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

Advanced ultrasound in the diagnosis of prostate cancer

The diagnosis of prostate cancer (PCa) can be challenging due to the limited performance of current diagnostic tests, including PSA, digital rectal examination and transrectal conventional US. Multiparametric MRI has improved PCa diagnosis and is recommended prior to biopsy; however, mp-MRI does miss a substantial number of PCa. Advanced US modalities include transrectal prostate elastography and contrast-enhanced US, as well as improved B-mode, micro-US and micro-Doppler techniques. These techniques can be combined to define a novel US approach, multiparametric US (mp-US). Mp-US improves PCa diagnosis but is not sufficiently accurate to obviate the utility of mp-MRI. Mp-US using advanced techniques and mp-MRI provide complementary information which will become even more important in the era of focal therapy, where precise identification of PCa location is needed.

A Standard Methodology to Characterize the Intrinsic Material Properties of Compliant Test Stimuli

Understanding how we perceive differences in material compliance, or 'softness,' is a central topic in the field of haptics. The intrinsic elasticity of an object is the primary factor thought to influence our perceptual estimates. Therefore, most studies test and report the elasticity of their stimuli, typically as stiffness or modulus. However, many reported estimates are of very high magnitude for silicone-elastomers, which may be due to artifacts in characterization technique. This makes it very difficult to compare the perceptual results between the studies. The work herein defines a standardized and easy-to-implement way to characterize test stimuli. The procedure involves the unconstrained, uniaxial compression of a plate into cylindrical substrates 10 mm tall by 10 mm diameter. The resultant force-displacement data are straightforwardly converted into stress-strain data, from which a modulus is readily derived. This procedure was used to re-characterize stimuli from prior studies. The revised results from the validated method herein are 200-1,100 percent lower than modulus values either reported and/or approximated from stiffness. This is practically significant when differences of 10-15 percent are perceptually discriminable. The re-characterized estimates are useful in comparing prior studies and designing new studies. Furthermore, this characterization methodology may help more readily bridge studies on perception with those designing technology.

Force-Rate Cues Reduce Object Deformation Necessary to Discriminate Compliances Harder than the Skin

Grasping and manipulating an object requires us to perceive its material compliance. Compliance is thought to be encoded by relationships of force, displacement, and contact area at the finger pad. Prior work suggests that objects must be sufficiently deformed to become discriminable, but the utility of time-dependent cues has not been fully explored. The studies herein find that the availability of force-rate cues improve compliance discriminability so as to require less deformation of stimulus and finger pad. In particular, we tested the impact of controlling force-rate and displacement-rate cues in passive touch psychophysical experiments. An ink-based method to mark the finger pad was used to measure contact area per stimulus, simultaneously with displacement and force. Compliances spanned a range harder and softer than the finger pad. The results indicated harder compliances were discriminable at lower peak forces when the stimulus control mode was displacement-rate (0.5 N) compared to force-rate (1.3 N). That is, when displacement-rate was controlled to be equal between the two compliances, the resultant force-rate psychophysical cues could be more readily discriminated. In extending prior studies, while some magnitude of finger pad deformation may be sufficient for discriminability, temporal cues tied to force afford more efficient judgments.

WFUMB Guidelines and Recommendations on the Clinical Use of Ultrasound Elastography: Part 5. Prostate

The World Federation for Ultrasound in Medicine and Biology (WFUMB) has produced guidelines for the use of elastography techniques, including basic science, breast, liver and thyroid elastography. Here we present elastography in prostate diseases. For each available technique, procedure, reproducibility, results and limitations are analyzed and recommendations are given. Finally, recommendations are given based on the level of evidence of the published literature and on the WFUMB expert group's consensus. This document has a clinical perspective and is aimed at assessing the usefulness of elastography in the management of prostate diseases.

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

Distinguishing an object's compliance, into percepts of "softness" and "hardness," is crucial to our ability to grasp and manipulate it. Biomechanical cues at the skin's surface such as contact area and force rate have been thought to help encode compliance. However, no one has directly measured contact area with compliant materials, and few studies have considered compliances softer than the fingerpad. Herein, we developed a novel method to precisely measure the area in contact between compliant stimuli and the fingerpad, at given levels of force and displacement. To determine the method's robustness, we conducted psychophysical and biomechanical experiments with human subjects. The results indicate that cues including contact area at stimulus peak force of 3 Newtons, force rate over stimulus movement and at peak force, displacement and/or time to reach peak force may help in discriminating compliances while the directional spread of contact area is less important. Between softer and harder compliances, some cues were slightly more evident, though not yet definitively. Based upon the method's utility, the next step is to conduct broader experiments to distill the mixture of cues that encode compliance. The importance of such work lies in building haptic displays, for example, to render virtual tissues.

Prostate cancer: a comparison of the diagnostic performance of transrectal ultrasound versus contrast enhanced transrectal ultrasound in different clinical characteristics

To determine whether contrast-enhanced transrectal ultrasound (CE-TRUS) is superior to transrectal ultrasound (TRUS) on diagnosis of prostate cancer, 317 patients were processed TRUS examination with or without SonoVue, then biopsy was performed. Sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) of two techniques were compared in multiple subgroups of PSA level, Digital rectal examination (DRE) and prostate volume on biopsy results. In PSA 4-10 ng/ml and DRE negative groups, CE-TRUS had greater sensitivity and accuracy compared with TRUS by patient (P = .004 and .003; .013 and .005 respectively) and greater sensitivity, accuracy, PPV and NPV by core. When prostate volume was 45-65 ml, CE-TRUS had greater specificity and accuracy by patient and all diagnostic performances were statistically significant by core. CE-TRUS is superior to TRUS on diagnosis of prostate cancer in a designed patient population with lower PSA level, DRE negative findings and modest prostate volume.

Teaching and practising rectal examination in Pakistan

BACKGROUND

Digital rectal examination (DRE) is an integral part of physical examination. The teaching and practising of DRE should start early in medical school for mastering the skills to perform DRE by the time of graduation. In recent years it has been observed that medical students are reluctant to learn and practise DRE because of a perception of the reduced importance of DRE as compared with other modalities of investigation. We evaluated the knowledge and attitude of medical students and interns towards the teaching and practising of DRE.

METHODS

We conducted a cross-sectional survey of four medical institutions in Karachi, Pakistan.

RESULTS

Of the 398 participants included in the study, almost half were medical students. Almost all (98%) of the participants appreciated the importance of DRE. Only half of the participants reported having been formally taught about DRE before reaching the final year of medical school. Only 16 per cent reported the use of manikins as an aide to demonstrate and practise DRE. The median number of times respondents had performed DRE was one. Patients' refusal to grant consent was the most common reason given for not performing DRE. Students are reluctant to learn and practise DRE because of a perception of its reduced importance

CONCLUSION

Teaching sessions on DRE using manikins are suggested to begin early in medical school. It is also suggested that a minimum number of DREs should be performed under supervision before the completion of the internship.

Neural coding of passive lump detection in compliant artificial tissue

Here, we investigate the neural mechanisms of detecting lumps embedded in artificial compliant tissues. We performed a combined psychophysical study of humans performing a passive lump detection task with a neurophysiological study in nonhuman primates (Macaca mulatta) where we recorded the responses of peripheral mechanoreceptive afferents to lumps embedded at various depths in intermediates (rubbers) of varying compliance. The psychophysical results reveal that human lump detection is greatly degraded by both lump depth and decreased compliance of the intermediate. The neurophysiology results reveal that only the slowly adapting type 1 (SA1) afferents provide a clear spatial representation of lumps at all depths and that the representation is affected by lump size, depth, and compliance of the intermediate. The rapidly adapting afferents are considerably less sensitive to the lump. We defined eight neural response measures that we hypothesized could explain the psychophysical behavior, including peak firing rate, spatial spread of neural activity, and additional parameters derived from these measures. We find that peak firing rate encodes the depth of the lump, and the neural spatial spread of the SA1 response encodes for lump size but not lump shape. We also find that the perception of lump size may be affected by the compliance of the intermediate. The results show that lump detection is based on a spatial population code of the SA1 afferents, which is distorted by the depth of the lump and compliance of the tissue.

Left lobe of the prostate during clinical prostate cancer screening: the dark side of the gland for right-handed examiners

BACKGROUND

The predictive value of the abnormality side during digital rectal examination (DRE) has never been studied, suggesting that physicians examined the left lobe of the gland as well as the right lobe. We aimed to assess the predictive value of the side of DRE abnormality for prostate cancer (PCa) detection and aggressiveness in right-handed urologists.

METHODS

An analysis of a prospective database was carried out that included all consecutive men undergoing prostate biopsies between 2001 and 2012. The main end point was the predictive value of the abnormality side during DRE for cancer detection in clinically suspicious unilateral T2 disease. The diagnostic performance of left- versus right-sided abnormality was also assessed in terms of sensitivity, specificity and negative/positive predictive values.

RESULTS

Overall, 308 patients had a suspicious unilateral clinical disease (detection rate 57.5%). The cancer detection rate was significantly higher in case of left-sided compared with right-sided clinical T2 stage (odds ratio 2.1). In case of left-sided disease, the number of positive cores, the rate of perineural invasion, the rate of primary grade 4 pattern and the percentage of cancer involvement per core were significantly higher compared with those reported for right-sided disease. The predictive value of abnormality laterality for cancer detection and aggressiveness remained statistically independent in multivariate models. The positive predictive value for cancer detection was 64.6 in case of suspicious left-sided disease versus 46.9 in case of right-sided disease.

CONCLUSIONS

The risks of detecting PCa and aggressive disease on biopsy are significantly higher when DRE reveals a suspicious left-sided clinical disease as compared with right-sided disease. Right-handed physicians should be aware of this variance in diagnostic performance and potential underdetection of left-sided clinical disease, and should improve their examination of the left lobe of the gland by conducting longer exams or changing the patient's position.

Simplifying touch data from tri-axial sensors using a new data visualization tool

Quantification and evaluation of palpation is a growing field of research in medicine and engineering. A newly developed tri-axial touch sensor has been designed to capture a multi-dimensional profile of touch-loaded forces. We have developed a data visualization tool as a first step in simplifying interpretation of touch for assessing hands-on clinical performance.

Haptic Detection of Artificial Tumors by Hand and with a Tool in a MIS Environment

Minimally invasive surgery uses optical cameras and special surgical tools in order to operate from an environment one step removed from the body cavity of interest to the surgeon. It has been suggested that constraints posed by this arrangement, in particular the lack of direct haptic feedback to the surgeon, may affect the surgeon's ability to identify tissues and accurately maneuver inside the body cavity. In the present study, the ability of laypeople to detect artificial tumors of various hardness values embedded in silicone gels was assessed in a simulated MIS environment. Participants explored the gels under three conditions all with remote viewing; using the unrestricted bare finger, using a stick-like surgical tool also unrestricted, and using the surgical tool restricted by its insertion through an operating port as in MIS. Participants were significantly more accurate and more efficient at tumor detection with the finger as compared to the other methods of exploration, and they were also better at detecting harder tumors as compared to softer ones. The potential implications of these results for the role of haptic perception in minimally invasive surgery are discussed.

Socio-Technical Systems Analysis in Health Care: A Research Agenda

Given the complexity of health care and the 'people' nature of healthcare work and delivery, STSA (Sociotechnical Systems Analysis) research is needed to address the numerous quality of care problems observed across the world. This paper describes open STSA research areas, including workload management, physical, cognitive and macroergonomic issues of medical devices and health information technologies, STSA in transitions of care, STSA of patient-centered care, risk management and patient safety management, resilience, and feedback loops between event detection, reporting and analysis and system redesign.

Construct validity in a high-fidelity prostate exam simulator

BACKGROUND

All health care practitioners should be facile in the digital rectal exam (DRE) as it provides prostate, rectal and neurological information. The purpose of this study was first to justify our hypothesis that tissue elasticity is indicative of carcinomatous changes. Second, we employed urological surgeons to evaluate our prostate simulator in three ways: (1) authenticate that the elasticity of the simulated prostates accurately represents the range of normal prostate stiffness, (2) determine the range of nodule size reasonably palpable by DRE and (3) discern what degree of elasticity difference within the same prostate suggests malignancy.

METHODS

Institutional Review Board-approved materials characterization, human-subjects experiments, histopathology and chart abstraction of clinical history were performed. Material characterization of 21 ex-vivo prostatectomy specimens was evaluated using a custom-built, portable spherical indentation device while a novel prostate simulator was employed to measure human-subject perception of prostatic state.

RESULTS

From the materials characterization, the measurements of the 21 gross prostates and 40 cross-sections yielded 306 data points. Within the same prostate, cancer was always stiffer. Of the seven cases with an abnormal DRE, the DRE accurately identified adenocarcinoma in 85%. From the human-subjects experiments, the simulated prostates evaluated by urologists ranged in stiffness from 8.9 to 91 kPa, mimicking the range found on ex vivo analysis of 4.6-236.7 kPa. The urological surgeons determined the upper limit of stiffness palpated as realistic for a healthy prostate was 59.63 kPa while the lower limit of stiffness was 27.1 kPa. Nodule size less than 7.5 mm was felt to be too small to reasonably palpate.

CONCLUSIONS

We found it is not the absolute elasticity of the nodule, but rather the relationship of the nodule with the background prostate elasticity that constitutes the critical tactile feedback. Prostate simulator training may lead to greater familiarity with pertinent diagnostic cues and diagnosis of prostate cancer.

A novel approach to assessing changes in prostate stiffness with age using virtual touch tissue quantification

OBJECTIVES

Virtual touch tissue quantification is a promising new implementation of the acoustic radiation force impulse ultrasound technique. The purposes of this study were to describe the normal shear wave velocity values of the prostate by virtual touch tissue quantification and to examine the clinical usefulness of this procedure in evaluation of age-related shear wave velocity changes in the prostate.

METHODS

One hundred twenty healthy volunteers were involved in this study. They were divided into 3 groups (40 participants per group): young (<30 years), middle aged (30-60 years), and old (>60 years). The shear wave velocity was measured at the inner and outer glands of the prostate at the maximum depth (~5.5 cm) in each participant.

RESULTS

The mean shear wave velocities ± SD at the inner gland of the prostate in the young, middle-aged, and old groups were 0.86 ± 0.21, 1.17 ± 0.42, and 1.82 ± 0.61 m/s, respectively, whereas the velocities at the outer gland in the respective groups were 0.85 ± 0.32, 1.15 ± 0.49, and 1.87 ± 0.75 m/s. The shear wave velocities did not differ between the inner and outer glands in any age group. They were all significantly greater in the old group than in the young and middle-aged groups (P < .05). Moreover, the shear wave velocities at the inner and outer glands all correlated significantly with age.

CONCLUSIONS

Virtual touch tissue quantification can provide numerical measurements of prostate stiffness and can effectively and objectively indicate age-related changes in prostate stiffness by measuring shear wave velocity values.