Imaging characteristics of incidentally detected cosmetic surgery-derived foreign bodies on CT images in the maxillofacial region

Various materials are used in cosmetic surgery, and it is challenging to maintain extensive knowledge about them. In dentistry, surgical orthodontic treatments (e.g., osteotomy and otoplasty) for jaw deformities and dysarthria often produce significant esthetic improvements, as well as improvements in oral function [1, 2]. These treatments are regarded as dental care; thus, they are very familiar to dentists. However, cosmetic surgery performed as medical treatment is less familiar to dentists, and they may have difficulty diagnosing the underlying problem. Furthermore, patients tend to withhold details of such procedures; they are unlikely to self-report a history of cosmetic surgery during an initial dental examination. Occasionally, cosmetic materials become a source of infection; subjective symptoms (e.g., swelling and pain at the surgical site) may be observed, and imaging studies may reveal that cosmetic surgery was performed in the same area. Although there have been sporadic reports of these foreign body granulomas [3‐6], dentists generally have minimal experience with cosmetic surgery-derived foreign bodies; these foreign bodies are not fully understood, despite their potential impact on detection of the main lesion.

Therefore, clinicians engaged in imaging interpretation should understand the types of cosmetic surgery-derived foreign bodies that they may encounter when analyzing images of the maxillofacial region, as well as the imaging characteristics of such foreign bodies. This study examined the imaging characteristics of cosmetic surgery-derived foreign bodies in the maxillofacial region through a retrospective review of cosmetic material foreign bodies incidentally detected on computed tomography (CT) images in routine clinical practice. This presentation of the imaging findings of multiple cosmetic materials may prevent misdiagnosis during interpretation of maxillofacial images.

This study included cases of head-and-neck diseases that were examined by CT at Okayama University Hospital Dentistry during the 5-year period from 2017 to 2021. Using CT image data stored on the image server, we retrospectively investigated cases involving cosmetic surgery-derived foreign bodies other than dental materials in the maxillofacial region. For each cosmetic surgery-derived foreign body included within the imaging area, the location, shape, CT values, and imaging findings of surrounding tissue were obtained from CT images.

Images were acquired using four different types of CT scanner: Aquilion ONE (Canon Medical Systems Corporation, Tochigi, Japan); Aquilion Precision (Canon Medical Systems Corporation, Tochigi, Japan); Discovery CT750 HD (GE Healthcare, Milwaukee, WI, USA); and SOMATOM Definition Flash (Siemens, Nurnberg, Germany). CT scans were obtained with the following parameters: field of view: 12.9 × 12.9 to 32 × 32 cm; tube voltage: 120–140 kV; tube current: 150–500 mA.

All CT images taken multiple times in the same patient during the study period were also examined. The total number of CT cases over the 5-year period from 2017 to 2021 was 5951. The foreign bodies other than normal anatomy that were observed as high-density areas within the imaging range of the maxillofacial region were targeted using CT soft tissue images. CT images of the full extent of the head and neck were reviewed by one dental radiologist. When the same site was treated multiple times and the amount of foreign body changed, only the first image was included; this was regarded as one case. Foreign bodies at different sites in the same patient were regarded as separate cases. Cases were excluded if they met any of the following criteria: foreign bodies of dental material origin (e.g., plates and screws associated with jaw deformities), foreign bodies introduced via trauma, vascular calcifications, and calcifications on the skin.

CT values were measured using a high-resolution medical image monitor (EIZO Corporation, Ishikawa, Japan). The region of interest area for CT value measurements was established in a freehand manner at the center of the lesion, approximately 1–2 mm from the lesion margin. The mean CT value between initial value and the remeasured value at 2 weeks was defined as the CT value of one observer. CT value assessments were performed by two observers with experience in CT examinations and CT measurement (10 and 26 years of experience, respectively).

We also obtained information regarding any additional useful imaging findings by other modalities such as panoramic radiography, magnetic resonance imaging (MRI), and ultrasonography during the same period. Finally, we investigated age, sex, whether the foreign bodies were associated with the disease targeted by the CT scan, and whether any information about cosmetic surgery was available prior to examination.

This study was performed in accordance with the principles of the Declaration of Helsinki. Approval was granted by the Ethics Committee of Okayama University (Date: 5 August 2022/No. 2208-038).

In total, there were 21 cases involving four types of cosmetic surgery-derived foreign bodies in the maxillofacial region identified via CT examination. There were 15 cases (one type) in the nasal region, five cases (two types) in the buccal region, and one case (one type) in the chin region. Their ages and sexes are shown in Fig. 1.

All the 15 cases in the nasal region were located on the nasal dorsum. In terms of shape, 13 cases had a straight I-shape and two cases had an L-shape; thus, the 15 cases had a rod-like morphology Fig. 2. The mean CT value of the 14 cases was 278.0 Hounsfield units (HU; range: 4–540 HU) Fig. 3. One male case was plate like and CT values could not be determined, but the density was uniform on soft tissue images. Hard tissue images showed homogeneous density in 12 cases, but three cases displayed homogeneous density surrounded by an osteosclerotic margin. Regarding other modalities, panoramic radiographs showed no obvious findings, although increased opacity in the median nasal area was suspected in some cases. Six cases had relevant findings on MRI. In five cases, nasal foreign bodies showed signal voids on T1-weighted and STIR images, similar to air-containing areas; there was no contrast enhancement. The remaining case demonstrated moderate signal intensity on T1-weighted images (similar to the intensity of muscle) and a uniform watery high signal on T2-weighted images (similar to the signal of cerebrospinal fluid). This case had a CT value of 4 HU. For all the 15 cases in the nasal area, no cosmetic surgery was declared prior to examination; the foreign body was found incidentally, unrelated to the purpose of CT examination.

In the buccal region, five foreign bodies (two types) were detected. In one case, multiple metallic thread-like linear foreign bodies were present under the buccal skin (Fig. 4). These foreign bodies were linear and CT values could not be obtained. Concerning other modalities, panoramic radiographs showed numerous thread-like opacities overlapping from the maxillary sinus to the maxilla and throughout the mandible, but not in the orbit or pyriform aperture. In four cases, the lesions comprised irregularly shaped lumps or cords extending from the zygomaticus muscle to the subcutaneous fat layer; they were quite visible (Fig. 5). The mean CT value of these four buccal foreign bodies was 16.3 HU (range: 8–26 HU) (Fig. 3). With respect to other modalities, panoramic radiographs showed no obvious findings. MRI showed moderate signal intensity on T1-weighted images and high signal on STIR images. No contrast enhancement was noted. In all five cases of buccal foreign bodies, no cosmetic surgery was declared prior to examination. In both of the two cases where CT findings suggested a cosmetic surgery-derived foreign body as the infectious source of the inflammatory findings, an additional patient interview confirmed a history of Aquamid^® injection approximately 2 years earlier (Fig. 5). In the remaining three cases, the foreign body was discovered incidentally, unrelated to the purpose of the CT scan.

The foreign body in the chin region showed a hemispherical morphology with smooth edges. The foreign body exhibited a uniform high-density area of 202 HU without contrast enhancement (Fig. 6). Regarding other modalities, panoramic radiographs showed no abnormal findings in the chin region. In the case involving the chin region, no cosmetic surgery was declared prior to examination; the detection of foreign bodies was incidental and unrelated to the disease targeted by the CT scan.

Cosmetic surgery for esthetic purposes is an unrestricted medical procedure with diverse treatment methods. Therefore, diverse cosmetic biomaterials are used in such procedures. In this study, we identified 21 cases involving four types of cosmetic surgery-derived foreign bodies in the nasal, buccal, and chin regions of the face that were included in CT scans.