Kunihiro Miwa

Imaging findings of lipomas in the orofacial region with CT, US, and MRI

OBJECTIVE The aim of this study was to document retrospectively the imaging findings of lipomas with the use of computed tomography, ultrasonography, and magnetic resonance imaging. STUDY DESIGN Thirteen patients with 11 lipomas and 2 lipomatoses were evaluated. Eleven cases were examined by computed tomography, 9 by ultrasonography, and 3 by magnetic resonance imaging. RESULTS Lipomas had a density ranging from -134 to -83 Hounsfield units, (mean-108) on the computed tomography images. The margins were ill defined in 9 of 10 cases. The superficial muscles were displaced externally in 8 cases and internally in 2 cases. With ultrasonography, 8 lesions were hypoechoic, and one was hyperechoic. All three lesions had a high signal intensity on both T1- and T2-weighted images. CONCLUSIONS Lipomas had a specific range of computed tomography Hounsfield unit values and also displaced the surrounding soft tissue. Although some variation in the ultrasonographic appearance was observed, the lesions tended to be hypoechoic. These findings may be useful for diagnosing lipomas in the orofacial region.

THE COMBINED USE OF US AND MR IMAGING FOR THE DIAGNOSIS OF MASSES IN THE PAROTID REGION

Purpose: To evaluate the usefulness of the combination of the two non-invasive modalities US and MR imaging to diagnose masses in the parotid region. Material and Methods: The US and MR findings of 21 patients with parotid masses were analyzed retrospectively by two radiologists without any clinical or histopathological information. The specific points evaluated were location, shape, margin, internal architecture, and intensity level on both US and MR, posterior echo enhancement on US, and capsule-like lining of the tumor on MR. Results: The findings concerning the shape and margin on US and MR were in fairly good agreement. Concerning the findings of the internal architecture, US could reveal the minute structures of the tumor while MR demonstrated differences in the signal intensities of histological tissue types of the various tumors. The posterior echo enhancement on US and the capsule-like lining on MR of the tumors were also useful for the diagnosis. Conclusion: Our results suggest that the combination of US and MR is useful for examining soft tissue masses in the parotid region to make a more accurate diagnosis, and not just differentiate malignant lesions from those which are benign.

Magnetic resonance imaging of oral and maxillofacial angiomas

Eleven patients with oral and maxillofacial angiomas (seven hemangiomas and four lymphangiomas) were evaluated with magnetic resonance imaging using a 0.2-T permanent system and spin-echo pulse sequences. These lesions typically had signal intensities that were iso T1-weighted, similar to muscle, and high T2-weighted, greater than subcutaneous fat. Nine tumors had well- or relatively well-defined margins, and seven cases had curvilinear structures of low signal intensities in the masses on T2-weighted images. It was impossible to distinguish hemangiomas from lymphangiomas on MR images. Our experience suggested that most angiomas of oral and maxillofacial regions present special characteristics on magnetic resonance images. It is thought that information obtained with magnetic resonance images can contribute significantly to the evaluation of the extent of these lesions.

Diagnostic analyses of cervical lymph nodes in patients with oral squamous cell carcinoma using CT and US

CT and US images of 24 patients with oral squamous cells carcinoma were studied retrospectively to clarify the characteristics finding of metastases in cervical lymph nodes. CT images of 201 lymph nodes were analyzed for patterns in appearance and maximum diameter on axial images. US findings of 45 lymph nodes were investigated with regard to internal echo. The metastatic nodes were found to be characterized by rim enhancement on CT and an heterogeneous appearance on US, while the features of non-metastatic nodes were an homogeneous appearance on CT with a density lower than that of the sternocleid mastoid muscle, and spot or septum patterns on US. Based on these results, we suggest new diagnostic criteria for metastatic cervical nodes in oral squamous cell carcinoma combining CT and US examinations.

Central squamous cell carcinoma of the mandible: Computed tomographic findings

Five cases of central squamous cell carcinoma of the mandible were investigated with the use of computed tomography. Bucco-lingual extent and spread along the mandibular division of the trigeminal nerve were evaluated. Three patients with trismus showed involvement of the masseter or medial pterygoid muscle on computed tomography. Involvement of more than two landmarks along the trigeminal nerve were observed in cases with both paresthesia of the lower lip and severe pain that resembled neuralgia. Perineural invasion was confirmed histologically in four cases, and all of these patients had both severe pain and mandibular canal involvement that could be demonstrated with computed tomography. When localized soft tissue changes are evident along the course of the trigeminal nerve in the region between the mandibular foramen and foramen ovale, ascending perineural spread should be suspected. Computed tomography findings correlated well with clinical symptoms but added information about the spread of the lesion within the surrounding soft tissue.

Quantitative evaluation of vascularity within cervical lymph nodes using Doppler ultrasound in patients with oral cancer: relation to lymph node size

OBJECTIVES The aim of this study was to quantitatively evaluate the relationship between vascularity within lymph nodes and lymph node size on Doppler ultrasound images of patients with oral cancer. METHODS A total of 310 lymph nodes (86 metastatic, 224 benign) from 63 patients with oral cancer were classified into 4 groups according to their short axis diameters: Group 1, short axis diameters of 4-5 mm; Group 2, 6-7 mm; Group 3, 8-9 mm; and Group 4, ≥ 10 mm. Vascular and scattering indices of lymph nodes on Doppler ultrasound images were analysed quantitatively. The vascular index was defined as the ratio of blood flow area to the whole lymph node area and the scattering index was defined as the number of isolated blood flow signal units. RESULTS For metastatic lymph nodes, the vascular index was highest in Group 1 and decreased as lymph node size increased. The vascular index of benign lymph nodes did not differ significantly among the four groups. The vascular index of metastatic lymph nodes was significantly higher than that of benign lymph nodes in Group 1. For metastatic lymph nodes, the scattering index increased as lymph node size increased and was significantly higher than that of benign lymph nodes in Groups 2-4. CONCLUSIONS An increase in vascularity is a characteristic of Doppler ultrasound findings in small metastatic lymph nodes. As the metastatic lymph node size increases, blood flow signals become scattered, and the scattering index increases.

Computed tomography appearance of marked keratinization of metastatic cervical lymph nodes: A case report

A case of squamous cell carcinoma of the tongue is reported with emphasis on an atypical finding of cervical lymph node metastasis visible on computed tomography. Multiple cervical lymph nodes revealed a high computed tomographic value of about 330 HU, lower than that of calcification. The lymph nodes revealed well-defined elliptical hyperechoic masses with an echogenic line and posterior shadow on ultrasonography. The appearance of a high density mass on computed tomography with a computed tomographic value lower than that of calcification may be a reliable finding of metastasis because it demonstrates the presence of marked keratinization produced by squamous cell carcinoma.

Vascularity as assessed by Doppler intraoral ultrasound around the invasion front of tongue cancer is a predictor of pathological grade of malignancy and cervical lymph node metastasis

OBJECTIVES To quantitatively evaluate the relationship of vascularity of tongue cancer as demonstrated on intraoral ultrasonography images and tumour thickness with pathological grade of malignancy and the presence of cervical lymph node metastases. METHODS 18 patients with tongue cancer were enrolled in this retrospective study. Using Doppler ultrasonography images of the invasion front of the cancers along the length of their tumour boundaries, three vascular indexes were analysed quantitatively, namely ratio of blood flow signal area within the cancer to whole tumour area (BAR), blood flow signal number ratio (BNR) and blood flow signal width ratio (BWR). The associations between these three indexes and occurrence of cervical lymph node metastasis and pathological grade of malignancy [Yamamoto-Kohama (YK) classification] were assessed. Furthermore, the relationship between tumour thickness and occurrence of cervical lymph node metastasis was evaluated on B-mode intraoral ultrasonography images. RESULTS There was no significant association between BAR and tumour thickness or occurrence of cervical lymph node metastasis. The BNRs and BWRs of patients with cervical lymph node metastasis were significantly higher than those of patients without nodal involvement. The BWRs of patients with high-grade malignancy (YK-4C) were significantly higher than those of patients with low-grade malignancy (YK-2 or 3). CONCLUSIONS BNR and BWR on the invasion front of the tongue cancer are predictors of pathological grade of malignancy and cervical lymph node metastasis.

Basic principles of magnetic resonance imaging for beginner oral and maxillofacial radiologists

The basic principles and diagnostic methods of magnetic resonance imaging (MRI) for beginning surgeons are described in this review. MRI is an important technique that is essential for diagnoses in the maxillofacial area. It is a scanning method that obtains tomographic images of the human body using a magnetic field. In contrast to computed tomography, it does not utilize X-rays and, therefore, represents a noninvasive test that lacks radiation exposure. It is particularly effective for soft-tissue diagnoses. MRI involves imaging protons in vivo. Protons emit a signal when a radio frequency pulse is applied in a magnetic field; the MRI device then forms an image from these signals. The basic images produced are T1- and T2-weighted images; comparison of these images is the first step of MRI-based diagnosis. Short-T1 inversion recovery images, which eliminate the signal from fat, are also useful for diagnosis. Gadolinium is used as a contrast agent for MRI. Taking sequential images at fixed intervals while injecting the contrast agent and then graphing the contrast effect along the time axis produces a time–signal intensity curve, which is useful for identifying features such as malignant neoplasms based on the graph pattern.

Effects of surrounding conditions on boundary and internal echoes of simulated mass lesions: A phantom study

Ultrasonography has been widely used in the maxillofacial region because of the ability to demonstrate pathological conditions in real time without radiation exposure. However, echo patterns of mass lesions vary with the surrounding tissue conditions. To examine the effects of the various surrounding conditions on depiction of such lesions on echograms, we constructed a model, an echo phantom consisting of an agar object, with or without scattering (methylcellulose) or absorptive (barium sulfate) material, and a corresponding surrounding medium. The objects boundary clarity decreased with increasing concentration of either the surrounding scattering or absorptive media, whereas the internal echo intensity of the object also decreased only with increasing concentration of the surrounding absorptive medium. The object with absorptive material produced peripheral echoes at the border. These results suggest that care should be taken when boundary echoes are evaluated as echo signs of lesions.