Lung Nodule Management

An Interventional Pulmonology Perspective

Udit Chaddha, MBBS; Jonathan S. Kurman, MD, MBA; Amit Mahajan, MD, FCCP; D. Kyle Hogarth, MD

Disclosures

Semin Respir Crit Care Med. 2018;39(6):661-666. 

In This Article

Cone Beam CT

Unlike a traditional "fan beam" CT scanner, CBCT involves a compact system mounted to a C-arm that can capture volumetric data with a single rotation of the scanner and detector, while the patient remains stationary. Volumetric data can improve the navigation and confirmation components of peripheral bronchoscopy. Using a commercially available software, peripheral pulmonary lesions can be segmented and then overlaid on traditional fluoroscopy images, a technique known as augmented fluoroscopy.[45] A pathway to the lesion can also be delineated in this manner, thereby enhancing peripheral navigation. In order to utilize augmented fluoroscopy, a CBCT scan must be performed at the beginning of the procedure, prior to navigation. Navigation is still typically performed using traditional electromagnetic modalities. Once navigation is completed, the biopsy instrument is extended to the lesion, and a second CBCT scan may be performed to confirm the position within the lesion. CBCT can identify the exact position of an instrument relative to a small lesion. This is important for diagnostic purposes but even more critical for future therapeutic applications, where accurate positioning is paramount.

Pritchett first described the combined use of CBCT and EMN in 2014.[46] A recent retrospective study of 75 consecutive patients reported an overall diagnostic yield of 83.7%.[47] The median lesion size was 16 mm with a range of 7 to 55 mm. No correlation was detected between diagnostic yield and lesion size, location, and visibility under standard fluoroscopy or the presence of a bronchus sign. Other studies using conventional bronchoscopy and CBCT reported lower diagnostic yields. A prospective study of 33 patients and a retrospective study of 59 patients described diagnostic yields of 70 and 71.2%, respectively.[48,49] The prospective study achieved an overall navigational yield of 91%, demonstrating the large gap between navigation and sample acquisition.[48] The mean nodule diameter in this study was 15 ± 3 mm.

The most recent study by Pritchett et al had a pneumothorax rate of 4%.[47] Radiation exposure was evaluated in a subset of nine patients. The mean effective dose was 2 mSV per CBCT scan. An average of 1.5 scans was performed per patient. A phantom study by Hohenforst-Schmidt et al found a measured body radiation level between 0.98 and 1.15 mSV and lung specific radiation doses of 0.38 to 0.42 mSV.[48] These levels are about one-third less than the dose used in the National Lung Screen Trial and up to 42% less than during conventional CT guidance.[4,50] Overall, CBCT is a safe modality and can potentially increase the diagnostic yield of bronchoscopies for peripheral lung lesions. Future research with high-quality data is needed to further delineate its optimal role in advanced bronchoscopy. One of the biggest hurdles to widespread adaptation of CBCT is likely to be its cost.

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