Biomedical subjects

P K Commean

Publications and source records attributed to P K Commean.

13 recordsLinked to original sources

PubMed1999

Computer-assisted 3D reconstruction of serial sections of cortical bone to determine the 3D structure of osteons.

The objective of this study was to create three-dimensional (3D) images for the histomorphological study of osteons. Medical imaging technology was used to register digitized 2D images of serial decalcified histological sections of bone, to segment the tissues of interest from the surrounding tissues, and to create 3D reconstructions from the segmented structures. Examination of the 3D reconstructions did not support suggestions in the literature that osteons have a spiraling organization. In contrast, the 3D reconstructions indicated that osteons have a complex pattern of organization that is dominated by branching. Examination of the reconstructions also suggested that osteons described in the literature as being dumbbell shaped are actually artifacts of the plane of sectioning. This study demonstrated the applicability of imaging and visualization technology developed for the 3D reconstruction of medical images to the reconstruction of digitized 2D images of serial sections of bone and additionally demonstrated the feasibility of using 3D reconstructions for the histomorphological study of osteons.

Animals↗

PubMed1999

Use of computed tomography and plantar pressure measurement for management of neuropathic ulcers in patients with diabetes.

BACKGROUND AND PURPOSE: Total contact casting is effective at healing neuropathic ulcers, but patients have a high rate (30%-57%) of ulcer recurrence when they resume walking without the cast. The purposes of this case report are to describe how data from plantar pressure measurement and spiral x-ray computed tomography (SXCT) were used to help manage a patient with recurrent plantar ulcers and to discuss potential future benefits of this technology. CASE DESCRIPTION: The patient was a 62-year-old man with type 1 diabetes mellitus (DM) of 34 years' duration, peripheral neuropathy, and a recurrent plantar ulcer. Although total contact casting or relieving weight bearing with crutches apparently allowed the ulcer to heal, the ulcer recurred 3 times in an 18-month period. Spiral x-ray computed tomography and simultaneous pressure measurement were conducted to better understand the mechanism of his ulceration. OUTCOMES: The patient had a severe bony deformity that coincided with the location of highest plantar pressures (886 kPa). The results of the SXCT and pressure measurement convinced the patient to wear his prescribed footwear always, even when getting up in the middle of the night. The ulcer healed in 6 weeks, and the patient resumed his work, which required standing and walking for 8 to 10 hours a day. DISCUSSION: Following intervention, the patient's recurrent ulcer healed and remained healed for several months. Future benefits of these methods may include the ability to define how structural changes of the foot relate to increased plantar pressures and to help design and fabricate optimal orthoses.

Casts, Surgical↗

PubMed1998

Below-knee residual limb shape change measurement and visualization.

OBJECTIVE: The ability to measure and visualize shape change (deformation) of a residual limb within and between prostheses is an important step toward improved prosthetic fit assessment. The objective was to develop measurement and visualization methods for below-knee residual limb soft tissue shape change after donning and loading a prosthesis to detect small shape changes (30mm or less). DESIGN: Spiral X-ray computed tomography imaging was utilized to acquire 3D volumetric data of the below-knee residual limb and prosthesis in situ from poor- and a good-fitting prostheses without and with a load. A new sum projection depth-shaded cylindrical mapping technique to measure and visualize small changes in shape was developed. From the volumetric data, the relative displacement of small lead markers placed on the residual limb's skin surface were measured using multiplanar reconstruction images and cylindrical maps. Displacement measurements averaging 15mm or less were obtained. RESULTS: The precision and accuracy was 1mm and 2mm, respectively, when measuring the shape change or deformation of the skin surface from the sum projection cylindrical maps. The skin surface deformation was at least 7mm or greater when comparing marker locations between scans with the prostheses in situ. CONCLUSION: These new image-based measurement and visualization methods provide a feasible means for measuring and displaying lower extremity residual limb shape change within and between different prostheses with and without loading.

Adult↗

PubMed1997

Lower extremity residual limb slippage within the prosthesis.

OBJECTIVE: The ability to measure skin surface slippage relative to the internal wall of a lower extremity prosthesis under various loading conditions is important for evaluation of socket fit and function, and creation of finite element models. Skin surface three-dimensional (3D) shape measurements with tracking of fiducial displacements in situ under axial loading of the prosthesis have not previously been reported. Analysis of slippage within the prosthesis has been performed using a new experimental measurement method based on spiral x-ray computed tomography (SXCT) imaging. DESIGN: Small lead markers were placed on the residuum of an adult with a below-knee amputation, and SXCT scans were obtained with the prosthesis in situ under two static axial loading conditions (44.5N and 178N). The 3D scan data were used to assess slippage with three methods: gross displacement of the tibia and distal end of the residuum; relative displacement of markers; and distance measurements between markers. RESULTS: The markers affixed to the below-knee skin surface within the prosthesis were measured. The skin slipped from 2 to 6 mm relative to the internal prosthesis wall when an additional load of 133.5N was applied in the axial direction to the distal end of the prosthesis. The tibial remnant moved 10.0 mm distally relative to the prosthesis internal wall. CONCLUSION: This method provides a feasible means for measuring residuum skin slippage relative to the prosthesis and skin deformation relative to tibia within an in situ prosthesis under load.

Artificial Limbs↗

PubMed1997

Finite element modeling and experimental verification of lower extremity shape change under load.

Prediction and measurement of residuum shape change inside the prosthesis under various loading conditions is important for prosthesis design and evaluation. Residual limb surface measurements with the prosthesis in situ were used for construction of a finite element model (FEM). These surface measurements were obtained from volumetric computed tomography. A new experimental method for modeling the shape of the in situ lower residual limb was developed based on spiral X-ray computed tomography (SXCT) imaging. The p-version of the finite element method was used for estimating the material properties from known load and displacement data. A homogeneous, isotropic, linear constitutive model with accommodation of the constitutive soft and hard tissues of the residuum was evaluated with static axial loading applied to the in situ prosthesis and compared with experimental results obtained in a human volunteer. Two FEMs were created for similar coronal cross sections of the below knee residuum under two loading conditions. Agreement between observed (from SXCT) and predicted (from FEA) residual limb shape changes inside the prosthesis were maximized with a single modulus of elasticity for the residuum soft tissue of 0.06 MPa, consistent with previously published results. This methodology provides a framework to predict and objectively evaluate FEMs and determine residuum material properties by inverse methods.

Anthropometry↗

PubMed1996

Precision of surface measurements for below-knee residua.

OBJECTIVE: To determine the absolute and relative precision of geometric measurements made of below knee (BK) residua and their BK plaster positive casts using calipers, electromagnetic digitizer, optical surface scanner (OSS), and spiral x-ray computed tomography (SXCT). DESIGN: The experimental measurement protocol for a single measurement session was as follows: Dot markers were placed on the residuum, and volume and distances were measured using water displacement and calipers; residuum was measured using electromagnetic digitizer; residuum was scanned using three-dimensional (3D) OSS; a negative plaster cast of subject's residuum was made; the residuum was scanned using SXCT scanner. These steps were repeated at a second measurement session. Plaster positive casts were constructed and subsequently measured using the same protocol. PARTICIPANTS: Thirteen adult below-knee amputee volunteers (subjects) participated in the study, and nine subjects returned for a second measurement session. The study group consisted of 9 men and 4 women; 10 Caucasians and 3 African Americans. RESULTS: Distance measurements for all measurement devices were repeatable within 1% in vivo and within 0.5% on plaster casts; and volumes were within 1% in vivo and within 0.1% on plaster casts. Distance measurements for each device were precise within 3% in vivo and within 1% on plaster casts; and volumes were within 5% in vivo and within 6% on plaster casts when compared with caliper and water displacement measures. CONCLUSION: These measurement systems were found to be substantially equivalent in terms of repeatability and precision for measurement of lower extremity residua.

Adult↗

PubMed1996

Residual-limb shape change: three-dimensional CT scan measurement and depiction in vivo.

PURPOSE: To perform quantitative evaluation of lower-extremity prosthesis fit by using spiral computed tomography (CT). MATERIALS AND METHODS: Two spiral CT scans were obtained at each of two different sessions in seven adult patients who had undergone amputation below the knee. A rigid-body transformation of the tibia was computed and used to align paired (intra- and intersession) spiral CT data sets for each individual in a common coordinate system. Paired scans in each individual were compared to assess registration and precision of soft-tissue change measurement. Clinical prosthesis fit evaluation was demonstrated in an adult amputee volunteer who underwent CT evaluation while wearing two different prostheses. RESULTS: In the seven patients examined, more than 90% of the measured soft-tissue volume displacements between sessions could be explained as true differences. Precision error of soft-tissue volume change was approximately 13 cm3, or approximately 1% error relative to the mean volume. Volumetric changes due to different prostheses were substantially larger than the random error. CONCLUSION: Registration of CT volumetric data sets to quantify residual-limb soft-tissue envelope change in lower-limb prosthetics is precise and can be used to detect the effect of prosthesis shape alterations.

Adult↗

PubMed1996

Design of a 3-D surface scanner for lower limb prosthetics: a technical note.

A three-dimensional (3-D) noncontact optical surface range sensing imaging system that captures the entire circumferential and distal end surfaces of lower limb residua in less than 1 second has been developed. The optical surface scanner (OSS) consists of four charge injection device (CID) cameras and three white light projectors, mounted on a rigid frame surrounding the subject's residuum, allowing 360 degrees surface coverage of the lower residual limb. Anatomic 3-D computer graphics reconstruction of a residuum surface, recorded with the OSS imaging system, is used for visualization and measurement. One cubical and two spherical calibration test objects were used to obtain a system precision of less than 1 mm. In a study conducted with 13 persons with below knee (BK) amputation, the OSS system was compared to calipers, electromagnetic digitizer, and volumetric computed tomography with better than 1 mm precision on plaster positive casts and approximately 2 mm on the residual limbs.

Amputation, Surgical↗

PubMed1995

Validation of spiral CT and optical surface scanning for lower limb stump volumetry.

Spiral X-ray Computed Tomography (SXCT), Optical Surface Scanning (OSS), and hydrostatic weighing methods were used to measure stump volume of trans-tibial amputees. The precision and accuracy of these methods were assessed in a validation study. A repeated measures analysis of variance statistical design was employed that required each participant to be measured (scanned) twice at each of two separate measurement sessions. For OSS and SXCT, each scan was segmented twice to determine intra-observer error. Plaster cast replicas of subject stumps were formed by certified prosthetists to serve as a reference standard. Accuracy (bias) of SXCT and OSS was determined by comparison to volumetry by hydrostatic weighing. Ten trans-tibial amputees were recruited for this study and nine completed both sessions. Plaster replica measurement precision error relative to the mean was found to be less than 1% for all modalities. The precision was slightly inferior on subjects, 1.1% and 2.2% error for hydrostatic weighting and OSS respectively, due to patient instability during measurement, but was better with SXCT where the subjects' stumps were stabilized during scan acquisition. The OSS and SXCT methods offer advantages over hydrostatic weighing and other volumetry methods since the volume data are represented digitally and can be analyzed in multiple ways. SXCT enables study of the stump and its internal tissues with the prosthesis in place. It was found that SXCT is comparable to hydrostatic weighing in both precision and accuracy. While OSS had a high precision and reproducibility, it was found to have an associated bias.

Adult↗

PubMed1994

Quantification of facial surface change using a structured light scanner.

Three-dimensional surface changes that accompany facial surgical procedures were measured noninvasively and evaluated quantitatively. An optical three-dimensional surface scanner with 360-degree surface coverage of a subject's head and a subsecond data acquisition was used. The scanner employs six pairs of "white light" pattern projectors and digital TV cameras. A noncontact optical method to quantify facial surface morphology and objectively assess change resulting from reconstructive or cosmetic plastic surgery has been developed. This quantification technique was implemented and tested with the three-dimensional range scanner. This technique defines the entire surface of the head and face, as opposed to the conventional manual method of measuring surface points or facial landmarks. The method allows facial volume change assessment. The method was tested by repeatedly scanning a volunteer who was injected subcutaneously with known volumes of anesthetic solution. The measured and injected volumes were compared and showed little difference.

Computer Graphics↗

PubMedDate not supplied

Volumetric measurement of renal cysts and parenchyma using MRI: phantoms and patients with polycystic kidney disease.

We have developed an MR method to measure the volumes of renal cysts and parenchyma in patients with polycystic kidney disease. Phantoms were designed to simulate polycystic kidneys. Four patients were recruited. MR scans were performed on the phantoms and patients. A stereology technique was applied for image segmentation and volume measurement. Volumetric measurement of renal cysts and parenchyma was accurate in phantom studies and reliable in both phantom and patient studies in these limited examples.

Adult↗

PubMedDate not supplied

Assessment of the diabetic foot using spiral computed tomography imaging and plantar pressure measurements: a technical report.

Persons with diabetes mellitus (DM) and peripheral neuropathy are at high risk for skin breakdown due to unnoticed excessive pressures to the plantar foot during walking. We developed methods that combined spiral x-ray computed tomography (SXCT) imaging and plantar pressure analysis to quantify internal foot structure and external pressure during plantar loading. Methods were tested using a subject with DM who had a plantar ulcer, and a healthy control. SXCT measurements were within 2 mm of truth and SXCT plantar recordings were within 6.5% of walking trials. Hammer toe deformity (second toe), severe atrophy of the intrinsic muscles and less contact area during plantar loading, and a peak plantar pressure three times greater at the site of the ulcer were measured in the diabetic foot as compared with the healthy control. This preliminary investigation suggests that these methods are accurate for structural and pressure measurements of diabetic and healthy feet.

Adult↗

PubMedDate not supplied

A device for applying static loads to prosthetic limbs of transtibial amputees during spiral CT examination.

This paper describes a device that allows the imaging of prosthetic legs under load conditions using spiral computerized tomography (CT). The device consists of a chair and a vertical footplate mounted on a 17.8 x 1.9 cm oak board that is 197 cm long. The load device can be easily positioned onto the CT bed. A subject sits in the chair and applies force by pushing the foot portion of the prosthesis against the footplate. The magnitude of the force is monitored by a digital force gauge coupled to the footplate. Because the load is borne by the hips and lower back of the subject against the chair, substantial forces can be generated and steadily maintained for the 20-45 s duration of the CT study. This device has been used successfully with 19 transtibial amputees, allowing the acquisition of spiral CT studies with half and full body weight loads.

Amputation, Surgical↗