Skills
The techniques that get re-explained in every write-up that uses them — a ring for fall-off, a tuning structure for a hotspot. Written once and quotable, so a notebook can point at one instead and stay about its own case.
delivery
Avoidance sectors through a serial OAR
Stop the beam entering through the organ you are trying to spare, rather than asking the optimizer to undo it afterwards.
freeCollimator angle and jaw tracking on a C-arm
C-arm linac2 refsTwo settings most planners leave at default that measurably change the plan, especially with multiple targets.
freeComplete versus directional blocking
Radixact / TomoTherapy2 refsTwo different tools with the same name. One removes entry and exit, the other only removes entry.
freeFixed cone, Iris or MLC
CyberKnife2 refsThe MLC is 30–40% faster and slightly less conformal — which matters depends entirely on the case.
freePicking pitch, modulation factor and field width
Radixact / TomoTherapy2 refsThree numbers decide most of a helical plan. There is a published Pareto front and a rule for pitch — use them instead of the defaults.
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evaluation
Choosing the prescription isodose line
CyberKnife2 refsA robotic plan is prescribed far lower than a C-arm plan on purpose — the heterogeneity is where the gradient comes from.
freeComplexity metrics, and what they actually predict
2 refsMU per Gy is the crude measure. MCS is the one with a published correlation to QA failure — and the correlation is only moderate.
freeReading a hard constraint against coverage
A disqualifying limit is not one objective among many. Spend everything else before you spend it.
freeThe dose algorithm decides the number you are judged on
2 refsIn lung, a pencil-beam and a Monte Carlo calculation of the same plan disagree by up to 10%. Nothing about the plan changed.
freeWhat to read on a DVH before changing anything
Three questions, in order, that tell you which knob to turn — and stop you turning all of them.
freeWhen the shared contour is the problem
1 refsEveryone is scored on the same structure set, so an error in it moves every plan the same way — and no leaderboard can show that.
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optimization
Adapt-to-position or adapt-to-shape
MR-linac2 refsOne reuses the plan's shapes against today's position; the other re-contours and re-optimizes. The difference is roughly half an hour.
freeChanging one thing per optimization
Two changes at once and you have learned nothing about either. The chain of versions is the write-up.
freeKnowledge-based planning, and when to distrust it
3 refsA model predicts achievable DVHs from your anatomy. It is only as good as the plans it was trained on — including their bad habits.
freePareto navigation instead of re-optimizing
2 refsCompute a set of Pareto-optimal plans once, then slide between them in real time. The trade-offs become visible instead of guessed.
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structures
Reviewing an auto-segmented contour
3 refsDice tells you almost nothing about whether a contour will change the plan. Review where the dose gradient is, not where the volume is.
freeRing structure for dose fall-off
A shell a few millimetres outside the PTV, pushed hard, to force the gradient down instead of hoping for it.
freeShell ladder for conformity and fall-off
CyberKnife2 refsFive concentric shells at different distances, each doing a different job — conformity, fall-off, then spillage.
freeSparing structures nobody scored you on
2 refsConstrictors and larynx can be spared at no measurable cost to target coverage or parotid dose. Most head and neck plans simply never ask.
freeSubtraction structures for an overlapping OAR
2 refsWhen the target overlaps something you must spare, split the target rather than asking the optimizer to satisfy both in the same voxels.
freeText-prompted segmentation for the structure nobody contoured
2 refsAsk for a structure in words and get a 3D mask. Useful precisely for the organs a challenge's structure set left out.
freeThecal sac as the cauda equina surrogate
2 refsBelow the cord there is no cord. What you contour instead changes the constraint, and contouring the nerve roots individually is not reproducible.
freeTuning structure to pull a hotspot
Contour the hotspot itself, then constrain it. Faster and more local than raising the global max-dose weight.
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