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normal tissue tolerance dose in terms of the total dose delivered by a standard fractionation schedule that causes a minimal 5%complication in 5 years
normal tissue tolerance dose in terms of total dose delivered by a standard fractionation schedule that causes a maximal 50%0 complication rate in 5 years
what two factors affect the NTTD?
the volume irradiated and fraction size
as volume of the organ affected by the treatment increases the tolerance dose for the organ?
as the size of the daily fraction increases the tolerance of normal tissue?
lung td5/5 (1/3 lung)
endpoint for Lung
spinal cord td5/5
spinal cord end point
Small Bowel td5/5
Small bowel endpoint
obstruction / perforation
Rectum end point
Gross tumor volume GTV
all known disease including abnormally enlarged regional lymph nodes
Clinical target volume CTV
encompasses the gtv plus regions presumed to harbor potential microscopic disease/ margin of at least 1-2 cm around tumor.
GTV + CTV = ?
INTERNAL TARGET VOLUME
ACCOUNTS FOR PHYSIOLOGICAL PROCESSES SUCH AS RESPIRATION HEARTBEAT RESPIRATION
PLANNING TARGET VOLUME
PROVIDES MARGIN AROUND CTV TO ALLOW FOR VARIATION OR UNCERTAIN IN THE CTV
GTV+CTV+PTV = TARGET VOLUME
ACUTE EFFECTS OF RADIATION
NORMALLY REVERSABLE AND MAY OCCUR DURING OR SOON AFTER IRRADIATION.
EXAMPLES OF ACUTE EFFECTS
ESOPHAGUS-ESOPHAGITIS 3-4 WEEKS POST
LUNG-PNEUMONITIS 3MONTHS POST
IRREVERSIBLE ACUTE EFFECTS DUE TO DEPLETION OF NONPARENCHYMAL CELLS NORMALLY OCCURS MONTHS TO YEARS AFTER RADIOTHERAPY.
MOST RADIOSENSITIVE TISSUE CELLS
STEMM CELLS SUCH AS BONE MARROW,INTESTINAL EPITHELIUM AND GONADAL EPITHELIUM
TISSUE RESPONCE DEPENDS ON WHAT 2 FACTORS?
INHERENT SENSITIVITY OF THE VARIOUS CELL POPULATIONS IN THE TISSUE OR ORGAN/TUNROVER KINETICS OF EACH CELL POPULATION
What did Bergonie and Tribondeau observe?
Immature dividing cells were damaged after lower doses of radiation than were the mature nondividing cells.
Radiation is more effective against cells that are?
1. actively dividing
3. long mitotic activity
High sensitivity cell
Vegetative intermitotic cells VIM
rapidly dividing cell/undifferentiated/ basal cells, crypt cells, erythroblasts, spermatogonia
Differentiating intermitotic cells DIM
Reverting post mitotic cells RPM
USUALLY DONT DIVIDE BUT ARE CAPABLE OF DIVIDING (LIVER CELLS,LYMPHOCYTES
FIXED POST MITOTIC CELLS FPM
DO NOT DIVIDE
WELL DIFFERENTIATED (NERVE, MUSCLE,ERYTHROCYTES)
WHAT RPM CELL IS HIGHLY SENSITIVE?
STOMA OF THE TISSUE
SUPPORT (BLOOD SUPPLY
FUNCTIONAL PART OF THE TISSUE/ORGAN
TUMOR LETHAL DOSE
A CERTAIN DOSE CAN BE ASSIGNED FOR EACH TYPE OF TUMOR, WHICH WILL CAUSE DESTRUCTION OF A HIGH PROPORTION OF ITS CELLS
NORMAL TISSUE TOLERANCE DOSE
THE MAXIMUM DOSE WHICH CAN BE DELIVERED WITHOUT IRREPARABLE DAMAGE
BONE TUMOR TLD
WHAT MUST THE THERAPUTIC RATIO BE TO HAVE A MORE SUCCESSFUL ERADICATION?
TERAPUTIC RATIO GREATER THAN 1
ASPECTS OF THE CELL SURVIVAL CURVE
THE QUASI THRESHOLD DOSE where equal increases of dose do not cause a corresponding equal decreas in surviving fraction
=37% CELL SURVIVAL
low oxygen and are 2.5-3x more radioresistance than fully o2 cells
oxygen enhancement ratio OER
the dose of radiation that produces a given biological response in the absence of oxygen divided by the dose of radiation that produces the same biological response in the presence of oxygen
4 "R" of radiobiology
180cGy per fraction 5x a week
160-170cGy 5 fraction/week total dose is increased by 10%
how long for normal cell repair
how long for cancer cell repair
size and dose are similar to conventional fract. results in a shorter overall treatment course
same as treatment course as conventional but has a greater dose to tumor
what 2 Rs do you want for normal cells?
repair and repopulation
what 2 Rs do you want for cancer cells?
reoxygenation and redistrubution
Intro to Rad Onc