The island of Tenerife in the Canary Islands is something of a paradise: Its warm, sunny weather and plentiful beaches make it a destination for European vacationers. Three-quarters of the Canary Islands’ economy is based on tourism, according to local government figures, and nearly 5 million tourists visit Tenerife each year. While the tourists and the money they spend buoy the economy, it doesn’t reach all Tinerfeños. The government of Spain, of which the Canary Islands are an autonomous community, reports that the population at risk of poverty or social exclusion increased in that territory in 2021 to 37.8 percent, the third highest rate in Spain.
Poverty can have some shocking health effects.
Not long ago, a group of specialists from the Canary Islands Health Service uncovered an alarming increase in the number of lower limb amputations performed in its hospitals. “During the period from 2010 to 2015, the loss of lower limbs increased from 364 to 444 annually,” said Manuel Maynar, a doctor with the Hospiten Group, an international hospital network based in Tenerife, and head of its Endolminal/Endovascular Diagnostic and Therapeutic Service. “In total, 2,350 of this kind of surgery were accounted for in just five years.”
The amputations were due to damage to lower limbs caused by diabetes mellitus. The condition is often called diabetic foot. Early detection of the damage is difficult but crucial. When left untreated, the lesions can cause the tissues to whither and die. Doctors in Tenerife wanted a tool to find the damage before it was visible to the eye, so they consulted a somewhat surprising source: the physicists and engineers working at one of the world’s premier telescopes, which is also located on Tenerife.
People with diabetes can begin to lose sensation in their feet and do not notice when they bump into objects or wear ill-fitting shoes and develop bruises or cuts. Over time, round lesions appear, often on the top of the foot near the toe bones or on the soles of the foot, particularly in the heels.
In a healthy person, such wounds would heal over time, but that isn’t the case for people with diabetes, who often have poor blood circulation in their extremities, and the bruises turn into open ulcers. Many times, patients ignore the wounds or expect them to heal on their own. The damaged area can grow to several centimeters in diameter and slowly but effectively kill nearby tissues. It is not a pleasant sight, since necropsies generate pus and discolor the skin. In extremely severe cases, these complications often render the foot completely useless, to the point of having to resort to amputation.
Maximo Selva, a clinical specialist at the University Hospital of Santa Cruz de Tenerife, Canary Islands, explained that these ulcers are an important cause of morbidity in patients with diabetes. On occasion, they can even lead to death.
“The lesions cause disabling situations, as a consequence of the surgical techniques used to combat them,” Selva said. “Often the solution is amputation. Even so, the diabetic foot is the chronic complication associated with diabetes mellitus that is easiest and simplest to prevent.”
The lack of sensation in the feet and toes complicates the early detection of these wounds. When the lesions are not caused by impacts severe enough for the patient to notice, the damage may spread for some time under the undisturbed skin. An exhaustive physical examination and a detailed interrogation of lifestyle habits are required to achieve an early diagnosis.
The uptick of diabetic foot and subsequent amputations in Tenerife is a bit of a mystery. “Local people consume mostly the varied Mediterranean diet,” Selva said. Though there are not enough studies to confirm a change in diet as the culprit, Selva did note that with the increase in foreign visitors, a number of fast-food restaurants have opened in the Canary Islands, which could be leading to an increase in dietary sugar.
There are many other contributing factors, such as smoking, obesity, or even inadequate footwear. Most of them, if modified early, can be treated and their effects reversed.
However, other elements such as age or the time of development of diabetes are more difficult to modify, as are contributions from unrelated circulatory, kidney, or neurological diseases. Despite techniques to curb the impact of ulcers, physicians still have a major task ahead of them. One of the current goals of science is to prevent the presence of lesions, even before they appear.
Regardless of the cause, the high number of cases is reason enough to require new tools to allow early detection of diabetic foot ulcers, Maynar said. Together with other members of his institution, he set out to find a scientific partner who could contribute technology that could find these wounds before they were visible.
One of the doors he knocked on was the Institute of Astrophysics of the Canary Islands (IAC). The institute operates more than two dozen astronomical and solar telescopes on Tenerife and the Canary island of La Palma, including the 10.4-m Gran Telescopio Canarias, the world's largest single-aperture optical telescope.
The observatory is known for its world-class contributions to astronomy. What could astronomers contribute to a disease of the human body?
In addition to its core field of studies, however, the institute has a medical technology program called TECMED. The objective of this unit is to transfer equipment and tools used in astrophysical research to various branches of health care. When the doctors from the Canary Islands hospitals approached and laid out the challenge, the astronomers realized they had an instrument that could do the job.
Most people think of astronomy in terms of visible light images of stars, but due to the calm, dry air above the peaks on Tenerife and La Palma, the IAS observatory hosts instruments that look at the cosmos in a wide variety of wavelengths. Radio and microwave telescopes can see emissions from cold gas clouds, while a twin telescope MAGIC can see gamma rays produced by pulsars and the entry of high-energy cosmic rays into the atmosphere.
Several of the telescopes feature detectors for infrared light, which astronomers use to study objects cooler than stars like the Sun. In addition to helping them understand dust clouds and observe objects that are moving away from the Earth at great speed, astronomers hope that infrared detectors could one day directly image a planet circling another star, since those planets would be relatively brighter in infrared than they are in visible light.
The damage from diabetic foot is similar in that way. The medical specialists told the astronomers from IAC of the critical role temperature plays in detecting the latent damage.
“When the diabetic foot lesions begin to form, but their effects are not yet visible, there is an increase in local temperature in the affected area," Selva said. What was needed to improve the early diagnosis of diabetic foot was a low-cost thermometer capable of measuring the heat signature in a noninvasive way.
To the astronomers, that sounded a lot like infrared astronomy.
Because the most worrisome potential damage was below the surface, it would require more than a single thermometer to get a robust signal of the location and extent of the illness. One thermometer would be a camera that operated in the visible and near-infrared, while another would be geared for the thermal infrared from 8 μm to 14 μm. Between the two cameras, the system would be able to develop a subdermal model of the foot while measuring temperature gradations of 0.05 degrees.
It took five years to develop the prototype, called PINRELL (Prototype for INfraREd analysis of Lower Limbs), for clinical trials.
“In this version of the prototype, we can obtain multichannel images. In addition, all the sensors of the cameras have been assembled to support the design in the IAC laboratories. Its fabrication has been possible thanks to a 3D printer belonging to the institution,” said Juan Ruiz Alzola, a researcher at IAC and professor of signal processing and communications at the University of Las Palmas de Gran Canaria.
The 3D-printed structure holds the different cameras in alignment and provides robustness to the whole system. They also point out that the relatively simple way in which it is made could facilitate the technological transfer of the tool to developing countries.
However, the key to PINRELL's progress is a software application developed for its implementation. It facilitates the acquisition of samples, the formal recording of images, as well as the analysis and processing of the information.
“Everything captured by the sensors goes through various data analysis techniques. These are applied for the segmentation of areas of interest, which are then used in the development of statistical algorithms,” explained Sara González, another of the engineers involved in the development of the equipment.
The application is currently in a desktop version that runs on both Linux and Windows. “When it came to developing and implementing the software, it was clear to us that it had to be a transferable system that would provide capabilities rather than complications,” González said. The group aims to have the camera system and software simplified enough to be used in nonclinical settings, such as the home or in the field.
A Powerful Tool
Currently, the PINRELL group is working on a database with the images collected. The idea is to put together a catalogue of images during the clinical trials that can track different anomalous surface temperature patterns—imperceptible to the human eye—of the diabetic foot ulcers.
“We are equipped with the information obtained on a preliminary basis. When the clinical trial phases begin, the volume of content will increase considerably and we want to be prepared to avoid delays,” Alzola said.
These tests will be carried out in hospital facilities sponsored by the Hospiten Group. The researchers will also train technicians who will use the system once it is approved for hospital use. After the clinical studies, the IAC, the Hospiten Group, and the Canary Islands Health Service will develop plans for the mass production of the equipment and its propagation on the islands.
The researchers of the IAC’s TECMED program take the responsibility of manufacturing and designing this prototype of medical equipment seriously. They know that patients’ quality of life is at stake.
“PINRELL will be a very powerful tool,” González said. “Early diagnosis of this kind of lesion could contribute to reducing the number of amputations, which is the main objective.”
Given the potential, the doctors working on the project are excited by its prospects. “Making it possible for every diabetic to have a technological tool like this, readily available, or even in their homes, would help to reduce the number of amputations considerably,” Selva said.
The team is hopeful that PINRELL could also be useful in detecting other diseases, such as sinusitis or pressure ulcers in bedridden people. Even though the camera system has its roots in studying the heavens, it could have its biggest impact improving the lives of people living on the earthly paradise of Tenerife.