Interview Dose Constrainits
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18 Terms
What is the typical maximum dose constraint for the spinal cord in conventional fractionation?
Spinal cord Dmax ≤ 45–50 Gy.
Why is spinal cord dose usually evaluated using Dmax rather than volume?
The spinal cord is a serial organ, so maximum dose is the most critical predictor of toxicity.
What is a common lung dose constraint for conventional fractionation?
V20<20% (esophageal)
V20<15% (breast)
V20<10% (Total lung, SBRT)
What is a typical mean lung dose constraint?
Mean lung dose ≤ 20 Gy.
Why are lung constraints often volume-based?
Lung is a parallel organ, so toxicity depends on the volume irradiated.
What is a commonly used heart dose constraint in conventional treatments?
Mean heart dose ≤35
Breast: <2Gy
V30Gy<50%
What is the mean dose for the pharyngeal constrictors? Toxicity?
Mean <= 50 Gy
symptomatic dysphagia and aspiration
What is the larynx dmax constraint? Toxicity?
dmax < 66 Gy
vocal dysfunction
What is the larynx mean dose constraint? Toxicity?
Mean < 50 Gy
aspiration
What is the lung constraint? Toxicity?
V20 <= 30%
pneumonitis
what is the esophagus mean constraint? Toxicity?
Mean < 34 Gy
Grade 3+ esophagitis
What are the dose constraints for the heart? Toxicities?
Mean < 26 Gy
What is a common rectum constraint in conventional prostate IMRT?
Rectum V70 ≤ approximately 20-25%.
What type of constraint is most important for the rectum?
Volume-based constraints.
What is a common bladder dose consideration in prostate IMRT?
Limiting high-dose volumes such as V65–70 Gy.
What is a typical bladder maximum dose constraint in prostate SBRT (5 fractions)?
Bladder Dmax ≤ approximately 38–40 Gy.
Why are SBRT dose constraints generally tighter than conventional fractionation?
Because higher dose per fraction increases the risk of normal tissue toxicity.
What is the most important general rule when applying dose constraints clinically?
Always follow department protocols and physician-specific guidelines rather than relying on memory alone.