Hologic QDR 4500 - Radiation Measurement and Calibration Procedures

QDR
®
4500 Technical Manual
3-24
2. Run SQDRIVER.
3. At the CARM$$$$> prompt type CALIBRATE (be patient, this procedure takes several
minutes).
CHECK LASER POSITIONING OFFSET
Center the table and arm using Center Table, or utility A/P position feature. Turn on the laser and
set it on the point of a sharp object. At the DOS prompt type SCANSQ -PNOFLAT and begin a
scan. Using the F3 function, realign the arm to the proper position and exit before the scan
begins. Turn on the laser and physically adjust back to the point of the object as follows:
1. Locate the 3 laser adjustment screws (small Phillips) under the C-arm. Adjust these
screws until the laser cross-hair is on the pointed object.
2. Run another scan to check your adjustments.
ADJUST A/D GAIN CONTROL
In order that all QDR 4500 machines have the same input to the A/D converter, regardless of
slight variation in X-ray flux detected, a potentiometer has been installed on the unit’s A/D
converter board. Perform the
A/D Gain Control Adjustment
procedure in the
ALIGNMENT AND
CALIBRATION
section of this manual.
PERFORM BEAM FLATTENING
This procedure flattens the X-ray beam for each scan mode. Perform the
Beam Flattening
procedure in the
ALIGNMENT AND CALIBRATION
section of this manual.
Note:
All covers, table mat, etc., in the X-ray path, must be on the Scanner before running beam
flattening.
PERFORM LATERAL ALIGNMENT TEST
This procedure verifies lateral alignment. Perform the
Lateral Alignment Test
procedure in the
ALIGNMENT AND CALIBRATION
section of this manual.
MEASURE X-RAY DOSE TO PATIENT
A radiation dose measurement must be performed at installation time, and should be done
routinely whenever the machine is worked on. This test requires the use of a Victoreen Model
450P or equivalent.
Note:
The dose measurements must be done with the machine fully assembled
and the table mat
in place
. The typical dose measurements are as follows for listed scan modes:
1. Place the meter in the center of the table and position the laser about 1/4 inch to the left
of the meter.