Introduction:
Cancer is one of the most fatal disorders of modern times. The survivability of cancer patients depends upon early and accurate diagnosis of cancer. Lung cancer is the second most predominant cancer in the world. It is the most common cancer in men and the second most common cancer in females. Around 2.21 million new cases of lung cancer have been diagnosed last year. Also, 1.8 million people have lost their lives due to this disorder. Endoscopic ultrasonography or endosonography is a new method that can be helpful for diagnosing lung cancer.
What Is Ultrasonography?
Ultrasonography is a non-invasive technique. In this procedure, ultrasound sound waves are projected toward the organs through a transducer. These soundwaves bounce off the organs like an echo and are captured by the transducer, which then processes these data from an image of the object.
This ultrasound technique has been combined with two other methods to visualize lung structures. These two techniques are bronchoscopy and endoscopy. In the bronchoscopy procedure, a thin tube is passed through the airway passage via the nose or mouth to visualize the structure of the respiratory system. In the endoscopy procedure, a thin is passed through the mouth to evaluate the structure of the digestive system. Based on these two techniques two different types of ultrasonographic techniques have developed. Endoscopic ultrasound of the lungs is done through the digestive canal and endobronchial ultrasound is done through the respiratory tract.
How It Is Done?
Before the procedure, all the vital parameters are accessed. The patient is positioned on a couch lying down on the left side. In general, the procedure is done under sedation and under local anesthesia. The throat portion is anesthetized. The endoscope is inserted into the throat and during this procedure, a patient may experience a gag during this procedure. During the endoscopic ultrasound, the probe is inserted in the esophagus, and during the endobronchial ultrasound, it is inserted in the trachea.
What Is Endoscopic Ultrasound?
As discussed endoscopic ultrasound is used to access the lung lesion through the esophagus. The benefits of this procedure are the assessment of extrapulmonary structures and the extension of the lesions outside of the lungs. Also, endoscopic ultrasound is better tolerated and the viewing angle is wider. It also offers better visualization of the small structures. Also, due to the absence of hard cartilage, a better orientation of the probe is possible. Not only that is better tolerated in patients suffering from cardiorespiratory distress. Examination and sampling of the left adrenal gland and coeliac lymph nodes can be possible through this technique. Assessment of liver metastasis is also possible in this process.
What Are the Types Of Endobronchial Ultrasound?
Endobronchial ultrasound can be of two types. These are:
Radial Endobronchial Ultrasound:
The transducer used for this purpose is rotating in nature. The frequency of the ultrasound probe is 20 MHz (with a range between 12 to 30 MHz). It can be inserted with or without the guide sheet through a working channel of the bronchoscope with a diameter of 2.0 to 2.8 millimeters. The diameter of the transducer probe also may vary from 1.4 to 2.6 millimeters. In general two types of probes are used one is the peripheral probe and another is the central probe. The peripheral probe has no balloon attached to it and is used to locate peripheral lung lesions. The central probes have balloons attached to them which can be used to access the wall of the respiratory system and the lymph nodes. The function of the balloon is to retract the distal portion of the respiratory system to facilitate the imaging procedure.
In radial endobronchial ultrasound, 360-degree imaging of the lung tissue is possible. But the rotation of the transducer probe must be passive. An active rotation of the probe may cause injury to the respiratory tube. That is why radial endobronchial ultrasound is always should be done after examination of the tracheobronchial tube with the help of a standard bronchoscope. In general inflation of the balloon is well tolerated by the patient under sedation. One of the main challenges of the radial endobronchial ultrasound procedure is the orientation of the images. After obtaining images, images should be matched with anatomical landmarks for orientation.
Linear Endobronchial Ultrasound:
In this type, the probe is built into a dedicated flexible bronchoscope. The diameter of the bronchoscope is 6.9 millimeters which are larger than the stranded bronchoscope. This wide-angle oral is done through oral intubation. The viewing angle of this type of probe is a 30-degree oblique angle and the frequency is 7.5 MHz due to this limited view, the insertion of such a transducer and view is difficult. That is why such probes are mainly used for aspiration biopsy purposes. This procedure is known as e EBUS-TBNA. The diameter of the needle used for this procedure is 21G and the depth of the penetration is 5 to 44 millimeters.
After endobronchial intubation, the EBUS-TBNA probe is positioned close to the target lymph node. After this, the needle sheath is pushed forward such that it is visualized on the endoscopic image, and the jabbing technique is used to extract the tissue sample in real-time mode. The stylet of the needle is used to agitate the tissue to remove any air entrapment. Aortopulmonary, sub-aortic, para-esophageal, and pulmonary ligament nodes are not accessed through this procedure.
What Is the Use of Endoscopic Ultrasound?
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Localization of the lung lesions and evaluation of the lung lesions in the real-time view.
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Identification of the lung and respiratory lesions and assessment of the extension.
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Tissue sampling for the biopsy procedure is possible.
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Accurate staging of lung cancer is possible.
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Assessment of metastasis is possible.
Conclusion:
Early and accurate detection of lung lesions is necessary for cancer treatment. The endosonography procedure utilizes a combination of endoscopy and ultrasound techniques for the identification of lung lesions. Also, fine needle aspiration biopsy is also possible through this technique. Staging of cancer and metastasis of cancer can also be accessed.
