**2.2 Pre-operative imaging and endoscopy**

Computerized tomography (CT) is a very good diagnostic tool with excellent Risk–Benefit Ratio. It is readily accessible, with faster image acquisition. One of the advantages of CT is that it can also be extended to include other sites of the body for staging purposes especially in cancer cases. Thin Slices, high resolution image acquisition allows high quality multiplanar reconstruction (**Figure 3**). Drawbacks of CT include exposure to ionizing radiation, inferior soft tissue contrast when compared to MRI, renal failure secondary to injection of iodinated contrast medium (**Table 1**).


**Figure 2.** *AS a grading used for predicting anesthesia risk.*

**Figure 3.**

*(a) Chet X-ray showing tracheal deviation at T4-T5 level. (b) 3D reconstruction of MDCT with virtual endoscopy showing tracheal stenosis. (c) Sternum eroded by thyroid cancer metastasis. (d, e, f) coronal cut contrast enhances MDCT showing narrowing at level T4-T5 along with enlarged thyroid.*

#### **2.3 CT virtual endoscopy**

Virtual endoscopy is an excellent tool used to obtain an anatomically similar representation of the intraluminal geography of the airway, including supraglottic, glottic and subglottic structures without the risk of exposure to ionizing radiation. Compared to conventional 3D reconstructions, the images obtained through virtual endoscopy give a perspective which, when rendered, creates the impression of a true endoscopic image allowing for a tailored approach towards the airway management (**Figure 3b**).

One of the limitations of virtual endoscopy, especially in airway pathologies, is that dynamic airway studies cannot be assessed. Hence, conventional airway endoscopy remains the "gold standard" in most airway assessment and pathologies. Virtual endoscopy can be used to supplement conventional airway endoscopy to help in planning the management of such cases [2].

#### **2.4 MRI**

MRI gives excellent contrast resolution compared to CT and is a useful in identifying specific characteristics pertaining to soft tissue masses and complex soft tissue lesions [2]. Even though the unwanted risks of ionizing radiation are absent with the use of MRI as compared to CT, images can be prone to motion artifact due to increased acquisition times that often require the patient to stay still for at least several minutes at a time.

Dynamic MRI is a useful tool in diagnosing certain uncommon airway pathologies such as in diagnosis of tracheo-broncho-malacia in pediatric population, in sleep studies for visualization of upper airway dynamics etc.

Mass effect leading to airway compromise from benign and malignant lesions such as hemangioma and lymphomas are more conspicuous on MRI, with high T2 signal intensity, compared to CT [3].

**131**

**USG**

> •

It is currently

•

Useful in emergencies

•

Has been used extensively

•

Images are reconstructed

•

Limited use due to

•

It is upcoming revolutionary

technology in which 3D models

are printed using 3D printers

with the data acquired from CT

scans.

•

Can be used in simulation of

airway for precision Preoperative

planning.

increased cost and time

consuming.

using data from helical CT.

in evaluation and planning of pediatric airway. More precise and superior

•

Virtual endoscopy can be

compared to real airway

•

Defines soft tissue lesions

better when compared

to CT.

•

It is non ionizing when

compared to CT hence can

be considered for certain

•

Has potential for vast applications in anesthesia training,

planning and management.

pediatric conditions.

endoscopic evaluation as it

saves administration of local

or general anesthesia and

improves patient compliance.

compared to X-ray.

for quick diagnosis.

one of the most

explored and utilized radiological

•

Lateral views are

most commonly used.

Flexion, extension and

frontal views can also

•

Tracheal lesions are characterized better compared

modality.

•

It is relatively

cheap and easily.

be used.

Accessible.

•

Used for Prediction

to X-ray.

of difficult airway,

•

Conditions such as

•

One of the drawbacks of

virtual endoscopy is that it is

not useful in dynamic airway

•

Dynamic MRI is a Useful

tool in diagnosing

•

The technology is presently in

its nascent stage and hence not

a viable option for a majority of

certain uncommon airway

pathologies such as in

diagnosis of tracheobronchomalacia in pediatric

cases.

population, in sleep

studies for visualization

of upper airway dynamics

etc.

studies.

tracheomalacia, fistula,

etc. not seen in X-ray can

be picked up on CT.

size and depth of left

double lumen endotrachial tube (DLT).

•

Can be performed in a non teritiary setting.

•

It has certain

limitation such

•

Used for confirmation

•

Study of static and

•

Then can also be easily

extended to involve the

bronchus.

dynamic airway anatomy

possible with CT.

of ET tube position.

has in deeper

lesions.

•

For diagnosing

tracheal lesions.

•

Can also be used for

Evaluation of airway narrowing and deviation, for

predicting left DLT size

and difficult airway

**Table 1.**

*Comparing the different radiological modalities.*

**X-ray**

**CT**

**CT reconstruction and virtual endoscopy**

**MRI**

**3D-printing**

*Airway Management in Head and Neck Pathology DOI: http://dx.doi.org/10.5772/intechopen.94498*

#### *Airway Management in Head and Neck Pathology DOI: http://dx.doi.org/10.5772/intechopen.94498*

*Special Considerations in Human Airway Management*

**2.3 CT virtual endoscopy**

several minutes at a time.

signal intensity, compared to CT [3].

help in planning the management of such cases [2].

studies for visualization of upper airway dynamics etc.

Virtual endoscopy is an excellent tool used to obtain an anatomically similar representation of the intraluminal geography of the airway, including supraglottic, glottic and subglottic structures without the risk of exposure to ionizing radiation. Compared to conventional 3D reconstructions, the images obtained through virtual endoscopy give a perspective which, when rendered, creates the impression of a true endoscopic image allowing for a tailored approach towards the airway management (**Figure 3b**). One of the limitations of virtual endoscopy, especially in airway pathologies, is that dynamic airway studies cannot be assessed. Hence, conventional airway endoscopy remains the "gold standard" in most airway assessment and pathologies. Virtual endoscopy can be used to supplement conventional airway endoscopy to

*(a) Chet X-ray showing tracheal deviation at T4-T5 level. (b) 3D reconstruction of MDCT with virtual endoscopy showing tracheal stenosis. (c) Sternum eroded by thyroid cancer metastasis. (d, e, f) coronal cut* 

*contrast enhances MDCT showing narrowing at level T4-T5 along with enlarged thyroid.*

MRI gives excellent contrast resolution compared to CT and is a useful in identifying specific characteristics pertaining to soft tissue masses and complex soft tissue lesions [2]. Even though the unwanted risks of ionizing radiation are absent with the use of MRI as compared to CT, images can be prone to motion artifact due to increased acquisition times that often require the patient to stay still for at least

Dynamic MRI is a useful tool in diagnosing certain uncommon airway pathologies such as in diagnosis of tracheo-broncho-malacia in pediatric population, in sleep

Mass effect leading to airway compromise from benign and malignant lesions such as hemangioma and lymphomas are more conspicuous on MRI, with high T2

**130**

**2.4 MRI**

**Figure 3.**


**Table 1.**

*Comparing the different radiological modalities.*

**Figure 4.**

*Example of fiber optic tracheoscopy on a tracheal stenosis patient under local anesthesia showing the carina (a) and stenosed part of the trachea (b).*
