An art critic once wrote, “If all women resembled those painted by Picasso, the Earth would be depopulated toward the end of the century.” The critic was speaking about Picasso’s “Woman in a Green Hat,” describing the model in the painting as “corpselike,” “greenish” and “formless.”
Anyone not sharing Picasso’s cubist view of the world would likely agree. But Picasso painted what he felt more than what he saw. He painted what could not otherwise be seen.
Commenting on the “Woman in a Green Hat,” Picasso said he painted the crooked nose on purpose “so that people were forced to see a nose. Later … they will recognize that it is not crooked at all.”
Medical imaging has been moving in a similar direction for years. Engineers have been assembling technologies, sometimes from wholly different modalities, to form novel constructions that generate information that cannot otherwise be obtained. Positron emission tomography/computed tomography (PET/CT) is an example.
The fusion of two modalities, PET/CT transcends its components, rendering a combination of anatomical and functional data. The concept of modality fusion took root with this hybrid, blossomed several years later into single-photon emission computed tomography (SPECT)/CT and, most recently, bore fruit as PET/magnetic resonance (MR).
Each hybrid provides information that cannot otherwise be obtained. But, just as being able to paint in cubist style is not reason enough to do so, neither is being able to fuse imaging technologies enough to justify such hybridization. Only if fused technologies provide clinical value are they worth the effort of their creation. And there is the rub.
Clinical value often is recognizable only in hindsight. And even then this value may be realized in ways not initially expected.
In the early 1990s, engineers were mounting image intensifiers the size of curb-side garbage cans on a ring that spun at high speed around patients’ heads. The dynamic images of 3-D brain aneurysms filling with contrast medium were as remarkable as the scans were frightening to watch.
The advent of flat panel detectors later in that decade improved image quality and increased the speed with which this ring could be spun. So encouraging was this leap forward that some pundits believed these once gangly and oversized systems might one day replace CTs. What happened instead was the evolution of multi-detector CTs (MDCT) and C-arm rotational angiography.
Today the most advanced MDCTs can cover the entire brain or heart in a single rotation, much like the image intensifier (II) prototype was envisioned to be able to do. Similarly, the technique of rotational angiography proven by those spinning IIs was modified to work with a single flat panel mounted on a C-arm, systems that are now commonplace in imaging centers around the world …
as are multi-detector CTs.
The footprints of other hybridizations are evident elsewhere. One, involving digital breast tomosynthesis (DBT), developed out of necessity. Seen for decades as the holy grail for evaluating breast cancer, DBT was found to work best with the technology it was meant to replace. The signs of cancer were easier to spot, it was learned, when 3-D and 2-D images were interpreted together. The need for this pairing led one manufacturer to develop an algorithm that synthesizes 2-D images from 3-D data, creating a synergy of 2-D and 3-D mammography in a single unit.
Imaging technologies will continue to be fused in the years ahead, propelling all of medicine forward as it has in the past. Like the early rotational angiography machines of 20 years ago, their unions may look like they’ve been torn from a Rube Goldberg sketchbook. But their clinical impact may be no laughing matter.
It will serve us well to remember that many of today’s most useful imaging systems began in the imagination of someone who saw, as Picasso said, “with different eyes.”
Greg Freiherr has reported on developments in radiology since 1983. He runs the consulting service, The Freiherr Group. Read more of his views on his blog at www.itnonline.com.
October 27, 2021 
