(Thursday, 7/18/2019) 1:00 PM - 3:00 PM
Room: 302
Purpose: Abdominal radiography is the gold-standard for confirming enteric tube placement and location. This study is to develop a new low-exposure protocol for this commonly performed portable radiographic exam. Techniques, energy (kVp) and tube current time product (mAs), were defined as a function of patient body habitus and presence of a ventilator.
Methods: To quantify current state-of-practice, a sample population of tube placement images was collected. Technologists, blinded to the goal, recorded distances from the x-ray tube to patient, x-ray tube to detector, body mass index, and patient ventilation status. This information, in conjunction with phantom imaging of various enteric tubes, was used to establish size-specific imaging protocols. Nasogastric and Dobhoff tubes were positioned between a torso phantom and sheets of tissue-equivalent material and imaged on a Shimadzu portable (MUX-200D-XC) under multiple kVp and mAs combinations. Images were analyzed for exposure index (EI) and tube conspicuity. Tube appearances in phantom images were assigned a numeric conspicuity score by a radiologist: not visualized (0) to diagnostic (3).
Results: Phantom images with EI from 7 to 631 over thicknesses of 9 to 15 inches were scored for tube conspicuity. All images scored at least a 3, indicating all were diagnostic for the task of confirming tube placement, even at the lowest EI. Based on these results, an EI goal of 20-30 was set for four patient size bins. Low-dose protocols were then developed by down scaling patient baseline data to the new EI goal.
Conclusion: Following review and refinement of enteric tube placement portable radiograph techniques, it has been demonstrated that a task-optimized protocol provides two key benefits. One is a substantial reduction in dose (-90%) and two creation of a standardized level of image quality performance to confirm enteric tube placement.
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