80525-02 IMSure Physics Data Guide

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Machine and Physics Data Guide
STANDARD IMAGING, INC.
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Middleton, WI 53562-1461
May / 2008 ©2008 Standard Imaging, Inc.
DOC #80525-02
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TEL 608.831.0025
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www.standardimaging.com
IMSure QA Machine Data
Most data required for IMSure QA is similar to that normally acquired in the
commissioning process of a linear accelerator. With all data readily available an entire dual energy machine can be set up in as little as a half hour.
The items needed for machine data configuration are listed below.
Items like machine names, configuration, tray factors and calibration specifications can be entered directly in the Physics Module. Tabular data such
as TMR, PDD, OCR, OF and Sc must be imported from CSV format files
as specified at the end of this guide. Some consistency rules apply to the
imported data as listed in Table B.
Other machine parameters such as jaw distances, rotation configurations,
and average MLC leaf leakages are needed as defined in Table A. Jaw
distances are common for all available machines and can be noted from
our sample data or from Table C on page 4. Leaf leakages are also fairly
uniform from machine to machine, and this parameter may also be used to
make small corrections in final IMSure QA IMRT results.
As many photon and electron energies along with their respective wedges
and cones can be entered (i.e., both upper and lower wedges, even oldfashioned split wedges and half beam blocks).
Table A: Machine Names, Configurations, Parameters and Data used
in IMSure QA
Names and Configurations
Cone Size
The numeric value of the cone that describes it’s
dimension in both the X and Y directions (in cm)
Machine Geometry – IMSure QA defaults to the IEC 1217 Convention
Base Gantry
Rotation
IEC 1217 Convention describes 0 degrees as the
Gantry pointing down. If your system describes
0 degrees as the Gantry pointing up you would
insert 180 to let IMSure QA know that your coordinate system is set 180 degrees from the IEC
standard.
Gantry Rotation
Direction
IEC 1217 Convention describes Gantry rotation
increasing clockwise (CW) if facing the Gantry
from the foot of the couch. 90 degrees will be with
the head of the accelerator to the right if facing the
gantry from the foot of the couch.
Base Collimator
Rotation
IEC 1217 Convention describes 0 degrees as
pointing towards the foot of the couch. If your
system describes 0 degrees as pointing towards
the Gantry you would insert 180 to let IMSure
QA know that your coordinate system is set 180
degrees from the IEC standard.
Collimator Rotation IEC 1217 Convention describes Collimator rotation
Direction
increasing clockwise (CW) if facing the collimator
while lying on the table in standard HFS position.
90 degrees would then be facing your right hand
in the HFS position
Import Machine
Name
Must match exactly the name used in the imported
RTP or DICOM-RT convention
Abbreviated Name
Short name for printouts
Manufacturer
(optional)
Machine Model
(optional)
Serial Number
(optional)
Location
(optional)
Nominal SAD
Typically 100 cm
Nominal Gap
Typically 5 cm – describes the distance from
the bottom of the cone to patient surface at 100
SSD
Beam Energy
Nominal in MV (photon), MeV (electron)
Nominal dMAX
In cm
Calibration
Reference Depth
Depth at which the calibrated does rate is set,
in cm.
Calibration Field Size
(Photons Only)
In cm, typically 10 cm
Jaw Transmission (for future use)
Factors
Calibration Cone Size
(Electrons Only)
Choose from drop down list of available cones
Source to Jaw
Distances
Calibration Phantom
Distance
In cm, typically 100 cm
Allowed EDW wedge Any of 10, 15, 20, 25, 30, 45 and 60 degrees may
angles
be chosen
Base Table Rotation
IEC 1217 Convention describes 0 degrees as the
head of the table. If your system describes 0 degrees as the foot of the table you would insert 180
to let IMSure QA know that your coordinate system
is set 180 degrees from the IEC standard.
Table Rotation
Direction
IEC 1217 Convention describes Table Rotation
increasing clockwise (CW) as looking up at the
bottom of the table. 90 degrees would have the
head of the table to the left if facing the Gantry.
Jaw Naming
Conventions
May differ between manufacturers. Two alphanumeric characters allowed
Jaw limits
Machine dependent, may include over-travel.
Specified for both upper and lower jaws.
Allowed Field Size
Limits
May differ for Open and wedged data. May be
specified in rectangular form, as for most hard
wedges.
See table C
Diode Calibration Calibration factor for diodes used with this enFactor
ergy
Source to MLC
distances
See table C
MLC Type
Choose your MLC configuration from drop down
list
Allowed Wedge
Directions
Refers to the thin end (toe) of wedge
Wedge Name
(Photons Only)
Common Wedge name for hard wedges (e.g. 15
deg). A default wedge named ‘Open Field’ must
be present for all Photon energies
Measurements and parameters
Wedge Angle
(Photons Only)
The numerical value for the wedge angle. Must
match the value used in the imported RTP or
DICOM-RT convention.
Calibration
Dose Rate
In cGy/MU, at Calibration Depth and at Calibration
Phantom distance
Tray Factor
(Photons Only)
Tray Field/Open Field – less than 1.000
Cone Name
Common Cone name for electron cones (e.g.
A10).
IMSure QA Machine Data continued
Mean Dose Leaf
Leakage
(Photon Only)
Used in 3-source model. Typically between 1
and 3 %.
Mean Fluence Map
Leaf Leakage
(Photon Only)
Used in 3-source model. Typically between 1 and
3%. Used in map comparisons.
Dosimetric Leaf
The distance from the light field edge of an MLC
Offset (Photon Only) leaf to the radiation field edge.
EDW data
(Photon Only)
Derived from STT. User must choose STT energy.
Wedge Factor
(Photon Only)
At calibration field size (usually 10x10). Defined as the ratio of the measured values of the
wedged field at reference depth over the similar
open field.
Output Factor
(Electron Only)
The ratio of the dose at the reference depth for
the indicated cone versus the dose at reference
depth for the reference cone.
VSSD
(Electron Only)
Virtual Source to Surface Distance can be measured and used reliably over short ranges for
extended distance use.
Tabular Input Data
Tables below must be read in from CSV (comma
delimited) files set up in proprietary IMSure QA
format.
TMR (Photons)
See discussion below
PDD (Electrons)
“
OCR (Photons
and Electrons)
“
OF (Photons)
“
CF (Electrons)
“
Head Scatter,
Sc (Photons)
“
What data is needed?
The physics data required for setting up IMSure is similar to the data that
is acquired during commissioning a linear accelerator. Therefore most
people will already have the necessary information. All data needs to be
setup in a proprietary .csv (comma delimited) format that can easily be
created with Microsoft Excel. Examples of these files can be found in the
Sample Data folder that installs in the IMSure 3.1 directory (see pg. 9 of
user manual)
Photon Open field data
•
TMR – Tissue ­Maximum Ratios
○ From smallest to largest fields size with a 0 field size extrapolated from available data. See the IMSure technical note available from the Standard Imaging website titled, “Obtaining and
extrapolating data for IMSure calculations”.
○ TMR must be normalized to the dMAX value and should encompass all clinically relevant depths
•
OCR – Off-center Ratios (also known as Off-axis ratios)
○ Only the largest field size is needed, e.g. 40 cm
○ Ideally OCR is measured at 100 cm SSD and at multiple depths
including dMAX, e.g. dMAX, 5cm, 10cm, 15cm, 20cm, 30cm
•
○ OCR data must be normalized to the central axis
OF – Output Factors
○ The algorithms in IMSure require that output factors be measured or re-calculated to an SAD setup geometry and dMAX depth
▪
All tabular data can be read into IMSure QA from a comma delimited file (see
format below or the Sample Data CD-ROM for samples). The CSV file format
was chosen because it is easily manipulated in Excel spreadsheets.
For output factors measured at a different depth, IMSure will
automatically re-calculate the output factors to the required
setup geometry as long as the geometry is specified in the
setup and TMR tables have been previously imported (see
pg. 13 of user manual)
○ The output factors should be measured for the smallest to
largest possible square fields and normalized to the 10x10 field
size. A zero field size output factor needs to be extrapolated for
the model. See the IMSure technical note available from the
Standard Imaging website titled, “Obtaining and extrapolating
data for IMSure calculations”. A typical OF table will look like
this:
IMSure QA Machine Data continued
•
Sc – Head Scatter Factors
○ Sc is measured for each field size at isocenter (SAD) with an
appropriate buildup cap of at least dMAX effective radius over the
measurement chamber. Sc is normalized to the calibration field
size (10x10). Clean data at every cm below 10x10 will provide
the best results for the 3-source model although measurements
below 3 cm tend to be suspect due to the difficulty of accurately
measuring fields this small. A zero field size head scatter factor
needs to be extrapolated for the model. See the IMSure
technical note available from the Standard Imaging website
titled, “Obtaining and extrapolating data for IMSure calculations”.
A typical Sc table will look like this:
•
OCR – Off-center Ratios (also known as Off-axis ratios)
○ Only the largest field size is needed, e.g. 40 cm.
○ Ideally OCR is measured at 100 cm SSD and at multiple depths
including dMAX, e.g. dMAX, 5cm, 10cm, 15cm, 20cm, 30cm.
○ OCR data must be normalized to the central axis
○ OCR data for wedges should be set up with the thick edge of
the wedge oriented to the positive (right) axis of the off-axis
distance, i.e., OCR’s greater than one should be to the negative
(left) axis and OCR’s less than one should be to the positive
(right) axis.
•
OF – Output Factors
○ The algorithms in IMSure require that output factors be measured or re-calculated to a setup geometry of 100 cm SSD and
dMAX depth
 For output factors measured at a different setup, IMSure will
automatically re-calculate the output factors to the required setup
geometry as long as the geometry is specified in the setup and TMR
tables have been previously imported (see pg. 13 of user manual)
○ The output factors should be measured for the smallest to largest possible square fields and normalized to the 10x10 field size.
A zero field size output factor does not need to be extrapolated
for the wedge.
Photon Wedge Data
•
TMR – Tissue maximum Ratios
○ From smallest to largest fields size with a 0 field size extrapolated from available data. See the IMSure technical note available from the Standard Imaging website titled, “Obtaining and
extrapolating data for IMSure calculations”.
○ TMR must be normalized to the dMAX value and should encompass all clinically relevant depths
○ If the largest field size for the wedge is rectangular, e.g., 40 x 20
then the table should contain a field size of 26.67 (equivalent
square of 40 x 20). An additional field of 40 cm should be added
at the end of the table duplicating the 40 x 20 measurements as
this is required for the model. A typical table would look like this:
○ An additional wedge factor for the 10x10 field size (relative to
open field) is needed. Variation of the wedge factors with field
size are accounted for in the output factor and collimator scatter
tables of each wedge.
Enhanced Dynamic Wedge: The Enhanced Dynamic Wedge model is
algorithmically based, and no additional data is needed.
IMSure QA Machine Data continued
Electron Data
•
PDD – Percent Depth Dose tables
With these measurements, VSSD can be computed by following the algorithm below:
○ Should be measured down the central axis with the phantom
surface at calibration phantom distance. PDD should be normalized to reference depth. IMSure QA has no requirements for the
actual depths measured, but in typical use, measurements to the
practical range for each energy are preferred (rule of thumb: ½
cm depth for each MeV of energy). IMSure QA will not extrapolate PDD, and will not compute dose or MU for points that lie
outside of the PDD table.
•
1. Beginning with these measurements, for n points, first compute a
set of points,
x(i) = Distance(i) –SSDref
y(i) = sqrt[Dose(SSDref) / Dose (Distance(i))]
2. Compute the average of each set, x’ and y’
OCR – Off-center Ratios (also knows as Off-axis ratios)
○ In many clinical situations, electron dose will always be specified at the central axis. In this case, where the off axis distances
would not be used, the user may choose to use the default single
point OAR, which is specified as 1.000 at the reference depth and
central axis. IMSure QA will only allow the user to enter off-axis
distances that are contained in this table, and in this case, the
user will only be able to enter x and y calculation points as 0,0.
VSSD can be computed from measured dose at various distances using the
method of Khan, with a chamber at the reference depth (dref) in a water or
water equivalent phantom, beginning at SSDref (e.g. 100 cm) and taking
several measurements down to a clinically useful extended distance, 115
cm or 120 cm SSD.
xy’ = (x1*y1 + x2*y2 + … xn*yn)/n
*.3
xx’ = (x1*x1 + x2*x2 + … + xn*xn)/n
*.4
5. Compute the slope (m) of the best least squares fit for these points,
m = (xy’ – x’*y’] /(xx’ – x’*x’)
○ Should be measured for each cone and energy, with the surface
of the phantom at calibration phantom distance, and the chamber at calibration reference depth.
VSSD (Virtual Source to Surface Distance): Should be measured for
each electron energy and each cone. Electron output is affected by jaw
and collimator scattering, as well as in-air scattering, and does not follow
the inverse square law over large ranges as well as photons do. However,
an effective or virtual SSD can be measured and used reliably over short
ranges for extended distance use, as are often needed in clinical practice.
A typical range for clinical use would be from 100 SSD to 115 SSD.
*.2.a
*.2.b
4. Compute the average of the distance squared,
CF – Cutout Factor Table
○ A series of cutout apertures should be made for each cone, in
10-20% increments, down to 40-60% for the smallest aperture.
For example, a 6x6 cone might have 3x3, 4x4, and 5x5 cutouts
(and 6x6, by default). A 20x20 cone might range have 10, 12.5
15, 17.5 and 20 cm cutouts. By definition; CF (unblocked field) =
1.000. Typical ranges of CF will be from 0.900 to 1.100, but can
go as low as 0.700 for very small cutouts.
x’ = (x1+x2+…xn)/n , y’ = (y1+y2+…yn)/n
3. Compute the average area,
○ Should be measured with the phantom surface at calibration
phantom distance, and at several depths. OCR must be normalized to the central axis value for each depth.
•
*.1.a
*.1.b
*.5
6. Finally,
VSSD = 1/m – dref
*.6
VSSD will vary for each energy and each cone, and must be measured
separately. VSSD also vary depending on accelerator and cone construction, but will typically range between 75 and 98 cm.
Cyberknife Data
•
TMR – Tissue Maximum Ratio
○ From smallest to largest collimator size with values from 0 to
clinically relevant depths
•
○ TMR must be normalized to the dMAX value
OCR – Off center Ratios (also known as Off-axis ratios)
○ Separate tables need to be created for each collimator size with
measured data at multiple depths including dMAX, e.g., 15 mm, 50
mm, 100 mm, 150 mm, 200 mm, and 250 mm, normalized to the
central axis
•
OF – Output factors
○ Output factors at different collimator sizes for differing SADs
typically from 500mm to 1100mm.
IMSure QA Machine Data continued
Setting up your data for IMSure
There are two choices for getting your data into IMSure. 1. Send your
data to Standard Imaging for conversion and setup. 2. Convert your
data yourself. There are advantages to each. Having Standard Imaging
convert your data of course means less work up front and we include the
conversion of up to 3 different machine’s data with your purchase. On the
other hand, doing the conversion yourself gives you the peace-of-mind
that the data was converted correctly and might mean less commissioning of the data before use.
See the .csv files in the Machine Data folder in the Sample Data
directory for an example on how to set up the file correctly. .
.csv file formatted files can be created in various programs but
Standard Imaging suggests utilizing Microsoft Excel for this task.
NOTE: Data must be set up exactly as shown or it will not
import into the IMSure physics module. (See pg. 15 of user
manual)
Sending your data to Standard Imaging for conversion
Make sure you have all of the required data. In most cases this data
is available from the scanning system that you use. Most scanning
system’s software offers multiple export functions. The data needs to
be output in ASCII format and ideally output as Excel spreadsheets.
IMPORTANT - For Eclipse users only – The Eclipse system
saves all of the raw beam data that is imported for beam modeling. If you use the Eclipse system contact Standard Imaging
and ask for the IMSure – Eclipse export instructions. This document includes step-by-step instructions for exporting this data
from Eclipse. This data then is zipped and sent to Standard
Imaging via e-mail. It is easily converted to IMSure format and
setup into an IMSure physics file which is then sent to you for
commissioning.
Your data will be returned to you formatted into a physics.imsure
file (see pg.12 of user manual) This file contains all of your data
pre-formatted for use with IMSure. Place the physics.imsure file into
the directory of your choice and then in IMSure preferences/Folder
preferences (see pg. 6 of user manual) set the Machine folder to the
same directory. Clicking on the Physics tab after setting this parameter will display the physics data.
NOTE: You will need to change the Machine Name(s) in the physics file to match the name your TPS uses for your machine.
Setting up your data yourself –
Use the sample .csv files that can be found in the Machine Data directory
in the Sample Data folder (see pg. 9 of user manual) as a guide in setting
up your data. The structure of these .csv files is very specific and will not
import into IMSure if they are not correct. The structure for each is as
follows:
1. Photons
a. From smallest to largest field size. A zero-field TMR must be
added to the open field table by the user in order to use the
3-source model. See the IMSure QA Physics Technical Note
regarding extrapolation of 0 field size data. However, the model
is relatively insensitive to that extrapolated data. Wedged fields
only need the smallest to largest field size.
TMR should be normalized to the dMAX of the energy. TMR data
must include reference depth. IMSure QA does not extrapolate
TMR depth, so values to clinically reasonable depths must be
taken or extrapolated by the user.
For non-square wedged fields there should be two entries for the
largest field size, one at the equivalent square of the non-square
field and one at the largest opening size for the individual jaws.
For example in the case of a 40 x 20 field, there would be an
entry for a field size of 26.7 (equivalent square) and one for 40
cm, both containing the same data.
b. OCR table – Only the largest field size for open and wedged.
Ideally the OCR data is measured at 100 SSD, at multiple
depths. Correction for depth dependent divergence is made by
IMSure QA. No correction is made for the minor variances due
to the true divergent depth at off-axis positions, but as the depth
to the specification calculation point is defined as the depth
down the central axis, no correction is required.
For open fields, a diagonal scan, if available, may provide more
reliable results. Half beam scans may be used, but must be
mirror imaged before im­port. IMSure QA does not distinguish
between radial and transverse scans, but averaged scans of
transverse and radial setup are also acceptable
For wedged data, only scans in wedged direction are needed,
and only for the largest field size. OCR data should include reference depth and must be normalized to the central axis value
at each depth, and independent of PDD. Wedge OCRs should
be measured with the ‘thick end’ of the wedge oriented to the
positive (right) axis of the off-axis distance, i.e., OCRs greater
than one should be to the negative (left) axis and OCRs less
than one should be to the positive (right) axis.
See the .csv files in the Machine Data folder in the Sample Data
directory for an example on how to set up the file correctly. .
.csv file formatted files can be created in various programs but
Standard Imaging suggests utilizing Microsoft Excel for this task.
NOTE: Data must be set up exactly as shown or it will not
import into the IMSure physics module. (See pg. 15 of user
manual)
IMSure QA Machine Data continued
c. OF Table (Output Factors) – From smallest to largest possible
square fields only, normal­ized to 10x10 FS. The models in
IMSure require output factors measured at dMAX. It is common
practice to measure output factors at deeper depths, e.g. 5 cm
to remove the electron contamination from the measurements.
IMSure can automatically back adjust these measurements to
dMAX as long as there is TMR data already input into the physics
module (see pg. 13 of user manual)
For Open-field data a zero FS extrapolation is needed. See the
IMSure QA Physics Technical Note regarding extrapolation of 0
field size data. For wedged data, Sc,p should be normalized to
10x10 and should range from smallest to largest field sizes. An
additional wedge factor for the 10x10 field size (relative to open
field) is needed. Variation of the wedge factors with field size are
accounted for in the output factor and collimator scatter tables of
each wedge.
The output factors, in combination with the Collimator Scatter Factors, are used to compute the phantom scatter, as Sp =
OF/Sc. OF is specified independently for wedged fields, so that
FS dependent wedge factors may be accommodated.
See the .csv files in the Machine Data folder in the Sample Data
directory for an example on how to set up the file correctly. .
.csv file formatted files can be created in various programs but
Standard Imaging suggests utilizing Microsoft Excel for this task.
NOTE: Data must be set up exactly as shown or it will not
import into the IMSure physics module. (See pg. 15 of user
manual)
d. Sc Table (Head Scatter) - Collimator Scatter, Sc, is very
important to the 3-source model. Sc for the square field sizes
is required to 1) compute the phantom scatter from the output
factor and 2) verify that the three source model head scatter
coefficients are modeled correctly.
Sc is not necessary for wedged fields as this is automatically
calculated from the formula Sc(wedged) = Sc,p (wedged)/
Sp(open).
Sc is measured for each field size at isocenter (SAD) with an
appropriate buildup cap of at least dMAX effective radius over the
measurement chamber. Sc is normalized to the calibration field
size (10x10).
A zero field size Sc is needed for the open-field (non-wedged)
data to use the 3-source model, and may be extrapolated from
the small field size data. See the IMSure QA Physics Technical
Note regarding extrapolation of 0 field size data. Because of
the nature of the model, clean Sc data ranging down to at least
3x3, measured for every FS between 3 and 12, will give the best
results.
See the .csv files in the Machine Data folder in the Sample Data
directory for an example on how to set up the file correctly.
.csv file formatted files can be created in various programs but
Standard Imaging suggests utilizing Microsoft Excel for this task.
IMPORTANT: Data must be set up exactly as shown or it will
not import into the IMSure physics module. (See pg. 15 of
user manual)
2. Electrons
a. PDD - Should be measured down the central axis with the
phantom surface at calibration phantom distance. PDD should
be normalized to reference depth.
IMSure QA has no requirements for the actual depths measured,
but in typical use, measurements to the practical range for each
energy are preferred (rule of thumb: ½ cm depth for each MeV
of energy). IMSure QA will not extrapolate PDD, and will not
compute dose or MU for points that lie outside of the PDD table.
See the .csv files in the Machine Data folder in the Sample Data
directory for an example on how to set up the file correctly. .
.csv file formatted files can be created in various programs but
Standard Imaging suggests utilizing Microsoft Excel for this task.
IMPORTANT: Data must be set up exactly as shown or it will
not import into the IMSure physics module. (See pg. 15 of
user manual)
b. OCR - Should be measured with the phantom surface at calibration phantom distance, and at several depths. OCR must be
normalized to the central axis value for each depth.
In many clinical situations, electron dose will always be specified
at the central axis. In this case, where the off axis distances
would not be used, the user may choose to use the default
single point OAR, which is specified as 1.000 at the reference
depth and central axis. IMSure QA will only allow the user to
enter off-axis distances that are contained in this table, and in
this case, the user will only be able to enter x and y calculation
points as 0,0.
The file format for electron OCR is identical to photon (see pg.6
of this manual).
c. CF Table (cone factor) - Cone Factor tables for electrons should
be measured for each cone and energy, with the surface of the
phantom at calibration phantom distance, and the chamber at
calibration reference depth. A series of cutout apertures should
be made for each cone, in 10-20% increments, down to 40-60%
for the smallest aperture. For example, a 6x6 cone might have
IMSure QA Machine Data continued
3x3, 4x4, and 5x5 cutouts (and 6x6, by default). A 20x20 cone
might range have 10, 12.5 15, 17.5 and 20 cm cutouts. By definition; CF (unblocked field) = 1.000. Typical ranges of CF will be
from 0.900 to 1.100, but can go as low as 0.700 for very small
cutouts.
An OCR table should be created for each collimator size and
should contain data out to the maximum radius used clinically at
several clinically used depths normalized to the central axis.
See the .csv files in the Machine Data folder in the Sample Data
directory for an example on how to set up the file correctly. .
.csv file formatted files can be created in various programs but
Standard Imaging suggests utilizing Microsoft Excel for this task.
IMPORTANT: Data must be set up exactly as shown or it will
not import into the IMSure physics module. (See pg. 15 of
user manual)
.csv file formatted files can be created in various programs but
Standard Imaging suggests utilizing Microsoft Excel for this task.
IMPORTANT: Data must be set up exactly as shown or it will
not import into the IMSure physics module. (See pg. 15 of
user manual)
See the .csv files in the Machine Data folder in the Sample Data
directory for an example on how to set up the file correctly. .
3. Cyberknife
a. TMR for Cyberknife – The Cyberknife planning system can
export as text files the TMR tables that were originally input from
machine data. The format for the IMSure .csv files for Cyberknife
TMR was designed to be very similar to those in order to make it
easy to create the correct file structure.
The TMR table should contain data for each collimator size and
all clinical depths and must be normalized to the dMAX value.
See the .csv files in the Machine Data folder in the Sample Data
directory for an example on how to set up the file correctly. .
.csv file formatted files can be created in various programs but
Standard Imaging suggests utilizing Microsoft Excel for this task.
IMPORTANT: Data must be set up exactly as shown or it will
not import into the IMSure physics module. (See pg. 15 of
user manual)
c. OF for Cyberknife - The Cyberknife planning system can export
as text files the OF tables that were originally input from machine data. The format for the IMSure .csv files for Cyberknife
OF was designed to be very similar to those in order to make it
easy to create the correct file structure.
An OF table should contain the measured output factors for
each collimator size and a variety of SAD distances. All output
factors are relative to the 60 mm collimator and are normalized
to that value. The value of the 60 mm collimator OF is 1.00 by
definition.
See the .csv files in the Machine Data folder in the Sample Data
directory for an example on how to set up the file correctly. .
.csv file formatted files can be created in various programs but
Standard Imaging suggests utilizing Microsoft Excel for this task.
IMPORTANT: Data must be set up exactly as shown or it will
not import into the IMSure physics module. (See pg. 15 of
user manual)
b. OCR for Cyberknife - The Cyberknife planning system can
export as text files the OCR tables that were originally input from
machine data. The format for the IMSure .csv files for Cyberknife
OCR was designed to be very similar to those in order to make it
easy to create the correct file structure.
IMSure QA Machine Data continued
Table B: Rules for Machine Data Consistency
1.
The Maximum Field size for the TMR data must be greater than or
equal to the Maximum Field size for that Wedge.
2.
For open fields, the Minimum Field size for the TMR data must be
equal to 0.0 cm.
3.
For non-open fields, the Minimum Field size for the TMR data must
be less than or equal to the Minimum Field size for that Wedge.
4.
A Field size must exist in the TMR data that matches the Minimum
Field size for that Wedge.
5.
6.
The values for the TMR depths must increase monotonically.
The values for the TMR Field Sizes must increase monotonically.
7.
The values for the Output Factor Field Sizes must increase monotonically.
8.
The values for the Collimator Scatter Factor Field Sizes must increase monotonically.
9.
The values for the Off-axis Ratio Depths must increase monotonically.
10. The values for the Off-axis Ratio Distances must increase monotonically.
11. The minimum value for the Off-axis Ratio Distances must be equal
to or less than (-Maximum Field Size/2).
12. The maximum value for the Off-axis Ratio Distances must be equal
to or greater than (+Maximum Field Size/2).
13. The TMR depths must include the Reference Depth.
14. The TMR Field Size set must include the Calibration Field Size.
15. The Output Factor Field Sizes must include the Calibration Field
Size.
16. The Collimator Scatter Factor Field Sizes must include the Calibration Field Size.
17. The output factors for all fields must be normalized to the value
at the Calibration Field Size (i.e., the output factor at FS=CFS will
equal 1.000).
18. The Collimator Scatter factors must be normalized to the value at
the Calibration Field Size (i.e., the output factor at FS=CFS will
equal 1.000).
19. The TMR value for the Calibration Field Size and at the Reference
depth must equal 1.
20. For open fields, the Min Jaw position for either upper or lower jaws
may not be less than (-Maximum Field Size/2).
21. For open fields, the Max Jaw position for either upper or lower jaws
may not be greater than (+Maximum Field Size/2).
22. PDD must contain the reference depth and the value at that point
must equal 1.000
23. PDD depths must increase monotonically
24. OCR must have at least one point = 1.000 at dMAX on CAX
25. Cone Factor must contain at least one point = 1.000 for FS = sqrt
(ConeX * ConeY)
Table C: Known Geometry Values for Various Linear Accelerator Heads
Distances for Primary collimator and Flattening Filter Geometry
used in 3-source model (Fixed, non-editable)
Jaw Distances (in cm)
Linac MLC Type
Elekta 80 *
Siemens
Varian 52
Varian 80
Varian 120
Zx
40.1
28.3
36.7
36.7
36.7
Zy
43.4
19.7
27.9
27.9
27.9
Zmlc
29.8
28.3
48.3
48.3
48.3
Zsp
4.0
4.0
4.0
4.0
4.0
Zsf
12.5
10.5
12.5
12.5
12.5
R01
0.2
0.2
0.2
0.2
0.2
R02
1.4
1.1
1.4
1.4
1.4
* The IMSure QA model assumes that MLC leaves are in the “X-direction”. The Elekta system can be accommodated by specifying the jaw distances as
above with the “Lower Jaw” specified as closer to the source than the “Upper Jaw”. An additional offsetting correction must be made in the Jaw Naming
convention, where the expected X jaw and Y jaw names are exchanged.