Prevalence of soft tissue calcifications in cone beam computed tomography images in the region of head and neck

Objective: to evaluate the prevalence of calcifications in the soft tissues of the cervical-facial region using cone beam computed tomography (CBCT) images. Material and Methods: two hundred and ten CBCT exames was analyzed by 01 examiner previously trained, with fild of view (FOV) of 16 x 13 cm and voxel of 0.25 mm, in ICAT Vision software (Imaging Science International, Hatfield, PA, USA) in coronal, axial and sagittal sections. The following calcifications were evaluated: tonsiloliths, sialolites, calcification of the styloid complex, calcified carotid atheromas, calcifications in laryngeal cartilages, calcified lymph nodes and osteoma cutis. The findings were tabulated according to the total of the sample, related to the gender, age group of the individuals. Results: Calcification of the styloid complex was the most frequent in the sample studied in both genres (39.04%), followed by the presence of tonsiloliths (19.52%), and calcified lymph nodes (6,67%). Conclusion: calcifications are frequent radiographic findings in CBCT and important for the diagnosis of some possible pathologies that do not present clinical symptoms. RESUMO


INTRODUCTION
C alcification is a biochemical phenomenon, characterized by the deposition of calcium salts, mainly calcium phosphate, in a certain region of the organism [1][2][3]. However, when it occurs disorganized in soft tissues, it is referred to as heterotopic calcification, which can be divided into three: dystrophic, idiopathic and metastatic [1,2].
Soft tissue calcifications in the head and neck region are usually incidental radiographic findings and with the advent of concomitant Cone BeamComputed Tomography (CBCT), they are more frequently encountered, since it consists of a diagnostic imaging method which allows the visualization of structures in three planes, accurately identifying and becoming an indication for diagnosis [4][5][6].
The analysis of CBCT location requires knowledge of the soft tissue anatomy involved, such as the position of lymph nodes, styloid ligaments, blood vessels, cartilages of the larynx and major ducts of the salivary glands. Important points should be considered in order to arrive at a correct interpretation such as the anatomical location, the number, the distribution and the shape of the calcifications. Some soft tissue calcifications do not require any intervention or long-term follow-up, while others may pose a threat to life and their main cause must be treated. [7][8][9].
In this context, the present study aimed to evaluate the prevalence of the following calcifications in soft tissues, tonsiloliths, sialolites, calcification of the styloid complex, calcified carotid atheromas, calcifications in laryngeal cartilages, osteoma cutis and calcified lymph nodes, using cone beam computed tomography (CBCT) images. The inclusion criteria were: (I) both age groups and genders; (II) presented good image quality; acquired with the FOV (field of view) of 16x13 cm and voxel of 0.25 mm, which in this way registered the middle and lower 1/3 of the face, mandible and upper cervical portion. Exclusion criteria were: (I) the tests that did not present the FOV described in the inclusion criteria or that presented poor image quality (presence of patient movement artifacts); (II) the presence of fractures, surgical interventions such as orthognathic surgeries and neoplasias that affect maxillofacial structures. The CBTC images wasanalyzed in the i-CAT Vision software, belonging to the tomographic acquisition system and evaluated in the MPR (multiplanar reconstruction) screen, which simultaneously displays the coronal, axial and sagittal sections of the region.

MATERIAL AND METHODS
The evaluator, duly trained in the analysis and manipulation of the software, had free access to the system tools such as alteration of brightness, contrast, application of filters, zoom tool, to aid in image quality and diagnosis.The analysis of the images obeyed the protocol (Table I).

Calcification Hyohydoid Complex
Evaluated in the coronal and sagittal MPR, taking into account that the styloid process above 3.0 cm in length (measured in said windows, with the tool "distance"). Considering the possible presence of calcification during the course of the style-hyoid and mandibular ligaments, which considered as segmented calcifications ( Figure 1).

Tonsillolith
Examined in axial and coronal sections and were considered as hyperdense images, irregular and precise borders, located in the parapharyngeal regions.

Sialoliths
Three anatomical planes were evaluated, analyzing the presence of irregular hyperdensities in the submandibular, sublingual and parotid regions.

Calcified carotid artery atheroma
Calcification was considered presence of hyperdensal images in the carotid regions, observed in axial sections, corresponding to the C3-C4 pre-vertebral region ( Figure 2).

Calcified lymph nodes
Axial and coronal sections were evaluated, where the presence of irregular, hyperdense, lobulated images (described as cauliflower) corresponding to the cervical and submandibular regions was considered. sialoliths, with the criterion of presence of lobular aspect as a determinant of calcified lymph node (Figure 3).

Calcifications in the laryngeal cartilages
Hyperdensities were observed in the regions corresponding to the laryngeal cartilages, that is, in the anterior region the upper pharyngeal air space and close to the major horn of the hyoid bone

Osteoma cutis
Multiple punctiform calcifications in the regions corresponding to facial subcutaneous tissue.
For statistical purposes, data were analyzed and all the findings were tabulated, taking into account the incidence side, gender, age group of individuals and types of dystrophic, idiopathic and metastatic calcification, being submitted to descriptive statistics.

RESULTS
Observed that of the 210 analyzed samples, 144 examinations (68.57%) presented soft tissue calcifications ( Figure  4). When analyzing the prevalence among the three classifications of calcifications, it was observed that the metastatic calcification presented the highest prevalence, followed by the dystrophic calcification and the idiopathic calcification.
Considering the total sample, 131 were female patients (62.38%) and 79 male patients (37.62%). The most frequent types of calcifications analyzed by gender were the hyoid-style complex and the presence of tonsiloliths (Table II).
When checking the frequency between calcifications, the following results on table III. The age group that presented the most calcification was 31 to 50 years of age.
Being that the age group from 51 to 70 years of age obtained the greatest presence of carotid artery calcifications (Table IV).
In this study, no cases of calcification were found in the laryngeal cartilage and calcinosis cutis.

DISCUSSION
Soft tissue calcifications are incidental and sometimes frequent radiographic findings in CBCT exams [4,6,7], and there is a consensus in the literature about the accuracy and the ability to detect small cranial soft tissue structures [4,6,8].
Therefore, due to the prevalence of these calcifications, it is important to emphasize and recognize these changes more assertively [2,5,10]. However, the great advantage of the CBCT becomes its greatest challenge, because the images are three-dimensional, due to the lack of training of professionals in the area of dentistry for its correct interpretation, errors can occur due to the non-recognition of lesions or pathologies.In this study, the evaluator was trained to verify the prevalence of soft tissue calcifications, which were present in routine patients, who obtained the CBCT examination.
The highest frequency occurred in metastatic calcifications of the stylohyoid complex [2,9,11,12]. Metastatic calcifications occur due to the increase of levels of calcium ions in the blood stream, which may result from the removal of these ions from bones, common in situations of hyperparathyroidism, hypervitaminosis D or bone inflammations and due to the excess of these ions in the diet [7,8]. Frequency was also present in both genders and in the age group from 31 to 50 years.   The second most prevalent calcification in this sample, dystrophic calcification, showed a higher amount of tonsiloliths, followed by lymph nodes and carotid atheroma, according to other studies [9,11]. Dystrophic calcifications occur when there is insufficient blood supply and necrotic and ischemic tissues are present, although serum calcium and phosphate levels are normal [4,6].
In the detection of carotid atheroma, some authors agree that the major importance of this diagnosis is to avoid the occurrence of a stroke [10,13,14]. Calcified carotid atheromas were present in 4.76% of the total sample, in the age range of 51 to 70 years. These changes require treatment, and since the calcification of the carotid artery is silent, it may be reported after a routine examination. It is important to evaluate other signs and symptoms to confirm the diagnosis, and it is necessary to differentiate the atheroma of the carotid artery from calcifications, such as thyroid cartilage, calcified lymph nodes, sialolites and phlebolites [15][16][17].
The type of calcification that presented the third highest incidence was idiopathic. Idiopathic calcifications, although the individual presents normal levels of blood calcium, there is deposition of calcium in healthy tissues [4]. Sialoliths were present in 0.47% of the sample, the incidence was not significant, however according to other studies [10], these mostly occur [18][19][20]. The age group with the highest prevalence of sialoliths was 31 to 50 years. These calcifications can present pain, also need treatment. Sometimes other types of complementary tests may be needed. Already osteoma cutis, this is a rare benign condition in which soft tissue calcifications occur in the dermis layer of the skin [21], and were not detected in this study.

CONCLUSION
Soft tissue calcifications presented expressive prevalence in the studied sample. The calcification of the metastatic type (calcification of the styloid complex) showed the highest prevalence in the analysed sample. Some calcifications do not need treatment; however, the professional dental surgeon should be alert and check the routine exams to detect such calcifications.