(Sunday, 7/12/2020) [Eastern Time (GMT-4)]
Room: AAPM ePoster Library
Purpose: To investigate the logic of next generation of fluoroscopic automatic dose control system based on contrast-to-noise ratio (CNR) optimized trajectory/curve for the design of phantom suitable for image quality evaluation of same.
Method: The Siemens Pheno interventional angiography system was operated under both the traditional signal-to-noise ratio (SNR) optimized and the CNR optimized fluoroscopy operation. CNR optimizations for “iron” and “iodine” were investigated. For this initial attempt, the AAPM DSA Phantom was employed as the test object, along with additional PMMA plastic plates to simulate a patient thickness of up to 16” thick, following the AAPM TG 125 protocol. The CNR and SNR were measured using the fluoroscopy loop images. The phantom and flat panel image receptor input dose rates were also measured at the time of data acquisition.
Results: The SNR based operation yielded similar results presented in the TG 125 Report with relatively stable level of input dose rate (IDR) ove entire PMMA thickness range to the flat panel image receptor. The CNR based operation showed a wide range of variation in IDR while the CNR was relatively stable. Different levels of CNR are noted though when comparing between “iron” and “iodine” optimization modes.
Conclusion: The AAPM DSA phantom is an iodine based phantom that was subjected to two different CNR optimization schemes of the Siemens Pheno system. The CNR optimization resulted in lower IDR to the phantom. It was also apparent, the specific aim of the CNR optimized logic is geared for a specific target. Thus, any phantom designed for image quality evaluation of a CNR optimized system must account for the specific targets being “optimized”. The traditional phantom design will not work and may result in erroneous results. The phantom design must meet with the control logic of the CNR based system with specificity.
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