The Tomotherapy Experience at Advocate Good Samaritan Hospital

The Tomotherapy Experience at Advocate Good Samaritan Hospital Mark Pankuch

Today’s Discussion n The History of Radiation at Good Samaritan n Quick Overview of the Tomotherapy Unit n Treatment population and Statistics of our experience n Results from Shielding n Comparison of plans

Advocate Good Samaritan n Treated first patient on May 13, 2002 n Single Linac Vault with a Seimens Primus Hand me down GE CT scanner from radiology n n Paper-less / Film-less department

Advocate Good Samaritan n Within two years reached capacity for a single Linac department n Began offering HDR treatments n Strong administrative and physician support for expansion

Advocate Good Samaritan n New Vault was needed n Doubling current patient volumes appeared as an over estimation for potential volume n Present day IGRT with OBI not commonly available

What did Tomotherapy Offer that Good Sam was missing? n IGRT n “Top End” IMRT

The Answer For Good Sam?

Tomotherapy

Tomotherapy MLC

MLC’s Oriented in the Sagital Plane

The Treatment Process Patient is set up on table to moveable lasers (2 min) n High energy CT scan performed in the Tx Position (3 Min) n New images are fused with planning CT images (3 Min) n Adjustments are made for patient position (2 min) n Treatment is delivered (10 Min) n

Of Special Note on Hardware: n No flattening filter n Output ~ 900 MU / min n Tx = 10, 000 MU n MLC’s very, very fast (us) n Capable of MVCT export n MVCT ~ 2 -3 c. Gy

Planning System Single workstation for planning n Cluster of 16 computers, w/ dual processors for computing. n Optimizations done on “beamlets” that can be calculated overnight n Very few contouring tools, need another system for contouring and fusions n No planning review station, system not multitasking n

What type of patients have we treated?

Tomotherapy n Not optimal for all treatment sites n Rotational / Helical Treatments n Need the capability to give low doses to large areas of normal tissues n Ability of “cave out” doses n Very conformal, with good dose drop off

Simultaneous Boost

DQA n Tomotherapy Supplied Phantoms n Film and Point dose taken on every patient n Planning system has built-in QA tools n Film analysis evaluated by calculating gamma index (Low et. al. , Med Phys 25, 1998) n n 3% Dose 3 mm DTA

QA c. Gy / MU n c. Gy / min n Lasers coincidence n Table Accuracy n Field Consistency n MLC accuracy n

Clinical Outcomes n Pelvis patients decreased side effects n Prostate patients no side effects (78 Gy) n Brain Patients get ring shape hair loss n Head / Neck patients Still have skin reactions n Considerably reduces reaction in mouth n Need more time for long term results n

Skin Reactions

Shielding Considerations n Large majority of shielding needed because of leakage n Scatter Radiation n Primary beam

Shielding Considerations X = W * U * T * ISF n Workload: n 30 Patients/day n 10 min Tx time n 880 MU/min n 66, 000 MU/year n Usage Factors = 1 n Occupancy Factor as usual n Occupational areas kept to 10% of limits n ISF from 3 meters n

Shielding Considerations, Leakage n Leakage levels obtained from chart like CT scanner n Leakage was measured and plotted as a function of position around the gantry and radial distance n All leaves closed for measurements n Leakage fraction at 3 meters was used n ISF from 3 meters

Shielding Considerations, Scatter n Scatter levels a function of position around gantry n Greatest at opening of couch n With all leaves open, can be 186% of leakage exposure n Clinically, the exposure can be reduced by a factor of 16 n Maximum % scatter increase = 12%, I used 15%

Shielding Considerations, Primary n Unit has a built in Primary Beam Block, 13 cm Pb n The primary beam was 6. 3% of the overall radiation at 2. 5 cm from the isocenter n Clinically, the exposure can be reduced by a factor similar to scatter due to closed leaves n I ignored reduction factor, and increased exposure by 6. 3%.

Shielding Results North Wall South Wall West Wall East Wall Calculated Exposure (m. R/hr) 0. 163 0. 042 0. 017 Measured Exposure (m. R/hr) 0. 288 0. 012 Ratio of Measured / Calculated 141% Ratio of Measured / Required 58% Ceiling Door 0. 009 0. 058 0. 278 0. 005 0. 013 0. 012 0. 188 22% 26% 117% 54% 12% 5% 3% 12% 38%

Plan Comparison n Tomotherapy n CMS XIO, Step and Shoot n Varian Eclipse, Sliding Window

Which is best? ? n Depends ……. . Workload n Needs n Patient sites n n Many systems now have IGRT n n Where is IGRT going? No Breath Gateing on Tomotherapy n Where is gateing doing?

In the future for Tomotherapy n Adaptive treatments n Live time optimizations n Conductivity with IMPAC n Live time QC n Breath Coaching Methods

Questions ? ? n Thanks for your attention! n Free tour of the Cancer Center after lunch n Questions ? ? ?