[show abstract][hide abstract] ABSTRACT: Metatarsophalangeal joint deformity is associated with skin breakdown and amputation. The aims of this study were to compare intrinsic foot muscle deterioration ratios (ratio of adipose to muscle volume), and physical performance in subjects with diabetic neuropathy to controls, and determine their associations with 1) metatarsophalangeal joint angle and 2) history of foot ulcer.
23 diabetic, neuropathic subjects [59 (SD 10) years] and 12 age-matched controls [57 (SD 14) years] were studied. Radiographs and MRI were used to measure metatarsophalangeal joint angle and intrinsic foot muscle deterioration through tissue segmentation by image signal intensity. The Foot and Ankle Ability Measure evaluated physical performance.
The diabetic, neuropathic group had a higher muscle deterioration ratio [1.6 (SD 1.2) vs. 0.3 (SD 0.2), P<0.001], and lower Foot and Ankle Ability Measure scores [65.1 (SD 24.4) vs. 98.3 (SD 3.3) %, P<0.01]. The correlation between muscle deterioration ratio and metatarsophalangeal joint angle was r=-0.51 (P=0.01) for all diabetic, neuropathic subjects, but increased to r=-0.81 (P<0.01) when only subjects with muscle deterioration ratios >1.0 were included. Muscle deterioration ratios in individuals with diabetic neuropathy were higher for those with a history of ulcers.
Individuals with diabetic neuropathy had increased intrinsic foot muscle deterioration, which was associated with second metatarsophalangeal joint angle and history of ulceration. Additional research is required to understand how foot muscle deterioration interacts with other impairments leading to forefoot deformity and skin breakdown.
[show abstract][hide abstract] ABSTRACT: Reusable, publicly available data is a pillar of open science. The Cancer Imaging Archive (TCIA) is an open image archive service supporting cancer research. TCIA collects, de-identifies, curates and manages rich collections of oncology image data. Image data sets have been contributed by 28 institutions and additional image collections are underway. Since June of 2011, more than 2,000 users have registered to search and access data from this freely available resource. TCIA encourages and supports cancer-related open science communities by hosting and managing the image archive, providing project wiki space and searchable metadata repositories. The success of TCIA is measured by the number of active research projects it enables (>40) and the number of scientific publications and presentations that are produced using data from TCIA collections (39).
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 07/2013; 2013:1282-1285.
[show abstract][hide abstract] ABSTRACT: We investigated the capacity of bone quantity and bone geometric strength indices to predict ultimate force in the human second metatarsal (Met2) and third metatarsal (Met3). Intact lower extremity cadaver samples were measured using clinical, volumetric quantitative computed tomography (vQCT) with positioning and parameters applicable to in vivo scanning. During processing, raw voxel data (0.4mm isotropic voxels) were converted from Hounsfield units to apparent bone mineral density (BMD) using hydroxyapatite calibration phantoms to allow direct volumetric assessment of whole-bone and subregional metatarsal BMD. Voxel data were realigned to produce cross-sectional slices perpendicular to the longitudinal axes of the metatarsals. Average mid-diaphyseal BMD, bone thickness, and buckling ratio were measured using an optimized threshold to distinguish bone from non-bone material. Minimum and maximum moments of inertia and section moduli were measured in the mid-diaphysis region using both a binary threshold for areal, unit-density measures and a novel technique for density-weighted measures. BMD and geometric strength indices were strongly correlated to ultimate force measured by ex vivo 3-point bending. Geometric indices were more highly correlated to ultimate force than was BMD; bone thickness and density-weighted minimum section modulus had the highest individual correlations to ultimate force. Density-weighted geometric indices explained more variance than their binary analogs. Multiple regression analyses defined models that predicted 85-89% of variance in ultimate force in Met2 and Met3 using bone thickness and minimum section modulus in the mid-diaphysis. These results have implications for future in vivo imaging to non-invasively assess bone strength and metatarsal fracture risk.
Journal of biomechanics 12/2012; · 2.66 Impact Factor
[show abstract][hide abstract] ABSTRACT: Charcot neuroarthropathy (CN), an inflammatory condition characterized by rapid and progressive destruction of pedal bones and joints, often leads to deformity and ulceration in individuals with diabetes mellitus (DM) and peripheral neuropathy (PN). Repetitive, unperceived joint trauma may trigger initial CN damage, causing a proinflammatory cascade that can result in osteolysis and contribute to subsequent neuropathic fracture. We aimed to characterize osteolytic changes related to development and progression of CN by measuring bone mineral density (BMD) and geometric strength indices using volumetric quantitative computed tomography. Twenty individuals with DM+PN were compared to twenty age-, sex-, and race-matched individuals with DM+PN and acute CN. We hypothesized that individuals with acute CN would have decreased BMD and decreased total area, cortical area, minimum section modulus, and cortical thickness in the diaphysis of the second and fifth metatarsals. Results showed BMD was lower in both involved and uninvolved feet of CN participants compared to DM+PN participants, with greater reductions in involved CN feet compared to uninvolved CN feet. There was a non-significant increase in total area and cortical area in the CN metatarsals, which helps explain the finding of similar minimum section modulus in DM+PN and CN subjects despite the CN group's significantly lower BMD. Larger cortical area and section modulus are typically considered signs of greater bone strength due to higher resistance to compressive and bending loads, respectively. In CN metatarsals, however, these findings may reflect periosteal woven bone apposition, i.e., a hypertrophic response to injury rather than increased fracture resistance. Future research using these techniques will aid further understanding of the inflammation-mediated bony changes associated with development and progression of CN and other diseases.
[show abstract][hide abstract] ABSTRACT: We present an atlas-based registration method for bones segmented from quantitative computed tomography (QCT) scans, with the goal of mapping their interior bone mineral densities (BMDs) volumetrically. We introduce a new type of deformable atlas, called subdivision-embedded atlas, which consists of a control grid represented as a tetrahedral subdivision mesh and a template bone surface embedded within the grid. Compared to a typical lattice-based deformation grid, the subdivision control grid possesses a relatively small degree of freedom tailored to the shape of the bone, which allows efficient fitting onto subjects. Compared with previous subdivision atlases, the novelty of our atlas lies in the addition of the embedded template surface, which further increases the accuracy of the fitting. Using this new atlas representation, we developed an efficient and fully automated pipeline for registering atlases of 12 tarsal and metatarsal bones to a segmented QCT scan of a human foot. Our evaluation shows that the mapping of BMD enabled by the registration is consistent for bones in repeated scans, and the regional BMD automatically computed from the mapping is not significantly different from expert annotations. The results suggest that our improved subdivision-based registration method is a reliable, efficient way to replace manual labor for measuring regional BMD in foot bones in QCT scans.
Journal of Digital Imaging 10/2012; · 1.10 Impact Factor
[show abstract][hide abstract] ABSTRACT: Few studies exist for bone densitometry of the whole foot. A phantom study demonstrated the sources of error and necessary controls for accurate quantitative computed tomography of the foot. A loss in bone mineral density (BMD) in the small foot bones may be an early indicator of diabetic foot complications.
Volumetric quantitative computed tomography (vQCT) facilitates the assessment of pedal bone osteopenia, which, in the presence of peripheral neuropathy, may well be an early sign of diabetic foot deformity. To date, sources and magnitudes of error in foot vQCT measurements have not been reported.
Foot phantoms were scanned using a 64-slice CT scanner. Energy (in kilovoltage peak), table height, phantom size and orientation, location of "bone" inserts, insert material, location of calibration phantom, and reconstruction kernel were systematically varied during scan acquisition.
Energy (in kilovoltage peak) and distance from the isocenter (table height) resulted in relative attenuation changes from -5% to 22% and -5% to 0%, respectively, and average BMD changes from -0.9% to 0.0% and -1.1% to 0.3%, respectively, compared to a baseline 120-kVp scan performed at the isocenter. BMD compared to manufacturer-specified values ranged, on average, from -2.2% to 0.9%. Phantom size and location of bone-equivalent material inserts resulted in relative attenuation changes of -1.2% to 1.4% compared to the medium-sized phantom.
This study demonstrated that variations in kilovoltage peak and table height can be controlled using a calibration phantom scanned at the same energy and height as a foot phantom; however, error due to soft tissue thickness and location of bones within a foot cannot be controlled using a calibration phantom alone.
Osteoporosis International 12/2011; 23(7):1977-85. · 4.04 Impact Factor
[show abstract][hide abstract] ABSTRACT: To describe a new semiautomated method for segmenting and measuring the volume of the muscle, bone, and adipose (subcutaneous and intermuscular) tissue in calf muscle compartments using magnetic resonance (MR) images and determine the intrarater and interrater reproducibility of the measures.
Proton-density weighted MR images were acquired from the right calf of 21 subjects. Three raters segmented and measured the volumes of bones, adipose tissue, and five individual muscle compartments. Two raters repeated the segmentations. The intra- and interrater reproducibility of the measures (intraclass correlation coefficients; ICC) were determined using generalizability theory.
All ICC values were greater than 0.96. The average standard error of the mean (SEM) of all measures was 1.21 cm(3) and none were greater than 2.3 cm(3) . Essentially all variation (≥97% for all measures) was due to subject differences, indicating low error in the measurements.
The volumetric measurements for the bones, adipose tissue, and muscle in each of the compartments using MRI were highly reproducible. MRI can provide quantitative, reproducible volumetric measures of bone, adipose tissue, and individual muscle compartments in the calf. We believe these methods can be used to quantify specific muscle or adipose volumetric measures for other clinical or research purposes.
Journal of Magnetic Resonance Imaging 09/2011; 34(6):1285-94. · 2.57 Impact Factor
[show abstract][hide abstract] ABSTRACT: Diabetic foot diseases, such as ulcerations, infections, and neuropathic (Charcot's) arthropathy, are major complications of diabetes mellitus (DM) and peripheral neuropathy (PN) and may cause osteolysis (bone loss) in foot bones. The purposes of our study were to make computed tomography (CT) measurements of foot-bone volumes and densities and to determine measurement precision (percent coefficients of variation for root-mean-square standard deviations) and least significant changes (LSCs) in these percentages that could be considered biologically real with 95% confidence. Volumetric quantitative CT scans were performed and repeated on 10 young healthy subjects and 13 subjects with DM and PN. Two raters used the original- and repeat-scan data sets to make measurements of volumes and bone mineral densities (BMDs) of the tarsal and metatarsal bones of the 2 feet (24 bones). Precisions for the bones ranged from 0.1% to 0.9% for volume measurements and from 0.6% to 1.9% for BMD measurements. The LSCs ranged from 0.4% to 2.5% for volume measurements and from 1.5% to 5.4% for BMD measurements. Volumetric quantitative CT provides precise measurements of volume and BMD for metatarsal and tarsal bones, where diabetic foot diseases commonly occur.
Journal of Clinical Densitometry 06/2011; 14(3):313-20. · 1.71 Impact Factor
[show abstract][hide abstract] ABSTRACT: Measures of second-fourth metatarsophalangeal joint (MTPJ) angle (indicator of hammer toe deformity) and clinical measures of tibial torsion have limited evidence for validity and reliability. The purposes of this study are to determine: (1) reliability of using a 3D digitizer (Metrecom) and computed tomography (CT) to measure MTPJ angle for toes 2-4; (2) reliability of goniometer, 3D digitizer, and CT to measure tibial torsion; (3) validity of MTPJ angle measures for toes 2-4 using goniometry and 3D digitizer compared to CT (gold standard) and (4) validity of tibial torsion measures using goniometry and 3D digitizer (Metrecom) compared to CT (gold standard).
Twenty-nine subjects participated in this study. 27 feet with hammer toe deformity and 31 feet without hammer toe deformity were tested using standardized gonimetric, 3D digitizer and CT methods. ICCs (3,1), standard error of the measurement (SEM) values, and difference measures were used to characterize intrarater reliability. Pearson correlation coefficients and an analysis of variance were used to determine associations and differences between the measurement techniques.
3D digitizer and CT measures of MTPJ angle had high test-retest reliability (ICC = 0.95-0.96 and 0.98-0.99, respectively; SEM = 2.64-3.35 degrees and 1.42-1.47 degrees, respectively). Goniometry, 3D digitizer, and CT measures of tibial torsion had good test-retest reliability (ICC = 0.75, 0.85, and 0.98, respectively; SEM = 2.15 degrees, 1.74 degrees, and 0.72 degree, respectively). Both goniometric and 3D digitizer measures of MTPJ angle were highly correlated with CT measures of MTPJ angle (r = 0.84-0.90, r = 0.84-0.88, respectively) and tibial torsion (r = 0.72, r = 0.83). Goniometry, 3D digitizer, and CT measures were all different from each other for measures of hammer toe deformity (p < 0.001). Goniometry measures were different from CT measures and 3D digitizer measures of tibial torsion (p < 0.002). CT measures and 3D digitizer measures of tibial torsion were similar (p = 0.112).
These results suggest that 3D digitizer and CT scan measures of MTPJ angle and goniometric, 3D digitizer, and CT scan measures of tibial torsion are reliable. Goniometer and 3D digitizer measures of MTPJ angle and tibial torsion measures are highly correlated with the gold standard CT method indicating good validity of measures, but the measures are not interchangeable.
[show abstract][hide abstract] ABSTRACT: Bone mineral density (BMD) decreases rapidly with prolonged non-weight bearing. Maximizing the BMD response to reloading activities after NWB is critical to minimizing fracture risk.
for measuring individual tarsal and metatarsal BMD have not been available. This case report describes tarsal and metatarsal BMD with a reloading program, as revealed by quantitative computed tomography (QCT).
A 24-year-old woman was non-weight bearing for 6 weeks after right talocrural arthroscopy. Tarsal and metatarsal BMD were measured with QCT 9 weeks (before reloading) and 32 weeks (after reloading) after surgery. A 26-week progressive reloading program was completed. Change scores were calculated for BMD before reloading and BMD after reloading for the total foot (average of all tarsals and metatarsals), tarsals, metatarsals, bones of the medial column (calcaneus, navicular, cuneiforms 1 and 2, and metatarsal 1), and bones of the lateral column (calcaneus, cuboid, cuneiform 3, and metatarsals 2-5). The percent differences in BMD between the involved side and the uninvolved side were calculated.
Before reloading, BMD of the involved total foot was 9% lower than that on the uninvolved side. After reloading, BMD increased 22% and 21% for the total foot, 16% and 14% for the tarsals, 29% and 30% for the metatarsals, 14% and 15% for the medial column bones, and 28% and 26% for the lateral column bones on the involved and uninvolved sides, respectively. After reloading, BMD of the involved total foot remained 8% lower than that on the uninvolved side.
The increase in BMD with reloading was not uniform across all pedal bones; the metatarsals showed a greater increase than the tarsals, and the lateral column bones showed a greater increase than the medial column bones.
[show abstract][hide abstract] ABSTRACT: A new method for measuring bone mineral density (BMD) of the tarsal and metatarsals is described using volumetric quantitative computed tomography (VQCT) in subjects with diabetes mellitus and peripheral neuropathy. VQCT images of a single foot were acquired twice from eight subjects (mean age 51 [11 SD], seven males, one female). The cortical shells of the seven tarsal and five metatarsal bones were identified and semiautomatically segmented from adjacent bones. Volume and BMD of each bone were measured separately from the two acquired scans for each subject. Whole-bone semiautomatic segmentation measurement errors were determined as the root mean square coefficient of variation for the volume and BMD of 0.8% and 0.9%, respectively. In addition to the whole-bone segmentation methods, we performed atlas-based partitioning of subregions within the second metatarsal for all subjects, from which the volumes and BMDs were obtained for each subregion. The subregion measurement BMD errors (root mean square coefficient of variation) within the shaft, proximal end, and distal end were shown to vary by approximately 1% between the two scans of each subject. The new methods demonstrated large variations in BMDs between the 12 bones of the foot within a subject and between subjects, and between subregions within the second metatarsal. These methods can provide an important outcome measure for clinical research trials investigating the effects of interventions, aging, or disease progression on bone loss, or gain, in individual foot bones.
Journal of Digital Imaging 06/2008; 22(5):492-502. · 1.10 Impact Factor
[show abstract][hide abstract] ABSTRACT: There is evidence that appropriate footwear is an important factor in the prevention of foot pain in otherwise healthy people or foot ulcers in people with diabetes and peripheral neuropathy. A standard care for reducing forefoot plantar pressure is the utilization of orthotic devices such as total contact inserts (TCI) with therapeutic footwear. Most neuropathic ulcers occur under the metatarsal heads, and foot deformity combined with high localized plantar pressure, appear to be the most significant factors contributing to these ulcers. In this study, patient-specific finite element models of the second ray of the foot were developed to study the influence of TCI design on peak plantar pressure (PPP) under the metatarsal heads. A typical full contact insert was modified based on the results of finite element analyses, by inserting 4 mm diameter cylindrical plugs of softer material in the regions of high pressure. Validation of the numerical model was addressed by comparing the numerical results obtained by the finite element method with measured pressure distribution in the region of the metatarsal heads for a shoe and TCI condition. Two subjects, one with a history of forefoot pain and one with diabetes and peripheral neuropathy, were tested in the laboratory while wearing therapeutic shoes and customized inserts. The study showed that customized inserts with softer plugs distributed throughout the regions of high plantar pressure reduced the PPP over that of the TCI alone. This supports the outcome as predicted by the numerical model, without causing edge effects as reported by other investigators using different plug designs, and provides a greater degree of flexibility for customizing orthotic devices than current practice allows.
[show abstract][hide abstract] ABSTRACT: We present a fast, interactive method for separating bones that have been collectively segmented from a CT volume. Given user-provided seed points, the method computes the separation as a multi-way cut on a weighted graph constructed from the binary, segmented volume. By properly designing and weighting the graph, we show that the resulting cut can accurately be placed at bone-interfaces using only a small number of seed points even when the data is noisy. The method has been implemented with an interactive graphical interface, and used to separate the 12 human foot bones in 10 CT volumes. The interactive tool produced compatible result with a ground-truth separation, generated by a completely manual labelling procedure, while reducing the human interaction time from a mean of 2.4 hours per volume in manual labelling down to approximately 18 minutes.
Medical image computing and computer-assisted intervention : MICCAI ... International Conference on Medical Image Computing and Computer-Assisted Intervention. 02/2008; 11(Pt 1):296-304.
[show abstract][hide abstract] ABSTRACT: For segmentation and volume measurement of renal cysts and parenchyma from kidney MR images in subjects with autosomal dominant polycystic kidney disease (ADPKD), a semi-automated, multi-spectral anaylsis (MSA) method was developed and applied to T1- and T2-weighted MR images. In this method, renal cysts and parenchyma were characterized and segmented for their characteristic T1 and T2 signal intensity differences. The performance of the MSA segmentation method was tested on ADPKD phantoms and patients. Segmented renal cysts and parenchyma volumes were measured and compared with reference standard measurements by fluid displacement method in the phantoms and stereology and region-based thresholding methods in patients, respectively. As results, renal cysts and parenchyma were segmented successfully with the MSA method. The volume measurements obtained with MSA were in good agreement with the measurements by other segmentation methods for both phantoms and subjects. The MSA method, however, was more time-consuming than the other segmentation methods because it required pre-segmentation, image registration and tissue classification-determination steps.
[show abstract][hide abstract] ABSTRACT: Neuropathic (Charcot's) arthropathy (NCA) is a complication of diabetes mellitus which, in a high percentage of patients, leads to foot fracture, joint destruction, severe foot deformity, ulceration, instability, and possibly amputation. The development of new treatments is currently limited by the lack of biomarkers that are sensitive and specific indicators of NCA disease onset and treatment outcomes. There is evidence that those with NCA have low foot bone mineral densities (BMDs) and that foot BMDs further decrease during off-loading treatment. We have initiated a repeated measures cohort study in which clinical and radiological data are being collected with the objective to establish volumetric quantitative computed tomography (VQCT)-derived foot BMD as a candidate biomarker for acute NCA. This paper presents the study design, methods and preliminary results.
Life Science Systems and Applications Workshop, 2007. LISA 2007. IEEE/NIH; 12/2007
[show abstract][hide abstract] ABSTRACT: Ground reaction forces from walking result in stress (pressure) and soft tissue strain at the plantar aspect of the foot. Excessive plantar pressure and tissue strain on the insensate foot may lead to ulceration. Our study investigated the effect of therapeutic footwear and custom-made orthotic inserts on pressure and tissue strain along the second ray of the plantar foot, and how these two variables are associated.
Twenty subjects (mean age 57.3 [SD 9.3] years, 12 male, 8 female, body mass index 32.5 [SD 7.4] kg/m2) with diabetes mellitus, peripheral neuropathy, and a history of a plantar ulcer participated. Plantar pressure data were recorded during computed tomography scans for four conditions (barefoot, shoe, shoe+total contact insert, and shoe+total contact insert+metatarsal pad). For each condition tested, tissue strain and plantar pressure were determined at the second metatarsal head and at 15 other points along the second ray.
Differences were noted between the 4 conditions for pressure (P<0.004) and soft tissue strain (P<0.042) at the second metatarsal head. Correlation coefficients demonstrated an association between pressure and strain (Barefoot r=0.81, Shoe r=0.75, Shoe+total contact insert r=0.73, and Shoe+total contact insert+metatarsal pad r=0.44).
Footwear and orthotic devices tested in this study decreased pressure and soft tissue strain at the second ray of the foot, and these two variables were strongly related. A better understanding of the role tissue strain plays in distributing plantar forces may lead to improvements in the design of orthotic devices.
[show abstract][hide abstract] ABSTRACT: Standard prevention and treatment strategies to decrease peak plantar pressure include a total contact insert with a metatarsal pad, but no clear guidelines exist to determine optimal placement of the pad with respect to the metatarsal head. The purpose of this study was to determine the effect of metatarsal pad location on peak plantar pressure in subjects with diabetes mellitus and peripheral neuropathy.
Twenty subjects with diabetes mellitus, peripheral neuropathy, and a history of forefoot plantar ulcers were studied (12 men and eight women, mean age=57+/-9 years). CT determined the position of the metatarsal pad relative to metatarsal head and peak plantar pressures were measured on subjects in three footwear conditions: extra-depth shoes and a 1) total contact insert, 2) total contact insert and a proximal metatarsal pad, and 3) total contact insert and a distal metatarsal pad. The change in peak plantar pressure between shoe conditions was plotted and compared to metatarsal pad position relative to the second metatarsal head.
Compared to the total contact insert, all metatarsal pad placements between 6.1 mm to 10.6 mm proximal to the metatarsal head line resulted in a pressure reduction (average reduction=32+/-16%). Metatarsal pad placements between 1.8 mm distal and 6.1 mm proximal and between 10.6 mm proximal and 16.8 mm proximal to the metatarsal head line resulted in variable peak plantar pressure reduction (average reduction=16+/-21%). Peak plantar pressure increased when the metatarsal pad was located more than 1.8 mm distal to the metatarsal head line.
Consistent peak plantar pressure reduction occurred when the metatarsal pad in this study was located between 6 to 11 mm proximal to the metatarsal head line. Pressure reduction lessened as the metatarsal pad moved outside of this range and actually increased if the pad was located too distal of this range. Computational models are needed to help predict optimal location of metatarsal pad with a variety of sizes, shapes, and material properties.
Foot & Ankle International 02/2007; 28(1):84-8. · 1.47 Impact Factor
[show abstract][hide abstract] ABSTRACT: The primary objective of conservative care for the diabetic foot is to protect the foot from excessive pressures. Pressure reduction and redistribution may be achieved by designing and fabricating orthotic devices based on foot structure, tissue mechanics, and external loads on the diabetic foot. The purpose of this paper is to describe the process used for the development of patient-specific mathematical models of the second and third rays of the foot, their solution by the finite element method, and their sensitivity to model parameters and assumptions. We hypothesized that the least complex model to capture the pressure distribution in the region of the metatarsal heads would include the bony structure segmented as toe, metatarsal and support, with cartilage between the bones, plantar fascia and soft tissue. To check the hypothesis, several models were constructed with different levels of details. The process of numerical simulation is comprised of three constituent parts: model definition, numerical solution and prediction. In this paper the main considerations relating model selection and computation of approximate solutions by the finite element method are considered. The fit of forefoot plantar pressures estimated using the FEA models and those explicitly tested were good as evidenced by high Pearson correlations (r=0.70-0.98) and small bias and dispersion. We concluded that incorporating bone support, metatarsal and toes with linear material properties, tendon and fascia with linear material properties, soft tissue with nonlinear material properties, is sufficient for the determination of the pressure distribution in the metatarsal head region in the push-off position, both barefoot and with shoe and total contact insert. Patient-specific examples are presented.