Related Experiment Video
Updated: May 20, 2026
07:13
A Two-interval Forced-choice Task for Multisensory Comparisons
Published on: November 9, 2018
Optimization of temporal dose modulation: comparison of theory and experiment
J M Bewes1, N Suchowerska, L Cartwright
1Faculty of Medicine, University of Sydney, Sydney, NSW, Australia.
Medical Physics
|July 5, 2012
Summary
Radiation dose patterns significantly impact cell survival, especially for cells with high beta values, when treatment times approach cellular repair times. This highlights the importance of considering dose delivery patterns in hypofractionated radiation therapy.
Area of Science:
- Radiation oncology
- Radiobiology
- Cellular biophysics
Background:
- Understanding cell survival kinetics is crucial for optimizing radiation therapy.
- Temporal modulation of radiation dose delivery can influence biological outcomes.
- The Lea-Catcheside formalism provides a framework for modeling cell survival under protracted irradiation.
Purpose of the Study:
- To compare theoretical predictions with experimental measurements of cell survival.
- To evaluate the impact of two distinct temporally modulated radiation dose patterns ('triangle' and 'V') on cell survival.
- To assess if dose protraction factor (G) predictions align with experimental data across different cell lines and doses.
Main Methods:
- Derived analytic expressions for the dose protraction factor (G) within the Lea-Catcheside formalism for 'triangle' and 'V' dose modulations.
- Conducted experimental clonogenic assays using melanoma (MM576) and non-small cell lung cancer (NCI-H460) cell lines.
- Maintained constant overall treatment time and total radiation dose while varying temporal dose patterns.
Main Results:
- The 'triangle' dose pattern consistently yielded a larger dose protraction factor (G) than the 'V' pattern.
- Experimental results showed a higher survival fraction for the 'V' pattern in MM576 cells at a high dose (6 Gy), aligning with theoretical predictions.
- No significant differences in survival were observed for lower doses or in the NCI-H460 cell line, consistent with theoretical models within experimental uncertainty.
Conclusions:
- Cell lines with high beta values demonstrate sensitivity to radiation dose delivery patterns when treatment times are comparable to cellular repair times.
- Theoretical models accurately predict experimental outcomes, validating the Lea-Catcheside formalism for modulated dose delivery.
- Dose delivery pattern should be a considered factor in the planning of hypofractionated radiation treatments.
Related Concept Videos
01:21Dose Size and Dosing Frequency: Determination Methods
Determining the optimal dose size and dosing frequency in pharmacotherapy is crucial for achieving therapeutic effectiveness while minimizing adverse effects. This article explores the methodologies employed in determining these parameters, focusing on their significance and interplay to tailor dosing regimens.Dose Size: Dose size refers to the amount of a drug administered in a single dose. It is determined based on the drug's pharmacodynamics and pharmacokinetics properties and...
01:24Pharmacokinetic–Pharmacodynamic Relationship: Problems
The empirical approach to drug therapy optimization relies on correlating pharmacological response with administered dosage. Such an approach can be costly, time-consuming, and often yields poor correlation due to variables like formulation factors and drug elimination characteristics. A more precise approach correlates response with plasma drug concentration or the amount of drug in the body, rather than dosage. This is achieved through pharmacokinetic-pharmacodynamic (PK/PD) modeling, which...
01:28Methods of Medium Optimization
Optimizing growth media enhances microbial proliferation and maximizes product yield. Statistical experimental design methodologies provide structured and reproducible approaches, offering progressively higher levels of robustness and efficiency.The One-Factor-at-a-Time (OFAT) MethodThe One-Factor-at-a-Time (OFAT) method involves adjusting a single variable while keeping all others constant. However, it cannot detect interactions between variables, often leading to suboptimal outcomes when...
01:25Determination of Multiple Dosing Parameters: Loading and Maintenance Doses
A loading dose is an essential pharmacological strategy to rapidly achieve the target plasma drug concentration necessary for an immediate therapeutic effect. This approach is especially critical for drugs characterized by slow absorption or extended half-lives, where delaying therapeutic plasma levels could compromise treatment outcomes. By administering a loading dose, clinicians ensure a prompt onset of drug action, even for agents with complex pharmacokinetic profiles.Achieving steady-state...
01:03Dose-Response Relationship: Overview
Agonists can bind with and activate receptors, resulting in the formation of drug-receptor complexes. Once formed, these complexes catalyze many biochemical processes at the cellular level and subsequently induce a pharmacologic response. The degree of response is directly proportional to the fraction of activated receptors, which in turn, depends on the concentration of the drug at the receptor site as well as the sensitivity of the receptor. An increase in the administered dose contributes to...
01:22Dose-Response Relationship: Potency and Efficacy
The potency of a drug is the measure of its ability to produce a biological response and can be compared by looking at the half-maximum effective concentration or EC50 values of different drugs. A lower EC50 value indicates higher potency of the drug. In the dose–response curve of two antihypertensive drugs, candesartan and irbesartan, a significant difference is observed in their EC50 values. A lower EC50 value for candesartan indicates that it is more potent than irbesartan, as it produces...