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Dose Calculation (dose + calculation)
Selected AbstractsExamples for the importance of radiophysical measurements in clinical phototherapyJOURNAL DER DEUTSCHEN DERMATOLOGISCHEN GESELLSCHAFT, Issue 5 2007Lars Alexander Schneider Summary Background: Optimal UV therapy requires regular surveillance of the variables that influence therapeutic success. In daily practice, phototherapy equipment is often operated with an attitude of "autocontrol." This implies that thorough control measurements of the emission spectra and calibration of UV fluences are not routinely performed. For both quality control and patient safety, it is essential to regularly check whether a UV source is providing the right target spectrum with the correct dose to the skin. Methods: We have exemplarily taken three UV sources currently used in clinical practice and performed radiophysical measurements, i. e. determined emission spectra, radiation output and correctness of dose calculation. Results: All three sources revealed either a largely inhomogeneous distribution pattern of radiation intensity, variation of radiation intensity over time or insufficient filtering of the UV lamp emission spectrum. Furthermore the dose calculation procedures had to be revised because of significant differences between the estimated and the administered UV doses. Conclusions: Radiophysical measurement of all UV-equipment in clinical use is a simple and effective way to improve the safety and reliability of phototherapy. Such measurements help to uncover technical flaws in radiation sources and prevent unnecessary side effects and UV exposure risks for the patient. [source] Economic Evaluation of Oseltamivir Phosphate for Postexposure Prophylaxis of Influenza in Long-Term Care FacilitiesJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 3 2005Nancy A. Risebrough MPhil Candidate Objectives: To compare the cost-effectiveness of oseltamivir postexposure prophylaxis during influenza A outbreaks with that of amantadine postexposure prophylaxis or no postexposure prophylaxis in long-term care facilities (LTCFs). Design: Cost-effectiveness analysis based on decision analytic model from a government-payer perspective. Setting: A Canadian LTCF, with high staff vaccination, at the beginning of influenza season. Participants: Elderly, influenza-vaccinated patients living in a Canadian LTCF. Measurements: Incremental costs (or savings) per influenza-like illness case avoided compared with usual care. Results: From a government-payer perspective, this analysis showed that oseltamivir was a dominant strategy because it was associated with the fewest influenza-like illness cases, with cost savings of $1,249 per 100 patients in 2001 Canadian dollars compared with amantadine and $3,357 per 100 patients compared with no prophylaxis. Costs for amantadine dose calculation and hospitalization for adverse events contributed to amantadine being a more-expensive prophylaxis strategy than oseltamivir. Both prophylaxis strategies were more cost-effective than no prophylaxis. Conclusion: Despite high influenza vaccination rates, influenza outbreaks continue to emerge in LTCFs, necessitating cost-effective measures to further limit the spread of influenza and related complications. Although amantadine has a lower acquisition cost than oseltamivir, it is associated with more adverse events, lower efficacy, and individualized dosing requirements, leading to higher overall costs and more influenza-like illness cases than oseltamivir. Therefore the use of oseltamivir postexposure prophylaxis is more cost-effective than the current standard of care with amantadine prophylaxis or no prophylaxis. [source] Clinical care and technical recommendations for 90yttrium microsphere treatment of liver cancerJOURNAL OF MEDICAL IMAGING AND RADIATION ONCOLOGY, Issue 3 2010S-C Wang Summary Selective internal radiation therapy (SIRT) with 90yttrium microspheres is a relatively new clinical modality for treating non-resectable malignant liver tumours. This interventional radiology technique employs percutaneous microcatheterisation of the hepatic arterial vasculature to selectively deliver radioembolic microspheres into neoplastic tissue. SIRT results in measurable tumour responses or delayed disease progression in the majority of eligible patients with hepatocellular carcinoma or hepatic metastases arising from colorectal cancer. It has also been successfully used as palliative therapy for non-colorectal malignancies metastatic to the liver. Although most adverse events are mild and transient, SIRT also carries some risks for serious and , rarely , fatal outcomes. In particular, entry of microspheres into non-target vessels may result in radiation-induced tissue damage, such as severe gastric ulceration or radiation cholecystitis. Radiation-induced liver disease poses another significant risk. By careful case selection, considered dose calculation and meticulous angiographic technique, it is possible to minimise the incidence of such complications to less than 10% of all treatments. As the number of physicians employing SIRT expands, there is an increasing need to consolidate clinical experience and expertise to optimise patient outcomes. Authored by a panel of clinicians experienced in treating liver tumours via SIRT, this paper collates experience in vessel mapping, embolisation, dosimetry, microsphere delivery and minimisation of non-target delivery. In addition to these clinical recommendations, the authors propose institutional criteria for introducing SIRT at new centres and for incorporating the technique into multidisciplinary care plans for patients with hepatic neoplasms. [source] Opioid Rotation in the Management of Chronic Pain: Where Is the Evidence?PAIN PRACTICE, Issue 2 2010K.C.P. Vissers MD Abstract The management of chronic pain remains a challenge because of its complexity and unpredictable response to pharmacological treatment. In addition, accurate pain management may be hindered by the prejudice of physicians and patients that strong opioids, classified as step 3 medications in the World Health Organization ladder for cancer pain management, are reserved for the end stage of life. Recent information indicates the potential value of strong opioids in the treatment of chronic nonmalignant pain. There are, up until now, insufficient data to provide indications about which opioid to use to initiate treatment or the dose to be used for any specific pain syndrome. The strong inter-patient variability in opioid receptor response and in the pharmacokinetic and pharmacodynamic behavior of strong opioids justifies an individual selection of the appropriate opioid and stepwise dose titration. Clinical experience shows that switching from one opioid to another may optimize pain control while maintaining an acceptable side effect profile or even improving the side effects. This treatment strategy, described as opioid rotation or switch, requires a dose calculation for the newly started opioid. Currently, conversion tables and equianalgesic doses are available. However, those recommendations are often based on data derived from studies designed to evaluate acute pain relief, and sometimes on single dose studies, which reduces this information to the level of an indication. In daily practice, the clinician needs to titrate the optimal dose during the opioid rotation from a reduced calculated dose, based on the clinical response of the patient. Further research and studies are needed to optimize the equianalgesic dosing tables. [source] Point-of-care reversal treatment in phenprocoumon-related intracerebral hemorrhageANNALS OF NEUROLOGY, Issue 6 2010Timolaos Rizos MD Objective Rapid reversal of the anticoagulatory effect of vitamin K antagonists represents the primary emergency treatment for oral anticoagulant-related intracerebral hemorrhage (OAC-ICH). Predicting the amount of prothrombin complex concentrate (PCC) needed to reverse OAC in individual patients is difficult, and repeated international normalized ratio (INR) measurements in central laboratories (CLs) are time-consuming. Accuracy and effectiveness of point-of-care INR coagulometers (POCs) for INR reversal in OAC-ICH have not been evaluated. Methods In phase 1, the agreement of emergency POC and CL INR measurements was determined. In phase 2, stepwise OAC reversal was performed with PCC using a predetermined dosing schedule. Concordance of POC and CL INR measurements during reversal and time gain due to POC were determined. Results In phase 1 (n = 165), Bland-Altman analysis showed close agreement between POCs and CLs (mean INR deviation 0.04). In phase 2 (n = 26), POCs caused a median initial net time gain of 24 minutes for the start of treatment with PCC. Median time for POC-documented complete OAC reversal was 28 minutes, compared with 120 minutes for CLs. Bland-Altman analysis between POCs and CLs revealed a mean INR deviation of 0.13 during stepwise PCC administration. POCs tended to slightly overestimate the INR, especially at higher INR levels. Remarkably, POC-guided reversal led to a median reduction of 30.5% of PCC dose compared with the a priori dose calculation. Hematomas enlarged in 20% of patients. Interpretation POC INR monitoring is a fast, effective, and economic means of PCC dose-titration in OAC-ICH. Larger studies examining the clinical efficacy of this procedure are warranted. ANN NEUROL 2010;67:788,793 [source] Know your dose: RADDOSEACTA CRYSTALLOGRAPHICA SECTION D, Issue 4 2010Karthik S. Paithankar The program RADDOSE is widely used to compute the dose absorbed by a macromolecular crystal during an X-ray diffraction experiment. A number of factors affect the absorbed dose, including the incident X-ray flux density, the photon energy and the composition of the macromolecule and of the buffer in the crystal. An experimental dose limit for macromolecular crystallography (MX) of 30,MGy at 100,K has been reported, beyond which the biological information obtained may be compromised. Thus, for the planning of an optimized diffraction experiment the estimation of dose has become an additional tool. A number of approximations were made in the original version of RADDOSE. Recently, the code has been modified in order to take into account fluorescent X-ray escape from the crystal (version 2) and the inclusion of incoherent (Compton) scattering into the dose calculation is now reported (version 3). The Compton cross-section, although negligible at the energies currently commonly used in MX, should be considered in dose calculations for incident energies above 20,keV. Calculations using version 3 of RADDOSE reinforce previous studies that predict a reduction in the absorbed dose when data are collected at higher energies compared with data collected at 12.4,keV. Hence, a longer irradiation lifetime for the sample can be achieved at these higher energies but this is at the cost of lower diffraction intensities. The parameter `diffraction-dose efficiency', which is the diffracted intensity per absorbed dose, is revisited in an attempt to investigate the benefits and pitfalls of data collection using higher and lower energy radiation, particularly for thin crystals. [source] Total imprecision of exposure biomarkers: implications for calculating exposure limitsAMERICAN JOURNAL OF INDUSTRIAL MEDICINE, Issue 10 2007Philippe Grandjean MD Abstract Background Assessment of the imprecision of exposure biomarkers usually focuses on laboratory performance only. Unrecognized imprecision leads to underestimation of the true toxicity of the exposure. We have assessed the total imprecision of exposure biomarkers and the implications for calculation of exposure limits. Methods In a birth cohort study, mercury concentrations in cord blood, cord tissue, and maternal hair were used as biomarkers of prenatal methylmercury exposure. We determined their mutual correlations and their associations with the child's neurobehavioral outcome variables at age 7 years. With at least three exposure parameters available, factor analysis and structural equation modeling could be applied to determine the total imprecision of each biomarker. The estimated imprecision was then applied to adjust benchmark dose calculations and the derived exposure limits. Results The exposure biomarkers correlated well with one another, but the cord blood mercury concentration showed the best associations with neurobehavioral deficits. Factor analysis and structural equation models showed a total imprecision of the cord-blood parameter of 25,30%, and almost twice as much for maternal hair. These imprecisions led to inflated benchmark dose levels. Adjusted calculations resulted in an exposure limit 50% below the level recommended by the U.S. National Research Council. Conclusions The biomarker imprecisions of 25,50% much exceeded normal laboratory variability. Such imprecision causes underestimation of dose-related toxicity and therefore must be considered in the data analysis and when deriving exposure limits. Future studies should ideally include at least three exposure parameters to allow independent assessment of total imprecision. Am. J. Ind. Med. 50:712,719, 2007. © 2007 Wiley-Liss, Inc. [source] Know your dose: RADDOSEACTA CRYSTALLOGRAPHICA SECTION D, Issue 4 2010Karthik S. Paithankar The program RADDOSE is widely used to compute the dose absorbed by a macromolecular crystal during an X-ray diffraction experiment. A number of factors affect the absorbed dose, including the incident X-ray flux density, the photon energy and the composition of the macromolecule and of the buffer in the crystal. An experimental dose limit for macromolecular crystallography (MX) of 30,MGy at 100,K has been reported, beyond which the biological information obtained may be compromised. Thus, for the planning of an optimized diffraction experiment the estimation of dose has become an additional tool. A number of approximations were made in the original version of RADDOSE. Recently, the code has been modified in order to take into account fluorescent X-ray escape from the crystal (version 2) and the inclusion of incoherent (Compton) scattering into the dose calculation is now reported (version 3). The Compton cross-section, although negligible at the energies currently commonly used in MX, should be considered in dose calculations for incident energies above 20,keV. Calculations using version 3 of RADDOSE reinforce previous studies that predict a reduction in the absorbed dose when data are collected at higher energies compared with data collected at 12.4,keV. Hence, a longer irradiation lifetime for the sample can be achieved at these higher energies but this is at the cost of lower diffraction intensities. The parameter `diffraction-dose efficiency', which is the diffracted intensity per absorbed dose, is revisited in an attempt to investigate the benefits and pitfalls of data collection using higher and lower energy radiation, particularly for thin crystals. [source] | ||||||||||