Artificial palpation in robotic surgery using haptic feedback.

BACKGROUND: The loss of tactile feedback in minimally invasive robotic surgery remains a major challenge to the expanding field. With visual cue compensation alone, tissue characterization via palpation proves to be immensely difficult. This work evaluates a bimodal vibrotactile system as a means of conveying applied forces to simulate haptic feedback in two sets of studies simulating an artificial palpation task using the da Vinci surgical robot. METHODS: Subjects in the first study were tasked with localizing an embedded vessel in a soft tissue phantom using a single-sensor unit. In the second study, subjects localized tumor-like structures using a three-sensor array. In both sets of studies, subjects completed the task under three trial conditions: no feedback, normal force tactile feedback, and hybrid vibrotactile feedback. Recordings of correct localization, incorrect localization, and time-to-completion were used to evaluate performance outcomes. RESULTS: With the addition of vibrotactile and pneumatic feedback, significant improvements in the percentage of correct localization attempts were detected (p = 0.0001 and p = 0.0459, respectively) during the first experiment with phantom vessels. Similarly, significant improvements in correct localization were found with the addition of vibrotactile (p = 2.57E-5) and pneumatic significance (p = 8.54E-5) were observed in the second experiment involving tumor phantoms. CONCLUSIONS: This work demonstrates not only the superior benefits of a multi-modal feedback over traditional single-modality feedback, but also the effectiveness of vibration in providing haptic feedback to artificial palpation systems.

Gradient-based 3D skin roughness rendering from an in-vivo skin image for dynamic haptic palpation.

BACKGROUND/PURPOSE: Many studies have revealed the importance of palpation for dermatologists; however, palpation is not always possible due to the risk of secondary infections or the risk of damaging the affected area. Thus, haptic rendering for indirect palpation using in-vivo skin images, which will enable to examine a real three-dimensional (3D) skin sample by virtual touch without directly palpating the infected skin area, could be a useful technology in dermatology. METHODS: We propose a new method of accurate 3D skin surface reconstruction using simple gradients from a single skin image for accurate 3D roughness rendering with a haptic device. Our approach takes advantage of bilateral filtering to preserve skin roughness and image gradients in order to generate a 3D skin surface (polygonal meshes) while preserving skin wrinkles and rough surface textures. RESULTS: Our method was evaluated using two experiments. The accuracy was tested with six 3D ground-truth surfaces and four clinical skin images (acne, miliaria, sweet syndrome, and herpes simplex). For objective evaluation, a well-known 3D roughness estimation method and the Hausdorff distance were adopted to compute errors. All results showed that the accuracy of our method is superior to that of the two existing methods. CONCLUSION: Haptic roughness rendering for skin palpation examination requires efficient and accurate 3D surface reconstruction. In this study, we developed a new method that can be used to reconstruct a 3D skin surface accurately while preserving roughness through the use of a single skin image.

Accurate depth estimation of skin surface using a light-field camera toward dynamic haptic palpation.

BACKGROUND: Haptic skin palpation with three-dimensional skin surface reconstruction from in vivo skin images in order to acquire both tactile and visual information has been receiving much attention. However, the depth estimation of skin surface, using a light field camera that creates multiple images with a micro-lens array, is a difficult problem due to low-resolution images resulting in erroneous disparity matching. METHODS: Multiple low-resolution images decoded from a light field camera have limitations to accurate 3D surface reconstruction needed for haptic palpation. To overcome this, a deep learning method, Generative Adversarial Networks, was employed to generate super-resolved skin images that preserve surface detail without blurring, and then, accurate skin depth was estimated by taking multiple subsequent steps including lens distortion correction, sub-pixel shifted image generation using phase shift theorem, cost-volume building, multi-label optimization, and hole filling and refinement, which is a new approach for 3D skin surface reconstruction. RESULTS: Experimental results of the deep-learning-based super-resolution method demonstrated that the textural detail (wrinkles) of super-resolved skin images is well preserved, unlike other super-resolution methods. In addition, the depth maps computed with our proposed algorithm verify that our method can produce more accurate and robust results compared to other state-of-the-art depth map computation methods. CONCLUSION: Herein, we first proposed depth map estimation of skin surfaces using a light field camera and subsequently tested it with several skin images. The experimental results established the superiority of the proposed scheme.

Haptic Glove and Platform with Gestural Control For Neuromorphic Tactile Sensory Feedback In Medical Telepresence †.

Advancements in the study of the human sense of touch are fueling the field of haptics. This is paving the way for augmenting sensory perception during object palpation in tele-surgery and reproducing the sensed information through tactile feedback. Here, we present a novel tele-palpation apparatus that enables the user to detect nodules with various distinct stiffness buried in an ad-hoc polymeric phantom. The contact force measured by the platform was encoded using a neuromorphic model and reproduced on the index fingertip of a remote user through a haptic glove embedding a piezoelectric disk. We assessed the effectiveness of this feedback in allowing nodule identification under two experimental conditions of real-time telepresence: In Line of Sight (ILS), where the platform was placed in the visible range of a user; and the more demanding Not In Line of Sight (NILS), with the platform and the user being 50 km apart. We found that the entailed percentage of identification was higher for stiffer inclusions with respect to the softer ones (average of 74% within the duration of the task), in both telepresence conditions evaluated. These promising results call for further exploration of tactile augmentation technology for telepresence in medical interventions.

Ultrasound-Guided Dynamic Needle Tip Positioning Technique Versus Palpation Technique for Radial Arterial Cannulation in Adult Surgical Patients: A Randomized Controlled Trial.

BACKGROUND: Radial arterial cannulation is most commonly done using palpation, but the use of ultrasound has increased the cannulation success rate. This improvement, albeit significant, has not led to a very high success rate especially in trainees. A modified ultrasound technique for vascular cannulation (dynamic needle tip positioning) has been described for peripheral venous cannulation. We therefore assessed the success rate of this technique compared to the palpation technique for radial artery cannulation in adult surgical patients. METHODS: We enrolled patients who were having nonemergent operations that required a radial arterial catheter for intraoperative monitoring. Patients were randomized to either palpation or dynamic needle tip positioning technique. Arterial cannulation was performed by anesthesia residents or faculty members. The primary end point was successful cannulation on the first pass. Secondary end points were overall 5-minute success rate and number of attempts within 5 minutes. RESULTS: Two hundred sixty patients were evaluated. The first-pass success rate was 83% in the dynamic needle tip positioning technique group (n = 132) and 48% in the palpation group (n = 128; P < .001); relative risk was 2.5; 95% confidence interval, 1.7-3.6. The overall 5-minute success rate was 89% in the dynamic needle tip positioning technique group compared to 65% in the palpation group (P < .001), relative risk was 2.4; 95% confidence interval, 1.2-1.6. The number of skin puncture attempts was significantly more in the palpation group (P < .001). The median cannulation times and interquartile ranges were 81.5 (61-122) seconds in the dynamic needle tip positioning and 76 (48-175) seconds (P = .7) in the palpation group. CONCLUSIONS: The use of the ultrasound-guided dynamic needle tip positioning technique increased the first and overall success rates compared to palpation in anesthesia residents and faculty members.

Haptic augmented skin surface generation toward telepalpation from a mobile skin image.

BACKGROUND/PURPOSE: Very little is known about the methods of integrating palpation techniques to existing mobile teleskin imaging that delivers low quality tactile information (roughness) for telepalpation. However, no study has been reported yet regarding telehaptic palpation using mobile phone images for teledermatology or teleconsultations of skincare. METHODS: This study is therefore aimed at introducing a new algorithm accurately reconstructing a haptic augmented skin surface for telehaptic palpation using a low-cost clip-on microscope simply attached to a mobile phone. Multiple algorithms such as gradient-based image enhancement, roughness-adaptive tactile mask generation, roughness-enhanced 3D tactile map building, and visual and haptic rendering with a three-degrees-of-freedom (DOF) haptic device were developed and integrated as one system. RESULTS: Evaluation experiments have been conducted to test the performance of 3D roughness reconstruction with/without the tactile mask. The results confirm that reconstructed haptic roughness with the tactile mask is superior to the reconstructed haptic roughness without the tactile mask. Additional experiments demonstrate that the proposed algorithm is robust against varying lighting conditions and blurring. In last, a user study has been designed to see the effect of the haptic modality to the existing visual only interface and the results attest that the haptic skin palpation can significantly improve the skin exam performance. CONCLUSION: Mobile image-based telehaptic palpation technology was proposed, and an initial version was developed. The developed technology was tested with several skin images and the experimental results showed the superiority of the proposed scheme in terms of the performance of haptic augmentation of real skin images.

Roughness based perceptual analysis towards digital skin imaging system with haptic feedback.

BACKGROUND/PURPOSE: To examine psoriasis or atopic eczema, analyzing skin roughness by palpation is essential to precisely diagnose skin diseases. However, optical sensor based skin imaging systems do not allow dermatologists to touch skin images. To solve the problem, a new haptic rendering technology that can accurately display skin roughness must be developed. In addition, the rendering algorithm must be able to filter spatial noises created during 2D to 3D image conversion without losing the original roughness on the skin image. In this study, a perceptual way to design a noise filter that will remove spatial noises and in the meantime recover maximized roughness is introduced by understanding human sensitivity on surface roughness. METHODS: A visuohaptic rendering system that can provide a user with seeing and touching digital skin surface roughness has been developed including a geometric roughness estimation method from a meshed surface. In following, a psychophysical experiment was designed and conducted with 12 human subjects to measure human perception with the developed visual and haptic interfaces to examine surface roughness. RESULTS: From the psychophysical experiment, it was found that touch is more sensitive at lower surface roughness, and vice versa. Human perception with both senses, vision and touch, becomes less sensitive to surface distortions as roughness increases. When interact with both channels, visual and haptic interfaces, the performance to detect abnormalities on roughness is greatly improved by sensory integration with the developed visuohaptic rendering system. CONCLUSION: The result can be used as a guideline to design a noise filter that can perceptually remove spatial noises while recover maximized roughness values from a digital skin image obtained by optical sensors. In addition, the result also confirms that the developed visuohaptic rendering system can help dermatologists or skin care professionals examine skin conditions by using vision and touch at the same time.

The effectiveness of a mobile application for the development of palpation and ultrasound imaging skills to supplement the traditional learning of physiotherapy students.

BACKGROUND: Mobile learning (m-learning) has becoming very popular in education due to the rapidly advancing technology in our society. The potentials of the mobile applications should be used to enhance the education process. Few mobile applications have been designed to complement the study of physical therapy skills for physiotherapy students. The aim of this study was to investigate whether a mobile application, as a supplement to traditional learning, is useful for physiotherapy students in the acquisition of palpation and ultrasound skills in the shoulder area. METHODS: Forty-nine students participated in this single-blinded, randomized controlled study. They were randomly distributed into two groups: experimental, with free access to the mobile application; and control, with access to traditional learning materials on the topic. Objective structured clinical evaluation (OSCE) and multiple-choice questionnaire (MCQ) were used to assess the educational intervention. Then, we also assessed the time taken to get a reliable ultrasound image and to localize a specific shoulder structure by palpation. RESULTS: There was no significant intergroup difference in the acquisition of theoretical knowledge (p = .089). Scores were significantly higher in the experimental group than in the control group for the majority items in the ultrasound assessment; positioning of patient (p < .001), positioning of ultrasound probe (p = 0.007), handling of ultrasound probe (p = .013) and global OSCE (p < .001) and skills in palpation of the shoulder; position of patient (p = .009), direction of palpation contact (p = .021) and global OSCE (p = .034). There were no significant differences in the time required to perform the examination between groups in ultrasound (p = .944) and palpation (p = .393). The results from the post-program survey assessing the global satisfaction with the mobile application were high (8.200 ± .767), on an 11 numeric point rating scale. CONCLUSION: These results suggest the effectiveness of an m-learning program as a complement to traditional education for developing skills in ultrasound and palpation of the shoulder region in undergraduate physiotherapy students.

Perception-based 3D tactile rendering from a single image for human skin examinations by dynamic touch.

BACKGROUND/AIMS: Diagnosis of skin conditions is dependent on the assessment of skin surface properties that are represented by more tactile properties such as stiffness, roughness, and friction than visual information. Due to this reason, adding tactile feedback to existing vision based diagnosis systems can help dermatologists diagnose skin diseases or disorders more accurately. The goal of our research was therefore to develop a tactile rendering system for skin examinations by dynamic touch. METHODS: Our development consists of two stages: converting a single image to a 3D haptic surface and rendering the generated haptic surface in real-time. Converting to 3D surfaces from 2D single images was implemented with concerning human perception data collected by a psychophysical experiment that measured human visual and haptic sensibility to 3D skin surface changes. For the second stage, we utilized real skin biomechanical properties found by prior studies. Our tactile rendering system is a standalone system that can be used with any single cameras and haptic feedback devices. RESULTS: We evaluated the performance of our system by conducting an identification experiment with three different skin images with five subjects. The participants had to identify one of the three skin surfaces by using a haptic device (Falcon) only. No visual cue was provided for the experiment. The results indicate that our system provides sufficient performance to render discernable tactile rendering with different skin surfaces. CONCLUSION: Our system uses only a single skin image and automatically generates a 3D haptic surface based on human haptic perception. Realistic skin interactions can be provided in real-time for the purpose of skin diagnosis, simulations, or training. Our system can also be used for other applications like virtual reality and cosmetic applications.

Google Glass, ultrasound and palpation: the anatomy teacher of the future?

Traditional palpation techniques are used less often in today's modern medical arena. Technological advances in imaging, for example, often supplant the need for such types of tactility. Herein, we discuss our recent experience using Google Glass in the teaching of anatomy to medical students, a method that melds traditional medical palpation with cutting edge technology. Based on our study, teachers of the new millennium might use Google Glass coupled with ultrasound and palpation in the teaching of human anatomy to medical students. Such a technology combines palpation, diagnosis, visualization, and learning of anatomy. Glass has provided a platform to position a live ultrasound image for us to view while examining the patient. This technology will allow the physicians of the future to embrace placing ones hand on the body while receiving both palpation and visual stimulation.

Optical palpation: optical coherence tomography-based tactile imaging using a compliant sensor.

We present optical palpation, a tactile imaging technique for mapping micrometer- to millimeter-scale mechanical variations in soft tissue. In optical palpation, a stress sensor consisting of translucent, compliant silicone with known stress-strain behavior is placed on the tissue surface and a compressive load is applied. Optical coherence tomography (OCT) is used to measure the local strain in the sensor, from which the local stress at the sample surface is calculated and mapped onto an image. We present results in tissue-mimicking phantoms, demonstrating the detection of a feature embedded 4.7 mm below the sample surface, well beyond the depth range of OCT. We demonstrate the use of optical palpation to delineate the boundary of a region of tumor in freshly excised human breast tissue, validated against histopathology.

Vibration and rotation during biaxial pressure algometry is related with decreased and increased pain sensations.

OBJECTIVE: During palpation, the pressure intensity and direction include minor deviations suggesting that standardized variations of the pressure intensity during pressure algometry may optimize the stimulus efficacy. This study examined the perceived pain outcome and reliability of a biaxial (bidirectional) algometer exerting rotational and vibratory stimulation on top of the basic pressure. METHODS: In 24 healthy subjects, pressure pain thresholds (PPTs) were recorded with a linear pressure gradient (30 kPa/s) applied by a 1-cm(2) probe bilaterally on the tibialis anterior muscle via biaxial and handheld algometers. During constant pressure stimulation (5 seconds, 75%, 100%, 125% PPT), rotational (45°, 90°, and 180°), linear vibrational (15, 25, and 50 Hz), and radial vibrational stimulations (5, 15, and 25 Hz) were applied randomly via regular and fanning rounded probes (1 cm(2)). Subjects rated perceived pain on a 10-cm visual analogue scale on two occasions separated by 1 week period. RESULTS: Repeated measures analysis of variance revealed enhanced effect of rotation angle (P < 0.001), probe (P < 0.001), and radial vibration frequency (P < 0.02), and suppressing effect of axial vibration frequency (P < 0.03) on pain perception, relative to basic pressure alone. PPT reliability of biaxial and handheld algometers showed averaged intraclass correlation coefficient of 0.94 and 0.945, and coefficient of variations of 15.4 and 13.5%, respectively. CONCLUSIONS: PPT assessment and multidirectional stimulations can be exerted reliably via biaxial algometer. Linear vibrational stimulation effect on pressure pain perception verified the inhibitory interaction between simultaneous pressure stimulation of low-threshold mechanoreceptors and nociceptors, while radial vibration and rotational stimulation showed facilitatory effects.

Prototype tactile feedback system for examination by skin touch.

BACKGROUND/PURPOSE: Diagnosis of conditions such as psoriasis and atopic dermatitis, in the case of induration, involves palpating the infected area via hands and then selecting a ratings score. However, the score is determined based on the tester's experience and standards, making it subjective. To provide tactile feedback on the skin, we developed a prototype tactile feedback system to simulate skin wrinkles with PHANToM OMNI. METHODS: To provide the user with tactile feedback on skin wrinkles, a visual and haptic Augmented Reality system was developed. First, a pair of stereo skin images obtained by a stereo camera generates a disparity map of skin wrinkles. Second, the generated disparity map is sent to an implemented tactile rendering algorithm that computes a reaction force according to the user's interaction with the skin image. RESULTS: We first obtained a stereo image of skin wrinkles from the in vivo stereo imaging system, which has a baseline of 50.8 µm, and obtained the disparity map with a graph cuts algorithm. The left image is displayed on the monitor to enable the user to recognize the location visually. The disparity map of the skin wrinkle image sends skin wrinkle information as a tactile response to the user through a haptic device. CONCLUSION: We successfully developed a tactile feedback system for virtual skin wrinkle simulation by means of a commercialized haptic device that provides the user with a single point of contact to feel the surface roughness of a virtual skin sample.

A novel airway device with tactile sensing capabilities for verifying correct endotracheal tube placement.

We present a new device for verifying endotracheal tube (ETT) position that uses specialized sensors intended to distinguish anatomical features of the trachea and esophagus. This device has the potential to increase the safety of resuscitation, surgery, and mechanical ventilation and decrease the morbidity, mortality, and health care costs associated with esophageal intubation and unintended extubation by potentially improving the process and maintenance of endotracheal intubation. The device consists of a tactile sensor connected to the airway occlusion cuff of an ETT. It is intended to detect the presence or absence of tracheal rings immediately upon inflation of the airway occlusion cuff. The initial study detailed here verifies that a prototype device can detect contours similar to tracheal rings in a tracheal model.

Intra- and inter-operator reliability of measuring compressive stiffness of the patellar tendon in volleyball players using a handheld digital palpation device.

This observational study aimed to evaluate the intra- and inter-operator reliability of a digital palpation device in measuring compressive stiffness of the patellar tendon at different knee angles in talent and elite volleyball players. Second aim was to examine differences in reliability when measuring at different knee angles, between dominant and non-dominant knees, between sexes, and with age. Two operators measured stiffness at the midpoint of the patellar tendon in 45 Dutch volleyball players at 0°, 45° and 90° knee flexion, on both the dominant and non-dominant side. We found excellent intra-operator reliability (ICC>0.979). For inter-operator reliability, significant differences were found in stiffness measured between operators (p<0.007). The coefficient of variance significantly decreased with increasing knee flexion (2.27% at 0°, 1.65% at 45° and 1.20% at 90°, p<0.001). In conclusion, the device appeared to be reliable when measuring compressive stiffness of the patellar tendon in elite volleyball players, especially at 90° knee flexion. Inter-operator reliability appeared to be questionable. More standardized positioning and measurement protocols seem necessary.

Enhancing robotic telesurgery with sensorless haptic feedback.

PURPOSE: This paper evaluates user performance in telesurgical tasks with the da Vinci Research Kit (dVRK), comparing unilateral teleoperation, bilateral teleoperation with force sensors and sensorless force estimation. METHODS: A four-channel teleoperation system with disturbance observers and sensorless force estimation with learning-based dynamic compensation was developed. Palpation experiments were conducted with 12 users who tried to locate tumors hidden in tissue phantoms with their fingers or through handheld or teleoperated laparoscopic instruments with visual, force sensor, or sensorless force estimation feedback. In a peg transfer experiment with 10 users, the contribution of sensorless haptic feedback with/without learning-based dynamic compensation was assessed using NASA TLX surveys, measured free motion speeds and forces, environment interaction forces as well as experiment completion times. RESULTS: The first study showed a 30% increase in accuracy in detecting tumors with sensorless haptic feedback over visual feedback with only a 5-10% drop in accuracy when compared with sensor feedback or direct instrument contact. The second study showed that sensorless feedback can help reduce interaction forces due to incidental contacts by about 3 times compared with unilateral teleoperation. The cost is an increase in free motion forces and physical effort. We show that it is possible to improve this with dynamic compensation. CONCLUSION: We demonstrate the benefits of sensorless haptic feedback in teleoperated surgery systems, especially with dynamic compensation, and that it can improve surgical performance without hardware modifications.

A Minimally Invasive Robotic Tissue Palpation Device.

OBJECTIVE: Robot-assisted minimally invasive surgery remains limited by the absence of haptic feedback, which surgeons routinely rely on to assess tissue stiffness. This limitation hinders surgeons' ability to identify and treat abnormal tissues, such as tumors, during robotic surgery. METHODS: To address this challenge, we developed a robotic tissue palpation device capable of rapidly and non-invasively quantifying the stiffness of soft tissues, allowing surgeons to make objective and data-driven decisions during minimally invasive procedures. We evaluated the effectiveness of our device by measuring the stiffness of phantoms as well as lung, heart, liver, and skin tissues obtained from both rats and swine. RESULTS: Results demonstrated that our device can accurately determine tissue stiffness and identify tumor mimics. Specifically, in swine lung, we determined elastic modulus (E) values of 9.1 ± 2.3, 16.8 ± 1.8, and 26.0 ± 3.6 kPa under different internal pressure of the lungs (PIP) of 2, 25, and 45 cmH2O, respectively. Using our device, we successfully located a 2-cm tumor mimic embedded at a depth of 5 mm in the lung subpleural region. Additionally, we measured E values of 33.0 ± 5.4, 19.2 ± 2.2, 33.5 ± 8.2, and 22.6 ± 6.0 kPa for swine heart, liver, abdominal skin, and muscle, respectively, which closely matched existing literature data. CONCLUSION/SIGNIFICANCE: Results suggest that our robotic palpation device can be utilized during surgery, either as a stand-alone or additional tool integrated into existing robotic surgical systems, to enhance treatment outcomes by enabling accurate intraoperative identification of abnormal tissue.

Application of a new palpometer for intraoral mechanical pain sensitivity assessment.

AIMS: To investigate the reliability and magnitude of intraoral mechanical pain sensitivity by using a palpometer with add-on devices with different physical properties. METHODS: Sixteen healthy volunteers participated. Three palpometers (0.5, 1.0, and 2.0 kg) were used. Add-on devices were put on the circular metal stamp of the palpometer. Four diameters (3, 4, 5, and 10 mm) and two shapes of the rubber-top (flat and round) of the add-on devices were tested at each force level, ie, a total of 24 combinations. Participants were stimulated at the gingival mucosa around the maxillary central incisors and first molars on both sides by using the palpometers in randomized order. Participants rated perceived stimulus intensity on a 0-50-100 numerical rating scale (NRS). Ten volunteers were examined twice on the same day and recalled for a second session for assessment of within- and between-session reliability. Intraclass correlation coefficients were calculated for reliability measures, and NRS scores were analyzed with analysis of variance. RESULTS: Reliability of NRS scores was excellent (interclass correlation coefficients 0.76 to 0.99). Analysis of NRS values corrected for pressure level revealed that there were main effects of site (P = .006), force (P < .001), size (P < .001), and shape (P < .001) but not side (P = .051). CONCLUSION: Reliability of intraoral novel palpometer measures of pressure sensitivity was excellent, and sensitivity to pressure stimulation was dependent on the applied force and physical properties of the add-on device. The study indicated that semi-quantitative assessment of intraoral mechanical sensitivity is feasible and could be applied in further studies on different intraoral pain conditions.

Optical-based artificial palpation sensors for lesion characterization.

Palpation techniques are widely used in medical procedures to detect the presence of lumps or tumors in the soft breast tissues. Since these procedures are very subjective and depend on the skills of the physician, it is imperative to perform detailed a scientific study in order to develop more efficient medical sensors to measure and generate palpation parameters. In this research, we propose an optical-based, artificial palpation sensor for lesion characterization. This has been developed using a multilayer polydimethylsiloxane optical waveguide. Light was generated at the critical angle to reflect totally within the flexible and transparent waveguide. When a waveguide was compressed by an external force, its contact area would deform and cause the light to scatter. The scattered light was captured by a high-resolution camera and saved as an image format. To test the performance of the proposed system, we used a realistic tissue phantom with embedded hard inclusions. The experimental results show that the proposed sensor can detect inclusions and provide the relative value of size, depth, and Young's modulus of an inclusion.

Gender differences in low and high pain palpation thresholds in the TMJ and neck areas.

The null hypothesis was that pain pressure thresholds are the same for young healthy males and females and do not differ between the temporomandibular joint (TMJ) and muscle sites. The aim of the current study was to compare pain pressure threshold levels using an algometer with a convex-formed contact piece and pressure increase rates similar to those in conventional finger palpation, making the conditions more like clinical examination of painful spots with commonly used physiotherapeutic methods. Healthy subjects, 12 male, mean age 22.5 +/- 1.62 (SD), and 12 female, 22.4 +/- 2.19 (SD), were enrolled. A transducer with a calibrated load range, 0 to 25 pounds, was used to measure pressure threshold levels for low (T1), VAS to approximately 2, and high (T2), VAS to approximately 8, pain levels bilaterally in the occipital (OC), sternocleidomastoid (SCM), upper trapezius (TU), transverse process of first vertebra (C1), and lateral temporomandibular joint (TMJ) areas. The null hypothesis was rejected. Levels T1 and T2 were significantly lower in the females in all tested areas. The range of the mean for T1 levels was 4.9-8.0 pounds for males and 3.2-5.1 pounds for females. For T2 levels, the range was 8.9-15.6 pounds for males and 6.2-10.3 pounds for females. Significant differences were found between muscle sites. These results support the use of different threshold levels: a) for males and females; and b) for different muscle areas.