Virtual bronchoscopy shows strength in stent surveillance
Multidetector CT (MDCT) scans are highly accurate in detecting airway stent complications according to a recent study performed at Beth Israel Deaconess Medical Center and Harvard Medical School in Boston and published this month in the American Journal of Roentgenology.

According to the researchers, airway stents are commonly used to treat patients with an airway obstruction from a variety of malignant and benign disorders.

“Bronchoscopy is currently the reference standard for detection and treatment of stent complications, but it is an invasive test,” said Vandana Dialani, MD, lead author of the study. “MDCT is a non-invasive imaging alternative for the detection of airway stent complications.”

The authors conducted a retrospective analysis of 21 patients who underwent MDCT within one week of bronchoscopy and were identified with bronchoscopically proven airway stent complications over an 18-month period. All patients underwent the same CT protocol on an 8-slice CT system (LightSpeed, GE Healthcare). Coronal and sagittal multiplanar volume reformation images, as well as 3D internal and external renderings of the airways, were routinely obtained in all cases, the authors noted.

Virtual bronchoscopic image shows intraluminal perspective of stent. Note external stud (arrow) that is stabilization device to help prevent dislodgement. Image and caption courtesy of the American Roentgen Ray Society.  
“Although airway stenting has become an increasingly popular and effective treatment for central airway obstruction, a rate-limiting factor for the use of stents has been the historically high rate of complications, particularly with long-term use,” the authors wrote. “Because most stent complications are potentially treatable if detected early and because an invasive procedure can potentially be avoided, a non-invasive method, such as MDCT, is needed for stent surveillance.”

MDCT correctly identified 29 (97 percent) of 30 complications in 21 patients, including all cases of intraluminal narrowing, migration, invasion by neoplasm and tracheal perforation; MDCT also identified three of four cases of stent fracture, according to the authors.

“A major impact of our study is that patients with positive MDCT findings of a stent complication can avoid diagnostic flexible bronchoscopy and may go directly to therapeutic rigid bronchoscopy,” the authors wrote.

In addition, they described two other potential benefits to performing virtual bronchoscopy: MDCT findings can be used to plan the bronchoscopic intervention, thus potentially decreasing the time of the procedure; and, second, if the stent needs to be replaced due to fracture, a custom stent can be designed using measurements obtained from MDCT.

Although the results of this study are very promising, the researchers emphasized the need for additional, larger studies to determine whether a negative CT result effectively excludes a stent complication and to better assess the accuracy of MDCT for detecting rare complications.  

“Our results show that MDCT is a promising alternative to bronchoscopy for surveillance of stents for complications and has the potential to assist early detection of complications while they are most amenable to treatment,” said Dialani. “MDCT has the potential to replace bronchoscopy for the routine surveillance of patients with airway stents.”