Atypical MRI and Histopathological Findings in Dermoid Cyst.

On images, a dermoid cyst is often described as resembling a "sack of marbles" or "marbles in a bag". Typically, it comprises an inhomogeneity filled with multiple nodules in a fluid matrix on both computed tomography and magnetic resonance imaging (MRI). How it appears, however, will vary depending on its histological contents, which may cause confusion in arriving at a diagnosis. This report describes a dermoid cyst in the floor of the mouth of a 55 year-old woman that showed an atypical internal appearance on MRI. Most of the lesion showed homogeneous high signal intensity on T1 - and T2-weighted images, suggesting that it was derived from fat. A small area within the mass, however, showed moderate signal intensity almost equal to that of muscle on T1-weighted images and high signal intensity on fat-suppressed T2-weighted images. Given the location of the lesion, a dermoid cyst was one possible diagnosis. A lipoma or lipoma variants were also considered, however, based on signal intensity. Histopathological section of the excised specimen revealed a dermoid cyst with sebaceous glands in its walls and keratin in its cavity. Dermoid cysts show variation in their internal structures and contents. Since MRI can reflect such histological variation, signal intensity requires careful interpretation.

Imaging Findings in AIDS-related Oral Kaposi's Sarcoma.

Kaposi's sarcoma (KS) is one of the most common diseases in patients with acquired immunodeficiency syndrome, but is rarely encountered in dental practice in Japan. We encountered a case of oral KS (OKS) presenting in the hard palate, gingiva, and tongue in a 41-year-old man. We report the results of imaging, including computed tomography (CT), magnetic resonance imaging, and positron emission tomography/CT in this case. The process leading to an imaging diagnosis of OKS is discussed, emphasizing the importance of collating clinical, laboratory, pathological, and radiological findings. The present results suggest that mapping of accurate tumors is very important in cases of OKS, and that multiple or bilateral manifestations, ill-defined margins, osteolysis, and swollen lymph nodes, in particular, need to be taken into account.

Diagnosis of retrodiscal tissue in painful temporomandibular joint (TMJ) by fluid-attenuated inversion recovery (FLAIR) signal intensity.

AIMS: The purpose of the present study is to analyze the fluid-attenuated inversion recovery (FLAIR) signal intensity of the retrodiscal tissue in a painful temporomandibular joint (TMJ), and to develop a diagnostic system based on FLAIR data. METHODOLOGY: The study was based on 33 joints of 17 patients referred for MR imaging of the TMJ. Regions of interest were placed over retrodiscal tissue and gray matter (GM) on FLAIR images. Using signal intensities of GM as reference points, signal intensity ratios (SIR) of retrodiscal tissue were calculated. SIRs in painful TMJ were compared with those in painless TMJ. Wilcoxon's Rank Sum Test was used to analyze the difference in SIRs between the painful and painless groups (P<0·05). RESULTS: The SIRs of retrodiscal tissue were significantly higher in painful joints than in painless joints. CONCLUSION: FLAIR sequences provide a high signal in patients having painful TMJ, and it suggests that retrodiscal tissue in painful TMJ contains elements such as protein.

Optimization of parameter settings in cine-MR imaging for diagnosis of swallowing.

Videofluorography is frequently used to evaluate swallowing and is considered the "gold standard" among imaging modalities. This modality, however, has several disadvantages, including radiation exposure and limitations in the detection of soft tissues. Conversely, magnetic resonance imaging (MRI) offers excellent contrast resolution in soft tissue without radiation exposure. A major drawback of MRI in evaluating swallowing, however, is that temporal resolution is poor. The aim of this study was to investigate a new cine-MRI modality. Imaging parameters were optimized and the efficacy of this new technique is discussed. Three techniques for speeding up MRI were combined: true fast imaging with steady state precession, generalized auto-calibrating partially parallel acquisition, and key-hole imaging. The effects of the receiver coils used, receiving bandwidth, slice thickness, and flip angle on each image were determined. The optimal imaging parameters obtained comprised a reduction factor of 2, receiving bandwidth of 1,000 Hz/pixel (repetition time of 151.7 milliseconds and echo time of 1.4 milliseconds), flip angle of 50°, and slice thickness of 6 mm. Neck and spine coils were used. Under these conditions, the new cine-MR imaging technique investigated showed a temporal resolution of 0.1 sec/slice (10 frames/sec). Even with optimized parameter settings, this technique did not allow a true temporal resolution of 30 frames/sec by a large margin. Motion artifacts persisted. Further study is needed on how to speed up this technique.

Signal intensity on fluid-attenuated inversion recovery images of condylar marrow changes correspond with slight pain in patients with temporomandibular joint disorders.

OBJECTIVES: Edema and necrosis of the temporomandibular joint (TMJ) have been described in terms of bone marrow signal abnormalities in magnetic resonance imaging (MRI). However, painful joints often show no such signaling abnormalities, making the diagnosis of TMJ disorders difficult in the clinical setting. An association has been suggested between TMJ bone marrow change and TMJ pain, but even when such change results in slight pain, it may be too slight to be visually apparent on MR images. We hypothesized that fluid-attenuated inversion recovery (FLAIR) can be used to detect such minimal changes. The purpose of this study was to determine whether there is an association between signal intensity on FLAIR images and pain in the TMJ. METHODS: The study included 85 TMJs in 45 patients referred to our department for MRI. The signal intensity on FLAIR images was measured. Pain was evaluated based on the visual analog scale. An unpaired t test and Pearson's product-moment correlation coefficient were used for the statistical analysis. A p value of <0.05 was considered statistically significant. RESULTS: Signal intensity on the FLAIR images was significantly higher in painful than in nonpainful TMJs, although a significant correlation was not observed between the signal intensity and the pain score. CONCLUSIONS: The results of this study suggest an association between abnormalities in the marrow of the mandibular condyle and pain. They also indicate that FLAIR imaging is a useful tool in the clinical diagnosis of painful TMJs.

Dentigerous cysts suspected the other odontogenic lesions on panoramic radiography and CT.

Dentigerous cysts are known as the second most common type of cyst in the jaws. The cyst is one of the lesions occurred frequently in the posterior body of the mandible and is often related to the unerupted third molar and forms around the crown of the unerupted tooth attaching at the cementoenamel junction. Such characteristic appearances are the diagnostic points differentiating from ameloblastoma or odontogenic keratocyst. However, it would be hard for us to diagnose it as a dentigerous cyst if the lesion does not show its typical appearance. We experienced two cases of dentigerous cysts which did not form around the crown of the unerupted tooth on radiologically. Both cysts were relatively large and resorbed adjacent teeth roots. Therefore, an ameloblastoma or an odontogenic keratocyst was suspected rather than a dentigerous cyst as the imaging diagnosis. The biopsy revealed that the lesion was a "dentigerous cyst" in one of the cases and "developmental cyst with inflammation" in another case. After the excision, the histopathological diagnosis was a dentigerous cyst with inflammation in both cases. This report shows the two cases of dentigerous cysts focusing on panoramic radiography and CT images. Also, we discuss the differential diagnosis by reconsidering those diagnostic points.

Reliance on diagnostic elements in panoramic imaging with focus on ameloblastoma and keratocystic odontogenic tumor: psychometric study.

The purpose of this study was to investigate degree of observer reliance (RD) on specific diagnostic elements in differential diagnosis of ameloblastoma (AB) and keratocystic odontogenic tumors (KOT) on panoramic images. The RD for 12 diagnostic elements, including 2 clinical and 10 radiographic elements, as recorded by eight dental radiologists on an ordinal ranking scale, was determined for 9 ABs and 9 KOTs. Intraobserver (IaOC) and inter-observer concordance (IeOC) for both ABs and KOTs were statistically analyzed in terms of RD. Significant differences in IeOC were also investigated between ABs and KOTs. The ranking of diagnostic elements was identified in each case of AB or KOT and classified according to IeOC. The mean rating scores of the 10 radiographic elements were then statistically compared and the RD for radiographic elements classified in each group. Good IaOC and IeOC were identified for the RD for the 12 diagnostic elements. IeOC differed significantly between the AB and KOT groups: the AB group showed higher concordance than the KOT group. Ameloblastoma lesion groups where IeOC was relatively high (χ(2)≥70, 70>χ(2)≥60) enabled ranking into four groups. Keratocystic odontogenic tumor lesion groups with χ(2) values of ≥50 and <50 showed ranking into five groups and two groups, respectively. In particular, the AB lesion groups showed a highly significant difference for the specified element of "adjacent radicular state". In panoramic diagnosis, the RD of dental radiologists for diagnostic elements is more consistent for AB than for KOT. In particular, "radicular state adjacent to a lesion" may be an decisive element in distinguishing between AB and KOT.

Imaging of the mylohyoid muscle: separation of submandibular and sublingual spaces.

OBJECTIVE: This article focuses on the anatomy of the mylohyoid muscle, a crucial landmark in imaging of the oral cavity and upper neck, showing dissected specimens and CT and MR images. CONCLUSION: Identification of the relationship of a lesion in the sublingual space to the mylohyoid muscle using MDCT and high-resolution MRI is a key part of the imaging assessment of the oral cavity and upper neck.

Magnetic resonance signal intensity from retrodiscal tissue related to joint effusion status and disc displacement in elderly patients with temporomandibular joint disorders.

Magnetic resonance imaging (MRI) on patients with temporomandibular joint disorders (TMD) has revealed that a decrease and/or increase in signal intensity from retrodiscal tissue, joint effusion (the excessive accumulation of joint fluid) and articular disc displacement are related to TMD. However, the effect of aging on these phenomena has yet to be clarified. This study was carried out to explore the relationship between changes in signal intensity from retrodiscal tissue, joint fluid status and pathological disc conditions in elderly patients with TMD. Twenty patients aged over 60 years were examined. They consisted of one man and 19 women, and ranged between 60 and 79 years in age (mean, 66.0 years). The relationships between decreased signal intensity on proton-density-weighted (PDW) images and increased signal intensity on T2-weighted (T2W) MR images from retrodiscal tissue, joint fluid status and state of articular disc were examined. Joint fluid status was classified into 5 levels by extent of high signal areas in upper and lower articular spaces on T2W images. Disc displacement status was evaluated by PDW images. The Wilcoxon test was applied for the statistical analysis. The group showing increased T2W signal intensities from the retrodiscal tissue consisted of 31 out of 40 joints (77.5%). This group showed a significant difference in comparison with the other groups in which no apparent joint fluid was shown (p<0.05). There were no statistically significant differences among other categories. The results suggest a negative relationship between joint fluid and increased signal intensity from retrodiscal tissue due to reflection of the inflammatory reaction in TM joints.

Evaluating the mandibular condyles of patients with osteoarthritis for bone marrow abnormalities using magnetic resonance T2 mapping.

OBJECTIVES: This study investigated whether erosion and osteophyte correlates with condyle bone marrow abnormalities (BMA), as detected with quantitative T2 mapping. METHODS: Fifty-six joints (in 44 patients) that demonstrated evidence of bony erosion (ER) or osteophytes (OS) related to disc displacement without reduction were studied with MR images. A control group of 50 joints (in 50 patients) was included. The subjects were divided into five groups; noAR (control), noBMA-ER, BMA-ER, noBMA-OS, and BMA-OS. T2 mapping was performed and the regions of interest were placed over the bone marrow at the top of the condyle. The mean T2 values of the bone marrow of the mandibular condyle were calculated for all mapping images. After assessing age-related changes in T2 values of noAR group using Pearson's product-moment, differences in median T2 values of five groups were analyzed using Kruskal-Wallis test, and Steel-Dwass test (p < 0.05). RESULTS: There was no significant correlation between age and T2 value in noAR group. The median T2 values of noBMA-ER and BMA-ER groups were significantly higher than those of noAR, noBMA-OS and BMA-OS groups. Those of noBMA-OS and BMA-OS groups were significantly lower than those of noAR, noBMA-ER and BMA-ER groups. There was no significant difference between noBMA and BMA groups. CONCLUSIONS: It is suggested that erosion and osteophyte of the condyle may correlate with bone marrow abnormalities. T2 mapping could be show slight marrow changes of the arthritic condyle.

A potential reference point for assessment of condylar bone marrow of the temporomandibular joint on proton density weighted images.

The purpose of this research was to determine a potential reference point for measurement of signal intensity of bone marrow of the condyle on proton density-weighted images (PDW) prior to analysis of bone marrow abnormality related to symptomatic osteoarthritis of the temporomandibular joint (TMJ). The study was based on 79 joints in 41 patients. The regions of interest (ROI) were placed over the bone marrow of the condyle and four other structures, It was hypothesized that a correlation between signal intensity of ROI over bone marrow and that of another structure would provide a potential reference point4or measurement of signal intensity of bone marrow. A significant positive linear correlation was found in the group for gray matter-1 and bone marrow. The correlation coefficient was 0.3 (Pearson correlation coefficient; p < 0.05). It was determined that gray matter is a potential reference point in evaluating the signal intensity of bone marrow in the mandibular condyle.

Differences in signal intensities of temporomandibular joint (TMJ) effusion on fluid-attenuated inversion recovery (FLAIR) images.

OBJECTIVES: Joint effusion is demonstrated by high signal intensity in the upper and lower temporomandibular joint (TMJ) spaces on T2-weighted images. The fluid-attenuated inversion recovery (FLAIR) technique can be applied to analyze joint effusion in the TMJ. FLAIR signal intensity can be more sensitively influenced by the contents of joint effusion than T2-weighted signal intensity. The purpose of this study was to analyze the signal intensity of joint effusion on FLAIR images and to investigate the changes in joint effusion contents according to the status of TMJ disorders. METHODS: A total of 48 joints (45 patients) with joint effusion were investigated by magnetic resonance (MR) imaging. Regions of interest were placed over the joint effusion and gray matter on FLAIR images. The joints were categorized as normal disk position (NL), disk displacement with reduction (DWR), disk displacement without reduction (DWOR), and osteoarthritis (OA). The signal intensity ratio of joint effusion was calculated using gray matter as the reference point. The Kruskal-Wallis test and Steel test were applied. A probability of less than 0.05 was considered statistically significant. RESULTS: The median signal intensity ratios of joint effusion differed significantly among the four joint categories (p = 0.02, Kruskal-Wallis test). The median signal intensity ratio of joint effusion in the OA category was significantly higher than that in the NL category (p = 0.04, Steel test). CONCLUSIONS: The present findings suggest that FLAIR images can demonstrate the changes in joint effusion contents according to the status of TMJ disorders.

Evaluation of lateral pterygoid muscles in painful temporomandibular joints by signal intensity on fluid-attenuated inversion recovery images.

OBJECTIVES: Pathological changes of the lateral pterygoid muscle (LPM) have been investigated using various modalities, including magnetic resonance (MR) imaging and electromyography. Fluid-attenuated inversion recovery (FLAIR) is an MR sequence that we hypothesized can be used to evaluate abnormalities of the LPM. The purpose of this study was to analyze the FLAIR signal intensity of the LPM in painful temporomandibular joints (TMJs) and investigate the pathological changes of the muscle. METHODS: The study was based on 149 TMJs of 77 patients who were referred for MR imaging of the TMJ. Patients rated their degree of pain during chewing and mouth opening using a visual analog scale (VAS). Regions of interest were placed over the superior and inferior heads of the LPM and gray matter on FLAIR sagittal images. Using the signal intensity of gray matter as a reference, the signal intensity ratio (SIR) of the LPM was calculated. Spearman's rank-correlation coefficient was used to analyze the correlation between the SIR and the VAS score (p < 0.05). RESULTS: A significant correlation was present between the SIR on FLAIR images and the VAS score. CONCLUSIONS: These results suggest that the FLAIR signal intensity of the superior and inferior heads of the LPM significantly increases as TMJ pain becomes more severe. Thus, FLAIR could be useful in assessing the relationship between the MR signals of the LPM and clinical symptoms.

Osseous abnormalities related to the temporomandibular joint.

With the arrival of arthrography, computed tomography, and magnetic resonance imaging, diagnostic imaging of the temporomandibular joint has improved tremendously over the last 20 years. In patients with temporomandibular joint pain and dysfunction, the main focus was on meniscal pathology. The purpose of this article is to discuss several osseous abnormalities and demonstrate their association with temporomandibular joint pain and dysfunction.

MR evidence of characteristics in symptomatic osteoarthritis of the temporomandibular joint: increased signal intensity ratio on proton density-weighted images of bone marrow in the mandibular condyle.

The purpose of this study was to clarify the presence of pain and a correlation between pain and characteristics of signal intensity of mandibular bone marrow in temporomandibular joints (TMJ) with osteoarthritis (OA). A total of 196 joints in 98 patients with TMJ disorders were examined using magnetic resonance imaging (MRI). A pain score and signal intensity on mandibular bone marrow were analyzed in the TMJ with OA. TMJ with OA showed a higher degree of pain compared to those without (p < 0.05). During opening, the joints in the higher signal intensity group showed a significantly higher degree of pain compared to the joints in the lower signal intensity group in those with OA on proton density weighted images (p < 0.05). It was concluded that TMJ with osteoarthritis is related to pain and that a symptomatic osteoarthritic TMJ can accompany bone marrow changes in the condyle, showing an increased signal on proton density weighted images.

Reliability of linear distance measurement for dental implant length with standardized periapical radiographs.

The purpose of this study was to investigate the accuracy of distance measurements of implant length based on periapical radiographs compared with that of other modalities. We carried out an experimental trial to compare precision in distance measurement. Dental implant fixtures were buried in the canine and first molar regions. These were then subjected to periapical (PE) radiography, panoramic (PA) radiography, conventional (CV) and medical computed (CT) tomography. The length of the implant fixture on each film was measured by nine observers and degree of precision was statistically analyzed. The precision of both PE radiographs and CT tomograms was closest at the highest level. Standardized PE radiography, in particular, was superior to CT tomography in the first molar region. This suggests that standardized PE radiographs should be utilized as a reliable modality for longitudinal and linear distance measurement, depending on implant length at local implantation site.

Cone-beam CT (CB Throne) applied to dentomaxillofacial region.

Cone-beam CT (CBCT) systems specifically designed for hard-tissue imaging of the maxillofacial region have recently become commercially available. The newly-developed CBCT system, CB Throne (Hitachi Medical Corp., Tokyo), is characterized by a number of features such as low dose, sub-millimeter spatial resolution, and a small footprint. This system has been clinically applied at Chiba Hospital, Tokyo Dental College, since April 2005. This article reports the characteristics of this system, and its diagnostic power for maxillofacial lesions and the pre-operative planning dental implants.

Comparison of accuracy of intravoxel incoherent motion and apparent diffusion coefficient techniques for predicting malignancy of head and neck tumors using half-Fourier single-shot turbo spin-echo diffusion-weighted imaging.

PURPOSE: To evaluate the use of the intravoxel incoherent motion (IVIM) technique in half-Fourier single-shot turbo spin-echo (HASTE) diffusion-weighted imaging (DWI), and to compare its accuracy to that of apparent diffusion coefficient (ADC) to predict malignancy in head and neck tumors. PATIENTS AND METHODS: HASTE DW images of 33 patients with head and neck tumors (10 benign and 23 malignant) were evaluated. Using the IVIM technique, parameters (D, true diffusion coefficient; f, perfusion fraction; D*, pseudodiffusion coefficient) were calculated for each tumor. ADC values were measured over a range of b values from 0 to 1000s/mm(2). IVIM parameters and ADC values in benign and malignant tumors were compared using Student's t test, receiver operating characteristics (ROC) analysis, and multivariate logistic regression modeling. RESULTS: Mean ADC and D values of malignant tumors were significantly lower than those of benign tumors (P<0.05). Mean D* values of malignant tumors were significantly higher than those of benign tumors (P<0.05). There was no significant difference in mean f values between malignant and benign tumors (P>0.05). The technique of combining D and D* was the best for predicting malignancy; accuracy for this model was higher than that for ADC. CONCLUSIONS: The IVIM technique may be applied in HASTE DWI as a diagnostic tool to predict malignancy in head and neck masses. The use of D and D* in combination increases the diagnostic accuracy in comparison with ADC.

Composition of the blood supply in the sublingual and submandibular spaces and its relationship to the lateral lingual foramen of the mandible.

OBJECTIVE: The purpose of this research was to contribute to minimizing arterial disruption during mandibular surgical procedures by clarifying the course of the arteries supplying the sublingual and submental regions. STUDY DESIGN: Heads of 75 human cadavers were dissected to identify the arterial supply of the sublingual and submental regions. Computed tomography scans were performed to visualize the lateral lingual foramina of the mandibles. RESULTS: The facial artery was found to contribute to the composition of almost half of the sublingual arteries studied. Furthermore, it was demonstrated that the arterial supply to an incisor tooth is often from the submental artery. CONCLUSIONS: Our data provide important information for coping with bleeding or hematoma occurring during surgical procedures in the mandibular region.

Analysis of elements in a minimal amount of temporomandibular joint fluid on fluid-attenuated inversion recovery magnetic resonance images.

OBJECTIVE: The aim of this study was to elucidate possible elements in minimal amounts of fluid (MF) in the temporomandibular joint by analyzing signal intensities in T2-weighted and fluid-attenuated inversion recovery (FLAIR) magnetic resonance (MR) images. STUDY DESIGN: Fifteen joints (15 patients) with MF were subjected to MR imaging to obtain T2-weighted and FLAIR images. Regions of interest were placed on MF, cerebrospinal fluid (CSF), and gray matter (GM), and their signal intensities were measured on both images. The signal intensity ratio (SIR) obtained by the signal intensity of GM between MF and CSF was compared in T2-weighted and FLAIR images. RESULTS: The average SIR of MF was lower than that of CSF on T2-weighted images, whereas it was higher on FLAIR images. The average suppression ratio of the signal intensity was lower for MF (24.1%) than for CSF (71.4%). CONCLUSIONS: MF may contain elements such as protein that are capable of inducing a shortened T1 relaxation time on MR images.