Endobronchial Ultrasonography – EBUS

Clinical Applications

(A) Determination of the Depth of Tumor Invasion of the Tracheal/ Bronchial Wall,

(B) Analysis of the Structure of the Bronchial Wall for Airway Diseases Such As Tracheobronchomalacia,

(C) Identification of the Location of a Peripheral Lung Lesion during Bronchoscopic Examination. Radial Probe Ebus Is More Accurate Than Fluoroscopy In Determining Contact Between Lesion And Bronchus. Therefore It Reduces the Time to Determine the Biopsy Sites and the Duration of Fluoroscopy,

(D) Qualitative Analysis of Peripheral Lung Lesions to Differentiate Between Benign and Malignant Lesions,

(E) Guidance For Transbronchial Needle Aspiration-Radial Probe Ebus Is Largely Replaced By Convex-Robe Ebus For This Indication.

Equipment

• A 20 MHz mechanical radial ultrasonic probe with a balloon- tip sheath is used, that can be introduced through the 2.8 mm diameter working channel of a flexible bronchoscope.
• These probes are connected with the Endoscopic Ultrasound System to obtain EBUS images.

Performing EBUS Using a Balloon Probe

• The balloon probe is inserted into the working channel of the bronchoscope, advanced beyond the lesion, and then inflated with the minimum amount of saline required to obtain an EBUS image of the entire circumference of the bronchial wall.
• Scanning is performed while retracting the probe slowly.
• Advancing the probe from proximal to distal airways can cause damage to the probe, and should be avoided.
• Using a 20 MHz probe, five layers can be identified on ultrasound images of the cartilaginous portion of extra pulmonary and intrapulmonary bronchi.

• The first layer (hyper echoic) is a marginal echo,
• The second layer (hypo echoic) represents sub mucosal tissue,
• The third layer (hyper echoic) is the marginal echo on the inner aspect of the bronchial cartilage,
• The fourth layer (hypo echoic) represents bronchial cartilage, and
• The fifth layer (hyper echoic) is the marginal echo on the outer aspect of the bronchial cartilage.
• For determination of the depth of tracheobronchial tumor invasion using EBUS, one must carefully examine the third and fourth layers that correspond to the bronchial cartilage.
• An important limitation of preoperative EBUS in determination of the depth of tumor invasion is difficulty is distinguishing lymphocytic infiltration from tumor invasion.
• As ultrasonography visualizes tissues according to the speed of propagation of ultrasound waves, it is seen that the speed of ultrasound waves from the 20 MHz probe through invasive cancer is similar to that through lymphocytic infiltrates and hypertrophied bronchial glands.

Convex probe EBUS

Introduction

• The radial probe EBUS has remained useful for a variety of purposes:
• To identify the location of mediastinal nodes before performing transbronchial needle aspiration (TBNA) procedures
• To evaluate the depth of tumor invasion into the tracheobronchial wall : and
• To guide bronchoscope tools to obtain tissue specimen from solitary pulmonary nodules and peripheral lesions.
• Although radial probe EBUS allows the operator to visualize the structures outside the bronchial wall, real time guidance for the biopsy of lesions beyond the airway wall is not feasible.
• To overcome this limitation, a convex probe EBUS which is built directly onto the distal tip of the bronchoscope has been developed that allows for real-time visualization and guided biopsy of mediastinal Structures.

Mediastinal Sampling – Need for EBUS TBNA

• Mediastinoscopy -good yield, but highly invasive
• Conventional TBNA-less invasive but yield variable
• All lymph node stations cannot be sampled with either
• EBUS-TBNA has emerged as a technique that combined the high yield of mediastinoscopy with the minimal invasiveness of TBNA.

Indications

• The main indications of EBUS-TBNA are the mediastinal and hilar staging of ca. Lung, diagnosis of suspected cancer when no endobronchial lesion is present in patients with lymphadenopathy, and recurrence or restaging of NSCLC after chemotherapy or radiation.
• Other indications include any causes of mediastinal lymphadenopathy such as suspected sarcoidosis, infections such as tuberculosis, mediastinal lymphoma, thymoma, and mediastinal cysts.
• In addition, EBUS-TBNA can assist in guiding therapy by measuring the depth of tumor invasion into the airway wall, or for tissue banking and molecular testing.
• The optical view of the EBUS scope is 30 degrees to the horizontal, not the typical 0-degree view of a standard scope.
• This has practical implications in that to obtain a forward 0-degree view, the scope must be flexed to -30 degrees; otherwise one can unknowingly injure the vocal cords or bronchial wall if the bronchoscope is advanced in neutral position.
• The needle channel is built such that the EBUS-TBNA needle placed through the scope extends at an angle of 20 degrees to its axis as it emerges out of the distal tip.
• The channel angulation is needed to ensure real-time ultrasound visualization of the biopsy needle as it is advanced through the airway and into the lymph node
• The EBUS TBNA needle is longer, grooved with stylet.

Procedure

• Identify the node to be sampled using the ultrasound image
• Proper identification of the nodal station can be carried out through both direct visualization of where the tip of the scope lies as well as through the visualization of anatomic structures within the ultrasound image’s field of view
• The EBUS needle catheter is advanced through the working channel and locked in position
• Needle is advanced till visualized in usg image
• Once within the node,
• The inner stylet should be tapped or slightly withdrawn and advanced several times to eject any debris that may have collected during insertion through the bronchial wall.

Complications

Complications Are Very Very Minimal

• Pneumomediastinum
• Pneumothorax
• Hemomediastinum
• Mediastinitis
• Bacteremia
• Similar To Conventional TBNA Procedure, Bleeding Complications Are Rare, Even If Major Vessels Are Punctured Inadvertently