Ultra-low-dose computed tomography system with a flat panel detector: assessment of radiation dose reduction and spatial and low contrast resolution

Abstract

Purpose: The aim of this study was to introduce a prototype cone-beam computed tomography system equipped with a flat panel detector (FPD-CT system) and measure its radiation dose and spatial and lowcontrast resolution.

Materials and methods: A patient was rotated in a sitting position, and cone beam data were acquired with the flat panel detector from a fixed X-ray tube. Absorbed dose, spatial and low-contrast resolution, and variation in the CT attenuation value were assessed quantitatively in the acrylic phantom. The visibility of normal blood vessels in clinical images of seven patients was analyzed qualitatively by five board-certified radiologists. These quantitative and qualitative data were compared between the FPD-CT system and multidetector row CT (MDCT).

Results: Minimal low-contrast sensitivity and a moderate spatial resolution were demonstrated in images of central lung fields acquired by FPD-CT. The absorbed dose in the FPD-CT system decreased to approximately 2.5% of the dose in the MDCT system.

Conclusion: Considering crossover structures in normal blood vessels and bronchi in the central areas of lung fields, this result implies that fairly acceptable spatial resolution can be realized with FPD-CT for detection and frequent follow-up of pulmonary abnormalities in the central lung fields.