JNM: FDG PET/CT can diagnose aortic dissections, guide treatment
Molecular imaging can help physicians identify aortic dissection, often a fatal blood vessel condition, as well as help in guiding treatment, according to two studies published in the May issue of the Journal of Nuclear Medicine.

Aortic dissection occurs when a tear in the wall of the aorta causes blood to flow between the layers of the wall of the aorta and force the layers apart. "Many conventional forms of imaging are not able to clearly differentiate between acute and chronic dissection," said Hans-Henning Eckstein, MD, PhD, professor at the Technical University of Munich in Germany.

In the Munich study, Eckstein and colleagues indicated that 18F-FDG PET/CT might be useful in differentiation of acute from chronic AD in clinically unclear cases.

The Munich researchers analyzed the 18F-FDG uptake in the aortic wall of acute and chronic stable aortic dissection in 18 patients with acute (nine patients), symptomatic progressive (two patients) or known chronic stable (seven patients) type B aortic dissection.

The maximum SUV of the dissection membrane or aortic wall was significantly higher in acute aortic dissection than in chronic stable aortic dissection. SUV varied from 3.03 to 4.64 for the dissection membrane and from 2.22 to 4.60 for the aortic wall, with false-negative and false-positive outliers, wrote Eckstein and colleagues.

In another study, researchers in Japan found that greater metabolic activity in acute aortic dissection was significantly associated with increased risk for rupture and progression.

A total of 28 medically treated acute aortic dissection patients were prospectively studied. Of the 28 patients, eight had an unfavorable outcome due to death from rupture (two patients), surgical repair (four patients) and progression of dissection (two patients). The remaining 20 patients were categorized as having favorable acute aortic dissection.

A stepwise-forward selection procedure demonstrated that the mean SUV at sites of maximum aortic dissection on 50-min FDG PET/CT images significantly and independently predicted an unfavorable outcome for acute aortic dissection, according to Toyoaki Murohara, MD, PhD, professor at Nagoya University Graduate School of Medicine in Japan and colleagues.

The Japanese researchers found that a mean SUV greater than 3.029 had significant predictive power, with sensitivity of 75 percent, specificity of 70 percent, a positive predictive value of 50 percent, a negative predictive value of 87.5 percent and an accuracy of 71.4 percent.

Murohara and colleagues concluded that 18F-FDG PET/CT may be used to improve acute aortic dissection patient management, although more studies are still needed to clarify its role in this clinical scenario.

"Usually, it is difficult to predict poor outcome for patients receiving medical treatment for acute aortic dissection," said Murohara. "This study will give us new information to evaluate the degree of the patients' illness." 

Early diagnosis and treatment are essential for survival of patients with this rare and often fatal disease," said James H.F. Rudd, MD, PhD, researcher and consultant cardiologist at the University of Cambridge in England, who authored an invited perspective article on the role of 18F-FDG PET in aortic dissection, accompanying the JNM studies. "Although further studies are needed, this research suggests that FDG-PET imaging might be used to identify patients who are at a very high risk of complications, allowing them to be fast-tracked to surgery."