Localisation

Question 1

What is the patient positioning?

Answer 1

Head first supine
Hands on chest

Question 2

What is the patient immobilisation?

Answer 2

Combifix (knee rest & foot stocks) - indexed and stabilises the knees.

Head rest - aimed towards patient comfort.

Question 3

Describe fiducial markers process

Answer 3

1 week before planning, markers inserted into prostate using a transrectal ultrasound.
3-4 inserted.
These allow matching on treatment using KV pairs as it gives a lower dose.

Question 4

Describe a rectal spacer

Answer 4

Bio synthetic gel inserted transrectally,
To create space between prostate and anterior rectal wall.
Usually inserted along with fiducials

Question 5

What is the patient prep?

Answer 5

The bladder should be comfortably full around 250ml.

Enemas should be used for bowel prep to empty rectum.

IV contrast used to delineate the pelvic blood vessels

Question 6

What are the landmark positions?

Answer 6

Ant tattoo in pubic symphysis region

Lateral tattoos both over iliac crest in line with the ant tattoo.

Question 7

What are the scanning parameters?

Answer 7

L3/L4 (L1/L2 - NODES) to 2cm below ischial tuberosities.

Slice thickness would be 2-3mm

Question 8

Describe localisation fully.

Answer 8

1. 1 week before planning scan the patient has 3-4 fiducial markers inserted into the prostate transrectally to allow match on treatment.
2. Rectal spacer is also inserted to create space between the prostate and the anterior rectal wall.
3. Patient would come in for the scan and be asked to drink water until they have a comfortably full bladder that they can hold, around 250ml so it can push the bowel out of the field. They would be asked to use an enema to empty their rectum so it remains the same throughout treatment.
4. The patient then lays on the couch head first supine and aligned to the midline which consists of SSN, TOX and UMB with their hands on chest to keep hands away from treatment field.
5. The immobilisation used is a head rest for patient comfort and combifix indexed to stabilise the knees.
6. Some pen marks are made to mark the reference points. The anterior marker is marked in the pubic symphysis region and the lateral markers are marked over the iliac crests. CT spots are placed above the pen marks so they can be visible on the scan.
7. The bed is 0’ed and the red laser is turned on and should align to the ct spots.
   The bed is taken out until the thorax region in Southend to get ready for the scan and the red laser is turned off.
8. A control scan is taken to check the bowels. If the rectal diameter is less than 4cm, then a full scan is taken, if out of tol then patient is asked to get off take another enema or walk around.
9. The scanning levels is l3/l4 interspace to 2cm below the ischial tuberosities. (L1/L2 for nodes) with the slice thickness of 2-3mm
10. Scan is completed and then the pen marks would be made into permanent tattoos, so they can help patient align in the same position every fraction.