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Results for “Dose Reconstruction”

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PubMed2003

[Radiotherapy and delayed breast reconstruction with implant: examination of compatibility].

PURPOSE: Delayed breast reconstruction with implant is frequently used after mastectomy. However, given that many breast cancer patients receive adjuvant radiotherapy, the adaptation of this method raises questions concerning possible cumulative complications. In the present study the compatibility of post-mastectomy radiotherapy and delayed breast reconstruction with implant was examined. PATIENTS AND METHODS: We evaluated a consecutive series of 66 invasive breast cancer patients who have received delayed breast reconstruction with implant after modified radical mastectomy between January 1997 and June 1999. The average time was 51 months from primary surgery to reconstruction. The median dose of loco-regional irradiation was 50 Gy. Grade III atrophic dermatitis was observed in none of the irradiated women. We identified two patient groups: 29 patients did not and 37 patients did receive post-mastectomy radiotherapy. The types and time of reconstruction related chronic complications (capsular contracture, defect of implant shell and skin necrosis) were recorded. Incidence of complications was estimated by the Kaplan-Meier method. Cancer related events were also studied. RESULTS: When expander was used, minor discomfort of the patients was common during the filling course. At four (11%) irradiated patients the expansion with expander was incomplete, due to severe pain. At a median follow up time of 53 months the incidence of capsular contracture was 24.1% without and 29.7% with radiotherapy (p=0.4121). The five-year estimated rate of late complications was 40% and 50%, respectively (relative risk: 1.29, 95% confidence interval: 0.58-2.89, p=0.5173). The position of implant had an impact on the incidence of capsular contracture: 46.2% with subcutaneous and 22.6% with submuscular position (p=0.0881). Four patients (6%) developed local relapse (three in the skin and one subcutaneous). All were treated with tumor excision without implant removal. CONCLUSION: Delayed breast reconstruction with implant after post-mastectomy radiotherapy can be offered to patients who are interested in breast reconstruction and had no severe late radiation skin toxicity. Post-mastectomy radiotherapy does not significantly increase the risk of complications. The use of skin expander is less tolerated by irradiated patients. Submuscular position of implants moderates the risk of capsular contracture.

Adult↗

PubMed2002

Comparison of cutaneous bioavailability of cosmetic preparations containing caffeine or alpha-tocopherol applied on human skin models or human skin ex vivo at finite doses.

The use of human skin models for performing cutaneous bioavailability studies has been little investigated. For instance, only few studies have been reported on human skin models dealing with vehicle effects on percutaneous penetration. The present study aimed at evaluating the influence on caffeine's and alpha-tocopherol's cutaneous bioavailability of cosmetic vehicles such as a water-in-oil emulsion, an oil-in-water emulsion, a liposome dispersion and a hydrogel applied at finite dose using the reconstructed human skin models EpiDerm and Episkin. The results were compared with those obtained in human skin ex vivo using similar experimental conditions. It was demonstrated that the rank order of solute permeability could be correctly predicted when the preparation was applied at a finite dose in human skin models, at least when solutes with far different physicochemical properties such as caffeine and alpha-tocopherol were used. If only slight effects of cosmetic vehicle on skin bioavailability were observed in human skin ex vivo, they were less predictable using skin models. Especially, alcohol-containing vehicles seemed to behave differently in EpiDerm as well as in Episkin than on human skin ex vivo. Stratum corneum intercellular lipid composition and organization of human skin models differ to some extent from that of human stratum corneum ex vivo, which contributes to less pronounced barrier properties, together with the increased hydration of the outermost stratum corneum layers of the models. These features, as well as still unknown factors, may explain the differences observed in vehicle effects in human skin ex vivo versus human skin models.

Biological Availability↗

PubMed2000

An independent dose-to-point calculation program for the verification of high-dose-rate brachytherapy treatment planning.

PURPOSE: We describe computer software that performs, quickly and accurately, secondary dose calculations for high-dose-rate (HDR) treatment plans, including those employed for prostate treatments. METHODS: The program takes as primary input the data file used by the HDR remote afterloader console for treatment. Dosimetric calculations are performed using the Meisberger polynomial and the anisotropy table for the HDR Iridium-192 source. For standard applicators, treatment geometry is automatically reconstructed and the dose is calculated at relevant reference point(s). Template-based treatment plans (e.g., prostate) require additional user input; the dose calculation is then performed at user-selected reference points. A total dwell time calculation for volume and planar implants using the Manchester tables was also implemented. RESULTS: For fixed-geometry HDR procedures, secondary dose calculations are within 2% of the treatment plan, and results are available for review instantly. For more general applications, the calculated and planned doses are typically within 3% at the prescription isodose line. The Manchester-based dwell time calculation is within 10% of the planned time.

Algorithms↗

PubMed2002

Suitability of FISH painting techniques for the detection of partial-body irradiations for biological dosimetry.

Peripheral blood was irradiated with 2, 3, 4 or 5 Gy of X rays and was mixed with nonirradiated blood at five different dilutions to simulate partial-body irradiations. Analysis by FISH was performed using whole-chromosome painting probes for chromosomes 1, 4 and 11 in combination with a pancentromeric probe. Chromosome aberrations affecting the painted fraction were classified according to the PAINT nomenclature; other unstable aberrations affecting the unpainted material were also recorded. To evaluate the suitability of painting for dose assessment in partial-body irradiations, the ability of the u test and a proposed s test to detect the expected overdispersion and the similarity between the real doses and the doses estimated using Dolphin's approach were considered. For short-term biodosimetry, compared with solid-stained dicentric analyses, the suitability of FISH painting techniques for the detection of partial-body exposures is reduced, because of the decrease in the frequency of aberrations detected by FISH and in the number of cells with two or more aberrations. For reconstruction of past doses, when only complete apparently simple translocations in cells free of unstable aberrations were considered, the detection of the overdispersion and the accuracy of dose estimations were dramatically reduced. In a partial-body exposure, as the original dose increased, the whole-body dose estimated a long time after irradiation would tend to be lower, and the difference from the original dose would tend to be greater.

Adult↗

PubMed1996

Early results of infrageniculate arterial reconstruction using cryopreserved homograft saphenous conduit (CADVEIN) and combination low-dose systemic immunosuppression.

BACKGROUND: The search continues for the ideal conduit for infrageniculate arterial reconstructions when the autogenous vein is unsuitable or unavailable. Based on experimental observations in our laboratory demonstrating improvement in canine cryopreserved allograft vein patency using systemic immunosuppression (Imsup), and the remarkable clinical success achieved in older (greater than 60 years of age) solid organ transplant recipients using combination low-dose Imsup, we studied the effects of Imsup on patency of cryopreserved homograft saphenous vein (CADVEIN) used for infrageniculate arterial reconstructions. STUDY DESIGN: Under the Institutional Review Board protocol, 21 infrageniculate CADVEIN grafts were placed in 19 patients between July 1993 and August 1994 for limb salvage when autogenous veins were unavailable. An immunopharmacologic protocol consisting of low-dose cyclosporine A, azathioprine, prednisone, warfarin, aspirin, and vasodilators given orally was instituted. For various reasons, 15 patients in group 1 received Imsup; five patients never received Imsup, and one patient in group 2 received Imsup briefly. Follow-up examinations were completed using the time range of six to 18 months (mean, eight plus or minus one month). RESULTS: One patient died (5.3 percent) 30 days after emergency combined venous graft and bilateral CADVEIN bypass. The actuarial 12-month primary patency in group 1 was 59.4 percent compared with 16.7 percent in group 2 (p < 0.015, log-rank test). Cellular rejection was typically seen in explanted CADVEIN. Systemic morbidity related to Imsup was minimal. The CADVEIN morbidity rate was significant: three graft aneurysms and four early graft ruptures. Major amputations were necessary in eight of 12 patients with graft closure. CONCLUSIONS: The data suggest that Imsup significantly improves CADVEIN patency with limited systemic morbidity; however, complications related to the conduit itself occurred with greater frequency and cause greater morbidity than when the autogenous veins were used. Much has yet to be learned regarding the preservation characteristics of CADVEIN and the immunologic interactions in patients receiving CADVEIN grafts, before further clinical use of this conduit can be recommended.

Adult↗

PubMed2000

Virtual computed tomography colonoscopy: artifacts, image quality and radiation dose load in a cadaver study.

The purpose of our study was to evaluate the interdependency of spatial resolution, image reconstruction artifacts, and radiation doses in virtual CT colonoscopy by comparing various CT scanning protocols. A pig's colon with several artificial polypoid lesions was imaged after air insufflation with helical CT scanning using 1-, 3-, and 5-mm collimation, and pitch values varying from 1.0 to 3.0. Virtual endoscopic images and "fly through" sequences were calculated on a Sun Sparc 20 workstation (Navigator Software, GE Medical Systems, Milwaukee, Wis.). Several reconstruction artifacts as well as overall image quality were evaluated by three independent reviewers. In addition, radiation doses for the different CT protocols were measured as multiple-scan average dose using a 10-cm ion chamber and a standard Plexiglass body phantom. Generally, image quality and reconstruction artifacts were less affected by pitch values than by beam collimation. Thus, narrow beam collimation at higher pitch values (e. g. 3 mm/2.0) seems to be a reasonable compromise between quality of virtual endoscopic images and radiation dose load.

Animals↗

PubMed2006

Three-dimensional dose verification for intensity modulated radiation therapy using optical CT based polymer gel dosimetry.

Dose distributions generated from intensity-modulated-radiation-therapy (IMRT) treatment planning present high dose gradient regions in the boundaries between the target and the surrounding critical organs. Dose accuracy in these areas can be critical, and may affect the treatment. With the increasing use of IMRT in radiotherapy, there is an increased need for a dosimeter that allows for accurate determination of three-dimensional (3D) dose distributions with high spatial resolution. In this study, polymer gel dosimetry and an optical CT scanner have been employed to implement 3D dose verification for IMRT. A plastic cylinder of 17 cm diameter and 12 cm height, filled with BANG3 polymer gels (MGS Research, Inc., Madison, CT) and modified to optimal dose-response characteristics, was used for IMRT dose verification. The cylindrical gel phantom was immersed in a 24 x 24 x 20 cm water tank for an IMRT irradiation. The irradiated gel sample was then scanned with an optical CT scanner (MGS Research Inc., Madison, CT) utilizing a single He-Ne laser beam and a single photodiode detector. Similar to the x-ray CT process, filtered back-projection was used to reconstruct the 3D dose distribution. The dose distributions measured from the gel were compared with those from the IMRT treatment planning system. For comparative dosimetry, a solid water phantom of 24 x 24 x 20 cm, having the same geometry as the water tank for the gel phantom, was used for EDR2 film and ion chamber measurements. Root mean square (rms) deviations for both dose difference and distance-to-agreement (DTA) were used in three-dimensional analysis of the dose distribution comparison between treatment planning calculations and the gel measurement. Comparison of planar dose distributions among gel dosimeter, film, and the treatment planning system showed that the isodose lines were in good agreement on selected planes in axial, coronal, and sagittal orientations. Absolute point-dose verification was performed with ion chamber measurements at four different points, varying from 48% to 110% of the prescribed dose. The measured and calculated doses were found to agree to within 4.2% at all measurement points. For the comparison between the gel measurement and treatment planning calculations, rms deviations were 2%-6% for dose difference and 1-3 mm for DTA, at 60%-110% doses levels. The results from this study show that optical CT based polymer gel dosimetry has the potential to provide a high resolution, accurate, three-dimensional tool for IMRT dose distribution verification.

Algorithms↗

PubMed2006

Computer-aided detection of colonic polyps using low-dose CT acquisitions.

RATIONALE AND OBJECTIVES: This report proposes an alternative method for the automatic detection of colonic polyps that is robust enough to be directly applicable on low-dose computed tomographic data. MATERIALS AND METHODS: The polyp modeling process takes into account both the gray-level appearance of polyps (intensity profiles) and their geometry (extended Gaussian images). Spherical harmonic decompositions are used for comparison purposes, allowing fast estimation of the similarity between a candidate and a set of previously computed models. Starting from the original raw data (acquired at 55 mA), five patient data sets (prone and supine scans) are reconstructed at different dose levels (to 5 mA) by using different kernel filters, slice overlaps, and increments. Additionally, the efficacy of applying an edge-preserving smoothing filter before detection is assessed. RESULTS: Although image quality decreases when decreasing acquisition milliamperes, all polyps greater than 6 mm are detected successfully, even at 15 mA. Although not important at high doses, smoothing improves detection results for ultra-low-dose (tube current<15 mA) data. CONCLUSION: The advantage of low-dose scans is a significant decrease in effective dose from 4.93 to 1.61 mSv while retaining high detection values, particularly important when thinking of population screening.

Algorithms↗

PubMedDate not supplied

Electron beam depth dose scaling by means of effective atomic number reconstructed from CT scans.

A method is developed by which the computed tomography scans of a medium carried out at a number of diagnostic energies can be utilized to obtain the in situ "Effective Atomic Number" and "Effective Density". The electron depth dose curves in water when scaled by these factors estimate the actual electron depth dose distribution in that medium. It appears that the use of CT scans for electron beam treatment planning, in the management of cancer, is quite promising.

Electrons↗

PubMed2005

Accelerated partial breast irradiation: an analysis of variables associated with late toxicity and long-term cosmetic outcome after high-dose-rate interstitial brachytherapy.

PURPOSE: To perform a detailed analysis of variables associated with late tissue effects of high-dose-rate (HDR) interstitial brachytherapy accelerated partial breast irradiation (APBI) in a large cohort of patients with prolonged follow-up. METHODS AND MATERIALS: Beginning in 1995, 75 women with Stage I/II breast cancer were enrolled in identical institutional trials evaluating APBI as monotherapy after lumpectomy. Patients eligible included those with T1-2, N0-1 (<or=3 nodes positive), M0 tumors of nonlobular histology with negative surgical margins, no extracapsular nodal extension, and negative results on postexcision mammogram. All patients underwent surgical excision and postoperative irradiation with HDR interstitial brachytherapy. The planning target volume was defined as the excision cavity plus a 2-cm margin. Treatment was delivered with a high-activity Ir-192 source at 3.4 Gy per fraction twice daily for 5 days to a total dose of 34 Gy. Dosimetric analyses were performed with three-dimensional postimplant dose and volume reconstructions. All patients were evaluated at 3-6-month intervals and assessed with a standardized cosmetic rating scale and according to Radiation Therapy Oncology Group late normal tissue toxicity scoring criteria. Clinical and therapy-related features were analyzed for their relationship to cosmetic outcome and toxicity rating. Clinical features analyzed included age, volume of resection, history of diabetes or hypertension, extent of axillary surgery, and systemic therapies. Therapy-related features analyzed included volume of tissue encompassed by the 100%, 150%, and 200% isodose lines (V100, V150, and V200, respectively), the dose homogeneity index (DHI), number of source dwell positions, and planar separation. RESULTS: The median follow-up of all patients was 73 months (range, 43-118 months). The cosmetic outcome at last follow-up was rated as excellent, good, and fair/poor in 67%, 24%, and 9% of patients, respectively. Suboptimal cosmetic outcome was significantly associated with the number of source dwell positions, V150, and V200 and inversely associated with DHI (0.77 vs. 0.73; p=0.05). Late skin toxicity was rated as Grade 0, 1, or 2 in 77%, 19%, and 4% of patients, respectively. The risk of Grade 1/2 skin toxicity was significantly associated with V150 and V200 and inversely associated with DHI (0.77 vs. 0.71; p=0.009). Late subcutaneous toxicity was rated as Grade 0, 1, 2, 3, or 4 in 55%, 15%, 12%, 5%, and 13% of patients, respectively. The risk of Grade 0/1 vs. Grade 2-4 subcutaneous toxicity was significantly associated only with a lower value of DHI (0.77 vs. 0.73; p=0.02). To further explore factors that might contribute to the risk of fat necrosis (symptomatic or asymptomatic), a separate analysis showed that only dose hotspots as reflected in V150 and V200 were significantly associated with elevated risk. The use of adriamycin-based chemotherapy after APBI was found to be associated with a significant increase in the incidence of higher-grade skin toxicity and a higher risk of fat necrosis and suboptimal cosmetic outcome. Patient age, volume of resection, extent of axillary surgery, a history of diabetes or hypertension, and the use of tamoxifen were not found to be significantly associated with cosmetic outcome or late normal tissue complications. CONCLUSIONS: Long-term cosmetic results and the risk of late skin and subcutaneous toxicity after APBI with interstitial HDR brachytherapy can be correlated with specific treatment-related variables. These data provide dosimetric parameters that might be used to minimize the risk of normal tissue injury after APBI interstitial brachytherapy.

Adipose Tissue↗

PubMed2001

Clinically evident fat necrosis in women treated with high-dose-rate brachytherapy alone for early-stage breast cancer.

PURPOSE: To investigate the incidence of and variables associated with clinically evident fat necrosis in women treated on a protocol of high-dose-rate (HDR) brachytherapy alone without external-beam whole-breast irradiation for early-stage breast carcinoma. METHODS AND MATERIALS: From 6/1997 until 8/1999, 30 women diagnosed with Stage I or II breast carcinoma underwent surgical excision and postoperative irradiation via HDR brachytherapy implant as part of a multi-institutional clinical Phase I/II protocol. Patients eligible included those with T1, T2, N0, N1 (< or = 3 nodes positive), M0 tumors of nonlobular histology with negative surgical margins, no extracapsular lymph-node extension, and a negative postexcision mammogram. Brachytherapy catheters were placed at the initial excision, re-excision, or at the time of axillary sampling. Direct visualization, surgical clips, ultrasound, or CT scans assisted in delineating the target volume defined as the excision cavity plus 2-cm margin. High activity (192)Ir (3-10 Ci) was used to deliver 340 cGy per fraction, 2 fractions per day, for 5 consecutive days to a total dose of 34 Gy to the target volume. Source position and dwell times were calculated using standard volume optimization techniques. Dosimetric analyses were performed with three-dimensional postimplant dose and volume reconstructions. The median follow-up of all patients was 24 months (range, 12-36 months). RESULTS: Eight patients (crude incidence of 27%) developed clinically evident fat necrosis postimplant in the treated breast. Fat necrosis was determined by clinical presentation including pain and swelling in the treated volume, computed tomography, and/or biopsy. All symptomatic patients (7 of 8 cases) were successfully treated with 3 to 12 months of conservative management. Continuous variables that were found to be associated significantly with fat necrosis included the number of source dwell positions (p = 0.04), and the volume of tissue which received fractional doses of 340 cGy, 510 cGy, and 680 cGy (p = 0.03, p = 0.01, and p = 0.01, respectively). Other continuous variables including patient age, total excised tissue volume, tumor size, number of catheters, number of days the catheters were in place, planar separation, dose homogeneity index (DHI), and uniformity index (UI) were not significant. Discrete variables including the presence/absence of DCIS, sentinel versus full axillary nodal assessment, receptor status, presence/absence of diabetes, and the use of chemotherapy or hormone therapy were not found to have a significant association with the risk of fat necrosis. CONCLUSIONS: In this study of HDR brachytherapy of the breast tumor excision cavity plus margin, treatment was planned and delivered in accordance with the dosimetric parameters of the protocol resulting in a high degree of target volume dose homogeneity. Nonetheless, at a median follow-up of 24 months, a high rate of clinically definable fat necrosis occurred. The overall implant volume as reflected in the number of source dwell positions and the volume of breast tissue receiving fractional doses of 340, 510, and 680 cGy were significantly associated with fat necrosis. Future dosimetric optimization algorithms for HDR breast brachytherapy will need to include these factors to minimize the risk of fat necrosis.

Adult↗

PubMed1992

Proton beams in radiation therapy.

The rationale for study of proton radiation therapy is that, for some anatomic sites and tumors, the treatment volume is smaller; i.e., there is less irradiation of nontarget tissue while the target is included in three dimensions at each treatment session. As a result, the dose to the target can be raised. The consequence is that the tumor control probability improves and the frequency and severity of treatment-related morbidity decrease. These results come about from the physical fact that the proton range in tissue is finite; in comparison, absorption of photons is an exponential function and, hence, some dose is received for the full-beam path through the body. Accordingly, the dose deep to the target for proton treatments can be zero for each beam path. This situation provides a virtually certain means of improving the treatment outcome for selected categories of patients. Experience to date with proton radiation therapy has been quite limited. As of June 1991, the total number of proton radiation-treated patients was 11,763 from the various centers. Of that number, approximately 46% and 32% have been treated for small benign intracranial lesions (principally pituitary adenomas and arteriovenous malformations) and for tumors of the eye, respectively. Thus, only some 2500 patients have been treated for all other tumor types. The results from three centers and approximately 2800 patients with uveal melanoma are that the local control rate was 96% (for failures in-field, marginal, and in other parts of the eye). The local control results for chondrosarcomas and chordomas of the skull base are 91% and 65%, respectively. These percentages compare with some 35% achieved with conventional treatment. Experience with arteriovenous malformations indicates that control of bleeding and disappearance of the lesion are comparable to those achieved by other procedures. The developments from the proton therapy programs have contributed greatly to radiation treatment planning, e.g., the first three-dimensional treatment planning system put into regular clinical use (uveal melanoma), beam's eye view, digital-reconstructed radiograph, dose-volume histograms, and definitions of the uncertainty in dose around any defined point. The potential for clinical gains is high. In May 1991, the Proton Radiation Oncology Group was formed to design, supervise, and coordinate clinical trials and to assist in data analysis. The efficacy of proton radiation therapy will be compared with that of photon therapy of the very highest technology.

Arteriovenous Malformations↗

PubMed2001

Direct ESR dating of a Pliocene hominin from Swartkrans.

Two fragments of a hominin tooth (Australopithecus robustus) and two bovid teeth from the Hanging Remnant of the Swartkrans Formation were analysed with ESR. Research was complicated by the fact that the samples came from a curated collection and their precise provenance is unknown. The environmental dose rate was reconstructed by a series of in situ gamma spectrometric measurements and elemental analyses of a range of sediment samples. U-series isotopic analyses indicated that each of the teeth had a significantly different uranium uptake history, rendering the assumptive early U-uptake and linear U-uptake models ineffective. ESR and U-series data were combined to calculate open system ages, resulting in a best estimate of 1630+/-160 ka for the Hanging Remnant. An open-system model which provides the maximum age for given U-series and ESR measurements yielded an estimate of about 2100 ka. Two bovid teeth from Member 2, previously estimated to be between 1.0 and 2.0 Ma, yielded age estimates of between about 100 and 200 ka. No known geochemical processes are likely to explain this severe age underestimation. We conclude that these samples are of Middle to Upper Pleistocene age and their presence in Member 2 was either due to reworking or inadequate stratigraphical discrimination of these deposits.

Animals↗

PubMed2004

Radioactive contamination in the upper part of the Techa river: stirring-up of bottom sediments and precipitation of suspended particles. Analysis of the data obtained in 1949-1951.

A hydrodynamic model of the upper part of the Techa river was developed on the basis of the river valley geometry as well as data of hydrological conditions and of the granulometric composition of bottom sediments. The model describes the transport of radioactivity by suspended sediments with different granulometric compositions (clay, silt) in the early 1950s. It includes the stirring-up of bottom sediments and the precipitation of suspended sediments as a function of water discharge rate and water level in the investigated part of the river. The results allow to specify the development of the river system contamination as a result of inflow of suspended sediments contaminated with radionuclides. In the period of liquid radioactive waste (LRW) discharges, the water of the Techa river contained a large fraction of finely dispersed particles of less than 5 micro m diameter. At the site of LRW discharge 80% of the discharged activity was adsorbed to these particles. Depending on the water flow, 40-80% of the suspensions precipitated at the bottom of subsequent sedimentation reservoirs. A total of about 1.6 MCi adsorbed to the suspended particles entered the open hydrographic system of the Techa river. The conclusion that the largest part of the activity was adsorbed on the suspended particles contradicts the assumption in the Techa river dosimetry system, TRDS-2000, that most of the released activity entered the Techa river in soluble form. For a correct reconstruction of the doses received by the Techa river population it is, therefore, essential to consider hydrodynamic models that take into account the transport of radionuclides adsorbed on the suspended particles.

Geologic Sediments↗

PubMed1984

Elective carotid resection for squamous cell carcinoma of the head and neck.

Patients with squamous cell carcinoma adherent to the carotid artery have a very poor prognosis, but some can be salvaged by aggressive surgical resection. Preoperative four vessel arteriography with intracranial views is mandatory to detect coexisting arteriosclerotic disease which may limit collateral perfusion of the ipsilateral cerebral hemisphere. Matas-type occlusive tests performed preoperatively are potentially dangerous and do not provide quantitative information that can be obtained intraoperatively by measuring internal carotid artery stump pressures. If the stump pressure is 50 mm Hg or greater, carotid reconstruction is unnecessary. A stump pressure of less than 50 mm Hg is an indication for reconstruction if the pharynx has not been entered during resection. If mucosal entry will be necessary and the stump pressure is less than 50 mm Hg, resection should not be carried out because of the increased risk of graft complications. Somatosensory evoked potentials predict cerebral tolerance to temporary interruption of flow but do not necessarily predict tolerance to permanent interruption of flow. Autogenous vein is the graft material of choice for reconstruction. In those patients not reconstructed, low-dose heparinization started before operation and continued for 10 days may lessen the likelihood of delayed stroke from embolization of a propagated thrombus in the carotid stump.

Adult↗

PubMed2005

The 3rd international intercomparison on EPR tooth dosimetry: Part 1, general analysis.

The objective of the 3rd International Intercomparison on Electron Paramagnetic Resonance (EPR) Tooth Dosimetry was the evaluation of laboratories performing tooth enamel dosimetry below 300 mGy. Participants had to reconstruct the absorbed dose in tooth enamel from 11 molars, which were cut into two halves. One half of each tooth was irradiated in a 60Co beam to doses in the ranges of 30-100 mGy (5 samples), 100-300 mGy (5 samples), and 300-900 mGy (1 sample). Fourteen international laboratories participated in this intercomparison programme. A first analysis of the results and an overview of the essential features of methods applied in different laboratories are presented. The relative standard deviation of results of all methods was better than 27% for applied doses in the range of 79-704 mGy. In the analysis of the unirradiated tooth halves 8% of the samples were identified as outliers with additional absorbed dose above background dose.

Benchmarking↗

PubMed2004

Probabilistic risk assessment of abalone Haliotis diversicolor supertexta exposed to waterborne zinc.

This paper describes a risk assessment approach that integrates predicted tissue concentrations of zinc (Zn) with a concentration-response relationship and leads to predictions of survival risk for pond abalone Haliotis diversicolor supertexta as well as to the uncertainties associated with these predictions. The models implemented include a probabilistic bioaccumulation model, which linking biokinetic and consumer-resource models, accounts for Zn exposure profile and a modified Hill model for reconstructing a dose-response profile for abalone exposed to waterborne Zn. The growth risk is assessed by hazard quotients characterized by measured water level and chronic no-observed effect concentration. Our risk analyses for H. diversicolor supertexta reared near Toucheng, Kouhu, and Anping, respectively, in north, central, and south Taiwan region indicate a relatively low likelihood that survival is being affected by waterborne Zn. Expected risks of mortality for abalone were estimated as 0.46 (Toucheng), 0.36 (Kouhu), and 0.29 (Anping). The predicted 90th-percentiles of hazard quotient for potential growth risk were estimated as 1.94 (Toucheng), 0.47 (Kouhu), and 0.51 (Anping). These findings indicate that waterborne Zn exposure poses no significant risk to pond abalone in Kouhu and Anping, yet a relative high growth risk in Toucheng is alarming. Because of a scarcity of toxicity and exposure data, the probabilistic risk assessment was based on very conservative assumptions.

Animals↗

PubMed2001

Left sided vocal cord paralysis: a newly recognized late complication of mediastinal irradiation.

BACKGROUND AND PURPOSE: To evaluate the incidence of vocal cord paralysis in a group of breast cancer patients treated with post operative radiation therapy after radical mastectomy. MATERIALS AND METHODS: A group of 150 patients operated with total mastectomy and axillary clearance received, in 1963-1965, post-operative radiotherapy to the parasternal, axillary and supraclavicular lymph node regions. The cohort has now been followed up to 34 years. RESULTS: Eleven of the 12 vocal cord paralyses were left sided, although the breast cancer was almost equally distributed as left- and right-sided (55 vs. 45%). The symptoms did not appear until 2-25 years after irradiation. Series 1 (treated with (60)Co photons) developed 5% recurrent nerve paralysis (RNP) after a median time of 19.0 years compared with 10% and a much earlier appearance (3.5 years) for series 2 (treated with both (60)Co photons and electrons). A reconstruction of the dose plan shows that an unintentional overlap of the fields resulted in hotspots in the tracheo-oesophageal groove, where parts of the tissue received 120-130% of the prescribed dose. CONCLUSIONS: A left-sided vocal cord paralysis of patients treated with mediastinal radiotherapy might not indicate only tumour recurrence but also mediastinal fibrosis. Small differences in patient positioning cannot be excluded as the cause of the difference in the two series. We postulate that other more subtle damage to the vagus nerve may occur without being recognized as late radiation injury.

Adult↗