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Medizinische Klinik, Intensivmedizin... Jun 2019Essential for drug dose adjustment is the glomerular filtration rate (GFR) not the serum creatinine level. In acute disease, a loading dose must be given that usually... (Review)
Review
Essential for drug dose adjustment is the glomerular filtration rate (GFR) not the serum creatinine level. In acute disease, a loading dose must be given that usually corresponds to the normal dose. The eliminated half-life is used to estimate the administration interval. For anti-infective drugs with a concentration-dependent effect, the target is the high peak such as for daptomycin, linezolide, and colistin. For anti-infective drugs with a time-dependent effect, the target is the high trough such as for piperacillin, meropenem and vancomycin. Such drugs with a time-dependent action should best be administered by infusion not by bolus dosing. With continuous renal replacement therapy (CRRT), the total filtration rate corresponds to a GFR of 30-50 ml/min and many antibiotics will not need a dose reduction on CRRT. After intermittent hemodialysis, a new loading dose should be given to ascertain sufficiently high concentrations in the interval until the next dose or next dialysis.
Topics: Anti-Bacterial Agents; Critical Illness; Glomerular Filtration Rate; Humans; Kidney Diseases; Meropenem; Pharmacokinetics; Piperacillin; Vancomycin
PubMed: 29980815
DOI: 10.1007/s00063-018-0455-5 -
World Journal of Urology Jan 2023To identify the relationship between fluoroscopy pulse rate and absorbed radiation dose. We compared absorbed radiation dose with common proxy measurements such as...
PURPOSE
To identify the relationship between fluoroscopy pulse rate and absorbed radiation dose. We compared absorbed radiation dose with common proxy measurements such as fluoroscopy time and C-arm reported dose.
METHODS
Using a simulated patient model, 60 s fluoroscopy exposures were performed using pulse rates of 30, 8, 4, 2, and 1 pulse(s) per second. Each experiment was performed with both standard and low-dose settings using a GE OEC 9800 plus C-arm. Landauer nanoDot™ OSL dosimeters were used to measure the absorbed radiation dose.
RESULTS
Fluoroscopy pulse rate and absorbed radiation dose demonstrated a linear correlation for both standard (R = 0.995, p < 0.001) and low-dose (R = 0.998, p < 0.001) settings. For any given pulse rate, using the low-dose setting reduced absorbed radiation dose by 58 ± 2.8%. Fluoroscopy time demonstrated a linear relationship with absorbed radiation dose for both standard (R = 0.996, p < 0.001) and low-dose (R = 0.991, p < 0.001) settings, but did not change with use of the low-dose setting. C-arm reported radiation dose correlated linearly with absorbed dose (R = 0.999) but consistently under-estimated measured values by an average of 49 ± 3.5%. Using a combination of 1 pulse-per-second and low-dose fluoroscopy, absorbed dose was reduced by 97.7 ± 0.1% compared to standard dose and 30 pulse-per-second settings.
CONCLUSION
Absorbed radiation dose decreases linearly with fluoroscopy pulse rate during equivalent exposure times. Adjusting fluoroscopy pulse rate and utilizing low-dose settings significantly reduces overall absorbed radiation exposure by up to 98%.
Topics: Humans; Radiation Dosage; Heart Rate; Radiation Exposure; Fluoroscopy; Patients
PubMed: 36525105
DOI: 10.1007/s00345-022-04238-2 -
Radiation Protection Dosimetry Oct 2023In this study, in some neighborhoods in Kahramanmaraş province of Turkey, indoors and outdoors direct gamma dose rate measurements have been done. All of the gamma dose...
In this study, in some neighborhoods in Kahramanmaraş province of Turkey, indoors and outdoors direct gamma dose rate measurements have been done. All of the gamma dose rate measurements have been made at ground level and at the height of 1 m from the ground. The median values of the gamma dose rates on the ground and 1 m above the ground indoors are 70.34 ± 7.74 and 49.53 ± 5.39 nGy h-1, respectively. Outdoor measurements have been carried out on both soil and asphalt floors. The average values of gamma dose rate on the ground and at a height of 1 m outdoors (soil floor) are 68.16 ± 7.49 and 53.50 ± 5.88 nGy h-1, respectively. The mean values of gamma dose rate on the ground and 1 m above the ground outdoors (asphalt floor) are 61.63 ± 6.77 and 48.69 ± 5.35 nGy h-1, respectively. Indoor and outdoor average gamma dose rates are below the mean world. In addition, using the measured gamma dose rate values, annual effective dose equivalent (AEDE) and excess lifetime cancer risk (ELCR) for adults have been calculated. The total AEDE and ELCR (on soil floors and indoors at 1 m above ground level) are 0.31 ± 0.03 mSv y-1 and 1.08 ± 0.10 × 10-3, respectively. The total AEDE and ELCR (on asphalt floors and indoors at 1 m above ground level) are 0.30 ± 0.03 mSv y-1 and 1.06 ± 0.10 × 10-3, respectively. The AEDE and ELCR for adults living in the neighborhoods within the scope of the study in Kahramanmaraş city center within 1 y are lower than the average world.
PubMed: 37587689
DOI: 10.1093/rpd/ncad223 -
World Journal of Plastic Surgery Jan 2021Radiotherapy as an adjuvant therapy to surgical resection has shown variable rates of recurrence treating earlobe keloids. The purpose of this study was to describe our...
BACKGROUND
Radiotherapy as an adjuvant therapy to surgical resection has shown variable rates of recurrence treating earlobe keloids. The purpose of this study was to describe our experience with surgical excision followed by high-dose-rate brachytherapy and present our outcomes after 24 months of follow-up.
METHODS
Retrospective chart of 14 patients with 14 earlobe keloids treated with surgical excision followed by high-dose-rate brachytherapy, between January 2015 and May 2016 were enrolled. Database included demographics, Fitzpatrick skin type, laterality, lesion size, and follow-up visits information. Outcomes were assessed in terms of keloid recurrence rates, complications, and patient subjective aesthetical result satisfaction after 24 months of follow-up.
RESULTS
All procedures were completed without complications. Three patients experienced keloid recurrence after 6 (14.28%) and 12 months (7.14%). Three patients experienced mild signs of self-limited post-radiation dermatitis. Self-assessment of aesthetical result was considered "very good" in 71.43% of patients.
CONCLUSION
Surgical excision followed by high-dose-rate brachytherapy is secure and effective to treat earlobe keloids, and can be considered a first line combined treatment. Larger clinical trials comparing different irradiation protocols are still needed.
PubMed: 33833958
DOI: 10.29252/wjps.10.1.78 -
Medical Physics Dec 2020FLASH radiotherapy (RT) can potentially reduce normal tissue toxicity while preserving tumoricidal effectiveness to improve the therapeutic ratio. The key of FLASH for...
PURPOSE
FLASH radiotherapy (RT) can potentially reduce normal tissue toxicity while preserving tumoricidal effectiveness to improve the therapeutic ratio. The key of FLASH for sparing normal tissues is to irradiate tissues with an ultra-high dose rate (i.e., ≥40 Gy/s), for which proton RT can be used. However, currently available treatment plan optimization method only optimizes the dose distribution and does not directly optimize the dose rate. The contribution of this work to FLASH proton RT is the development of a novel treatment optimization method, that is, simultaneous dose and dose rate optimization (SDDRO), to optimize tissue-receiving dose rate distribution as well as dose distribution.
METHODS
Distinguished from existing methods, SDDRO accounts for dose rate constraint and optimizes dose rate distribution. In terms of mathematical formulation, SDDRO is a constrained optimization problem with dose-volume constraint on dose distribution, minimum dose rate constraint on dose-averaged tissue-receiving dose rates, minimum monitor unit constraint on spot weight, and maximum intensity constraint on beam intensity. In terms of optimization algorithm, SDDRO is solved by iterative convex relaxation and alternating direction method of multipliers. SDDRO algorithms are presented for both scenarios with either constant or variable beam intensity.
RESULTS
SDDRO was compared with intensity modulated proton therapy (IMPT) (dose optimization alone, and no dose rate optimization) using three lung cases. SDDRO substantially improved the dose rate distribution compared to IMPT, for example, increasing of the region-of-interest (ROI) volume (ROI = CTV_10mm: the ring sandwiched by 10 mm outer and inner expansion of CTV boundary) receiving at least 40 Gy/s from ~30-50% to at least 98%, and the lung volume receiving at least 40 Gy/s from ~30-40% to ~70-90%. Moreover, both dose and dose rate distributions from SDDRO were further considerably improved via the combined use of hypofractionation and multiple beams.
CONCLUSIONS
We have developed a joint dose and dose rate optimization method for FLASH proton RT, namely SDDRO, which is first-of-its-kind to the best of our knowledge. The results suggest that (a) SDDRO can substantially improve the FLASH-dose rate coverage (e.g., in terms of dose rate volume histogram) compared to IMPT for the purpose of normal tissue sparing while preserving the dose distribution and (b) the combination of hypofractionation and multiple beams can further considerably improve the SDDRO plan quality in terms of both dose and dose rate distribution.
Topics: Algorithms; Proton Therapy; Radiotherapy Dosage; Radiotherapy Planning, Computer-Assisted; Radiotherapy, Intensity-Modulated
PubMed: 33068294
DOI: 10.1002/mp.14531 -
Translational Andrology and Urology Jun 2018High dose-rate (HDR) brachytherapy involves delivery of a high dose of radiation to the cancer with great sparing of surrounding organs at risk. Prostate cancer is... (Review)
Review
High dose-rate (HDR) brachytherapy involves delivery of a high dose of radiation to the cancer with great sparing of surrounding organs at risk. Prostate cancer is thought to be particularly sensitive to radiation delivered at high dose-rate or at high dose per fraction. The rapid delivery and high conformality of dose results in lower toxicity than that seen with low dose-rate (LDR) implants. HDR combined with external beam radiotherapy results in higher cancer control rate than external beam only, and should be offered to eligible high and intermediate risk patients. While a variety of dose and fractionations have been used, a single 15 Gy HDR combined with 40-50 Gy external beam radiotherapy results in a disease-free survival of over 90% for intermediate risk and 80% for high risk. HDR monotherapy in two or more fractions (e.g., 27 Gy in 2 fractions or 34.5 Gy in 3) is emerging as a viable alternative to LDR brachytherapy for low and low-intermediate risk patients, and has less toxicity. The role of single fraction monotherapy to a dose of 19-20 Gy is evolving, with some conflicting data to date. HDR should also be considered as a salvage approach for recurrent disease following previous external beam radiotherapy. A particular advantage of HDR in this setting is the ease of delivering focal treatments, which combined with modern imaging allows focal dose escalation with minimal toxicity. Trans-rectal ultrasound (TRUS) based planning is replacing CT-based planning as the technique of choice as it minimizes or eliminates the need to move the patient between insertion, planning and treatment delivery, thus ensuring high accuracy and reproducibility of treatment.
PubMed: 30050796
DOI: 10.21037/tau.2017.12.08 -
Postepy Dermatologii I Alergologii Oct 2015The incidence of skin cancer worldwide is constantly growing and it is the most frequently diagnosed tumor. Brachytherapy (BT) in particular localizations is a valuable... (Review)
Review
The incidence of skin cancer worldwide is constantly growing and it is the most frequently diagnosed tumor. Brachytherapy (BT) in particular localizations is a valuable tool of the exact radiation depot inside the tumor mass. In localizations such as the face, skull skin and inoperable tumors, relapses after surgery, radiotherapy are usually not suitable for primary or secondary invasive treatment. Brachytherapy is a safe procedure for organs at risk according to rapid fall of a dose outside the axis of the applicator with satisfactory dose localization inside the target. The complications rate is acceptable and treatment costs are low. In some tumors (great skin lesions in the scalp, near eyes or on the nose) BT allows for a great dose reduction in surrounding healthy tissues. Brachytherapy provides minimal dose delivery to surrounding healthy tissue, thus enabling good functional and cosmetic results. Treatment is possible almost in all cases on an outpatient basis.
PubMed: 26759545
DOI: 10.5114/pdia.2015.54746 -
Medical Physics Mar 2022Compared to CONV-RT (with conventional dose rate), FLASH-RT (with ultra-high dose rate) can provide biological dose sparing for organs-at-risk (OARs) via the so-called...
PURPOSE
Compared to CONV-RT (with conventional dose rate), FLASH-RT (with ultra-high dose rate) can provide biological dose sparing for organs-at-risk (OARs) via the so-called FLASH effect, in addition to physical dose sparing. However, the FLASH effect only occurs, when both dose and dose rate meet certain minimum thresholds. This work will develop a simultaneous dose and dose rate optimization (SDDRO) method accounting for both FLASH dose and dose rate constraints during treatment planning for pencil-beam-scanning proton therapy.
METHODS
SDDRO optimizes the FLASH effect (specific to FLASH-RT) as well as the dose distribution (similar to CONV-RT). The nonlinear dose rate constraint is linearized, and the reformulated optimization problem is efficiently solved via iterative convex relaxation powered by alternating direction method of multipliers. To resolve and quantify the generic tradeoff of FLASH-RT between FLASH and dose optimization, we propose the use of FLASH effective dose based on dose modifying factor (DMF) owing to the FLASH effect.
RESULTS
FLASH-RT via transmission beams (TB) (IMPT-TB or SDDRO) and CONV-RT via Bragg peaks (BP) (IMPT-BP) were evaluated for clinical prostate, lung, head-and-neck (HN), and brain cases. Despite the use of TB, which is generally suboptimal to BP for normal tissue sparing, FLASH-RT via SDDRO considerably reduced FLASH effective dose for high-dose OAR adjacent to the target. For example, in the lung SBRT case, the max esophageal dose constraint 27 Gy was only met by SDDRO (24.8 Gy), compared to IMPT-BP (35.3 Gy) or IMPT-TB (36.6 Gy); in the brain SRS case, the brain constraint V12Gy≤15cc was also only met by SDDRO (13.7cc), compared to IMPT-BP (43.9cc) or IMPT-TB (18.4cc). In addition, SDDRO substantially improved the FLASH coverage from IMPT-TB, e.g., an increase from 37.2% to 67.1% for lung, from 39.1% to 58.3% for prostate, from 65.4% to 82.1% for HN, from 50.8% to 73.3% for the brain.
CONCLUSIONS
Both FLASH dose and dose rate constraints are incorporated into SDDRO for FLASH-RT that jointly optimizes the FLASH effect and physical dose distribution. FLASH effective dose via FLASH DMF is introduced to reconcile the tradeoff between physical dose sparing and FLASH sparing, and quantify the net effective gain from CONV-RT to FLASH-RT.
Topics: Humans; Male; Organs at Risk; Proton Therapy; Radiotherapy Dosage; Radiotherapy Planning, Computer-Assisted; Radiotherapy, Intensity-Modulated
PubMed: 34800301
DOI: 10.1002/mp.15356 -
Cancer Radiotherapie : Journal de La... Oct 2014Cervical cancer, although less common in industrialized countries, is the fourth most common cancer affecting women worldwide and the fourth leading cause of cancer... (Review)
Review
Cervical cancer, although less common in industrialized countries, is the fourth most common cancer affecting women worldwide and the fourth leading cause of cancer death. In developing countries, these cancers are often discovered at a later stage in the form of locally advanced tumour with a poor prognosis. Depending on the stage of the disease, treatment is mainly based on a chemoradiotherapy followed by uterovaginal brachytherapy ending by a potential remaining tumour surgery or in principle for some teams. The role of irradiation is crucial to ensure a better local control. It has been shown that the more the delivered dose is important, the better the local results are. In order to preserve the maximum of organs at risk and to allow this dose escalation, brachytherapy (intracavitary and/or interstitial) has been progressively introduced. Its evolution and its progressive improvement have led to the development of high dose rate brachytherapy, the advantages of which are especially based on the possibility of outpatient treatment while maintaining the effectiveness of other brachytherapy forms (i.e., low dose rate or pulsed dose rate). Numerous innovations have also been completed in the field of imaging, leading to a progress in treatment planning systems by switching from two-dimensional form to a three-dimensional one. Image-guided brachytherapy allows more precise target volume delineation as well as an optimized dosimetry permitting a better coverage of target volumes.
Topics: Ambulatory Care; Brachytherapy; Chemoradiotherapy; Combined Modality Therapy; Dose Fractionation, Radiation; Dose-Response Relationship, Radiation; Equipment Design; Female; Humans; Neoadjuvant Therapy; Organs at Risk; Practice Guidelines as Topic; Radiation Injuries; Radiation Protection; Radioisotopes; Radiotherapy Dosage; Radiotherapy, Image-Guided; Uterine Cervical Neoplasms
PubMed: 25151650
DOI: 10.1016/j.canrad.2014.06.008 -
International Journal of Molecular... Jun 2022Accurate knowledge of the relative biological effectiveness (RBE) and its dependencies is crucial to support modern ion beam therapy and its further development....
Accurate knowledge of the relative biological effectiveness (RBE) and its dependencies is crucial to support modern ion beam therapy and its further development. However, the influence of different dose rates of the reference radiation and ion beam are rarely considered. The ion beam RBE-model within our "UNIfied and VERSatile bio response Engine" (UNIVERSE) is extended by including DNA damage repair kinetics to investigate the impact of dose-rate effects on the predicted RBE. It was found that dose-rate effects increase with dose and biological effects saturate at high dose-rates, which is consistent with data- and model-based studies in the literature. In a comparison with RBE measurements from a high dose in-vivo study, the predictions of the presented modification were found to be improved in comparison to the previous version of UNIVERSE and existing clinical approaches that disregard dose-rate effects. Consequently, DNA repair kinetics and the different dose rates applied by the reference and ion beams might need to be considered in biophysical models to accurately predict the RBE. Additionally, this study marks an important step in the further development of UNIVERSE, extending its capabilities in giving theoretical guidance to support progress in ion beam therapy.
Topics: DNA Repair; Kinetics; Relative Biological Effectiveness
PubMed: 35682947
DOI: 10.3390/ijms23116268