Isolable small-molecule cysteine sulfenic acid.

An isolable small-molecule cysteine sulfenic acid (Cys-SOH) protected by a molecular cradle was synthesized by direct oxidation of the corresponding cysteine thiol and its structure was established by X-ray crystallographic analysis. Studies on biologically relevant reactivity indicated its usefulness as a biorepresentative small-molecule sulfenic acid model.

Modeling of the Bioactivation of an Organic Nitrate by a Thiol to Form a Thionitrate Intermediate.

Thionitrates (R-SNO2) have been proposed as key intermediates in the biotransformation of organic nitrates that have been used for the clinical treatment of angina pectoris for over 100 years. It has been proposed and widely accepted that a thiol would react with an organic nitrate to afford a thionitrate intermediate. However, there has been no example of an experimental demonstration of this elementary chemical process in organic systems. Herein, we report that aryl- and primary-alkyl-substituted thionitrates were successfully synthesized by the reaction of the corresponding lithium thiolates with organic nitrates by taking advantage of cavity-shaped substituents. The structure of a primary-alkyl-substituted thionitrate was unambiguously established by X-ray crystallographic analysis.

Influence of voxel size and scan field of view on fracture-like artifacts from gutta-percha obturated endodontically treated teeth on cone-beam computed tomography images.

OBJECTIVE: To determine the optimal scan settings (scan mode and position of field of view [FOV]) for cone beam computed tomography to reduce root fracture-like artifacts that are often observed in teeth filled with gutta-percha cones (GPCs). STUDY DESIGN: Fracture-like artifacts that appeared on cone beam computed tomography images of 9 extracted human mandibular premolars filled with GPCs were analyzed using I-mode (FOV, 102 mm; voxel size, 0.2 mm) and D-mode (FOV, 51 mm; voxel size, 0.1 mm) settings. RESULTS: The artificial lines were more obvious in I-mode than in D-mode. Increased distance between the center of the FOV and the GPCs produced stronger artificial lines in both I-mode and D-mode. CONCLUSION: To reduce fracture-like artifacts, it is critical to use a mode with small voxel size and to place the target tooth in the center of the FOV.

Radiopacity Measurement of Restorative Resins Using Film and Three Digital Systems for Comparison with ISO 4049: International Standard.

This study compared Ultra Speed Occlusal Film (USOF) and 3 digital systems in determining the radiopacity of 5 different restorative resins in terms of equivalents of aluminum thickness. Whether those digital systems could be used to determine whether radiopacity was in line with International Organization for Standardization (ISO) recommendations was also investigated. Disks of each of 5 restorative resins and an aluminum step wedge were exposed at 65 kVp and 10 mA on USOF and imaged with each digital system. Optical density on the film was measured with a transmission densitometer and the gray values on the digital images using Image J software. Graphs showing gray value/optical density to step wedge thickness were constructed. The aluminum equivalent was then calculated for all the resins using a regression equation. All the resins were more radiopaque than 1 mm of aluminum, and therefore met the ISO 4049 recommendations for restorative resins. Some resins showed statistically higher aluminum equivalents with digital imaging. The use of traditional X-ray films is declining, and digital systems offer many advantages, including an easy, fast, and reliable means of determining the radiopacity of dental materials.

Root canal filling materials spread pattern mimicking root fractures in dental CBCT images.

OBJECTIVE: To clarify the cause of artificial tooth-root fracture lines in cone beam computed tomography (CBCT) images caused by root canal filling materials and to enhance the diagnostic performance of CBCT. STUDY DESIGN: We analyzed the CBCT images of 18 extracted human teeth (9 upper central incisors and 9 lower premolars) that were filled with a size 50 gutta-percha cone and inserted into tooth sockets in a human skull. RESULTS: The CBCT images of the incisors displayed artificial lines in the oblique directions, notably the mesiobuccal, distolingual, distobuccal and mesiolingual directions, but only rarely in the cross-directions (buccal, lingual, mesial, and distal). In the premolars, the reverse was true, with lines mainly in the cross-directions, mesial and distal directions particularly. The lines were predominantly at the cervical slice. CONCLUSIONS: Artifacts resulting from root filling material appear along the long axis of the alveolar bones, and resemble root fractures.

Characteristic findings on panoramic radiography and cone-beam CT to predict paresthesia after extraction of impacted third molar.

The purpose of this study was to compare findings on the relationship between impacted molar roots and the mandibular canal in panoramic and three-dimensional cone-beam CT (CBCT) images to identify those that indicated risk of postoperative paresthesia. The relationship between impacted molars and the mandibular canal was first classified using panoramic images. Only patients in whom the molar roots were either in contact with or superimposed on the canal were evaluated using CBCT. Of 466 patients examined using both panoramic and CBCT images, 280 underwent surgical extraction of an impacted molar, and 15 of these (5%) reported postoperative paresthesia. The spatial relationship between the impacted third molar root and the mandibular canal was determined by examining para-sagittal sections (lingual, buccal, inter-radicular, inferior, and combinations) obtained from the canal to the molar root and establishing the proximity of the canal to the molar root (in contact with or without loss of the cortical border and separate). The results revealed that darkening of the roots with interruption of the mandibular canal on panoramic radiographs and the inter-radicular position of the canal in CBCT images were characteristic findings indicative of risk of postoperative paresthesia. These results suggest that careful surgical intervention is required in patients with the above characteristics.

Effect of display monitor devices on intra-oral radiographic caries diagnosis.

OBJECTIVES: Recent developments in digital computer technology have enabled radiological diagnosis to be performed using a monitor screen. In medical radiography, the importance of monitors has been shown in many diseases. Digital imaging and communication in medicine (DICOM)-compatible monitors are widely used. However, the effect of monitors on the diagnosis of oral disease has not yet been clarified and remains controversial. The aims of this study are to compare the caries diagnostic ability between DICOM monitors and other monitors and to examine if monitor capability affects the diagnosis. MATERIALS AND METHODS: One hundred proximal surfaces of 50 extracted human upper premolar teeth were used as specimens. Intra-oral radiographs of all specimens were taken digitally. Three types of monitors were compared in terms of caries diagnostic ability: a DICOM standard-compatible monitor, a standardized personal computer (PC) monitor, and a tablet PC. Six oral radiologists diagnosed each radiograph independently. Areas under the receiver operating characteristic (ROC) curve were generated and compared. RESULTS: Area under the ROC curve (AUC) of the DICOM monitor, PC monitor, and tablet PC was 0.68147, 0.67002, and 0.60189, respectively. There was no significant difference between the DICOM monitor and the PC monitor, but the tablet PC showed significantly lower accuracy. There were no significant differences among the monitors for dentin caries (p > 0.05). CONCLUSIONS: DICOM-compatible monitors and PC monitors have similar capabilities, but tablet PCs showed lower diagnostic accuracy, especially for superficial caries. CLINICAL RELEVANCE: Appropriate monitors are needed for radiographic diagnosis on monitor screens.

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.

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.

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.

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.

Relationships between third-molar juxta-apical radiolucencies and mandibular canals in panoramic and cone beam computed tomography images.

OBJECTIVE: This study aimed to determine the relationship between third-molar juxta-apical radiolucencies and mandibular canals on panoramic and cone beam computed tomography (CBCT) images. STUDY DESIGN: Forty-two patients were included in this retrospective study. The root apices and the relationships of the juxta-apical radiolucencies to the mandibular canals were evaluated on both panoramic and CBCT images. The McNemar test (P < .05) was used to compare panoramic with CBCT findings. RESULTS: Root apices were visualized clearly with CBCT in most cases for which the apices were not seen clearly on panoramic images. Similarly, juxta-apical radiolucencies were separate from the mandibular canals with CBCT in most cases. CONCLUSIONS: The present study found that there is no consistent intimate relationship between juxta-apical radiolucencies and the mandibular canals. Similar studies with larger sample sizes are required to further confirm these findings.

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.

Potential of fluid-attenuated inversion recovery MRI as an alternative to contrast-enhanced MRI for oral and maxillofacial vascular malformations: experimental and clinical studies.

OBJECTIVE: To determine the potential of fluid-attenuated inversion recovery (FLAIR) imaging of oral and maxillofacial vascular malformations as an alternative to contrast-enhanced magnetic resonance imaging (MRI), we investigated the influence of differences in T1 and T2 values on image contrast in FLAIR images and evaluated the diagnostic utility of such images. STUDY DESIGN: FLAIR imaging and heavily T2-weighted (hT2-weighted) imaging were performed using a phantom. FLAIR and hT2-weighted images of 32 lesions (11 mucous cysts, 12 vascular malformations, and 9 tumors) were also studied retrospectively. The contrast-to-noise ratios (CNRs) and CNR change ratios were compared. RESULTS: All aqueous solutions except those with a short T2 value were discriminated by CNR change ratio (P < .05). All 3 types of lesions were discriminated by CNR change ratio (P < .05). CONCLUSION: FLAIR imaging has potential as an alternative to contrast-enhanced MRI in differentiating vascular malformations from other types of lesions in the oral and maxillofacial region.

Imaging findings of benign peripheral nerve sheath tumor in jaw.

OBJECTIVE: The aim of this study was to investigate the imaging characteristics of peripheral nerve sheath tumors (PNSTs) in the jaw. STUDY DESIGN: Imaging studies of 6 patients were retrospectively reviewed. Conventional radiography, computed tomography, and magnetic resonance imaging were performed in all patients. RESULTS: A fusiform lesion continuous with the nerve was observed in 2 cases, with the tumor arising within the inferior alveolar canal. In the other 4 cases, with the tumor arising outside the canal, the tumor had protruded and eroded into the bone. Protrusion was also present in 1 of the 2 cases, with the tumor arising within the canal. A target or fascicular sign was observed each in 1 case. CONCLUSIONS: A fusiform lesion continuous with the nerve and a target or fascicular sign was only present in a few cases. The PNSTs, however, showed a tendency to protrude into the bone.

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.

Comparison of various methods for quantification of apparent diffusion coefficient of head and neck lesions with HASTE diffusion-weighted MR imaging.

OBJECTIVES: The purposes of this retrospective study were to compare various methods of apparent diffusion coefficient (ADC) measurement for head and neck lesions in half-Fourier single-shot turbo spin-echo (HASTE) diffusion-weighted imaging (DWI) and determine the threshold ADC value for predicting malignancy. STUDY DESIGN: HASTE DW images of 46 lesions (10 cysts, 14 benign tumors, and 22 malignant tumors) were studied retrospectively. The ADC values were compared among the 0-1000 method, 500-1000 method, and weighted linear regression (WLR) fit. RESULTS: The highest overall accuracies of 83.3%, 86.1%, and 88.9% were obtained when ADC values of 1.24 × 10(-3) mm(2)/s (0-1000 method), 0.98 × 10(-3) mm(2)/s (500-1000 method), and 1.23 × 10(-3) mm(2)/s (WLR fit), respectively, were used for the threshold. CONCLUSIONS: The present results indicate that ADC measurement with HASTE DWI is useful in predicting malignancy of head and neck lesions.

Non-Hodgkin lymphoma involving the mandible: imaging findings.

OBJECTIVE: The aim of this study was to investigate the imaging findings of non-Hodgkin lymphoma (NHL) involving the mandible. STUDY DESIGN: The imaging studies of 4 patients with NHL involving the mandible were retrospectively reviewed. Panoramic and computerized tomographic (CT) images were available for all patients. Magnetic resonance imaging (MRI) was available for 3 patients. RESULTS: On panoramic images, an apparent radiolucent lesion was found in only 2 of 4 cases. However, in all cases careful observation demonstrated imaging findings suggesting malignancy. On CT and MRI, tumor replaced the bone marrow in all cases and spread to the surrounding soft tissue in 3 cases. Cortical bone destruction tended to be mild for the extent of tumor involvement. CONCLUSIONS: NHL involving the mandible tended to show slight or mild cortical bone destruction relative to the extent of the tumor involvement. Careful observation was considered to be necessary when interpreting conventional images, because they might not clearly demonstrate bone destruction.

[Weighted-averaging multi-planar reconstruction method for multi-detector row computed tomography].

Development of multi-detector row computed tomography (MDCT) has enabled three-dimensions (3D) scanning with minute voxels. Minute voxels improve spatial resolution of CT images. At the same time, however, they increase image noise. Multi-planar reconstruction (MPR) is one of effective 3D-image processing techniques. The conventional MPR technique can adjust slice thickness of MPR images. When a thick slice is used, the image noise is decreased. In this case, however, spatial resolution is deteriorated. In order to deal with this trade-off problem, we have developed the weighted-averaging multi-planar reconstruction (W-MPR) technique to control the balance between the spatial resolution and noise. The weighted-average is determined by the Gaussian-type weighting function. In this study, we compared the performance of W-MPR with that of conventional simple-addition-averaging MPR. As a result, we could confirm that W-MPR can decrease the image noise without significant deterioration of spatial resolution. W-MPR can adjust freely the weight for each slice by changing the shape of the weighting function. Therefore, W-MPR can allow us to select a proper balance of spatial resolution and noise and at the same time produce suitable MPR images for observation of targeted anatomical structures.