A Cylindrical 3D Water
Scanner –
First Experiences and Results
Karen Feyen
AZ St-Maarten Duffel, Belgium
A.Z. Sint-Maarten – RT
department - Linacs
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SLi 18 (installed 2002), conformal treatments
• 6MV/15MV photons
• 5 electron energies
• MLCi with 1 cm leaves, max field size 40 cm x
40 cm
• Short physics duct from control area to linac
technical area : no fixed cabling
Synergy platform (installed 2007), IMRT
• 6MV/15MV photons
• Beam modulator with 4 mm leaves, max field
size 21 cm x 16 cm
• Physics duct about 25 m, fixed cabling and
connectors in bunker and control area
EPID based IGRT on both systems
• Iview GT
• Vanderwilt remote table control
• Offline/online protocols, no CBCT
± 1000 new patients/year
A.Z. Sint-Maarten – RT
department
• CT simulation
•
– Siemens Definition CT (medical imaging
department)
– A2J CT-Sim lasers
– Medio 50 CP simulator used for some palliative
Medio 50 CP simulator
– Some palliative treatments
• Main TPS = Pinnacle
• Brachy:
– Nucletron HDR / Oncentra Masterplan
– PBT inhouse/other centers : Bard / Variseed
• Other equipment
• More than 40 PC’s and workstations for about 20
•
people
A lot of cables and a lot of heat
Dosimetry material
• Abolute Dosimetry
– FC-65-G cylindrical reference
chamber
– PPC-40 parallel plate chamber
– Dose-1 electrometer
– WP1D motorised
waterphantom
• Machine QA - SNC
– Switching to IC-profiler or
Profiler 2 (still to be decided)
– Daily QA3 (wireless)
• Patient QA
– Matrixx
– Invidos
• Brachy QA
– Unidos E and Sourcecheck
(PBT)
– Nucletron/Standard Imaging
and PTW well chamber (HDR)
3DS – How did we decide ?
• Motivation :
• WP700 system dates from 1989 and was in
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need for replacement
“New” project : commission Sli 18 for IMRT,
we wanted this done without doubts about
the measurement data quality
Increase time efficiency of water tank
measurements
Reduce threshold to use of water tank
• Obtained budget approval 04/2010
3DS – How did we decide ?
• Requirements specifications (highlights):
– Must
– qualitatively perform as well or better than the old
system (of course)
– work with current detectors
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handle current data
export to Pinnacle
TMR/TPR capable
Before purchase, we must work with the system to
get the look and feel
– Should
– more user friendly
– easier/faster to setup
3DS – How did we decide ?
• On site visits at nearby centers May-June 2010
• PTW MP3-M / Mephysto MC2
• IBA Blue Phantom / OmniPro Accept v7
 both very qualitative and well established systems
 IBA blue phantom and OmniPro Accept v7 seemed logical
successor to our current system
• No clinical 3DS system available in Europe at
•
that time
=> Visit to SNC factory
3DS – How did we decide ?
• Visit SNC factory
• First view on a functional prototype
• Opportunity to talk to several
people involved in the development
of hardware and software
• Enthousiastic team determined
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to deliver a innovative and
qualitative product, eager to
take input from (potential) users
Good overview of hardware,
software
But system released early 2011,
which was later than we hoped
for
3DS – How did we decide ?
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Competitive offers from all parties
Open communication with all distributors
Detailed comparison of all specs
Choice between solid well established system and young
innovative system
Very much attracted by the novelties of the 3DS system
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Auto setup : objective, time saving (?),
One-cable connection : fast, less fragile
Measurement database instead of files
Layered processing with rollback options
Consistent detector orientation (certainly has a positive effect
but not thoroughly evaluated at that time)
3DS – How did we decide ?
• But no reference and no opportunity to test at that time
=> Test site agreement
– Gain experience with new system before it is released
– Opportunity to provide input for new features (wish list !)
– Possibly start measurements with test system if all works earlier
than planned (optimism is good)
3DS – the system
3DS – the system
• Main hardware differences :
– Cylindrical geometry
– movement in (r, theta, z) instead of
(x, y, z)
– Look less bulky
– less water needed, less weight
– scan range is the same for all scans
( i.e. not larger for diagonals) but is
large (standard 50 cm)
– larger scan range possible with
special detector holder
Mechanical Testing
• Relative positioning accuracy using laser
pointer and chart paper
– Ring drive
– Vertical drive
– Diameter drive
• Done using controls box – without auto
setup measurements (dry tank)
• Leveling accuracy : ≤ 0.1° (accuracy of
our digital level)
• Plumb line of vertical drive using laser
level (construction)
3DS – Setup
• Platform setup procedure:
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Connect power and PDI
Calibrate motors platform and tank
Put tank approximately right
Fill tank and adjust height to correct SSD
Leave bunker and run auto setup procedure
• Tank Leveling
• Ring center determination
• Tank center determination and tank adjustment
• Ring angle offset determination
• Hysteresis measurement
3DS – Auto setup
3DS – Auto setup – calibrate
platform
• Platform leveling and x- y- motors need to be
•
calibrated before they can be used
Best done before aligning the system with the
crosswire
3DS – Auto setup – calibrate
platform
• Tank ring drive, diameter drive and vertical drive
home positions are determined
3DS – Auto setup
3DS – Auto setup – ring center
• Diameter drive is mounted eccentrically to
allow for the detector to be in the center
3DS – Auto setup – Ring center
• To keep the detector in the mechanical
center of the tank, it must be positioned
correctly
• In the direction orthogonal to
the diameter drive -> specific
distance when mounting the
detector
• In the direction along the
diameter drive -> done by
the system
3DS – Auto setup – Ring center
• If the ring center would not be
determined correctly, the detector
would rotate on a circle around the
mechanical center
3DS – Auto setup
• Tank adjust
• The isocenter/beam center is determined from
• Inline and crossline scan at collimator 0°
• Inline and crossline scan at collimator 180°
• The tank position is shifted to match the beam
center
• Angle offset
• The angle of the tank is aligned with the
collimator
3DS – Auto setup Checks
• Check after auto setup during test
period:
• Visually check position of detector vs
crosswire
• Take scans at cardinal angles
• Check correct position of beam edges
• => Part of factory testing
3DS – Setup -timings
Item
Timing (approx.)
Calibrate platform
1’30”
Calibrate tank
45”
Fill tank (old reservoir)
7’
Tank leveling
4’30”
Ring/Tank center & adjust
7’
Ring angle offset
1’45”
Hysteresis
1’30”
3DS – Scan database
• Scans are grouped in projects – can be
added to multiple projects
• DB can be searched by building logical
expressions of various scan parameters
• Scan lists can filtered
• Scans lists can be grouped
3DS – Scan database - projects
3DS – Scan database searches
3DS – Scan database filtering
3DS – Scan database filtering
3DS – Scan layered processing
3DS – Scan layered processing
Experiences – Detectors used
Experiences – Easy setup
Results – Large scan range
• The standard scan range of 50 cm can be extended
using the radial offset detector holder
• 40 cm x 40 cm, d=30cm, 5 cm extra => 62cm scan
Results – Large scan range
• Radial offset detector offsets the detector from the
center of the carriage, brings it closer to the tank wall
• Diameters driver rotates by 180° when detector is in the
center
Results – Consistent detector
orientation
• The cylindrical design
ensures a consistent
orientation of the
detector : the motion
always occurs
transverse to the axis
of the detector
Results – Consistent detector
orientation
• Intuitively important for
• extended detectors
• detectors with different dimensions
along their respective axis
• Tested with 3 types of detectors
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• elongated IC
• “spherical” IC (CC13)
• diode
Compared scans with axis
• transverse to motion
• along the direction
Results – Consistent detector
orientation – elongated IC
Results – Consistent detector
orientation – elongated IC
Effect clearly visible
Results – Consistent detector
orientation – CC13
Results – Consistent detector
orientation – CC13
Effect present but less visible
Results – Consistent detector
orientation – diode
Results – Consistent detector
orientation – diode
Effect invisible
Results – Evaluation of scan
parameters
• Set of scans for various field sizes and
various scan settings – CC13
Results – Evaluation of scan
parameters
• Set of scans for various field sizes and
various scan settings – Edge (diode)
Results – Detector choice –
small fields
• Set of scans for
various
detectors and
optimal scan
settings
• “Sharp” vs noisy
Results – Detector choice –
large fields
• Set of scans for
various
detectors and
optimal scan
settings
• “Sharp” vs noisy
Results – Scans with offset
• Achieved by either
• Software controlled shift of platform (offsets ~ 1cm)
• By combination of radial and angular movement (larger offsets)
Results – Scans with offset
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Check off-axis shift
Collimator 45°
Scan with no offset /
Scan with 1 cm offset
Results – Scans with offset
Edge -
0 cm
offset
1 cm
offset
delta
cm
7.02
6.1
0.92
6.07
0.92
Edge + 6.99
• Check detector position ?
Results – Currently performing
commissioning measuring
Results – Currently performing
commissioning measuring
Summary of my findings
• 3DS is a nice innovative system to work with : no more
dreading to use it
– Less bulky, less heavy, practical design
– Auto setup : objective, fast(er)
– One-cable connect
– Database of measurement : very helpful during comissioning
– Layered processing
=> Faster, more frequent use
• Still being optimised and developped further based on
user feedback => real strength of SNC
Acknowledgements
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My colleague
physicists, for all extra
work during evenings
and weekends:
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Natalie Bal
Charlotte Bauwens
Our department head
dr. Ph. Spaas
Thank you !
3DS – the system
3DS – the system