Comparison of predicted and measured contact pressures in normal and dysplastic hips

PURPOSE: To evaluate intravascular MR imaging in normal New Zealand rabbits and hereditary hyperlipidaemic Watanabe rabbits (WHHL) with histological correlation. MATERIAL AND METHODS: The suprarenal abdominal aortas of two normal and two WHHL rabbits were examined by conventional angiography, high resolution MRT with a surface coil and intravascular MRT in a 1.5 T system. The intravascular reception coil consisted of a copper wire loop built into the balloon of an angioplasty catheter. The findings were correlated with histological examinations. RESULTS: Excellent spin echo images with a resolution of 78 x 156 microns were obtained in less than 4 minutes. The arteriosclerotic changes in the vessels of the WHHL rabbits could not be recognised angiographically. High resolution MRT with surface coils showed mural thickening but a detailed demonstration of arteriosclerotic lesions was possible only by means of high resolution intravascular imaging. There was good histological correlation. CONCLUSION: Arteriosclerotic lesions can be demonstrated in vivo by high resolution intravascular imaging.     

Encapsulation of scleral buckling materials. A study of sixty specimens

OBJECTIVE: The purpose of the study was to obtain information on the encapsulation of two nonabsorbable biomaterials (silicone and hydrogel) used as explants in scleral buckling in retinal detachment surgery. DESIGN: The study design was a histopathologic study on a cohort of capsule fractions and complete eyes. PARTICIPANTS: Fifty-nine patients participated in this study, in which 60 specimens, including 37 hydrogel and 21 silicone capsule specimens as well as 2 whole eyes, were gathered. There were no control subjects. INTERVENTION: The capsule specimens were obtained from eyes operated on previously for scleral buckling for retinal detachment. The two whole eyes were enucleated. All specimens were studied with routine optic microscopy. MAIN OUTCOME MEASURES: Patient characteristics, type of scleral buckling, and number of operations performed were analyzed. Histologically, the capsular structure, its interface with the explant, and its different components also were studied. Remnants of the buckling material also were investigated. RESULTS: There were 45 male and 14 female patients, with a mean age of 49 years. Histologically, capsule specimens had a fibrous matrix with fibroblasts and few inflammatory cells. Eighteen (48.6%) of 37 hydrogel capsule specimens displayed hydrogel fragments surrounded by a foreign body giant cell granuloma in 16 cases. CONCLUSION: Nonabsorbable materials undergo encapsulation after implantation on the eye surface. Giant cell granuloma was observed in some hydrogel capsule specimens in relation to hydrogel fragmentation. The exact origin of this fragmentation remains unknown.     

High resolution MR imaging of joint degeneration in the knee of the STR/ORT mouse

MR imaging of the knee joints of the mouse at 2.35 T produces an in-plane resolution of 35 x 70 microns and a slice thickness of 600 microns from the sagittal and coronal planes, in less than 60 min. In normal, live DBA mice, which have no known pathology, the images clearly resolve many joint structures, such as the cruciate ligaments, menisci, and articulating surfaces of the femur and tibia. Gross pathological changes were identified first in excised knees from cadaver mice of the STR/ORT strain. Males of this strain spontaneously exhibit rapid joint degeneration with increasing age compared to females, in which much milder symptoms develop more slowly. Thickening of the patellar tendon, displacement of the patella, deformity, and sclerosis were clearly distinguishable in males compared with females older than 7 mo of age. The same degenerative features were evident in MR images of the knees of the live male but not female STR/ORT mice of this age, indicating that it would be possible to monitor longitudinally by MR imaging progressive development of joint changes in this osteoarthritic model.     

Magnetic resonance microscopy and histopathology: comparative approach of bromobenzene-induced hepatotoxicity in the rat

The development of magnetic resonance (MR) microscopy has provided new approaches to histology and histopathology. Recent work has shown the promise of increased sensitivity in animal models of chemically induced hepatotoxicity. However, the field is so new that there is little experience to relate changes seen in MR micrographs to the more traditional optical images stained with hematoxylin and eosin. This work compares the sensitivity and reproducibility of MR microscopy with conventional histopathology in detecting bromobenzene-induced hepatotoxicity in the rat. A time-course study was undertaken to provide a range of histopathologies. Specimens were studied at 24, 48, 72, and 96 hours after exposure to 10% of the median lethal dose of bromobenzene. Using 4 animals per group (a total of 32 rats) added statistical significance to the study and defined a range of interanimal variability over 96 hours. This work shows that MR microscopy, besides being nondestructive and three-dimensional, is at least as sensitive as conventional hematoxylin-eosin staining in detecting bromobenzene-induced centrilobular lesions and recovery of the hepatocellular architecture in the rat. This study further suggests that, as we begin to understand the underlying mechanisms of contrast in MR histology, MR may, in fact, supply even higher specificity than more traditional studies: variations were observed in MR images of treated livers at a given time point that could be not be differentiated based on the grading of necrosis and inflammation on hematoxylin-eosin-stained sections.     

Quantification of stromal thinning, epithelial thickness, and corneal haze after photorefractive keratectomy using in vivo confocal microscopy

PURPOSE: The authors establish, for the first time, observer-independent quantification of stromal thinning, epithelial thickness, and corneal haze after excimer laser photorefractive keratectomy (PRK) using a unique, new form of in vivo confocal microscopy. METHODS: Rapid, continuous z-scans of high-resolution confocal images, termed confocal microscopy through focusing (CMTF), were performed in the central corneal area of 17 patients before and 1 month after PRK for low- to moderate-grade myopia (-2.88-9.13 diopters [D]). Corneal, epithelial, and stromal thickness measurements and an objective haze estimate were obtained from each CMTF scan by digital image analysis. RESULTS: Epithelial thickness averaged 51 +/- 4 microns before and 45 +/- 10 microns 1 month post-PRK (P < 0.005), whereas stromal thinning ranged from 20 to 154 microns, representing a direct estimate of the actual photoablation depth. Corneal thickness averaged 560 +/- 36 microns before PRK and 462 +/- 52 microns at 1 month. The change in corneal thickness correlated closely with the change in spherical equivalent refraction (r = 0.94, P < 0.0001); linear regression analysis revealed a value of 14.3 microns corneal thinning per diopter of correction. A significant correlation was found between the objective CMTF haze estimate and a clinical haze grading obtained by slit-lamp examination (r = 0.73, P < 0.001). CONCLUSIONS: Confocal microscopy through focusing is a new, powerful in vivo tool that enables quantitative, unbiased evaluation of PRK procedures over time by providing epithelial and stromal thickness analysis, photoablation depth assessment, and unbiased haze measurement. The method is uniquely valuable in the pre- and postoperative assessment of PRK patients and for determining the optimal treatment strategy, especially in assessing refractive and visual outcomes in individual cases.     

Rupture of silicone gel filled testicular prosthesis: causes, diagnostic modalities and treatment of a rare event

PURPOSE: Rupture of the envelope of silicone gel filled testicular prostheses is rare and alleged to be unlikely without intraoperative needle puncture. We observed that it may be caused by chronic intermittent trauma or a single acute increase of pressure, and report diagnostic and therapeutic modalities. MATERIALS AND METHODS: Four cases treated by us during the last 10 years are presented. One patient had testicular implants for Klinefelter's syndrome, whereas the other 3 had been treated for female-to-male transsexualism. Diagnosis was confirmed by ultrasonography and magnetic resonance imaging. The fibrous capsule surrounding the ruptured prosthesis was left intact to allow en bloc surgical extirpation. Histological evaluation of the resected specimen was performed. RESULTS: Rupture of silicone gel filled testicular implants may be caused by acute or chronic pressure without intraoperative needle puncture. CONCLUSIONS: Magnetic resonance imaging offers superior diagnostic accuracy and should be regarded the gold standard in the evaluation of implant rupture. Ultrasonography is an acceptable alternative. In cases when gross symptoms of scrotal inflammation are lacking replacement of implants is facilitated by the fibrous capsule that forms around any prosthesis. Transcapsular migration of silicone particles was observed even when the fibrous capsule was intact.     

Magnetic resonance imaging of the normal mouse brain: comparison with histologic sections

Details in the living animal can be compared with respective histologic section taken after death. In less than 35 min, 12 to 16 coronal and transverse images through the brain can be obtained, each with an in-plane resolution of 100 x 200 microns and a slice thickness of 900 microns. The experimental parameters can be manipulated not only to achieve different tissue contrast but also to access any desired plane.     

Optimization of thin-foil based phosphor screens for CCD imaging in TEM in the voltage range of 80-400 kV

The voltage dependence characteristics of thin-foil based phosphor screens in the thickness range of approximately 10-60 microns are examined for CCD imaging in transmission electron microscopy (TEM) in the voltage range of 80-400 kV. The brightest screen is obtained with a P20 layer of about 12 microns at 80 kV, and a thicker screen lowers both the screen brightness and resolution. The thickness of the brightest screen is higher at higher voltage, but other considerations for a practical CCD imaging system suggest that the P20 layer should not be greater than approximately 18 microns for the voltage range stated above.     

Tissue response to suture materials implanted subcutaneously in a rabbit model

We compared the tissue response to a nonabsorbable monofilamented suture made of expanded polytetrafluoroethylene (ePTFE), which has recently been introduced for use in plastic surgery, with the response to 10 other commercially available absorbable sutures and nonabsorbable monofilamented and multifilamented sutures. The sutures were used to secure a patch of ePTFE implanted in the dorsum of adult New Zealand White rabbits. At 30, 60, and 120 days after implantation, the tissue response to the sutures was assessed with respect to the number of foreign-body giant cells present, the thickness of the fibrous capsule that developed, and the general inflammatory response (n = 4 for each suture for each time period). Analysis of variance revealed that specific suture type was significantly associated with foreign-body giant cell count and fibrous capsule thickness. Tevdek had a significantly higher value for mean number of foreign-body giant cells. Silk and Tevdek had significantly thicker fibrous capsules, and ePTFE suture had a significantly thinner capsule. Absorbable sutures and nonabsorbable multifilamented sutures evoked a more extensive tissue response than monofilamented sutures; the differences between nonabsorbable monofilamented and nonabsorbable multifilamented sutures were significant for capsule thickness. In general, suture made of ePTFE produced a minimal tissue response. It should be a good choice for use in facial plastic surgery, in which excellent functional and aesthetic results are critical.     

Confocal microscopic characterization of wound repair after photorefractive keratectomy

PURPOSE: Development of postoperative corneal haze and regression of refractive effect are unfavorable clinical complications of excimer laser photorefractive keratectomy (PRK). Although exact mechanisms remain to be elucidated, these outcomes have been attributed to post-PRK corneal wound healing. The purpose of this study was to evaluate corneal wound repair quantitatively after PRK in a rabbit model using a newly developed in vivo technique, termed confocal microscopy through focusing (CMTF). METHODS: Twelve rabbit corneas received a monocular, 6-mm diameter, 9.0-diopter PRK myopic correction. Animals were evaluated sequentially up to 6 months after surgery by in vivo CMTF, which uses an image-intensity depth profile to measure epithelial and stromal thickness and uses corneal light reflectivity as an objective estimate of corneal haze. At differing temporal intervals, in vivo morphology was correlated with ex vivo histology using fluorescence microscopy. RESULTS: One week after PRK, an acellular layer of 86 +/- 24 microns was found anteriorly in the remaining stroma, which demonstrated surgically induced keratocyte death. Underlying keratocytes became activated and migrated toward the wound bed; repopulation was completed within 3 weeks. One week after PRK, there was a significant increase (P < 0.001) in light reflections detected from the photoablated stromal surface (1745 +/- 262 U) and from the underlying activated fibroblasts (713 +/- 607 U). Corneal reflectivity peaked at 3 weeks (4648 +/- 1263 U) and decreased linearly to 889 +/- 700 U by 6 months after the PRK; this corresponded to a reflectivity six times greater than the level seen in unoperated corneas. Two weeks after PRK, initial corneal edema had resolved, revealing an actual ablation depth (maximal stromal thinning) of 118 +/- 8 microns. Starting at 2 weeks after surgery, the stroma underwent gradual rethickening that reached 98% of the preoperative thickness at 6 months after PRK; at that time, only 6% of the initial photoablation depth persisted. By contrast, the central corneal epithelium showed no significant postoperative hyperplasia. CONCLUSIONS: Rabbit corneas treated by PRK showed a remarkable stromal wound-healing response that ultimately led to the restoration of the original stromal thickness by 6 months after surgery, demonstrating complete regression of the initial photoablative effect. Additionally, corneal wound healing was associated with increased light reflections from both the photoablated stromal surface and the activated wound-healing keratocytes underlying this area. Based on these findings, the authors hypothesize that the development of clinically observed corneal haze in PRK patients may be related, in part, to activation of corneal keratocytes and to putative changes in the extracellular matrix.     

Magnetic resonance imaging of the musculoskeletal system. II. The hip

Magnetic resonance (MR) imaging of the hip joint and adjacent structures can provide valuable information under many clinical circumstances. After plain radiography, MR imaging is arguably the modality of choice for the detection of osteonecrosis, occult fractures, primary and secondary neoplasms, and in the assessment of some soft tissue abnormalities. The accuracy of MR imaging is dependent on technical factors, such as magnet field strength, surface coils, and sequence selection. Low resolution MR images generally are satisfactory for screening for osteonecrosis and for the evaluation of large bone or soft tissue abnormalities. Tailoring an examination with high resolution images, specialized sequences, or contrast may add useful information, particularly if a detailed evaluation of the joint is desired. Tailoring of the examination by an experienced radiologist requires adequate clinical information, so communication between the referring physician and radiologist is crucial for optimal results. Finally, MR imaging and radiographs are complementary examinations; MR images of the hip should not be interpreted without having recent radiographs available for comparison.     

Macroscopic and microscopic study of local compatibility of silicone rubber in short- and long-term experiments

Extended trials were carried out on the purpose of finding optimal silicone rubber materials for endotheses, among others macroscopical and microscopical examinations of local compatibility after implantation in rats and dogs. Short-term experiments on 7 kinds of silicone rubber (VEB Chemiewerk Nünchritz) showed that subcutaneous and intramuscular implantation was well tolerated by rats. Optimal terms for removal were the 7th and the 28th day. Long-term trials of 4 kinds of silicone rubber in rats and dogs up to 1 year yielded no significantly different results compared with control materials from the Dow Corning Corporation. After comparing trials for biostability, 2 silicone rubbers were recommended for clinical use. Optimal terms for removing in long-term experiments were the 3rd, 6th, and 12th month. In the rat experiments after 6 months the thickness of the capsule remained constant, as morphometrically determined. This might be crucial in the assessment of long-term compatibility.     

Health care in the new Russia: a western perspective

OBJECTIVE: To evaluate the growth and insulin secretion from microencapsulated beta TC6-F7 cells in vitro and to assess the in vivo function of microencapsulated cells transplanted in rats with steptozotocin (STZ)-induced diabetes. METHOD: Alginate-poly-L-lysine encapsulated beta TC6-F7 cells were exposed to glucose, isobutylmethylxanthine (IBMX) and glucagon-like peptide I (7-36 amide) in a static in vitro challenge. In vivo, 2.5-3.5 x 10(7) encapsulated cells were implanted into diabetic rats. Graft function was evaluated by monitoring blood glucose concentrations and by an intraperitoneal glucose tolerance test. RESULTS: The cell density (number of cells per capsule) of cultured microencapsulated beta TC6-F7 cells increased almost 35-fold over a 55 day observation period to reach a plateau of approximately 3500 cells/capsule. While insulin secretion per capsule remained unchanged over the first 21 days of culture, a 7-fold increase was observed during the last 14 days of the 55 day observation period. Intraperitoneal transplantation of 3.5 x 10(7) encapsulated cells into diabetic rats resulted, within 24 hours, in reversal of hyperglycemia for up to 60 days. Post-transplantation blood glucose concentrations varied between 2 and 4 mM. Glucose clearance rates evaluated by an intraperitoneal glucose tolerance test at 30 days post-transplantation resulted in a markedly flat glucose clearance curve with blood glucose never rising above 4 mM. The glucose challenge of microencapsulated cells recovered 30 days post-transplantation resulted in a 2-fold increase in insulin response at glucose concentrations greater than 5.5 mM as compared to glucose-free media. In addition, immunostaining of recovered grafted tissue for insulin, reveals a strong presence of the peptide within the cell population. CONCLUSIONS: These data demonstrate the potential use of an immunoisolated beta-cell line for the treatment of diabetes.     

The influence of time on human breast capsule histology: smooth and textured silicone-surfaced implants

Although the histology of capsular tissue is well described in the literature, most studies in humans do not correlate histologic findings with implant age (number of years an implant was in place before sampling). As such, questions regarding the long-term histology in humans remain. The microanatomy of 93 human periprosthetic capsular tissues surrounding 22 textured and 71 smooth silicone-surfaced prostheses was studied. The implants were divided into two groups according to the time between implantation and capsulectomy: between 0 and 5 years or more than 5 years. Hematoxylin and eosin and Masson trichrome-stained sections were analyzed by light microscopy, with and without polarization. Eighteen of the textured implants contained silicone gel and four contained saline. Sixty of the smooth implants contained silicone gel, eight contained saline, and in three, the filler type was not known. For the majority of patients, surgery was performed for augmentation mammaplasty, and the implants were removed because of capsular contracture. The following histologic features were assessed: synovial-like metaplasia, villous hyperplasia, density of the collagenous capsule, alignment of collagen fibers within the capsule, and the presence of foreign material and of a foreign body reaction. The following trends were observed. In smooth implants, increasing implant duration was associated with a decrease in the presence of synovial-like metaplasia (p = 0.003) and villous hyperplasia; there was no significant difference in the presence of a dense collagenous capsule, the orientation of collagen fibers, or the presence of a foreign body reaction. An increase was observed in the presence of foreign material (p = 0.01). In textured implants, increasing implant duration was associated with a decrease in the presence of synovial-like metaplasia, villous hyperplasia (p = 0.003), dense collagenous architecture, and parallel orientation of collagen fibers (p = 0.017). An increase in the presence of a foreign body type reaction and foreign material (p = 0.024) was observed. In comparing textured and smooth-surfaced implants, synovial-like metaplasia was observed more often in the textured group, both at 0 to 5 years (p = 0.01) and at greater than 5 years (p < 0.01). Textured implants more often had villous hyperplasia at 0 to 5 years (p = 0.03) but not beyond 5 years. Smooth implants more often had a dense collagenous capsule than textured implants after 5 years. No significant difference was seen in the orientation of collagen fibers in capsules around smooth and textured implants at 0 to 5 years. After 5 years, the incidence of capsules with collagen fibers arranged parallel to the implant surface was significantly greater in the smooth group than in the textured group (p = 0.01). The presence of a foreign body type reaction was seen more often in the textured group between 0 and 5 years (p = 0.01) and at greater than 5 years (p < 0.01), and the presence of foreign material was more often seen in the textured group between 0 and 5 years (p = 0.06) and at greater than 5 years (p < 0.01). In summary, the cytologic changes around implants seem to be dynamic in nature, and implantation duration and shell type play a significant role. Synovial-like metaplasia, villous hyperplasia, and foreign material were more often observed in the textured group within the 0 to 5 year interval. Beyond 5 years, synovial-like metaplasia, a foreign body type reaction, and foreign material were more often observed in the textured group. Differences in the density of collagenous capsules were not significant at any time point, and collagen fibers oriented parallel to the implant surface were more often observed in the smooth group after 5 years. The significance of these findings awaits further investigation.     

Microgrooved subcutaneous implants in the goat

We investigated the behavior of microgrooved implants in soft tissue using polystyrene implantable disks, either smooth or microgrooved (1-10 microm) on both sides. The implants were placed subcutaneously in a goat for 1, 4, or 12 weeks. Light and transmission electron microscopy showed that fibrous capsule formation around the implants was fairly uniform. After 1 week the implants were covered with a fibrous capsule about 80 microm thick. The collagen matrix was loose, and many inflammatory cells were present. After 4 weeks the matrix was more dense and contained many newly formed blood vessels. At the implant surface a layer of inflammatory cells about 10 microm thick had accumulated. Finally, after 12 weeks the matrix had densified. One cellular layer of inflammatory cells was present at the implant surface. We carried out histomorphometric measurements of capsule thickness, inflammatory layer thickness, and the number of blood vessels. Capsule thickness appeared not to decrease with time. Further, these measurements showed that there were no differences in tissue reaction between smooth and microgrooved implants. On the basis of our observations, we suggest that 1 microm deep and 1-10 microm wide microgrooves do not influence tissue response around polystyrene implants in soft tissue.     

Cellular responses to silicone and polyurethane prosthetic surfaces

Prosthetic devices composed of silicone or polyurethane are commonly used in surgery. These devices elicit a soft tissue reaction which may frequently be complicated by capsule formation. Histologically the capsule comprises both cellular (fibroblasts and endothelial cells (EC)) and matrix components (predominantly collagen type I). We hypothesized that the function of the cellular elements is altered by exposure to prosthetic materials and that this alteration contributes to capsule formation. To test this hypothesis, we utilized specific in vitro assays of cell function (attachment, proliferation, matrix gel contraction), which closely mimic in vivo cellular events, in order to define the responses of EC and fibroblasts to prosthetic surfaces (foam polyurethane, flat silicone, and textured silicone). Morphologic changes were evaluated by scanning electron microscopy (SEM). Attachment of both cell types to all prosthetic surfaces was significantly decreased compared to control (HUVEC: control, 55 +/- 1; foam polyurethane, 19 +/- 4*; flat silicone, 25 +/- 3*; textured silicone, 36 +/- 1*; fibroblast: control, 93 +/- 6; foam polyurethane, 21 +/- 4*; flat silicone, 57 +/- 5*; textured silicone, 44 +/- 5* (*P < 0.05 = significant; units, percentage spread)). Fibroblast proliferation was significantly decreased on foam polyurethane (0.1 +/- 0.03*) and textured silicone (0.18 +/- 0.05*), but not on flat silicone (0.79 +/- 0.2; control = 0.96 +/- .2). In contrast, HUVEC proliferation was significantly decreased on both silicone surfaces but not on polyurethane (units, cpm/cell; control, 0.26 +/- 0.05; foam polyurethane, 0.15 +/- 0.05; flat silicone, 0.08 +/- 0.03*; textured silicone, 0.02 +/- 0.01*).(ABSTRACT TRUNCATED AT 250 WORDS)     

Placental pathology in systemic lupus erythematosus: a prospective study

An intravenous (iv) radiofrequency (RF) coil is proposed as a means of obtaining high resolution images of artery wall. The anatomic positioning of peripheral artery/vein pairs was investigated and a phantom mimicking the iliac artery/vein pair was constructed. Imaging results, comparing iv coils with external coils, demonstrated a potential 15- to 20-fold increase in signal-to-noise ratio (SNR) with iv coils. The SNR benefit was measured over a cylindrical volume, adjacent to the coil, and typical of artery position. Prototype expandable iv coils were constructed of Cu-Be loops and introduced via an 8-Fr catheter. The effects of local and remote iv coil tuning were investigated and local tuning was found to provide significant SNR benefits. The in vivo performance of iv RF coils was demonstrated in a porcine animal model. The iv coils were found to be an excellent alternative to intraarterial coils.     

Migration and biodegradation of free silicone from silicone gel-filled implants after long-term implantation

In vivo 1H NMR chemical shift imaging (CSI), 1H NMR localized spectroscopy (STEAM) and multinuclear NMR spectroscopy (29Si, 13C, 1H) were used to characterize the aging process of silicone gel-filled implants in a rat model after long-term implantation. Although no significant changes could be observed in the implants or surrounding tissue by in vivo 1H chemical shift imaging, in vivo 1H localized spectroscopy of the livers from the longer term population revealed the presence of silicone. Ex vivo 29Si spectroscopy of the liver, spleen, and the capsule formed around the 9 and 12 month implants clearly demonstrated and confirmed for the first time that a significant amount of free silicone migrates from silicone gel-filled implants. Also, these results show that silicones are not metabolically inert, and their biodegradation in tissue and within the implant can be monitored after 9 and 12 months by changes in the 29Si chemical shifts seen in corresponding ex vivo spectra. The NMR findings are supported by those obtained by atomic absorption spectroscopy. Silicone aging changes not only the chemical composition of the gel, but also its proton T2 relaxation times, which increase with long implantation times. The three dimensional structure of the gel disintegrates (i.e., polymer chain rupture), increasing the molecular mobility of the polymer and, consequently, its protons T2 values. The relaxation data we obtained reflect this in vivo degradation, especially in the case of implant rupture. Additionally, small concentrations of fat in the silicone gel were found within the implants. The presence of these lipophilic substances also might increase the T2 values (plasticizer effect). These findings may assist in evaluating the implant integrity and disease symptoms related to their presence in humans.     

A small angle light scattering device for planar connective tissue microstructural analysis

The planar fibrous connective tissues of the body are composed of a dense extracellular network of collagen and elastin fibers embedded in a ground matrix, and thus can be thought of as biocomposites. Thus, the quantification of fiber architecture is an important step in developing an understanding of the mechanics of planar tissues in health and disease. We have used small angle light scattering (SALS) to map the gross fiber orientation of several soft membrane connective tissues. However, the device and analysis methods used in these studies required extensive manual intervention and were unsuitable for large-scale fiber architectural mapping studies. We have developed an improved SALS device that allows for rapid data acquisition, automated high spatial resolution specimen positioning, and new analysis methods suitable for large-scale mapping studies. Extensive validation experiments revealed that the SALS device can accurately measure fiber orientation for up to a tissue thickness of at least 500 microns to an angular resolution of approximately 1 degree and a spatial resolution of +/-254 microns. To demonstrate the new device's capabilities, structural measurements from porcine aortic valve leaflets are presented. Results indicate that the new SALS device provides an accurate method for rapid quantification of the gross fiber structure of planar connective tissues.     

Measurement of localized cartilage volume and thickness of human knee joints by computer analysis of three-dimensional magnetic resonance images

RATIONALE AND OBJECTIVES: This work demonstrates a new method for computerized measurement of the dimensions (thickness and volume) of articular cartilage for any specified region of the human knee joint. Three-dimensional magnetic resonance (MR) images optimized for cartilage contrast have been analyzed using computerized edge-detection techniques, and the reproducibility of articular cartilage thickness and volume measurements is assessed. METHODS: A fat-suppressed, three-dimensional SPoiled GRass MR sequence (45/7.5/30 degrees) with total scan time of approximately 12 minutes was used to acquire volume images of human knee joints at spatial resolution of 0.6 x 1.2 x 1.2 mm. Measurements were made using six repeated scans for three healthy volunteers over a period of 2 months. The subsequent semi-automated image processing to establish total cartilage volume and cartilage thickness maps for the femur required approximately 60 minutes of operator time. RESULTS: The mean coefficient of variation for total cartilage volume for the six repeated scans for the three volunteers was 3.8%, and the average coefficient of variation for the user-selected cartilage plugs was 2.0%. The cartilage thickness maps from the repeated scans of the same knee were similar. CONCLUSIONS: Standard resolution MR images with fat-suppressed contrast lead to an objective and reproducible measurement of spatial dimensions of articular cartilage when analyzed semi-automatically using computerized edge-detection methods.