Irene Githinji, a radiologist in Nairobi, Kenya, didn’t know if the 5-year-old boy had a deadly lesion in his brain. She needed a CT scan to be sure, but her hospital didn’t have one. Kenya’s private facilities have them for $60 to $200, but Mbagathi Hospital, where Githinji treats families, sits at the edge of the Kibera slum, the largest in Africa. “I don't know what happened to the patient after that,” she says, “but I doubt that they ever did the CT scan.”

Even when Githinji’s patients can afford a private facility, the time it takes to get them there can be fatal. “We once lost a young man with head injury, because he had to be taken out for a CT scan,” Irene remembers. The scan showed bleeding around the brain, “but before he could be taken into surgery, he died.”

The World Health Organization estimates that two-thirds of the planet does not have access to basic radiology services: simple x-rays, which can show a cracked bone or lung infection, and ultrasounds, which use sound waves to picture a growing fetus, track blood flow, or guide a biopsy. In a country of 43 million, Kenya only has 200 radiologists; Massachusetts General, in Boston, has 126. Elsewhere, the deprivation is even more severe. Liberia currently has two radiologists. There are more radiologists working in the four teaching hospitals on Longwood Avenue in Boston, Massachusetts, than there are in West Africa.

The global radiology gap is far less discussed than infectious-disease outbreaks and natural disasters, but its dangers to public health are every bit as urgent. “It affects the entire global health care system,” explains Dan Mollura, a radiologist and the CEO of RAD-AID International, an organization that works to improve access to radiology for the world’s poorest people. “Without radiology, most health-care systems have serious gaps and can't provide any care.”

Without ultrasounds, doctors can’t monitor pregnancies. Without chest x-rays, they can’t tell if tuberculosis treatment is working. And without a CT scanner, they can’t catch internal bleeding from a motorcycle accident or cancer at its earliest stages. “Every part of medicine in which the patient has a problem and the answer isn't obvious on physical exam or labs benefits from imaging—particularly trauma,” says Jeffrey Mendel, the senior health and policy advisor for radiology at Partners in Health.

Though CT scanners are available in more than 96 percent of U.S. emergency departments, people in rural Nepal often spend a month’s income and travel more than two days find a facility with an x-ray or ultrasound. But the high price doesn’t guarantee that the imaging is reliable. Nearly 50 percent of x-rays and more than 40 percent of ultrasounds in resource-deprived countries aren’t fully functional, often because they are donated at the end of their lives and getting replacement parts isn’t possible.

“We received an ultrasound donated to our organization along with a lot of extremely valuable stuff. When you turned it on, it was an MS DOS prompt and it said Copyright 1992. I hadn't seen an ultrasound like that in 15 years,” says Ryan Schwarz, a physician and the COO of Possible, an organization that brought working x-rays and ultrasounds to a million people in rural Nepal. The machine wasn’t totally useless; a technician, who traveled a day-and-a-half to reach them, told them one of its probes still functioned. “It’s currently sitting in one of the procedure rooms for a very limited scope of tests and, for those tests it can be very effective, but it’s literally two things,” Schwarz says.

Even when the machines work, there may not be an electrical system to keep them working. Modern hospitals run on three-phase electric power, which guarantees an uninterrupted supply of current. “Getting three-phase to rural Nepal is a tremendous task,” Schwarz says. “With unreliable current, you run into shocks. This is a problem every day in developing countries.”

Closing the radiology gap, then, also means overcoming many non-medical challenges: a lack of electricity, roads, or an information system to store the images. To know what problems exist in an area before launching a program, RAD-AID International developed Radiology Readiness Assessments, which are lengthy downloadable surveys that help organizations measure unmet needs.

A common limitation is a lack of staff. After the 2010 earthquake in Haiti, Mendel and Partners in Health stocked the University Hospital in Mirebalais (UHM) with a CT scanner—the first in a public hospital in Haiti and the first to cost their patients nothing. But the hospital still doesn’t have enough money to hire a radiologist to run the machine, Mendel says.

One solution is telemedicine. UHM uses a picture-archiving and communication system that sends CT scans to a server in Boston, which stores the images and creates an electronic medical record for volunteer radiologists in the U.S. and Canada to read. The volunteers log on twice a week to look over scans, which each take about ten minutes. In 2014, 40 volunteers read approximately 4,000 CT scans.

But telemedicine has limits, especially in an emergency. “Bus accidents happen every day in Nepal,” Schwarz explains. “You have literally 25 patients all at once, who are all bleeding. That’s challenging enough. You’re certainly not waiting for someone in a different country or time zone to tell you what an x-ray shows.”

People like Mendel have a longer-term solution in mind, too, which involves training local staff. “The ultimate goal is that you improve the medical infrastructure in a country to a point where that infrastructure becomes the basis for the country’s health care, not that it needs volunteers to keep it going on a day-to-day basis,” Mendel says.

The Massachusetts General Hospital’s Imaging Global Health Program, for example, invites radiologists from resource-deprived countries to train for three months at the state-of-the-art facility. After Irene Githinji completed her radiology exams as a resident physician, she was accepted into the program. She learned not only about reading images, but also about medical record keeping.

The experience also drove home the sadness and frustration that she sometimes feels as a doctor based in a hospital that doesn’t have the same resources. “Sometimes, you know what ought to be done for a patient, but cannot, because facilities are lacking,” Githinji says. “No one should be let to suffer or die, just because they are poor.”