How to learn about a world-class double bass? Give it a CT

Radiology experts at Penn Medicine applied imaging technology to centuries-old instruments to better understand how to care for masterworks built between the 17th and 19th centuries, and provide insights into building new ones.

When you’re an expert in medical CT imaging, two things are bound to happen, says Peter Noël, associate professor of radiology and director of CT Research at the Perelman School of Medicine. One: You develop an insatiable curiosity about the inner workings of all kinds of objects, including those unrelated to your research. And two: Both colleagues and complete strangers will ask for your help in imaging a wide variety of unexpected items.

Over the course of his career, in between managing his own research projects, Noël has imaged diverse objects ranging from animal skulls to tree samples from a German forest, all in the name of furthering scientific knowledge. But none has intrigued him as much as his current extracurricular project: the first known attempt to perform CT imaging of some of the world’s finest string basses.

Duane Rosengard; Peter Noël, Zachary S. Martin; Leening Liu, and Mark Kindig around a double bass in a CT clinic.
The instrument imaging team, from left: Philadelphia Orchestra bassist Duane Rosengard; Peter Noël, director of CT Research at the Perelman School of Medicine; luthier Zachary S. Martin; Leening Liu, a Ph.D. student in Noël’s Laboratory of Advanced Computed Tomography Imaging; and Mark Kindig. (Image: Courtesy of Penn Medicine News)

The goal is to crack the code on what makes a world-class instrument. This knowledge could both increase the ability to better care for masterworks built between the 17th and 19th centuries, as well as providing insights into refining the building of new ones, including possibly shifting from older, scarcer European wood to the use of sustainably harvested U.S. wood.

That’s why Noël and Leening Liu, a Ph.D. student in Noël’s Laboratory of Advanced Computed Tomography Imaging, have found themselves volunteering to run the basses through a Penn CT scanner occasionally.

The team has set its focus on exploring two data points for each bass: internal air volume and the density of its wood. “We believe the air volume has everything to do with why a bass sounds the way it does, because it directly relates to the sonority of a particular instrument and its presence or power,” says luthier Zachary S. Martin. “And wood density very much plays into the instrument’s structure, flexibility, and responsiveness.”

Challenges aside, these collaborators from both creative and quantitative disciplines are delighted to be working together.

Liu operates the scanner and also helps calculate the instruments’ internal volumes. “From the internal corpus volume perspective, it's a straightforward calculation for us,” she says. “It means segmentation, counting the pixels, and then using the pixel volume to calculate how much volume is within the bass itself.”

As for mapping the density of the wood, this issue is more relevant to Liu’s Ph.D. research. Her thesis focuses on using physical density to measure temperatures within the human body, specifically for thermal ablation, a minimally invasive treatment for cancers, including those of the liver and kidney. Carefully directed high temperatures are used to kill both tumor cells and a surrounding safety margin of healthy tissue, and knowing the temperature at which the tissue is burned gives an idea of the treatment’s effectiveness.

“We scientists love to talk about the science part and the musicians feel the same way about music,” Noël says. “We all have a common sense of what we want to achieve, but it’s inspiring and amazing to see what happens when two totally different worlds talk to each other.”

Read more at Penn Medicine News.