SIR 2025

General IR

Quality

Session: 2nd Annual Quality Improvement Forum: Improving Outcomes, Safety and Efficiency in IR

Evaluating CNR vs. SNR Optimized Automatic Dose Rate Control Fluoroscopy Systems: A Comparative Study of Image Quality and Dose Efficiency

Monday, March 31, 2025

10:25 AM – 10:34 AM CT

Location: Innovation Theatre

Presenter(s)

Chi M. Trinh

Medical Student
Johns Hopkins School of Medicine, United States

Author/Co-author(s)

SM

Sizhuo Meng, BS

Graduate Student
Johns Hopkins University, United States
TZ

Troy Zhou, PhD

Chief Physicist
Johns Hopkins Hospital, United States

Purpose: The purpose of this study is to compare the image quality and dose performance of fluoroscopy systems optimized for Contrast-to-Noise Ratio (CNR) and Signal-to-Noise Ratio (SNR) through automatic dose rate control (ADRC).[1] By evaluating these modes, the study aims to determine the optimal approach for balancing image quality and radiation dose, ultimately guiding better clinical decisions in interventional procedures.

Materials and Methods: Data were collected using a Siemens ARTIS Pheno robotic C-arm system, featuring both the classic SNR-optimized and the newly developed CNR-optimized automatic dose rate control (OPTIQ). A source-to-image distance of 110 cm was maintained. Five saline bags with varying iodine contrast concentrations (0%, 14%, 25%, 33%, 40%) were used to simulate contrast levels typically encountered in interventional fluoroscopic procedures. Three PMMA blocks (15 cm, 20 cm, 25 cm) were employed to represent patient tissues of different body sizes. The system was tested across high-, medium-, and low-dose modes. In total, 45 data sets were collected, capturing key metrics such as SNR, CNR, patient dose rate (PDR), and Figure of Merit (FOM) under all conditions.

Results: Preliminary results show that the traditional SNR-optimized ADRC outperformed the CNR-optimized ADRC OPTIQ in both SNR and CNR, with an average improvement of 10.39% and 6.06%, respectively, in each across various parameter settings. However, the patient dose rate was significantly higher in all configurations when using the CNR-optimized ADRC OPTIQ, with an average increase of 64.7%. The FOM, calculated as CNR²/PDR for both ADRC modes, also favored the classic SNR-optimized ADRC across all thicknesses and iodine concentrations, with an average increase of 137.67%.

Conclusion: This study highlights the substantial differences between the traditional SNR-optimized ADRC and the newly developed CNR-optimized ADRC in interventional fluoroscopy. The traditional SNR-optimized ADRC demonstrated superior image quality and greater radiation dose efficiency compared to the CNR-optimized ADRC. The choice of ADRC mode should be carefully tailored to the specific contrast requirements of each interventional procedure to optimize clinical outcomes and enhance patient safety. The proposed standardization methods aim to ensure consistent use of the appropriate ADRC mode, thereby improving both clinical outcomes and patient safety. [4]