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EXAM SPECIFIC PLANNI
| Question | Answer |
|---|---|
| sequential fractionations | H/N Ph1: left upper neck + nodes 44/22 Ph2: upper neck 16/8 PROSTATE Ph1: pros and SV 56/28 Ph2 pros: 18/9 |
| SIB fractionations | H+N: 70/35, with a PTV70, PTV63 and PTV56 H+N: 60/30, with PTV60 and PTV44 PROSTATE: 78/39 with PTV78, 64, 54 PROSTATE: 74/37 with PTV 54 and 74 |
| advantages and disadvantages of PB | advantages: fast disadvantages: poor representation of inhomogeneity effects, assumes monoenergetic beams, struggles to deal with irregular contours, density scaling that does not account for lateral scatter |
| advantages and disadvantages of CC | advantages: accounts for inhomogeneities, accounts for spectrum of energies and beam modifiers disadvantages: can be slow, difficult to commission |
| advantages and disadvantages of MC | advantages: extremely accurate, inherently accounts for patient and beam parameters disadvantages: demanding of computer power, slow, difficult to commission, statistical uncertainty |
| NCP beam arrangements | RIGHT LAT: G270, Couch 0 (left lateral) Sup oblique G300, Couch 90 (or G80-100, Couch 290-310) ++ oblique G325, Couch 0 |
| bowtie beam arrangements | small breast (<20) - 1 medial arc, 1 lat arc medium breast (20-24) - 2 medial arcs and 1 lateral large breast (>24) 2 medial arcs and 2 lateral arcs LEFT: 0-300, 170-100 RIGHT: 60-0, 260-190 |
| hyperfractionation RATIONALE | -inc opportunity for redistribution and reoxygenation between fx -possibly lower OER - different sparing of late reacting normal tissues (improve tumoour control while limiting NTT) reduce damage to late responding NTT (sensitive to fx size) |
| hyperfractionation prescriptions | fx less than 1.8Gy given more than once a day |
| hypofractionation RATIONALE | total dose divided into large doses, given once a day or less good for low a/b ratio, fewer hospital visits |
| hypofractionation prescriptions | 40/15 to breast |
| acc fractionation RATIONALE | same as hyperfrac, counteract tumour repop during txt |
| acc fractionation prescriptions | 72/45 with three fractions of 1.6Gy per day. rest period of 2 weeks in the middle |
| define constant dose rate | refers to a treatment delivery mode in which the dose rate of the radiation beam (MU/min) remains fixed throughout beam-on time. different to variable dose rate (VDR): machine can speed up or slow down dynamically to achieve modulation more efficiently. |
| define fluence map | a 2D representation (matrix) that shows the spatial distribution of photon fluence (or intensity) across the beam’s cross-section. Each pixel (or small segment) of the map corresponds to how much radiation is intended to pass through that area. |
| 3DCRT small field larynx | opposing lateral fields, bolus on anterior surface with collimation along angle of spinal cord |
| unilateral parotid volume (3dcrt) | include lower neck - junction required traditional wedge pair or 3 field arrangement |
| bilateral vol (e.g. oropharynx) | junction technique with multifield arrangement (parotid sparing) |
| bilateral facial volumes | 6-8 fields, posterior, post obliques, lats, and ant obliques |
| IMRT arrangement for h/n | 7-9 beams, no opposing fields |
| AAPM RECS | (full answer) |
Created by:
jrichardss