Image Quality Assessment of Low CT Dose for Foreign Bodies Detection
Presentations
PO-GePV-M-254 (Sunday, 7/25/2021) [Eastern Time (GMT-4)]
Purpose: To develop a suitable image quality CT protocol to detect the foreign bodies (FBs) in the respiratory tract of pediatrics with both a minimum patient radiation dose and an equivalent radiation risk to a conventional radiograph chest exam.
Methods: CT Data were collected on a Siemens Flash. The modification to the protocol included setting the reference kVp to 80, which lowered the CTDI value by 58%, the reference mAs to 9 mAs which reduced the CTDI by an additional 90%, using X-CARE and Adaptive Dose Shield, SAFIRE was set to order 4. Twenty CT exams using the modified CT protocol were performed with different FBs distributions in a five years old size anthropomorphic phantom (LUNGBOY) shown in Figure (1). The FBs included small size radiopaque bodies such as fish bones, peanuts, LEGO toys, etc. The exams were then presented randomly to the radiologist team to interpret the images and report the results. The GE QC phantom (Figure a) was used to measure the modulation transfer function (MTF). The ACR CT phantom (Figure 2) used to measure the (CNR). Image quality metric (Q) is calculated to characterize and to compare the different CT protocols in terms of dose, spatial resolution, and noise using: Q=c.(ρ(10%)⁴)/(σ.D)
Results: The CNR is reduced by 20% due to the decrease in mAs. The images were reconstructed with kernel I30, the limiting spatial resolution at 10% MTF was improved. The Q-factor was increased, indicating improvement in image quality, due to the decrease in the CTDI and the increase in the MTF. The results are summarized in table(1)
Conclusion: Low-dose CT protocols can be very reliable for FB detection with high image quality and low patient dose, especially in pediatric patients where the aspiration of FBs is a frequent and severe cause of respiratory problems in children.
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