Less than 50% of the right parotid (light blue) volume receives at most what dos

Question

Less than 50% of the right parotid (light blue) volume receives at most what dose? A. 1221 cGY B. 2100 cGY C. 2635 cGY D. 3000 cGY What is the mean dose to the right parotid (light blue) volume? A. 1221 cGY B. 2100 cGY C. 2635 cGY D. 3000 cGY In an intensity-modulated radiation therapy (MRT) plan, the radiation oncologist requests that 95% of the planning target volume (PTV) be covered by 95% of the prescribed dose, with the maximum dose not to exceed 105%. A plan is created with only 85% if the prescribed dose covering 95% of the PTV. Possible reasons include all of the following except. A. The PTV is drawn to include part of the build-up region. B. The manually set field sizes are too small. C. The photon every is to low. D. The PTV overlaps an organ at risk, which has been given higher priority. In conformal radiation treatment of the prostate, the four field box technique has been used for many years. IMRT treatments of the prostate are now common because of: A. better tumor control B. less rectal toxicity C. faster treatment times D. higher reimbursements Which of the following statements is true? A. The integral total dose the patient receives is more for IMRT B. The does non-uniformity within the PTV is always less for IMRT C. The dowse non-uniformity within the PTV is always less for conformal radiation therapy. D. None of the above Can IMRT sharpen the dose off between the target and an organ at risk? A. Yes, a narrow inset field at drop off between the target and an organ at risk? B. yes, by including non - coplanar beams. C. Yes, by using optimizing dose volume constructs to force the IMRT optimizer to provide the required dose fall off. D. All of the above.

Explanation / Answer

In Head and neck cancer The light blue line represents the 4800 cGy blue area is therefore 50% of this dose is 2400 cGy

also Mean dose to the parotid was kept below 2600 cGy

one can say the answer is b)2100 cGy

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