The Tomotherapy
Experience at Advocate
Good Samaritan Hospital
Mark Pankuch
Today’s Discussion

The History of Radiation at Good Samaritan

Quick Overview of the Tomotherapy Unit

Treatment population and Statistics of our experience

Results from Shielding

Comparison of plans
Advocate Good Samaritan

Treated first patient on May 13, 2002

Single Linac Vault with a Seimens Primus
Hand me down GE CT scanner
from radiology


Paper-less / Film-less department
Advocate Good Samaritan

Within two years reached capacity for a single
Linac department

Began offering HDR treatments

Strong administrative and physician support for
expansion
Advocate Good Samaritan

New Vault was needed

Doubling current patient volumes appeared as
an over estimation for potential volume

Present day IGRT with OBI not commonly
available
What did Tomotherapy Offer that
Good Sam was missing?
 IGRT
 “Top
End” IMRT
The Answer For Good Sam?
Tomotherapy
tomotherapy_T1.mov
Tomotherapy MLC
MLC’s Oriented in the Sagital Plane
The Treatment Process





Patient is set up on table to moveable lasers (2
min)
High energy CT scan performed in the Tx
Position (3 Min)
New images are fused with planning CT images
(3 Min)
Adjustments are made for patient position (2
min)
Treatment is delivered (10 Min)
Of Special Note on Hardware:

No flattening filter

Output ~ 900 MU / min

Tx = 10,000 MU

MLC’s very, very fast (us)

Capable of MVCT export

MVCT ~ 2-3 cGy
Planning System





Single workstation for planning
Cluster of 16 computers, w/ dual processors for
computing.
Optimizations done on “beamlets” that can be
calculated overnight
Very few contouring tools, need another system
for contouring and fusions
No planning review station, system not
multitasking
What type of patients have we treated?
Tomotherapy Patient Breakdown to Oct 2006
Abdomen
Spine
Female Pelvis
Thorax
Head / Neck
Brain
Male Pelvis
0
10
20
30
Number of Patients
40
50
60
Tomotherapy

Not optimal for all treatment sites

Rotational / Helical Treatments

Need the capability to give low doses to large
areas of normal tissues

Ability of “cave out” doses

Very conformal, with good dose drop off
Simultaneous Boost
DQA

Tomotherapy Supplied Phantoms

Film and Point dose taken on every patient

Planning system has built-in QA tools

Film analysis evaluated by calculating gamma index
(Low et.al., Med Phys 25, 1998)


3% Dose
3mm DTA
40
DQA Results For First 143 Procedures
30
20
10
0
4.0 to 3.5 3.5 to 2.5 2.5 to 1.5 1.5 to 0.5 0.5 to -0.5 -0.5 to -1.5 -1.5 to -2.5 -2.5 to -3.5 -3.5 to -4.0
% Dif erence from Expected
QA






cGy / MU
cGy / min
Lasers coincidence
Table Accuracy
Field Consistency
MLC accuracy
Clinical Outcomes

Pelvis patients decreased side effects

Prostate patients no side effects (78Gy)

Brain Patients get ring shape hair loss

Head / Neck patients
Still have skin reactions
 Considerably reduces reaction in mouth
 Need more time for long term results

Skin Reactions
Shielding Considerations

Large majority of shielding needed because of
leakage

Scatter Radiation

Primary beam
Shielding Considerations


X = W * U * T * ISF
Workload:
30 Patients/day
 10 min Tx time
 880MU/min
 66,000,000 MU/year





Usage Factors = 1
Occupancy Factor as usual
Occupational areas kept to 10% of limits
ISF from 3 meters
Shielding Considerations, Leakage

Leakage levels obtained from chart like CT scanner

Leakage was measured and plotted as a function of
position around the gantry and radial distance

All leaves closed for measurements

Leakage fraction at 3 meters was used

ISF from 3 meters
Shielding Considerations, Scatter

Scatter levels a function of position around gantry

Greatest at opening of couch

With all leaves open, can be 186% of leakage exposure

Clinically, the exposure can be reduced by a factor of
16

Maximum % scatter increase = 12%, I used 15%
Shielding Considerations, Primary

Unit has a built in Primary Beam Block, 13cm Pb

The primary beam was 6.3% of the overall radiation at
2.5 cm from the isocenter

Clinically, the exposure can be reduced by a factor
similar to scatter due to closed leaves

I ignored reduction factor, and increased exposure by
6.3%.
Shielding Results
North
Wall
South
Wall
West
Wall
East
Wall
Calculated
Exposure
(mR/hr)
0.163
0.042
0.017
Measured Exposure
(mR/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%
17%
54%
12%
5%
3%
12%
38%
Plan Comparison

Tomotherapy

CMS XIO, Step and Shoot

Varian Eclipse, Sliding Window
Rt Parotid
100%
90%
80%
Volume
70%
60%
50%
40%
30%
Tomotherapy
20%
XIO
Eclipse
10%
0%
0
10
20
30
Dose (Gy)
40
50
60
Lt Parotid
100%
90%
80%
Volume
70%
60%
50%
40%
30%
Tomotherapy
20%
XIO
Eclipse
10%
0%
0
10
20
30
Dose (Gy)
40
50
60
Spinal Cord
100%
90%
80%
Volume
70%
60%
50%
40%
30%
Tomotherapy
20%
XIO
Eclipse
10%
0%
0
10
20
30
Dose (Gy)
40
50
60
Brain Stem
100%
90%
80%
Volume
70%
60%
50%
40%
30%
Tomotherapy
20%
XIO
Eclipse
10%
0%
0
10
20
30
Dose (Gy)
40
50
60
PTV
100%
90%
80%
Volume
70%
60%
50%
40%
30%
Tomotherapy
20%
XIO
Eclipse
10%
0%
0
10
20
30
Dose (Gy)
40
50
60
Which is best??

Depends ……..
Workload
 Needs
 Patient sites


Many systems now have IGRT


Where is IGRT going?
No Breath Gateing on Tomotherapy

Where is gateing doing?
In the future for Tomotherapy

Adaptive treatments

Live time optimizations

Conductivity with IMPAC

Live time QC

Breath Coaching Methods
Questions ??

Thanks for your attention!

Free tour of the Cancer Center after lunch

Questions ???
Descargar

The Tomotherapy Experience at Advocate Good