WEEKLY CHECKS

The weekly checks are as follows: 1. Treatment room door switches - This ensures that the exposure of the source is inhibited if the doors are open.

2. Radiation warning light - The correct operation of the radiation warning lights at the entrances is checked, as is the operation of, and recovery from, the use of the emergency stop button.

3. Emergency stop - The correct operation of the use of the emergency stop button is checked.

4. Portable radiation monitor - This is checked once per week on our schedule, and if necessary, batteries are replaced.

5. Correct operation of microselectron-HDR and applicator - This is done to ensure that the system is left in working order.

MONTHLY CHECKS

The monthly checks are carried out on the following areas:

1. Timer check - the timer is checked by comparison with an independent electric timer, over a period of several minutes.

2. Source strength - measurements are made to determine the output in terms of air kerma rate at a specified distance from the source. The purpose of this check is primarily for us to confirm, and to place on record, that the clinical data used for treatment is still appropriate, having been accurately decay corrected by the microSelectron-HDR or the planning system. It also indicates that the source is undamaged and that the unit is operating as expected.

THREE MONTHLY CHECKS

These consist of the following:

1. Check on the cable and on source positioning - are checked by a device known as the calibration rule. This consists essentially of a transparent applicator, mounted adjacent to a distance scale marked in mm. A white plastic marker can be pushed down into the lumen of the applicator so that the check cable, when operated, will push this marker along the tube and therefore indicate its furthest position of travel.

2. Source strength calibration - is performed using a perspex jig. It consists of a perspex tube, designed to hold the thimble ionization chamber, around which there are four smaller tubes; each designed to take a microselectron-HDR.

3. Contamination test - is checked for the leak of the sources.

4. Applicator checks - are examined for wear and tear by a physicist.