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 The MapCHECK is a 2-dimensional detector array designed for efficient and stringent IMRT plan QA. The MapCHECK measures the integrated absolute dose with 445 detector locations, of which 221 are located in the 10 cm x 10 cm center. Analysis of the measured and planned dose is performed within the MapCHECK software by importing a dose map file from the treatment planning system.
Measuring a dose file and importing from the planning system is fast and efficient. Comparison criteria are easy to adjust, and concise results are immediately displayed. Reports are generated for easy filing.
East Setup
The MapCHECK is quickly setup using the lasers and crosshairs. The MapCHECK software communicates with the hardware via a single power/data cable. The CAX of each dose map is known or calculated by the MapCHECK software, meaning there is no manual registration of planned and calculated files.
Comparison and Analysis
The MapCHECK compares measured dose points to planned dose points with a single mouse click immediately following measurement. The user may compare normalized data or absolute dose data using distance to agreement or gamma. Three adjustable criteria guarantee maximum user control:
1. Threshold: Isodose percentage line that defines the dose area to evaluate. This is a more stringent method compared to defining arbitrary boxes around regions of interest.
2. Distance to Agreement: If Dose Difference is not satisfied, then planned points are searched within a user-defined radius for a value that corresponds to the measured point at the center of the radius.
3. Dose Difference: Planned dose is subtracted from measured dose and the difference is evaluated. Supports normalized or absolute dose comparisons.
Measured points that do not fit within the acceptance criteria are highlighted. A summary of total measured points, number passed, number failed, and percent passed is presented.
Accuracy
The MapCHECK delivers accurate results when compared to other methods such as film and ionization chambers. MapCHECK dose response is less noisy than film, and because the dose values are absolute, the need for a chamber point measurement is eliminated.
MapCheck detectors measure only 0.8 mm x 0.8 mm and can more precisely measure penumbras. Due to the fact that IMRT beams are collections of small fields with steep penumbras, this is a critical MapCHECK advantage.
MLC QA
The MapCHECK has been shown to differentiate systematic MLC misalignments of only 1 mm. Only the MapCHECK enables instant absolute dose readings of patient plans with the necessary spatial resolution to also detect machine misalignments.
MapCHECK data acquisition is fast. Beams can be measured individually or as a composite (orthogonal to the the MapCHECK). STEP 1 - Measured data displayed as dose contours
STEP 2 - Import planned data - displayed as dose contours
STEP 3 - Compare measured dose to planned dose for each detector
STEP 4 - Profiles show measured and planned dose for any detector row or column
Advanced Film Analysis (AFA™)
MapCHECK Advanced film Analysis (AFA) is for customers who wish to use film for periodic QA, either IMRT or other, and for those customers new to IMRT who want multiple methods to commission their system. Every MapCHECK system includes AFA.
What sets MapCHECK AFA apart from other film analysis systems is easier setup and better dose response. Films are calibrated using dose data from the MapCHECK detector array - an H & D curve and ion chamber measurement is not necessary. Pin Prick location is completely automated. Simply scan a film and apply your MapCHECK dose calibration and background subtraction files.
Three easy steps for film analysis:
1. Scan film with MapCHECK software
2. Calibrate film with MapCHECK detector array
3. Save your film file
Isocentric Mounting Fixture (IMF™)
The IMF holds the MapCHECK array at up to 10 cm of water equivalent depth securely in the accessory tray and at precisely 100 cm SDD. IMF exhibits little to no flex at any gantry angle, ensuring exceptional accuracy in determining gravity induced off-axis MLC shifts.
Specifications
Detector Array
Quantity: 445 solid state radiation hardened n-type detectors
Array Geometry
Center Array: 10 cm x 10 cm array: Detector Spacing 7.07 mm
Outer Ring Surrounding Center Array (6 cm wide)
Detector Spacing: 14.14 mm
Axial and Transverse (X,Y) Linear Array Length: 22 cm x 22 cm,
Detector Spacing: 10 mm
Diagonals Linear Array Length: 25.4 cm x 25.4 cm , 7.07 mm spacing
Active Detector Area: 0.8 mm x 0.8 mm
Total Inherent Buildup to Detector Junction: 2.0 ± 0.1 g/cm2
Physical Distance to Detector Junction from Overlay: 1.35 ± 0.1 cm
Total Inherent Backscatter to Detector Junction: 2.7 ± 0.1 g/cm2
Physical Distance to Detector Junction from Bottom Of Instrument Plate: 1.94 ± 0.1 cm
Radiation Measured: Photons, Co-60 to 25 MV: Electrons, 6 MeV to 25 MeV
Dosage Limit: 330 cGy
Detector Location: Actual detector position on pc board aligned within 0.25 mm of identified location
Dimensions: 31.2 cm W x 43.3 cm L x 5.2 cm T (with leveling feet)
Weight: 4.8 kg
Power
Type: “Desktop”, switching
Input: 100 or 240 VAC, 47/63 Hz; General Purpose IEC 320 socket, Class I Power Inlet for straight cable entry.
Output: +18 VDC, 1 AMP, 2.5 mm center positive plug
Dimensions: 4.7 cm W x 8.65 cm L x 3.2 cm T
Cables
Power/Data: 25-meter, connects MapCHECK to power supply
Serial Data: 2-meter, 9 pin connects power supply to PC
IEC straight plug, line cord
Calibration
• Wide field array calibration using patented method, U.S. Patent no. 6125335
• Relative correction factors for each array detector stored in PC calibration files.
• Absolute dose calibration converts relative values to absolute values
Computer System Requirements
Computer: Minimum Pentium 700 mHz, 128 MB RAM, 1 MB VGA video card capable of at least 800 x 600 pixels and open GL capable, USB or Serial port, 5 MB HDD
Operating System: Windows 98 or higher, MapCHECK Windows code requires 3 MB installed
Firmware: Factory installed in flash memory (PC updateable)
MapCHECK IMRT QA System Includes:
MapCHECK Detector Array with PC Software Interface, 25 m power data cable, MapCHECK off-axis positiong template, USB Cable, Power Supply (110/220 V) and Calibration Fixture.
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