Identification and adjustment of experimental occlusal interference using functional magnetic resonance imaging.

BACKGROUND: The purpose of this study was to use functional magnetic resonance imaging (fMRI) to quantify changes in brain activity during experimental occlusal interference. METHODS: Fourteen healthy volunteers performed a rhythmical tapping occlusion task with experimental occlusal interference of the right molar tooth at 0 mm (no occlusion), 0.5 mm, and 0.75 mm. The blood-oxygen-level dependent (BOLD) signal was quantified using statistical parametric mapping and compared between rest periods and task periods. RESULTS: In tapping tasks with experimental occlusal interference of 0.75 mm or 0.5 mm, there was clear activation of the contralateral teeth-related primary sensory cortex and Brodmann's area 46. At 0 and 30 minutes after removal of the experimental occlusal interference, the activation clearly appeared in the bilateral teeth-related primary sensory cortices and Brodmann's area 46. At 60 minutes after the removal of the experimental occlusal interference, the activation of Brodmann's area 46 had disappeared, and only the bilateral teeth-related primary sensory cortices were active. CONCLUSIONS: The present results suggest that adjustments for experimental occlusal interference can be objectively evaluated using fMRI. We expect that this method of evaluating adjustments in occlusal interference, combined with fMRI and the tapping task, could be applied clinically in the future.

Prevalence and imaging characteristics of detectable tonsilloliths on 482 pairs of consecutive CT and panoramic radiographs.

BACKGROUND: Recent studies suggest that tonsilloliths are clinically related to halitosis and tonsillar abscess. Based on our empirical knowledge, tonsilloliths are relatively commonly encountered in daily clinical practice. It has been reported that the detection rate of tonsilloliths was under 24% in previous reports, although experience suggests otherwise. The purpose of the study was to evaluate the prevalence and characteristics of tonsilloliths using computed tomography (CT). In addition, the possible causes of low detection rates on panoramic radiographs were evaluated based on comparisons between CT images and panoramic radiographs in order to elucidate the limitations of visualizing the area around the palatine tonsils on panoramic radiographs. METHODS: 482 pairs of CT images and panoramic radiographs were retrospectively assessed with respect to the presence and characteristics of tonsilloliths. In addition, the causes in cases of disagreement between the two modalities were analyzed. RESULTS: The detection rate of tonsilloliths was 46.1% using CT scans, unlike previous reports. The characteristics of tonsillolith were dot-like figures with about 300-500 Hounsfield units within the palatine tonsil under the soft palate. The most common length of tonsilloliths was about 3 or 4 mm. As the subjects aged, the detection rate increased gradually. A significant difference in the tonsillolith detection rate was found between the over and under 40-year-old groups (p < 0.0001). However, the detection rate of tonsilloliths was only 7.3% on panoramic radiographs. A significant correlation was observed between the detection rate of tonsilloliths on panoramic radiographs and CT number (Spearman r = 0.429), size, (Spearman r = 0.318), and number of tonsilloliths (Spearman r = 0.333). CONCLUSION: The present results suggest that tonsilloliths are relatively more common than previously suggested. However, panoramic radiographs detect only a small percentage of palatine tonsilloliths. The low detection rates on panoramic radiographs might be related to the degree of calcification, size, and number of tonsilloliths.

Occurrence of silk stitch abscess after surgery in patients with oral squamous cell carcinoma.

OBJECTIVES: To elucidate the predisposing factors and clinical characteristics related to the occurrence of stitch abscess after surgery in patients with oral squamous cell carcinoma (SCC). PATIENTS AND METHODS: The subjects were 232 patients who underwent excision and/or reconstruction and/or neck dissection for oral SCC using silk sutures for high ligation of the blood vessels. Detection rates and characteristics of patients with stitch abscess were retrospectively evaluated by comparing patients with and without stitch abscesses after surgery diagnosed by ultrasonography and findings of various modalities in 232 patients. Several echogenic dots with subtle acoustic shadows in a hypoechoic mass were identified as the characteristic findings of stitch abscess on US. The patient groups with and without stitch abscess were compared with respect to various factors to identify those that predispose to the occurrence of stitch abscess. The factors analyzed included patients' sex and age, chemotherapy treatment, radiotherapy treatment, the presence of a history of allergy, and blood test results. RESULTS: A significant correlation was found between the occurrence of stitch abscess and age, liver function abnormalities on blood tests, and the presence of a history of allergy. Multiple stitch abscesses clearly tended to occur more often than single ones in patients with stitch abscess. CONCLUSIONS: The occurrence of stitch abscesses was related to age, liver dysfunction, and/or the presence of allergies. When diagnosing stitch abscess, the occurrence of multiple stitch abscesses is important.

Fundamental research for dose control during supine dental panoramic radiography.

OBJECTIVE: This study aimed to control radiation doses when using a portable supine dental panoramic radiography system by measured the scattered doses. METHOD: The study used LPX7007 (Asahi Roentgen) for the panoramic radiography system. The subjects comprised a cylinder phantom (QualitA) and a RANDO Phantom (Alderson). The semiconductor dosimeter was an X2 survey sensor (RaySafe). The phantom was set at a height of 1 m from the floor, and the sensor was set at 1 m from the floor at the genital level and 1.5 m at the lens level. Measurements were taken at 30°intervals clockwise from 0°at distances of 0.5 m and 1 m in radius around the phantom. The occupational exposure range was defined as 0 ± 30° and the public exposure range was defined as the occupational exposure range and 30° to 150° and 210° to 330° as the public exposure range. RESULT: The highest doses were observed in the 120° and 240° directions, and the lowest in 0° ± 30° range. The lowest limit number of images taken in the occupational exposure range was 130 images at a distance of 0.5 m, 452 images at 1 m at the lens level for the cylinder phantom, and 320 images at 0.5 m and 1098 images at 1 m for the RANDO Phantom. In the public exposure range at the genital level, there was one image at 0.5 m and six images at 1 m for the cylinder phantom, and two images at 0.5 m and eight images at 1 m for the RANDO Phantom. CONCLUSION: We found that radiation exposure can be reduced by keeping a distance from the subject, avoiding working at 120° and 240° and staying within 0° ± 30° behind the panoramic radiography system.

Stray radiation dose reduction using a backscatter shield and a rectangular collimator for a handheld intraoral X-ray unit.

The objective of this study was to study the dose reduction effect on occupational exposure of operators and public exposure other than operators when a backscatter shield and a rectangular collimator are used in conjunction with a handheld intraoral X-ray unit. The occupational exposure was reduced to 40% when the backscatter shield was attached to the cone-tip, to 13% when the rectangular collimator was attached and to 7.7% when the backscatter shield and rectangular collimator were used together. On the other hand, the public exposure was reduced to 20% when the rectangular collimator was attached, but the backscatter shield was not effective in reducing the public exposure. Attaching a backscatter shield is effective in reducing the occupational exposure, and a rectangular aperture is effective in reducing the occupational exposure, as well as the public exposure.

Comprehensive Study of Anti-UVC Activity and Cytotoxicity of Hot-water Soluble Herb Extracts.

BACKGROUND/AIM: COVID-19 pandemic caused the rapid dissemination of ultraviolet C (UVC) sterilization apparatuses. Prolonged exposure to UVC, however, may exert harmful effects on the human body. The aim of the present study was to comprehensively investigate the anti-UVC activity of a total of 108 hot-water soluble herb extracts, using human dermal fibroblast and melanoma cell lines, for the future development of skin care products. MATERIALS AND METHODS: Exposure time to UVC was set to 3 min, and cell viability was determined using the MTT assay. Anti-UVC activity was determined using the selective index (SI), a ratio of 50% cytotoxic concentration for unirradiated cells to 50% effective concentration that restored half of the UVC-induced decrease of viability. RESULTS: Dermal fibroblasts at any population doubling level were more resistant to UVC irradiation than melanoma cells. Both 49 herb extracts recommended by Japan Medical Herb Association (JAMHA) and 59 additional herb extracts showed comparable anti-UVC activity. SI values of selected herbs (Butterbur, Cloves, Curry Tree, Evening Primrose, Rooibos, Stevia, Willow) were several-fold lower than those of vitamin C and vanillin. Their potent anti-UVC activity was maintained for at least 6 h post irradiation, but declined thereafter to the basal level, possibly due to cytotoxic ingredients. CONCLUSION: UVC sensitivity may be related to the growth potential of target cells. Removal of cytotoxic ingredients of herb extracts may further potentiate and prolong their anti-UVC activity.

UVC-Protective Activity of Lemongrass Among 12 Fat-soluble Herbal Extracts: Rapid Decay Due to Cytotoxicity.

BACKGROUND/AIM: The COVID-19 pandemic led to the rapid spread of the use of ultraviolet C (UVC) sterilizers in many public facilities. Considering the harmful effects of prolonged exposure to UVC, manufacturing of safe skin care products is an important countermeasure. In continuation of our recent study of water-soluble herbal extracts, the present study aimed at searching for anti-UVC components from fat-soluble herbal extracts. MATERIALS AND METHODS: Human dermal fibroblast and melanoma cells were exposed to UVC (1.193 W/m2) for 3 min. Viable cell number was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Cell-cycle analysis was performed using a cell sorter. UVC-protective activity was quantified by the selective index (SI), i.e., the ratio of the 50% cytotoxic concentration for unirradiated cells to the concentration that restored viability of UVC-treated cells by 50%. RESULTS: Only lemongrass extract, among 12 fat-soluble herbal extracts, showed significant anti-UVC activity, comparable to that of lignified materials and tannins, but exceeding that of N-acetyl-L-cysteine and resveratrol. Lemongrass extract was highly cytotoxic, producing a subG1 cell population. During prolonged incubation in culture medium, the anti-UVC activity of lemongrass extract, sodium ascorbate and vanillic acid declined with an approximate half-life of <0.7, 5.4-21.6, and 27.8-87.0 h, respectively. CONCLUSION: Removal of cytotoxic principle(s) from lemongrass extract is crucial to producing long-lasting UVC-protective effects.

Effect of cranium structure on dose distribution during intraoral radiography.

OBJECTIVES: This study aimed to evaluate, the effect of the cranium structure on dose distribution by measuring the dose using the RANDO phantom for safe use of an X-ray unit during personal identification work at a large-scale disaster site. METHODS: As the subject, the head and neck of the RANDO Phantom (Alderson) containing a dry skull composed of a tissue-equivalent substance and having a shape similar to that of a living body were studied. With the body in the supine position, the air doses per second of irradiation time were measured for a total of six sections of the anterior, premolar, and molar teeth (molar on the left side) at a tube voltage of 60 kV and tube current of 10 mA during maxilla and mandible intraoral radiography. RESULTS: The region having the highest exposure dose was the main X-ray direction in both the mandible and maxilla. Conversely, the dose tended to be low in the range from the temporal region to the occipital region on both sides of the horizontal plane, from the frontal region to the occipital region of the sagittal plane, and in the parietal region of the frontal plane. CONCLUSIONS: It would be preferable to examine from the top of the body where the dose tends to decrease for all imaging sites.

Importance of magnetic resonance imaging for evaluation of a child with prominent swelling of the facial region after trauma: report of a case.

In the present case of a 9-year-old girl with prominent swelling in the mental and facial regions after trauma, repeated magnetic resonance (MR) examinations were performed to evaluate areas of incision, because the swelling became worse and more prominent despite intravenous antibiotic treatment. However, there was no evidence of respiratory tract impingement or deformation, including obliteration, on MR imaging. Therefore, surgical treatment involving an incision because of facial region swelling was cancelled, and the intravenous antibiotic therapy was continued. To prevent misdiagnosis and over-treatment of young children with inflammation of the oral and maxillofacial regions, dentists, including pediatric dentists, should be aware of the clinical usefulness of MR examinations. In particular, MR examinations are non-invasive for young children, because there is no X-ray exposure, and they can be used repetitively. At the same time, the present case demonstrated that it is very difficult to understand and predict changes in the inflammation process associated with children's facial trauma.

Overview of Radiological Studies on Visualization of Gubernaculum Tracts of Permanent Teeth.

The eruption pathway from the dental follicle to the gingiva for permanent teeth is known as the gubernaculum tract (GT), a physiologic structure thought to play a role in tooth eruption. Cone beam computed tomography and multi-detector computed tomography have recently been used to visualize the GT, with the results indicating that this structure might be related to the normal eruption of teeth. By contrast, curved and/or constricted GTs may lead to abnormal tooth eruption. In addition, complex odontomas have been reported from within the GT or dental sac of unerupted permanent teeth. If an odontoma occurs within the GT, the tooth will not erupt normally. Moreover, the imaging characteristics of the GT from the top of the odontogenic mass to the alveolar crest are extremely useful for making a differential pathological diagnosis and for differentiating between odontogenic and non-odontogenic masses. Therefore, radiological studies on the GT have been attracting increasing attention. Given this background, the present review aims to clarify the imaging characteristics and review recent studies on the GT considering the importance of the research.

Relationship between inferior alveolar nerve canal position at mandibular second molar in patients with prognathism and possible occurrence of neurosensory disturbance after sagittal split ramus osteotomy.

PURPOSE: To elucidate the relationship between the anatomic position of the inferior alveolar nerve (IAN) at the mandibular second molar and the occurrence of neurosensory disturbances of the IAN after sagittal split ramus osteotomy (SSRO) in patients with mandibular prognathism. Also, the present study evaluated the difference in anatomic position of the IAN between patients with and without mandibular prognathism. PATIENTS AND METHODS: Computed tomography images were taken of 28 patients with mandibular prognathism and 30 without prognathism. On these scans, the IANs from the mandibular second molar region to the mandibular foramen in the mandibular ramus were identified. The present study was designed as a cross-sectional study. The distance from the buccal aspect of the IAN canal to the outer buccal cortical margin of the mandible in the mandibular second molar regions was measured on the computed tomography images. Also, the linear distance between the superior aspect of the IAN canal and the alveolar crest in these regions was calculated. In addition, we investigated the presence or absence of contact between the IAN canal and the inner buccal cortical margin of the mandible from the mandibular second molar to the mandibular foramen in the mandibular ramus. Next, we examined whether neurosensory disturbances occurring after SSRO were related to the position of the IAN at the mandibular second molar. RESULTS: A significant difference was found in the occurrence of neurosensory disturbances of the IAN after SSRO between men and women (χ(2) test, P < .05). For the distance from the buccal aspect of the IAN canal to the outer buccal cortical margin of the mandible in the mandibular second molar region, a significant difference was found between groups with and without neurosensory disturbances (Student's t test, P < .01). The shorter the distance from the buccal aspect of the IAN canal to the outer buccal cortical margin, the more frequent the occurrence of neurosensory disturbances of the IAN. CONCLUSIONS: The present results have demonstrated that gender and the anatomic position of the IAN canal at the mandibular second molar are significantly related to the occurrence of neurosensory disturbances of the IAN after SSRO. Therefore, surgeons should clearly inform patients of the increased possibility of neurosensory disturbances after SSRO when the patients are female and are found to have a shorter distance from the buccal aspect of the IAN canal to the outer buccal cortical margin.

Reduction of operator exposure by rectangular collimation in portable intraoral radiography.

Portable intraoral X-ray units are frequently used for home-visit dental treatment and personal dental identification. Therefore, the reduction of operator exposure is crucial. Rectangular collimation is effective at reducing patient exposure and operator exposure; however, its effects are not known. We investigated the reduction of operator exposure through rectangular collimation by measuring the backscattered dose in relation to the operator exposure dose. Using a portable intraoral X-ray unit, a head phantom for CT dose measurement as the object, a dosimeter, and stainless-steel rectangular collimator, a 1-cm ambient dose equivalent was measured in intervals of 15° in horizontal and vertical planes with the radii of 50 and 100 cm. The backscattered dose decreased to approximately one-third when a rectangular collimator was attached to the cone tip. This may have been due to the reduction of the volume of scattered X-rays generated in the phantom by rectangular collimation. We clarified that rectangular collimation is effective at reducing the operator exposure and is useful for protecting the operators of portable intraoral X-ray units during home-visit dental treatment and personal dental identification.

Comparison of air dose and operator exposure from portable X-ray units.

This study was aimed at investigating and comparing exposure dose of workers and the surrounding workers. In addition, worker's exposure was also measure about lens and finger. Four intraoral portable X-ray units were evaluated. The stray radiations were measured using Pitman 37D and ionization chamber (Pitman). MyDosemini (ALOKA) was used for measurement of the finger exposure dose. Without the shield became high in anterior 0.5 m. Comparing the air dose for the four models used in this study showed a high tendency for the two NOMAD models. And using the shields, the images could be taken 4.6 times of the baseline at a maximum and 3.6 times on average. The finger radiation exposure dose was low with both of the NOMAD models, with no significant difference found. By setting the baseline value without a shield, finger radiation exposure when using a shield was lower than the detection limit for the D3000, and was reduced by approximately 94-96% for other three models. All models can photograph around 100 bodies, so it is considered that it is not necessary to switch out the operator considering the operation limit. But even if it does not reach the operation limit, the stochastic effects of radiation exposure can be increased as well as the deterministic effects of the operation limit. The operator and the surrounding workers seek to protect themselves. It is important to perform exposure management that takes into account the stochastic effects to the operator and the surrounding workers.

Can the lower rate of CT- or MRI-related adverse drug reactions to contrast media due to stricter limitations on patients undergoing contrast-enhanced CT or MRI?

OBJECTIVE: The aim of this study was to examine whether a decreased occurrence rate of adverse drug reactions (ADRs) to contrast media in contrast-enhanced CT and MRI was attributable to appropriate criteria for patients with some diseases. A secondary aim was to elucidate safety profiles for contrast media and factors influencing the occurrence of ADRs. METHODS: Clinical data of patients who underwent contrast-enhanced CT (5576 cases) or MRI (3357 cases) were retrospectively analyzed to evaluate rates of ADRs to contrast media, symptoms of ADRs, treatments for ADRs, and differences in medical history, blood test results, and other factors between patients with and without ADRs in a dental hospital. RESULTS: The rate of ADRs to contrast media was 0.54% for CT and 0.09% for MRI. The most frequent ADRs in contrast-enhanced CT or MRI were nausea and vomiting as physiologic reactions. Two serious reactions were seen for CT, but none for MRI. Significant differences between patients with and without ADRs were seen in liver function according to blood tests for CT, and in digestive disorders elicited from medical interviews for MRI. CONCLUSION: The lower occurrence rate of ADRs to contrast media in dental hospitals could be due to the adoption of appropriate criteria for patients with some diseases undergoing enhanced CT or MRI. Complete suppression of ADRs to contrast media for CT or MRI is unrealistic, so attention is warranted for patients with decreased liver function when performing enhanced CT, and for patients with digestive disorders when performing enhanced MRI.

Augmentation of Neurotoxicity of Anticancer Drugs by X-Ray Irradiation.

BACKGROUND: In order to investigate the combination effect of anticancer drugs and X-ray irradiation on neurotoxic side-effects (neurotoxicity), a method that provides homogeneously X-ray-irradiated cells was newly established. MATERIALS AND METHODS: PC12 cell suspension was irradiated by X-ray (0.5 Gy) in serum-supplemented medium, immediately inoculated into 96-microwell plates and incubated overnight. The medium was replaced with fresh serum-depleted medium containing 50 ng/ml nerve growth factor to induce differentiation toward nerve-like cells with characteristic neurites according to the overlay method without changing the medium. The differentiated cells were treated by anticancer drugs as well as antioxidants, oxaliplatin or bortezomib, and the viable cell number was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide method. RESULTS: Antioxidants and anticancer drugs were cytotoxic to differentiating PC12 cells. Combination of anticancer drugs and X-ray irradiation slightly reduced cell viability. CONCLUSION: The present 'population irradiation method' may be useful for the investigation of the combination effect of X-ray irradiation and any pharmaceutical drug.

Characteristics of diffusion-weighted images and apparent diffusion coefficients of ranulas and other masses in and around the floor of the mouth.

OBJECTIVE: The aim of this study was to evaluate the characteristics of diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) values of ranulas. In addition, to elucidate DWI findings and ADC values of other representative masses in and around the floor of the mouth. STUDY DESIGN: DWI findings and ADC values in 35 patients with ranulas and 33 patients with other masses were retrospectively reviewed with a central focus on cystic masses or lesions that may have cyst-like components in and around the floor of the mouth based on the diagnosis of each respective disease. RESULTS: Ranulas were all well-defined, homogeneous masses with high signal intensity on DWI. The mean ± standard deviation ADC value of the 35 ranulas was 2.59 ± 0.31 × 10-3 mm2/s. There was a significant difference in ADC values between simple and plunging ranulas. On DWI, most other masses were heterogeneous, and most ADC values, except those for thyroglossal duct cysts, hemangiomas, and pleomorphic adenomas, were significantly lower than those for ranulas. CONCLUSIONS: The characteristic DWI and ADC findings of ranulas can be determined accurately, and these data can be significantly useful in the differential diagnosis of many kinds of diseases in and around the oral floor.

Significance and usefulness of imaging characteristics of gubernaculum tracts for the diagnosis of odontogenic tumors or cysts.

We aimed to determine the significance and usefulness of imaging characteristics of gubernaculum tracts (GT) for the diagnosis of odontogenic tumors or cysts. This was a retrospective analysis of relationships between odontogenic or non-odontogenic tumors or cysts and the GT that were visualized using multi-detector computed tomography (MDCT). The relationship between the size of a mass and expansion of the GT in all odontogenic tumors or cysts to which GTs were contiguous on MDCT, was statistically analyzed. Intact or expanded GTs were detected in MDCT images on the top of almost all odontogenic tumors or cysts, but not on non-odontogenic tumors or cysts. Characteristic image findings regarding the relationship between the GT and the odontogenic mass were detected for the respective odontogenic tumors or cysts in which the GTs were contiguous to the mass on MDCT. In ameloblastomas, expansion of the GTs significantly and very strongly correlated with tumor size (r = 0.741, p = 0.0001), but this correlation was very weak in dentigerous cysts (r = 0.167, p = 0.028) and there was no correlation between these parameters in odontogenic keratocysts (r = -0.089, p = 0.557). The imaging characteristics of GTs at the top of masses should be very useful for both the differential diagnosis of the pathological diagnosis of odontogenic masses and for differentiation between odontogenic and non-odontogenic masses.

Functional evaluation of swallowing in patients with tongue cancer before and after surgery using high-speed continuous magnetic resonance imaging based on T2-weighted sequences.

OBJECTIVES: The aim of this study was to determine the usefulness of evaluating the function of swallowing before and after surgery in patients with tongue cancer by using T2-weighted sequences of high-speed continuous magnetic resonance imaging (HSCMRI). STUDY DESIGN: The imaging findings and related parameters on HSCMRI along with those on routine MRI examinations before and after surgery were examined in 19 patients with tongue cancer. In addition, changes in various parameters during 1 year after surgery were evaluated in 10 patients. RESULTS: In most patients examined, the direction of flow to the esophagus could be seen on HSCMRI before and after surgery. Significant correlations were observed among 4 parameters and in the responses to a dysphagia questionnaire. CONCLUSIONS: The results of the present study suggest that the dynamics of swallowing can be directly visualized on HSCMRI by using 4 parameters that permit the evaluation of changes before and after surgery, and this enables objective evaluation of patients' swallowing complaints.

Multiple mandibular static bone depressions attached to the three major salivary glands.

A Stafne bone defect is a static bone depression in the mandible that is commonly observed in cortical bone near the mandibular angle. We herein present a rare case in which static bone depressions attached to the three major salivary glands were observed on panoramic radiography and computed tomography (CT). The three static bone depressions in the mandible were visualized on a panoramic radiograph and CT as oval radiolucent masses in a 68-year-old man. The CT numbers in the bone depressions ranged from 10 to 50 HU, and they were close to those of the respective salivary glands. Based on the CT numbers, the areas in the bone depressions were determined to be a normal parotid gland, sublingual gland, and submandibular gland. The patient underwent a follow-up examination and did not request further consultation.

Changes in the distributions of fluorine-18-labelled fluoro-2-deoxy-d-glucose accumulation into tongue-related muscles after dissection in patients with tongue cancer.

OBJECTIVES: To elucidate the changes in the distributions of fluorine-18-labelled fluoro-2-deoxy-d-glucose (18F-FDG) accumulation in the tongue muscles of patients following four kinds of surgical operations for tongue cancers. METHODS: The changes in the distributions of 18F-FDG accumulations in the tongue muscles on positron emission tomography (PET)-CT, in association with imaging findings on CT and MRI, were retrospectively analyzed before and after four kinds of surgical operations for 50 patients with tongue cancers. RESULTS: 18F-FDG-PET-positive areas appeared at the back of the intrinsic muscles of the tongue after invasive surgery for tongue cancers despite the absence of abnormal findings on CT and MRI. A correlation between the standardized uptake value maximum of 18F-FDG in the intrinsic muscles and the degree of invasiveness of the surgical procedures for tongue cancers (r = 0.539, p < 0.01) was found. CONCLUSIONS: It is important to pay attention to the changes in 18F-FDG distributions in the intrinsic muscles of the tongue before and after invasive surgery despite the absence of abnormal findings on CT and MRI when evaluating the tongue on 18F-FDG-PET.