CRS Proton Scanner capabilities
The CRS proton software is designed to move a chamber to specified depths points, set up in a table, dwell on each point for a determined amount of time and record each point, then export them to file for analysis. Analyzing the scans is limited to displaying and printing the depth dose curves, screen cursor measurements and PDD printouts.
Supported IMPORT formats to convert to CRS:
W2cad (Eclipse, Varian Golden Files)
CRS supported EXPORT treatment plan formats:
CMS (old binary format)
The electrometer’s primary and reference analog amplifiers have a fixed gain to ensure that no changes to frequency response will occur, which can affect accuracy. The amplifiers do not have any integration which makes the response time as fast as possible. This allows the electrometer to act as an oscilloscope to read and store the signal as it is outputted from the LINAC in raw form. The electrometer’s analog inputs are digitized using 16 bit digital to analog converters within the electrometer before being transmitted to the PC. These analog inputs include primary channel, reference channel and bias voltage measured at all times at the chambers.
Scanning is done by a scan that first moves away from the origin, followed by a second one returning back to the origin. During the measurements, the PC software receives the primary and reference raw data, reference corrections are done by the PC software after the scans are completed and averaged together. The data is displayed and stored automatically with a unique identifier.
Before scanning, the chamber origin is manually set by hand, the software moves all motors with 1/4mm increments as instructed by the PC site energy record. The software calculates the motor step movements, including returning the scanner to origin. Again, this ELIMINATES position feedback from the water tank. There is no speeding up or slowing down of the scanning due to rapid change of input, like depth build-up region or penumbras. The scanner runs as fast as possible based on a user setting of scanning speed. It can be set to less than one mm/second to about a hundred mm/second, thirty to fifty mm/second is a good average scanning speed.
CRS scanning options and capabilities:
Open field Depth dose
Open field Profile
Wedge Depth dose
Wedge longitudinal Depth
Wedge longitudinal Profile
Depth dose under a block
Profile under a block
Dynamic Profile wedge
Dynamic Depth wedge
Open field TMR Depth
Open field SAD profile
CRS Scanning system concept
All of our scanning hardware is designed with simplicity in mind, a building-block concept, many of the components are interchangeable with each other, costs can be reduced by purchasing our 2D scanner as the main component and adding other equipment as accessories to the scanner by sharing some of the common parts. The software is common to all of our scanners using standard LAN 10/100 communication and compatible with Windows XP-10 operating systems, no drivers or separate licenses are needed and there are no restrictions on how many computers are used.
CRS absolute TG-51 calibration, semiautomatic or automatic
All calculations required by the TG-51 published worksheets are supported with the exception of Worksheet C.
The software accepts depth dose data either manually entered or from scanned CRS data files. Using the CRS electrometer one can measure depth dose files used with the calibration and ultimately measure the Dose automatically.
There are two alternatives to obtain the necessary depth dose data. One is using clinical spreadsheet depth dose data and the other is creating a CRS formatted depth dose file from a CRS supported Treatment Plan. The CRS SCAN software has provision to do that.
Dose readings are entered manually into the computer using a calibrated electrometer or automatically using the CRS electrometer. Averaging of more than one Dose reading is provided for. The CRS electrometer can be calibrated by an ACL or cross calibrated against a calibrated electrometer.
All calibration information collected, measured and calculated are stored in a TG-11 formatted file by date. Calibration reports are either hardcopy printed or transferred into a spreadsheet file from the TG-11 file.
Absolute Dose TG-51 calibration in water is supported in TomoTherapy units with the incorporation of the TG-148 protocol.
The software collects, calculates and stores the following:
Determination of kq
Corrected ion.chamber reading
Dose to water at 10cm depth
Dose to water/MU at dmax
Determination of Kecal and K’R50
Corrected ion.chamber reading
Dose to water at reference depth, dref
Dose to water/MU at dmax
CRS Analyze Data options and capabilities:
Transfer to Treatment plans
Make dosimetry tables, up to 40cm
TG21/25 Ionization screen display
TG21/25/51 PDD screen display
Make stereotactic dosimetry tables, up to 10cm
How the CRS scanning system works
The basic component that makes this system different to other systems is the electrometer. It is completely software driven from a remote PC. Every 1/4mm step of any axis movement is originated by the PC software. This ELIMINATES position feedback from the water tank. The PC acts as the system clock for all the electrometer functions, which includes motor stepping, data transfers of current measurements for primary and reference inputs and bias control.