The key tool of Dr. Andrew Callen’s trade is a million-dollar CT scanner which, with help from special dye injected into the narrow, fluid-filled compartment through which a patient’s spinal cord threads, enables an imaging technique called dynamic CT myelography.

The technique has proven vital in localizing CSF leaks which cause intracranial hypotension, a debilitating condition whose causes often remained mysterious until a decade ago. Intracranial hypotension happens when cerebrospinal fluid leaks from the spine, lowering the pressure in the central nervous system like a deflating tire. That can cause crushing headaches and other symptoms. While rare, this happens to more than 11,000 people a year across the United States and more than 200 a year in Colorado – and those are probably underestimates.

Callen, a University of Colorado School of Medicine neuroradiologist, leads the CSF Leak Clinic at UCHealth University of Colorado Hospital on the Anschutz Medical Campus. He’s a leader in advancing dynamic CT myelography (dCTM) to better diagnose and treat intracranial hypotension.

But this high-tech diagnosis has often hinged on overcoming a low-tech issue – one that, thanks to Callen’s expertise and persistence as well as a big assist from Denver engineering firm K1C Consulting, has been addressed, in part, by a couple of actual hinges.

An unexpected challenge in diagnosing CSF leaks

The challenge has been that small cerebrospinal fluid leaks – in particular, CSF-venous fistulas, which were first described in 2014 – are hard to spot even with advanced imaging tools such as dCTM. To up the odds, neuroradiologists perform rapid imaging with the patient’s head lower than their waist. That allows gravity to move the injected X-ray dye toward the head while densely layering along the spinal canal, allowing visualization of otherwise undetectable problems.

But how to safely and accurately raise the patient’s waist above their head in the narrow tube of a CT scanner without distorting the CT images with artifacts from the added material? The answer, too often, has been… pillows.

“People resorted to using pillows and wedges,” Callen said. “Basically, building a pillow fort on the CT table.”

The “pillow fort” Callen’s team often settled on consisted of a HoverMatt typically used to transfer patients from gurney to scanner bed. They folded it under the patient’s hips and inflated it. This method did raise the hips but with the cost of introducing inconsistency to an otherwise highly precise scan. Other times, they would use a foam wedge. In either scenario, a tall patient’s spine might sag more than a short patient’s, resulting in insufficient movement of contrast dye and boosting the odds of a missed diagnosis.

“It was just insane to me that a quaternary referral center of expertise would resort to such a rudimentary and crude way of performing these procedures,” Callen said.

No one, anywhere, had a better solution. So, he decided to invent one himself. But he would need a bit of help with the engineering.

Engineering for the inside of a CT scanner isn’t easy

Dr. Jody Tanabe, the CU School of Medicine’s neuroradiology chief, suggested reaching out to K1C Consulting, which had worked with CU faculty on device development in the past. Callen reached out to them in November 2022. Funds from the Department of Radiology and, later, a grant from the Considine Family Foundation would cover the cost.

K1C engineers Richard Wojcik and Michael Bojanowski observed a dynamic myelography procedure, gathered impressions from the CT technologists who work hands-on with patients, and brainstormed with Callen. Bojanowski says they wanted something very stable but simple – and also made with radiotranslucent materials that wouldn’t affect CT image quality.

“I thought he had a very interesting problem that we wanted to solve simply and elegantly,” Bojanowski said.

They settled upon a sort of narrow cot with a pivot at the midpoint that could be easily placed on the CT scanner bed. Metal would corrupt scans, so rather than a hydraulic piston or similar to push the center up directly, they went with a manual winch that reeled in a nylon cable attached at either end, tenting the cot smoothly on Rollerblade-style wheels as it did. The central hinges would be of a robust plastic called Ultem and the frame of extruded fiberglass. The base upon which the patient lies would be off-the-shelf plastic softened with foam cushioning and covered with heavy-duty canvas.

A better positioning device for dynamic CT myelography improves CSF leak diagnosis

Callen started using the device in August 2023, and in October, he, Wojcik and Bojanowski published a technical report of their “novel patient-positioning device for dynamic CT myelography” in the American Journal of Neuroradiology. It was something of a sensation.

“Once we published that, several other big-name centers reached out and asked if they could purchase one, as they have encountered similar obstacles doing this procedure,” Callen said.

The answer, for the time being, was “no” – because only one existed. Meanwhile, Callen has enjoyed the consistency and repeatability it confers with every patient he has scanned – more than 100 and counting. But that may change soon.

Callen has landed a CU Innovations Startup Toolbox grant, which he’s using on regulatory consulting (to navigate the U.S. Food and Drug Administration medical-device approval process), marketing strategy, and, with help from K1C Consulting, contract-manufacturing and commercialization, “to assemble not just one, but hundreds of these,” as Bojanowski put it.

Still, Callen says, “I’m not necessarily an entrepreneur – my goal in creating this device was not necessarily to form a company.”

Rather, his main interest is doing right by his patients and those at a growing number of national centers capable of finding and treating CSF leaks, he says. (Treatment typically involves injecting the patient’s blood or fibrin glue to repair small leaks, a minimally invasive surgery by CU School of Medicine neurosurgeon Dr. Peter Lennarson to repair larger ones, or clotting off veins that cause CSF-venous fistulas using endovascular or percutaneous procedures that access the vein internally or through the skin, respectively).

CSF leaks are an area in which a neuroradiologist “can make a huge difference,” Callen says. Rather than just assessing scans and reporting findings, he’s involved throughout the care of a patient with intracranial hypotension: diagnosing, imaging, repairing, working closely with surgery when a more significant repair is needed, and managing medications after leaks are closed.

And, also, leading the invention of a new medical device. “Low-tech” as it may appear (and appearances can deceive), it’s already helping patients, with many more to benefit going forward.