Advances in Contrast Agent Delivery, Mammography
Contrast agent injection systems
Two new automated injections systems for contrast radiography are now undergoing clinical evaluation. Guerbet (France), manufacturer of the Micropaque line of barium contrast agents, is evaluating the KMP 2000 enteroclysis pump, designed to infuse barium contrast into the small bowel for diagnostic gastrointestinal scans. Current methods of delivering barium to the small intestine require patients to swallow the agents and wait for a period of time until they reach the bowel. The KMP 2000 utilizes tubing that is inserted directly into the bowel to deliver the agents to the target site for immediate use. The pump, which provides exact volume input levels of barium, allows flow rate and other parameters to be adjusted as needed.
According to the company, the system can reduce the time required for the procedure, and increase the physician's control. The pump has received CE Mark approval and is under clinical evaluation at several sites in the United Kingdom. The firm expects to launch the product in the U.K. this month.
Meanwhile, a relatively new competitor, Acist Medical Systems (Eden Prairie, MN, USA), is marketing an automated injection system for delivering cardiovascular contrast agents. The firm's Model CL-100 Angiographic Contrast Injection System provides both a disposable, single-use angiographic kit and an electromechanical pump. Unlike current hand syringe or power injector methods for delivering angiographic contrast, the Acist pump gives physicians complete control over the flow of contrast material, and is able to respond to the optimal rate of injection based on the patient's condition. The device features an automated hand piece that combines the precise control of a handhelp syringe with the advantages of an injector, touch screen controls, and automatic contrast refilling to simplify the procedure and cut personnel requirements.
The company launched the CL-100 last July (it was U.S. Food and Drug Administration [FDA]-approved in December 1997), and is conducting multicenter clinical studies, which it expects will reveal both improved cath lab efficiency and contrast material savings. The firms is also developing a related disposable kit for radiology angiographic labs, slated for introduction in the second quarter of 1999, as well as a system for delivering ultrasound contrast agents.
More than 18 million radiology, 3 million diagnostic and interventional cardiology, and 11 million cardiac ultrasound procedures are performed in the United States each year. As Table 1 shows, the worldwide market for x-ray contrast agents alone now totals about US$2 billion annually. Mallinckrodt (St. Louis, MO, USA) holds about a 40% share of this market in the U.S. and 25% worldwide.
Breast caner detection
Several emerging imaging techniques, such as microwave imaging, scintimammography, and laser mammography show promise for the early detection of breast cancer. As Fig. 1 illustrates, the percentage of American women undergoing regular mammogram screenings for breast cancer has increased significantly in the past eight year, although the numbers still fall short of optimum. According to the American Cancer Society nearly 179,00 new cases of breast cancer are diagnosed in the United States annually, resulting in over 40,000 deaths.
Researchers at Northwestern University (Evanston, IL, USA), the University of Wisconsin (Madison), and start-up Interstitial (Evanston, IL, USA) are developing microwave imaging technology that may represent a significant advance for the detection of breast cancer. The new method holds promise not only for detecting tumors that are invisible to conventional mammogram x-rays, but also for helping discriminate malignant from benign tumors, thus reducing the number of unnecessary biopsies. Using a miniature sensor/antenna that is placed against the skin surface, low-energy, nonionizing microwave pulses are bounced off the breast without the need for breast compression. The sensor analyzes the pulses, detecting differences in water content between a malignant tumor and normal breast tissue, and a computer processor uses the resulting data to produce a three-dimensional digital image of the breast.
Scintimammography, in contrast, is a nuclear imaging technique that requires the patient to swallow or be injected with a glucose-based radioactive material. Cancerous tissue absorbs the radioactive material at a faster rate than normal tissue, and can be detected with a gamma camera as areas of high radioactive concentration. The technique is particularly well suited to women who are not easy to image with mammography, such as those with naturally dense breasts,or those who have had surgery (including breast implants).
Researchers at the Jefferson National Accelerator Facility (Newport News, VA, USA) have developed an advanced scintimammography camera designed to provide superior breast images. The new camera, which is licensed to Dilon Technologies (also of Newport News), is about a quarter of the size of current models, making it easier to take pictures of the breast from different angles. It should also provide better picture resolution than cameras currently in use, the researchers say. The camera is undergoing clinical testing at Johns Hopkins University (Baltimore, MD, USA).
Meanwhile, ultrasound continues to expand its role as an adjunctive imaging modality for the diagnosis and biopsy of suspicious breast lesions, specifically for women with dense breast tissue. At last year's meeting of the American Institute of Ultrasound in Medicine (AIUM), researchers for Leiden University (The Netherlands) reported the results of a two-year, 4,000-patient study designed to examine the benefits of ultrasound in diagnosing breast cancer. Patients in the study received an ultrasound examination if mammography showed an undetermined mass, or if a patient presented with a palpable lump that could not be detected effectively with a mammogram.
While mammography alone correctly diagnosed 83% of the study participants' cancerous lumps, the number of correctly diagnosed cases rose to 94% with the addition of ultrasound imaging. Of the additional diagnoses, half were made in patients with a palpable lump not visible on the mammogram, while the other half occurred in patients who, based on their mammogram, were thought to have benign lesions.
Advances in ultrasound technology promise to provide even better image interpretation capabilities in the near future, according to Thomas Nelson and colleagues from the University of California, San Diego, who also presented at AIUM. Working with Siemens Ultrasound (New York, NY, USA), Nelson investigated the use of 3-D and gray-scale harmonic imaging techniques (using microbubble contrast agents), and found that these techniques greatly enhanced the comprehension of patient anatomy, providing high contrast and spatial resolution without the artifacts associated with Doppler imaging.