Fiber-based laser speckle imaging for the detection of pulsatile flow

• Published in: Lasers in surgery and medicine Vol. 47; no. 6; pp. 520 - 525
• Main Authors: Regan, Caitlin, Yang, Bruce Y., Mayzel, Kent C., Ramirez-San-Juan, Julio C., Wilder-Smith, Petra, Choi, Bernard
• Format: Journal Article
• Language: English
• Published: United States Blackwell Publishing Ltd 01.08.2015; Wiley Subscription Services, Inc
• Subjects: cold test; dental photoplethysmography; Dental Pulp - blood supply; electric pulp test; endodontics; endodontics; leached fiber bundle; Equipment Design; Healthy Volunteers; Humans; In Vitro Techniques; Lasers, Gas; leached fiber bundle; Optical Fibers; Optical Imaging - instrumentation; Optical Imaging - methods; Photoplethysmography - instrumentation; Photoplethysmography - methods; pulpal vitality; pulsatile blood flow; Pulsatile Flow; root canal; electric pulp test; cold test; dental photoplethysmography; endodontics; leached fiber bundle; root canal; pulsatile blood flow; pulpal vitality
• ISSN: 0196-8092; 1096-9101; 1096-9101
• DOI: 10.1002/lsm.22370

Background and Objective In endodontics, a major diagnostic challenge is the accurate assessment of pulp status. In this study, we designed and characterized a fiber‐based laser speckle imaging system to study pulsatile blood flow in the tooth. Study Design/Materials and Methods To take transilluminated laser speckle images of the teeth, we built a custom fiber‐based probe. To assess our ability to detect changes in pulsatile flow, we performed in vitro and preliminary in vivo tests on tissue‐simulating phantoms and human teeth. We imaged flow of intralipid in a glass microchannel at simulated heart rates ranging from 40 beats/minute (bpm) to 120 bpm (0.67–2.00 Hz). We also collected in vivo data from the upper front incisors of healthy subjects. From the measured raw speckle data, we calculated temporal speckle contrast versus time. With frequency‐domain analysis, we identified the frequency components of the contrast waveforms. Results With our approach, we observed in vitro the presence of pulsatile flow at different simulated heart rates. We characterized simulated heart rate with an accuracy of and >98%. In the in vivo proof‐of‐principle experiment, we measured heart rates of 69, 90, and 57 bpm, which agreed with measurements of subject heart rate taken with a wearable, commercial pulse oximeter. Conclusions We designed, built, and tested the performance of a dental imaging probe. Data from in vitro and in ­vivo tests strongly suggest that this probe can detect the presence of pulsatile flow. LSI may enable endodontists to noninvasively assess pulpal vitality via direct measurement of blood flow. Lasers Surg. Med. 47:520–525, 2015. © 2015 Wiley Periodicals, Inc.