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PubMed1998

[Optimization of PET image quality by means of 3D data acquisition and iterative image reconstruction].

PURPOSE: In the recent past, several algorithms have been developed in order to transform 3D sinograms acquired at volume PET systems into 2D data sets. These methods offer the possibility to combine the high sensitivity of the 3D measurement with the advantages of iterative 2D image reconstruction. The purpose of our study was the assessment of this approach by using phantom measurements and patient examinations. METHODS: The experiments were performed at the latest-generation whole-body PET system ECAT EXACT HR+. For 2D data acquisition, a collimator of thin tungsten septa was positioned in the field-of-view. Prior to image reconstruction, the measured 3D data were sorted into 2D sinograms by suing the Fourier rebinning (FORE) algorithm developed by M. Defrise. The standard filtered backprojection (FBP) method and an optimized ML/EM algorithm with overrelaxation for accelerated convergence were employed for image reconstruction. The spatial resolution of both methods as well as the convergence and noise properties of the ML/EM algorithm were studied in phantom measurements. Furthermore, patient data were acquired in the 2D mode as well as in the 3D mode and reconstructed with both techniques. RESULTS: At the same spatial resolution, the ML/EM-reconstructed images showed fewer and less prominent artefacts than the FBP-reconstructed images. The resulting improved detail conspicuously was achieved for the data acquired in the 2D mode as well as in the 3D mode. The best image quality was obtained by iterative 2D reconstruction of 3D data sets which were previously rebinned into 2D sinograms with help of the FORE algorithm. The phantom measurements revealed that 50 iteration steps with the optimized ML/EM algorithm were sufficient to keep the relative quantitation error below 5%. CONCLUSION: Our measurements show that the image quality in 3D PET can be improved by using iterative reconstruction techniques. The concept of 3D data acquisition and combining the FORE algorithm with 2D ML/EM reconstruction can readily be employed in clinical practice since the computation time is not considerably longer than that in iterative reconstruction of true 2D data.

Aged↗

PubMed1997

[Study of compression resistance of conventional or passive post and core reconstructed roots].

BACKGROUND: The object of this study is to estimate if the reconstructed roots with passive post and core have a greater resistance to compression in relation to reconstructed roots with traditional post and core. MATERIALS AND METHODS: Experimental situations have been reproduced as close as possible to real clinical situations simulating the cervical edge of the crown with a supporting cervical ring. A comparative analysis of the resistance to compression has been carried out using three groups of roots: the first group constructed from reconstructed roots with traditional post and core; the second group of reconstructed roots with passive post and core; the third group of roots were not reconstructed. RESULTS: Our results have shown that if the root reconstruction includes a metallic support ring that goes beyond the root plate by at least 1 mm there is no difference in the resistance to compression of statistical significance between reconstructed roots with passive post and core and reconstructed roots with traditional post and core. It turns out instead that there is a significant increase in resistance to compression of the reconstructed roots (because of the presence of the cervical support ring) in respect of the third group of unreconstructed roots.

Analysis of Variance↗

PubMed1998

Immediate breast reconstruction in breast cancer: morbidity and outcome.

Breast reconstruction is frequently performed for and requested by women with breast cancer. There are continued concerns about the safety of this procedure. We reviewed the Medical College of Georgia experience with immediate breast reconstruction to determine overall morbidity and whether premorbid risk factors could predict complications. Patients were reviewed with attention to epidemiologic characteristics, comorbid medical conditions, and risk factors; hospital and operative course; immediate wound complications; and patient survival. t test and chi-square analysis were performed to determine risk factors for developing wound complications. Between October 1990 and December 1996, 55 patients underwent 62 mastectomies and immediate reconstruction for breast cancer or contralateral prophylaxis. There were 13 stage 0, 23 stage I, 16 stage II, 4 stage III, and 1 stage IV tumors. There were 19 prosthetic and 43 autologous tissue reconstructions. Eighteen patients had 24 wound complications. Major complications occurred in eight patients and required reoperation for implant removal (two bilateral), ventral herniorrhaphy, and split thickness skin grafting for tissue loss. Patients who were obese were statistically more likely to develop surgical wound complications. Tobacco use, age, comorbid medical illness, operative blood loss, length of operation, and length of hospital stay did not predict for the development of wound complications. Patients who underwent prosthetic reconstruction had a significantly higher rate of major wound complications when compared with those who had autologous reconstruction. There was a single case of delay of chemotherapy secondary to surgical wound complication. There were no cases of autologous flap loss or local recurrence. Median survival is 23 months (1-72 months). At last follow-up, 53 patients are alive and without evidence of local recurrence. Breast reconstruction may be performed safely for most breast cancer patients. Autologous tissue reconstruction is preferred and carries significantly less major morbidity. Reconstruction should not delay adjuvant chemotherapy.

Adult↗

PubMed1998

[Customized 3D radiographic reconstruction of the human pelvis].

The pelvis is an essential element in the study of scoliosis since it constitutes the base of the spine and its orientation may affects postural balance. In order to study the role of the pelvis in the evolution and treatment of this disease, a new technique for the 3D personalised reconstruction of the pelvis was developed. It consists in identifying and digitizing 19 pelvic anatomical landmarks on postero-anterior and lateral x-rays and to reconstruct them in 3D with two techniques: the DLT algorithm developed by Marzan (1976) and, for 6 of the 19 landmarks, an adaptation of it called DLT with confidence coefficients. The latter takes into account the confidence given to the identification of the landmarks on each x-rays. Two methods were used to validate the reconstruction of the pelvis. The first one, used for 11 scoliotic patients and 2 dry pelvis specimens, consists in applying the reconstruction algorithm in an inverse way on the 3D coordinates of the reconstructed landmarks to obtain their 2D retroprojection on the x-ray planes, and thus comparing the retroprojected coordinates with the 2D digitized coordinates. The second method consists in measuring a dry pelvis specimen and comparing the 3D measured landmarks with the ones reconstructed with the x-rays of this specimen. For the first validation, results have shown that the lowest retroprojection errors (less than 2.5 +/- 2.6 mm) for the scoliotic patient group are located on the superior base of the sacrum, on the sacral curve and on the acetabula, while the highest (6.4 +/- 7.2 mm) were on the iliac crests. For the dry specimens, the retroprojection errors were below the millimeter. The second validation method showed 3D differences of 2.4 +/- 1.2 mm between measured and reconstructed landmarks of a dry specimen, which is of the same order of magnitude as what is reported in the literature for vertebrae. The reconstruction of the pelvis is thus considered adequate and its graphical wireframe representation allows to visualise and measure clinical indices concerning its orientation in space. Moreover, the reconstructed landmarks will be used to develop a personalised geometrical and mechanical model of the pelvis which, when integrated with the one for the spine and rib cage, will allow to simulate in a more realistic manner the biomechanical behaviour of the scoliotic trunk, particularly for the study of orthopaedic treatments with braces leaning on it.

Acetabulum↗

PubMedDate not supplied

Reconstruction of the frontal sinus and frontofacial skeleton with hydroxyapatite cement.

OBJECTIVE: To evaluate the efficacy of a newly developed biomaterial, hydroxyapatite cement, for use in frontal sinus and anterior craniofacial skeletal reconstruction. DESIGN: A nonrandomized patient cohort that was compared with historical controls of standard treatment with methyl methacrylate implants. SETTING: Craniofacial reconstructive surgery services at 3 referral health care centers. Eligible patients had frontal-cranial defects limited to a maximum size of 25 cm2. Patients were randomly selected volunteers with preexistent, acute traumatic or acute surgically induced defects of the frontal sinus and anterior craniofacial skeleton. All patients provided informed consent, and the study was approved by the 3 institutional review boards. Forty patients underwent reconstruction of defects of the anterior craniofacial region, and 38 of these patients were evaluable at 24 months. MAIN OUTCOME MEASURES: Hydroxyapatite cement was used to reconstruct full-thickness anterior craniofacial skull defects. Standard surgical techniques were used to place all implants. The primary outcome measurement was maintenance of implant volume determined at 24 months by computed tomography and clinical examination. Secondary outcome measures included incidence of complications and infections necessitating implant removal. RESULTS: Of the 38 evaluable patients, 31 had successful reconstructions at the end of the study, for an overall success of 82% for frontal sinus and frontofacial region reconstruction. Seven patients underwent explantation, 5 for surgical access to the site. Two implants were removed because of infection in the wound, for an overall incidence of approximately 5%. Explant biopsy specimens confirmed implant osseointegration and vascularization. CONCLUSIONS: Hydroxyapatite cement successfully reconstructs full-thickness defects of the frontal sinus and frontofacial region at 24 months. Hydroxyapatite cement appears to be superior to acrylic implants for frontal-cranial reconstruction and by allowing implant osseointegration with improved biocompatibility.

Adult↗

PubMedDate not supplied

Temporoparietal fascial flap in orbital reconstruction.

OBJECTIVE: To evaluate the success of the temporoparietal fascial flap (TPFF) in the primary or secondary reconstruction of difficult orbital defects and to review the surgical techniques. DESIGN: Retrospective analysis. SETTING: Tertiary medical center. PATIENTS: Nine patients with diverse orbital cavity or periorbital soft tissue and bony defects due to trauma, benign or malignant neoplasms, and radiation treatment. INTERVENTIONS: Temporoparietal fascial flap anatomy and techniques of harvest and inset are reviewed in detail. Four cases are presented to illustrate possible variables in orbital reconstruction. Variables examined include the location of defects, the success of flap survival in orbital cavities after primary or secondary reconstruction, the effects of prior irradiation on flap survival, and the possibility of concurrent osteointegrated implant placement with TPFF reconstruction. MAIN OUTCOME MEASURES: Functional and aesthetic outcomes were determined by physical examination and preoperative and postoperative photographs. RESULTS: All patients had successful transfer of TPFF grafts without flap compromise. Temporoparietal fascial flap was a viable option for subtle orbital and malar contour defects. In chronically inflamed wounds such as with osteoradionecrosis and orbitoantral fistula, TPFF successfully restored vascularity, obliterated the defects, and enabled the placement of osteointegrated implants. The TPFF also supported the concurrent placement of a free calvarial bone graft. Finally, split-thickness skin grafted onto a pedicled TPFF showed 100% survival. CONCLUSIONS: The TPFF is one of the most reliable and versatile regional flaps in the head and neck for orbital reconstruction. This study presents the use of TPFF in a variety of orbital defects, from lateral bony rim defects to total exenteration. Timing of repair in this study spans from immediate reconstruction to reconstruction delayed more than 50 years after the initial injury. In all cases, reconstruction with TPFF resulted in improved bony and soft tissue contours, and incurred minimal morbidity.

Adult↗

PubMed1999

The bridging lateral mandibular reconstruction plate revisited.

BACKGROUND: Lateral oromandibular reconstruction using a soft tissue free flap with a first-generation locking mandibular reconstruction plate (MRP) was rejected in a previous series by the senior author (K.E.B.) owing to a high incidence of delayed plate extrusion through the cheek skin. OBJECTIVE: To reexamine this method of reconstruction using a second-generation, low-profile MRP. PATIENTS AND DESIGN: A prospective case series of 27 patients with segmental defects of the lateral mandible after treatment of head and neck cancer. SETTING: An academic tertiary care referral center. INTERVENTION: All patients had mandibular continuity restored using the Leibinger Locking System (Stryker Leibinger Inc, Kalamazoo, Mich) MRP. Associated soft tissue defects were repaired using radial forearm (n = 22) or rectus abdominis (n= 5) free flaps. MAIN OUTCOME MEASURE: Incidence of hardware-related complications. RESULTS: All microvascular flap transfers were successful. One patient experienced a plate fracture 9 months after reconstruction. Only 1 patient experienced external plate exposure, 6 months after undergoing reconstruction of a through-and-through defect. Reconstruction was successful in 25 (93%) of the cases after a median follow-up period of 19.5 months. CONCLUSIONS: The high incidence of external plate exposure in patients undergoing lateral oromandibular reconstruction using soft tissue free flaps and first-generation locking MRPs may have resulted from a plate geometry that was prone to result in extrusion. After a similar length of follow-up, the incidence of reconstructive failure was reduced by using a low-profile, rounded-contour MRP. Final assessment of the durability of this technique will require long-term follow-up.

Adult↗

PubMed2002

Midface reconstruction with the fibula free flap.

OBJECTIVE: To evaluate the use, indications, and outcomes of the fibula osteocutaneous free flap when reconstructing the midface. DESIGN: Retrospective review of a case series. SETTING: Tertiary referral center. PATIENTS: We evaluated all patients requiring midface reconstruction after tumor resection between January 1, 1994, and January 1, 2000. Twenty-seven individuals who lacked sufficient retentive surfaces and/or teeth to support a conventional prosthesis were offered vascularized bony reconstruction. INTERVENTIONS: All patients underwent fibular osteocutaneous free flap reconstruction of the midface: 16 primarily, 11 secondarily. MAIN OUTCOME MEASURES: Success of free tissue transfer, perioperative complications, oral diet, speech, type of dental reconstruction, and cosmesis. RESULTS: Twenty-six of 27 flaps survived. Four patients had wound complications managed successfully with local wound care. Fourteen patients achieved a regular diet and 13 patients maintain a soft diet. Eighteen patients had osseointegrated implants placed, and 14 patients used an implant-borne prosthesis. Cosmetic results were judged to be excellent in 14 patients; good in 8; fair in 4; and poor in 1. CONCLUSIONS: Use of the fibula osteocutaneous free flap to reconstruct the midface is highly reliable and our flap of choice for lower maxillary defects requiring bony reconstruction. However, when orbitozygomatic support is the primary objective, the utility of this flap is limited. Because of the complexity of this procedure, the choice of midface reconstruction technique should be individualized for each patient.

Adolescent↗

PubMed1980

Alternatives in reconstructive surgery after mastectomy.

The modern era of breast reconstruction began about ten years ago. Today, reconstruction is possible for any woman who has had a mastectomy. The decision should be made only after discussion with both the woman's ablative surgeon and her plastic surgeon. Today there are a number of alternative methods to breast reconstruction. These include the following possibilities: immediate reconstruction, simple correction of a disturbing scar, reduction of a large remaining breast to simplify proper fitting of an external prosthesis, simple creation of a mound on the mastectomy side, insertion of a special prosthesis to fill in the subclavicular area, and reconstruction of the areolar nipple complex. Where more radical surgery has been done, the use of a myocutaneous flap, and in some special situations, reconstruction by means of microvascular anastomosis may be carried out. Some of these methods can be used in combination to fit the needs of the individual woman. It is the plastic surgeon's desire to help in the team approach in the treatment of breast cancer and by making suggestions to the ablative surgeon to make final reconstruction easier. Additional benefit might be the patients willingness to present herself earlier if she knows that in the long run reconstruction can be carried out.

Breast↗

PubMed2000

Use of the radial forearm fasciocutaneous free flap and montgomery salivary bypass tube for pharyngoesophageal reconstruction.

BACKGROUND: Head and neck reconstructive surgeons involved in pharyngoesophageal reconstruction have several options available to repair the defect after partial or total laryngopharyngectomy. There is no uniform agreement among head and neck surgeons as to which of the most frequently used techniques offers the best results. METHODS: A retrospective study was performed on 20 consecutive patients who had undergone reconstruction of the hypopharynx and cervical esophagus using a radial forearm free flap with Montgomery salivary bypass tube at the Massachusetts Eye and Ear Infirmary in Boston, Massachusetts, and St. Louis University, Department of Otolaryngology-Head and Neck Surgery between 1992 and 1996. This reconstruction was used for primary reconstruction after total or partial laryngopharyngectomy with cervical esophagectomy, partial pharyngectomy sparing the larynx, and for reconstruction of the stenotic neopharynx after laryngectomy. RESULTS: The overall rate of pharyngocutaneous fistula was 20%, and the rate of postoperative stricture was 10%. Of patients reconstructed with this technique, 85% were able to resume oral alimentation, whereas 15% remained G-tube dependent. Of the 18 patients who did not have their larynges remain intact, 6 were able to develop useful tracheoesophageal speech. CONCLUSIONS: The results of this study show that the radial forearm fasciocutaneous free flap in combination with the Montgomery salivary bypass tube is extremely useful for reconstruction of partial and circumferential defects of the hypopharynx and cervical esophagus.

Adult↗

PubMed2006

Evaluation of two 3D virtual computer reconstructions for comparison of cleft lip and palate to normal fetal microanatomy.

Cleft lip and palate reconstructive surgery requires thorough knowledge of normal and pathological labial, palatal, and velopharyngeal anatomy. This study compared two software algorithms and their 3D virtual anatomical reconstruction because exact 3D micromorphological reconstruction may improve learning, reveal spatial relationships, and provide data for mathematical modeling. Transverse and frontal serial sections of the midface of 18 fetal specimens (11th to 32nd gestational week) were used for two manual segmentation approaches. The first manual segmentation approach used bitmap images and either Windows-based or Mac-based SURFdriver commercial software that allowed manual contour matching, surface generation with average slice thickness, 3D triangulation, and real-time interactive virtual 3D reconstruction viewing. The second manual segmentation approach used tagged image format and platform-independent prototypical SeViSe software developed by one of the authors (F.W.). Distended or compressed structures were dynamically transformed. Registration was automatic but allowed manual correction, such as individual section thickness, surface generation, and interactive virtual 3D real-time viewing. SURFdriver permitted intuitive segmentation, easy manual offset correction, and the reconstruction showed complex spatial relationships in real time. However, frequent software crashes and erroneous landmarks appearing "out of the blue," requiring manual correction, were tedious. Individual section thickness, defined smoothing, and unlimited structure number could not be integrated. The reconstruction remained underdimensioned and not sufficiently accurate for this study's reconstruction problem. SeViSe permitted unlimited structure number, late addition of extra sections, and quantified smoothing and individual slice thickness; however, SeViSe required more elaborate work-up compared to SURFdriver, yet detailed and exact 3D reconstructions were created.

Cleft Lip↗

PubMed2003

Reoperations after prophylactic mastectomy with or without implant reconstruction.

BACKGROUND: The authors characterized the unanticipated reoperations after prophylactic mastectomy, with or without implant reconstruction. METHODS: The surgical cohort was comprised of 1417 women with a family history of breast carcinoma. The women received a prophylactic mastectomy with (bilateral, n = 593; contralateral, n = 506) or without reconstruction (n = 318) at the Mayo Clinic (Rochester, MN) between 1960 and 1993. Reoperations and indications for reoperation were compiled from medical records and a patient survey. RESULTS: Three hundred eighteen women received a bilateral (n = 39) or contralateral (n = 279) prophylactic mastectomy without reconstruction. With a median follow-up of 15 years, 18 women (6%) required reoperation. Most of these reoperations occurred within the first year after prophylactic mastectomy. Five hundred ninety-three women had reconstruction with implants following bilateral prophylactic mastectomy. Approximately one-half of the women (52%) required at least 1 unanticipated reoperation during a median follow-up of 14 years. Approximately 39% of all reoperations occurred within 1 year of breast reconstruction and 69% within 5 years. Implant-related issues were the most common cause for reoperation. Some women with breast carcinoma elected to receive contralateral prophylactic mastectomy with therapeutic mastectomy for the affected breast. Five hundred six women received reconstruction with implants. During a median follow-up of 8.8 years, 189 women (37%) required unanticipated reoperation. The most common indication was implant-related issues. The time course of reoperations was similar to that for women in the bilateral group. CONCLUSIONS: Surgical reoperations were fairly common among women who received prophylactic mastectomy with implant reconstruction. Most of the reoperations were implant related. Reoperations were fairly uncommon after prophylactic mastectomy without reconstruction.

Adult↗

PubMed2005

Correlates of breast reconstruction: results from a population-based study.

BACKGROUND: Immediate or early postmastectomy breast reconstruction is performed infrequently. To the authors' knowledge, little is known regarding surgeon or patient perspectives on reconstruction treatment decisions. The purpose of the current study was to identify patient attitudes and preferences associated with breast reconstruction, and whether these differed by race. METHODS: A sample of women age < or = 79 years who were diagnosed with ductal carcinoma in situ and invasive breast carcinoma between December 2001 and January 2003 was identified from the Surveillance, Epidemiology, and End Results (SEER) registries of Detroit and Los Angeles. Eligible subjects completed a questionnaire at a mean of 7 months after diagnosis. The Wald chi-square test and logistic regression were used for data analysis. RESULTS: Of the 1844 respondents, 646 underwent a mastectomy (35.0% of the total sample) and 245 of these patients received breast reconstruction (38.0%; of the mastectomy group). On multivariate analysis, younger patient age, higher educational levels, and earlier stage of disease were found to be significantly associated with breast reconstruction. Although 78.2% of women reported that breast reconstruction was discussed, only 11.2% correctly answered 3 basic knowledge questions regarding the procedure. The desire to avoid more surgery was the most common reason for not undergoing breast reconstruction. CONCLUSIONS: The results of the current study found that the majority of women were aware of breast reconstruction but choose not to undergo the procedure. Lack of knowledge and a greater perception of barriers to the procedure were more common among African-American patients and women with a lower education level, suggesting a need for improved educational strategies.

Aged↗

PubMed2006

Advances and surgical decision-making for breast reconstruction.

In patients who undergo breast reconstruction after mastectomy, choosing the appropriate timing and the best method of reconstruction are essential to optimize outcomes and to minimize the potential for postoperative complications. At The University of Texas M. D. Anderson Cancer Center, the clinicopathologic factors that are used in the surgical decision-making for breast reconstruction after mastectomy include the breast cancer stage, status of axillary sentinel lymph node, smoking status, body habitus, preexisting scars, prior radiation therapy, and planned or previous chemotherapy. Immediate breast reconstruction after mastectomy is preferable for patients who have a low risk of requiring postmastectomy radiation therapy (PMRT) (Stage I breast cancer). Delayed reconstruction may be preferable in patients who are deemed preoperatively to require PMRT (Stage III breast cancer) to avoid difficulties associated with radiation delivery after an immediate breast reconstruction. In patients who are deemed preoperatively to be at an increased risk of requiring PMRT (Stage II breast cancer), delayed-immediate breast reconstruction may provide an additional option. The approach to breast reconstruction will need to be adapted to maintain an appropriate balance between minimizing the risk of recurrence and providing the best possible aesthetic outcomes as the indications for PMRT and other treatment modalities continue to change.

Axilla↗

PubMed2004

Surgical management of maxillectomy defects based on the concept of buttress reconstruction.

BACKGROUND: Few published large series have described a surgical approach to maxillary skeletal reconstruction on the basis of the extent of maxillectomy. METHODS: We have reviewed a 10-year experience with 38 consecutive maxillary reconstructions with respect to maxillectomy defects, reconstructive procedures, reconstructed buttresses, and functional and aesthetic outcomes. RESULTS: Maxillectomy defects were classified into three categories on the basis of the buttress concept. Buttress reconstruction was most frequently performed in category III maxillary defects (56%), followed by category I (50%) and category II (20%). The vascularized composite autograft included the rectus abdominis myocutaneous free flap combined with costal cartilage, and the latissimus dorsi myocutaneous free flap combined with the V-shaped scapula is an effective method for reliable reconstruction of both skeletal and soft tissues. CONCLUSIONS: A critical assessment for skeletal defects and associated soft tissue defects is essential for an adequate approach to solve complex problems in maxillary reconstruction. On the basis of retrospective analysis of this series, a reconstructive algorithm for surgical management of maxillectomy defects is proposed.

Adult↗

PubMed2005

Analysis and comparison of morphological reconstructions of hippocampal field CA1 pyramidal cells.

Morphological reconstructions have become a routine and valuable tool for neuroscientists. The accuracy of reconstructions is a matter of considerable interest given that they are widely used in computational studies of neural function. Despite their wide usage, comparisons of reconstructions obtained using various methodologies are lacking. We reviewed reconstructions of hippocampal CA1 pyramidal cells from five published studies and found marked differences in some of the most basic measurements. For four of the five studies means of total cell length clustered in the 11,479-13,417-microm range. The remaining study had a significantly larger value for this index at 16,992+/-5,788 microm. Surface area means varied more than 4-fold from 16,074 to 67,102 microm2. Volume means varied more than 8-fold from 3,828 to 30,384 microm3. Simulated passive input resistance means varied from 38.0 to 172.1 MOmega, reflecting the variability in cell dimensions. Estimates of the electrotonic length varied from 1.26 to 1.56. In two reconstructions used in previously published studies, simulated somatic excitatory postsynaptic potentials (EPSPs) varied 2-4-fold in amplitude, time to peak and half-width, for synaptic inputs at similar locations. Substantial jitter on the z-axis was identified as one likely source of the discrepancy in total cell length, while substantial differences in diameter measurements across studies, and sometimes within the same study, accounted for the variability in surface area and volume. While some part of the observed variability is surely due to the diversity of CA1 pyramidal cells, our analysis suggests that a substantial portion stemmed from methodological inconsistencies and from technological limitations. Suggestions are made for improving the quality and usefulness of morphological reconstructions. We conclude that reconstructions across studies have substantial variability in measures that are very relevant to neuronal function. Consequently, modelers are advised to use more than just one reconstructed cell in their simulations of neural function.

Animals↗

PubMed2003

In vivo efficacy of bone-marrow-coated polycaprolactone scaffolds for the reconstruction of orbital defects in the pig.

Alloplastic materials offer a number of advantages over bone autografts in the reconstruction of craniofacial defects. These include: lack of donor site morbidity, unlimited quantities of available material, and the possibility to conform exactly to the defect. An ideal bioresorbable material would degrade slowly, and have osteoconductive properties to allow replacement and remodeling by osseous tissue. This is seldom observed, the materials instead being replaced by fibrous tissue. Polycaprolactone (PCL), an FDA-approved bioresorbable polymer, has several properties that might make it suitable for reconstruction of craniofacial defects. The technique of fused deposition modeling (FDM) allows for the fabrication of highly reproducible bioresorbable 3D scaffolds. The nature of the fully interconnected pore network might enhance vascular ingrowth and osteoconductive properties. It was hypothesized that coating the scaffolds in bone marrow might enhance bone formation due to the osteoinductive nature of the bone-marrow mesenchymal cells. This study aimed to test these hypotheses in the pig model. Defects measuring 2 x 2 cm were surgically created in each orbit of eight Yorkshire pigs. The orbits were divided into three groups: Group 1 (n=4), no reconstruction (control); Group 2 (n=6), reconstruction with no coated PCL scaffolds; and Group 3 (n=6) reconstruction with bone-marrow-coated PCL scaffolds. The results were evaluated at 3 months by histological and histomorphometric analyses. The defects in Group 1 were covered with fibrous scar tissue. The shape of the reconstructed area was insufficient. The defects in Groups 2 and 3 were reconstructed correctly. In Group 2 the noncoated scaffolds showed 4.5% of new bone formation compared with 14.1% in Group 3, which is statistically significant (p<0.05). The entirely interconnected 3D polycaprolactone scaffold seems to be a promising material. It induces the bone ingrowth required for reconstructing craniofacial and orbital defects. Further long-term evaluations of these PCL scaffolds must be made in order to confirm these conclusions.

Absorbable Implants↗

PubMedDate not supplied

Three-dimensional intravascular ultrasonography: reconstruction of endovascular stents in vitro and in vivo.

BACKGROUND: Intravascular ultrasonography displays an artery in loosely related cross-sectional images with limited axial information. However, intravascular ultrasound images are suited to three-dimensional reconstruction. METHODS: A comprehensive intravascular ultrasound imaging system was used to reconstruct planar images in three-dimensions. This system consisted of a 25MHz transducer-tipped rigid probe (for in vitro studies) or a 25MHz transducer-tipped catheter within a 3.9F monorail imaging sheath (for in vivo studies), a motorized catheter pullback device that withdraws the transducer at 0.5mm/s, and an image processing computer that stacks 15 cross-sectional images/mm of stent axial length and then performs thresholding-based three-dimensional image rendering. We imaged 10 stents (4 Palmaz-Schatz, 3 Wiktor, 2 Strecker, and 1 Medinvent) in vitro after implantation in freshly harvested saphenous veins and 37 Palmaz-Schatz stents in vivo, 10 in native coronary arteries and 27 in vein grafts, 21 acutely and 18 on follow-up. RESULTS: Three-dimensional reconstruction of images obtained with this system reproduced the geometry of each stent design. In vitro, images of the Palmaz-Schatz stents showed the expanded diamonds, the central articulation, and flaring of both ends of both halves of the stents. Images of the Wiktor stents showed the sinusoidal wave-shaped coils in their helical configuration. Images of the Strecker stents showed the interlocking-loop design with gaps between the terminal loops at either end of the stent. Images of the Medivent stent reproduced the woven texture formed by braiding the stent wires. Three-dimensional reconstruction of images obtained in vivo also reproduced the spatial geometry of the Palmaz-Schatz stent. However, reconstruction of in vivo images was limited by cardiac-cycle-linked vessel motion and torsion and the presence of echo-dense tissue that could not be separated completely from the stent itself. CONCLUSIONS: Properly acquired intravascular ultrasound images can be used to reconstruct the spatial geometry of endovascular stents. Because stent spatial geometry is known and unambiguous, reconstruction of endovascular stents should be one of the tests of imaging systems designed to perform three-dimensional reconstruction of ultrasound images.

Adult↗