Lecture 6 Plan Evaluation Flashcards
Criteria of a good plan?
- Dosimetric
- high dose encloses the target volume
- low dose to normal structures
- uniform dose inside target volume - Biological
- good tumour control
- low risk of complications to normal organs - Practical
- setup convenience
- treatment time
- risk of committing mistakes
Definition of DVH
- graphical representation of dose statistics in a specified structure
- summed volume of elements receiving dose in a specified dose interval
- differential or cumulative
Main uses of DVH
- check the dose adequacy and uniformity in target volumes
- extent and value of hotspots
- dose comparison between rival plans
Limitation of DVH?
- cannot handle dose heterogeneities
- deviations at regions of steep dose gradient
- no spatial information
Definition of conformity index?
Quantify the degree of congruence between isodose contours and tumour contours
Definition of homogeneity index?
Describes the uniformity of dose within a treated target volume
Name 2 biological plan evaluation tools
- tumour control probability
- normal tissue complication probability
What is tumour control probability?
= sum of TCP of tumor voxels
A biological index to predict clinical tumor control
Dependent parameters:
- dose distributions
- tumor sensitivity
- tumor doubling time
- overall treatment time and fractionation
What is normal tissue complication probability
= biological index to predict the chance of developing complications in normal tissue
Dependent parameters
- dose distributions
- dose tolerance of normal tissue
- serial or parallel ogans
3 parameters of Lyman-Kutcher-Burman NTCP model
- TD50 (dose for resulting 50% of a complication)
- dose response curve
-serial or parallel organs
What is TD5/5 and TD50/5
TD5/5 = probability of 5% complication within 5 years from treatment
TD50/5= probability of 50% complication within 5 years form treatment
What is CB-CHOP
Contours
Beam arrangement
Coverage
Hotspots
OARs
Prescription
