Author: Kainoa Calistro-Allen, Brendon J. Villegas 👨🔬
Affiliation: University of Alabama Birmingham 🌍
Purpose:
To compare differences in radiation output and image quality in clinical esophagrams across fluoroscope vendors in use at University of Alabama Birmingham, prompted by reports that a newly installed unit delivers substantially higher than typical radiation doses.
Methods:
A phantom was developed to assess fluoroscopic planar image quality and record acquisition parameters for varying thicknesses of Lucite. The image quality phantom incorporates (20) low contrast objects localized by (5) steel alloy fiducials which were imaged at various thicknesses of soft tissue mimics (1-15 inches of total Lucite). We evaluated fluoroscopes from Shimadzu (digital detector), Siemens (digital detector), and Phillips (image intensifier) using the current standard clinical protocols for “esophagram” and “bariatric esophagram” examinations. Images were analyzed to quantitate quality metrics such as Signal to Noise Ratio (SNR), Contrast to Noise Ratio (CNR), and noise features. Concomitant dose metrics of radiation output (Air Kerma Rate (AKR), Entrance Skin Exposure Rate (ESER), Detector Exposure Rate (DER)) and beam quality (Half-Value Layer (HVL), kVp, mA) were obtained from the acquisition display and RadCal AcuGold Dosimetry set.
Results:
Shimadzu exhibited the highest radiation output (ESER, AKR, DER) and best image quality (CNR, SNR) for all protocols. Siemens uses the hardest beam (highest HVL) and highest mA among the vendors to deliver the lowest patient dose (AKR, ESER) at any mimic thickness, except Phillips at 9”. Siemens and Phillips performed comparably with their relative performance varying as a function of patient thickness; they exhibited similar dose profiles (ESER, AKR) and image quality (CNR) despite vast differences in detector type, detector fluence (DER), and beam quality (HVL, mA).
Conclusion:
This work demonstrates a standardized method to test the image quality and dose profile of fluoroscopes across vendors. This characterization can be used to adjust protocols to reduce dose creep and harmonize radiographic fluoroscopic units.