TP3 final exam review Questions And Answers Graded A+!!!!

SBRT lung fractionation - ANS 6-30 Gy in 1-5fx 5 Fx x 10 Gy 4 Fx x 12 Gy 3 Fx x 20 Gy Dose heterogeneity - ANS 1. Overlapping beams with tight margin will put high doses in the center of the target. 2. High Doses in Center may not help radiobiologically but there is no particular disadvantage. 3. Higher dose of radiation administered anywhere within the tumor will enhance the composite cytotoxic effect of and increase the TCP. 4. EUD (Equivalent Uniform Dose) is more robust for prospective description of SBRT. EUD is less sensitive to estimates of surviving fractions and number of tumor chologens. Normalization for SBRT lung? - ANS 80-90% SBRT lung constraint spinal cord? - ANS 18Gy SBRT lung constraint esophagus? - ANS 27Gy SBRT lung constraint ipsilateral lung? - ANS 24Gy SBRT lung constraint heart? - ANS 30Gy SBRT lung constraint trachea? - ANS 30Gy SBRT lung constraint ipsilateral bronchus? - ANS 30Gy SBRT lung constraint whole lung? - ANS V20 10% SBRT target delineation? - ANS GTV, CTV, ITV, PTV? GTV=CVT for SBRT ITV: Margin added to CTV PTV: 5mm all directions with exception 10mm Sup-Inf 1. Margins around targets can vary from -4mm to +4mm. 2. With negative margins, there will be a higher dose in the center. 3. With negative margins, there is a larger gradient created. Why do we use 4D CT in lung treatments? - ANS It allows us to see the movement of the tumor with the patients breathing cycle If the tumor is moving too much and the PTV is not drawn to encompass this movement then the tumor would not get the full dose. SBRT rib and chestwall info - ANS -Follow up Intervals are longer post tx with increased survival -Delayed morbidity is becoming increasingly important -Rib and Chestwall can be Organ at Risk (OAR) especially for peripherally located lesions -Need