afterloader at NSHA

Question 1

name of afterloader at NSHA

Answer 1

Nucletron microselectron remote afterloader

Question 2

source change frequency

Answer 2

every 3 months

Question 3

activity of new souce vs old source at source change

Answer 3

11 Ci vs 5 Ci

Question 4

How many in-room radiation detectors are there?

Answer 4

2- There is one on the afterloader and one on the wall of the room. The one on the afterloader causes yellow radiation symbol to light up in control room and on afterloader handle. The one on the wall of the treatment room causes a red light to flash on the wall of the control room.  two independent checks.

Question 5

explain the HDR source out indicator light

Answer 5

tied to a sensor in the afterloader that checks if the source cable has deployed – not actually measuring radiation

Question 6

How much further does check cable go compared to source cable?

Answer 6

2 mm further

Question 7

explain the afterloader battery backup

Answer 7

(emergency power source; EPS) which retracts the source in the event of a power outage and powers the computers in the control room. During quarterly source change, the engineer checks that this is working and that the backup battery has adequate charge.

Question 8

how does engineer test the emergency stop buttons in the room during quaterly source change?

Answer 8

before installing the new source (and after removing the old source), the engineer puts in an inactive dummy source, which is used to test the emergency stop buttons within the room

Question 9

what checks which channel is being used?

Answer 9

 LED lights and fibre optic cable system

Question 10

why do we want transfer tubes to be as straught as possible?

Answer 10

don’t want to perturb the distance travelled by the source

Question 11

3 important parameters for brachy planning

Answer 11

time (dwell time and time since calibration)
position
path

Question 12

3 important parameters for brachy radiation protection

Answer 12

time
distance
shielding

Question 13

dwell positions in relation to the afterloader

Answer 13

 Surface of indexer is position 0 cm. 150 cm is the most distal (relative to the afterloader) position for most catheters.
• Treatments are delivered starting in the position that is the most proximal to the machine and then goes out from there, then comes all the way back
• What is referred to as the “first” dwell position is typically the most distal from the afterloader.

Question 14

how many times is check cable sent out for source cable?

Answer 14

 Check cable goes out twice for every one time the source goes out. The check is first sent out to all channels at the beginning of treatment. Then for each channel, the check cable is sent out again, followed by the source; and repeat for all channels.

Question 15

what to do with daylights savings time?

Answer 15

ignored since 1 h only makes 0.06% decay

Question 16

what reading on wipe tests warrants investigation?

Answer 16

reading twice higher than the background

Question 17

during quaterly source change, what else is checked

Answer 17

• backup battery is working and holding enough charge
• emergency stop buttons in room are working
• source and check cable are replaced periodically since some parts wear out over time
• primary check of source strength and 2nd check of strength (E2E test of a brachy plan) with Matrixx