External Beam Radiation Therapy Special Procedures Kent A

External Beam Radiation Therapy Special Procedures Kent A. Gifford, Ph. D. , Acknowledgements to : Karl L. Prado, Ph. D. , Charles Bloch, Ph. D. , Peter Balter, Ph. D. , Gurpreet Arora, B. S. Department of Radiation Physics

Total Body Irradiation n n Indications Techniques Dosimetry Data Examples

TBI: Clinical Indications n Preparation for marrow or stem-cell implantation Suppress immune system to prevent rejection n Rid body of tumor cells not reached by chemotherapeutic agents (e. g. CNS) n

TBI Techniques AAPM Report 17, figure 1. source moves horizontally single source, long SSD half body, direct and oblique fields patient moves horizontally half body, adjacent direct fields

TBI Techniques AAPM Report 17, figure 1. two vertical beams four sources single source, short SSD two horizontal beams head rotation

MDACC “Classic” TBI

MDACC TBI Techniques: Mick-Radio Nuclear Stand

Total Skin Irradiation n n High Dose-Rate Total Skin Electron (HDTSE-) Treatment: Technique Description Indications Methodology Data / Calculation Dose Verification (TLD)

MDACC TSEI technique (modified Stanford technique) n 2 angled beams (90°± 23°) for uniform coverage and reduced total body dose n patient is 25 cm behind lucite plate nimproved dose uniformity (6 fields w/plate � 8 fields w/o plate, Holt JG, Perry DJ. Med. Phys. 9: 769 -776(1982)) nincreased dose to self shielded areas by diffusion n 6 ° positions, every 60

MDACC TSEI technique (modified Stanford technique) 1 st day of cycle 2 nd day of cycle laser ANT RPO POST LPO LAO RAO

Stanford dual beam technique n n n feet straight ahead or pointed slightly outwards for better balance elbows at or above shoulder level arms parallel to the scatter plate

QA - Patient TLD’s n n TLD’s are taped to the patient’s skin and irradiated for one cycle (12 beams) reference TLD’s are irradiated using a 10 x 10 cm 2 field of 9 Me. V electrons at 2. 0 cm depth (100 cm SSD) in an acrylic phantom

SRS: Available Systemsn n n Gamma Knife Radionics Xknife/Xplan Brainlab Cyberknife Others (many “homemade”)

Delivery techniques n 201 intersecting beams (Gamma Knife) n n Arcs with circular collimators (1 -4 cm) n n spherical dose distributions ellipsoid dose distributions Multiple fields, shaped with miniature MLC n n arbitrary dose distributions IMRT

Stereotactic Radiosurgery n n Elimination of motion & setup errors means smaller field size can be used Reduction in field size allows higher dose per fraction, and reduction in number of fractions (1 to 5) n n Large dose to small lesions with minimal dose to surrounding tissue. Single fraction n “Out-of-town” patients Patients in poor health Other patients who might be burdened by protracted treatment. Bloch, Ph. D.

SRS QA

Treatment n n n Typically 5 arcs, about 60 degree each. 5 -10 MU/degree 300 - 600 MU/arc. 300 MU/min 1 -2 minutes per arc. Total treatment is 5 -10 min of beam time. Room entries between arcs to move couch and re-check patient alignment.

Gating Study-Left Breast By Gurpreet Arora, B. S.

PROBLEM: Thoracic tumors move

Planning 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 4 D scanning GE PET/CT (can be used on any GE CT scanner) Uses Varian RPMÔ to monitor respiration By Peter Balter, Ph. D.