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Related Concept Videos

Planar Rigid-Body Motion01:22

Planar Rigid-Body Motion

Understanding the movement of a rigid body in planar motion involves recognizing that every particle within this body is traversing a path that maintains a consistent distance from a specific plane. This concept is fundamental in the study of physics and mechanical engineering, and it allows us to comprehend better how objects move in space.
Planar motion is typically divided into three distinct categories. The first is rectilinear translation, demonstrated by a subway train that moves along...
Relative Motion Analysis - Acceleration01:10

Relative Motion Analysis - Acceleration

A slider-crank mechanism converts rotational motion from the crank into linear motion of the slider or vice versa. This mechanism consists of three main parts: the crank, the connecting rod, and the slider. The movement of the slider-crank is an example of general plane motion as the fluctuating angle between the crank and the connecting rod. Consider a segment AB where point A is at the end of the slider and point B is on the diametrically opposite end to point A, on a crack. The variance in...
Relative Motion Analysis - Velocity01:24

Relative Motion Analysis - Velocity

A stroke engine has a slider-crank mechanism that converts rotational motion from the crank into linear motion of the slider or vice versa. This mechanism consists of three main parts: the crank, the connecting rod, and the slider.
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Rotation with Constant Angular Acceleration - I01:37

Rotation with Constant Angular Acceleration - I

If angular acceleration is constant, then we can simplify equations of rotational kinematics, similar to the equations of linear kinematics. This simplified set of equations can be used to describe many applications in physics and engineering where the angular acceleration of a system is constant.
Using our intuition, we can begin to see how rotational quantities such as angular displacement, angular velocity, angular acceleration, and time are related to one another. For example, if a flywheel...
Principle of Impulse and Moment01:15

Principle of Impulse and Moment

When one considers a rigid body undergoing a plane motion, which is essentially a blend of translational and rotational movement, the application of Newton's second law gives the formula for the translational movement of such a body. If this equation is multiplied by a time interval, dt, and then integrated over the limits of integration, it results in an equation that embodies the principle of linear impulse.
Moments of Inertia for an Area about Inclined Axes01:18

Moments of Inertia for an Area about Inclined Axes

In physics and engineering, understanding the moments of inertia for a given area with asymmetrical mass distribution is critical for proper design and analysis. When considering an arbitrary coordinate system, the moments of inertia can be obtained by integrating the moment of inertia for an infinitesimal area element.

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Radiation Planning Assistant - A Streamlined, Fully Automated Radiotherapy Treatment Planning System
08:25

Radiation Planning Assistant - A Streamlined, Fully Automated Radiotherapy Treatment Planning System

Published on: April 11, 2018

Similarities between static and rotational intensity-modulated plans.

Q Jackie Wu1, Fang-Fang Yin, Ryan McMahon

  • 1Department of Radiation Oncology, Duke University School of Medicine, Durham, NC 27710, USA. jackie.wu@duke.edu

Physics in Medicine and Biology
|December 2, 2009
PubMed
Summary

Intensity-modulated radiotherapy (IMRT) and intensity-modulated arc therapy (IMAT) require a minimum number of multi-leaf collimator (MLC) segments for optimal plan quality. Both techniques show similar dose inhomogeneity when using comparable MLC segments.

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Area of Science:

  • Radiation Oncology
  • Medical Physics

Background:

  • Intensity-modulated radiotherapy (IMRT) and intensity-modulated arc therapy (IMAT) are advanced radiation therapy techniques.
  • The number of multi-leaf collimator (MLC) segments is a critical factor influencing treatment plan quality and modulation capability.

Purpose of the Study:

  • To compare the similarities between IMRT and IMAT regarding the number of MLC segments needed to achieve treatment objectives.
  • To evaluate the impact of MLC segment count on target dose inhomogeneity for both IMRT and IMAT.

Main Methods:

  • Three clinical cases of increasing complexity (prostate, prostate with seminal vesicles, prostate with pelvic lymph nodes) were studied.
  • Gold-standard plans were generated, and multiple IMRT and IMAT plans were created with varying segment numbers.
  • Plans were assessed based on organ-at-risk sparing, target coverage, and target dose inhomogeneity (D5).

Main Results:

  • Both IMRT and IMAT plans demonstrated similar target dose inhomogeneity for a comparable number of MLC segments.
  • Target dose inhomogeneity remained relatively constant until a critical number of segments was reached, after which it sharply increased.
  • Critical segment numbers varied by case complexity (70, 100, 110 for cases a, b, c respectively).

Conclusions:

  • IMAT and IMRT exhibit similar dependencies on the number of MLC segments for achieving adequate plan quality.
  • A minimum critical number of MLC segments is essential for both techniques to ensure sufficient modulation and dose distribution.
  • Further research is needed to define minimum critical segment numbers across diverse treatment sites and anatomical configurations.