Pipop Sutthiprapaporn

The reliability of computed tomography (CT) values and dimensional measurements of the oropharyngeal region using cone beam CT: comparison with multidetector CT

OBJECTIVES To evaluate the reliability of cone beam CT (CBCT) values and dimensional measurements of oropharyngeal air spaces as compared with those of multidetector row CT (MDCT). METHODS A soft tissue equivalent phantom with different sized holes was used. The phantom was scanned using CBCT and MDCT. In addition, a volunteer was examined using both methods for clinical comparison. The CT data were retrieved to a personal computer and treated using image processing software for three-dimensional rendering and dimensional measurements. The CT values of air, water and soft tissues were measured experimentally and the CT values of air, fat and muscle were measured in a clinical case. The diameter of each hole drilled in the phantom was measured on CBCT and MDCT images using the software tool and digimatic callipers. RESULTS The CBCT values were quite different from the Hounsfield units obtained with a typical MDCT system. The standard deviations were almost ten times larger with CBCT. In vivo assessment showed that the CBCT values for fat had a wide range that partially overlapped the values for muscle. The measurement of distances greater than 4 mm was consistent for all methods. The difference for holes was less than 0.2 mm. CONCLUSIONS The phantom study showed that CBCT provides limited quantitative CT values for each pixel on sliced images for differentiating air, water and soft tissues. However, the measurement of air spaces with CBCT was quite accurate.

Positional changes of oropharyngeal structures due to gravity in the upright and supine positions

OBJECTIVES To compare the responses of oropharyngeal structures to gravity while sitting upright or lying down in a supine position. METHODS Seven subjects were evaluated by cone beam CT (CBCT) while in the upright position and by a four-row multidetector helical CT (MDCT) while in the supine position. All of the voxel sizes were adjusted to be 0.3x0.3x0.3 mm3 in the x-y-z axis. The posterior nasal spine, basion and fourth cervical bone were used as references to measure positional changes in the oropharyngeal structures between the upright and supine positions. The smallest areas in the oropharynx were also evaluated. RESULTS The soft palate, epiglottis and entrance of the oesophagus moved caudally with the positional change from supine to sitting upright, and moved posteriorly when the position changed from an upright to a supine position. The hyoid bone moved caudally but not posteriorly in response to the same positional changes. The width and length of the smallest area present in the oropharynx was larger in the upright position than in the supine position. CONCLUSIONS Gravity can produce movements in oropharyngeal structures in response to postural changes between sitting upright and lying in the supine position.

Improved inspection of the lateral pharyngeal recess using cone-beam computed tomography in the upright position

ObjectivesTo evaluate the structure of the lateral pharyngeal recess (LPR) and surrounding structures in computed tomography (CT) images obtained from subjects in the supine and upright positions.MethodsSix subjects were evaluated using cone-beam CT (CBCT) in the upright position, and with a four-row multidetector helical CT (MDCT) in the supine position. All of the voxel sizes were adjusted to 0.3 × 0.3 × 0.3 mm3 in the x, y, z coordinate system. The posterior nasal spine and basion were used as references. The LPR and surrounding structures were measured and compared in the two different modalities.ResultsIn 83% of the cases, the LPR was deeper when the position was changed from supine to upright.ConclusionsOur results suggest that imaging of the LPR using CBCT with the subject in the upright position is superior to that using MDCT with the subject in the supine position.

A morphological comparison of the piriform sinuses in head-on and head-rotated views of seated subjects using cone-beam computed tomography

ObjectivesFood flow in the oropharynx changes when the head is rotated. The purpose of this study was to evaluate morphological differences in the upper and lower piriform sinuses in head-on (HO) versus head-rotated (HR) positions.MethodsTen healthy adult volunteers with no previous history of dysphagia were subjected to cone-beam computed tomography (CBCT) in the HO and HR positions. Binary CBCT images were created at 50% gray scale to examine morphological changes in the lower piriform sinuses.ResultsUpon rotation to the right, the cross-sectional area of the left lower piriform sinus increased significantly (P = 0.037). The depth of the right lower piriform sinus also increased significantly (P = 0.011) upon rotation. The volume of the lower piriform sinuses increased significantly on both sides (right, P = 0.009; left, P = 0.013). The upper piriform sinuses acquired a teardrop shape, with the rotated side narrowed and opposite side enlarged.ConclusionsThese results suggest that changes in food flow during head rotation result mainly from changes in the size and shape of the upper piriform sinuses.

Cone-beam computed tomography evaluation of curved root canals prepared using reciprocal rotary files and rotational rotary files

Aim: The aim of this study is to compare curved root canal preparation between reciprocal rotary files and rotational rotary files in extracted teeth using cone-beam computed tomography (CBCT). The independent variable was the file type (reciprocal vs. rotary), and the primary outcome variable was the centering ratio of distance change after canal preparation. Secondary outcomes were canal transportation in extension and direction and the preparation time. Materials and Methods: Forty mesial root canals from extracted permanent molars with curvatures ranging between 25° and 45° were randomly divided into 4 groups. Canals were prepared with two types of reciprocal rotary files (WaveOne and Reciproc) and two types of rotational rotary files (ProTaper and Mtwo), ten canals in each group. The root canals were scanned before and after preparation using CBCT. Group differences in outcome variables were tested using ANOVA and 5% type I error probability. Results: At the middle third of canals, reciprocal rotary files yielded the least amount of deviation from the center in inner–outer furcal direction (P < 0.001). Transportation was shown from the original canal shape in all directions in four groups. The reciprocal rotary files took the least amount of preparation time as well (P < 0.001). Conclusions: Reciprocal files result in less transportation and working time than the rotational files.