Supraspinatus tendon micromorphology in individuals with subacromial pain syndrome.

STUDY DESIGN: Cross-sectional cohort. INTRODUCTION: Tendon collagen organization can be estimated by peak spatial frequency radius (PSFR) on ultrasound images. Characterizing PSFR can define the contribution of collagen disruption to shoulder symptoms. PURPOSE OF THE STUDY: The purpose of this was to characterize the (1) supraspinatus tendon PSFR in participants with subacromial pain syndrome (SPS) and healthy controls; (2) PSFR between participants grouped on a tendon visual quality score; and (3) relationship between PSFR with patient-reported pain, function, and shoulder strength. METHODS: Participants with SPS (n = 20) and age, sex, and arm-dominance-matched healthy controls (n = 20) completed strength testing in scaption and external rotation, and patient-reported pain, and functional outcomes. Supraspinatus tendon ultrasound images were acquired, and PSFR was calculated for a region of interest 15 mm medial to the supraspinatus footprint. PSFR was compared between groups using an independent t-test and an analysis of variance to compare between 3 groups for visually qualitatively rated tendon abnormalities. Relationships between PSFR with pain, function, and strength were assessed using Pearson correlation coefficient. RESULTS: Supraspinatus tendon PSFR was not different between groups (P = .190) or tendon qualitative ratings (P = .556). No relationship was found between PSFR and pain, functional loss, and strength (P > .05). CONCLUSIONS: Collagen disruption (PSFR) measured via ultrasound images of the supraspinatus tendon was not different between participants with SPS or in those with visually rated tendon defects. PSFR is not related to shoulder pain, function, and strength, suggesting that supraspinatus tendon collagen disorganization may not be a contributing factor to shoulder SPS. However, collagen disruption may not be isolated to a single region of interest. LEVEL OF EVIDENCE: 3b: case-control study.

Achilles and patellar tendon morphology in dancers with and without tendon pain.

OBJECTIVES: To examine Achilles and patellar tendon morphology in dancers with and without tendon pain. METHODS: Fifty-three dancers with and without Achilles and/or patellar tendon pain participated. Eleven age-matched non-dancers served as controls. Longitudinal ultrasound images of the middle and distal Achilles and proximal and distal patellar tendons were acquired. To assess macromorphology, the thickness of the middle and distal Achilles and proximal and distal patellar tendons were measured. Micromorphology was analyzed by selecting 2 x 2-mm2 regions of interest in the tendons; spectral analysis using the fast Fourier transform was run for several kernels (2 x 2-mm2 subimages) within each image, and the peak spatial frequency (PSF) was extracted. A one-way ANOVA compared asymptomatic, symptomatic, and control tendon thickness and PSF. RESULTS: Macromorphology: There was no significant difference between asymptomatic and symptomatic dancers in middle or distal Achilles tendon thickness and distal patellar tendon thickness. Proximal patellar tendons in control subjects were thinner than those in asymptomatic (p=0.036) and symptomatic (p=0.003) dancers. Micromorphology: There was no significant difference in PSF between asymptomatic and symptomatic dancers and controls in the Achilles or patellar tendon. CONCLUSION: Increased proximal patellar tendon thickness without changes in tendon micromorphology suggests that tendon adaptations are more likely activity-related and less likely influenced by degeneration.

Functional Transcranial Doppler Ultrasound for Monitoring Cerebral Blood Flow.

Functional transcranial Doppler ultrasound (fTCD) is the use of transcranial Doppler ultrasound (TCD) to study neural activation occurring during stimuli such as physical movement, activation of tactile sensors in the skin, and viewing images. Neural activation is inferred from an increase in the cerebral blood flow velocity (CBFV) supplying the region of the brain involved in processing sensory input. For example, viewing bright light causes increased neural activity in the occipital lobe of the cerebral cortex, leading to increased blood flow in the posterior cerebral artery, which supplies the occipital lobe. In fTCD, changes in CBFV are used to estimate changes in cerebral blood flow (CBF). With its high temporal resolution measurement of blood flow velocities in the major cerebral arteries, fTCD complements other established functional imaging techniques. The goal of this Methods paper is to give step-by-step instructions for using fTCD to perform a functional imaging experiment. First, the basic steps for identifying the middle cerebral artery (MCA) and optimizing the signal will be described. Next, placement of a fixation device for holding the TCD probe in place during the experiment will be described. Finally, the breath-holding experiment, which is a specific example of a functional imaging experiment using fTCD, will be demonstrated.

Longitudinal Quantitative Ultrasonic Analysis of Patellar Tendon in a Collegiate Athlete After Bilateral Debridement: A Case Report.

CONTEXT: A National Collegiate Athletic Association Division I female basketball athlete (age = 20 years, height = 190.5 cm, mass = 87 kg) had chronic patellar tendinopathy. INTERVENTION(S): After undergoing unsuccessful conservative treatments, the athlete underwent bilateral open patellar debridement surgery. Pain and dysfunction were assessed via the Victorian Institute of Sport-P (VISA-P) score with concurrently collected B-mode ultrasound images of the patellar tendon throughout a 12-month rehabilitation. RESULTS: Peak spatial frequency radius (PSFR), a quantitative ultrasound measure previously shown to be correlated with collagen organization, was compared with changes in VISA-P scores. Overall increases in PSFR values across 0°, 30°, 60°, and 90° of knee flexion were observed throughout recovery. Despite increased PSFR values and returning to sport, the athlete reported substantial pain. CONCLUSIONS: In this level 3 exploration case report, we provide novel insight into ultrasonically measured structural changes of the patellar tendon after surgery and during rehabilitation of an athlete with chronic tendinopathy. Perceived pain measurements were not necessarily related to structural adaptations.

Most High-Intensity Transient Signals Are Not Associated With Specific Surgical Maneuvers.

BACKGROUND: Mortality after congenital heart defect surgery has dropped dramatically in the last few decades. Current research on long-term outcomes has focused on preventing secondary neurological sequelae, for which embolic burden is suspected. In children, little is known of the correlation between specific surgical maneuvers and embolic burden. Transcranial Doppler ultrasound is highly useful for detecting emboli but has not been widely used with infants and children. METHODS: Bilateral middle cerebral artery blood flow was continuously monitored from sternal incision to chest closure in 20 infants undergoing congenital heart defect repair or palliative surgery. Embolus counts for specific maneuvers were recorded using widely accepted criteria for identifying emboli via high-intensity transient signals (HITS). RESULTS: An average of only 13% of all HITS detected during an operation were correlated with any of the surgical maneuvers of interest. The highest mean number of HITS associated with a specific maneuver occurred during cross-clamp removal. Cross-clamp placement also had elevated HITS counts that significantly differed from other maneuvers. CONCLUSIONS: In this study of infants undergoing cardiac surgery with cardiopulmonary bypass, the great majority of HITS detected are not definitively associated with a specific subset of surgical maneuvers. Among the measured maneuvers, removal of the aortic cross-clamp was associated with the greatest occurrence of HITS. Future recommended research efforts include identifying and confirming other sources for emboli and longitudinal outcome studies to determine if limiting embolic burden affects long-term neurological outcomes.

Real-Time Cerebral Hemodynamic Response to Tactile Somatosensory Stimulation.

BACKGROUND AND PURPOSE: Recent studies in rodents suggest that somatosensory stimulation could provide neuroprotection during ischemic stroke by inducing plasticity in the cortex-vasculature relationship. While functional magnetic resonance imaging (fMRI) has shown that somatosensory stimulation increases cerebral blood flow (CBF) over several seconds, subsecond changes in CBF in the basal cerebral arteries have rarely been studied due to temporal resolution limitations. This study characterized hemodynamic changes in the middle cerebral arteries (MCAs) during somatosensory stimulation with high temporal resolution (100 samples/s) using functional transcranial Doppler ultrasound (fTCD). METHODS: Pneumotactile somatosensory stimulation, consisting of punctate pressure pulses traversing the glabrous skin of the hand at 25 cm/s, was used to induce CBF velocity (CBFV) response curves. Changes in CBFV were measured in the bilateral MCAs using fTCD. All 12 subjects underwent three consecutive trials consisting of 20 seconds of stimulation followed by 5 minutes of rest. RESULTS: Sharp, bilateral increases in CBFV of about 20% (left MCA = 20.5%, right MCA = 18.8%) and sharp decreases in pulsatility index of about 8% were observed during stimulation. Left lateralization of up to 3.9% was also observed. The magnitude of the initial increase in CBFV showed significant adaptation between subsequent trials. CONCLUSIONS: Pneumotactile somatosensory stimulation is a potent stimulus that can evoke large, rapid hemodynamic changes, with adaptation between successive stimulus applications. Due to its high temporal resolution, fTCD is useful for identifying quickly evolving hemodynamic responses, and for correlating changes in hemodynamic parameters such as pulsatility index (PI) and CBFV.

The Breath-Hold Acceleration Index: A New Method to Evaluate Cerebrovascular Reactivity using Transcranial Doppler.

BACKGROUND AND PURPOSE: Cerebrovascular reactivity (CR) is an ideal biomarker to detect cerebrovascular damage. CR can be quantified by measuring changes in cerebral blood flow velocity (CBFV) resulting from a CO2  vasodilatory stimulus, often using the breath-holding index (BHI). In this method, transcranial Doppler (TCD) ultrasound is used to measure CBFV changes in the middle cerebral artery (MCA) during a breath-hold maneuver. Despite its convenience, BHI has high variability. Changing body position may contribute to potential variability. It is important to determine if CR differs with body position. The aims of this study were, first, to propose an alternative, more robust index to evaluate CR using a breath-hold maneuver; second, investigate the effect of body position on CR measured with conventional (BHI) and a new proposed index. METHODS: Ten healthy young volunteers held their breath for 30 seconds on a tilt table. CR was calculated at five different angles using two indices: the conventional BHI, and the breath-hold acceleration index (BHAI), a new index obtained by linear regression of the most linear portion of the mean velocity change during the breath-hold maneuver. The regression represents acceleration (change in blood flow velocity per unit of time) sampled at each cardiac cycle. RESULTS: The mean coefficient of variation was 43.7% lower in BHAI in comparison with BHI. Neither index was statistically significant between body positions (P > .05). CONCLUSIONS: BHAI has less variability in comparison with the conventional standard BHI. Additionally, neither index showed statistical significance in CR based on change in body position.

Variations in plantar pressure variables across five cardiovascular exercises.

PURPOSE: To quantify variations in plantar pressure variables in healthy adults across five cardiovascular exercises. METHODS: Ten young (19-35 yr old) and 10 middle-aged (45-60 yr old) individuals participated. After equipment familiarization, plantar pressure data were recorded during walking, running, elliptical training, stair climbing, and recumbent biking. Separate one-way analyses of variance with repeated measures identified significant differences in pressure variables across exercises and between age groups under the forefoot, arch, and heel. RESULTS: Forefoot: Peak pressures were higher during walking (253 kPa), running (251 kPa), and elliptical training (213 kPa) than stair climbing (130 kPa) and recumbent biking (41 kPa; P < or = 0.001). Biking pressures were lower than all other conditions (P < 0.001). Arch: Pressures were higher during running (144 kPa) compared with all other conditions (P < or = 0.001). Intermediate-level pressures during walking (119 kPa) and elliptical training (102 kPa) exceeded those during stair climbing (80 kPa; P < or = 0.002). Pressures were lowest during recumbent biking (33 kPa; P < 0.001). Heel: Pressures were highest during walking (215 kPa) and running (188 kPa), exceeding those recorded during all other activities (P < 0.001). Moderate elliptical training pressures (94 kPa) surpassed stair climbing values (66 kPa; P = 0.014). Pressures were lowest during recumbent biking (25 kPa; P < 0.001). The only significant difference identified between age groups was a larger arch contact area in the young compared with middle-aged, when averaged across exercises (P = 0.011). CONCLUSIONS: When protection of the forefoot is important (e.g., diabetic foot neuropathies), biking and stair climbing offer optimal pressure reductions. If protecting the heel from high pressures and forces is warranted, recumbent biking, stair climbing, and elliptical training provide greater relief.

Direct comparison of feature tracking and autocorrelation for velocity estimation.

Feature tracking is an algorithm for estimating tissue motion and blood flow using pulse-echo ultrasound. It was proposed as a computationally simpler alternative to other techniques such as autocorrelation and time-domain cross correlation. The advantage of feature tracking is that it selectively extracts easily identifiable parts of the speckle signal (e.g., the local maxima), reducing the amount of information being processed. Studies on feature tracking to date have used stationary, speckle-generating targets to simulate blood flow. Also, feature tracking has not been compared with accepted commercial methods. This study directly compares feature tracking performance with the complex autocorrelation method, which is the most common color flow algorithm. Experiments were performed with both a rotating string phantom and a commercial flow phantom surrounded by tissue-mimicking material, using 2.25 MHz and 3.5 MHz transducers, under more realistic signal-to-clutter (-15 to -35 dB) and signal-to-noise ratios (SNR) (15 dB to 3 dB) than previous translating-phantom tests. The feature tracking approach is shown to produce mean estimates comparable to autocorrelation (R2 = 0.9954 and 0.9960 for 6-sample and 12-sample autocorrelation, respectively, and R2 = 0.9998 for both 6-sample and 12-sample feature tracking) for velocities ranging from 10 to 100 cm/s. The variance of feature-tracking estimates is shown to compare favorably to the complex autocorrelation approach using the same number of ensemble flow samples (19 to 28% lower standard deviation for 3.5 MHz, 36 to 55% lower standard deviation for 2.25 MHz). However, linear regression of the feature locations does not produce an appreciable improvement in estimation variance. Discussion of the need for further research, particularly in the areas of feature detection and feature correspondence, is given.

Changes in tendon spatial frequency parameters with loading.

To examine and compare the loading related changes in micro-morphology of the patellar tendon. Fifteen healthy young males (age 19±3yrs, body mass 83±5kg) were utilised in a within subjects matched pairs design. B mode ultrasound images were taken in the sagittal plane of the patellar tendon at rest with the knee at 90° flexion. Repeat images were taken whilst the subjects were carrying out maximal voluntary isometric contractions. Spatial frequency parameters related to the tendon morphology were determined within regions of interest (ROI) from the B mode images at rest and during isometric contractions. A number of spatial parameters were observed to be significantly different between resting and contracted images (Peak spatial frequency radius (PSFR), axis ratio, spatial Q-factor, PSFR amplitude ratio, and the sum). These spatial frequency parameters were indicative of acute alterations in the tendon micro-morphology with loading. Acute loading modifies the micro-morphology of the tendon, as observed via spatial frequency analysis. Further research is warranted to explore its utility with regard to different loading induced micro-morphological alterations, as these could give valuable insight not only to aid strengthening of this tissue but also optimization of recovery from injury and treatment of conditions such as tendinopathies.

Cerebral hemodynamics during scene viewing: Hemispheric lateralization predicts temporal gaze behavior associated with distinct modes of visual processing.

Systematic patterns of eye movements during scene perception suggest a functional distinction between 2 viewing modes: an ambient mode (characterized by short fixations and large saccades) thought to reflect dorsal activity involved with spatial analysis, and a focal mode (characterized by long fixations and small saccades) thought to reflect ventral activity involved with object analysis. Little neuroscientific evidence exists supporting this claim. Here, functional transcranial Doppler ultrasound (fTCD) was used to investigate whether these modes show hemispheric specialization. Participants viewed scenes for 20 s under instructions to search or memorize. Overall, early viewing was right lateralized, whereas later viewing was left lateralized. This right-to-left shift interacted with viewing task (more pronounced in the memory task). Importantly, changes in lateralization correlated with changes in eye movements. This is the first demonstration of right hemisphere bias for eye movements servicing spatial analysis and left hemisphere bias for eye movements servicing object analysis. (PsycINFO Database Record

Circular ultrasound compounding by designed matrix weighting.

Spatial compounding is an imaging technique that aims to improve image contrast by combining partially decor-related images acquired at different angles or positions. In conventional spatial compounding, data sets are combined with equal weighting. Here, we describe an alternative method of reconstruction using algorithms which weight the data based on a "quality" matrix. The quality matrix is derived from beamforming characteristics. For each data set, the reliability of the data is assumed to vary spatially. By compounding the data based on the quality matrix, a complete image is formed. Here, we describe the construction of a rotational translation stage and tissue-mimicking phantoms that are used in conjunction with a commercial medical ultrasound machine to test our reconstruction algorithms. The new algorithms were found to increase the contrast-to-speckle ratio of simulated cysts and tumors by 61% from raw data, and to significantly increase edge definition of small embedded targets. The new method shows promise as a computationally efficient method of improving contrast and resolution in ultrasound images. The method should be particularly useful in breast imaging, where images from multiple angles can be acquired without interference from bone or air.

Maximal dynamic grip force and wrist torque: the effects of gender, exertion direction, angular velocity, and wrist angle.

The objective of this study was to examine the effects of gender, exertion direction, angular velocity and wrist angle on simultaneous grip force and wrist torque under the isokinetic condition. The study used 20 participants (10 males and 10 females) and included 6 angular velocities (15, 30, 45, 60, 75, and 90 degrees /s) and 2 wrist exertion directions (flexion and extension) over the wrist range of motion of 70 degrees flexion to 60 degrees extension in 5 degrees increments. Similar to other studies, males and flexion exertion produced larger forces than females and extension exertion, respectively. However, the largest forces were generated at near extreme flexion of the wrist and the dependent variable of angular velocity was not practically significant. These results can contribute to the evaluation of cumulative trauma syndromes, but there is a need for more research on the dynamic measures of the hand and wrist complex and for standard development for dynamic force measurement.

Ultrasound-Based Tendon Micromorphology Predicts Mechanical Characteristics of Degenerated Tendons.

The purpose of this study was to explore the relationship between tendon micro-morphology quantified from a sonogram and tendon mechanical characteristics measured in vivo. Nineteen adults (nine with unilateral Achilles tendinosis) participated. A commercial ultrasound scanner was used to capture longitudinal B-mode ultrasound images from the mid-portion of bilateral Achilles tendons and a custom image analysis program was used to analyze the spatial frequency content of manually defined regions of interest; in particular, the average peak spatial frequency of the regions of interest was acquired. In addition, a dynamometer and a motion analysis system indirectly measured the tendon mechanical (stiffness) and material (elastic modulus) properties. The peak spatial frequency correlated with tendon stiffness (r = 0.74, p = 0.02) and elastic modulus (r = 0.65, p = 0.05) in degenerated tendons, but not healthy tendons. This is the first study relating the mechanical characteristics of degenerated human Achilles tendon using a non-invasive micro-morphology analysis approach.

Functional Transcranial Doppler Ultrasound for Measurement of Hemispheric Lateralization During Visual Memory and Visual Search Cognitive Tasks.

Functional transcranial Doppler ultrasound (fTCD) is a noninvasive sensing modality that measures cerebral blood flow velocity (CBFV) with high temporal resolution. CBFV change is correlated to changes in cerebral oxygen uptake, enabling fTCD to measure brain activity and lateralization with high accuracy. However, few studies have examined the relationship of CBFV change during visual search and visual memory tasks. Here a protocol to compare lateralization between these two similar cognitive tasks using fTCD is demonstrated. Ten healthy volunteers (age 21±2 years) were shown visual scenes on a computer and performed visual search and visual memory tasks while CBFV in the bilateral middle cerebral arteries was monitored with fTCD. Each subject completed 40 trials, consisting of baseline (25 s), calibration (variable), instruction (2.5 s), and task (20 s) epochs. Lateralization was computed for each task by calculating the bilateral CBFV envelope percent change from baseline and subtracting the right side from the left side. The results showed significant lateralization ( ) of the visual memory and visual search tasks, with memory reaching lateralization of 1.6% and search reaching lateralization of 0.5%, suggesting that search is more right lateralized (and therefore may be related to "holistic" or global perception) and memory is more left lateralized (and therefore may be related to local perception). This method could be used to compare cerebral activity for any related cognitive tasks as long as the same stimulus is used in all tasks. The protocol is straightforward and the equipment is inexpensive, introducing a low-cost high temporal resolution technique to further study lateralization of the brain.

Enabling real-time ultrasound imaging of soft tissue mechanical properties by simplification of the shear wave motion equation.

Ultrasound based shear wave elastography (SWE) is a technique used for non-invasive characterization and imaging of soft tissue mechanical properties. Robust estimation of shear wave propagation speed is essential for imaging of soft tissue mechanical properties. In this study we propose to estimate shear wave speed by inversion of the first-order wave equation following directional filtering. This approach relies on estimation of first-order derivatives which allows for accurate estimations using smaller smoothing filters than when estimating second-order derivatives. The performance was compared to three current methods used to estimate shear wave propagation speed: direct inversion of the wave equation (DIWE), time-to-peak (TTP) and cross-correlation (CC). The shear wave speed of three homogeneous phantoms of different elastic moduli (gelatin by weight of 5%, 7%, and 9%) were measured with each method. The proposed method was shown to produce shear speed estimates comparable to the conventional methods (standard deviation of measurements being 0.13 m/s, 0.05 m/s, and 0.12 m/s), but with simpler processing and usually less time (by a factor of 1, 13, and 20 for DIWE, CC, and TTP respectively). The proposed method was able to produce a 2-D speed estimate from a single direction of wave propagation in about four seconds using an off-the-shelf PC, showing the feasibility of performing real-time or near real-time elasticity imaging with dedicated hardware.

A new method for shear wave speed estimation in shear wave elastography.

Visualization of mechanical properties of tissue can aid in noninvasive pathology diagnosis. Shear wave elastography (SWE) measures the elastic properties of soft tissues by estimation of local shear wave propagation speed. In this paper, a new robust method for estimation of shear wave speed is introduced which has the potential for simplifying continuous filtering and real-time elasticity processing. Shear waves were generated by external mechanical excitation and imaged at a high frame rate. Three homogeneous phantoms of varying elastic moduli and one inclusion phantom were imaged. Waves propagating in separate directions were filtered and shear wave speed was estimated by inversion of the 1-D first-order wave equation. Final 2-D shear wave speed maps were constructed by weighted averaging of estimates from opposite traveling directions. Shear wave speed results for phantoms with gelatin concentrations of 5%, 7%, and 9% were 1.52 ± 0.10 m/s, 1.86 ± 0.10 m/s, and 2.37 ± 0.15 m/s, respectively, which were consistent with estimates computed from three other conventional methods, as well as compression tests done with a commercial texture analyzer. The method was shown to be able to reconstruct a 2-D speed map of an inclusion phantom with good image quality and variance comparable to conventional methods. Suggestions for further work are given.

In vivo lateral blood flow velocity measurement using speckle size estimation.

In previous studies, we proposed blood measurement using speckle size estimation, which estimates the lateral component of blood flow within a single image frame based on the observation that the speckle pattern corresponding to blood reflectors (typically red blood cells) stretches (i.e., is "smeared") if blood flow is in the same direction as the electronically controlled transducer line selection in a 2-D image. In this observational study, the clinical viability of ultrasound blood flow velocity measurement using speckle size estimation was investigated and compared with that of conventional spectral Doppler of carotid artery blood flow data collected from human patients in vivo. Ten patients (six male, four female) were recruited. Right carotid artery blood flow data were collected in an interleaved fashion (alternating Doppler and B-mode A-lines) with an Antares Ultrasound Imaging System and transferred to a PC via the Axius Ultrasound Research Interface. The scanning velocity was 77 cm/s, and a 4-s interval of flow data were collected from each subject to cover three to five complete cardiac cycles. Conventional spectral Doppler data were collected simultaneously to compare with estimates made by speckle size estimation. The results indicate that the peak systolic velocities measured with the two methods are comparable (within ±10%) if the scan velocity is greater than or equal to the flow velocity. When scan velocity is slower than peak systolic velocity, the speckle stretch method asymptotes to the scan velocity. Thus, the speckle stretch method is able to accurately measure pure lateral flow, which conventional Doppler cannot do. In addition, an initial comparison of the speckle size estimation and color Doppler methods with respect to computational complexity and data acquisition time indicated potential time savings in blood flow velocity estimation using speckle size estimation. Further studies are needed for calculation of the speckle stretch method across a field of view and combination with an appropriate axial flow estimator.

Physical activity discrimination improvement using accelerometers and wireless sensor network localization - biomed 2013.

Automating documentation of physical activity data (e.g., duration and speed of walking or propelling a wheelchair) into the electronic medical record (EMR) offers promise for improving efficiency of documentation and understanding of best practices in the rehabilitation and home health settings. Commercially available devices which could be used to automate documentation of physical activities are either cumbersome to wear or lack the specificity required to differentiate activities. We have designed a novel system to differentiate and quantify physical activities, using inexpensive accelerometer-based biomechanical data technology and wireless sensor networks, a technology combination that has not been used in a rehabilitation setting to date. As a first step, a feasibility study was performed where 14 healthy young adults (mean age = 22.6 ± 2.5 years, mean height = 173 ± 10.0 cm, mean mass = 70.7 ± 11.3 kg) carried out eight different activities while wearing a biaxial accelerometer sensor. Activities were performed at each participant’s self-selected pace during a single testing session in a controlled environment. Linear discriminant analysis was performed by extracting spectral parameters from the subjects’ accelerometer patterns. It is shown that physical activity classification alone results in an average accuracy of 49.5%, but when combined with rule-based constraints using a wireless sensor network with localization capabilities in an in silico simulated room, accuracy improves to 99.3%. When fully implemented, our technology package is expected to improve goal setting, treatment interventions and patient outcomes by enhancing clinicians’ understanding of patients’ physical performance within a day and across the rehabilitation program.