the convenience of obtaining US images of the gallbladder, particularly in the acutely ill patient, than to its overall superiority for help in detecting stones.

 


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  		Figure 1b. (a) Cholecystogram obtained after oral administration of contrast material demonstrates excellent opacification of the gallbladder without evidence of stones. (b) US image obtained 1 day after a illustrates the increased sensitivity of US for detection of stones (curved arrow) in the presence of an otherwise normal-appearing gallbladder (straight arrow). The cholecystogram has become a "museum piece" in the United States as the result of US. This may be related more to the convenience of obtaining US images of the gallbladder, particularly in the acutely ill patient, than to its overall superiority for help in detecting stones.

 
During the middle 1970s, computed tomography (CT) was first applied to abdominal imaging. In 1976, the EMI Corporation in England, pioneered the first body scanner, which acquired an image in 18 seconds. This development was quickly advanced by all the current CT scanner manufacturers. It immediately became apparent that this single development was to change the scope of gastrointestinal radiology (20,21). The impact of abdominal CT on imaging of gastrointestinal disease in the early days was confined mainly to assessment of the liver and pancreas. Technical limitations in scanning time and resolution limited the detection and characterization of lesions in these solid organs. However, the pancreas, in particular, became "visible" for the first time. Although US was being explored, CT quickly became the imaging modality of choice in the United States for assessment of the pancreas.

At approximately the same time, flexible fiberoptic endoscopes were developed and introduced by Basil Hirschowitz and colleagues (22). The effect of this innovation, which allowed direct visualization of the lumina of the esophagus, stomach, and colon, was enormous. By the end of the 1970s it became obvious that gastroenterologists, who pioneered the use of flexible fiberoptic endoscopy, had developed a new reference standard for detection of diseases of the upper and lower portions of the gastrointestinal tract. The evaluation of esophagus, stomach, and colon was no longer the sole realm of the radiologist. By the time the 1980s came to a close, the radiographic evaluation of the esophagus, stomach, and colon—even with the improvements in imaging with double-contrast techniques—was supplanted to a large degree by endoscopy. This change in referral pattern reflected the fact that gastroenterologists directed patient disposition. The fact that many physicians believed that fiberoptic endoscopy was more accurate than even the best air contrast techniques, whether true or not, also diminished the number of referrals to radiologists.

With fiberoptic endoscopy came the development of endoscopic retrograde cholangiopancreatography (ERCP) (23,24). This technique permitted assessment of the biliary and pancreatic ducts by using fluoroscopic images. Radiologists were presented with an increasing number of cases of biliary and pancreatic disease, and this stimulated a medical educational effort to familiarize radiologists with the appearance of such pathologic conditions. Diagnostic percutaneous transhepatic cholangiography all but disappeared in hospitals and facilities that had ERCP capabilities.

Cine fluoroscopy also became a useful clinical tool to assess intestinal motility during the 1970s. This technical advance permitted documentation of esophageal, gastric, and small-bowel peristalsis. The result was more accurate description of the motility of the gastrointestinal tract in normal and pathologic conditions, providing information not available with endoscopy (25). In particular, the ability to record the complex mechanism of swallowing led to the development of a new assessment of abnormal swallowing in patients with stroke and in those who had undergone neck surgery or had experienced trauma. Speech pathologists and radiologists began to work together to evaluate and remedy swallowing difficulties.

The 1980s and Beyond

In the 1980s, the major developments that influenced gastrointestinal radiology were (a) further improvement in abdominal CT scanning speed and spatial resolution and (b) application of magnetic resonance (MR) imaging to the assessment of the liver, spleen, and, to some degree, pancreas.

The development of rapid (2-second) scanning speeds, improved tube cooling capabilities, and refinements in intravenous contrast media injection techniques resulted in a veritable revolution in the application of CT to imaging of the liver, pancreas, spleen, and even the gastrointestinal tract itself. The mural and extramural aspects of diseases of the bowel wall were well demonstrated with CT. These CT advances were accomplished quite early in the 1980s and included demonstration both of inflammatory processes such as appendicitis, diverticulitis, Crohn disease, and small-bowel obstruction and of primary neoplasms such as adenocarcinoma and lymphoma. Staging systems that made use of CT were developed to characterize primary bowel malignancies (26–29).

Detection and characterization of hepatic and pancreatic neoplasms in the 1980s occurred with three parallel imaging strategies—US, CT, and MR imaging. During this decade of development in these three modalities, the ability to detect focal lesions in the liver improved. Increased image resolution and the addition of intravenously administered contrast agents for both CT and MR imaging (gadolinium chelates) helped improve detection and characterization (30–32). The rapid development of new faster sequences and respiratory gating (33) permitted imaging of the abdomen with greater clarity, because motion artifacts caused less degradation of the images. During the 1980s, screening for hepatocellular carcinoma was performed with US and, increasingly, with contrast-enhanced CT. There were some reports of increased sensitivity of MR imaging (32,34), but for the most part, the emergence of MR imaging as a screening technique awaited further refinements in the 1990s in terms of the development of contrast agents other then gadolinium chelates, more sensitive coils, and faster and more specialized sequences. CT became the major method for aid in detecting pancreatic carcinoma, with little role for either US or MR imaging at that time.

With the increasing use and availability of MR imaging and CT, several societies were formed to promote the interchange of ideas and information and provide continuing medical education for practicing radiologists. These included the Society of Computed Body Tomography and Magnetic Resonance and the Society of Magnetic Resonance in Medicine. The teaching of CT and MR techniques and interpretation became integrated into radiology residency programs. Many university departments developed sections for CT and MR imaging.

By the year 2000, the scope of gastrointestinal radiology has expanded to include areas of imaging and therapy not even suspected in 1950. What was once a discipline confined to conventional abdominal radiography and barium studies has expanded to encompass not only the gastrointestinal tract but also the major abdominal organs such as the liver, spleen, and pancreas. In fact, the term gastrointestinal radiology itself is being replaced by the term "abdominal imaging" at many radiology centers, reflecting the increased scope and multitude of imaging techniques.

Although conventional radiography of the abdomen is still used, its application has been limited to bedside imaging and the initial evaluation of abdominal distention, possible small-bowel obstruction, intestinal ischemia, evidence of pneumoperitoneum and, perhaps, to the detection of ureteral stones. At many centers, CT has almost totally replaced conventional radiography as a screening technique for most acute abdominal processes. These include appendicitis, acute pancreatitis, acute diverticulitis, blunt trauma to the abdomen, possible abdominal abscess, volvulus, intussusception, and possible perforation; it is also used to aid in detection of an ischemic bowel when the conventional radiograph is not helpful and in evaluation of small-bowel obstruction due to adhesion tumors (35–42). With the wide distribution of helical CT in the United States, CT has at present become the imaging test that provides the highest information content. Also, the new multidetector-array CT scanners provide even greater opportunities for detection and characterization of abdominal pathologic conditions (43).

It is interesting to reflect on the changes that have occurred in imaging of the gastrointestinal tract by focusing on one common disease process: small-bowel obstruction (Fig 2). In the late 1950s, conventional radiography and single-contrast barium small-bowel examinations were used for diagnosis. In the late 1970s and the 1980s, enteroclysis was introduced as a method to increase the rapidity and sensitivity for diagnosis of small-bowel obstruction (45). In the 1990s, the benefits of CT in patients with conventional radiographic evidence of small-bowel obstruction became known, particularly for determining the cause (ie, strangulation with or without infarction and necrosis, volvulus, tumor, metastasis, Crohn disease) (39,40,45–47). Most recently MR imaging has been used to help evaluate the small bowel (45), which has led to speculation that MR imaging will join the cast of imaging techniques that are available for evaluation of small-bowel obstruction.



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  		Figure 2a. The addition of newer techniques for detection and characterization of small-bowel obstruction has affected the treatment of patients during the past 50 years. The following images represent five patients. (a) Radiograph of the abdomen obtained in a patient in the supine position shows extensively dilated small bowel with no colonic air. This image represents the primary study of small-bowel obstruction. Conventional radiography has persisted over the past 50 years. (b) Small-bowel barium study obtained with a transit time of 3 hours is an ideal depiction of obstruction (arrow). Barium study was the only other technique available in the 1950s and 1960s to help analyze obstruction. (c) Radiograph obtained at enteroclysis, which was introduced in the late 1970s, provides additional options for help in the detection and characterization of small-bowel obstruction, which is shown here as an abrupt termination (arrow) of the barium column. The cause of obstruction in this patient was tumor implants (metastases) on the bowel from recurrent ovarian cancer. The results were obtained 20 minutes after intubation. (d) The use of CT scans, introduced in the 1980s, to evaluate suspected small-bowel obstruction extended the ability of radiologists to characterize the cause of obstruction. This transverse CT scan demonstrates multiple segments of small-bowel dilatation caused by an incarcerated bowel loop (arrow) in an anterior abdominal wall hernia. (e) The newest technique to be applied to evaluation of the small bowel is MR imaging. By using water as a contrast agent and a coronal T2-weighted single-shot fast spin-echo technique (repetition time = {infty}, echo time = 280 msec, 40-mm section thickness), the bowel lumen, fold pattern, and relationship of one segment to another can be shown. It is yet to be determined where MR imaging will fit in the algorithms for imaging of small-bowel obstruction. (Reprinted, with permission, from reference 44.)

 


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  		Figure 2b. The addition of newer techniques for detection and characterization of small-bowel obstruction has affected the treatment of patients during the past 50 years. The following images represent five patients. (a) Radiograph of the abdomen obtained in a patient in the supine position shows extensively dilated small bowel with no colonic air. This image represents the primary study of small-bowel obstruction. Conventional radiography has persisted over the past 50 years. (b) Small-bowel barium study obtained with a transit time of 3 hours is an ideal depiction of obstruction (arrow). Barium study was the only other technique available in the 1950s and 1960s to help analyze obstruction. (c) Radiograph obtained at enteroclysis, which was introduced in the late 1970s, provides additional options for help in the detection and characterization of small-bowel obstruction, which is shown here as an abrupt termination (arrow) of the barium column. The cause of obstruction in this patient was tumor implants (metastases) on the bowel from recurrent ovarian cancer. The results were obtained 20 minutes after intubation. (d) The use of CT scans, introduced in the 1980s, to evaluate suspected small-bowel obstruction extended the ability of radiologists to characterize the cause of obstruction. This transverse CT scan demonstrates multiple segments of small-bowel dilatation caused by an incarcerated bowel loop (arrow) in an anterior abdominal wall hernia. (e) The newest technique to be applied to evaluation of the small bowel is MR imaging. By using water as a contrast agent and a coronal T2-weighted single-shot fast spin-echo technique (repetition time = {infty}, echo time = 280 msec, 40-mm section thickness), the bowel lumen, fold pattern, and relationship of one segment to another can be shown. It is yet to be determined where MR imaging will fit in the algorithms for imaging of small-bowel obstruction. (Reprinted, with permission, from reference 44.)

 


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  		Figure 2c. The addition of newer techniques for detection and characterization of small-bowel obstruction has affected the treatment of patients during the past 50 years. The following images represent five patients. (a) Radiograph of the abdomen obtained in a patient in the supine position shows extensively dilated small bowel with no colonic air. This image represents the primary study of small-bowel obstruction. Conventional radiography has persisted over the past 50 years. (b) Small-bowel barium study obtained with a transit time of 3 hours is an ideal depiction of obstruction (arrow). Barium study was the only other technique available in the 1950s and 1960s to help analyze obstruction. (c) Radiograph obtained at enteroclysis, which was introduced in the late 1970s, provides additional options for help in the detection and characterization of small-bowel obstruction, which is shown here as an abrupt termination (arrow) of the barium column. The cause of obstruction in this patient was tumor implants (metastases) on the bowel from recurrent ovarian cancer. The results were obtained 20 minutes after intubation. (d) The use of CT scans, introduced in the 1980s, to evaluate suspected small-bowel obstruction extended the ability of radiologists to characterize the cause of obstruction. This transverse CT scan demonstrates multiple segments of small-bowel dilatation caused by an incarcerated bowel loop (arrow) in an anterior abdominal wall hernia. (e) The newest technique to be applied to evaluation of the small bowel is MR imaging. By using water as a contrast agent and a coronal T2-weighted single-shot fast spin-echo technique (repetition time = {infty}, echo time = 280 msec, 40-mm section thickness), the bowel lumen, fold pattern, and relationship of one segment to another can be shown. It is yet to be determined where MR imaging will fit in the algorithms for imaging of small-bowel obstruction. (Reprinted, with permission, from reference 44.)

 


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  		Figure 2d. The addition of newer techniques for detection and characterization of small-bowel obstruction has affected the treatment of patients during the past 50 years. The following images represent five patients. (a) Radiograph of the abdomen obtained in a patient in the supine position shows extensively dilated small bowel with no colonic air. This image represents the primary study of small-bowel obstruction. Conventional radiography has persisted over the past 50 years. (b) Small-bowel barium study obtained with a transit time of 3 hours is an ideal depiction of obstruction (arrow). Barium study was the only other technique available in the 1950s and 1960s to help analyze obstruction. (c) Radiograph obtained at enteroclysis, which was introduced in the late 1970s, provides additional options for help in the detection and characterization of small-bowel obstruction, which is shown here as an abrupt termination (arrow) of the barium column. The cause of obstruction in this patient was tumor implants (metastases) on the bowel from recurrent ovarian cancer. The results were obtained 20 minutes after intubation. (d) The use of CT scans, introduced in the 1980s, to evaluate suspected small-bowel obstruction extended the ability of radiologists to characterize the cause of obstruction. This transverse CT scan demonstrates multiple segments of small-bowel dilatation caused by an incarcerated bowel loop (arrow) in an anterior abdominal wall hernia. (e) The newest technique to be applied to evaluation of the small bowel is MR imaging. By using water as a contrast agent and a coronal T2-weighted single-shot fast spin-echo technique (repetition time = {infty}, echo time = 280 msec, 40-mm section thickness), the bowel lumen, fold pattern, and relationship of one segment to another can be shown. It is yet to be determined where MR imaging will fit in the algorithms for imaging of small-bowel obstruction. (Reprinted, with permission, from reference 44.)

 


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  		Figure 2e. The addition of newer techniques for detection and characterization of small-bowel obstruction has affected the treatment of patients during the past 50 years. The following images represent five patients. (a) Radiograph of the abdomen obtained in a patient in the supine position shows extensively dilated small bowel with no colonic air. This image represents the primary study of small-bowel obstruction. Conventional radiography has persisted over the past 50 years. (b) Small-bowel barium study obtained with a transit time of 3 hours is an ideal depiction of obstruction (arrow). Barium study was the only other technique available in the 1950s and 1960s to help analyze obstruction. (c) Radiograph obtained at enteroclysis, which was introduced in the late 1970s, provides additional options for help in the detection and characterization of small-bowel obstruction, which is shown here as an abrupt termination (arrow) of the barium column. The cause of obstruction in this patient was tumor implants (metastases) on the bowel from recurrent ovarian cancer. The results were obtained 20 minutes after intubation. (d) The use of CT scans, introduced in the 1980s, to evaluate suspected small-bowel obstruction extended the ability of radiologists to characterize the cause of obstruction. This transverse CT scan demonstrates multiple segments of small-bowel dilatation caused by an incarcerated bowel loop (arrow) in an anterior abdominal wall hernia. (e) The newest technique to be applied to evaluation of the small bowel is MR imaging. By using water as a contrast agent and a coronal T2-weighted single-shot fast spin-echo technique (repetition time = {infty}, echo time = 280 msec, 40-mm section thickness), the bowel lumen, fold pattern, and relationship of one segment to another can be shown. It is yet to be determined where MR imaging will fit in the algorithms for imaging of small-bowel obstruction. (Reprinted, with permission, from reference 44.)

 
Helical CT, with improved data acquisition speed and data display, has changed the approach in the patient who has experienced blunt trauma to the abdomen. It is interesting to recognize that CT was applied in cases of blunt trauma long before the development of helical CT (41). Survey examination with intravenous contrast material permits assessment of damage to the liver, spleen, pancreas, and gastrointestinal tract, as well as the rest of the abdomen and pelvis. Stable patients now can be examined with one modality that will provide information about the presence of peritoneal or retroperitoneal bleeding, organ damage, and even bowel perforation. The unstable patient now is examined with US at the emergency room to determine whether blood is present in the abdomen. The entire triage procedure has greatly facilitated assessment of the trauma patient (42).

A large percentage of the abdominal imaging studies currently performed are related to tumor detection, staging, and treatment follow-up in all abdominal organs. Fifty years ago, while detection of esophageal, gastric, and colonic tumors was part of the overall mission of gastrointestinal radiology, detection of tumors in solid organs was not possible, nor was tumor staging. Both CT and MR imaging have now assumed the role of primary techniques for tumor detection and staging, with US being used in the United States primarily for guidance during needle biopsy of liver lesions and other large abdominal masses. CT has become the major technique for guidance in needle biopsy of deeper abdominal masses and pancreatic lesions. The development of CT fluoroscopy (48) may provide even greater success in targeting lesions, and the development of open magnets to facilitate interventional MR techniques will increase the ability of radiologists to use MR imaging guidance for needle biopsy of tumors.

Perhaps the most dramatic development in gastrointestinal radiology over the past 50 years has been the ability to image the pancreas, pancreatic ducts and vessels, and adjacent lymph nodes. The only clues to the presence of pancreatic disease 50 years ago were changes in the size and contour of the duodenum or a greater curvature of the stomach on barium studies—an indication of advanced inflammation or the presence of a mass. Current pancreatic imaging techniques provide answers that were not previously available. Staging of pancreatitis and detection and staging of adenocarcinoma are readily accomplished by using multiphase contrast-enhanced helical CT, which can demonstrate tumor extent, encasement of vessels, and spread to local lymph nodes (49). MR imaging performed with special coils and contrast agents can demonstrate islet cell tumors as small as 1 cm in diameter (50).

Detection of focal and diffuse liver disease has also dramatically progressed since the 1950s, when liver disease was evaluated by means of laboratory tests and biopsy. All three of the currently used modalities for characterizing the liver—US, CT, and MR imaging—have contributed greatly to the radiologist's ability to detect, characterize, and stage metastases, primary hepatocellular carcinoma, bile duct carcinomas, fatty infiltration, hemochromatosis, cirrhosis, and Budd-Chiari syndrome (Fig 3). The addition of contrast agents for US have made this modality versatile for help in evaluating different types of liver lesions (51,52). Harmonic US, the result of the use of microbubble contrast agents, and the specialized technique of pulse-inversion imaging, which optimizes detection with signals from contrast agents, increase the conspicuity of malignant liver lesions.



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  		Figure 3a. The application of CT for help in detection and characterization of hepatic lesions has revolutionized the management of hepatic malignancies by permitting directed surgical resection, directed infusion chemotherapy, and chemical ablation of tumors. (a) Transverse CT scan of the liver (acquisition time, 18 seconds) obtained in 1976 without use of intravenous contrast material. No hepatic lesion is depicted despite the proved presence of a 4-cm-diameter hepatocellular carcinoma lesion. (b) Transverse CT scan in a different patient was obtained in 1999 by using helical CT technology and a triple-phase contrast enhancement protocol. This portal venous phase image demonstrates a lesion (arrow) posteriorly distributed in the right lobe. The lesion has both hypo- and hypervascular components. (c) Transverse arterial phase CT scan in the same patient as in b demonstrates not only the dominant right lobe lesion but also multiple small hypervascular lesions (arrows) in the anterior portion of the right lobe and throughout all segments of the left lobe. This information aids the surgeon in designating this cancer as inoperable. If the portal venous phase image alone had been obtained, a different decision might have been made.

 


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  		Figure 3b. The application of CT for help in detection and characterization of hepatic lesions has revolutionized the management of hepatic malignancies by permitting directed surgical resection, directed infusion chemotherapy, and chemical ablation of tumors. (a) Transverse CT scan of the liver (acquisition time, 18 seconds) obtained in 1976 without use of intravenous contrast material. No hepatic lesion is depicted despite the proved presence of a 4-cm-diameter hepatocellular carcinoma lesion. (b) Transverse CT scan in a different patient was obtained in 1999 by using helical CT technology and a triple-phase contrast enhancement protocol. This portal venous phase image demonstrates a lesion (arrow) posteriorly distributed in the right lobe. The lesion has both hypo- and hypervascular components. (c) Transverse arterial phase CT scan in the same patient as in b demonstrates not only the dominant right lobe lesion but also multiple small hypervascular lesions (arrows) in the anterior portion of the right lobe and throughout all segments of the left lobe. This information aids the surgeon in designating this cancer as inoperable. If the portal venous phase image alone had been obtained, a different decision might have been made.

 


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  		Figure 3c. The application of CT for help in detection and characterization of hepatic lesions has revolutionized the management of hepatic malignancies by permitting directed surgical resection, directed infusion chemotherapy, and chemical ablation of tumors. (a) Transverse CT scan of the liver (acquisition time, 18 seconds) obtained in 1976 without use of intravenous contrast material. No hepatic lesion is depicted despite the proved presence of a 4-cm-diameter hepatocellular carcinoma lesion. (b) Transverse CT scan in a different patient was obtained in 1999 by using helical CT technology and a triple-phase contrast enhancement protocol. This portal venous phase image demonstrates a lesion (arrow) posteriorly distributed in the right lobe. The lesion has both hypo- and hypervascular components. (c) Transverse arterial phase CT scan in the same patient as in b demonstrates not only the dominant right lobe lesion but also multiple small hypervascular lesions (arrows) in the anterior portion of the right lobe and throughout all segments of the left lobe. This information aids the surgeon in designating this cancer as inoperable. If the portal venous phase image alone had been obtained, a different decision might have been made.

 
Multiphase helical CT has become the standard for overall staging of liver tumors at many institutions. The three-phase study (arterial, portal venous, and delayed) has helped markedly increase detection of hepatic lesions (53,54). CT clearly is being challenged by MR imaging because of the combination of new contrast agents and more sensitive and specific sequences and the lack of radiation exposure. The array of new sequences (single-shot fast spin echo, echo planar, fat-suppressed T2 weighted) can be tailored to help detect the wide variety of lesions encountered (55,56).

In the evaluation of biliary tract disease, particularly stones, a new technique, MR cholangiopancreatography (MRCP), has emerged as an important method for assessment of biliary intraductal abnormalities. MRCP is fast, accurate, noninvasive (unlike ERCP), and does not require the use of contrast agents. Stones as small as 3 mm in diameter, as well as strictures and intraluminal masses, can be detected. MRCP may rival US as the screening method for ductal evaluation, particularly because MRCP provides a good demonstration of the distal common bile duct and pancreatic duct (57,58).

While flexible sigmoidoscopy and the air-barium double-contrast examination now share screening duties for the detection of colon polyps and cancers (according to guidelines of the American Cancer Society [59]), the development of CT colonography (virtual colonoscopy) and, probably, MR colonography, which provide three-dimensional displays of the lumen of the colon, may alter these guidelines in the next few years (Fig 4). Necessitating only a standard colon-cleansing preparation (similar to that for colonoscopy) and the appropriate software and hardware updates for helical CT, CT colonography may be the ideal screening technique because it causes no patient discomfort other than insufflation of air or carbon dioxide into the colon. It is rapid and does not require the use of contrast material or sedation. The ability to detect polyps probably equals that possible with colonoscopy, but as yet the specificity of CT colonography is not as high as that of colonoscopy. With the additions of software that can "straighten" the colon image to a linear tube and computer-aided programs that can be used to identify areas of abnormality, CT colonography would appear to have a bright future—a future never dreamed of in 1950 (60). Not to be left behind, MR imaging investigators (61) are also developing similar capabilities. We may soon have a choice between MR colonography and CT colonography.



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  		Figure 4a. Detection of colon polyps in the 1950s was accomplished by means of single-contrast barium enema studies. Fifty years later, imaging for detection of polyps has evolved to include CT colonography and, perhaps, MR colonography. (a) Single-contrast barium enema study obtained in 1959 demonstrates a polyp (arrow) with a long stalk. (b) CT colonographic image obtained in a different patient in 1999 illustrates the ability of this technique to characterize the colonic surface and lumen and aid in detection of smaller sessile polyps (arrows).

 


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  		Figure 4b. Detection of colon polyps in the 1950s was accomplished by means of single-contrast barium enema studies. Fifty years later, imaging for detection of polyps has evolved to include CT colonography and, perhaps, MR colonography. (a) Single-contrast barium enema study obtained in 1959 demonstrates a polyp (arrow) with a long stalk. (b) CT colonographic image obtained in a different patient in 1999 illustrates the ability of this technique to characterize the colonic surface and lumen and aid in detection of smaller sessile polyps (arrows).

 
Although it is beyond the scope of this overview to document the changes that have occurred in the assessment of the abdominal vasculature, it is important to recognize that in 1950, simple aortography was in its infancy. Now, in the year 2000, the performance of diagnostic aortography with catheter techniques has greatly diminished, having gone from the only major study available in the 1960s and 1970s to a seldom-used study today. The development of multidetector-array helical CT with three-dimensional display of vessels accomplished with nonangiographic techniques and the concomitant development of MR angiography with similar types of image displays has provided information about the anatomy and pathology of the vasculature. These noninvasive methods can be used for rapid acquisition and display in ways that conventional arteriography cannot be used (Fig 5). The noninvasive assessment of blood flow in the portal vein, superior mesenteric artery, and superior mesenteric vein can be performed both with contrast-enhanced Doppler US and with MR imaging (62,63). This ability to measure visceral blood flow will permit assessment both of acute and of chronic intestinal ischemia and will expand the role of imaging modalities beyond that of the conventional radiographic small-bowel barium studies and even of CT.



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  		Figure 5a. The radiologic evaluation of intestinal ischemia was, for the most part, confined to abdominal radiography in the 1950s. Fifty years later, the use of helical CT with CT angiography has greatly increased the sensitivity and specificity of imaging for ischemic bowel. (a) Radiograph in a patient (supine position) with abdominal pain and metabolic acidosis who was suspected of having intestinal ischemia demonstrates dilated bowel but no specific features of intestinal ischemia. In this setting, the only way to establish a diagnosis was with laparotomy. At surgery, it was discovered that the patient had extensive advanced infarction. Had helical CT been available, the diagnosis would have been confirmed preoperatively. (b) Transverse CT scan in a different patient demonstrates an embolus (arrow) in the superior mesenteric artery of a patient with atrial fibrillation; the patient was suspected of having intestinal ischemia. (c) Transverse CT scan in the same patient as in b shows extensive air (arrows) in the bowel wall of segments of jejunum, which permitted a diagnosis of intestinal infarction due to superior mesenteric arterial hypoperfusion. (Fig 5b and 5c courtesy of R. Brooke Jeffrey, Jr, MD, Department of Radiology, Stanford University, Calif.)

 


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  		Figure 5b. The radiologic evaluation of intestinal ischemia was, for the most part, confined to abdominal radiography in the 1950s. Fifty years later, the use of helical CT with CT angiography has greatly increased the sensitivity and specificity of imaging for ischemic bowel. (a) Radiograph in a patient (supine position) with abdominal pain and metabolic acidosis who was suspected of having intestinal ischemia demonstrates dilated bowel but no specific features of intestinal ischemia. In this setting, the only way to establish a diagnosis was with laparotomy. At surgery, it was discovered that the patient had extensive advanced infarction. Had helical CT been available, the diagnosis would have been confirmed preoperatively. (b) Transverse CT scan in a different patient demonstrates an embolus (arrow) in the superior mesenteric artery of a patient with atrial fibrillation; the patient was suspected of having intestinal ischemia. (c) Transverse CT scan in the same patient as in b shows extensive air (arrows) in the bowel wall of segments of jejunum, which permitted a diagnosis of intestinal infarction due to superior mesenteric arterial hypoperfusion. (Fig 5b and 5c courtesy of R. Brooke Jeffrey, Jr, MD, Department of Radiology, Stanford University, Calif.)

 


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  		Figure 5c. The radiologic evaluation of intestinal ischemia was, for the most part, confined to abdominal radiography in the 1950s. Fifty years later, the use of helical CT with CT angiography has greatly increased the sensitivity and specificity of imaging for ischemic bowel. (a) Radiograph in a patient (supine position) with abdominal pain and metabolic acidosis who was suspected of having intestinal ischemia demonstrates dilated bowel but no specific features of intestinal ischemia. In this setting, the only way to establish a diagnosis was with laparotomy. At surgery, it was discovered that the patient had extensive advanced infarction. Had helical CT been available, the diagnosis would have been confirmed preoperatively. (b) Transverse CT scan in a different patient demonstrates an embolus (arrow) in the superior mesenteric artery of a patient with atrial fibrillation; the patient was suspected of having intestinal ischemia. (c) Transverse CT scan in the same patient as in b shows extensive air (arrows) in the bowel wall of segments of jejunum, which permitted a diagnosis of intestinal infarction due to superior mesenteric arterial hypoperfusion. (Fig 5b and 5c courtesy of R. Brooke Jeffrey, Jr, MD, Department of Radiology, Stanford University, Calif.)

 
In the 1950s, gastrointestinal radiology was a relatively new area of subspecialty in radiology. Fifty years later, the term "gastrointestinal radiology" itself is being transformed into "abdominal imaging," which reflects the greatly expanded scope of the gastrointestinal radiologist. The Accreditation Council for Graduate Medical Education has recently approved special training programs in abdominal (not gastrointestinal) radiology (64).

Although barium sulfate suspensions are still used to obtain images of the luminal surface of the gastrointestinal tract, as they were 50 years ago, the developments of US, CT, and MR imaging have greatly expanded the scope of gastrointestinal radiology to the point where barium studies are but a small part of the spectrum of activities currently performed by the abdominal imager.

FOOTNOTES

2 Current address: Department of Radiology, Weill Medical College of Cornell University, New York, NY. Back

Abbreviations: ERCP = endoscopic retrograde cholangiopancreatography, MRCP = MR cholangiopancreatography

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