Dynamic instrumented palpation - a new method for soft tissue quality assessment: application to prostate disease diagnosis.

The objective is to establish the feasibility of using dynamic instrumented palpation, a novel technique of low-frequency mechanical testing, applied here to diagnose soft tissue condition. The technique is applied, in vitro, to samples of excised prostate gland affected by benign prostate hyperplasia and/or prostate cancer. Particular attention is paid to the relationship between the histological structure of the tissue and the dynamic mechanical properties in an attempt to separate patient-specific aspects from histopathological condition (i.e. prostate cancer or benign prostate hyperplasia). The technique is of clinical interest because it is potentially deployable in vivo. Prostate samples were obtained from a total of 36 patients who had undergone transurethral resection of the prostate to relieve prostatic obstruction and 4 patients who had undergone radical cystoprostatectomy for bladder cancer. Specimens (chips) recovered from transurethral resection of the prostate were of nominal size 5 mm × 8 mm and thicknesses between 2 and 4 mm, whereas those from the cystoprostatectomy were in the form of transverse slices of thickness approximately 6 mm. Specimens were mechanically tested by a controlled strain cyclic compression technique, and the resulting dynamic mechanical properties expressed as the amplitude ratio and phase difference between the cyclic stress and cyclic strain. After mechanical testing, the percentage areas of glandular and smooth muscle were measured at each probe point. Good contrast between the dynamic modulus of chips from benign prostate hyperplasia and prostate cancer patients was demonstrated, and absolute values similar to those published by other authors are reported. For the slices, modulus values were considerably higher than for chips, and good in-patient mechanical contrast was revealed for predominantly nodular and predominantly stromal areas. Extending this classification between patients required pattern recognition techniques. Overall, the study has demonstrated that dynamic mechanical properties can potentially be used for diagnosis of prostate condition using in vivo measurements.

Quantitative mechanical assessment of the whole prostate gland ex vivo using dynamic instrumented palpation.

An instrumented palpation sensor, designed for measuring the dynamic modulus of tissue in vivo, has been developed and trialled on ex vivo whole prostate glands. The sensor consists of a flexible membrane sensor/actuator with an embedded strain gauge and is actuated using a dynamically varying airflow at frequencies of 1 and 5 Hz. The device was calibrated using an indentation stiffness measurement rig and gelatine samples with a range of static modulus similar to that reported in the literature for prostate tissue. The glands were removed from patients with diagnosed prostate cancer scheduled for radical prostatectomy, and the stiffness was measured within 30 min of surgical removal. Each prostate was later examined histologically in a column immediately below each indentation point and graded into one of the four groups; normal, benign prostatic hyperplasia, cancerous and mixed cancer and benign prostatic hyperplasia. In total, 11 prostates were assessed using multiple point probing, and the complex modulus at 1 and 5 Hz was calculated on a point-by-point basis. The device yielded values of quasi-static modulus of 15 ± 0.5 kPa and dynamic modulus of 20 ± 0.5 kPa for whole prostates, and a sensitivity of up to 80% with slightly lower specificity was achieved on diagnosis of prostate cancer using a combination of mechanical measures. This assessment did not take into account some obvious factors such as edge effects, overlap and clinical significance of the cancer, all of which would improve performance. The device, as currently configured, is immediately deployable in vivo. A number of improvements are also identified which could improve the sensitivity and specificity in future embodiments of the probe.

Validity of a Newly Developed Tri-axial Sensor for Clinical Breast Examination Skills Assessment.

The clinical breast examination is a critical exam for early detection of breast cancer. Assessment methods are needed to determine competency and skill mastery for experts and novices. The 3D sensor was developed to capture hand shear and normal forces conducted during an exam. Trials were conducted to record exploratory maneuvers used during the exam. The sensor system was found to be a reliable method for capturing exploratory maneuvers.

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.

Caliper measurement to improve clinical assessment of palpable neck lumps.

INTRODUCTION: One-stop neck lump clinics with ultrasonography and cytopathology support are an expensive and finite resource. Consequently, many neck lump patients are assessed in general ear, nose and throat or head and neck clinics. Optimal clinical assessment of neck lump size is important to guide investigation, monitor change and provisionally stage nodal disease. The aims of this study were to investigate whether caliper measurement is more accurate than clinical palpation in assessing neck lump size and whether caliper measurement of neck lump size correlates closely with accurate ultrasonography measurement. METHODS: A prospective study was carried out involving 50 patients with clinically palpable neck lumps presenting to the one-stop neck lump clinic. Long and short axis neck lump dimensions were estimated first by clinical palpation and second by caliper measurement. Estimations were compared with accurate ultrasonography measurement. RESULTS: The mean combined long and short axis measurement deviation from accurate ultrasonography measurement was smaller for caliper measurement (7.80 mm) than for clinical palpation (12.38 mm) (p <0.01). There was no significant difference observed between combined axis ultrasonography and combined axis caliper measurement of neck lumps (p = 0.462). CONCLUSIONS: Caliper measurement is more accurate than clinical palpation in estimating the size of clinically palpable neck lumps. The use of calipers to measure the skin surface dimensions of palpable neck lumps is statistically comparable to accurate ultrasonography measurement.

New palpometer with implications for assessment of deep pain sensitivity.

The aims of this study were to compare test-retest variability and accuracy measures between (1) manual palpation and a novel palpometer and (2) different force levels. Sixteen clinicians were instructed to target 0.5, 1.0, and 2.0 kg on a force meter using manual palpation and the new palpometer (adjustable spring-coil with a small pin touching the examiner's hand when the correct pressure is reached). In all experiments, 10 consecutive measures of the force levels were recorded. The coefficient of variation (CV), actual force levels, and relative differences between target level and actual force level were compared between experiments and target levels. All outcome parameters had significantly lower values for the new palpometer than for manual palpation in a force-dependent manner (p<0.004). CVs and actual force levels were significantly different between all target levels (p<0.004). The new palpometer had low test-retest variability and provides a more accurate pressure stimulus than manual palpation.

Development of a mechanical stimulator and force measurement system for the assessment of nociceptive thresholds in pigs.

A mechanical stimulator and force measurement system was developed to quantify withdrawal thresholds to noxious mechanical stimulation of the foot in young pigs. The device and associated PC software have design and control features not previously used in other mechanical stimulators. The device, capable of delivering stimulus rates between 2 and 17 mm/s, maximum force 27 N, was validated in a cross-over study on 8 juvenile pigs (6-8 weeks of age) to check the repeatability and reliability of force threshold measurement and assess its ability to measure changes in force threshold following an inflammatory challenge. Threshold force measurements were obtained over several time periods before and after the pigs received a 0.25 ml subcutaneous injection of 3% carrageenan in 0.01 M phosphate buffered saline (PBS) or PBS in the hind foot. Consistent withdrawal thresholds were measured in injected (ipsilateral) and contralateral feet, 24 h and 30 min prior to injection (mean 8.4; 95% CI 7.1-9.7 N). Carrageenan injection, but not PBS injection, induced a significant decrease in withdrawal thresholds 90 min after injection (4.6+/-0.9 N) which remained reduced for 6h after injection. The testing system provided reliable and reproducible measurements of foot withdrawal thresholds to noxious mechanical force in young pigs (weight range 32-39 kg), and was capable of detecting and monitoring changes in threshold sensitivity following the induction of acute local inflammation in the foot. The system is suitable for studying nociceptive mechanisms in pigs.

Assessment of accuracy of acetabular cup orientation in CT-free navigated total hip arthroplasty.

We have used the Orthopilot (Aesculap AG, Tuttlingen, Germany) computed tomography (CT)-free navigation system to ensure accurate and reproducible acetabular cup orientation. In this system, cup orientation is assessed with respect to bony configuration as determined by palpation of the anatomical landmarks (the bilateral anterosuperior iliac spines and the upper margin of the pubic symphysis). In this study, intraoperative cup orientation as presented by the OrthoPilot navigation system was compared with the value obtained through postoperative radiological assessment using CT Digital Imaging and Communications in Medicine (DICOM) data and Medical Image Processing, Analysis, and Visualization (MIPAV; National Institutes of Health, US Department of Health and Human Services, Bethesda, Maryland). Intra- and postoperative results obtained from 27 consecutive navigated total hip arthroplasties (THAs) were analyzed. For cup positioning, the desired inclination and anteversion angles were set within the "safe zone" proposed by Lewinnek. In the intraoperative evaluation, the mean inclination angle as determined by the navigation system was 43.5 degrees +/- 2.17 degrees (range, 39.9 degrees to 46.6 degrees ) after the final implantation. In contrast, the mean inclination angle determined by postoperative calculation using MIPAV was 44.9 +/- 3.3 degrees (range, 38.1 degrees to 55.0 degrees ). A discrepancy of >5 degrees was observed in only 1 hip. For the anteversion, the mean intra- and postoperative values were 11.1 degrees +/- 5.6 degrees (range, 0 degrees to 17.8 degrees ) and 13.5 degrees +/- 5.9 degrees (range, 5.1 degrees to 21.6 degrees ), respectively. Again, a discrepancy of >5 degrees was observed in 1 case. Mean differences between the intra- and postoperative values were 1.9 degrees +/- 1.9 degrees and 2.6 degrees +/- 1.6 degrees for inclination and anteversion, respectively. A good agreement between the intraoperative values presented by the navigation system and those in the postoperative CT evaluation was observed, and the validity of this navigation system was confirmed.

Markov model assessment of subjects' clinical skill using the E-Pelvis physical simulator.

Inherent difficulties evaluating clinical competence of physicians has led to the widespread use of subjective skill assessment techniques. Inspired by an analogy between spoken language and surgical procedure, a generalized methodology using Markov models (MMs), independent of the modality under study, was developed. The methodology applied to an endoscopic experiment in "Generalized approach for modeling minimally invasive surgery as a stochastic process using a discrete Markov model" by J. Rosen et al. (IEEE Trans. Biomed. Eng., Vol. 53, No. 3, pp. 399-413, Mar. 2006) is modified and applied to data collected with the E-Pelvis physical simulator. The simulator incorporates five contact pressure sensors located in key anatomical landmarks. Two 32-state fully connected MMs are used, one for each skill level. Each state corresponds to a unique five-dimensional signature of contact pressures. Statistical distances measured between models representing subjects with different skill levels are sensitive enough to provide an objective measure of medical skill level. The method was tested with 41 expert subjects and 41 novice subjects in addition to the 30 subjects used for training the MM. Of the 82 subjects, 76 (92%) were classified correctly. Unique state transitions as well as pressure magnitudes for corresponding states were found to be skill dependent. The "white box" nature of the model provides insight into the examination process performed.

Ultrasound palpation sensor for tissue thickness and elasticity measurement--assessment of transverse carpal ligament.

Palpation is a traditional diagnostic procedure for health care professionals to use their fingers to touch and feel the body soft tissues. It is a common clinical approach, though it is rather subjective and qualitative and the palpation results may vary among different people. Tissue ultrasound palpation sensor (TUPS) provides a feasible solution that makes the palpation of soft tissues not subjective feeling any more. It is comprised of an ultrasound transducer together with a load cell to form the finger-sized probe. The probe is used to push against the soft tissue surface to measure the thickness and elasticity of the soft tissues. TUPS has been successfully applied to the assessment of various human tissues. Recently, we have improved TUPS, which can now be linked to personal computer (PC) via universal serial bus (USB) and provide a better user-interface. The information of ultrasound signal and indentation force is displayed on PC in real time during measurement. In this paper, we introduce the recent application of TUPS for the assessment of the transverse carpal ligament. The tissues at the carpal tunnel regions of five normal male subjects were tested using TUPS. The results showed that the average thickness of the tissues covering the carpal tunnel ligament and the tunnel region was 7.98+/-1.05 mm and 9.59+/-1.12 mm, respectively. Under a compression force of 20 N applied by a cylindrical ultrasound indentor with a diameter of 9 mm, the stiffness of the soft tissue layer and the tunnel region was 6.72+/-2.10 N/mm and 15.63+/-8.42 N/mm, respectively. It is expected that TUPS can be a potential tool for non-invasive assessment of carpal tunnel syndrome.

Assessment of the level of sensory block after subarachnoid anesthesia using a pressure palpator.

UNLABELLED: In a cross-over study, we compared two methods of assessing the level of sensory block during subarachnoid anesthesia: the traditional pinprick sensation or a novel pressure palpator exerting a pressure of 650 g. Fifty patients scheduled for transurethral surgery under subarachnoid anesthesia were randomly assigned to be tested for spread of sensory block. In Group 1, the pressure palpator was followed by pinprick; in Group 2, the reverse sequence was used. Evaluation was performed 15 and 25 min after the subarachnoid injection of 2 mL of 5% lidocaine hyperbaric solution. In Group 1, the level of sensory block assessed with the pressure palpator was 1.7 +/- 3.2 cm (0.5 +/- 1.2 dermatomes) higher than that with the pinprick at 15 min, and 2.2 +/- 3.4 cm (0.6 +/- 1.0 dermatomes) higher than that with the pinprick 25 min after the block. In Group 2, the difference was accentuated. The level of sensory block assessed by pinprick 15 min after subarachnoid lidocaine was 5.7 +/- 4.8 cm (1.2 +/- 0.9 dermatomes) lower than the level with the pressure palpator, and 4.2 +/- 3.3 cm (0.9 +/- 0.6 dermatomes) lower than that with the pressure palpator at 25 min. In all instances, the pressure palpator gave a significantly higher assessment than the pinprick. We conclude that the pressure palpator, when preceded by the pinprick test, is associated with an increased threshold. This method may be useful in assessing the sensory block produced by subarachnoid anesthesia. IMPLICATIONS: A novel pressure palpator that maintains the integrity of the epidermis was used to assess the level of sensory block after subarachnoid anesthesia and was compared with the standard method of the pinprick sensation. This method assessed the block consistently higher than the pinprick method, but it may have advantages as a noninvasive sensory test.