YY 0832.1-2011Stereotactic and planning system for radiotherapy with X-Radiation - Part 1: Stereotactic and planning system for radiotherapy with X-Radiation for head lesion (English PDF)

4.1 Coordinates

The system shall adopt the requirements for coordinates, movements and scales in GB/T 18987. If other coordinates are adopted, they shall be indicated in the random file as required in 4.2a).

4.2 Random file

The random file shall include at least the following contents.

a) The coordinates adopted by the system; as well as the relationship between such coordinates and the coordinates defined in GB/T 18987;

b) The medical electron accelerator (hereinafter referred to as the accelerator) used in conjunction with shall meet the requirements of GB 15213 and GB 9706.5;

c) The energy range of the accelerator used in conjunction with;

d) The parameters of collimator, including the quantity, No., height, nominal dimensions of the two end faces;

e) The size of the radiation filed for the accelerator used in conjunction with, after assembly of the collimator;

f) The size of radiation field of each collimator along the direction of the two main axes of the isocenter of accelerator used in conjunction with;

g) The value of penumbra of each collimator along the direction of the two main axes of the isocenter of accelerator used in conjunction with;

h) The parameters, dimensions, and relevant information of the stereotactic device used in conjunction with;

i) In order to meet the isocenter accuracy and other requirements of the accelerator used in conjunction with as required in 4.6;

j) In order to meet the imaging parameters required in 4.8, as well as the test methods whether the image satisfies the therapy plan.

The target reconstruction position error calculated by the therapy planning software shall be no greater than 1.5mm.

4.8.3 Area coincidence rate

The coincidence rate BETWEEN the area enclosed by 80% isodose line calculated by the therapy planning software AND the area enclosed by the film calculated under the same conditions shall be greater than 90%.

4.9 Security requirements of the therapy planning software

The therapy planning software in the system shall meet the requirements of YY 0637.

5.1 Coordinates

The inspection of the random file shall meet the requirements of 4.1.

5.2 Requirements for the random file

The inspection of random file shall meet the requirements of 4.2.

5.3 Size deviation of radiation field

It shall be performed by the following methods.

a) Select a collimator for therapy; place the film in a plane that is through the isocenter and perpendicular to the radiation beam axis; the equivalent water mold thickness on the film is at least 5cm; while the equivalent water mold thickness below the film is 5cm. Set the angle between accelerator frame and the speed-limiting system into 0°; select the appropriate energy and dose for the accelerator used in conjunction with; sequentially expose the film from the lower to the higher dose; so that calibrate the film gray scale value corresponding to different absorbed dose.

b) Use the appropriate mathematical model according to the absorbed dose value of the irradiation and the gray scale value of the corresponding film; draw a gray scale-dose response curve of the used radiation film;

c) According to the conditions of a), select appropriate dose to sequentially expose the collimator of each size; the irradiation dose shall be within the appropriate response area of the gray scale-dose response curve of the used film; process the film after exposure;

Yi - coordinate along the Y-axis measure after the ith repetitive positioning, in mm;

Z0 - coordinate along the Z-axis measured at the first time, in mm;

Yi - coordinate along the Z-axis measure after the ith repetitive positioning, in mm

5.8 Performance of therapy planning software

5.8.1 Dose calculation error of therapy planning software

It shall be performed as per the following methods.

a) The ionization chamber used for measurement shall meet the requirements of the measuring conditions. Use head model, separately take the three references points, i.e. model center and two isocenters as the targets to do three therapy plans; set the radiation dose of the target within the high-dose and low-gradient area; and finish the design of the therapy plan;

b) Insert the ionization chamber into the model; so that its effective measurement points overlap with the target;

c) Separately place the three targets at the accelerator isocenters; use the collimator adopted in the therapy planning and the radiation conditions to irradiate; measure the absorbed dose of the three targets;

d) Calculate the error between the absorbed dose value calculated by the therapy planning software as per the Formula (4) and the actually-measured absorbed dose value; the maximum value shall meet the requirements of 4.8.1. Where.

deltaP - the relative percentage error between he actually-measured absorbed dose value and the absorbed dose value calculated by the therapy planning, in %;

P0 - absorbed dose value of target calculated by the therapy planning software, in Gy;

Pi - actually-measured absorbed dose value (i=1~3) of target, in Gy.

5.8.2 Target position calculation error of the therapy planning software

It shall be performed as per the following methods. […]