The role of diagnostic ultrasound as a new diagnostic aid in oral and maxillofacial surgery.

Only very few studies have been done in the past to evaluate the usefulness and limitations of ultrasonography in oral and maxillofacial surgery. This study, though in an embryonic stage, has been done to bring this technique to limelight and to put forth the importance of its use and limitations in the branch of oral surgery. The purpose of this study was to investigate and study the characteristic pattern of the oral tissues on gray scale ultrasonography and to assess the practical applicability of this new diagnostic technique in diagnosing various tissue pathologies in the field of oral and maxillofacial surgery.

Human ear can hear only a limited range of sound frequencies. This range is from 20 to 20,000 Hz beyond the audible range. There are sounds of varying pressure waves which we cannot hear. Those with frequencies below the audible range are referred to as infrasonic, whilst those with frequencies above the audible limit are known as ultrasonic.

The principles and application of ultrasound was discovered by Curie brothers in 1880. The Dussik brothers in Austria (1937) were the first to describe the use of ultrasound imaging, and later in 1972, Kossoff in Australia and others introduced gray scale ultrasonography. Thus, after a long gestation and childhood, diagnostic ultrasound is now reaching adolescence with a potential for considerable future growth.[1] Lawrence M. Vincent in 1988 stated that sonography is widely applicable in the diagnosis of a variety of soft tissue abnormalities. He carried out his studies in extremities’ soft tissue abnormalities including muscle hemorrhage and injury, inflammation, and neoplasm. Though the major application of diagnostic ultrasound is in cardiology, gastroenterology, obstetrics and gynecology, it is recently gaining importance in the diagnosis of oral and maxillofacial lesions.

In diagnostic ultrasound, piezoelectric effect is being used where the application of the electric field across the material causes that material to expand or to contract depending upon the way in which the field is applied, producing longitudinal oscillations in the surrounding medium. The pathological lesions undertaken for this study were soft tissue tumors, cysts, odontogenic abscess, and a case of postoperative third molar surgery after 48 h.

Materials and Methods

In the field of oral and maxillofacial region, 10 patients were selected in the age group 11–65 years. The patients were divided into three groups:

Patients who had bony lesions.

Patients who had salivary gland lesions with lymph node involvement.

Patients who had postoperative swelling 48 h after the removal of lower third molar.

Detailed clinical examinations were carried out for all the patients and entered in the chart. Routine radiographic, hematological, and histopathologic examinations were also carried out.

Equipments

The machine used in the study was ultramark 8 (UM8) ultrasound system having transducers of various frequencies (3.5 MHz, 5.0 MHz, 7.5 MHz, and 10.0 MHz).

Medigel-methylcellulose was used as the coupling agent between transducer and patient contact area.

Method

Scans were taken. Patients were turned toward the operator. Normal side was also scanned. Medigel-methyl cellulose was applied over the lesion as well as the transducer. Transverse and longitudinal sections were taken out. Necessary images were frozen and studied. With the attached camera, single coated films were taken. The procedure took about 5 minutes.

The total number of patients taken for study was 10 out of which 30% were females and 70% were males.

Two Cases of Cystic Lesions, One Each in Mandible and Maxilla (Case Reports 1 and 2)

In the case no. 1, [Figure 1a] scan revealed continuous hyperechoic line due to the thinned out outer cortex of mandible. Anechoic area with posterior wall enhancement confirmed the presence of cyst. A hyperechoic mass was seen within the sonolucent area. This might be due to any calcification. In this case, it was found to be an impacted tooth.

Figure 1

(a) Photograph showing swelling in the right angle of the mandible. (b) Transverse section showing sonolucent area with hyperechoic line of outer cortex of the mandible. (c) Longitudinal section of scan showing sonolucent area with hyperechoic focus within it with posterior wall enhancement

But in case no. 2, [Figure 1b–c] internal echoes were seen with enhancement of posterior wall echo. These internal echoes were due to the presence of superimposed infection or hemorrhage in the cyst.

Two Cases of Salivary Gland Pathology with Nodal Involvement (Case Reports 3 and 4)

In case no. 3 [Figure 2a] who had a hard swelling in the left parotid region for duration of 6 years, the scan [Figure 2b] revealed heterogeneous areas suggestive of mixed lesion. Enlarged lymph nodes of size 1.4×1.4 cm (hypoechogenic than the surrounding tissue) were seen in the submandibular region. Submental lymph nodes were visualized as hypoechoic area as seen in [Figure 2c]. The impression was that of tumor in the left parotid gland with node involvement. Biopsy was suggestive of pleomorphic adenoma. Fine needle aspiration biopsy (FNAC) was suggestive of salivary gland neoplasm.

Figure 2

(a) Photograph showing swelling in the left parotid region extending to right submandibular region. (b) Scan showing normal homogenous echopattern of the right parotid. (c) Scan showing heterogeneous echo pattern with small hypoechoicareas of the left parotid region

In case 4, there were anechoic areas within heterogeneous echoes. Anechoic areas were suggestive of cystic lesion. Presence of continuous hyperechoic line with posterior acoustic shadow was suggestive of intact mandible. Lymph node was visualized in the left submandibular region.

These two cases of pleomorphic adenoma of parotid gland showed heterogeneous pattern with both solid and cystic areas.

A Case of Postoperative Swelling (Case Report 5)

The patient [Figure 3a] was taken for study 48 h after the removal of lower third molar. There was a slight diffuse tender swelling on clinical examination.

Figure 3

(a) Photograph showing diffuse swelling in the left side of the face. (b) Scan showing increased width and hypoechoic pattern of left subcutaneous tissue

The scan of this patient [Figure 3b] showed that right and left (operated) masseters were of the same width (1.24 cm), but an increase in the width of subcutaneous tissue was noticed on the left side with hypoechoic areas [Figure 3c] suggestive of subcutaneous edema.

Two Cases of Ameloblastoma (Case Reports 6 and 7)

In case 6, the scan revealed that the lesion was large with irregular boundaries. Heterogeneous echo pattern with anechoic areas was seen within the lesion. Bony contour could not be imaged and could be correlated with X-ray which showed erosion of lower border and posterior border of the mandible.

In case 7, presence of hyperechoic line was suggestive of outer cortex of mandible and the lesion was confirmed to be within the mandible. Internal echoes were seen, which might be due to cystic degeneration within the lesion or superadded infection. This was correlated with aspiration by which yellowish brown colored material was obtained.

Case Report 8

Sonogram confirmed the presence of the lesion within the mandible. The lesion with 3×2.9 cm dimension had cystic areas with intermediate posterior wall enhancement. Heterogeneous echoes were seen and might be due to blood or fluid.

Case Report 9

The scan revealed the size of lesion to be 3.5×3.5 cm, which was compatible with that of clinical examination. The lesion was a solid one with heterogeneous echoes. There was hyperechoic area with posterior acoustic shadow suggestive of calcification. The histopathologic study reported it as central giant cell tumor.

Case Report 10

The size of the mass was measured to be 4.3×4.2 cm. Two areas of cystic nature (anechoic) of 1×1 cm were seen indicating degeneration within the mass. The involvement of bone, either maxilla or mandible, could be ruled out by this scan which showed continuous hyperechoic lines. Left submandibular and deep cervical nodes were visualized by hyperechoic pattern.

Discussion

The following ultrasonic parameters were used in the diagnosis of the lesion:

Ultrasound pattern – solid or cystic

Boundary echo – smooth or irregular

Internal echo – homogenous or heterogeneous

Posterior wall echoes – enhanced, intermediate, attenuated.

If there is thinning out of cortical plate of bone due to expansion and resorption, there is propagation of ultrasound waves and echoes are reflected, thus producing ultrasonography patterns.

Only enlarged lymph nodes are sonographically visible[2] because these round or oval masses are globally hypoechogenic relative to the surrounding tissues. And for the measurement of node size, transverse diameter is more helpful than longitudinal diameter. Most but not all of the inflammatory nodes are smaller than 8 mm in diameter.[3]

Willey and others in 1975 stressed the value of ultrasound in providing a more accurate means of quantifying lymph node size and volume and in evaluating its extension.

Nishino[4] in 1988 examined 73 cases of swollen lymph nodes, 52 cases of acute or chronic lymphadenitis accompanying sialoadenitis, and 18 cases of metastatic lymphadenopathy. He reported that maximum diameter and longitudinal/transverse ratio are most useful in the differential diagnosis and that the borders, internal echoes, and posterior wall echo enhancement are next in usefulness. Based on this, six cases of various bony lesions have been taken for the study. Out of these six cases, three were cystic in nature. The study proved to be of value and results were encouraging. In the remaining three cases, gray scale ultrasonography helped to substantiate clinical findings such as site, size, and internal structure. Real-time scanning being a new diagnostic tool for assessing various pathological lesions can be much useful in detecting salivary gland pathology.

Conclusions

In the field of oral and maxillofacial region, 10 patients were selected in the age group 11–65 years. The patients were divided into three groups. The procedure was carried out with the patients in supine position, using either 7.5 MHz or 10.0 MHz frequency transducers. The value of diagnostic ultrasound in the study of internal topography of various facial tissues and its use for assessing various pathological lesions was proved to be useful.

Christensens[5] and others in 1988 found out that ultrasonography is a valuable tool for guiding intervention in the musculoskeletal system.

Gray scale ultrasonography,[6] a new diagnostic aid which is painless, non-invasive, rapid, relatively inexpensive, and easily reproducible, can be used for the assessment of various masses of oral and maxillofacial and neck regions.

Currently, ultrasound-guided biopsy or FNAC is of value in decreasing false-negative results, since solid and cystic areas can be localized by the scan. Ultrasound-guided biopsy or aspiration will have a greater diagnostic aid and specificity.[78] Also, evaluation of lesion using Doppler and color Doppler techniques may yield information about the vascular and blood flow pattern within the lesion.