Mamoru Wakoh

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 Students 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.

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

Abstract 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.

Suitability of the general-purpose graphic printer as an image output device for digital dental x-ray images.

OBJECTIVES The purpose of this study was to evaluate the suitability of the general-purpose graphic printer as an image output device for digital dental x-ray images. METHODS The image quality as obtained by a thermal printer and by a dye sublimation printer was investigated. A grid pattern image was used to check parallelism and verticality of lines in each hard copy. A step-wedge image was printed with each printer, and the optical density, gradient, and root mean square granularity were compared. Depiction ability was also compared by using test images, including small signals. RESULTS All of the lines were parallel and vertical on hard copies of both printers. The dye sublimation printer showed better results on optical density, gradient, root mean square granularity, and depiction ability. CONCLUSION The dye sublimation printer produces images of the depiction ability comparable to the cathode ray tube display and seems suitable as an image output device for digital dental x-ray images.

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

AbstractObjectivesEdema 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.MethodsThe 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.ResultsSignal 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.ConclusionsThe 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.

Computed Dental Radiography System versus Conventional Dental X-ray Films for Detection of Simulated Proximal Caries

The diagnostic accuracy of intraoral images obtained with a first generation Computed Dental Radiography (CDR) digital dental imaging system is compared with the diagnostic accuracy of conventional dental x-ray film images using a receiver operating characteristics (ROC) analysis. Fifteen dentition phantoms were constructed. Each contained 4 teeth, consisting of premolar and molar teeth with 6 proximal surfaces. Mechanical defects were created randomly on the proximal surfaces and plugged with dentine powder to simulate caries. Fifteen images of each modality were rated by nine dentists in separate sessions according to their confidence in their ability to detect the simulated caries. The images examined were as follows: original CDR images, CDR images magnified 2×, CDR images magnified 4 ×, Ektaspeed Plus dental x-ray film images, and Ultraspeed dental x-ray film images, both unmagnified and magnified 2 ×. A series of ROC curves indicated the limited usefulness of magnification for the CDR system, and consistently similar success in detecting simulated proximal caries for original CDR images and original film images. The magnification of original film images did not always promote greater success than that obtained with the original film images.

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.

A sensitometric comparison of Kodak Ektavision and Fuji Super HR-S panoramic radiographic films

OBJECTIVES The purpose of this study was to compare the combination of Ektavision film and Ektavision intensifying screen with the combination Super HR-S panoramic radiographic film and HR-4 intensifying screen with respect to sensitometric properties and the visualization of anatomic structures. METHODS The density response and resolution of both panoramic radiographic film/intensifying screen combinations were evaluated through use of the generated characteristic curves and the modulation transfer function. The diagnostic clarity was evaluated by five oral and maxillofacial radiologists who used a rating scale to evaluate the image clarity of selected anatomic structures. RESULTS The film speed and radiographic contrast, respectively, were 1.3 and 1.2 times higher for Ektavision than for Super HR-S. The image resolution with Ektavision was similar to that with Super HR-S. Ektavision was perceived to provide clearer images of the selected anatomic details than did Super HR-S. CONCLUSION With respect to the clarity of anatomic structures, Ektavision film, with its higher speed and higher contrast, proved superior to Super HR-S film.

Image interpretation for squamous cell carcinoma of Stensen duct

A case of squamous cell carcinoma presumed to have arisen from the right Stensen duct is reported. The patient, a 62-year-old man, was referred to our hospital with swelling in the right cheek. Magnetic resonance imaging (MRI), including contrast-enhanced MRI, and contrast-enhanced computerized tomography (CECT) enabled diagnosis of a solitary mass in the Stensen duct. Fat-suppressed T(2)-weighted imaging, in particular, demonstrated a mass-like lesion in the dilated Stensen duct and obstructive parotitis where the duct transitions into the parotid gland. Gadolinium-DTPA-enhanced T(1)-weighted imaging demonstrated the mass-like lesion surrounded by signal-hyperintense layer showing continuous transition from the thickened Stensen duct wall, which was also hyperintense. The CECT revealed peripheral annular enhancement surrounding the tumorous mass, with no enhancement of the duct wall itself, reflecting an increase in micro blood vessels in the stroma of the neoplasm. These image findings correlated well with subsequent histopathologic findings. A mass with rim enhancement and dilated Stensen duct accompanied by parotitis and no salivary calculus may suggest a differential diagnosis of malignant tumor of Stensen duct.

Tuned-Aperture Computed Tomography (TACT®) to assess impacted teeth using 2D slices and 3D pseudo-holograms

The purpose of this clinical study was to compare the diagnostic information yield of interactive TACT 3D pseudo-holograms, 2D TACT slices and conventional dento-alveolar images for the imaging and localization of impacted maxillary incisor teeth.

Dose Response of Two Storage-Phosphor Systems for Intra-Oral Radiography

We evaluated the dose response of two storage-phosphor systems, DenOptix and Digora, for intra-oral radiography. Dose response curves were generated using uniform flat field exposure. The dynamic range of both systems was assessed. Root mean square (RMS) granularity curves were also generated to compare noise levels at different exposures. For DenOptix, curves were obtained by activating and inactivating the automatic range control (ARC) setting. For Digora, curves were generated at different calibration exposures. Moreover, tube voltage and tube current dependencies in both systems were examined.In the dose response curve of the DenOptix with the activated ARC setting, the pixel value was kept almost constant regardless of exposure. The dose response curve of the Digora was changed by the different calibration exposures. The curves at relatively large calibration exposures had inflection points and the pixel value gradually decreased at exposures higher than the inflection points. These results clearly show that the DenOptix with the activated ARC setting, as well as the Digora, can produce images with identical density, regardless of exposure. The dynamic range of both storage-phosphor systems was significantly greater than that of CCD-based systems. With both DenOptix and Digora, higher exposure decreased relative noise levels. The sensitivity of both systems increased with higher tube voltage, although tube current dependency was not observed. Both systems allow for a dose reduction due to a high tube voltage.