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PubMed1986

Investigation of the zinc status of surgical patients--II. Influence of vascular reconstruction on the zinc status.

Patients admitted for major vascular reconstruction operations received an i.v. dose of 65Zn. From the increased whole-body retention of 65Zn and the findings on other parameters it was concluded that the was concluded that the post-operative zinc metabolism of these patients differed from that of the control subjects. Unexpectedly, this difference persisted for several months. These patients can probably serve as controls in studies of patients who have undergone surgery of the intestinal tract. Increase of whole-body retention of 65Zn may be a sensitive indicator for subclinical zinc deficiency, but application in practice is hampered by the long duration of the period required for the measurement. From the present results it seems likely that measurement of the retention of 65Zn in the forearm as a function of time yields the same information but in a considerably shorter time.

Aged↗
PubMed2006

Risk characterization and exposure assessment in arseniasis-endemic areas of Taiwan.

This paper examines the age-specific human health risks exposed to inorganic arsenic through arsenic-contaminated farmed fish/shrimp and groundwater consumptions in arseniasis-endemic areas of blackfoot disease (BFD)-endemic area and Lanyang Plain in Taiwan, based on an probabilistic integrated risk assessment framework. We employ an age-dependent predictive physiologically-based pharmacokinetic model to account for arsenic concentrations in target organs. We reconstruct age-specific dose-response profiles for arsenicosis and arsenic-induced cancers by best fitting a pharmacodynamics-based three-parameter Hill equation model to published epidemiological data from West Bengal and Taiwan. The predicted median arsenic concentrations in age group-specific skin, lung, and bladder ranged from 2.24-5.70, 3.76-9.46, and 5.11-20.71 micro g g(-1) in BFD-endemic area, whereas 4.98-12.04, 8.23-19.92, and 11.07-43.45 micro g g(-1) in Lanyang Plain, respectively. Risk analysis indicates that consumption of arsenic-contaminated farmed fish/shrimp and groundwater in arseniasis-endemic areas may increase threat to prevalence of arsenicosis for all age groups, whereas adults may undergo potential risks of arsenic-induced skin, lung and bladder cancers. We show that peoples in Lanyang Plain are more readily associated with higher morbidities for arsenicosis and skin cancer as well as fatalities for lung and bladder cancers than that of peoples in BFD-endemic area. Here we report the first case in which theoretical human health risks for consuming As-contaminated farmed fish/shrimp and groundwater in the arseniasis-endemic areas are alarming under a conservative condition based on a probabilistic risk assessment framework.

Adolescent↗
PubMed1997

Novel structural features of bovine papillomavirus capsid revealed by a three-dimensional reconstruction to 9 A resolution.

The three-dimensional structure of bovine papillomavirus has been determined to 9 A resolution by reconstruction of high resolution, low dose cryo-electron micrographs of quench-frozen virions. Although hexavalent and pentavalent capsomeres form star-shaped pentamers of the major capsid protein L1, they have distinct high-resolution structures. Most prominently, a 25 A hole in the centre of hexavalent capsomeres is occluded in the pentavalent capsomeres. This raises the possibility that the L2 minor capsid protein is located in the centre of the pentavalent capsomeres. Inter-capsomere connections approximately 10 A in diameter were clearly resolved. These link adjacent capsomeres and are reminiscent of the helical connections that stabilize polyomavirus.

Animals↗
PubMed2006

A shift-invariant filtered backprojection (FBP) cone-beam reconstruction algorithm for the source trajectory of two concentric circles using an equal weighting scheme.

In this paper, a shift-invariant filtered backprojection cone-beam image reconstruction algorithm is derived, based upon Katsevich's general inversion scheme, and validated for the source trajectory of two concentric circles. The source trajectory is complete according to Tuy's data sufficiency condition and is used as the basis for an exact image reconstruction algorithm. The algorithm proceeds according to the following steps. First, differentiate the cone-beam projection data with respect to the detector coordinates and with respect to the source trajectory parameter. The data are then separately filtered along three different orientations in the detector plane with a shift-invariant Hilbert kernel. Eight different filtration groups are obtained via linear combinations of weighted filtered data. Voxel-based backprojection is then carried out from eight sets of view angles, where separate filtered data are backprojected from each set according to the backprojection sets' associated filtration group. The algorithm is first derived for a scanning configuration consisting of two concentric and orthogonal circles. By performing an affine transformation on the image object, the developed image reconstruction algorithm has been generalized to the case where the two concentric circles are not orthogonal. Numerical simulations are presented to validate the reconstruction algorithm and demonstrate the dose advantage of the equal weighting scheme.

Algorithms↗
PubMedDate not supplied

A model of the translational apparatus based on a three-dimensional reconstruction of the Escherichia coli ribosome.

The morphology of the Escherichia coli ribosome, i.e., its shape at moderate to low (20-40 A (1 A = 0.1 nm)) resolution, provides important constraints in modeling both the folding of ribosomal RNA and the translational process. A new reconstruction, obtained by low-dose cryoelectron microscopy and image processing of single ribosomes, contains clues to the way in which the ribosome interacts with the key functional ligands: the mRNA and the A- and P-site tRNAs. It also suggests possible pathways of the nascent polypeptide chain. From an interpretation of these clues in the light of existing knowledge, a plausible model for the locations and interactions of key components of protein synthesis is suggested.

Escherichia coli↗
PubMed2004

Human serum provided additional values in growth factors supplemented medium for human chondrocytes monolayer expansion and engineered cartilage construction.

We have previously formulated an optimized human chondrocytes growth medium based on 2% fetal bovine serum supplementation. For clinical usage, the animal serum must be replaced by patient own serum. We investigated the effects of human serum concentration for human nasal septum chondrocytes monolayer culture and cartilage reconstruction. Human serum demonstrated a dose dependent manner in promoting chondrocytes growth and cartilage engineering.

Animals↗
PubMed2002

Reconstruction of electron spectra using singular component decomposition.

Reconstruction of electron spectra of medical accelerators from measured depth dose distributions is an attractive tool for commissioning of a Monte Carlo treatment planning system. However, the reconstruction method is an inverse radiation transport problem which is poorly conditioned, in the sense it may become unstable due to small perturbations in the input data. Predicting the sharp (delta-like) peak in the electron spectrum provides an additional challenge for the numerical reconstruction technique. To improve efficiency and robustness of the reconstruction technique, we developed an algorithm based on a separation of the electron spectrum into singular and regular components. We approximate the singular peak of the spectrum by a narrow weighted Gaussian function. The parameters of this Gaussian function are sought using only the fall-off and toe regions of the depth-dose curve. Analytical representation of the spectral peak by a Gaussian has benefit since only one weight and the mean and variance must be derived from the depth-dose curve instead of multiple spectra weights. The regular part of the spectrum is reconstructed from the residual depth-dose distribution using a variational method combined with a regularization technique to avoid the nonphysical oscillations. The effectiveness of the method is demonstrated by comparing predictions to "benchmark" spectra and depth-dose distributions from Monte Carlo simulation of medical accelerators.

Algorithms↗
PubMed1995

The effects of risedronate on canine cancellous bone remodeling: three-dimensional kinetic reconstruction of the remodeling site.

To investigate the dose-dependent effects of risedronate on cancellous bone remodeling, adult female beagle dogs were treated with either placebo, 0.1, 0.5, or 2.5 mg/kg/day of risedronate orally in an intermittent cyclic regimen (7 days on 21 days off), repeated three times. Iliac cancellous bone samples were subjected to histomorphometric analysis and three-dimensional (3-D) kinetic reconstruction of the remodeling site was performed. In the 0.1 mg/kg dose group, resorption and activation indices were no different from the placebo group. However, wall thickness was increased resulting in a positive bone balance at the level of the remodeling unit. In the 0.5 and 2.5 mg/kg dose groups, a dose-dependent reduction in activation frequency and tissue level bone formation was observed. Resorption rates were also significantly decreased, 60% and 80% for the 0.5- and 2.5-mg/kg groups, respectively. An approximate 25% reduction in final erosion depth was noted in both these groups. Analyses of the growth curves of the bone packet confirmed that the kinetics of the growth of a completed packet were different in the 0.5- and 2.5-mg/kg dose groups compared with placebo. These changes were associated with a significant increase in the final wall thickness in both groups indicating no net impairment of osteoblast function. These increases in wall thickness in combination with the reductions in final erosion depth in the 0.5 and 2.5 mg/kg groups resulted in a significant dose-dependent positive bone balance. This pharmacological profile suggests that risedronate may be of therapeutic utility in the treatment of metabolic bone diseases where reductions in activation frequency and resorptive cell activity at the level of the remodeling unit are a therapeutic goal.

Administration, Oral↗
PubMed2005

Reevaluation of radiation dose around the JCO site from the criticality accident in Tokai-mura.

Based on the monitoring data periodically taken during the JCO criticality accident in Tokai-mura, neutron and gamma-ray doses were evaluated at 13 points around the site boundary ranging from 73 to 540 m from the conversion building where the criticality took place. Radiation doses obtained by the present study were compared with the dose-distance curves developed through the works of the Nuclear Safety Commission Investigation Committee. The latter values are larger by 30 to 120% than the former at the 6 nearest points within 150 m from the conversion building, while they agree well at the points beyond 250 m. It is suggested that the shielding effects by the surrounding buildings around the conversion building contributed to the difference of estimated doses near the JCO boundary. To reconstruct the radiation environment realistically at the residential area near the JCO facilities, it is necessary to employ radiation transport calculations with three-dimensional models of the configuration around the conversion building. Radiation doses evaluated in the present study can be used to check the validity of such calculations based on the three-dimensional model.

Gamma Rays↗
PubMed2001

Monte Carlo simulation of a dynamic MLC based on a multiple source model.

Detailed knowledge of the characteristics of the radiation field shaped by a multileaf collimator (MLC) is essential in intensity modulated radiotherapy (IMRT). A previously developed multiple source model (MSM) for a 6 MV beam was extended to a 15 MV beam and supplemented with an accurate model of an 80-leaf dynamic MLC. Using the supplemented MSM and the MC code GEANT, lateral dose distributions were calculated in a water phantom and a portal water phantom. A field which is normally used for the validation of the step and shoot technique and a field from a realistic IMRT treatment plan delivered with dynamic MLC are investigated. To assess possible spectral changes caused by the modulation of beam intensity by an MLC, the energy spectra in five portal planes were calculated for moving slits of different widths. The extension of the MSM to 15 MV was validated by analysing energy fluences, depth doses and dose profiles. In addition, the MC-calculated primary energy spectrum was verified with an energy spectrum which was reconstructed from transmission measurements. MC-calculated dose profiles using the MSM for the step and shoot case and for the dynamic MLC case are in very good agreement with the measured data from film dosimetry. The investigation of a 13 cm wide field shows an increase in mean photon energy of up to 16% for the 0.25 cm slit compared to the open beam for 6 MV and of up to 6% for 15 MV, respectively. In conclusion, the MSM supplemented with the dynamic MLC has proven to be a powerful tool for investigational and benchmarking purposes or even for dose calculations in IMRT.

Computer Simulation↗
PubMedDate not supplied

Three-dimensional reconstruction from a single oblique section of fish muscle M-band.

A new method of three-dimensional image reconstruction from electron micrographs is presented here, which enables a three-dimensional image to be produced from a single oblique section of a two- or three-dimensional crystal. The method, which is most powerful when the section is thin and the angle of obliquity small, has several potential advantages over the conventional method of reconstruction using tilted views of the section. In particular the accumulated electron dose on the specimen is much smaller and the reconstruction is not affected by changes in the thickness of the section during exposure to the electron beam. The method involves the solution of a generally almost singular set of linear projection equations, relating through the sectioning geometry the three-dimensional crystal density to the two-dimensional projected image density. This can be achieved most conveniently by linear least squares filtering. An application of the method to determine the structure of the M-band of fish muscle is described. The resulting map agrees well with that produced by the more conventional approach involving tilted views.

Animals↗
PubMed1998

[Complex maxillofacial trauma: diagnostic contribution of multiplanar and tridimensional spiral CT imaging].

INTRODUCTION: Adequate radiologic assessment of the maxillofacial trauma patient is the basis for planning reparative surgery. We investigated the yield of the integration of axial CT with multiplanar (MP) and three-dimensional (3D) reconstructions with the Spiral technique. MATERIAL AND METHODS: Thirty-five patients (21 men and 14 women, mean age: 31.2 years) with complex maxillofacial traumas were submitted to Spiral CT. Images were acquired with 2-3-mm collimation, 1:1 to 2:1 pitch, 210 mAs, 120 kV, 15-24 s Spiral scan, RI = 1. 3D reconstructions were always obtained and used to guide MPRs targeted on the single injury. The examinations were retrospectively given a score, namely 1 if 3D and MPR yielded no more important diagnostic information than axial CT, 2 if 3D and MPR permitted better detailing of some axial CT findings and thus improved image reading, and 3 if 3D and MPR showed new injuries missed on axial images. Then, a radiologist and a maxillofacial surgeon reviewed the 3D images together only to assess in which cases they were useful to optimize surgical planning. RESULTS: Nine cases (25.7%) scored 1, seventeen (48.6%) scored 2 and nine (25.7%) scored 3. MP and 3D reconstructions were useful or determinant (2 + 3) in over 74% of cases. 3D images made surgical planning easier in 15 of 32 surgical patients (46.8%), allowing the surgeon a better panoramic view of the complex fracture. CONCLUSIONS: The greatest advantage of multiplanar imaging is the improved depiction of skeletal injuries along a horizontal plane, paralleling that of axial scans. The depiction of fractures of cribrum and of orbital roof and floor was particularly useful from a clinical viewpoint. MPRs clearly depicted herniation and incarceration of the lower rectus muscle in blow-out fractures. MP and 3D reconstructions better defined the presence and grade of displaced bone fragments in nearly vertical structures, such as the upward branches and coronoid apophysis of the mandible. 3D images alone never showed any more fractures than those seen on axial and MP images. 3D images are especially useful to the surgeon because they permit the panoramic depiction of the fracture complex, which facilitates treatment planning. The radiologist can use 3D reconstructions to guide the acquisition of targeted MP reconstructions, for better diagnostic yield. The Spiral technique, with its pitch increases up to 2, permits to limit the radiation dose while preserving the quality of postprocessing reconstructions. Finally, decreasing the execution time is important in multiple trauma patients who are often clinically unstable or have damaged vital organs.

Adult↗
PubMed2001

Reconstruction of 131I deposition density in regions of Belarus with estimation of thyroid doses from inhalation of 131I.

The relationship between 131I and 137Cs activity concentrations in 213 soil samples taken in 10 administrative districts of Belarus was derived. Analysis of the relationship shows a decreasing trend in the 131I/137Cs isotope ratio values with increasing 137Cs content in soil. Using the [131I-137Cs] relation obtained and the data on 137Cs contamination of settlements the 131I deposition density was evaluated for 1080 settlements situated in the area of investigation. Based on these assessments thyroid doses from inhalation of 131I were estimated. According to the results, the thyroid doses for the adult population vary from 5 to 40 mSv, the median dose is about 12 mSv. Uncertainties in the calculation of thyroid doses, based on the procedure applied, are discussed.

Adult↗
PubMed2005

The three-dimensional scintillation dosimetry method: test for a 106Ru eye plaque applicator.

The need for fast, accurate and high resolution dosimetric quality assurance in radiation therapy has been outpacing the development of new and improved 2D and 3D dosimetry techniques. This paper summarizes the efforts to create a novel and potentially very fast, 3D dosimetry method based on the observation of scintillation light from an irradiated liquid scintillator volume serving simultaneously as a phantom material and as a dose detector medium. The method, named three-dimensional scintillation dosimetry (3DSD), uses visible light images of the liquid scintillator volume at multiple angles and applies a tomographic algorithm to a series of these images to reconstruct the scintillation light emission density in each voxel of the volume. It is based on the hypothesis that with careful design and data processing, one can achieve acceptable proportionality between the local light emission density and the locally absorbed dose. The method is applied to a Ru-106 eye plaque immersed in a 16.4 cm3 liquid scintillator volume and the reconstructed 3D dose map is compared along selected profiles and planes with radiochromic film and diode measurements. The comparison indicates that the 3DSD method agrees, within 25% for most points or within approximately 2 mm distance to agreement, with the relative radiochromic film and diode dose distributions in a small (approximately 4.5 mm high and approximately 12 mm diameter) volume in the unobstructed, high gradient dose region outside the edge of the plaque. For a comparison, the reproducibility of the radiochromic film results for our measurements ranges from 10 to 15% within this volume. At present, the 3DSD method is not accurate close to the edge of the plaque, and further than approximately 10 mm (<10% central axis depth dose) from the plaque surface. Improvement strategies, considered important to provide a more accurate quick check of the dose profiles in 3D for brachytherapy applicators, are discussed.

Brachytherapy↗
PubMed1989

Image analysis of single macromolecules.

A battery of sophisticated techniques is now available to extract three-dimensional structural information from electron micrographs of biological macromolecules occurring in the form of single particles. One of these techniques, the random-conical reconstruction method, which allows low-dose imaging, has been recently perfected and is being used routinely for the study of ribosomal architecture. The analysis of the 40S mammalian ribosomal subunit serves as an illustration of the various steps of image processing. The use of classification combined with 3-D reconstruction provides the means to investigate variations of the macromolecular structure (deformations, conformational changes, etc.) that are caused by the specimen preparation. An example is provided by the changes in the shape of the 70S monosome of E. coli as it changes its orientation on the carbon grid. The most challenging applications of the techniques discussed are in the area of cryo-microscopy of ice-embedded specimens. First studies of single macromolecules imaged in this way have indicated that the 3-D imaging methods and, specifically, the random-conical reconstruction method, will be applicable under these conditions.

Analysis of Variance↗
PubMed2002

Safety of titanium mesh for orbital reconstruction.

During the past several decades, the standard of care for orbital reconstruction after trauma has been autogenous bone grafts. Complications of bone grafts, including donor site morbidities such as scar alopecia and graft resorption with delayed enophthalmos, have inspired an interest in the use of alloplastic substitutes such as titanium. Titanium's role in orbital reconstruction was limited originally to small orbital defects, and as an adjunct to bone grafts. More recently, clinical studies have documented the sole use of titanium mesh to reconstruct large orbital defects. This study sought to document further the safety and efficacy of titanium mesh in reconstructing large orbital defects after facial trauma, with more extensive follow-up compared with previous studies. In the current study, 55 patients with 67 orbital fractures underwent orbital reconstruction with titanium mesh over a 5-year period. Associated fractures were reduced anatomically and fixed rigidly. For the analysis, 44 patients with 56 orbital fractures had adequate follow-up (mean, 44 months). An abscess developed in one patient who received high-dose steroids for 72 hours before reconstruction. She was treated with broad-spectrum intravenous antibiotics and bedside incision and drainage, and did not require removal of the titanium mesh. No patient in the current series required removal of the titanium mesh. A single case of uncorrected enophthalmos was treated with bone grafting rather than mesh revision. Large orbital defects can be reconstructed using titanium mesh with good functional results and minimal risk for infection. This study covered the authors' first 5 years using titanium. They have now used titanium mesh in orbital reconstructions for more than 10 years, without any additional cases of infection.

Adolescent↗
PubMed1997

The success rate of free flaps after preoperative irradiation in head and neck reconstruction.

BACKGROUND AND AIMS: The reconstructive treatment of large head and neck tumours involves serious problems. Preoperative irradiation increases the risk of postoperative complications. Microvascular free flaps offer definite advantages over conventional reconstruction techniques and permit immediate preoperative high-dose radiation therapy. MATERIAL AND METHODS: In 1985-1996, at the Turku University Central Hospital, 101 patients, 61 (60%) men and 40 (40%) women (age range 15-79 years, mean 61 years), with head and neck tumours, underwent microvascular reconstructions, and 90 of them were irradiated before surgery. All irradiated patients underwent primary reconstruction immediately after resection. The total irradiation dose was about 60 Gy, usual range 50 to 65 Gy. The patients were operated on 3 to 5 weeks after discontinuation of irradiation therapy. RESULTS: Of the whole material of 101 free flaps, 89 (88%) were transferred successfully. The success rate in irradiated patients was 88% and in nonirradiated patients 91%. Reoperation had to be performed within twelve hours in three cases, with good results. Only two hernias occurred as donor complications (2%). Two of the patients died postoperatively (2%). Partial flap necrosis occurred in five patients and five patients underwent another reconstruction using a new free flap or with conventional reconstruction techniques. CONCLUSIONS: Free flaps are often the only acceptable choice in extensive head and neck primary reconstructions after irradiation. Microvascular free tissue transfers to the head and neck after preoperative irradiation has become the accepted method of reconstruction as a result of increased success rates with superior aesthetic and functional results.

Adolescent↗
PubMed2004

CT-fluoroscopy guided interstitial brachytherapy with image-based treatment planning for unresectable locally recurrent rectal carcinoma.

PURPOSE: The aim of the study is to develop high-dose-rate (HDR) conformal interstitial brachytherapy by means of combined CT-fluoroscopy guidance with CT-based treatment planning for locally recurrent rectal carcinoma. METHODS AND MATERIALS: Brachytherapy needle insertion was guided with a helical CT scanner providing continuous fluoroscopy reconstruction. A video monitor placed adjacent to the CT gantry simultaneously allowed the operator to see the process of needle insertion. Final CT images were transferred by an online system to the treatment-planning computer, which reconstructed the implant needles and organ contours. The doses in planning target volume were normalized and geometrically optimized. The patients received a brachytherapy dose at 5 Gy twice daily with a hypofractionated accelerated schedule at a total dose of 30-50 Gy with or without external radiation therapy. Eighteen patients were treated with this procedure. RESULTS: Ten to thirty-six needles (average, 17.3) were successfully placed to the planning target volume in each patient. The average time for CT fluoroscopy was 357 seconds for each procedure. No accident was seen at needle insertion, but 2 patients developed incomplete peroneal nerve palsy after needle removal, but gradually recovered. CT-based treatment planning was faster and more accurate than projection reconstruction with conventional radiograms. Analysis of the dose volume histogram showed conformal dose distribution to the target, while avoiding normal structures. CONCLUSION: CT fluoroscopy guidance ensures safety and increases the accuracy of needle placement in brachytherapy. Conformal high-dose-rate (HDR) interstitial brachytherapy with CT-based treatment planning is a method worth considering for locally recurrent rectal cancer.

Adenocarcinoma↗