Fundamental study on the effectiveness of X-ray spectrum shaping technology in computed tomographic colonography: Using barium for tagging

Abstract

Objective: We evaluated the applicability of X-ray spectrum shaping technology to computed tomographic colonography (CTC) using barium (Ba) for tagging.

Methods: We compared an imaging method that uses only a bowtie filter (BF) and an imaging method that adds a tin filter (TF) using X-ray spectrum shaping technology. The modulation transfer function (MTF) and standard deviation/noise power spectrum (SD/NPS) were calculated using the wire method and a water phantom (20 cm), respectively. We used a colon CT phantom (NCCS type) to evaluate lesion detection ability. Only air and a Ba suspension adjusted to three different CT values were placed inside the simulated intestinal tract to measure the CT value of the Ba suspension portion (CT value _Ba), and the full width at half maximum (FWHM), diameter, and height of a simulated polyp (7 mm, 5 mm) were measured.

Results: There was no change in MTF with either imaging method. The SD and NPS were lower with TF, and the image quality was improved in terms of noise. The CT value _Ba decreased by an average of 33% with TF. FWHM increased with the TF method when the CT value _Ba was high (difference was within 6%). Furthermore, the simulated polyp could be recognized under all conditions, and no statistically significant difference was observed in the measurement results.

With the TF method, it has been suggested that the ability to detect lesions may be affected, especially when the CT value of the residue is low, and caution is required when interpreting images.

Conclusion: The TF may affect the ability to detect lesions if the CT value of the residue is low, so care must be taken when interpreting images. However, in this study, there was no significant difference in lesion detection ability compared to the BF, suggesting that this imaging method can be applied to CTC using Ba for tagging.