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.

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.

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.

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.

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.

A case of zoster sine herpete of the trigeminal nerve.

Varicella-zoster virus reactivation causes zoster (shingles), a syndrome characterized by severe pain and a vesicular rash. The present report details a case of varicella-zoster virus reactivation of the maxillary and mandibular division of the right trigeminal nerve without evidence of vesicular rash (zoster sine herpete). It is difficult to identify owing to no typical clinical signs such as vesicular eruption. Zoster sine herpete of the trigeminal nerve, in particular, is rarely reported. In this case, the diagnosis was based on clinical findings and was supported by the demonstration of an immunoglobulin G antibody. Zoster sine herpete of the trigeminal nerve, in particular, should be considered in patients with severe facial pain over specific dermatomes, if they do not demonstrate appreciable findings of traumatic neuropathy, tumor or herpes zoster.

Osteosarcoma of maxilla with unusual image findings in child.

Osteosarcoma of the head and neck is relatively rare and accounts for less than 10 percent of all osteosarcomas in general. We report a case of osteosarcoma in which imaging and histopathology of the hard palate of an 11-year-old boy yielded atypical findings. An approximately 8×15mm lesion found in the center of the palate was hard and healthy in color. Subsequent biopsy resulted in a diagnosis of nonepithelial malignant tumor. No abnormalities were observed in the maxillary bone or tooth on panoramic or occlusal radiographs. Computed tomography images revealed a mass lesion approximately 7×9×9mm in size on the hard palate extending into the maxilla. The cortex of the maxilla adjacent to the lesion was unclear in parts. The internal structures were slightly inhomogeneous and its density was lower than that of muscle. On magnetic resonance images, the lesion was represented by low signal intensity on T1-weighted (T1W) images and high signal intensity on T2-weighted images with fat-suppression. The margin of the lesion was a little unclear and the internal structures were slightly inhomogeneous. The lesion was enhanced homogeneously on post-contrast T1W images with fat-suppression. The histopathological diagnosis was fibrogenesis-type osteosarcoma. No findings specific to osteosarcoma such as localized enlargement of the periodontal ligament space alongside the root, cortical destruction, periosteal ossification or osteogenesis were found in this case.

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.

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.

Fat suppression with short inversion time inversion-recovery and chemical-shift selective saturation: a dual STIR-CHESS combination prepulse for turbo spin echo pulse sequences.

PURPOSE: To test a newly developed fat suppression magnetic resonance imaging (MRI) prepulse that synergistically uses the principles of fat suppression via inversion recovery (STIR) and spectral fat saturation (CHESS), relative to pure CHESS and STIR. This new technique is termed dual fat suppression (Dual-FS). MATERIALS AND METHODS: To determine if Dual-FS could be chemically specific for fat, the phantom consisted of the fat-mimicking NiCl(2) aqueous solution, porcine fat, porcine muscle, and water was imaged with the three fat-suppression techniques. For Dual-FS and STIR, several inversion times were used. Signal intensities of each image obtained with each technique were compared. To determine if Dual-FS could be robust to magnetic field inhomogeneities, the phantom consisting of different NiCl(2) aqueous solutions, porcine fat, porcine muscle, and water was imaged with Dual-FS and CHESS at the several off-resonance frequencies. To compare fat suppression efficiency in vivo, 10 volunteer subjects were also imaged with the three fat-suppression techniques. RESULTS: Dual-FS could suppress fat sufficiently within the inversion time of 110-140 msec, thus enabling differentiation between fat and fat-mimicking aqueous structures. Dual-FS was as robust to magnetic field inhomogeneities as STIR and less vulnerable than CHESS. The same results for fat suppression were obtained in volunteers. CONCLUSION: The Dual-FS-STIR-CHESS is an alternative and promising fat suppression technique for turbo spin echo MRI.

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.

Effects of dose reduction on multi-detector computed tomographic images in evaluating the maxilla and mandible for pre-surgical implant planning: a cadaveric study.

OBJECTIVE: To assess effects of dose reduction on image quality in evaluating maxilla and mandible for pre-surgical implant planning using cadavers. MATERIALS AND METHODS: Six cadavers were used for the study using multi-detector computed tomography (CT) operated at 120 kV and the variable tube current of 80, 40, 20 and 10 mA. A slice thickness of 0.625 mm and pitch 1 were used. Multi-planar images perpendicular and parallel to dentitions were created. The images were evaluated by five oral radiologists in terms of visibility of the anatomical landmarks including alveolar crest, mandibular canal, floors of the maxillary sinus and nasal cavity, contours/cortical layer of jaw bones and the details of trabecular bone. Observers were asked to determine the quality of the images in comparison with 80 mA images based on the criteria: excellent, good, fair or non-diagnostic. The average scores of all observers were calculated for each specimen in all exposure conditions. RESULTS: The 40 mA images could visualize such landmarks and were evaluated to be same or almost equivalent in quality to the 80 mA images. Even the 20 mA images could be accepted just for diagnostic purpose for implant with substantial deterioration of the image quality. The 10 mA images may not be accepted because of the obscured contour caused by image noise. CONCLUSION: Significant dose reduction by lowering mA can be utilized for pre-surgical implant planning in multi-detector CT.

Automatic segmentation of teeth from dentomaxillofacial 3D-CT images.

CT is an effective tool for image diagnosis because it enables noninvasive observation of internal organs. In the course of CT, 3D-CT, such as a helical scanning CT and a multi-detector row CT, has been developed. With the use of 3D-CT, organs can be observed from several viewing directions. Even now, however, 3D-CT images are generated by manual procedures to extract objective organs using the threshold method. These procedures waste time and effort. Therefore, development of highly automated and effective extracting techniques has been desired. The region growing (RG) method is one of the effective techniques of extracting internal organs. The conventional RG method, however, has some defects. Extracted regions are strongly affected by the threshold value for segmentation. A break point on a region contour yields a leakage of region. To overcome these defects, we formulated a modified region growing method with edge detection (MRGWED) which combines a three-dimensional region growing technique and an edge detection technique. Using the MRGWED, we tried to extract teeth from dentomaxillofacial 3D-CT image data.

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.

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.

CT image applications for pre-surgical assessment and surgical pre-planning in Pediatric Dentistry.

In this study we focused on dental anomalies peculiar to children and investigated how 3D-surgical planning and simulation could be applied to each case. This study included 3 patients (2 female and 1 male, 8 to 12 years). The CT imaging was performed via a SOMATOM Plus4. From the resulting data, an image of the tooth and bone was rendered using image analysis software Amira 3.1 which was then used to reconstruct three-dimensional images. The reconstructed 3D images were imported to 3D modeling software, which provided the basis for the surgical simulations. From these results, we were able to gain important insights that helped shape the planning of the surgical operation. Furthermore we consider that these findings would be useful for the patient when taking them through the process of obtaining informed consent.

Static MR images for diagnosis of swallowing.

Evaluation of swallowing has been made possible by cine-Magnetic resonance (MR) imaging with high time resolution. However, the spatial resolution in cine-MR imaging remains inadequate for the detection of anatomical structures. Therefore, it is necessary to refer to static MR images in conjunction with cine-MR imaging. The aim of this study was to determine which MR parameters were appropriate for static imaging of the anatomical structures involved in swallowing. MR imaging was carried out, and T1-weighted, T2-weighted and proton-density-weighted MR images were obtained in the sagittal plane in 5 healthy volunteers. Each image was evaluated for anatomic landmark clarity by 3 oral radiologists. The anatomic landmarks selected were the lip, tip of tongue, center of tongue, tongue base, soft palate and epiglottis. Differences in clarity among 3 imaging modalities were evaluated. A 3-point score rating system was used. The results showed that lower TE sequences, i.e., either T1-weighted or proton-density-weighted images, were the most suitable for use in conjunction with cine-MR imaging in diagnosing swallowing disorders.