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