Impact of Fraction Size, Dose-Rate, Temperature and Overall Treatment Time on Tumor Cell Response

2016 ◽  
pp. 67-76
Keyword(s):  
Tumor Cell ◽  
Dose Rate ◽  
Cell Response ◽  
Treatment Time ◽  
Overall Treatment Time ◽  
Fraction Size

scholarly journals Estimation of cell response in fractionation radiotherapy using different methods derived from linear quadratic model

2015 ◽  
Vol 49 (4) ◽  
pp. 347-356 ◽  
Author(s):  
Safoora Nikzad ◽  
Bijan Hashemi ◽  
Golshan Mahmoudi ◽  
Milad Baradaran-Ghahfarokhi
Keyword(s):  
Cell Response ◽  
Treatment Time ◽  
Theoretical Models ◽  
Accurate Method ◽  
Quadratic Model ◽  
Breast Adenocarcinoma ◽  
Linear Quadratic ◽  
Overall Treatment Time ◽  
Simple Method ◽  
Theoretical Methods

Abstract Background. The aim of this study was to use various theoretical methods derived from the Linear Quadratic (LQ) model to calculate the effects of number of subfractions, time intervals between subfractions, dose per subfraction, and overall fraction time on the cells’ survival. Comparison of the results with experimental outcomes of melanoma and breast adenocarcinoma cells was also performed. Finally, the best matched method with experimental outcomes is introduced as the most accurate method in predicting the cell response. Materials and methods. The most widely used theoretical methods in the literature, presented by Keall et al., Brenner, and Mu et al., were used to calculate the cells’ survival following radiotherapy with different treatment schemes. The overall treatment times were ranged from 15 to 240 minutes. To investigate the effects of number of subfractions and dose per subfraction, the cells’ survival after different treatment delivery scenarios were calculated through fixed overall treatment times of 30, 60 and 240 minutes. The experimental tests were done for dose of 4 Gy. The results were compared with those of the theoretical outcomes. Results. The most affective parameter on the cells’ survival was the overall treatment time. However, the number of subfractions per fractions was another effecting parameter in the theoretical models. This parameter showed no significant effect on the cells’ survival in experimental schemes. The variations in number of subfractions per each fraction showed different results on the cells’ survival, calculated by Keall et al. and Brenner methods (P<0.05). Conclusions. Mu et al. method can predict the cells’ survival following fractionation radiotherapy more accurately than the other models. Using Mu et al. method, as an accurate and simple method to predict the cell response after fractionation radiotherapy, is suggested for clinical applications.

Fractionated high-dose-rate brachytherapy in primary carcinoma of the nasopharynx.

1998 ◽  
Vol 16 (6) ◽  
pp. 2213-2220 ◽  
Author(s):  
P C Levendag ◽  
P I Schmitz ◽  
P P Jansen ◽  
W M Eijkenboom ◽  
A G Visser ◽  
...  
Keyword(s):  
Dose Rate ◽  
Treatment Time ◽  
Univariate Analysis ◽  
High Dose Rate ◽  
Local Failure ◽  
Dose Effect ◽  
High Dose ◽  
Outpatient Basis ◽  
Overall Treatment Time ◽  
Prognostic Group

PURPOSE A growing body of data suggests that local control in nasopharyngeal cancer (NPC) is related to the radiation dose administered. We conducted a single-institution study of high-dose radiotherapy (RT), which incorporated high-dose-rate (HDR) brachytherapy (BT). These results were analyzed together with data obtained from controls who did not receive BT. PATIENTS AND METHODS The BT group comprised 42 consecutive patients of whom 29 patients were staged according to the tumor, node, metastasis system as T1 through 3, 13 patients were T4, and 34 patients were N+ disease. BT was administered on an outpatient basis by means of a specially designed flexible nasopharyngeal applicator, and the dose distributions were optimized. Treatment for T1 through 3 tumors comprised 60 Gy of external-beam radiotherapy (ERT) followed by six fractions of 3 Gy BT (two fractions per day). Patients with parapharyngeal tumor extension and/or T4 tumors received 70 Gy ERT and four fractions of 3 Gy BT. The no-BT group consisted of all patients treated from 1965 to 1991 (n = 109), of whom 82 patients had stages T1 through 3, 27 patients had T4, and 80 patients had N+ disease. Multivariate Cox proportional hazards analyses were performed by using the end points time to local failure (TTLF), time to distant failure (TTDF), disease-free survival (DFS), cause-specific survival (CSS), and the prognostic factors age, tumor stage, node stage, and grade. Because the overall treatment time varied substantially in the no-BT group, the dependence of local failure (LF) on the physical dose as well as the biologic effective dose (BED) corrected for the overall treatment time (OTT) (BEDcor10) was studied. RESULTS The BT group had a superior 3-year local relapse-free rate (86% v 60%; univariate analysis, P = .004). Multivariate analysis showed hazards ratios for BT versus no-BT of 0.24 for TTLF (P = .003), 0.35 for TTDF (P = .038), 0.31 for DFS (P < .001), and 0.44 for CSS (P = .01). The best prognostic group consisted of patients with T1 through 3, N0 through 2b tumors treated with BT who attained a 5-year TTLF of 94% and CSS of 91%. In contrast, the worst prognostic group, i.e., 5-year TTLF of 47% and CSS of 24%, was composed of patients with T4 and/or N2c through 3 tumors who did not receive BT. CONCLUSION High doses of radiation (73 to 95 Gy) can be administered to patients with NPC with minimal morbidity by means of optimized HDR-BT. The use of a BT boost proved to be of significant benefit, particularly in patients with T1 through 3, N0 through 2b disease. The steep dose-effect relationship seen for the physical dose and the BEDcor10 indicates that the results are dose related. The analysis has identified a poor prognostic group in whom treatment intensification with chemotherapy (CHT) is indicated.

scholarly journals Radiation Exposure of Personnel Categories at the Center of Oncology and Hematology at Mohammed VI Hospital in Marrakech

2019 ◽  
pp. 1-7
Author(s):  
Bouchra Amaoui ◽  
Abdennasser El Kharras ◽  
Mohammed Aabid ◽  
Oum Keltoum Hakam ◽  
Abdelmajid Choukri ◽  
...  
Keyword(s):  
Ionizing Radiation ◽  
Dose Rate ◽  
Treatment Time ◽  
Radiological Protection ◽  
Average Dose ◽  
Annual Dose ◽  
Overall Treatment Time ◽  
Dose Rates ◽  
Average Value ◽  
Regulatory Standards

Objective: This study aims to estimate the annual doses for personnel categories following their exposure to ionizing radiation during their occupation in the external radiotherapy department of the Center of Oncology and Hematology (COH) at Mohammed VI Hospital in Marrakech. Materials and Methods: Operational dosimeters PACK MGP DMC 3000 were used to measure the dose rates around the machines operating with ionizing radiation. In order to assess the reliability of the measurements made by these dosimeters, they were checked against measurements made at the same position by the Inspector detector. The annual effective dose was calculated by multiplying the average dose rate measured during a procedure by the overall treatment time throughout a year. Results: Regarding the reliability check of the measuring instrument, the recorded error is between 2 and 10% with an average of 7%. For personnel category A, the measured dose rate ranges from 0.066 to 0.083 µSv/h, with an average value of 0.075 µSv/h. For category B, it varies between 0.066 and 0.083 µSv, with an average value of 0.092 µSv/h. It is 0.074 µSv/h for category C. The annual dose for category A ranges from 0.089 to 0.113 mSv/year, with an average value of 0.101 mSv/year. For category B, it varies between 0.089 and 0.113 mSv/year, with an average value of 0.100 mSv/year. It is 0.100mSv/year for category C. Conclusion: The annual effective doses to personnel categories, assessed by this study, are very low compared to the regulatory standards set by the International Commission on Radiological Protection (ICRP). As a result, workers benefit from good radiation protection conditions within the Center of Oncology and Hematology at Mohammed VI Hospital in Marrakech.

Total radiation dose and overall treatment time are predictive for tumor sterilization in cervical carcinoma treated with chemoradiation and pulsed-dose-rate brachytherapy

Brachytherapy ◽  
2015 ◽  
Vol 14 (1) ◽  
pp. 16-22 ◽  
Author(s):  
Lorraine Krebs ◽  
Sophie Maillard ◽  
Nathalie Gaillot-Petit ◽  
Cécile Ortholan ◽  
Tan Dat Nguyen
Keyword(s):  
Radiation Dose ◽  
Dose Rate ◽  
Cervical Carcinoma ◽  
Treatment Time ◽  
Total Radiation ◽  
Overall Treatment Time ◽  
Total Radiation Dose ◽  
Pulsed Dose Rate

scholarly journals Intermolar Mandibular Distraction Osteogenesis—A Preliminary Report

2021 ◽  
Vol 11 (9) ◽  
pp. 4118
Author(s):  
Suen A. N. Lie ◽  
Britt H. B. T. Engelen ◽  
Veronique C. M. L. Timmer ◽  
Nico M. P. Vrijens ◽  
Paolo Asperio ◽  
...  
Keyword(s):  
Distraction Osteogenesis ◽  
Treatment Time ◽  
Average Length ◽  
Case Series ◽  
Growth Spurt ◽  
Overall Treatment Time ◽  
Mandibular Distraction ◽  
Mandibular Distraction Osteogenesis ◽  
Root Fractures

Background: Dental Class II is the most common indication for combined orthodontic-orthognathic treatment. Intermolar mandibular distraction osteogenesis (IMDO) treatment was performed during the growth spurt, to avoid surgery at a later age. The aim of this study is to present our first experience with IMDO. Methods: This is a retrospective case series of patients who underwent an IMDO. All patients showed mandibular retrognathism, and orthodontic treatment with functional appliances was not successful. Results: In total, 20 patients (mean age of 14.8 years (SD = 0.9 ys) were included. All patients achieved a Class I occlusion. An average length gain of 9.6 mm (SD = 3.7 mm) was reached. In one patient an abscess occurred. Nine patients presented with root fractures of the second molar; three were lost, one treated endodontically. The average time between insertion and removal of the distractors was 4.6 months (SD = 1.5 mths). In one case a premature consolidation was seen. Conclusion: We achieved satisfactory results with IMDO, although undesirable effects occurred. An advantage is the manageable overall treatment time. Open questions concern the occurrence of root fractures. Furthermore, the question of long-term stability is open. The question of dynamic distraction treatment in relation to temporomandibular joint changes can only be answered in the long term.

Primary Human Liver Cells as Source for Modular Extracorporeal Liver Support - a Preliminary Report

2002 ◽  
Vol 25 (10) ◽  
pp. 1001-1005 ◽  
Author(s):  
I.M. Sauer ◽  
K. Zeilinger ◽  
N. Obermayer ◽  
G. Pless ◽  
A. Grünwald ◽  
...  
Keyword(s):  
Human Liver ◽  
Treatment Time ◽  
Liver Perfusion ◽  
Cell Mass ◽  
Liver Weight ◽  
Liver Cells ◽  
Liver Support ◽  
Overall Treatment Time ◽  
Human Liver Cells ◽  
Extracorporeal Liver Support

Cell-based extracorporeal liver support is an option to assist or replace the failing organ until regeneration or until transplantation can be performed. The use of porcine cells or tumor cell lines is controversial. Primary human liver cells, obtained from explanted organs found to be unsuitable for transplantation, are a desirable cell source as they perform human metabolism and regulation. The Modular Extracorporeal Liver Support (MELS) concept combines different extracorporeal therapy units, tailored to suit the individual and intra-individual clinical needs of the patient. A multi-compartment bioreactor (CellModule) is loaded with human liver cells obtained by 5-step collagenase liver perfusion. A cell mass of 400 g – 600 g enables the clinical application of a liver lobe equivalent hybrid organ. A detoxification module enables single pass albumin-dialysis via a standard high-flux dialysis filter, and continuous venovenuous hemodiafiltration may be included if required. Cells from 54 human livers have been isolated (donor age: 56 ± 13 years, liver weight: 1862 ± 556 g resulting in a viability of 55.0 ± 15.9%). These grafts were not suitable for LTx, due to steatosis (54%), cirrhosis (15%), fibrosis (9%), and other reasons (22%). Out of 36 prepared bioreactors, 10 were clinically used to treat 8 patients with liver failure. The overall treatment time was 7–144 hours. No adverse events were observed. Initial clinical applications of the bioreactor evidenced the technical feasibility and safety of the system.

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