Evirgen S, kamburoglu K.

World J Radiol 2016 January 28; 8(1): 50-58.

REVIEW ON THE APPLICATIONS OF

ULTRASONOGRAPHY IN

DENTOMAXILLOFACIAL REGION

Journal club: 14

Dr Sanjana Ravindra

Dr Sanjana RavindraRajarajeswari Dental CollegeBangalore

Introduction

Sonography – technique based on sound waves that acquire images in real time without the use of ionizing radiation.

‘‘Ultra’’ means beyond or in excess

‘‘Sound’’ means audible sound energy

The term ultrasound means the form of sound energy beyond audible range

Ultrasound wave is a form of longitudinal mechanical wave

that needs a medium to transmit from one place to anotherDr Sanjana Ravindra

• Human ear can hear only a limited range of sound frequencies- range between 20Hz - 20,000Hz

• Frequencies below the audible range (i.e. < 20Hz)-‘infrasonic‘

• Frequencies above the audible range (i.e. >20,000Hz)-‘ultrasonic’

Ultrasound used for diagnostic purposes has a frequency of 2MHz

– 20MHz

Introduction

Dr Sanjana Ravindra

HISTORY

1794 Spallanzani

Demonstrated the existence of Ultrasound in bats

1912 Richardson invented the echo locator based on the idea of

ultrasound used for navigation and detection of objects in water

1942 Dussik K.T & Friederick reported the first successful application of ultrasound to

medical diagnosis

Dr Sanjana Ravindra

1971 Daly and Wheeler carried out ultrasound imaging of dental soft tissues to find out the

use of ultrasonic measurement in clinical evaluation of oral soft tissues

1954 Kallnus developed Doppler ultrasound

1977 Ferguson MM et al demonstrated the use of ultrasonography in the diagnosis of cystic

hygroma of the neck

1976 Nieman demonstrated the use of ultrasonography to detect parotid masses

1978 Pickrell KL was the first to use ultrasonography for localization of parotid gland calculus

HISTORY

Dr Sanjana Ravindra

Some of them are partially reflected from the interface between different tissues and returns to the transducer

Sound waves travel into body and hit the tissues and organs

Transducer sends high-frequency sound pulses (1 to 5 MHz) into our body

Transducer calculates the distance from it to the tissues and transmits the echoes electrically onto a monitor.

Dr Sanjana Ravindra

All diagnostic ultrasound applications are based on detection and display of

acoustic energy reflected from interfaces with in the body

These interactions provide information needed to generate high resolution

gray scale images of body and related to blood flow

Dr Sanjana Ravindra

INSTRUMENTATION

Transmitter

Transducer

Receiver

Processor

Display

Record and storing of

image

Dr Sanjana Ravindra

TRANSMITTER

Energize the transducer by application of precisely timed,

high amplitude voltage

Controls rate of pulses emitted by transducer

No. of pulsed echoes produced in each sec is PRF

(pulse repetition frequency)

Doubling PRF causes Better Resolution of the image

Dr Sanjana Ravindra

TRANSDUCER

1. Piezoelectric crystals

2. Two electrodes

3. Backing layer

4. Matching layer

5.Acoustic insulator (rubber

)

6. Plastic housing

• Device which converts one form of energy to other

• In US, it converts electrical energy to ultrasonic energy & vice versa

• Transducer is both a transmitter & a receiver

Dr Sanjana Ravindra

TRANSDUCER - PIEZOELECTRIC CRYSTALS

Thin piezoelectric crystal (0.5mm) element located near face of transducer

Front and back surface of crystal is coated with conducting film to ensure good contact with electrodes

Outside electrode is grounded to prevent electric shock to patient & inner electrode abuts against a thick backing block.

Housing is usually a strong plastic.

• Naturally occurring

piezoelectric material – quartz,

Rochelle salt, topaz, and dry

bone

• Man made piezoelectric

materials are called

“ferroelectric materials”

• Eg: Barium titanate, Lead

zirconate titanate (PZT),

Polyvinylidene difluoride

(PVDF)

Dr Sanjana Ravindra

TRANSDUCER - BACKING LAYER

Made of tungsten with rubber

powder and epoxy resin

Backing material occupies the

space behind the crystal,

Dampens the vibrations

Accepts all waves that it receives

and completely absorb the energy

of waves

Dr Sanjana Ravindra

TRANSDUCER - MATCHING LAYER

Made of aluminum powder and

epoxy resin

Matching layer optimizes the

transmission of sound energy into

patient by providing a medium that is

intermediate in acoustic properties of

a piezoelectric crystal and tissue of

the patients

Dr Sanjana Ravindra

RECEIVER

Receives , detects and amplifies the weak returning

signals

Also provides compensatory amplification of the

weaker signals those arising from deeper tissues - time

gain compensation (TGC)

It compresses and re-maps the wide range of

amplitudes returning to transducer into narrow range

Dr Sanjana Ravindra

SIGNAL PROCESSOR

Display screen is divided into a matrix of pixels

Image of all signal reflections are formed and displayed

on monitorDr Sanjana Ravindra

All ultrasound transducers contain a range of frequencies, termed

bandwidth

- 2.5 - 3.5 MHz for general abdominal imaging

– 5.0 - 7.5 MHz for superficial imaging

Dr Sanjana Ravindra

INTERPRETATION OF USG IMAGE

Sonographic images are identified in terms of echoes

Different structures emit different signals on US imaging - termed as echogenicities

Higher the reflection --- higher the echogenicity

Hyperechoic structures- appear white and bright

Isoechoic - same density as surrounding structures and appear grey

Hypoechoic structures- appear dark, black and produce weak signal

Dr Sanjana Ravindra

The internal echoes may be either homogeneous or heterogeneous.

‘Homogeneous’ refers to an even echo pattern or reflections that are relative and uniform in composition.

If the mass is uniformly hypoechoic or hyperechoic, then it is described as a homogeneous mass.

‘Heterogeneous’ refers to an uneven echo pattern or reflections of varying echodensitities.

If a mass lesion contains hyperechoic and hypoechoic areas, it would be described as a heterogeneous mass

Dr Sanjana Ravindra

ADVANTAGES

Sound waves are not ionizing radiation.

There are no known harmful effects on any tissues at energies & doses currently used in diagnostic ultrasound.

Images show good differentiation between soft tissues.

It performs muscles and soft tissue images very well.

It renders "live" images.

It shows the structure of organs.

Small, easily carried scanners are available.

Technique is widely available & inexpensive.Dr Sanjana Ravindra

DISADVANTAGES

If lesion is very deep or surrounding bone is very thick, ultrasound waves are absorbed by bone.

Ultrasound performs very poorly when there is a gas between the scan head and the organ of interest.

The deep penetration of ultrasound is limited.

The method is operator-dependent

Real-time imaging means that the radiologist must be present during the investigation

Dr Sanjana Ravindra

INDICATIONS

Evaluation of swellings of the neck, particularly those involving thyroid, cervical lymph nodes or major salivary glands — ultrasound is now regarded as the investigation of choice for detecting solid and cystic soft tissue masses

Detection of salivary gland and duct calculi

Determination of the relationship of vascular structures and vascularity of masses with the addition of colour flow Doppler imaging

Assessment of blood flow in the carotids and carotid body tumours

Ultrasound-guided fine-needle aspiration (FNA) biopsy

Dr Sanjana Ravindra

INDICATIONS

Assessment of TMJ disorders

Assessment of the Intraosseous lesions of the jaw

Assessment of cervical lymph node metastasis

Assessment of Maxillofacial space infections Assessment of Soft tissue lesions such as carcinoma of tongue

Dr Sanjana Ravindra

In the assessment of congenital vascular lesions of the maxillofacial region.

To characterize the flow of head and neck vascular anomalies and to differentiate hemangiomas from other vascular malformations.

In monitoring the healing of periapical lesions after surgery.

To identify factors associated with alterations of mental artery flow.

To assess mental artery flow and mental artery pulse strength.

An effective tool in the definitive diagnosis of nonspecific nodular lesions of the soft tissues located in the oral and maxillofacial region.

In the diagnosis and differentiation of benign and malignant salivary gland tumors.

Doppler US Doppler US has found wide spread use in the

assessment

of peripheral vascular disease.

Accuracy of Color doppler US was found to be 95% in determining tumor site

Dr Sanjana Ravindra

MIDFACIAL FRACTURES

Authors of a study used ultrasound in

diagnosing zygomatico-orbital complex fractures

and found an accuracy of 94%

McCann et al found lower accuracy

(85%) in diagnosing fractures of the

zygomatico-orbital complex when compared to

aforementioned study.

Another study, reported accuracy in diagnosing fractures

of the orbital floor

Gülicher et alshowed that

ultrasonographic control of fracture

repair led to excellent results in almost all patients.

• Orbitozygomatical complex fractures• Isolated fractures of the zygomatic arch,

orbital floor, nasal bone, frontal sinus, along with complex Le-Fort fractures

Soft tissue covering of the tissues impairs

imaging of fractures in several

planes.

Therefore, the application of US is not a substitute

for accurately taken X-ray imaging for

detecting fractures of the mandibular

ramus and condyle[

Dr Sanjana Ravindra

Dr Sanjana Ravindra

TEMPOROMANDIBULAR DISORDERS

US, an alternative technique to magnetic resonance imaging (MRI), was

utilized for assessing TMJ in the beginning of 1990´s.

Transverse and

longitudinal scans

Antereriosuperior joint

compartment

Axial, coronal, and oblique

views

Hyperechoic

• Condyle and

• Glenoid fossa

Isoechoic

• Connective

• Muscular tissues

Hypoechoic

• Superior and inferior joint spaces

Dr Sanjana Ravindra

TMJ - DISK

DISPLACEMENT

WITH REDUCTION WITHOUT REDUCTION

Closed mouth

Open mouth

Dr Sanjana Ravindra

Emshoff et al concluded that US was a reliable diagnostic

tool in diagnosing normal disc position at the various mouth

opening positions.

A meta-analysis of US for the detection of TMJ anterior disc

displacement revealed that high resolution US was

superior in the diagnosis of anterior disc displacement

without reduction.

On the other hand, utilization of US for detecting lateral

and posterior displacements was not suggested.

Overall, the diagnostic efficacy of

US in TMJ evaluation is acceptable

and can be used as a rapid

preliminary diagnostic method

Dr Sanjana Ravindra

Muscle disorders

Temporalis muscle is seen as a thin HYPOECHOGENIC BAND lying adjacent to the medial part of the temporalis fossa.

The bony landmark is identified as a HYPERDENSE LINE, whereas the course of the temporalis muscle is best visualized by having the patient clench.

The masseter muscle is seen as a HOMOGENEOUS structure lying adjacent to the ECHOGENIC BAND of the mandible.

The anterior digastric muscle corresponds to round HYPOECHOGENIC zones located lateral to the respective mylohyoidmuscles.

The posterior digastric muscle is seen as a HYPOECHOGENIC band located under the HOMOGENEOUSultrasonographic pattern of the parotid gland.

Sternocleidomastoid muscle is easily visualized due to its large size and typical band shape which shows a solid HYPOECHOGENIC ultrasonographic pattern. The medial boundary of the sternocleidomastoid muscle is identified as a very DENSE HYPERECHOGENIC LINE. Dr Sanjana Ravindra

US was found to be useful for the measurement of masseter muscle

thickness.

In the inflammatory muscle, the echogenic bands, which correspond to

the internal fascia or tendon of the muscle, are frequently diminished or

disappeared.

Muscle with histologically verified edema shows less echogenity compared to that

of muscle without edema .

Muscle disorders

Dr Sanjana Ravindra

MASSETER MUSCLE

HYPERTROPHY

Normal masseter muscle

Masseter hypertrophy

Dr Sanjana Ravindra

ORAL SUBMUCOUS FIBROSIS

Manjunath K Evaluation of oral submucous

fibrosis using ultrasonographic technique: a

new diagnostic tool.

Ultrasonographic unit with color Doppler and

9-5 MHz intra - cavitary convex transducer

used with water path

Glove finger filled with water served as

water path between transducer and oral

mucosa

Transducer with cellulose dextrose gel was

placed on water path and analyzed

• In normal individuals, ultrasonography

delineates normal mucosa with uniform fine

mottled appearance with interspersed

hypoechoic areas.

• Color Doppler and spectral Doppler depicts

uniform distribution of blood vessels

• Diffuse fibrotic patch (crossing dot

lines) and diminished vascularity in

an oral submucous fibrosis lesion

Dr Sanjana Ravindra

Soft tissue masses of the neck

Thyroglossal cysts and branchial cleft cysts are mostly encountered cervical cysts. Less frequently, cystic hygomas, dysontogenetic cysts, ranulas and laryngoceles are found.

On US examination, thyroglossal cysts most often appear anechoic with posterior acoustic enhancement.

Debris in cervical cysts can result in a hypoechoic, pseudosolid appearance. Although most of branchial cleft cysts are hypoechoic some of them are anechoic.

Ultrasonographically ranulas are smoothly marginated, anechoic or homogeneously hypoechoic lesions without internal color or power Doppler signals.

Palagatti et al found a diagnostic accuracy of 92.2% for US in the diagnosis of cystic lesions which is in line with the previous literature.

Dr Sanjana Ravindra

US is able to show hyperreflective

microbubbles of gas in supurative sialadenitis with adjacent reactive

nodes.

A study, found that most of the inflammatory

swellings had relatively clear boundaries,

hypoechoic intensity and homogeneous

ultrasound architecture of lesions.

Considering inflammatory swellings, us had a sensitivity of 97% and specificity of

100%, whereas; clinical diagnosis had a

sensitivity and specificity of 85.7%[57].

Us was found to have high sensitivity in the

diagnosis of inflammatory swellings of

the head and neck region.

Acute inflammation

Dr Sanjana Ravindra

Odontogenic tumor is hyperechogenic because of the uniformity of the tumor mass.

Odontogenic cystic lesions are unechogenic, because of their

liquid content.

Keratocystic odontogenic tumors are hypoechogenic, because of their dense and thick content[

Bone lesions

Dr Sanjana Ravindra

TEETH

Used in detection

of enamel, dentin

thickness

Ultrasonic Caries Detector (Novadent)

Dr Sanjana Ravindra

PERIAPICAL LESIONS

Cystic lesion: A hypoechoic well-contoured cavity surrounded by reinforced bone walls, filled with fluid, and with no evidence of internal vascularization on color Doppler examination.

Granuloma: A poorly defined hypoechoic area, showing rich vascular supply on color Doppler examination.

Dr Sanjana Ravindra

SPACE INFECTION

Normal submandibular regionAffected submandibular space

A.Sonogram of the submandibular space showing the spreading infection and the involvement of the

submandibular lymph nodes (arrowheads). The mixed hypoechoic and hyperechoic pattern indicates

the starting of abscess formation.

B, Sonogram of normal submandibular region for comparison with the infected side.

Dr Sanjana Ravindra

Salivary gland

SALIVARY GLANDS – PAROTID GLAND

& DUCT

1 parotid gland, 2 Stensen's duct, 4 masseter

muscle, 5 surface of the mandible, 6 buccal muscle,

large arrow retromandibular vein and external carotid

artery.

Axial ultrasound - normal right

submandibular gland showing its

relationship to adjacent structures. S,

submandibular gland; M, mylohyoid

muscle; H, hyoglossus muscle; White

arrow, intraglandular duct; D, posterior

belly of digastric muscle.

SUBMANDIBULAR GLAND

Dr Sanjana Ravindra

• SUBLINGUAL

GLAND

ACUTE INFLAMMATION

salivary glands are enlarged and

hypoechoic. There may be

inhomogeneous; multiple small,

oval, hypoechoic areas; and may

have increased blood flowDr Sanjana Ravindra

CHRONIC INFLAMMATION

SIALOLITHIASIS

US features of

sialolithiasis include

strongly hyperechoic

lines or points with

distal acoustic

shadowing, which

represent stonesDr Sanjana Ravindra

US features of advanced Sjogren

syndrome include inhomogeneous

structure of the gland with scattered

multiple small, oval, hypoechoic or

anechoic areas, usually well defined, and

increased parenchymal blood flow

SJOGREN SYNDROME

PLEOMORPHIC ADENOMA

Hypoechoic, well-defined,

lobulated tumors with posterior

acoustic enhancement and

may contain calcifications

WARTHINS TUMOR

well defined, hypoechoic, and

inhomogeneous with multiple irregular

anechoic areas (arrowheads) and

posterior acoustic enhancement. Dr Sanjana Ravindra

Oral cancer tumor thickness

In conclusion, US could be used as the primary imaging modality for the

assessment of tongue tumor thickness as it improved planning for

prophylactic neck dissection in early stage disease.

•Wakasugi-Sato et al developed a method in order to

allow operators to easily assess and confirm the surgical

clearance of tongue carcinomas intraoperatively using

intraoral US. Tumor thickness was reported as an

important prognostic factor in cancers of the oral cavity.

Authors demonstrated that there was a strong correlation

between tumor thickness measured from ultrasonic

images and histological sections.

•Yuen et al evaluated the correlation between ultrasonic

and pathologic tumor thickness. They found a statistically

significant correlation between pathologic and ultrasonic

thickness.

•Shintani et al measured tumor thickness of squamous

cell carcinoma and compared the clinical usefulness of

CT, MRI, and intraoral US to delineate the extent of

tumors. They showed that intraoral US is very accurate

and valuable for mapping these tumors.

•Yesuratnam et al compared preoperative tumor

thickness on high resolution intraoral US and MR

imaging with histologically determined tumor thickness.

They found high correlation between tumor thickness on

preoperative US and histological primary tumor thickness

and good correlation between MRI and histological

primary tumor thickness

Dr Sanjana Ravindra

Unsharp borders common

in Tuberculous nodes sharp borders in malignant

nodes

Calcification within lymph

nodes

LYMPH NODES

Normal, Reactive,

Lymphomatous & Tuberculous

nodes are predominantly

hypoechoic when compared

with the adjacent muscles.

Dr Sanjana Ravindra

VASCULAR PATTERN

Dr Sanjana Ravindra

New ultrasonic device including a soft tissue matched transducer with a

customized transreceiver and signal processing was capable of measuring soft tissue thickness over bone and implants placed in porcine models.

This was efficient as a diagnostic tool for intraoral measurements of the

inferior alveolar canal and floor of the maxillary sinus before dental implant

placement.

Authors measured the distance from the bottom of the osteotome to the inferior canal and maxillary sinus floor using a

novel ultrasonic device and conventional radiographs.

A significant positive correlation was observed between the radiographic and

us measurements.

Implantology

US has the potential to be an alternative diagnostic tool for implant dentistry

owing to its nonionizing nature

US may play an important role in locating submerged implants.

Dr Sanjana Ravindra

US has emerged as a noninvasive periodontal

assessment tool that yields real time

information regarding level, tissue thickness,

histological change, calculus and bone

morphology as well as tooth structure for fracture cracks.

Because of the small size of the probe and

its special design, patients felt that the oral US was a stress

free, painless and fast examination tool.

The periodontal width is directly accessible

and measurable. Besides, it offeres new

prospects for gum thickness evaluation, earlier detection of a

small anatomic change, and diagnosis of oral

mucosa lesions.

In contrast to the conventional methods

of transgingival probing witch is an invasive

method and may give false measurements because of the tissue edema which occur

due to injection of local anesthesia prior to the

procedure

Periodontal US

Dr Sanjana Ravindra

Another possible application of US studied is the visualization of

foreign bodies in soft tissues.

Among other imaging modalities, the best

sensitivity and specificity results were achieved by

using us

Visualization of the size and form of well-

shaped materials such as wood,

composite, amalgam and glass

Foreign bodies

Dr Sanjana Ravindra

US is an innovative and evolving imaging

technology with plenty of research continuing to be

done in medical field.

It is safe, rapid, portable and economic.

Further studies towards clinical applications of the

US in the dento-maxillofacial region are

essential in order to obtain information regarding

accurate and appropriate clinical usage of the system in dentistry[

CONCLUSION

Dr Sanjana Ravindra

REASON FOR CHOOSING THIS ARTICLE ?

Dr Sanjana Ravindra

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Dr Sanjana Ravindra

Dr Sanjana Ravindra