Total Body Irradiation (Ttbi) Treatments Using A Tomotherapy Unit

Total Body Irradiation (TTBI) treatments using a Tomotherapy unit:

Feasibility, advantages, problems and prospects

1G.Guidi, 2M.Amadori, 2P.Antognoni, 1E.Cenacchi, 1L.Morini, 1L.Boni, 1P.Ceroni, 2G.Tolento, 2G.De Marco, 2S.Scicolone, 2M.Parmiggiani, 2P.Giacobazzi, 2S.Pratissoli, 2F.Titone, 2B.Lanfranchi, 1C.Danielli,

2F.Bertoni, 1T.Costi, *M.Corni

1 Medical Physics 2 U.O. Radiation Oncology

Azienda Ospedaliero - Universitaria di Modena - Policlinico

Acknowledges:

*In memory of Marco Corni, whose contribution of professionalism, consistency, helpfulness and friendliness are been crucial for development, obtaining and comparing the present results.

diapositiva 2G.Guidi, M.Amadori, M.Corni et.al.

PLAN PARAMETERS – COMPARISON (e.g. Size of the patient : Big)

Field Width Pitch MFGantry

RotationsDelivery Time DVH Highlight

5 cm 0.385 2.5 58 1927 secV12=93% Body (DMax=14Gy)V8<15% Lungs



2.5 cm 0.875 1.8 60 3155 secV12=93% Body(DMax=15Gy)V8>40% Lungs

•V8<1% Dummy Lungs (Lungs contracted laterally by 0.5cm to guaranties the irradiation of the body during the breathing)•V9<1% Lens•Dose Prescription 12Gy @ 93%Vol•Other MF (e.g MF = 3.5, 5, 7) and Pitch (e.g. P=0.35, 0.287, 0.213) are applicable for optimization but the system is crashed during the Final Dose Calculation or the “Get Full Dose”


ISSUE AND CONSIDERATION

• FIELD WIDTH 2.5 CM– Decreasing of the target dose distribution– Increasing of the treatment time– Increasing of the lungs doses– Increasing of the lungs doses– Arms and lateral extremity receive less

dose than prescription due to the rotation– Lung receive more doses– Maximum of dose > 115% Dp

• LEGS– Marker at 1/3 of the femur is used to

define the beams or to avoid any beams overlap ore over dosage

– Inferior extremity are treatable using• 2 opposed filed at the Linac with

calculation at the middle-plane• Using Helical treatment is also

possible to treat• Probably using Direct Beam Option

could be possible to save time


PAEDIATRIC PATIENT

• Paediatric Patient : Small (<150cm)• Single Plan• Beam-ON: 1150 sec• Dose Distribution:

– Prescription 12 Gy @ 93%Vol– Max Dose <110% Dp – Lung : V8 > 20%– Lens < 3Gy

• Integral doses and high dose rate must be evaluate before to treat paediatric patients with this techniques

• Special case not treatable using standard TBI could be submitted or evaluated by ethic committee, before to be treatable using Tomotherapy TBI

• Many open issue at the moment must be consider before to treat paediatric patients, but the techniques could be important, especially considering the comfort, accuracy and the speed of the procedures


SMALL PATIENTS

• Size Patient : Small• Beam-ON: 1644 sec• 2 Plans

– Body (Head - 1/3 Femur)– Legs (From 1/3 Femur)

• Beam-ON: 1644 sec• Dose Distribution:

– Prescription 12 Gy @ 90%Vol

– Max Dose <110% Dp– Lung : V8 < 40%– Dummy Lung : V8 < 10%


DQA (Delivery Quality Assurance)

• DQA– 3 Type

• Head (Eyes)• Lung area• End Region of the treatment to guarantee

the complete treatment of the patient • Cheese Phantom

– Gafchromic + Ion Chamber • Map Comparing

– Vidar Dosimetry Pro 16– Gamma Index (3% @ 3mm)

• Actual results <1% of differences• Dose Profile evaluations

– Matching of the profile on X and Y direction


INNOVATIVE TECHNIQUES – (TLI AND TMI)

TMI (Total Marrow irradiation) or TLI (Total Lymphoid Irradiation) are similarly applicable using Helical Treatment


RESEARCH (DIODE QA) – PRELIMINARY RESULTS FOR HELICAL TREATMENT

Diode courtesy of Tema Sinergie


ISSUES, LIMITATION AND TRICK

• Maximum Gantry rotation = 60• Long beamlet time > 12 h/ plan using the DC2/DC3 Cluster• Long Optimization Time ~ 1-1.5min per iteration ( 200-300 iterations per plan)• Image resample 256 x 256 can completely adequate for small volume (e.g. lens)• Dose Matrix Volume (0.642cm) – Why should I use Gamma Index of 3mm @ 3%?• Prescription?

– 12 Gy @ 93% of the volume– Dmean = 12 Gy (Easy way to plan and obtain DVH results, but a careful analysis of the volume is

necessary)• Many immobilization devices and setup are been explored, but the most reproducible is the supine

position with a Vacuum device. The patient head should be fixed but the mouth should be freedom• 20-25 minutes to “Get the full doses” • 20-25 minutes to calculate the final dose• 3 h to prepare the 3 DQA Plans (Head, Lung, Cauda)• 3 h of beams to perform the QA at the machine (MVCT + DQA for each DQA Plan)• Liver, spleen and heart should be used as a Target, during the plan optimization, to dose the body

adequately close to the lungs, otherwise some area will be significantly under dosed• Hot-Spot must be controlled, but increasing the MF could be not possible to deliver the plans due to the

machine constrain (Time, Gantry Speed Rotation, Beam undeliverable)• Using the prescription at the mean dose the plan is very easy and fast but few area of the marrow or the

body could be completely under dosed (Preliminary results)


CONCLUSIONSTTBI (Tomotherapy TBI) A FEASIBLE AND PROMISE TECHNIQUE FOR THE FUTURE

• The simulation of the patients has demonstrated the feasibility and advantages of treatments TTBI– 20-30min of beam-on– Supine position– Reposition the patient through the use of IGRT techniques– The technology allows to treat patients, with clear benefits identified in the best coverage of the target

and the OAR sparing• We have identified some problems and limits to the research subject.

– Some considerations, still subject of evaluation• Immobilization systems• Computation time• DQA-Quality• Vivo Dosimetry using Diode or Mosfet• TTBI Dose Rate (800 cGy / min) compared with conventional treatments TBI (10-40 cGy / min).

– Features of research• Irradiate mice

– To evaluate teh high dose rate effect in lung and OARs– To highlight changes on stem cells and influence on cells in transit through the blood.– Explore differential fractionation scheme (eg, 16-18Gy) based on radiobiological evidences

• Similarly to the results of Total Marrow Irradiation (TMI) and Total lymphoid Irradiation (TLI), the Tomotherapy TBI (TTBI) could be considered an innovative technique applicable to the clinical routine.

• Finally some doubts are expressed in emergency management, where you may need to find a Tomotherapy backup or develop a similar treatment, to ensure continuity therapeutic even during maintenance of the equipment.

Total Body Irradiation (Ttbi) Treatments Using A Tomotherapy Unit

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