External Beam Radiation External Beam Radiation Therapy Special Therapy Special

ProceduresProcedures

Kent A. Gifford, Ph.D., Kent A. Gifford, Ph.D., Acknowledgements to : Karl L. Prado, Acknowledgements to : Karl L. Prado,

Ph.D., Charles Bloch, Ph.D., Peter Balter, Ph.D., Charles Bloch, Ph.D., Peter Balter, Ph.D., Gurpreet Arora, B.S.Ph.D., Gurpreet Arora, B.S.

Department of Radiation PhysicsDepartment of Radiation Physics

Total Body IrradiationTotal Body Irradiation

IndicationsIndications TechniquesTechniques Dosimetry DataDosimetry Data ExamplesExamples

TBI: Clinical IndicationsTBI: Clinical Indications

Preparation for marrow or stem-cell Preparation for marrow or stem-cell implantationimplantation Suppress immune system to prevent Suppress immune system to prevent

rejectionrejection Rid body of tumor cells not reached by Rid body of tumor cells not reached by

chemotherapeutic agents (e.g. CNS)chemotherapeutic agents (e.g. CNS)

half body, adjacentdirect fields

TBI TechniquesTBI TechniquesAAPM Report 17, figure 1.AAPM Report 17, figure 1.

single source,long SSD

source moves horizontally

patient moves horizontally

half body, directand oblique fields

TBI TechniquesTBI TechniquesAAPM Report 17, figure 1.AAPM Report 17, figure 1.

four sources

two horizontal beams

single source, short SSD

two vertical beams

head rotation

MDACC “Classic” TBIMDACC “Classic” TBI

MDACC TBI Techniques:MDACC TBI Techniques:Mick-Radio Nuclear StandMick-Radio Nuclear Stand

Total Skin IrradiationTotal Skin Irradiation

High Dose-Rate Total Skin Electron High Dose-Rate Total Skin Electron (HDTSE-) Treatment: Technique (HDTSE-) Treatment: Technique DescriptionDescription

IndicationsIndications MethodologyMethodology Data / CalculationData / Calculation Dose Verification (TLD)Dose Verification (TLD)

MDACC TSEI techniqueMDACC TSEI technique(modified Stanford technique)(modified Stanford technique)

2 angled beams (90°±23°) for 2 angled beams (90°±23°) for uniform coverage and reduced uniform coverage and reduced total body dosetotal body dose

patient is 25 cm behind lucite patient is 25 cm behind lucite plateplateimproved dose uniformityimproved dose uniformity(6 fields w/plate 8 fields (6 fields w/plate 8 fields w/o plate, Holt JG, Perry DJ. w/o plate, Holt JG, Perry DJ. Med. Phys.Med. Phys. 99:769-776(1982)):769-776(1982))

increased dose to self increased dose to self shielded areas by diffusionshielded areas by diffusion

6 positions, every 606 positions, every 60°°

2 angled beams (90°±23°) for 2 angled beams (90°±23°) for uniform coverage and reduced uniform coverage and reduced total body dosetotal body dose

patient is 25 cm behind lucite patient is 25 cm behind lucite plateplateimproved dose uniformityimproved dose uniformity(6 fields w/plate 8 fields (6 fields w/plate 8 fields w/o plate, Holt JG, Perry DJ. w/o plate, Holt JG, Perry DJ. Med. Phys.Med. Phys. 99:769-776(1982)):769-776(1982))

increased dose to self increased dose to self shielded areas by diffusionshielded areas by diffusion

6 positions, every 606 positions, every 60°°

MDACC TSEI techniqueMDACC TSEI technique(modified Stanford technique)(modified Stanford technique)

ANT

LPORPO

1st day of cycle

POST

RAOLAO

2nd day of cycle

laser

Stanford dual beam techniqueStanford dual beam technique

feet straight ahead or pointed slightly feet straight ahead or pointed slightly outwards for better balanceoutwards for better balance

elbows at or above shoulder levelelbows at or above shoulder level arms parallel to the scatter platearms parallel to the scatter plate

QA - Patient TLD’sQA - Patient TLD’s

TLD’s are taped to the patient’s skin TLD’s are taped to the patient’s skin and irradiated for one cycle (12 and irradiated for one cycle (12 beams)beams)

reference TLD’s are irradiated using reference TLD’s are irradiated using a 10x10 cma 10x10 cm22 field of 9 MeV electrons field of 9 MeV electrons atat2.0 cm depth (100 cm SSD) in an2.0 cm depth (100 cm SSD) in anacrylic phantomacrylic phantom

TLD’s are taped to the patient’s skin TLD’s are taped to the patient’s skin and irradiated for one cycle (12 and irradiated for one cycle (12 beams)beams)

reference TLD’s are irradiated using reference TLD’s are irradiated using a 10x10 cma 10x10 cm22 field of 9 MeV electrons field of 9 MeV electrons atat2.0 cm depth (100 cm SSD) in an2.0 cm depth (100 cm SSD) in anacrylic phantomacrylic phantom

SRS: Available Systems-SRS: Available Systems-

Gamma KnifeGamma Knife Radionics Xknife/XplanRadionics Xknife/Xplan BrainlabBrainlab CyberknifeCyberknife Others (many “homemade”)Others (many “homemade”)

Delivery techniquesDelivery techniques

201 intersecting beams (Gamma 201 intersecting beams (Gamma Knife)Knife) spherical dose distributionsspherical dose distributions

Arcs with circular collimators (1-4 cm)Arcs with circular collimators (1-4 cm) ellipsoid dose distributionsellipsoid dose distributions

Multiple fields, shaped with miniature Multiple fields, shaped with miniature MLCMLC arbitrary dose distributions arbitrary dose distributions IMRTIMRT

Stereotactic RadiosurgeryStereotactic Radiosurgery

Elimination of Elimination of motion & setup motion & setup errors means errors means smaller field size smaller field size can be usedcan be used

Reduction in field Reduction in field size allows higher size allows higher dose per fraction, dose per fraction, and reduction in and reduction in number of fractions number of fractions (1 to 5)(1 to 5)

Large dose to small Large dose to small lesions with lesions with minimal dose to minimal dose to surrounding tissue.surrounding tissue.

Single fraction Single fraction ““Out-of-town” Out-of-town”

patientspatients Patients in poor Patients in poor

healthhealth Other patients who Other patients who

might be burdened might be burdened by protracted by protracted treatment.treatment.

Bloch, Ph.D.

SRS QASRS QA

TreatmentTreatment

Typically 5 arcs, about 60 degree Typically 5 arcs, about 60 degree each.each.

5-10 MU/degree 5-10 MU/degree 300 - 600 MU/arc. 300 - 600 MU/arc. 300 MU/min 300 MU/min 1-2 minutes per arc. 1-2 minutes per arc. Total treatment is 5-10 min of beam Total treatment is 5-10 min of beam

time.time. Room entries between arcs to move Room entries between arcs to move

couch and re-check patient couch and re-check patient alignment.alignment.

Gating Study-Left BreastGating Study-Left Breast

By Gurpreet Arora, B.S.

PROBLEM: Thoracic tumors PROBLEM: Thoracic tumors movemove

Planning on the three CT setsPlanning on the three CT sets

CT at Inspiration CT at Expiration CT during Free Breathing

Combined to form ITVs

By Peter Balter, Ph.D. and Lei Dong, Ph.D.

The GE system for 4D The GE system for 4D scanningscanning

Uses Varian RPMto monitor respiration

GE PET/CT (can be used on any GE CT scanner)

By Peter Balter, Ph.D.