The Pentagon is buying a mobile cardiac care unit and separate MRI trailer for the 167 detainees at Guantánamo, a $2.6 million investment for an aging population of captives who can’t be treated on U.S. soil.

The Army put the project out to bid this summer, seeking state-of-the-art equipment to be shipped by barge to the base and set up. A military surgical team would be brought to the base to use the cardiac care unit, as needed.

The investment is part of a Pentagon program offering the detainees healthcare that’s comparable to what U.S. troops receive. The Bush administration made the commitment to comparable care before Congress banned detainees from U.S. soil for any reason — trials or even critical medical care.

“We’ve got detainees with prosthetics, we’ve got detainees who will have age-related things. Some who wish treatment, some who wish to refuse treatment and some who are in between,” said Navy Capt. Robert Durand, the prison camps spokesman.

But with no end in sight to the detention center, Durand said, the military is looking at “the broader questions raised by an aging population: How would we do dialysis if we needed to? How would we do other kinds of medical procedures, and is there a capability we have to build here?”

Prison doctors won’t say how many of the 166 prisoners age 26 to 65 would benefit from the cardiac catheterization lab.

After years of repatriating some sick and elderly captives, leaked prison records show that eight of the remaining detainees are in their 50s and two prisoners are in their 60s. The eldest, Saifullah Paracha of Pakistan, refused a cardiac catheterization procedure in 2006 after the Navy airlifted a mobile suite, two cardiologists and a 19-member medical team to do it.

The package, awarded Friday, was split between two Defense Department contractors. It includes:

•  The mobile catheterization lab that could carry out angioplasty procedures came in at $998,5000 and was awarded to Cardiac Services Mobile, Inc. of Nashville, Tenn.

•  The MRI (magnetic resonance imaging) machine in a separate trailer costs $1.65 million and was awarded to Siemens Medical Solutions USA of Malvern, Pa.

A contractor could build the pop-up medical suites on U.S. soil inside six months, and get them up and running soon after the Navy gets them to Cuba, said Anita Chambers, president of the Cheyenne, Wyo.-based Odulair. Her firm designs and manufactures mobile medical clinics and surgery units like those the Pentagon proposes to put in Cuba.

Once-scarce MRIs are more abundant now, and driven around the United States for use in rural communities and hospitals that don’t have a patient load to justify having one permanently on site.

In the United States, a suite like the one Guantánamo is getting would typically service thousands of people or a small city, said Dr. Mauricio Cohen, a cardiologist with the University of Miami Health System. It would be used for both diagnostic and therapeutic purposes, to look for and then clear blockages through angioplasty.

In rural America, he said, “many, many small cities in the United States have this type of service — a unit that comes once a week, then a patient comes on the trailer and they cath them.”

Or, more typically, he said, a small-town American with a suspected heart condition would be sent to a larger city hospital that has expertise on the topic.