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Related Concept Videos

Respiratory Volumes01:15

Respiratory Volumes

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Respiratory volumes are crucial metrics, meticulously measured to quantify the air exchanged in and out of the lungs during various phases of the breathing cycle. These precise measurements are vital for assessing lung function, diagnosing respiratory conditions, and monitoring overall respiratory health. Each parameter provides specific insights into the mechanics of breathing and the functional capacity of the lungs.
Tidal Volume (TV) Tidal volume (TV) is the air inhaled or exhaled in a...
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Respiratory Volumes and Capacities01:22

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The respiratory system is responsible for the intake of oxygen and the expulsion of carbon dioxide from the body. Respiratory volumes describe the volume of air in the lungs at different phases of the respiratory cycle. Tidal volume is the air breathed in and out during normal, quiet breathing. Inspiratory reserve volume is the air that can be forcefully inspired beyond the tidal volume. In contrast, expiratory reserve volume refers to the air that can be expelled from the lungs after a normal...
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Pressure Relationships in Thoracic Cavity01:24

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Breathing, otherwise known as pulmonary ventilation, is the process of air movement into and out of the lungs. The main mechanisms propelling pulmonary ventilation are atmospheric pressure (Patm), intra-pulmonary (Ppul ) or intra-alveolar pressure (Palv) within the alveoli, and intrapleural pressure (Pip) within the pleural cavity.
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Respiratory Volumes and Capacities I01:26

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Assessing the respiratory rate and rhythm for a complete minute is crucial for evaluating the breathing pattern. Even a minor increase in the patient's average respiratory rate, by as little as three to five breaths per minute, is an early and vital indicator of respiratory distress. Patients with a respiratory rate exceeding twenty-four breaths per minute require close monitoring to determine the physiological alterations. This careful observation is essential for prompt recognition and...
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Factors Affecting Pulmonary Ventilation01:19

Factors Affecting Pulmonary Ventilation

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Besides the pressure difference between the external environment and the lungs, the airflow rate and ease of pulmonary ventilation are also influenced by three other factors: surface tension of the fluid in the alveoli, compliance of the lungs, and airway resistance.
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Lung Capacity01:47

Lung Capacity

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The air in the lungs is measured in volumes and capacities. Lung volume measures reflect the amount of air taken in, released, or left over after a lung function, like a single inhalation. Lung capacity measures are sums of two or more lung volume measures.
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An analytical expression for R50% dependent on PTV surface area and volume: a lung SBRT comparison.

Dharmin D Desai1, E L Johnson2, Ivan L Cordrey1

  • 1Department of Radiation Oncology, CHI Memorial Hospital, Chattanooga, TN, USA.

Journal of Applied Clinical Medical Physics
|September 30, 2020
PubMed
Summary

Researchers derived an analytical formula for R50%, a key metric in stereotactic body radiation therapy (SBRT), simplifying dose spill assessment. This new formula accurately predicts R50% for spherical targets, improving radiation treatment planning.

Keywords:
PTV surface areaR50%analytic equationlung SBRT

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Area of Science:

  • Medical Physics
  • Radiation Oncology
  • Radiotherapy Planning

Background:

  • R50% is a standard metric in stereotactic body radiation therapy (SBRT) to quantify intermediate dose spill.
  • It is defined as the ratio of the 50% isodose cloud volume (IDC50%) to the planning target volume (PTV).
  • Accurate assessment of dose spill is crucial for optimizing SBRT treatment plans and minimizing toxicity.

Purpose of the Study:

  • To derive an exact analytical expression for the R50% metric.
  • To validate this expression using clinical data from stereotactic body radiation therapy.
  • To provide a simplified and accurate method for calculating intermediate dose spill in SBRT.

Main Methods:

  • Developed an analytical expression for R50% based on physical principles for spherical volumes.
  • The expression relates R50% to the planning target volume's surface area (SAPTV), volume (VPTV), and dose gradient (Δr).
  • Validated the derived formula by comparing its computed R50% values against clinical data from diverse, multi-institutional studies.

Main Results:

  • An exact analytical expression for R50% in spherical volumes was successfully derived.
  • The analytical expression accurately predicts R50% values.
  • Comparison with clinical data showed an average percent difference of 3.8 ± 4.5%, confirming the expression's validity.

Conclusions:

  • The derived analytical expression for R50% offers a precise and efficient method for assessing intermediate dose spill in SBRT.
  • This formula simplifies calculations and can enhance the accuracy of radiotherapy planning.
  • The validated expression holds significant potential for improving SBRT treatment optimization and patient outcomes.