1. Scope of Talking
TomoTherapy Overview of Tomotherapy
Tomotherapy Process
Clinical Application
Concerned Issues
Lalida Tuntipumiamorn
Division of Radiation Oncology
Future Direction
Department of Radiology,
Faculty of Medicine, Siriraj Hospital
MAHIDOL UNIVERSITY
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Acknowledgement To Get the Satisfied Dose
Distribution
• Some of materials provided by
-Timothy Holmes- PhD : St Agnes
Cancer Center, Baltimore MD
-Thomas Rockwell Mackie – PhD :
U of Wisconsin and TomoTherapy
Inc.
- Chester Ramsey-PhD : Thompson
Cancer Center, Tenessee , USA
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-Limited Number of Beams and Directions
Cone Beam Non-uniform Intensities
with the Conventional Linac plus MLC -Limited Number of Field Segmentations
Limited Degree of Intensity Level
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Siriraj Radiation Oncolgy

2. Serial Tomotherapy : Peacock system
Fan Beam Intensity TM
Modulation
• Common Name :
Slice Therapy or
Tomotherapy
- Sequential /Serial
Tomotherapy
- Helical Tomotherapy
1994
Conventional Linear Accelerator added with
Special MLC + Couch Control
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Serious Problem in Serial Tomotherapy!
Binary MLC MIMiC:
NOMOS
Maximum Field Size
2 x 20 OR 4 X 20 cm2
Indexing and couch
immobilization device
( CRANE) Over or under dose
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The New IMRT Delivery with
Helical Tomotherapy …….
Couch Indexing Error of as little as
1 mm can increase the total non-
uniformity to as much as 25%
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Siriraj Radiation Oncolgy

3. Concept for Helical Tomotherapy :
Since 1993
CT ring gantry
would be ideal for
Tomotherapy with
the modulated slit
beam using the
bank of fast moving
collimators
Spiral delivery should
improve the hot-spot
or cold spot problem
Thomas Rockwell Mackie at the junction
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Linac is mounted on a slip ring that allow
Helical Tomotherapy is a Fusion of a continuous rotation around the patient (15-60 sec)
Radiation Therapy Linear Accelerator
and a Helical CT Scanner
Independent Primary
Jaws in the Superior-
Inferior Direction
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MLC
TOMO Binary MLC
Characteristic
Optical sensors and
pneumatic driven
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4. Increase Degree
of Freedom Megavoltage CT Imaging
Capability
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projections/
revolution
e
ag
Im o r
CT tect
e
d
Capability of obtaining a CT ,
before , after or even during the
treatment will be possible
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TOMO Beam
Characteristic
Lack of the Flattening Filter
-No scatter caused outside the field
- High dose rate
Helical Tomotherapy
Tomo Beam Characteristic
Geometry
Conical –shaped Profile
Radial Profile
6 MV High Dose Source
(860 MU/min, 1.5 mm
point source) Low penumbra
3.5 MV Low Dose Source
(20 MU/min, 1.5 mm
point source)
Lateral Profile
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5. Dose at Depth More Uniform
MVCT Image Guidance
5 x5 cm Field Size
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MVCT Imaging Quality
High contrast resolution
= 1.2-1.6 mm
Low Contrast resolution =
2-4%
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6. Don’t Forget for the
MVCT Number to
Electron Density
Conversion Table
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Helical Tomotherapy Process
TomoTherpy Process
• Imaging / Contouring
• Planning / Optimizing
• In-room Megavoltage CT Imaging
• Image Registration ( IGRT )
• Treatment Verification
• Treatment Delivery
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Optimization
Create ROI Dose Delivery Capabilities
Set initial value s for Importance
Using maximum
and Penalty
U-shaped tumor likelihood Estimator
Optimization
Total 91,800 pencil
beam were used in
Spinal cord
the optimization
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7. Planned Fluence Sinogram
in Tomotherapy
Leaf Control
Planned Fluence Sinogram
Sinogram Corrected
From optimization process
tongue & groove ,
2D array of energy fluence that corrleate
thread time
between the projection and intensities
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Plan QA
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IGRT
Total delivery time
≅ 30 minutes
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Siriraj Radiation Oncolgy

8. TomoTherapy
vs.
Clinical Application
Only single , 6 MV Photon Beam ?
No Electron Beam ?
Questions Coplanar Only ?
IMRT Only?
Dosimetric/Clinical Advantage ?
How about Integral Dose?
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Dosimetric gain in CI and HI of PTV and sparing of OARs
was significantly obtained in HT vs. Conventional IMRT
But clinical advantage needs furthur investigation
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HT prostate planning generally provided treatment
plans with excellent target homogeneity and
favorable critical structure sparing when compared to
conventional IMRT
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Siriraj Radiation Oncolgy

9. Prostate , Vertebral –body retreatment = PTV Coverage + Sparing
OAR , HT = Linac
Pediatric ethmoid sacroma retreatment =PTV Coverage both OK ,
but HT show a little bit better sparing OAR
Subtle dosimetric difference
But no marked advantage with either system
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SRS
Capability
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Helical Tomo shows larger lower isodose line
volumes, longer treatment time , and can treat
a much larger lesion than Gamma-knife
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Siriraj Radiation Oncolgy

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Dosimetric Advantage from
Tomo but Integral Dose
increase 6.5 %
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Siriraj Radiation Oncolgy

11. TomoTherapy
Integral Dose!!
A Potential Risk Factor for
Secondary Cancer ?
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Integral Dose = Mean Dose x
Volume
TOMO IMRT
6 MV 3DCRT 6 MV IMRT
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AAPM 2007
Same protocol
Adult prostate treatment
Linac vs. Helical Tomo
Pediatric CSI
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TomoTherapy
Some Concerned Issues
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Longer Treatment Time!!
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13. Future of
TomoTherapy
Prepare for Adaptive RT
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Thank You for Your
Attention!
Future Direction
TomoDirect
Discrete -angle
delivery mode
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Siriraj Radiation Oncolgy