Innovations in medical imaging often come with new challenges. A recent study has highlighted the limitations of current methods for measuring radiation doses from wide detector computed tomography (CT), focusing particularly on the effectiveness of radiochromic film LD-V1 for dose profile assessments. With the rapid rise of CT technology over the past few decades, CT scans have become widespread, yet they are also recognized for contributing significantly to cumulative radiation exposure. Addressing this pressing issue, researchers at the First Affiliated Hospital of Bengbu Medical University conducted investigations to gauge the effectiveness of LD-V1 film, pivotal for correcting radiation dose assessments.
The study, published on March 7, 2025, aimed to derive correction factors for measured radiation doses based on console-read values—specifically the volume computed tomography dose index (CTDIvol). The researchers began by establishing calibration curves using CTDI phantoms across various tube currents at 120 kV, then utilized radiochromic film to capture dose profiles under wide beam collimations, such as 80, 100, 120, 140, and 160 mm.
Douglas Boone, noted for his analysis of CTDI limitations, drew attention to the challenges of using traditional pencil-shaped ionization chambers for capturing complete radiation profiles when X-ray beams exceed 40 mm. This study correlates with Boone’s findings, asserting the inadequacy of these traditional metrics for more advanced CT scanners, which have significantly increased beam widths.
Measurement accuracy was evaluated by placing the LD-V1 film within extended holes of CTDI phantoms and comparing the resulting dose profiles against console-displayed CTDIvol. It was confirmed by the study’s authors: "Radiochromic film LD-V1 is feasible for measuring the dose profile of wide detector CT scanners." This reliability stems from the film’s ability to record detailed dose distributions even when exposed to scattered fields inherent in CT scans.
Data revealed discrepancies between the film-derived CTDI values and those shown on consoles, prompting the establishment of correction factors. For head phantoms, the researchers found factors of 1.299, 1.284, 1.157, 1.151, and 1.099, with body phantoms showing slightly higher correction factors of 1.566, 1.585, 1.512, 1.365, and 1.327 across various collimation settings. Such findings fundamentally question previous assessments, recognizing, as stated by the authors, "The console-displayed CTDIvol doesn’t provide a full assessment of the radiation dose," thereby underscoring the need for these correction factors.
To obtain accurate CTDI values, it was necessary to oversee multiple readings under similar experimental conditions, which were supported by specific measurements across three separate trials to account for variability and reduce errors. The results were digitized using scanning technology, analyzed through image processing software, and informed the derived correction factors and measurement efficiencies—a key output of the study’s analysis.
Through the calibration process, the researchers maintained rigorous standards. Examining the film responses, it became evident the measurement efficiency exhibits variation, particularly lower efficiencies under wider beam configurations. Observational data unmistakably indicated the measurement rate diminishes with increasing axial beam width, which highlights the necessity for optimized calibration methods for upcoming CT technologies, ideally integrating the use of radiochromic films.
This study signifies substantial advancements not only for clinical implementation but also for future research endeavors aimed at optimizing radiation safety standards across imaging practices. The research leads toward potential application of these correction factors to modern CT systems with variable geometric and energy characteristics.
Continued exploration is encouraged, aimed at refining these techniques across different CT systems and establishing broader guidelines for clinical practice. The results presented represent a first step toward harmonizing the radiation dosimetry associated with advanced CT technologies—providing clinicians and patients with more reliable data for treatment planning, thereby enhancing overall safety. The authors are hopeful such methodologies could revolutionize CT assessment practices, ensuring the trade-offs of diagnostic imaging are thoroughly evaluated and minimized.