Stereotactic_Radiosurgery- ACCURAY REQUIREMENTS

1. Positional accuracy of the measurement point shall be no greater than 0.1mm along each axis, for a full tank of water.

2. Positional repeatability of the measurement point shall be no greater than 0.1 mm along each axis, for a full tank of water.

3. Minimum scan region shall be (W)200 x (L)160 x (D)300 mm.

4. Measurement time at each point: minimum shall be 0.1 s or less.

5. Step size: minimum shall be 0.2 mm or less.

6. The following parameters shall be user selectable:

Scan speed.

Scan range.

7. System shall be able to scan at radial directions along arbitrary angles about the vertical axis (e.g. 15 o angles are required for Iris beam commissioning, 45 o for conventional Linacs).

8. System shall have the ability to adjust for phantom tilt of at least 1 o in roll and pitch.

9. Electrometer shall meet the following specifications:

Non-linearity < ± 0.5% (as per IEC) 60731.

Stability after 8hrs < ± 0.5% p.a.

Leakage current < ± 1 fA

10. System shall have sufficient dynamic range to measure OCR tails at depth of 300mm to within 0.5% of point measurements for 1000 MU LInac.

11. System shall accommodate standard diode detectors and chambers (e.g PTW 60008 and 60012, Sun Nuclear Edge or other equivalent Accuray approved detectors) as well as options for different connectors (e.g. BNC coax./triax, TNC).

12. System shall have automatic gain adjustment to balance the signal between the field and the reference channels (especially when one is diode and other is an ion chamber).

Software

13.-System shall be able to add OCR profiles, average them and fold in half.

System shall have the ability to calculate flatness and symmetry preferably with choice of different protocols e.g. Accuray or Varian etc.

16. System shall be capable of smoothing acquired raw scan data.

17. System shall allow for ability to read point dose values from the displayed plots or present tabulated form.

18. System shall be able to export raw scan data in ASCII format.

19. System shall have the ability to acquire at least four profiles at five different depths without operator intervention. e.g. typical OCR scan for fixed collimators require two profiles (0 o and 90 o) at five depths (15 mm, 50 mm, 100 mm, 200 mm & 300 mm), and a typical Iris OCR scans require four profiles(0 o, 15 o, 90 o,105 o) at the same depths.

18. System shall have an automated routine that provides the offset between the null point and the profile mid-point at two different depths and displays the angle between them.

19. System shall be able to reset its null position based on the calculated offset.

20. System can operate as a software based electrometer in both charge integrated and dose rate mode.

COMPLIANCE

1.- Positioning accuracy: AXES X:0.1-0.2, Z:0.1-0.2 Y:0.2-0.25

2.- It complies

3.- It complies

4.- It seems that this spec applies to integrating electrometer. Our electrometer does only relative measurements. If this is test of the speed, we measure an average of 45 sec for a TPR depth of 30cm. The time is a function of the ARM selectable speed.

5.- It complies

6.- It complies

7.- It complies

8.- It complies

9.- It complies for non-integrating electrometer

10.- It complies

11.- the system does good measurements with the 60012 and 60017 PTW diodes, a little noisier with the edge.

12.- It complies

Software

13.- It complies

16.- It complies

17.- It complies

19.- It complies

20.- The ARM electrometer is not an integrating electrometer; scans in dose rate mode only.

An integrated electrometer can be connected to the ARM system and take point measurements at required depths

* The robust stand was designed to move the small tank to within the Accuray positioning specifications.

** Of particular relevance is the way that the scanner does the autocenter Using a 0.1 resolution; it determines the center of the radiation field in 1/10 of millimeter or better. It finds the deviation from the center and automatically corrects it. It also determines the angle of deviation; an exceeding spec of the angle could be due to non correct angle position or an erroneous measurement of the scanning system.