US-assisted bronchoscopy with use of miniature transducer-containing catheters

Improving diagnostic strategies in bronchoscopy for peripheral pulmonary lesions

INTRODUCTION

In the past two decades, bronchoscopy of peripheral pulmonary lesions (PPLs) has improved its diagnostic yield due to the combination of various instruments and devices. Meanwhile, the application is complex and intertwined.

AREAS COVERED

This review article outlines strategies in diagnostic bronchoscopy for PPLs. We summarize the utility and evidence of key instruments and devices based on the results of clinical trials. Future perspectives of bronchoscopy for PPLs are also discussed.

EXPERT OPINION

The accuracy of reaching PPLs by bronchoscopy has improved significantly with the introduction of combined instruments such as navigation, radial endobronchial ultrasound, digital tomosynthesis, and cone-beam computed tomography. It has been accelerated with the advent of approach tools such as newer ultrathin bronchoscopes and robotic-assisted bronchoscopy. In addition, needle aspiration and cryobiopsy provide further diagnostic opportunities beyond forceps biopsy. Rapid on-site evaluation may also play an important role in decision making during the procedures. As a result, the diagnostic yield of bronchoscopy for PPLs has improved to a level comparable to that of transthoracic needle biopsy. The techniques and technologies developed in the diagnosis will be carried over to the next step in the transbronchial treatment of PPLs in the future.

Endobronchial ultrasonography guidance for transbronchial needle aspiration using a double-channel bronchoscope

STUDY OBJECTIVES

Endobronchial ultrasonography (EBUS) is used as guidance for transbronchial needle aspiration (TBNA), and real-time imaging of the needle position cannot be confirmed with a single-channel bronchoscope. We assessed the usefulness of EBUS-guided TBNA using a double-channel bronchoscope (EBUS-D), which provides real-time needle position, and compared it with EBUS-guided TBNA using a single-channel bronchoscope (EBUS-S).

DESIGN

Randomized, comparative prospective study.

SETTING

Hiroshima City Hospital, a tertiary-referral teaching hospital.

PATIENTS

Between January 2000 and August 2003, 55 patients with intrathoracic lymphadenopathy were included. Patients were randomized to undergo EBUS-D (n = 30) or EBUS-S (n = 25).

METHODS

EBUS-D: The EBUS probe and TBNA catheter were inserted simultaneously through a double-channel bronchoscope. Once the needle placement in the lesion was confirmed by EBUS, TBNA was performed. EBUS-S: The EBUS probe was removed after the determination of the penetration site. Then, the TBNA catheter was inserted and TBNA was performed.

RESULTS

All the lymph nodes could be visualized with EBUS in each group of patients. In the EBUS-D group, the TBNA needle was visualized as a hyperechoic point on the real-time EBUS image. The diagnostic accuracy rate of EBUS-D and EBUS-S were statistically significantly different (97% vs 76%, respectively; p = 0.025). On second attempt of TBNA, the diagnostic rate of the EBUS-D group was superior to that of the EBUS-S group (85.7% vs 33.3%, respectively; p = 0.036). The mean number of penetrations was 1.24 in the EBUS-D group and 1.36 in the EBUS-S group. No complications were observed in the EBUS-D group, but a self-limiting hemorrhage occurred in a patient in the EBUS-S group.

CONCLUSION

EBUS-D is useful for diagnosing intrathoracic lymphadenopathy, and the obtained specimen with real-time confirmation of the needle is directly proportional to an accurate diagnosis.

Endobronchial ultrasonography using a guide sheath increases the ability to diagnose peripheral pulmonary lesions endoscopically

STUDY OBJECTIVE

To assess the ability of endobronchial ultrasonography (EBUS) using a guide sheath (EBUS-GS) to diagnose peripheral pulmonary lesions.

METHOD

We devised a technique for EBUS-GS covering a miniature probe, and 150 lesions were evaluated in a prospective open study. In this procedure, the probe covered by a guide sheath is introduced into the lesion via the working channel of a bronchoscope. The probe is withdrawn, while the guide sheath is left in situ. A brush or biopsy forceps is introduced through the guide sheath into the lesion.

RESULTS

One hundred sixteen of 150 EBUS-GS procedures (77%) were diagnostic. Cases in which the probe was located within the lesion had a significantly higher diagnostic yield (105 of 121 cases, 87%) than when the probe was located adjacent to it (8 of 19 cases, 42%) [p < 0.0001, chi(2)]. The diagnostic yield from EBUS-GS in lesions </= 10 mm (16 of 21 lesions, 76%), >10 to </= 15 mm (19 of 25 lesions, 76%; p = 0.99, chi(2)), >15 to </= 20 mm (23 of 35 lesions, 66%; p = 0.41, chi(2)), and > 20 to </= 30 mm (33 of 43 lesions, 77%; p = 0.96, chi(2)) were similar, demonstrating the efficacy of EBUS-GS even in lesions </= 10 mm in diameter. In 54 of 81 lesions </= 20 mm, fluoroscopy was not able to confirm whether the forceps reached the lesion. However, the yield was the same with (67%, 18 of 27 lesions) and without (74%, 40 of 54 lesions) successful fluoroscopy (p = 0.96, chi(2)). Moderate bleeding occurred in two patients (1%); there were no other complications.

CONCLUSIONS

EBUS-GS is a useful method for collecting samples from peripheral pulmonary lesions, even those too small to be visualized under fluoroscopy.

Catheter-based intraluminal sonography

With the development of interventional and minimally invasive surgical techniques in the last decade, a strong interest in intraluminal sonography has arisen because of the need for better imaging information and management of the interventional procedure. High-resolution intraluminal sonography is a unique approach for the evaluation of a wide range of abnormalities within the luminal structures throughout the body. This imaging technique has been able to obtain information not available with even the most sophisticated percutaneous sonography, CT, or MRI. The uniqueness of this approach has led to extensive research, establishing a variety of clinical applications. These miniature catheter-based transducers have become important supplemental tools in the evaluation of the urinary and gastrointestinal tracts. Other areas need to be evaluated more thoroughly before efficacy is established, but the concept of using miniature transducers has shown promise in many areas of the body. This should lead to the provision of important information for decision making relative to patient care and surgical intervention. In the future, with projected technical progress, intraluminal sonography should substantially improve its diagnostic capabilities.

Analysis of the internal structure of peripheral pulmonary lesions using endobronchial ultrasonography

STUDY OBJECTIVE

To correlate the internal structure of peripheral pulmonary lesions, as visualized by endobronchial ultrasonography (EBUS), and the histology of the surgical specimen to develop a classification system for distinguishing benign from malignant lesions by EBUS.

DESIGN

Retrospective review.

SETTING

A national hospital.

PATIENTS

One hundred twenty-four patients with peripheral pulmonary lesions who had undergone EBUS in whom a definitive histologic diagnosis was made. In 69 patients, EBUS findings were correlated with the histology of a surgical specimen.

INTERVENTION

EBUS was performed by a miniature probe (20-MHz) introduced up to the lesion through a channel in a bronchoscope.

RESULTS

Three classes and six subclasses of lesions were identified by EBUS based on the internal structure of the lesion, focusing on internal echoes, vascular and bronchial patency, and the morphology of the hyperechoic areas, reflecting air in the alveoli and bronchioles. The classes of lesions are as follows: type I, homogeneous pattern (type Ia, with patent vessels and patent bronchioles; type Ib, without vessels and bronchioles); type II, hyperechoic dots and linear arcs pattern (type IIa, without vessels; type IIb, with patent vessels); and type III, heterogeneous pattern (type IIIa, with hyperechoic dots and short lines; type IIIb, without hyperechoic dots and short lines). Twenty-three of 25 type I lesions (92.0%) were benign, while 98 of 99 type II and III lesions (99.0%) were malignant. Twenty-one of 24 type II lesions (87.5%) were well-differentiated adenocarcinomas, and all type IIIb lesions were malignant, including 18 poorly differentiated adenocarcinomas (81.8%).

CONCLUSIONS

EBUS permits the visualization of the internal structure of peripheral pulmonary lesions, and this information suggests the histology of the lesion.

Lung cancer--where are we today? Current advances in staging and nonsurgical treatment

Lung cancer remains the commonest cause of cancer death in both men and women in the developed world, although mortality rates for men are dropping. Spiral computed tomography (CT) of the chest in middle-aged, smoking subjects may identify two to four times more lung cancers than a chest X-ray, with more than 70% of tumors being Stage I. The incidence of benign nodules is high, making interpretation difficult. Randomized controlled trials are required to determine whether spiral CT detects lung cancer early enough to improve mortality. Preoperative staging has relied on CT scans, but positron emission tomography scanning has greater sensitivity, specificity, and accuracy than CT and is recommended as the final confirmatory investigation when the CT shows resectable disease. In locally advanced non-small cell lung cancer, there is a small advantage for the addition of chemotherapy to radiotherapy, but no advantage for postoperative radiotherapy. Chemotherapy gives no benefit when given as neoadjuvant or adjuvant treatment around surgery. In advanced disease, newer cytotoxic agents confer a small survival advantage over older combinations, but the advantage in median survival over best supportive care remains a few months with modest improvements in quality of life. Survival with small cell lung cancer has shown little increase over the last 15 years despite multiple attempts to manipulate the timing, dose intensity of chemotherapy, and the potential of radiotherapy. Novel therapies are urgently needed for all cell types of lung cancer.

Peripheral pulmonary diseases: evaluation with endobronchial US initial experience

Endobronchial ultrasonography (US) with 4.5-F small-caliber US probes, combined with bronchoalveolar lavage technique, was evaluated in autopsied lungs and 22 patients with various pulmonary interstitial or alveolar diseases. Several different echoic patterns were found that may reflect changes due to pathologic alteration of lung parenchyma. This technique may have potential for evaluation and diagnosis of peripheral lung diseases.

Endobronchial ultrasonography for mediastinal and hilar lymph node metastases of lung cancer

STUDY OBJECTIVES

Conventional radiologic procedures are frequently unreliable in the diagnosis of mediastinal and hilar lymph node metastases of lung cancer. In order to improve diagnostic accuracy, we performed endobronchial ultrasonography (EBUS) during bronchofiberscopic examinations of patients with lung cancer.

METHODS AND PATIENTS

To evaluate mediastinal and hilar lymph node metastases, EBUS was performed prospectively using a radial scanning probe of 20 MHz through a bronchofiberscope.

RESULTS

We observed hilar lymph nodes (10R, 11R superior, 11R inferior, 12R, 10L, 11L, 12L) in 20 of 37 patients who underwent EBUS, and we could clearly identify whether direct invasion of the pulmonary artery by a lymph node had occurred. Of the 27 patients who showed no hilar lymph nodes on chest CT scan, lymph node swellings < 10 mm or > or = 10 mm in diameter were identified by EBUS in 9 patients and 2 patients, respectively. Interestingly, EBUS also revealed that the pulmonary artery was directly invaded by an interlobar lymph node < 10 mm in diameter in one patient. In most patients, lymph node 7 was easily identified and was clearly differentiated from the surrounding esophagus, vessels, and mediastinal fat tissue by EBUS. However, fused lymph nodes or lymph nodes with low central density when visualized by chest CT scan were occasionally observed as independent lymph nodes by EBUS. When compared with the pathologic diagnosis of lymph node metastasis in 16 patients who underwent surgery, the most specific and sensitive method for identifying lymph node metastases were EBUS alone (92%) and EBUS in combination with CT scan (100%), respectively. The overall accuracy of EBUS was 94% for the diagnosis of direct invasion of the pulmonary arteries by a hilar lymph node.

CONCLUSIONS

EBUS in combination with conventional radiologic tools may contribute to improved staging, especially in surgical cases with hilar lymph node metastases.

Bronchoscopic ultrasonography in the diagnosis of tracheobronchial invasion of esophageal cancer

OBJECTIVE

To study the usefulness of bronchoscopic ultrasonography in diagnosing tracheobronchial invasion of esophageal cancer and to compare it with endoscopic ultrasonography, bronchoscopy, and computed tomography.

METHODS

We prospectively investigated 59 patients with newly diagnosed esophageal cancer located at or above the level of the tracheal bifurcation. A 20-MHz ultrasonic probe covered by a sheath with a balloon inflated with water was used for bronchoscopic ultrasonography. The presence of tracheobronchial invasion was diagnosed on the basis of an interruption in the most external hyperechoic layer of the tracheal bronchus.

RESULTS

Bronchoscopic ultrasonography was completed without complications in all patients, but endoscopic ultrasonography was performed completely in only 44% of them. The overall accuracy rates for diagnosis of tracheobronchial invasion on the basis of bronchoscopy, bronchoscopic ultrasonography, endoscopic ultrasonography, and computed tomography were 78%, 91%, 85%, and 58%, respectively. Statistical examination showed that the accuracy of bronchoscopic ultrasonography and bronchoscopy was significantly greater than that of computed tomography, and the accuracy of bronchoscopic ultrasonography was greater than that of bronchoscopy.

CONCLUSIONS

Bronchoscopic ultrasonography is useful for evaluating cancer invasion into the tracheal bronchus. It is more accurate than the other methods and could be used to visualize the layered structure of the tracheal bronchus in all patients.

Correlation between endobronchial ultrasonography (EBUS) images and histologic findings in normal and tumor-invaded bronchial wall

The aim of this study was to examine the ability of endobronchial ultrasonography (EBUS) to image the bronchial wall structure in order to assess the depth of bronchial tumor invasion. Sixty-one patients who underwent lobectomy, pneumonectomy or forceps biopsy were included in this study. In 21 patients with bronchoscopically visible bronchial malignant tumors, EBUS was performed during bronchoscopy. In the remaining 40 patients, ultrasonography was performed on the resected specimens. The EBUS findings obtained using thin ultrasonic probes (20 MHz radial scanner) were compared with the macroscopic and histologic findings of the corresponding areas in the resected specimens. When the bronchial walls were imaged while immersed in normal saline, six ultrasonically distinct layers were detected in the cartilaginous and membranous portions. A similar wall structure was imaged when EBUS was performed during bronchoscopy using a latex balloon sheath. The image of the lamina propria and submucosa was occasionally compressed and mixed with a balloon echo due to the latex balloon sheath, whereas the cartilage layer was always distinctly imaged. A good correlation was observed between the EBUS-determined cartilage thickness and the actual histologic measurement, as measured with vernier calipers. Malignant tissues were imaged as hypoechoic areas, and tumor invasion of the cartilage layer was clearly detected. In conclusion, using high-resolution (20 MHz) ultrasonic probes, the bronchial wall structure could be imaged as six distinct layers. The cartilage layer was easily identified and could be used as a reference to evaluate the rest of the bronchial wall structure.

Semi-invasive and invasive procedures for the diagnosis and staging of lung cancer. II. Bronchoscopic and surgical procedures

Each of the various techniques used for the diagnosis and staging of lung cancer has its advantages and limitations (Table 1). Imaging has a major role in guiding these procedures and deciding which of them is most appropriate in a given clinical setting. A CT examination by which the size and location of the parenchymal lesion and the presence and location of enlarged lymph nodes can be determined is a prerequisite for all sampling procedures. As a general rule, when attempting to diagnose a solitary pulmonary nodule or mass, central lesions are more easily approached by the bronchoscopic route, whereas a transthoracic route is preferred for peripheral lesions. Bronchoscopy is often performed using fluoroscopic guidance, and the recently developed CT fluoroscopy and endoscopic ultrasound have the potential to facilitate transbronchial needle aspiration. A recent advent in imaging of lung cancer has been the introduction of positron emission tomography to the diagnostic work-up of lung cancer. Although this technique has been shown to be highly accurate in determining the malignant or benign nature of lesions, it does not enable histologic diagnosis. In each case, the most appropriate diagnostic procedure should be tailored to suit the specific requirements determined by the characteristics of the disease process, institutional availability of the various diagnostic procedures, and patient preferences, when possible.

Advances in ultrasound biomicroscopy

The visualisation of living tissues at microscopic resolution is attracting attention in several fields. In medicine, the goals are to image healthy and diseased tissue with the aim of providing information previously only available from biopsy samples. In basic biology, the goal may be to image biological models of human disease or to conduct longitudinal studies of small-animal development. High-frequency ultrasonic imaging (ultrasound biomicroscopy) offers unique advantages for these applications. In this paper, the development of ultrasound biomicroscopy is reviewed. Aspects of transducer development, systems design and tissue properties are presented to provide a foundation for medical and biological applications. The majority of applications appear to be developing in the 40-60-MHz frequency range, where resolution on the order of 50 microm can be achieved. Doppler processing in this frequency range is beginning to emerge and some examples of current achievements will be highlighted. The current state of the art is reviewed for medical applications in ophthalmology, intravascular ultrasound, dermatology, and cartilage imaging. Ultrasound biomicroscopic studies of mouse embryonic development and tumour biology are presented. Speculation on the continuing evolution of ultrasound biomicroscopy will be discussed.

Assessment of usefulness of endobronchial ultrasonography in determination of depth of tracheobronchial tumor invasion

STUDY OBJECTIVE

We assessed the usefulness of endobronchial ultrasonography in the determination of the depth of tumor invasion of the tracheobronchial wall.

METHODS

We performed a needle-puncture experiment on normal tissue of 45 specimens to determine the laminar structure of the tracheobronchial wall. In addition, we compared the ultrasonographic determinations of tumor invasion from 24 lung cancer cases with the histopathologic findings.

RESULTS

The cartilaginous portions of the extrapulmonary bronchi and the intrapulmonary bronchi exhibited a five-layer structure. Starting on the luminal side, the first layer (hyperechoic) was a marginal echo, the second layer (hypoechoic) was the submucosal tissue, the third layer (hyperechoic) was the marginal echo on the inner side of the bronchial cartilage, the fourth layer (hypoechoic) was bronchial cartilage, and the fifth layer (hyperechoic) was the marginal echo on the outer side of the cartilage. In the membranous portions, the first layer (hyperechoic) was a marginal echo, the second layer (hypoechoic) was smooth muscle, and the third layer (hyperechoic) corresponded to the adventitia. Comparisons between the ultrasonograms and the histopathologic findings in 24 lung cancer cases revealed that depth diagnosis was the same in 23 lesions (95.8%) and was different in 1 lesion (4.2%). In the single case in which the findings were different, lymphocytic infiltration that protruded between the cartilage rings was mistakenly interpreted as tumor infiltration.

CONCLUSIONS

This method allows visualization of the laminar structure of the tracheobronchial wall, which is impossible with other diagnostic imaging methods.

2-D and 3-D endoluminal ultrasound: vascular and nonvascular applications

Endoluminal ultrasound using catheter-based transducers has been used for the evaluation of a wide range of abnormalities. To date, one of the most promising areas of clinical application is its use intravascularly for quantitating the degree of arterial stenosis and for monitoring the therapeutic effects of angioplasty in peripheral and coronary arteries. Uses in the gastrointestinal tract include quantification of the size and wall thickness of esophageal varices, distinguishing between various submucosal lesions and measuring the degree of fibrosis in scleroderma. In the genitourinary system, endoluminal ultrasound provides a unique intraoperative tool allowing the addition of a third dimension (depth) to endourological procedures. The indications for, and the use of, endoluminal ultrasound within the upper urinary tract can be expected to increase with more experience, and the procedure has become an important technique that yields information not available through other modalities. In the bronchotracheal tree, endoluminal ultrasound allows imaging and subsequent biopsy of lymph nodes and tumors that cannot be visualized at routine bronchoscopy. Three-dimensional (3-D) reconstruction of two-dimensional (2-D) ultrasound imaging is a new method in the evolution of intraluminal imaging. It provides information about spatial relationships of anatomic structures that cannot be evaluated using conventional 2-D imaging. Although still in its infancy, 3-D endoluminal ultrasound has the potential to become a dynamic tool in both the research and clinical areas.

Percutaneous transhepatic intraductal biliary sonography for lymph node staging at 12.5 MHz in malignant bile duct obstruction: work in progress

PURPOSE

To assess the value of intraductal ultrasound (US) for lymph node staging in malignant biliary obstruction.

METHODS

Eighteen patients with malignant extrahepatic obstruction were imaged during percutaneous bile duct drainage with a mechanically rotating US transducer at 12.5 MHz. Detectable lymph nodes were classified as malignant when two of three criteria (hypoechoic, rounded, conspicuous margins) were fulfilled. The results were compared with histopathological data in 8 patients and follow-up CT findings in 10 patients.

RESULTS

In 15 of 18 patients (83%) malignant lymph node involvement was suspected at intraductal US and in 5 of 18 patients (28%) during CT. Histopathological investigation after operation (n = 8) and follow-up CT studies (n = 10) revealed the presence of malignant nodal involvement in 13 of 18 (72%) patients. The sensitivity, specificity, and accuracy of transhepatic intraductal biliary US in determining merely the presence or absence of malignant lymph nodes without specific topographic assignment were 92%, 40%, and 78%, respectively.

CONCLUSION

These preliminary results suggest that intraductal US may develop into a promising adjunctive modality during percutaneous bile duct drainage in patients with suspected malignant regional lymph node involvement.

Thoraxsonography--Part II: Peripheral pulmonary consolidation

In many cases of pulmonary diseases extending up to the pleura, ultrasound (US) helps to identify the etiology of the lesion. There are several sonomorphological criteria to differentiate peripheral pulmonary consolidations. Pneumonic infiltration shows a hypoechoic inhomogeneous echo texture, with multiple air inlets and bronchoaerograms. Fluid bronchogram indicates an obstructive pneumonitis. Pulmonary infarctions are visible in different stages as triangular pleural-based lesions in most cases of pulmonary embolism. The diagnostic accuracy of chest sonography in pulmonary embolism was 85%-90%. US-guided transthoracic biopsy shows a diagnostic yield of > 90% in malignancies and 50%-83% of benign lesions. The overall complication rate is very low: 1%-2% hemoptysis, 2%-4% pneumothoraces and 1%-2% requiring chest tube drainage. Color Doppler US can demonstrate the vascular patterns and may help in the understanding of underlying pathophysiology. Sonographic examinations of the upper and central mediastinum provide good results in 90-95% of cases. Some anatomical limitations of transcutaneous US can be circumvented by endoluminal US.

Non-small-cell lung cancer: detection of mediastinal lymph node metastases by endoscopic ultrasound and CT

In this prospective study endoscopic ultrasound (EUS) and computed tomography (CT) were evaluated to compare diagnostic accuracy of the two methods. They were performed for nodal staging in selected patients admitted to our institution for non-small-cell lung cancer (NSCLC). From February 1992 to July 1993, 45 patients were recruited for the study when N3 and N2 nodal involvement were excluded on standard chest X-ray. All the patients completed EUS and CT exams for staging before treatment. The results of sensitivity, specificity and accuracy were obtained in 30 patients who underwent surgical treatment with macroscopically radical resection of T and N, which allowed a complete surgical and histological comparison of CT and EUS findings. On a per-patient basis CT results were: sensitivity 63.6%, specificity 78.9% and accuracy of 73.3%; on a nodal station basis sensitivity, specificity and accuracy were 70.0%, 85.1% and 81.6%, respectively. The EUS evaluation showed, on a per-patient basis, values of sensitivity 45.5%, specificity 57.9% and overall diagnostic accuracy of 53.3%. On a nodal station basis the results were 50.0%, 86.6% and 78.2%, respectively. The results obtained in the 30 patients when both techniques were taken in association regarding sensitivity (90.9%), specificity (73.7%) and accuracy (80.0%) on a per-patient basis suggest that the association of EUS and CT offers the best approach for preoperative staging of NSCLC.