Impact of Camera Deviation on Penile Curvature Assessment Using 2D Pictures

Abstract

Background: An accurate curvature assessment (CA) is required in the decision-making process for patients with Peyronie's disease. In-office CA following induced erection is the gold standard for CA, although penile photography is commonly used due to its convenience. Camera deviations during 2D image acquisition might affect CA accuracy. Aim: To investigate the impact of camera angle deviations on CA. Methods: 2D pictures were taken from 5 models with a known uniplanar curvature (40 degrees, 45 degrees, 60 degrees, 90 degrees, and 120 degrees). The model was kept on a fixed point and the camera was rotated around it. Pictures were taken with every 10 degrees increase in camera deviation from the optimal position. The camera rotated to a maximum of 90 degrees deviation in both the vertical and horizontal planes. The pictures were analyzed by 2 different urologists using a goniometer. The expected apparent curvature (AC) and the corresponding picture assessment error (PAE = AC - real model curvature) were also calculated for each picture using trigonometry principles. Main Outcome Measure: Assessing PAE magnitude and patterns was our primary outcome. Secondary outcomes were intraobserver, interobserver, and observer-AC intraclass correlation coefficient (ICC). Results: 100 pictures were analyzed. Intraobserver reliability was high (ICC = 0.99) for both urologists. Interobserver and observer-AC correlation were also high (ICC = 0.996 and ICC = 0.992, respectively). When the camera rotated in the horizontal axis, the PAE underestimated the curvature for models with curvatures smaller than 90 degrees and overestimated the reading of the 120 degrees model. When the camera rotated in the vertical axis, PAE had an inverse effect. The PAE showed a tendency to increase exponentially with higher deviation, reaching almost 100% for a deviation of 80 degrees. Nevertheless, analyzing its magnitude regardless of the curvature, PAE was always <5% for camera deviations of 0-20 degrees. Clinical Implications: If using picture-based CA, clinicians should attempt to take a picture perpendicular to the curvature plane for the most accurate measurement in degrees. Many clinicians request that patients take 3 pictures in a standard fashion (craniocaudal, lateral, and frontal), and if this technique is to be used, an extra picture is recommended. Strength & Limitations: In our controlled environment, we were able to isolate CA errors due to camera angles from other confounders such as erection hardness. As a consequence, however, our results cannot be easily generalized. Conclusion: PAE due to non-optimal camera position is a complex phenomenon that affects CA depending on the rotation axis and the degree of penile curvature. Nevertheless, PAE is always <5% for camera deviations of 0-20 degrees