|Year : 2021 | Volume
| Issue : 2 | Page : 55-61
Diagnostic value of ultrasonography in maxillofacial practice: A narrative review
George Ewansiha1, Anas Ismail2, Mohammed Kabir Saleh2, Adeola Ladeji3, Babatunde Olamide Bamgbose4, Jun-ichi Asaumi5, Abdulmannan Yahya6
1 Department of Oral Diagnostic Sciences, Aminu Kano Teaching Hospital, Kano, Nigeria
2 Department of Radiology, Faculty of Clinical Sciences, Bayero University Kano, Kano, Nigeria
3 Department of Oral Pathology and Oral Medicine, Lagos State University College of Medicine, Ikeja, Lagos, Nigeria
4 Department of Oral Diagnostic Sciences, Aminu Kano Teaching Hospital, Kano; Department of Oral Diagnostic Sciences, Faculty of Dentistry, Bayero University Kano, Kano; Department of Oral and Maxillofacial Radiology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Nigeria
5 Department of Oral and Maxillofacial Radiology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama; Department of Oral Diagnosis and Dentomaxillofacial Radiology, Okayama University Hospital, Okayama, Nigeria
6 Department of Child Dental Health, Bayero University/Aminu Kano Teaching Hospital, Kano, Nigeria
|Date of Submission||04-Sep-2020|
|Date of Decision||07-Mar-2021|
|Date of Acceptance||20-Apr-2021|
|Date of Web Publication||10-Dec-2021|
Prof. Babatunde Olamide Bamgbose
Department of Oral Diagnostic Sciences, Bayero University Kano, Kano
Source of Support: None, Conflict of Interest: None
Ultrasonography or sonography is a rapidly evolving imaging technology, which uses high-frequency sound waves that are transmitted into the body and echoes from the tissue interfaces are detected and displayed on a monitor. In recent years, its application in maxillofacial practice has gained importance as a diagnostic tool. Therefore, the aim of this manuscript is to review the literature for narrative assessment of the diagnostic value of ultrasound in maxillofacial practice and to compare the significance of ultrasound to other diagnostic modalities. The PubMed CENTRAL, MEDLINE, Springerlink and Cochrane library databases were searched using the MeSH terms subject headings: Ultrasonography, maxillofacial practice, maxillofacial sonography, echogenicity, physics of ultrasonography, diagnostic ultrasonography, greyscale, Doppler and maxillofacial imaging. The search was restricted to free-full text and articles written in the English language published from 1989 to 2018. A total number of 36 articles retrieved were reviewed by the authors restricted to review paper, original research and case report which described the diagnostic modality of US in maxillofacial practice. US have become one of the valuable diagnostic imaging modalities in maxillofacial practice owing to its affordability, availability and safety to tissues as it employs non-ionising radiation.
Keywords: Doppler, greyscale, maxillofacial imaging, ultrasonography
|How to cite this article:|
Ewansiha G, Ismail A, Saleh MK, Ladeji A, Bamgbose BO, Asaumi Ji, Yahya A. Diagnostic value of ultrasonography in maxillofacial practice: A narrative review. Niger J Basic Clin Sci 2021;18:55-61
|How to cite this URL:|
Ewansiha G, Ismail A, Saleh MK, Ladeji A, Bamgbose BO, Asaumi Ji, Yahya A. Diagnostic value of ultrasonography in maxillofacial practice: A narrative review. Niger J Basic Clin Sci [serial online] 2021 [cited 2022 May 24];18:55-61. Available from: https://www.njbcs.net/text.asp?2021/18/2/55/332186
| Introduction|| |
Ultrasonography (US) has been added to the list of imaging modalities, including conventional radiography, computed tomography (CT), panoramic radiography, magnetic resonance imaging (MRI) and more advanced techniques such as nuclear medicine and positron-emission tomography, for evaluating maxillofacial pathosis and anomalies. Ultrasound and MRI use non-ionising radiation and are popular in maxillofacial practice. They can be used for examination of pathological lesions such as subcutaneous abscesses, inflammatory mass overlying the thyroid, obstructing calculus in the salivary gland, diffuse parotitis, Sjogren syndrome, tumours within the parotid gland and submandibular region, cervical cysts and metastatic lymph nodes. Ultrasonography as an imaging modality in maxillofacial practice is popular due to its relative low cost, availability, non-invasive nature, lack of radiation hazards, reproducibility and 'real time' imaging with cross-sectional capabilities.,, Its drawbacks include operator-dependence, limitation with respect to its field of view and difficulty in viewing structures behind bone and air. US can serve an alternative modality where MRI is contraindicated in patient with condition such as cardiac pacemakers, metallic dental restoration, cochlear implants and metallic prostheses. The principles and applications of ultrasound were first discovered by the Curie brothers in 1880, and in 1937, the Dussik brothers described the use of ultrasonographic imaging. However, sonography was introduced into the medical field in the 1950s, and with improved development, it has become one of the commonly used diagnostic tools.,,, The term ultrasound refers to acoustic waves of frequency >20 KHz which is inaudible to the human ear. Medical ultrasound uses frequency between 1 and 20 MHz, but in practice, high frequency pulse of acoustic wave of 2.5–18 MHz are utilised.,
| Basic Principles of Ultrasound Imaging|| |
Sound is produced by a mechanical vibration that transmits energy through a medium. When transmitted, it causes the molecules to oscillate during the wave propagation. Ultrasound is a high-frequency sound wave which transmits a longitudinal pressure wave made of zone of compression (high density of molecule) followed by zone of rarefaction (low density molecule). If the force oscillates continuously, alternating zones of compression and rarefaction are propagated through the material. This establishes a wave-front of disturbance in the material, known as a longitudinal wave.,
In diagnostic ultrasound imaging, high-frequency sound wave is transmitted into the body via a transducer which converts electrical energy into mechanical vibration. At the same time, it also receives transmitted echoes from the tissue interfaces, which in turn are converted to electric signals for display on the computer screen., The ultrasound transducer consists of one or more piezoelectric crystals which are based on the principle that quartz is subject to a change in shape when placed within an electrical field. The main component of the transducer is a thin piezoelectric crystal. Currently, the most widely used piezoelectric material is lead zirconate titanate.,, In medical ultrasound imaging, the resolution of the image depends on the magnitude of the frequency. The higher the frequency produced, the better the image resolution. Basically, two modes of US are employed for acquiring information namely: the greyscale and the Doppler imaging. Greyscale mode consists of A-Mode, B-Mode and M-Mode. A-Mode is the simplest form of US mode representing echo amplitude hence the term A-mode. It is used for measuring boundaries of tissue of different acoustic properties. It is rarely used nowadays. B-mode or brightness mode produces different echogenicity of reflected waves which are displayed in two-dimensional (2D) image and show tissue borders as black and white image. Images may be displayed as static or real-time. M-mode is a 2D image that allows recording the motion. It has an excellent temporal resolution.,, The D-mode is based on the 'Doppler effect' used to assess the velocity of blood flow through the blood vessels. Different techniques are applicable in Doppler imaging: continuous wave Doppler, duplex Doppler, power Doppler, pulsed wave Doppler and colour Doppler.
The aim of this article was to review the available literature on the diagnostic value of ultrasonography in maxillofacial practice.
| Materials and Methods|| |
The review was based on the available English literature from electronic databases via PubMed CENTRAL, MEDLINE, SpringerLink and Cochrane library databases and Google Scholar with articles published from 1989 to 2018. The search strategy included keywords such as 'maxillo-facial sonography', 'physics of ultrasonography', 'sialolithiasis', 'diagnostic ultrasonography,' 'greyscale' and 'Doppler and maxilla-facial imaging'; using the 'AND' Boolean logical operator. A total number of 2400 of articles were retrieved. All articles discussing ultrasonographic or sonographic application in maxillofacial practice were included in the study. Studies on therapeutic application of ultrasound in maxillofacial lesions were excluded. A hand search of literature was also done in textbook to add to the electronic search results.
Inclusion and exclusion criteria
The inclusion criteria were:
- Studies evaluating the use of ultrasonography in the diagnosis of maxillofacial lesions irrespective of demography
- Article type from review, case report and original research were inclusive
- Accuracy and sensitivity of US compared to other diagnostic tools was included
- Articles written English language only.
The exclusion criteria were given as follow:
- Studies on therapeutic application of ultrasonography in maxilla-facial practice
- Article type being editorial, letter to the editor and commentary were excluded.
| Results|| |
A total of 2400 articles identified through four literature databases (PubMed Central 2321, MEDLINE 18, Springerlink 59 and Cochrane library 2) with an additional 14 article identified through other source (Google Scholar). Only 36 papers met the inclusion and exclusion criteria and were included in the study. The PRISMA flow chart [Figure 1] shows the decision-making process in the selection of articles.
The characteristics of the selected papers comprised of 11 reviews, 21 original articles and 3 case reports which is represented in [Table 1].
| Accuracy of Ultrasound Relative to Other Diagnostic Modalities|| |
US has routinely served as an efficient tool for diagnosis of various orofacial lesions with a high accuracy when compared to other diagnostic modalities.,, According to Zope et al. and Garg et al., there is significant association, with an overall correlation between US diagnosis and histopathological diagnosis in oro-facial swellings. These correlations were reliable, except in case of benign odontogenic tumour. Thus, US is employed as a valuable modality along with clinical and histopathological examination in the diagnosis of oro-facial swellings. Puri et al. found 100% accuracy of US as a diagnostic aid in cystic lesions, 80% for benign lesions and 85.71% for malignant lesions. They concluded that US is a reliable diagnostic modality that can be used with greatest accuracy with cystic lesions, whereas in benign and malignant lesions, it could serve as an adjunctive investigation.
| Diagnostic Applications of Ultrasound in Maxillofacial Practice|| |
The value of US as an effective diagnostic aid in maxillo-facial practice is widely documented.,, Recently, US is gaining recognition either as a first line of investigation for provisional diagnosis or for the provision of differential diagnosis because of its relative economic cost and ability to provide an accurate information on lesions of the jaws before surgical intervention., In view of the complex anatomy of the head and neck, lesions behind bone and suspected malignant lesions with possible infiltration of deeper structures are better evaluated by the use of CT and MRI imaging techniques. Ultrasound imaging applications are useful for the assessment of salivary gland pathology, swelling of the orofacial region, cervical lymphadenopathy, temporomandibular joint disorders, congenital vascular lesion of the head and neck, detection of foreign bodies (FBs) and primary lesion of the tongue.,,,, Other application includes US-guided-fine needle biopsy (USG-FNAB), implantology and oral submucous fibrosis.,
| Assessment of Inflammatory and Neoplastic Salivary Gland Lesions|| |
Salivary gland diseases range from inflammatory, systemic, cystic, obstructive or neoplastic lesions and can be clearly detected and differentiated with US examination. Salivary gland ultrasound (SGUS) has been successfully employed in salivary gland lesions to confirm the presence of mass, differentiate between intra- and extra-glandular lesions, and suggest the nature of neoplasm. Sonographic examination of the salivary gland examination is best performed using linear-array broad band transducer with a frequency of 7–12 MHz, which is usually selected depending on the depth of the lesion. The normal structure of salivary gland has a medium greyscale homogenous echo pattern and the level of echogenicity is higher than that of surrounding parenchyma., In acute inflammation, the salivary gland is usually characterised by enlargement and decrease in parenchymal echotexture. Doppler assessment may show increase in blood flow. In organised abscess, it may be surrounded by a hyperechoic 'halo.' Normal sized or smaller hypoechoic and inhomogeneous ultrasound architecture are usually noticed in chronic inflammation without increased blood flow, and border tends to be regular with specks of calcification. Occasionally, acute sialadenitis may show multiple small round or oval hypoechoic area distributed throughout the parenchyma. The differential diagnosis in such cases may include sarcoidosis and other granulomatous conditions, Sjögren syndrome, disseminated lymphoma, hematogeneous metastases and benign lymphoepithelial lesions in HIV-positive patient.
Pleomorphic adenoma is one of the common benign lesions of the salivary glands. It appears as a well-defined, homogeneous, hypoechoic mass with posterior acoustic enhancement, whereas, most malignant lesions depending on the histologic grade are ill-defined, hypoechoic with heterogeneous internal architecture and associated enlarged lymph nodes which are recognised by round shape heterogeneity, loss of hilar architecture, abnormal disorganised vascularity, cystic changes and extracapsular spread., Although, the sonographic appearance of benign and malignant salivary glands lesions are often similar, several sonographic features such as heterogeneous echotexture, indistinctive margins, regional lymph node enlargement and the absence of posterior acoustic enhancement have been reported to be more frequently associated with malignancy.,, On colour Doppler the benign lesion showed absent or poor vascularisation while the malignant lesions usually show a central hypervascularity.
| Sialolithiasis|| |
About 80% of salivary calculi are found within the submandibular glands, 6% are in the parotid glands, and rarely seen in sublingual or minor salivary glands., They are characterised by transient episodes of pain and swelling of the involved salivary gland during mealtime. It is often accompanied by dry mouth, halitosis and bad taste. Sialolith is an organised pale-yellow material. The exact aetiology is unknown but contributing factors may include saliva stagnation, tobacco smoking, use of diuretics, hyperparathyroidism and duct inflammation/obstruction or injury.,, Although, calculi are usually solitary, multiple cases are not uncommon. US are the first imaging modality employed due to its non-invasiveness, relatively low cost and availability in most centres. Terraz et al. reported 77% for detection of sialoliths. Calculi with diameter >3 mm were correctly diagnosed onsonography, but the sensitivity decreased with calculi with diameter <3 mm. The size of calculi may be a determining factor for the performance of US to detect calculi. Gritzmann et al. reported intraglandular stone larger than 2 mm were easily detected with posterior acoustic shadowing, but these shadows were absent or poorly visualised in small calculi. Typical US features of salivary calculi showed markedly hyperechoic lines or points with distal acoustic shadowing. In symptomatic cases with duct obstruction, dilated excretory ducts are visible. In 50% of case sialolithiasis coexist with inflammation. Hyperechoic bubbles of air mixed with saliva may mimic stone in the Wharton's duct.,,
| Autoimmune Diseases of the Salivary Glands|| |
Sjögren's syndrome is a slowly progressive, chronic autoimmune disorder of the exocrine glands which predominately affect women over 40 years of age, characterised by intense periductal infiltration by lymphocytes and plasma cells, causing destruction of salivary and lacrimal glands. In recent years, SGUS has been explored as a diagnostic tool for detection of Sjögren's syndrome., US features of Sjögren's syndrome includes an oval-shaped, well-defined boundary with scattered multiple small foci of hypoechoic intensity, inhomogeneous structure of the gland usually with increased parenchymal blood flow. In a comparative study of US with MRI and MR sialography to examine salivary glands in primary Sjögren syndrome, the sensitivity of MR sialography (96%), MRI (81%) and US (78%) were compared, but US showed a specificity of 94%and accuracy of 85%.,,, The addition of SGUS notably improves diagnosis of Sjögren's syndrome with increased sensitivity of 87%.
| Assessment of Oro-Facial Infection|| |
Odontogenic infections arising from decayed tooth or periodontal lesions can extend beyond the alveolar bone to involve the various potential spaces of the head and neck. Infection tends to spread through the connective tissues and along the fascial plane following the path of least resistance, causing considerable morbidity and mortality. At times, it is difficult to make a diagnosis on the stage of infection and to define its exact anatomical location based on clinical and conventional plain radiographic examination because of the complex anatomy of the maxilla-facial region and given the fact that plain radiograph does not provide a good definition of soft tissue imaging. In such cases, cross-sectional imaging modalities like CT scan and MRI can greatly aid in the location of infection, while US can be used as a reliable adjunctive imaging modality to depict the different stages of fascial space infection of odontogenic origin. Although, greyscale US alone cannot differentiate between abscess and surrounding blood vessel, but combination of colour Doppler with greyscale US has allowed for easy differentiation of an abscess cavity from flow of blood in vessels., Hence, to evaluate the efficacy of US in the diagnosis of fascial space infection of odontogenic origin, Shah et al. and Sharma et al. both reported the same consistency with a sensitivity of 100% and a high significant positive correlation when clinical working diagnosis is comparable with US.
| Sonographic Assessment of Cysts, Neoplasm, and Intraosseous Lesion of the Jaw|| |
The jaw is the most common site for either odontogenic or non-odontogenic lesions with heterogeneous group of cystic, neoplastic and intraosseous lesions. The use of US as a complementary examination to CT scan and MRI is important in evaluating solid and cystic lesions of the jaw., Although, US does not establish final diagnosis it will facilitate differentiation between solid and cystic lesions. US have limited use in intraosseous lesions due to bone overlying the lesion. However, bony lesion which causes cortical expansion and consequent thinning of the cortical plate allows the passage of ultrasonographic signal.,, The overall diagnostic accuracy and sensitivity of US for cystic lesions was found to be 100%, as documented by Puri et al. and Akinbami et al., respectively.
Cystic swellings on sonogram typically appear anechoic due to fluid-filled nature, clear boundary with homogeneous echogenic architecture which creates enhanced transmission at the distal aspect of the cystic mass. If they become infected the lesion can produce some echoes within the hypoechoic area.,, Odontogenic cyst usually appears anechoic because of their fluid-filled content. The odontogenic keratocyst exhibits hypoechoic pattern because of the dense cystic content which contain keratins., Dentigerous cyst is anaechoic to focal hyperechoic, with area of the hyperechoic pattern representing the tooth portion exhibiting posterior acoustic shadowing. Residual cyst is noted to be well-defined hypoechoic lesion. Furthermore ameloblastoma is noted to show hyperechoic to anechoic internal echo pattern and in some case only hyperechoic pattern is demonstrated because of the uniformity of the tumour mass., Malignant tumours show characteristic complex echo texture with heterogeneous internal echopattern and irregular boundaries.
| Primary Tumours of the Tongue|| |
Sonographic features of tongue demonstrated by intraoral ultrasound (IOUS) are useful imaging modality to estimate accurate tumour size and thickness particularly in case of carcinoma of the tongue. Tumour thickness (TT) is considered as an objective parameter to estimate the depth of invasion within connective tissue, to predict the subsequent lymph node metastasis and to define adequate resection margins.,, The accuracy of tongue TT could be measured within 1 mm thickness with IOUS, but discussion remains as to which cut-off point is optimal. TT is an important parameter for predicting nodal metastases and for survival, and study done by Nair et al. showed that the incidence of occult nodal metastases was zero when TT cut-off was <4 mm and TT of 4 mm and above was predictor of occult cervical lymph node metastasis. However, IOUS should be an added protocol for measuring TT and not to replace MRI, CT and 'gold standard' histopathology evaluation.
| Evaluation of Foreign Bodies|| |
Most common encountered FBs in maxillofacial region are materials from splinter of wood, fishbone, tooth fragment, tuft of brushes, dental materials and metals. These objects may get lodge in soft tissue, sinuses or between bone and muscles. Although, conventional plain radiograph is the preferred initial workup, but several types of FBs are non-radiopaque and therefore remain undetected. Unlike, US maybe the prefer imaging method for the detection of superficial (as deep as 3 cm) non-opaque FBs like wood and plastic, and also for the accurate localisation of the soft-tissue FBs. High frequency acoustic wave may be more accurate than low frequency. However, it is not efficient for the detection of FBs in air-filled cavities such as the maxillary sinuses or at bone/soft-tissue interface (as in the body of mandible).,
Aras et al. documented a diagnostic sensitivity of 95% of US for the detection of localised superficial FBs with low radiopacity in the tissue of the body.
| Assessment of Cervical Lymph Nodes|| |
Cervical lymphadenopathy frequently arises from various causes including infection, malignant neoplasm, benign hyperplasia, distant metastasis and to non-specific lesions. Critical assessment of nodal status in patient with cervical lymph nodes pathosis like lymphoma or reactive lymph node is essential as it aid to predict prognosis and in the selection of appropriate treatment options. Clinical examination is valuable in cervical lymph nodes lesion but unreliable owing to the diverse location of cervical lymph nodes, their multiple numbers and as occult neck disease can occur in up to 50% of the patients. Hence, US has been showed to have a higher sensitivity (96.8%) than clinical examination (73.3%) for the detection of cervical lymph nodes.,,,
| Conclusion|| |
Ultrasonography is gaining relevance in oral and maxillofacial practice, serving as a first–line diagnostic imaging method as well as for follow-up of many lesions. It has relatively high sensitivity, specificity and accuracy.
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Conflicts of interest
There are no conflicts of interest.
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