Purpose or Case Report: Perception plays a significant role in the interpretation of images (Fig.1). A medical image perception society (MIPS) now exists with a goal to improve the understanding of imaging perceptual factors. Perception in sonography is different than other modalities where images are produced in a specifically formatted manner and then evaluated later by the observer (passive perception). Ultrasound is performed in a less standardized process to provide the best acoustic window of the region of concern. Image production requires the operator’s perceptual skills while acquiring the images (interactive perception). The study purpose was to determine if experience, knowledge base or scan time correlates with an imagers perceptual ability to visualize the normal appendix.
Methods & Materials: The retrospective study included 343 patients sent from emergency to radiology for an ultrasound to exclude appendicitis during 2014. Patients with a visualized normal appendix with subsequent discharge from hospital and patients in whom the appendix was not seen but who were discharged without a diagnosis of appendicitis were included. The studies were performed by 1 of 15 sonographers or 1 of 8 radiology residents. Time taken to acquire the images and whether the appendix was identified on sonography was recorded. The study was approved by the hospital ethics research board.
Results: Table 1 depicts patient characteristics, scan time and experience of the sonographer with perception of the appendix. In multivariable logistic regression (Table 2) both experience and scan time were significantly correlated with visualizing the pediatric, but not the adult appendix. Sonographers were in general better at identifying the appendix (33%) than the residents (21.8%), but not significantly. When comparing the more junior residents (PGY2/3) to the more knowledgeable R4/5, the differences in perceiving the appendix were negligible. The 4 sonographers with the highest perception rates had a four-fold increase in visualization of the pediatric appendix.
Conclusions: Missed diagnosis and misinterpretation of sonographic images is too easily attributed to patient/equipment limitations without significant research to define the role of individual perceptual expertise and the factors affecting it. Sonography to rule out appendicitis in the pediatric patient would be most successful if performed by an experienced sonographer with a history of success in identifying the normal appendix and with adequate time to perform the scan.