2025 Volume 29 Issue 3 Pages 126-133
Introduction: Videofluoroscopic swallowing study (VFSS) is widely used to evaluate swallowing function. In Japan, rice and rice gruel are main foods, even among patients with dysphagia. Typically, barium sulfate is sprinkled on cooked rice to create contrast for VFSS. However, cooked rice mixed with barium sulfate does not provide sufficient internal radiopacity. Recent electron microscopy findings have demonstrated that non-ionic iodine contrast media can penetrate the interior of rice grains. However, no studies have evaluated iodine contrast-enhanced rice in three dimensions. This study used microcomputed tomography (micro-CT) to assess the distribution of contrast within rice and gruel cooked with a non-ionic iodine contrast medium and to quantify the contrast enhancement via pixel values.
Methods: Sixteen types of simulated VFSS test foods, rice and rice gruel, were prepared with and without a contrast medium under varying pressure and soaking conditions. A non-ionic iodine contrast media, iodixanol, was mixed with water and uncooked rice, and the water level was adjusted to prepare rice or rice gruel (rice with excess water). Cooking was performed using an electric pressure cooker under low or high pressure, with either no soaking or 18 h of soaking. After cooking, samples were placed in plastic containers and scanned using a micro-CT device. Imaging conditions included 75 kV tube voltage, 50 mA current, and 600 projection angles. DICOM images were reconstructed and evaluated using open-source software. Pixel values were measured in 10 regions of interest. Samples were compared using the t-test at the significance level of 0.05.
Results: All test foods retained appropriate physical forms for VFSS. Micro-CT enabled non-destructive, three-dimensional observation of the contrast distribution of prepared test foods. Contrast-enhanced rice and rice gruel showed significantly higher pixel values than non-contrast test foods. Depending on the cooking pressure, the pixel values of contrast-enhanced rice ranged from 170 to 250, while those of rice gruel ranged from 150 to 190. Increasing the cooking pressure resulted in higher pixel values, suggesting greater penetration of contrast into the rice interior. Rice gruel exhibited a more uniform contrast distribution than rice owing to its higher water content. Additionally, soaking uncooked rice for a short time increased the pixel values.
Conclusion: Cooking rice and rice gruel with a non-ionic iodine contrast medium in a pressure cooker enhanced internal contrast. Micro-CT proved suitable for evaluating VFSS food models, allowing three-dimensional quantitative assessment of the distribution of contrast within VFSS test foods.
