We evaluated the usefulness of endobronchial ultrasonography with a guide sheath (EBUS-GS) for diagnosing of peripheral pulmonary lesions (PPLs).1–4 The diagnostic rate of transbronchial biopsy (TBB) using EBUS-GS for PPLs ranged from 58% to 77%.1–8 This technique is promising for small peripheral lesions, especially in combination with a virtual bronchoscopic navigation system.3 However, the present EBUS-GS method is still not a real-time procedure for target visualization. We usually perform TBB using EBUS-GS and x-ray fluoroscopy as follows: the EBUS probe with a guide sheath is inserted through a bronchoscopic working channel into the bronchi leading to the PPLs. After localizing the PPL on the EBUS image and x-ray fluoroscopy, the EBUS probe is removed from the guide sheath and the guide sheath is left in the PPL. Biopsy forceps and bronchial brushes are introduced through the guide sheath. Specimens are obtained under x-ray fluoroscopic guidance for histologic and cytologic examination.2–4 For PPLs, the present EBUS-GS method has a weakness, in that the edge position of a guide sheath sometimes migrates either because of the patient's respiratory movement or during insertion of the biopsy forceps or the brush. For mediastinal lesions, the endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) technique using a convex probe (BF-UC260F-OL8; Olympus, Tokyo, Japan) can show real-time EBUS images,9,10 so that the diagnostic rate of TBNA becomes significantly higher than that of conventional TBNA, which is performed in a blind manner.11,12 We thus anticipated that real-time EBUS for PPLs could overcome the migration problem and result in a diagnostic rate higher than that of the conventional EBUS-GS method. It is very important to accumulate information on real-time EBUS for PPLs. If this technique is available, TBB without x-ray fluoroscopy might be possible for PPLs. However, few data on real-time EBUS images of biopsy forceps or brushes in PPLs are available. In contrast, using a biopsy forceps near an EBUS probe has the risk of damaging the EBUS probe with the biopsy forceps. In this study, we attempted a pilot study on performing TBB for relatively large PPLs (mean diameter, >30 mm) under real-time EBUS guidance using a flexible bronchoscope (FB) with 2 working channels.
PATIENTS AND METHODS
Between January 2007 and May 2007, 6 patients (3 men) with PPLs [mean diameter >30 mm on computed tomography (CT) image] underwent TBB under real-time EBUS and x-ray fluoroscopic guidance. All patients were given detailed descriptions of the procedure before the examination and were informed that this method was a new approach. This study was approved by the institutional review board. After written informed consent was obtained, patients underwent the procedures as described below.
TBB Under Real-time EBUS Guidance
A FB with 2 working channels (XBF-2T-40Y; Olympus) was used for all patients. A 20-MHz mechanical radial-type probe (UM-S20-17R; Olympus) with an external diameter of 1.4 mm and a guide sheath with an external diameter of 1.9 mm (B01-836-12; Olympus) were used. The probe was connected to an endoscopic ultrasound system (EU-M30S; Olympus). TBB under real-time EBUS guidance was performed as shown in Figure 1. After inserting the bronchoscope under local anesthesia, as distal as possible into the target bronchus under direct vision (Fig. 1A), an EBUS probe was inserted into the guide sheath and the guide sheath-covered probe was then inserted through the working channel of 2.0 mm in diameter into the bronchi leading to the area in which the lesion was located (Fig. 1B). Both EBUS imaging and x-ray fluoroscopy were used to confirm that the probe and guide sheath had reached the lesion. If an EBUS image of the lesion could not be obtained, the probe was removed from the guide sheath. Then, a double-hinged curette was inserted into the guide sheath and the appropriate bronchus was selected by manipulating the curette under fluoroscopic guidance. Once the bronchus was determined, the curette was removed from the guide sheath and once again the probe was inserted into the guide sheath to capture the EBUS image of the lesion. After the lesion was localized on the EBUS image and x-ray fluoroscopy, the biopsy forceps along with the guide sheath with an external diameter of 2.7 mm (XB01-836-13; Olympus) was inserted through the other working channel, which was 2.8 mm in diameter, under x-ray fluoroscopy and EBUS guidance (Fig. 1C). A biopsy forceps or brush was introduced through the guide sheath and pathologic and cytologic specimens were obtained under EBUS and x-ray fluoroscopic guidance. If biopsy forceps images could not be obtained on EBUS images, the forceps were removed from the guide sheath and a curette was used for selecting an appropriate bronchus again under x-ray fluoroscopic guidance.
The primary objective of this study was to evaluate the EBUS probe for detecting biopsy forceps or brushes in PPLs.
If we had difficulty in obtaining biopsy forceps or brush images on real-time EBUS in PPLs, we immediately changed to the conventional EBUS-GS method. TBB using conventional EBUS-GS was performed by the procedure described earlier.2–4
On the CT images, the mean±SD diameter of the lesions was 37.4±4.5 mm (range: 32.0 to 45.0 mm). All lesions were detected by EBUS. Biopsy forceps or brush images on real-time EBUS were obtained in 4 of 6 cases. Definitive diagnoses were established for all lesions by TBB, using real-time EBUS in 4 cases and conventional EBUS-GS in 2 cases (Table 1). These 6 lesions included 4 cases of primary lung cancer (3 adenocarcinoma and 1 small cell carcinoma), 1 case of breast cancer metastasis and 1 case of organizing pneumonia.
One lesion for which biopsy forceps images could not be obtained on real-time EBUS was located on right-sided segment 9 (Table 1, case 3). It was not difficult to insert an EBUS probe into the PPL, but we had difficulty in performing biopsy forceps, brush, or curette procedures in proximity to the EBUS probe. The other lesion for which images could not be obtained was located in right-sided segment 5 (Table 1, case 5). In this case, the EBUS probe was inserted near the inferior edge of the lesion; we were unable to insert the forceps or curette into the lesion because the working channel for biopsy forceps was positioned lower than the working channel for the EBUS probe. In these 2 cases, we subsequently performed TBB using the conventional EBUS-GS method and x-ray fluoroscopy. Pathologic diagnoses were obtained by conventional EBUS-GS in cases 3 and 5.
In the 4 other cases, we could obtain forceps or brush images on real-time EBUS. However, when a forceps or brush was stationary, it was very difficult to distinguish the image of forceps from the images of normal pulmonary structures (vessels, bronchi). In case 6, the lesion was in right-sided segment 1 on the CT image (Fig. 2A). The EBUS probe and biopsy forceps with guide sheath were inserted into the lesion (Fig. 2B) and the biopsy forceps image was obtained on real-time EBUS (Fig. 2C). Unfortunately, we could hardly determine the position of the tip of the forceps only from real-time EBUS guidance, because the EBUS image of the edge of the forceps was similar to the image of the body of the forceps. Therefore, detection of the forceps or brush in PPLs on real-time EBUS was not adequate. The average time to the first biopsy was 14.6 minutes and the average total examination time was 26.6 minutes. No complications other than minor bleeding occurred in all cases.
This study was the first trial in which we attempted to examine the practicality of TBB under real-time EBUS guidance for the diagnosis of PPLs. TBB for PPLs under x-ray fluoroscopy is a common technique in Japan, but is not necessarily used throughout the world. TBB without x-ray fluoroscopy has some advantages in that both patient and physician can avoid x-ray exposure and it is relatively inexpensive. EBUS-GS is one of the most promising techniques for TBB without x-ray fluoroscopy for PPLs. Yoshikawa et al13 have recently reported the usefulness of TBB without x-ray fluoroscopy for PPLs, with a diagnostic rate of 61.8%.
There are some technical limitations of this method for diagnosing PPLs as changing the position of the EBUS probe from a position adjacent to the lesion to a position within the lesion is difficult by the conventional EBUS-GS method. Kurimoto et al1 reported that the diagnostic rate using EBUS-GS and x-ray fluoroscopy was significantly higher when the EBUS probe could be placed within the PPL than when the probe could be placed adjacent to the PPL. Shirakawa et al6 also place emphasis on the importance of the position of the probe. In the future, real-time EBUS may reveal the center of a PPL and overcome this problem.
Further advantages of the real-time EBUS method are as follows. First, this method might facilitate TBB for PPL without x-ray fluoroscopy. If a virtual bronchoscopic navigation system can be used, TBB without x-ray fluoroscopy will be possible even for lesions near the pleura.14–17 Second, finding the center of the PPLs and guiding forceps into the lesion might increase the diagnostic rate compared with using conventional EBUS-GS even under x-ray fluoroscopy.
Unfortunately, we have decided to temporarily refrain from using this method until more adequate instruments and systems have been developed to perform TBB under real-time EBUS guidance. This decision is because of some limitations in inserting both the forceps and the EBUS probe in one lesion. When the target lesion is small, the insertion of both the forceps and the probe becomes much more difficult, with increased risk of damage to the EBUS probe. Moreover, the forceps images in EBUS guidance were of low quality.
To improve this technique, new instrumentation is recommended. Although we used an XBF-2T-40Y bronchoscope that had 2 working channels, this bronchoscope was developed for use in real-time EBUS-TBNA12 and it was not possible to insert it into the peripheral area of the lesion. High-quality images of the forceps or brush in PPLs on real-time EBUS were not obtained, mainly because 2 separate catheters had to be inserted into the lesion. That is, we had to avoid damage to the EBUS probe during the use of the forceps. Therefore, we inserted the biopsy forceps into another bronchus apart from the EBUS probe. However, because the direction of the EBUS probe insertion and forceps was not parallel, it was difficult to obtain high-quality images by radial-type EBUS.
In the future, improved instruments that have an EBUS probe and forceps in one body that can be inserted into the peripheral pulmonary area should be developed. Such an instrument may show the center of the lesion as well as the position of the forceps simultaneously. The current radial-type EBUS can show the forceps or brush only as a pinpoint shadow in the short-axis images of EBUS. If the 3-dimensional reconstruction of EBUS becomes available, the long-axis images of EBUS will assist in overcoming this problem.18 Basically, a convex probe will be necessary for long-axis imaging. However, the present convex probe is too big to be inserted into the peripheral airways and needs to be miniaturized. In addition, the surface of the present biopsy forceps is so smooth that recognition of the forceps is difficult on real-time EBUS images. The EBUS-TBNA needles are corrugated, which facilitates their detection by EBUS.9–11 If new biopsy forceps have similar corrugation, it could be recognized more easily on EBUS images.
In summary, our attempt at TBB under real-time EBUS guidance was modestly successful in 4 of 6 cases. We found technical limitations of the real-time EBUS method using FB with 2 working channels. Improvement of instrumentation will be necessary for optimal TBB with real-time EBUS guidance.
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