Characterizing the range of simulated prostate abnormalities palpable by digital rectal examination

Abstract

Background-Although the digital rectal exam (DRE) is a common method of screening for prostate cancer and other abnormalities, the limits of ability to perform this hands-on exam are unknown. Perceptible limits are a function of the size, depth, and hardness of abnormalities within a given prostate stiffness.Methods-To better understand the perceptible limits of the DRE, we conducted a psychophysical study with 18 participants using a custom-built apparatus to simulate prostate tissue and abnormalities of varying size, depth, and hardness. Utilizing a modified version of the psychophysical method of constant stimuli, we uncovered thresholds of absolute detection and variance in ability between examiners.Results-Within silicone-elastomers that mimic normal prostate tissue (21 kPa), abnormalities of 4 mm diameter (20 mm 3 volume) and greater were consistently detectable (above 75% of the time) but only at a depth of 5 mm. Abnormalities located in simulated tissue of greater stiffness (82 kPa) had to be twice that volume (5 mm diameter,40 mm 3 volume) to be detectable at the same rate.Conclusions-This study finds that the size and depth of abnormalities most influence detectability, while the relative stiffness between abnormalities and substrate also affects detectability for some size/depth combinations. While limits identified here are obtained for idealized substrates, this work is useful for informing the development of training and allowing clinicians to set expectations on performance.

Construct validity in a high-fidelity prostate exam simulator

“…Therefore, scenarios involving these small lesions should be avoided in training programs. 15 Medical education curriculums employ standardized patients or physical simulators to teach the more intimate portions of the physical exam. The limitation of standardized patients is that most volunteers are 'normal.'…”

Measuring tactile cues at the fingerpad for object compliances harder and softer than the skin

“…The sets of compliance values were chosen to be greater or lesser than that of the fingertip; this property was confirmed by determining the stiffness of each stimulus and a human finger using a 6 mm flat-plate indenter indenting at 0.5 mm/s to a force of 1 N. Each stimulus was cylindrical with a diameter of 3.8 cm and height of 1.0 cm, so that its diameter was larger than the fingertip contact. Stimuli were constructed with a silicone elastomer (BJB Enterprises, Tustin, CA; TC-5005) with control of its modulus [10–12]. A small indentation at the center of the surface of each stimulus, approximately 1.0 mm in diameter with a depth of 0.3 mm and imperceptible to the participant, was introduced in the casting process so as to be usable later as a consistent point of comparison between stimuli and across stimulus replications and indentation levels.…”

Sociotechnical systems analysis in health care: a research agenda

“…This process was used by DeVoge et al (2009) to redesign a sign-out support tool for physicians. As a complement to engaging end users after a physical prototype is completed, computational methods such as statistical modeling approaches (see for example, Baumgart et al (2010)) and formal methods (such as Bolton & Bass, 2010; Bolton, Siminiceanu, & Bass, 2011) incorporating models of end user task behavior, medical devices, decision support tools, and/or the operational environment can inform requirements refinement. Such methods can allow modeling the impact of normative as well as potential erroneous human behavior (Bolton & Bass, in press; Bolton, Bass, & Siminiceanu, submitted).…”