Tissue Dimensions Research Articles

Histological analysis of loaded zirconia and titanium dental implants: an experimental study in the dog mandible.

To assess whether or not peri-implant soft tissue dimensions and hard tissue integration of loaded zirconia implants are similar to those of a titanium implant. In six dogs, two one-piece zirconia implants (VC, ZD), a two-piece zirconia implant (BPI) and a control one-piece titanium implant (STM) were randomly placed. CAD/CAM crowns were cemented at 6months. Six months later, animals were killed and histomorphometric analyses were performed, including: the level of the mucosal margin, the extent of the peri-implant mucosa, the marginal bone loss and the bone-to-implant contact (BIC). Means of outcomes variables were calculated together with their corresponding 95% confidence intervals. In general, the mucosal margin was located coronally to the implant shoulder. The buccal peri-implant mucosa ranged between 2.64±0.70mm (VC) and 3.03±1.71mm (ZD) (for all median comparisons p>0.05). The relative marginal bone loss ranged between 0.65±0.61mm (BPI) and 1.73±1.68mm (ZD) (buccal side), and between 0.55±0.37mm (VC) and 1.69±1.56mm (ZD) (lingual side) (p>0.05). The mean BIC ranged between 78.6%±17.3% (ZD) and 87.9%±13.6% (STM) without statistically significant differences between the groups (p>0.05). One- and two-piece zirconia rendered similar peri-implant soft tissue dimensions and osseointegration compared to titanium implants that were placed at 6months of loading. Zirconia implants, however, exhibited a relatively high fracture rate.

Sequential Healing at Implants with Different Configuration and Modified Surfaces: An Experimental Study in the Dog.

To evaluate the peri-implant soft and hard tissue adaptation at implants with different modified surfaces and configurations. Six Beagle dogs were used. Mandibular premolars and first molars were extracted bilaterally. After 3 months, full-thickness flaps were elevated, and two different types of trans-mucosal implants (ICX-Gold®, Medentis Medical GmbH, Dernau, Germany and SLActive®, Institute Straumann, Bern, Switzerland) and two different surfaces were randomly installed in the distal regions of one side of the mandible. Abutments were applied, and a nonsubmerged healing was allowed. After 1 month, the procedures were performed in the other side of the mandible, and after a further month, the animals were sacrificed, biopsies were collected, and ground sections prepared for histological examination. Similar results in marginal bone and soft tissues dimensions were observed after 1 month of healing at the two implant systems used, and no major changes could be observed after 2 months of healing. After 1 month, the percentage of new bone was 69.0% and 68.8% at ICX-Gold and SLActive surfaces, respectively. After 2 months, the percentage of new bone was 67.8% and 71.9% at ICX-Gold Medentis and SLActive surfaces, respectively. No statistically significant differences in osseointegration were found. The two implant systems used resulted in similar osseointegration after 1 and 2 months of healing.

An "All-laser" Endothelial Transplant.

The "all laser" assisted endothelial keratoplasty is a procedure that is performed with a femtosecond laser used to cut the donor tissue at an intended depth, and a near infrared diode laser to weld the corneal tissue. The proposed technique enables to reach the three main goals in endothelial keratoplasty: a precise control in the thickness of the donor tissue; its easy insertion in the recipient bed and a reduced risk of donor lenticule dislocation. The donor cornea thickness is measured in the surgery room with optical coherence tomography (OCT), in order to correctly design the donor tissue dimensions. A femtosecond laser is used to cut the donor cornea. The recipient eye is prepared by manual stripping of the descemetic membrane. The donor endothelium is inserted into a Busin-injector, the peripheral inner side is stained with a proper chromophore (a water solution of Indocyanine Green) and then it is pulled in the anterior chamber. The transplanted tissue is placed in the final and correct location and then diode laser welding is induced from outside the eyeball. The procedure has been performed on more than 15 patients evidencing an improvement in surgery performances, with a good recovery of visual acuity and a reduced donor lenticule dislocation event.

Soft Tissue Alterations in Esthetic Postextraction Sites

Dimensional alterations of the facial soft and bone tissues following tooth extraction in the esthetic zone play an essential role to achieve successful outcomes in implant therapy. This prospective study is the first to investigate the interplay between the soft tissue dimensions and the underlying bone anatomy during an 8-wk healing period. The analysis is based on sequential 3-dimensional digital surface model superimpositions of the soft and bone tissues using digital impressions and cone beam computed tomography during an 8-wk healing period. Soft tissue thickness in thin and thick bone phenotypes at extraction was similar, averaging 0.7 mm and 0.8 mm, respectively. Interestingly, thin bone phenotypes revealed a 7-fold increase in soft tissue thickness after an 8-wk healing period, whereas in thick bone phenotypes, the soft tissue dimensions remained unchanged. The observed spontaneous soft tissue thickening in thin bone phenotypes resulted in a vertical soft tissue loss of only 1.6 mm, which concealed the underlying vertical bone resorption of 7.5 mm. Because of spontaneous soft tissue thickening, no significant differences were detected in the total tissue loss between thin and thick bone phenotypes at 2, 4, 6, and 8 wk. More than 51% of these dimensional alterations occurred within 2 wk of healing. Even though the observed spontaneous soft tissue thickening in thin bone phenotypes following tooth extraction conceals the pronounced underlying bone resorption pattern by masking the true bone deficiency, spontaneous soft tissue thickening offers advantages for subsequent bone regeneration and implant therapies in sites with high esthetic demand (Clinicaltrials.gov NCT02403700).

Effect of glucose on the biomechanical function of arterial elastin

Elastin is essential to provide elastic support for blood vessels. As a remarkably long-lived protein, elastin can suffer from cumulative effects of exposure to biochemical damages, which can greatly compromise its biomechanical properties. Non-enzymatic glycation is one of the main mechanisms of aging and its effect is magnified in diabetic patients. The purpose of this study is to investigate the effects of glucose on mechanical properties of isolated porcine aortic elastin. Elastin samples were incubated in 2M glucose solution and were allowed to equilibrate for 4, 7, 14, 21 or 28 days at 37°C. Equibiaxial tensile tests were performed to study the changes of elastic properties of elastin due to glycation. Significant decreases in tissue dimension were observed after 7 days glucose incubation. Elastin samples treated for 14, 21 or 28 days demonstrate a significant increase in hysteresis in the stress–stretch curves, indicating a greater energy loss due to glucose treatment. Both the longitudinal and the circumferential directions show significant increases in tangent modulus with glucose treatment, however only significant increases are observed after 7 days for the circumferential direction. An eight-chain statistical mechanics based microstructural model was used to study the hyperelastic and orthotropic behavior of the glucose-treated elastin and the material parameters were estimated using a nonlinear least squares method. Material parameters in the model were related to elastin density and fiber orientation, and, hence, the possible microstructural changes in glucose-treated elastin. Estimated material parameters show a general increasing trend in elastin density per unit volume with glucose incubation. The simulation results also indicate that more elastic fibers are aligned in the longitudinal and circumferential directions, rather than in the radial direction.

Is the Preoperative MRI Appearance of Lumbar Multifidus Prognostic for Outcomes of Lumbar Decompression?

Introduction Decompressive surgery for symptomatic lumbar spinal stenosis is associated with good outcomes provided that appropriate patient selection is undertaken, which has proven critical (Aalto et al 2006). It has previously been proposed that the MRI appearance of multifidus is correlated to leg and back pain symptoms (Ali et al 2011 and Kader et al 2000). Therefore, our aim was to assess whether the preoperative MRI appearance of multifidus was predictive of outcomes for lumbar spinal stenosis surgery and could be used in patient selection. Our hypothesis was that patients with fatty atrophy on MRI would have significantly poorer clinical outcomes than those without. Patients and Methods A review of patients who had undergone lumbar spinal stenosis surgery in the previous 2 years (minimum 1-year follow-up) and had completed spine tango outcomes was undertaken. Exclusion criteria were additional procedures, for example, fusion and patients without MRI scans. Individual patient comorbidities and complication profiles were also assessed. The multifidus caliber was measured for each patient on MRI using a DICOM viewer by two assessors blinded to the outcome scores. In addition to the Kader et al (2000) classification, elliptical cross-sectional area mapping of multifidus was taken as an average measurement at the axial L4/5 level. Also, measured were the posterior adipose tissue layer and dimensions of the L5 vertebral body, areas of critical stenosis and psoas muscles, respectively. Results A total of 66 patients (41 females and 25 males) met the inclusion criteria and underwent analysis. There was a significant improvement for the cohort in ODI and COMI scores following surgical intervention and 89% of patients had improvement in ODI and COMI scores. The mean age was 67 years (range, 29–86 years). Overall, 44 patients had single level decompressions while for 2 level and 3 level decompressions; there were 16 and 6 patients, respectively. Overall, 44 (84%) of single levels involved either L4/5 or L5/S1 (37/44) with L3/4 and L2/3 involved in five and two patients, respectively. Moderate or severe fatty degenerative changes (Kader grades II or III) were noted in 71% of patients while a mean CSA (cm2) of 8.4 cm2 or less for multifidus at the measured level was noted in 71% of patients. The proportions of the cohort who improved more than 40% in their COMI and ODI when comparing the cohorts of patients with CSA < 8.5 cm2 compared with ≥ 8.5 cm2 were significantly different (47 vs. 79% [ p = 0.02] and 32 vs. 68% [ p = 0.006]). For patients with a Kader grade of 0 to 2 and CSA ≥ 8.5 cm2, there was significantly more percentage improvement with ODI/COMI (mean 84, 75) compared with Kader 2 to 3 and CSA < 8.5 cm2 (mean 28, 23) ( p = 0.05). Conclusion The appearance of lumbar multifidus on preoperative MRI is predictive of outcomes of lumbar spinal stenosis surgery with better results at a minimum of 1 year in patients with less fatty degenerative changes and higher cross-sectional area. This has implications for use in the perioperative setting and further research on the value of preoperative imaging for other spinal surgery is indicated.

Treatment of severe mucogingival defects with a combination of strip gingival grafts and a xenogeneic collagen matrix: a prospective case series study.

Large areas of mucogingival alterations may result from advanced regenerative procedures. This prospective case series study was performed to introduce and evaluate a surgical approach that combines the strip gingival graft technique with the use of a xenogeneic collagen matrix. The primary outcome measurement was the increase in keratinized tissue width from baseline to 12 months postprocedure. Twenty patients were enrolled, and they all completed the 12-month evaluation. All treated sites exhibited a significant gain in keratinized tissue at 12 months, with a mean width of 6.33 mm (SD: 2.16), while there was a 43% contraction of the grafted area at 6 months. Tissue dimensions remained stable between 6 and 12 months. The use of the combination graft was well accepted by the patients, with minimal morbidity according to the patients' low self-reported pain and the low utilization of pain medication.

Three-Dimensional Evaluation of Alveolar Bone and Soft Tissue Dimensions of Maxillary Central Incisors for Immediate Implant Placement: A Cone-Beam Computed Tomography Assisted Analysis.

This study explored the relationship between the thickness of bone and soft tissue along the labial and palatal aspect of maxillary central incisors. The influence of overall socket width, labiopalatal positioning of the incisor on the bone, and soft tissue thickness were also investigated. This study used cone-beam computed tomography of 150 patients to determine labial, palatal soft and hard tissue thickness, labiopalatal (B-P) socket width and corelated the same to the labiopalatal positioning of maxillary central incisors. Mean (SD) thicknesses of the labial soft tissue at cervical (C), midroot (M), and apical (A) locations and the corresponding bone thicknesses were 1.07 (0.28), 0.987 (0.27), 1.240 (0.41), and 0.928 (0.39), 0.894 (0.52), 1.57 (0.88), respectively. Similarly, palatal soft tissue and bone thicknesses at locations C, M, A were 1.807 (0.66), 1.557 (0.62), 1.639 (0.66), and 1.679 (0.62), 3.439 (1.28), 6.038 (1.63), respectively. Mean (SD) thicknesses of the B-P socket width at location C was 8.047 (0.963). There is a positive correlation between the labial and palatal bone and corresponding soft tissue thickness, between thickness of the labial bone and the labiopalatal thickness of the alveolar socket. No correlation was observed between the thickness of the labial cortical bone and the labiopalatal positioning of the tooth.

Assessment of the soft tissue volumetric changes following acellular dermal matrix grafts with cone beam computerized tomography.

The aim of this study was to use cone beam computerized tomography (CBCT), which consistently allowed the determination of the dimensions of the soft tissue, to evaluate acellular dermal matrix grafts (ADMG) used to increase gingival soft tissue thickness (GSTT). In total, 90 gingival defects were included in the study. Surgical procedures were performed to augment the gingival tissue with ADMG. While GSTT measurements were assessed at baseline and 6, 12, and 18 months post-surgery, ADMG measurements were performed with CBCT at 6, 12, and 18 months post-surgery. All parameters showed statistically significant differences between time intervals. In the ADMG-treated sites, the baseline GSTT was 1.00 ± 0.37 mm and the final thickness was 1.66 ± 0.34 mm. The 6-month measurement of ADMG was 0.79 ± 0.08 mm, and the final measurement was 0.11 ± 0.09 mm. High-quality images of the GSTT and ADMG can be consistently obtained with CBCT. The present findings indicate that soft tissue augmentation can be achieved in gingival defects with the use of ADMG.

Influence of the target tissue size on the shape of ex vivo microwave ablation zones

Purpose: The aim of this study was to numerically and experimentally characterise the influence of tissues dimensions on the size and shape of microwave-induced ablation zones. Materials and methods: A 2.45 GHz interstitial antenna was introduced into ex vivo bovine liver samples, delivering 60 W for 10 min; then the dimensions of the coagulated area were measured. Ablations were performed both in large samples (termed unrestricted tissue) for characterising the tissue response, and in thin samples, whose dimensions in the plane perpendicular to the antenna were smaller than the short axis of the ablated area obtained in unrestricted samples. In the numerical study the electromagnetic field emitted from the antenna and the corresponding temperature increase were evaluated in both unrestricted and thin tissue samples. Results: When the height of the tissue was smaller than the ablation diameter measured in unrestricted samples, a 7.5% increase in length of the ablated zone was experimentally observed. When both the height and width were lower than the diameter measured in unrestricted samples, an elongation of about 23.4% was experimentally obtained. The numerical study showed that the boundary conditions between the target tissue and the surrounding materials are critical. Conclusions: The ex vivo performances of microwave ablation devices are notably influenced by the shape and dimension of the tissues where the procedure takes place. Accordingly, dedicated interventional protocols should be developed for treatment planning on targets of different shape and size.

Differences in dentofacial characteristics of Class I malocclusion between Saudi and Japanese adult females.

Objectives:The objective was to compare dentofacial characteristics of Class I malocclusion in Saudi and Japanese adult females.Materials and Methods:Lateral cephalograms of 50 Saudi adult female and 50 Japanese adult female (18–35-year-old) were obtained. All patients were skeletal Class I, angle Class I malocclusion, arch length discrepancy (−10–10 mm), overjet (1–5 mm), overbite (1–5 mm), absence of congenital anomalies, or significant facial asymmetries or congenitally missing tooth other than the 3rd molar and absence of temporomandibular joint problems. Patient cephalograms were traced and digitized. 16 angular measurements and 13 linear measurements of facial form were used.Results:A comparison of the vertical dimension showed that the Saudi females had a significantly larger gonial angle, a significantly larger facial angle and longer lower face height compared to the Japanese females. Dentally, Saudi females had more protruded incisors with increased distances of the posterior teeth to the palatal plane. For the soft tissue dimension, the Saudi subjects had a significantly more prominent nose, retruded lip and a more protruded chin compared with Japanese.Conclusions:There were significant differences in dentofacial morphology between Saudi and Japanese adult females. Both Asian countries have distinct cephalometric features, which should be considered as a reference in treating patients of varying ethnic backgrounds to optimize the final results.

Ridge preservation using a new 3D collagen matrix: a preclinical study.

The success of ridge preservation techniques in reducing bone resorption is well documented, but no clear guidelines have been provided regarding the type of the biomaterial or technique to be used. This experimental animal study aimed at comparing the effectiveness of two ridge preservation techniques. Following the extraction of the distal roots of the mandibular second and fourth premolars of four dogs, the sockets were preserved using a combination of a collagen membrane intimately covering the socket plus a collagen matrix or a collagen membrane alone. The mandibular quadrants were randomly assigned to one of the treatment groups. Histomorphometrical analyses as well as microscopic observations were performed. After 5months of healing, the histological analysis revealed a similar picture of bone formation in both groups. No significant differences between the buccal and lingual dimensions were calculated between the two treatment groups. The mucosa covering the alveolar ridges is significantly more abundant in post-extraction sockets preserved with the double-layered approach. The double-layered approach used to treat post-extraction sockets may result in a better preservation of the mucosal seal than the single-layered approach. The use of the new collagen matrix associated with a collagen membrane could be a clinical option to preserve post-extraction ridges, especially when an improvement in soft tissue dimension and quality is desired. However, the cost-benefit ratio of this approach should be thoroughly evaluated in further studies.

Intermediate long-term clinical performance of dental implants placed in sites with a previous early implant failure: a retrospective analysis.

The aim of this retrospective case-control study was to evaluate the intermediate long-term clinical performance and success rate of dental implants inserted into sites of previous early implant failure. A retrospective evaluation was conducted on 6456 patients with 10,234 implants from January 2004 to December 2011. The patients with early implant failure retreated in previous failed sites were enrolled in the study. The collected data included patient's characteristics, implants characteristics (failed and replaced), and if was the case, any additional surgery performed prior or at the same of implant placement to obtain proper hard tissues dimensions. Moreover, peri-implant clinical parameters, marginal bone loss (MBL), and the implant quality scale (IQS) of the replacement implants were recorded after delivering of the final prosthesis and annually thereafter. Ninety-six patients (100 implants) showed initial early failure (failure rate=0.98%). Sixty-six patients (male: 38; female: 28; mean age: 42.3±18.2years old) with early implant failure received a total of 67 replacement dental implants. Three patients with three implants dropped out of the study during the mean follow-up of 69.4±27.0months. The implant length and diameter were varied for seven sites. The number of sites that required additional surgeries increased from 18 to 24 for first and replacement implant insertion, respectively. One of the 67 replacement implants failed before prosthesis delivery, and one implant failure occurred 20months after prosthesis delivery, which represented a cumulative survival rate of 94.6%. At last follow-up evaluation, the overall mean MBL was 1.7±1.3mm. Two of 64 implants failed according to IQS criteria, three implants showed satisfactory survival, and one implant showed compromised survival. No pain or tenderness was observed in the rest 58 implants evaluated, showing a success rate (optimum health) of 90.6%. Within the limits of the present study, early implant failure was not an obstacle for implant replacement at the same site after an adequate soft and hard tissues healing period.

CT imaging during microwave ablation: analysis of spatial and temporal tissue contraction.

To analyze the spatial distribution and temporal development of liver tissue contraction during high-temperature ablation by using intraprocedural computed tomography (CT) imaging. A total of 46 aluminum fiducial markers were positioned in a 60 × 45 mm grid, in a single plane, around a microwave ablation antenna in each of six ex vivo bovine liver samples. Ablations were performed for 10 min at 100 W. CT data of the liver sample were acquired every 30 s during ablation. Fiducial motion between acquisitions was tracked in postprocessing and used to calculate measures of tissue contraction and contraction rates. The spatial distribution and temporal evolution of contraction were analyzed. Fiducial displacement indicated that the zone measured postablation was 8.2 ± 1.8 mm (∼20%) smaller in the radial direction and 7.1 ± 1.0 mm (∼10%) shorter in the longitudinal direction than the preablation tissue dimension. Therefore, the total ablation volume was reduced from its preablation value by approximately 45%. Very little longitudinal contraction was noted in the distal portion of the ablation zone. Central tissues contracted more than 60%, which was near an estimated limit of ∼70% based on initial water content. More peripheral tissues contracted only 15% in any direction. Contraction rates peaked during the first 60 s of heating with a roughly exponential decay over time. Ablation zones measured posttreatment are significantly smaller than the pretreatment tissue dimensions. Tissue contraction is spatially dependent, with the greatest effect occurring in the central ablation zone. Contraction rate peaks early and decays over time.

Advanced imaging and tissue engineering of the human limbal epithelial stem cell niche.

The limbal epithelial stem cell niche provides a unique, physically protective environment in which limbal epithelial stem cells reside in close proximity with accessory cell types and their secreted factors. The use of advanced imaging techniques is described to visualize the niche in three dimensions in native human corneal tissue. In addition, a protocol is provided for the isolation and culture of three different cell types, including human limbal epithelial stem cells from the limbal niche of human donor tissue. Finally, the process of incorporating these cells within plastic compressed collagen constructs to form a tissue-engineered corneal limbus is described and how immunohistochemical techniques may be applied to characterize cell phenotype therein.

Cellular basis of morphological variation and temperature-related plasticity in Drosophila melanogaster strains with divergent wing shapes.

Organ shape evolves through cross-generational changes in developmental patterns at cellular and/or tissue levels that ultimately alter tissue dimensions and final adult proportions. Here, we investigated the cellular basis of an artificially selected divergence in the outline shape of Drosophila melanogaster wings, by comparing flies with elongated or rounded wing shapes but with remarkably similar wing sizes. We also tested whether cellular plasticity in response to developmental temperature was altered by such selection. Results show that variation in cellular traits is associated with wing shape differences, and that cell number may play an important role in wing shape response to selection. Regarding the effects of developmental temperature, a size-related plastic response was observed, in that flies reared at 16°C developed larger wings with larger and more numerous cells across all intervein regions relative to flies reared at 25°C. Nevertheless, no conclusive indication of altered phenotypic plasticity was found between selection strains for any wing or cellular trait. We also described how cell area is distributed across different intervein regions. It follows that cell area tends to decrease along the anterior wing compartment and increase along the posterior one. Remarkably, such pattern was observed not only in the selected strains but also in the natural baseline population, suggesting that it might be canalized during development and was not altered by the intense program of artificial selection for divergent wing shapes.

Uniaxial and biaxial mechanical properties of porcine linea alba

Incisional hernia is a severe complication post-laparoscopic/laparotomy surgery that is commonly associated with the linea alba. However, the few studies on the mechanical properties of the linea alba in the literature appear contradictory, possible due to challenges with the physical dimensions of samples and variations in protocol. This study focuses on the tensile mechanical characterisation of the porcine linea alba, as determined by uniaxial and equi-load biaxial testing using image-based strain measurement methods. Results show that the linea alba demonstrated a non-linear elastic, anisotropic behaviour which is often observed in biological soft tissues. The transverse direction (parallel to fibres) was found to be approximately eight times stiffer than the longitudinal (cross-fibre) direction under both uniaxial and equi-load biaxial loading. The equi-load biaxial tensile tests revealed that contraction could occur in the transverse direction despite increasing load, probably due to the anisotropy of the tissue. Optical surface marker tracking and digital image correlation methods were found to greatly improve the accuracy of stretch measurement, resulting in a 75% change in the apparent stiffness compared to using strain derived from machine cross-head displacement. Additionally, a finite element model of the experiments using a combination of an Ogden and fibre exponential power law model for the linea alba was implemented to quantify the effect of clamping and tissue dimensions (which are suboptimal for tensile testing) on the results. The preliminary model results were used to apply a correction factor to the uniaxial experimental data prior to inverse optimisation to derive best fit material parameters for the fibre reinforced Ogden model. Application of the model to the equi-load biaxial case showed some differences compared to the experimental data, suggesting a more complex anisotropic model may be necessary to capture biaxial behaviour. These results provide an improved assessment of the mechanical properties of the porcine linea alba for wound closure and other studies.

Posters

Background A fuctional outcome was and still remains the main purpose of a periodontal surgical procedure. However, as implants have been part of dental routine, the 'Esthetics' factor has been gradually more considerable in the soft tissue augmentation. The keyword for an esthetic result is usually 'predictability'. In other words, a plastic surgery technique that can be predictable and repeatable in its clinical outcome is needed. Aim/Hypothesis The aim of this poster is to present the double-partial thickness, coronally positioned, bucally slibing flap. This is an alternative flap technique for soft tissue augmentation and its main benefit is a more esthetic outcome in periodontal surgery. Material and methods A 28 year-old male patient, referred to our dental clinic with a failed apicoectomy treated #21. The treatment plan involved an implant restoration. Both hard and soft tissues were in need of augmentation. The tooth was extracted and a Biomet 3i implant was placed. For the soft tissues augmentation the double-partial thickness, coronally positioned, bucally slibing flap technique was performed, while for the hard tissues augmentation, DFDBA particles were utilized and stabilized with a resorbable collagen membrane. Results The surgical outcome was more than satisfactory. Hard and soft tissues dimensions were considerably improved and no surgical scars remained after the healing period. Conclusion and clinical implications ?he double-partial thickness, coronally positioned, bucally slibing flap is an effective plastic periodontal surgery technique. The esthetic outcome is considered to be the main advantage. However, it's a challenging technique and needs microsurgery equipment to be performed.

Multi-resolution voxel phantom modeling: a high-resolution eye model for computational dosimetry

Voxel models of the human body are commonly used for simulating radiation dose with a Monte Carlo radiation transport code. Due to memory limitations, the voxel resolution of these computational phantoms is typically too large to accurately represent the dimensions of small features such as the eye. Recently reduced recommended dose limits to the lens of the eye, which is a radiosensitive tissue with a significant concern for cataract formation, has lent increased importance to understanding the dose to this tissue. A high-resolution eye model is constructed using physiological data for the dimensions of radiosensitive tissues, and combined with an existing set of whole-body models to form a multi-resolution voxel phantom, which is used with the MCNPX code to calculate radiation dose from various exposure types. This phantom provides an accurate representation of the radiation transport through the structures of the eye. Two alternate methods of including a high-resolution eye model within an existing whole-body model are developed. The accuracy and performance of each method is compared against existing computational phantoms.

Musculotendon variability influences tissue strains experienced by the biceps femoris long head muscle during high-speed running

The hamstring muscles frequently suffer injury during high-speed running, though the factors that make an individual more susceptible to injury remain poorly understood. The goals of this study were to measure the musculotendon dimensions of the biceps femoris long head (BFlh) muscle, the hamstring muscle injured most often, and to use computational models to assess the influence of variability in the BFlh’s dimensions on internal tissue strains during high-speed running. High-resolution magnetic resonance (MR) images were acquired over the thigh in 12 collegiate athletes, and musculotendon dimensions were measured in the proximal free tendon/aponeurosis, muscle and distal free tendon/aponeurosis. Finite element meshes were generated based on the average, standard deviation and range of BFlh dimensions. Simulation boundary conditions were defined to match muscle activation and musculotendon length change in the BFlh during high-speed running. Muscle and connective tissue dimensions were found to vary between subjects, with a coefficient of variation (CV) of 17±6% across all dimensions. For all simulations peak local strain was highest along the proximal myotendinous junction, which is where injury typically occurs. Model variations showed that peak local tissue strain increased as the proximal aponeurosis width narrowed and the muscle width widened. The aponeurosis width and muscle width variation models showed that the relative dimensions of these structures influence internal muscle tissue strains. The results of this study indicate that a musculotendon unit’s architecture influences its strain injury susceptibility during high-speed running.