On many nights, detailed body scans of patients at the North Shore Medical Center in Salem zip through Internet lines to a suburban Minneapolis office. From there, they might be rerouted to Texas or California, or to France, China, or India, where doctors study the images for signs of disease.
More than two dozen other medical institutions in Massachusetts send their CAT, MRI, and X-ray scans to doctors in other states or foreign countries who often render crucial medical judgments.
To many local hospitals, these so-called ''nighthawk" radiology services are godsends, a global solution to a local problem: a rapidly increasing demand for patient scans, but a shortage of trained radiologists to analyze them. Doctors in other time zones analyze the scans while radiologists here sleep. Often, emergency room doctors on the night shift treat patients based on these far-off diagnoses. Some local radiologists said the volume of work would overwhelm their practices if nighthawk services were not available.
''The bottom line is, did we manage to survive? Yes, we did, using the nighthawk service," said Dr. M. Christian Semine, radiology chairman at North Shore Medical Center, which contracts with one of the nation's largest nighthawk firms, Virtual Radiology Consultants of Minnetonka, Minn.
The practice concerns some doctors and lawmakers, who fear that sending radiology work offshore can diminish care, potentially lead to privacy violations, and may one day cut into the work or salaries of US doctors. US Senator Hillary Rodham Clinton, Democrat of New York, and Representative Edward J. Markey, a Massachusetts Democrat, filed legislation last year that would require patient consent before private health data could be transferred abroad.
''When somebody is half a world away, how can you be sure that the individuals are who they say they are? How do you constantly inspect and ensure they're doing what they should be doing?" said Dr. Arl Van Moore Jr., a radiologist based in Charlotte, N.C., who led a recent task force on the issue for the American College of Radiology that urged hospitals to check the credentials and quality of work provided by nighthawk radiologists.
Other countries do not provide oversight of radiologists who service US clients. Nighthawk firms say the radiologists they employ are US-trained, many of them immigrants who return to their countries to work; others are US citizens willing to live abroad. The firms monitor their work and get them credentialed. And these radiologists often only render preliminary diagnoses that initially guide doctors but are subject to a final review by US-based radiologists.
None of the local radiologists interviewed complained of shoddy service or misdiagnoses. Defenders of the practice also point out that all data sent over Internet lines is encrypted for security. Radiologists use computer hardware and software designed to preserve the crispness of images transmitted through the Internet.
The new phenomenon is being driven by a US shortage of radiologists, a trend even more acute in Massachusetts, local radiologists say. Last month, the Massachusetts Medical Society reported that six medical specialties were facing severe doctor shortages: neurosurgery, anesthesiology, gastroenterology, cardiology, orthopedics, and radiology.
But unlike those other disciplines, radiologists do not need to see patients, which makes that specialty uniquely suited for outsourcing. And with the advent of Internet lines able to quickly move huge amounts of data, several enterprising doctors in Minnesota a few years ago saw an opportunity, and a new field was born.
With improvements in technology, scanning and imaging have become integral to medicine. More scan types are available than ever -- CT, MRI, ultrasound, X-ray, nuclear medicine studies, and even plain film -- and doctors are increasingly dependent on these tools to make diagnoses. But the number of radiologists trained in US medical schools has not kept pace.
''Radiologists were getting woken up eight or 10 times a night. They were not getting any productive sleep," said Dr. Sean Casey, CEO and founder of Virtual Radiologic Consultants.
Casey observed this problem from the University of Minnesota's medical center, where he once worked. He looked into sending some of the overburdened radiology department's work offshore.
''Due to political reasons, the chairman of radiology did not think that was the solution," said Casey. ''As a state university, it might have raised eyebrows to have a lease on a property in the south of France."
So, Casey and other colleagues split off from the university to form VRC, which then helped alleviate the university's radiology overload and rapidly expanded. The privately held firm now contracts for work in 45 states.
The majority of his 50-radiologist staff work in the United States, with 10 percent abroad in Germany, France, Australia, Brazil, and China.
''These entrepreneurs have seen an opening . . . it's a windfall for these companies," said Dr. Giles Boland, vice chairman of Mass. General's radiology department, which does not use nighthawk services.
According to a survey presented at a conference last year by Massachusetts General Hospital radiologist-in-chief Dr. James Thrall, up to 30 percent of US radiology groups and departments use nighthawk services. Of this use, 10 to 15 percent of cases involved overseas doctors, with the rest handled by US remote facilities or on-contract radiologists working from home.
The field was virtually nonexistent five years ago, but is now growing rapidly, though no reliable figures tracking the spurt exist.
''They are making huge inroads. Maybe 15 years down the line, you may find that all radiologists work for these companies," said Dr. Kenneth Peelle, president-elect of the Massachusetts Medical Society and a radiologist at Saints Memorial Medical Center, which does not use nighthawk services, instead requiring staff radiologists to take night shifts.
Casey, who would not disclose Virtual Radiology Consultants' revenues or profits, said his staff analyzes about 555,000 scans annually. The company performs nighthawk work for about 30 Massachusetts hospitals and institutions. Other companies, who also use overseas radiologists, also provide services in the Commonwealth.
Casey said his firm closely monitors its radiologists electronically and through regular phone conversations.
Local radiologists said they expect the use of nighthawk services will grow rapidly in Massachusetts because the shortage of radiologists appears to be particularly severe here, due to high housing costs and low reimbursement rates from insurance companies.
Though most radiologists appear to accept the growing use of nighthawk firms as inevitable, many have concerns, which are usually kept quiet. Three years ago, Mass. General announced it would form a partnership with a nonprofit in India to allow Indian doctors to handle some of the hospital's radiology work. Radiologists' Internet bulletin boards overflowed with rancor, and Dr. Sanjay Saini, who helped devise the plan, received anonymous hate mail.
''There was a group of vocal radiologists -- I don't know who they are -- who criticized MGH," said Saini, now radiology chairman at Emory University School of Medicine.
The Mass. General program never got off the ground. But many hospitals in the state have since taken to sending some radiology work out-of-state or offshore.
''It's a prerequisite these days," said North Shore Medical's Semine, explaining that pushing his short-staffed team harder could actually be dangerous. ''If I had them work any harder, they're just going to start making mistakes with patients."