A Novel Imaging Technique for Analyzing Condylar Movement During Mastication in Patients With Jaw Deformities: Four-Dimensional Computed Tomography.

OBJECTIVE: This study aimed to reveal characteristic condylar movements in patients with jaw deformities. STUDY DESIGN: Thirty patients with jaw deformities before surgery were enrolled and instructed to chew a cookie during 4-dimensional computed tomography (4DCT). The distance between the most anterior and posterior positions of the bilateral condyles on 4DCT images was measured and compared among patients with different skeletal classes. Correlations between the condylar protrusion and cephalometric values were also determined. RESULTS: The distances of condylar protrusion during mastication were significantly greater in the skeletal class II group than in the skeletal class III group ( P =0.0002). Significant correlations were found between the distances of condylar protrusion during mastication and the sella-nasion-B point angle ( r =-0.442, P =0.015), A point-nasion-B point angle ( r =0.516, P =0.004), sella-nasion plane to ramus plane angle ( r =0.464, P =0.01), sella-nasion plane to occlusal plane angle ( r =0.367, P =0.047), and condylion-gonion length ( r =-0.366, P =0.048). CONCLUSION: Motion analysis with 4DCT images revealed that condylar movement in patients with retrognathism was larger than in patients with mandibular prognathism. Skeletal structure was therefore correlated with condylar movement during mastication.

Four-Dimensional Computed Tomographic Image Evaluation of the Change of Condylar Movement With and Without Implant-Supported Removable Prostheses in the Fibular Mandible: A Pilot Case Series Report.

Implant-supported removable prostheses (ISrP) improve the quality of life, especially in patients who underwent mandibular reconstruction, but few studies have focused on the effect of ISrP in the fibular mandible on the function of the temporomandibular joint. The purpose of this pilot case series was to determine the usefulness of four-dimensional computed tomography (4DCT) images for the evaluation of differences in condylar movements with and without ISrP. Three patients who underwent ISrP following segmental mandibulectomy and free-flap reconstruction were evaluated. The participants were instructed to masticate a cookie during the 4DCT scan. The distance between the most anterior and posterior positions of the condyles on the sagittal view of the 4DCT images during the chewing of the cookies was measured and compared with and without ISrP. 4DCT revealed changes in the distances of condylar protrusion with and without wearing ISrP, but there were no obvious differences among the three patients. The 4DCT motion analysis was useful for the evaluation of the effect of wearing ISrP on condylar movements during mastication in patients with mandibular reconstruction and may become a useful objective evaluation method for the functional evaluation of ISrP.

Axial four-dimensional computed tomographic images to analyze crosswise differences in protrusive condylar movement in patients who underwent mandibulectomy and free flap reconstruction.

OBJECTIVE: Few studies evaluate condylar movement following mandibular reconstruction. The main objective of this study was to show that axial four-dimensional computed tomography (4DCT) could visualize bilateral protrusive condylar movement directly. We used axial 4DCT images to assess condylar protrusion in patients who underwent mandibular reconstruction. METHODS: We enrolled seven healthy volunteers (median age 30 years, range 27-38 years) and seven patients (median age 65 years, range 52-80 years), who underwent mandibulectomy (segmental in five, hemi in one, marginal in one) and free flap reconstruction (using the fibula in six and the radial forearm in one). Six study subjects were instructed to masticate a cookie during the 4DCT scan (the seventh made chewing motions). The distance between the most anterior and posterior positions of the bilateral condyles on 4DCT (axial view) images was then measured and compared between controls and patients using the Mann-Whitney U-test. RESULTS: The crosswise difference in the distances of condylar protrusion was significantly greater in patients than in the controls. CONCLUSION: Axial 4DCT images can visualize a bilateral condylar protrusive path. Axial 4DCT images for patients who have undergone mandibulectomy and reconstruction may be useful for evaluation of functional movement of condyles.

Four-dimensional computed tomography evaluation of jaw movement following mandibular reconstruction: A pilot study.

PURPOSE: The purpose of this study was to analyze jaw movement during mastication in patients who underwent mandibular reconstruction following segmental mandibulectomy, including mouth opening and mastication time, based on four-dimensional computed tomography (4D CT) images. MATERIAL AND METHODS: This study included six surgical patients, who underwent segmental mandibulectomy and simultaneous reconstruction with a free fibula osteocutaneous flap, and four controls. 4D CT was performed during mastication of a cookie to evaluate the movement of the jaw during natural function. The maximum mouth opening, mastication time, and movement of the mandibular angle during mastication were evaluated from the 4D CT images. RESULTS: 4D CT images enabled visualization of jaw movement during mastication. When compared with the controls, the maximum mouth opening during mastication and excursion of the mandibular angle, especially on the diseased side, tended to decrease in surgical patients; however, this did not occur with mastication time. The numerical differences between the diseased and nondiseased side in surgical patients tended to be higher than the crosswise differences in controls. CONCLUSION: 4D CT images revealed differences in jaw function between patients who underwent mandibular reconstruction and controls. 4D CT could be used to evaluate postoperative outcomes following mandibular reconstruction.

Hepatic CT perfusion measurements: a feasibility study for radiation dose reduction using new image reconstruction method.

OBJECTIVES: To assess the effects of image reconstruction method on hepatic CT perfusion (CTP) values using two CT protocols with different radiation doses. MATERIALS AND METHODS: Sixty patients underwent hepatic CTP and were randomly divided into two groups. Tube currents of 210 or 250 mA were used for the standard dose group and 120 or 140 mA for the low dose group. The higher currents were selected for large patients. Demographic features of the groups were compared. CT images were reconstructed by using filtered back projection (FBP), image filter (quantum de-noising, QDS), and adaptive iterative dose reduction (AIDR). Hepatic arterial and portal perfusion (HAP and HPP, ml/min/100ml) and arterial perfusion fraction (APF, %) were calculated using the dual-input maximum slope method. ROIs were placed on each hepatic segment. Perfusion and Hounsfield unit (HU) values, and image noises (standard deviations of HU value, SD) were measured and compared between the groups and among the methods. RESULTS: There were no significant differences in the demographic features of the groups, nor were there any significant differences in mean perfusion and HU values for either the groups or the image reconstruction methods. Mean SDs of each of the image reconstruction methods were significantly lower (p<0.0001) for the standard dose group than the low dose group, while mean SDs for AIDR were significantly lower than those for FBP for both groups (p=0.0006 and 0.013). Radiation dose reductions were approximately 45%. CONCLUSIONS: Image reconstruction method did not affect hepatic perfusion values calculated by dual-input maximum slope method with or without radiation dose reductions. AIDR significantly reduced images noises.

[Development of automatic window level and width-setting system for abdominal CT scanning].

Window setting is a very important technique in CT examinations. However, most beginner technologists have difficulty in setting the optimal window. Now, thanks to technical progress, it is easy to obtain a great many CT images. On the other hand, it is impossible to provide the optimal window setting for all images. Therefore, our purpose is to offer optimal CT images for every patient by using the automatic window-level and width-setting system. As a result of this experiment, there was a considerable difference in window setting by an expert technologist and that by a beginner technologist. With our system, we were able always to obtain an optimal window setting, such as that set by an expert technologist, regardless of the CT experience of the radiological technologist. We think that this system will be effective in observing animated examinations even if film is no longer used in the future.

[Results of a questionnaire survey on window setting and FOV on CT images of examinations].

The use of CT as a general examination has spread widely and is even used in small institutions. However, it is difficult to determine the current situation of each institution. Therefore, we employed a questionnaire to investigate the current situation of a variety of institutions. From the results of the questionnaire, we determined that the window setting was difficult for beginner technologists. In addition, in many institutions, radiological technologists did not always use the same display FOV for the same patient. From this questionnaire, we were able to determine the present conditions in each institution. We consider these results very useful.