advances craniospinal irradiation
TRANSCRIPT
Advances in craniospinal irradiationWilliam Parker Carolyn FreemanWilliam Parker Carolyn Freemanyy
CSF pathways
Conventional technique
VanDyk, 1977 IJROBPVanDyk, 1977 IJROBPa y , 9 J Oa y , 9 J O
Conventional technique
From KHAN, 1998
Evolution of CSI technique
Supine positionSupine position
CT simulationCT simulation
Simplification of beam geometrySimplification of beam geometry
Improvement in volume definition (CT & MR)Improvement in volume definition (CT & MR)
Better junction planning Better junction planning
Forward step and shoot IMRT for dose compensationForward step and shoot IMRT for dose compensation
Use of inverse IMRT for posterior fossa treatment Use of inverse IMRT for posterior fossa treatment
IMRT/Tomotherapy for CSI IMRT/Tomotherapy for CSI
Supine position
Patient comfortPatient comfortPatient comfortPatient comfort
Access to airwayAccess to airway
Standard accessoriesStandard accessories
Reproducible setupReproducible setup
Virtual Simulation and 3D CRTuse “modern” use “modern” linaclinac features to simplify techniquefeatures to simplify technique
t i j f j ti f th i d h lft i j f j ti f th i d h lfasymmetric jaws for junction feathering and easy halfasymmetric jaws for junction feathering and easy half--blockingblocking
isocentricisocentric setup to eliminate unnecessary setupsetup to eliminate unnecessary setupisocentricisocentric setup to eliminate unnecessary setup setup to eliminate unnecessary setup motionsmotions
Posterior field & CS junction
INF limit set with INF limit set with
20 cm20 cm1111oo
asymmetric jaw up to asymmetric jaw up to 20 cm20 cm
20 cm20 cm20 cm20 cm
“isocentric setup” “isocentric setup” -- couch motions in one direction onlycouch motions in one direction only
Whole brain field
Insufficient coverage of the whole brain and meninges in the treatment of medulloblastoma Insufficient coverage of the whole brain and meninges in the treatment of medulloblastoma
may correlate with increased risk of local failure.may correlate with increased risk of local failure. IJROBP 37(3) 523-9, 1997
Liu, Carrie, Parker, Freeman, Med Pediatr Oncol 38(1), 2002
Whole brain field
collimator rotationcollimator rotationcollimator rotation collimator rotation 1111oo to match to match diverging post diverging post
i fi ldi fi ld20 cm20 cm
spine fieldspine field
isocenterisocenter
half blocked with half blocked with asymmetric jawasymmetric jaw
Whole brain field
CTV = brain CTV = brain
PTV = brain+ 3mm PTV = brain+ 3mm
field edges are 7mm field edges are 7mm ggfrom PTVfrom PTV
blocking with MLCblocking with MLCblocking with MLCblocking with MLC
treat the brain forget treat the brain forget the lensesthe lensesthe lensesthe lenses
Posterior spine field
Simplified beam geometry
1111oo20 cm20 cm 30 cm30 cm
Anterior setup for posterior treatment
CS j nctionCS j nctionCS junctionCS junction
isocentersisocenters
gapgap
Better junction planning
1111oo20 cm20 cm 30 cm30 cm
40 cm40 cm 10 + x cm10 + x cm20 cm20 cm
Better junction planning
1111oo20 cm20 cm 30 cm30 cm
38 cm38 cm 11 + x cm11 + x cm21 cm21 cm
Better junction planning
1111oo20 cm20 cm 30 cm30 cm
36 cm36 cm 12 + x cm12 + x cm22 cm22 cm
Dose compensation with “IMRT”
No compensationNo compensation
S&S IMRTS&S IMRT
Dose compensation
90%90% 5%5% 5%5%
Posterior field dose compensation
Posterior fossa boost
IJROBP 41(3) 625-629, 1998 MRIMRI CTCT
Boost target definition
Inverse IMRT for CSI Multiple post fieldsMultiple post fields
Smaller targetSmaller target
S d t l dS d t l dSpread out low dose Spread out low dose conform high doseconform high dose
IMRT for CSI
Junction QA
Summary
supine position is more comfortable, reproducible, and supine position is more comfortable, reproducible, and allows airway accessallows airway access
CT, MR for improved volume definitionCT, MR for improved volume definition
virtual simulation with simplified geometry is safervirtual simulation with simplified geometry is safer
IMRT for dose compensationIMRT for dose compensation
inverse conformal IMRT with tomotherapy is viable andinverse conformal IMRT with tomotherapy is viable andinverse conformal IMRT with tomotherapy is viable and inverse conformal IMRT with tomotherapy is viable and safe treatment for CSIsafe treatment for CSI
ReferencesParker W Brodeur M, Roberge D, Freeman CR. Treatment of standard and non-standard craniospinal irradiation with helical tomotherapy Int J Radiat Oncol Biol Phys, in press 2009.
Parker W, Filion E, Roberge D, Freeman CR. Intensity-modulated radiotherapy for craniospinal irradiation: target volume considerations, dose constraints, and competing risks. Int J Radiat Oncol Biol Phys 2007;69:251-257
Parker WA Freeman CR A simple technique for craniospinal radiotherapy in the supine position Radiother Parker WA, Freeman CR. A simple technique for craniospinal radiotherapy in the supine position. Radiother Oncol 2006;78:217-222.
Liu M, Carrie C, Parker W, Freeman CR. Comparison of manual and computer-generated customized blocks for whole brain fields used in the treatment of medulloblastoma. Medical and Pediatric Oncology 2002; 38:55-57