OBI MONTHLY QA
Machine:
S/No
Initial
Date
1. Collision interlock-- Alarm sound & All motions disabled
Location
Arms
Detector
Pass
Fail
Comments
Rotate gadry to 90 degree so kv is at floor
Measure distance to grid&shift at two different detector distance
2. KVDetector Position and Reproduciblity
Measure SSD to detector shift at two different detector distance
Detector Position
SSD (cm)
Diff or Shift (<0.2cm)
Vertica Long
Lat
Expected measured Diff
(<0.2cm) Sup/inf
l
60
0
0
55.2
20
0
0
15.2
3. KV Source Position and Reproduciblity
Place KVS at 100,0,0
Rotate gandry to 270 so KVS is at floor
Measure from source face plate to isocentre
Detector Position
Vertica Long
Lat
l
100
0
0
Distance (cm)
Expected measured
85.5
Diff or Shift (<0.2cm)
Diff
(<0.2cm)
Rt/Lt
4. Imager Alignment & Scaling
Scaling
Setup blade calibration plate on couch top @ 100cm SSD
Level gantry to 90degree so KV detector is at floor
Place KV source at 100,0,0 & detector at 50,0,0
In OBI maintenance take an image using single pulse full resolution
Measure distance between 10X10 pair of lines in X & Y direction
Technique
KVP
60
MA
16.0
Ms
Direction
X
Y
Expected(cm)
10
10
Measured(cm)
Diff (cm)
8.0
Pass/fail
Imager Alignment
Using image from above zoom out until the centre circle on the plate is visible
Select area histogram icon and select show details
Change Hor Pos to 1024 & Vert Pos to 768
Drag upper left hand corner of the ROI box until it intersects the centre of the circle
Record the Hor Pos & Vert Pos of the centre pixel position
Center pixel position
Pass/fail
(<10pixels)
Expected
Measured
Diff.
Horizontal post 1024
Vertical post
768
5. OBI Imaging & Treatment Isocenter Coincidence
Place isocenter cube tool on couch top at isocenter using laser and crosshairs
Place KV source at 100,0,0 & detector at 50,0,0
In OBI maintanance take an images at four cardinal angles
At each angle measure difference between center of steel ball & digital graticule
technique
KVP
Gantry angle
270
0
90
180
FF Last Image Hold
50
mA
16
KV source angle
180
270
0
90
ms
Difference (cm)
8
Pass/fail(<0.15cm)
2D/2D match and couch shift accuracy
Expected Shift(B)
shift(A)
(A-B)
New
couch
position
(C)
Final
(C-D)
couch
position
(D)
Vertical
Long
Lat
6. Image Quality (LEEDS Test Tool)
High Contrast Resolution
Place gandry to 90 degree so KV detector is at floor
Remove couch from beam path & remove any OBI filter
Place KV source at 100,0,0 & detector at 50,0,0
Place leeds test tool onn diagonal on detector cover
Image and window & level to resolve greatest lp/mm
technique SinglePulseFull Resolution
KVP
50
mA
50
ms
6.0
Low Contrast Resolution
Use setup from above
Attach 1mm cu filter to kv source faceplate
Image and window & level to resolve lowest contrast disc
Turn off lights & view from a distance
technique SinglePulseFull Resolution
KVP
85
mA
50.0
ms
Disc # resolved
Disc # resolved
4.0
Total
≤2mm