Our aim in this study was to evaluate hyoid bone movement trajectories and the age-related changes during swallowing in healthy subjects by ultrasonography. Data were obtained from 30 healthy volunteers (15 men, 15 women) in three age groups (20-39, 40-59, 60-79 years). The subjects were examined while sitting in an upright position, with the back against a wall to control movement. The transducer was placed in a longitudinal scan above the larynx. The subjects were then given 5 mL of mineral water. The water bolus was held in their mouth until they were forced to do a rapid swallow. The imaging was repeated five times for averaging. The movement was divided into 4 phases: slowly ascending phase (A-B, Elevation); rapidly ascending phase (B-C, Anterior); temporary pause phase (position of maximum rise, Remain); and rapidly and slowly descending shifts toward the resting position phase (C-D, Return). We easily visualized the hyoid bone trajectory by using ultrasonography. In all cases, ultrasonographic analysis of the hyoid bone was confirmed to have a similar trajectory, as determined with videofluoroscopy. The average swallowing duration measurements increased with age. The measurement of the maximally elevated point of the hyoid bone decreased with age. The movement of the hyoid bone during swallowing can be visualized by US. The trajectory of the hyoid bone in sagittal section indicated the capability of swallowing, and may detect some anomalies in swallowing.

To evaluate in detail the dose distribution during computed tomography (CT), a sheet roll CT dosimetry phantom (SRCT-P) with a radiochromic film (RF) was experimentally developed. The SRCT-P was made by rolling up a vinyl chloride sheet in a cylindrical shape to arbitrarily select the SRCT-P diameter, dose measurement position, and depth. The SRCT-P centre core consisted of a plastic hose in which a 10 mm acrylic bar with a RF was inserted. To determine the availability of the SRCT-P, the surface and centre doses (at a 5 mm radius) at each SRCT-P diameter (6-16 cm; every 2 cm) were measured. The ratios of the centre-to-surface doses (D(centre)/D(surface)) systematically increased, from 80 to 111%, for decreasing SRCT-P diameters, between 16 and 6 cm, respectively. The centre dose approached the surface dose as the SRCT-P diameter decreased. To use a RF for a CT dose measurement, further detailed research and analysis is necessary. However, this study has shown that a SRCT-P is useful and beneficial for the measurement of the dose distribution during a CT examination.

Although the half-value layer (HVL) is one of the important parameters for quality assurance (QA) and quality control (QC), constant monitoring has not been performed because measurements using an ionization chamber (IC) are time-consuming and complicated. To solve these problems, a method using radiochromic film and step-shaped aluminum (Al) filters has been developed. To this end, GAFCHROMIC EBT2 dosimetry film (GAF-EBT2), which shows only slight energy dependency errors in comparison with GAFCHROMIC XR TYPE-R (GAF-R) and other radiochromic films, has been used. The measurement X-ray tube voltages were 120, 100, and 80 kV. GAF-EBT2 was scanned using a flat-bed scanner before and after exposure. To remove the non-uniformity error caused by image acquisition of the flat-bed scanner, the scanning image of the GAF-EBT2 before exposure was subtracted after exposure. HVL was evaluated using the density attenuation ratio. The effective energies obtained using HVLs of GAF-EBT2, GAF-R, and an IC dosimeter were compared. Effective energies with X-ray tube voltages of 120, 100, and 80 kV using GAF-EBT2 were 40.6, 36.0, and 32.9 keV, respectively. The difference ratios of the effective energies using GAF-EBT2 and the IC were 5.0%, 0.9%, and 2.7%, respectively. GAF-EBT2 and GAF-R proved to be capable of measuring effective energy with comparable precision. However, in HVL measurements of devices operating in the high-energy range (X-ray CT, radiotherapy machines, and so on), GAF-EBT2 was found to offer higher measurement precision than GAF-R, because it shows only a slight energy dependency.

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