Normal tissue sensitivity Flashcards
dose constraint for the brain?
max dose: 50Gy
What is the toxicity end point for the brain?
Symptomatic necrosis
Reduced cognitive development in children receiving whole- brain RT
Brain very sensitive to more than 2Gy per fraction and twice daily treatment
Is the brain a serial or parallel structure?
Parallel
What is the alpha beta ratio of the brain?
2.9
What is the dose constraint for the optic chiasm?
Max dose: 55Gy
Toxicity end point for the optic chiasm?
Potential for partial visual loss on section of optic nerve receiving dose
Optic neuropathy
Is the optic chiasm serial or parallel?
serial
What is the dose constraint for the brain stem?
Whole brainstem can receive no more than 54GY
Is the brain stem serial or parallel?
Serial
What is the toxicity end point for the brain stem?
Permanent cranial neuropathy or necrosis
What is the alpha beta ratio for the brain stem?
2.5-3.3
Max dose for the spinal cord?
Max dose: 45Gy it actually says 50 Gy in QUANTEC
What is the toxicity end point for the spinal cord?
Myelopathy
0.2% myelopathy with 50Gy (2Gy/#)
6% mylelopathy with 60Gy (2Gy/#)
Is the spinal cord serial or parallel?
serial
Alpha beta ratio for the spinal cord?
0.87
Max dose to the salivary glands?
Single parotid limit of 20Gy
Both parotids linnet of 25Gy
Submandibulars limit to 35Gy to help
DVH’s not reliable as GLANDS SHRINK DURING TREATMENT and gland sparing decreases
Toxicity end point for the salivary glands?
Long term parotid salivary function reduced.
are the salivary glands serial or parallel?
Parallel
Larynx and Pharynx dose constraint?
Absolute limit of 66Gy
40-45Gy if larynx is not the target structure
Toxicity end point for the larynx and pharynx?
Pharynx: Dysphagia
Larynx: Vocal dysfunction, Oedema, Aspiration
Dose constraint for the lung?
V20 limit 30-35%
What is the toxicity end point for the lung?
Fibrosis (a/b 3.5)
Pneumonitis (a/b 4)
Is the lung serial or parallel?
Parallel
What is the alpha beta ratio for the lung?
3.5-4
What is the dose constraint for the heart?
V25Gy
What are the toxicity end points of the heart?
Long term Cardiac mortality
Diffuse myocardial fibrosis
Pericarditis
Is the heart serial or parallel?
Mixed serial/parallel
What is the max dose for the oesophagus?
40-50Gy to limit acute oesophagitis
Toxicity end point for the oesophagus?
Oesophagitis – grade 3 acute
Is the oesophagus serial or parallel?
Parallel
What is the dose constraint for the liver?
Whole liver (mets) 30Gy
Primary liver: 28Gy
Toxicity end point for the liver?
Radiation induced liver disease
Is the liver serial or parallel?
Highly parallel
Dose constraint for the small bowel and stomach?
Hard to delineate with contrast
50Gy limit
15Gy <120 cc (cubic centimeters) – which is 120 mL
Toxicity end point for the stomach and small bowel?
Ulceration
Grade 3+ toxicity
Are the stomach and small bowel serial or parallel?
Serial
Bladder dose constraints?
V80 <15%
V75< 25%
V65 <50%
Is the bladder serial or parallel?
Mixed-parallel
What is the toxicity end point for the bladder?
Grade 3+ toxicity
What are the dose constraints for the rectum?
V50Gy < 50%
V70Gy < 20%
V75Gy < 15%
Toxicity end point for the rectum?
Grade 3+ late rectal toxicity
Is the rectum serial or parallel?
Serial/Parallel
What are the dose constraints for the penile bulb?
D90
D60-70
What is the toxicity end point for the penile bulb?
Severe erectile dysfunction
Is the penile bulb serial or parallel?
Parallel