麻豆传媒

CHICAGO -- As if confronting a Tyrannosaurus rex wasn't bad enough, imagine if that dinosaur was also suffering from a toothache: Noninvasive imaging of the left dentary of a T. rex's jaw showed thickening and a mass that extended to the root of one of its teeth, suggesting a bone infection, a researcher reported.

Dual-energy CT explained a curious bump on the fossilized jaw of "," one of the most complete T. rex skeletons unearthed, according to Charlie Hamm, MD, of Charité University Hospital in Berlin. Tristan's fossilized skeleton, which was discovered in Carter County, Montana, dates back approximately 68 million years to the period. The skeleton was sold to a private party who named it after his son, and loaned it to the Museum für Naturkunde Berlin.

"The left dentary showed two notable findings on visual inspection and CT imaging: a diffuse thickening of nearly the entire left dentary with a homogenous distribution of calcium and a focal exophytic mass on the ventral surface of the dentary with a significant accumulation of fluorine (P<0.0001)," according to Hamm and colleagues in a study presented at the Radiological Society of North America annual meeting.

"Furthermore, the focal exophytic mass showed diminutive diffuse lucencies extending from the surface to the tooth root of the 5th replacement tooth and demonstrated a tapering shape with a fistular-like center, which also demonstrated a significant fluorine accumulation respectively (P<0.0001). The perseverance of anatomical structures within the mass suggests the diagnosis of tumefactive osteomyelitis," they noted.

Hamm explained that previous fossil studies have mostly relied on invasive sampling and analysis. Dual-energy CT (DECT) deploys x-rays at two different energy levels, providing information about tissue composition and disease processes not possible with single-energy CT.

"We hypothesized that DECT could potentially allow for quantitative noninvasive element-based material decomposition and thereby help paleontologists in characterizing unique fossils," Hamm said. DECT allowed the researchers to overcome the difficulties of scanning a large portion of Tristan Otto's lower jaw, particularly because of its high bone density.

The scanner's tube current and voltage had to be adjusted in order to minimize artifacts and boost image quality, Hamm stated. His group also explained that "Two custom and validated DECT algorithms were applied for the detection of calcium and fluorine, based on a three-material decomposition approach."

They concluded that "the noninvasive density- and element-based material decomposition of fossilized bone revealed that fluorine could serve as an imaging biomarker for areas with decreased bone density, helping paleontologists to investigate fossils without the need to harm their integrity."

Hamm acknowledged that this was a proof-of-concept study, but that it demonstrated that DECT could provide structural and molecular information on unique fossil objects, while avoiding sample defragmentation or destruction, and potentially address an unmet need in paleontology.

"DECT is also promising for other paleontological applications, such as age determination and differentiation of actual bone from replicas," added Oliver Hampe, PhD, a paleontologist with the Museum für Naturkunde Berlin. "The experimental design, including the use of a clinical CT scanner, will allow for broad applications."

Hamm and colleagues previously performed a at the Field Museum in Chicago. "With every project, our collaborative network grew and evolved into a truly multidisciplinary group of experts in geology, mineralogy, paleontology, and radiology, emphasizing the potential and relevance of the results to different scientific fields," Hamm said.

Back in 2014, other German radiologists used CT data to to confirm the identity of an unprepared fossil, and then mined that dataset to separate the fossilized bone from surrounding sediment to produce a . More recently, a U.S.-based radiologist used CT scanning to diagnose in a 75 million-year-old fibula fossil.

Max Wintermark, MD, of Stanford University in California, called the current study "fascinating."

"We also use dual-energy CT in patients for multiple purposes...to improve the detection of intracranial bleeds, to determine the age of vertebral fractures, and to define the composition of kidney stones," Wintermark, who was not involved in the study, told 麻豆传媒. "The T. rex study findings highlight the need to study additional applications in patients, including the diagnosis of osteomyelitis."

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