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Published on: September 19, 2014
Tactile imaging of breast masses: first clinical report
P S Wellman1, E P Dalton, D Krag
1Harvard University Division of Engineering and Applied Sciences, 29 Oxford St, Cambridge, MA 02138, USA.
Hypothesis:
Tactile imaging can accurately document the palpable extent of breast masses.
Design:
Prospective nonrandomized interventional trial, comparing mass size estimates from preoperative physical examination, ultrasound, and tactile imaging with postoperative measurements of the resected masses.
Setting:
A community ambulatory surgical center and a university hospital tertiary care center.
Patients:
Twenty-three women undergoing surgical excision of breast masses. All subjects had a single, palpable, dominant mass, 0.5 to 3 cm in diameter.
Intervention:
Prior to surgery, the size of each mass was estimated from tactile imaging using an array of pressure sensors that is stroked over the mass. Size was also estimated by ultrasound and physical examination. Immediately following resection of the mass, it was bisected, and the palpable extent was measured with a caliper.
Main Outcome Measure:
Maximum mass diameter estimates from ultrasound, physical examination, and tactile imaging, compared with the resected measurement.
Results:
Tactile imaging estimates were repeatable (7.5% mean SD for multiple estimates of the same mass) and show good agreement with the resected measurements. Mean absolute error was 13%, and linear regression with zero intercept had a slope of 0.94, r(2) = 0.51. Physical examination and ultrasound estimates had respective mean absolute errors of 46% and 34%, regression slopes of 1.27 and 0.89, and r(2) = 0.28 and 0.37.
Conclusions:
Tactile imaging can provide accurate and reproducible estimates of the size of breast masses. This capability can enhance cancer surveillance for patients with benign masses (eg, due to scarring or fibrocystic changes) because previous work suggests that reliable detection of a difference in mass size by physical examination requires a 40% change in diameter. In contrast, this study suggests tactile imaging requires only a 15% change (95% confidence interval).
