prostate hdr technique

High dose rate brachytherapy for prostate cancer TECHNIQUE

Peter Hoskin Mount Vernon Cancer Centre

Northwood UK

Bladder 1 2 3 4 5 6

TRUltrasound 5 mm planes

Rectum

7 8

Steps in HDR prostate brachytherapy

• Implantation • Volume definition • Dosimetry planning • QA • Treatment delivery

TRUS stepper unit Set up is critical for Implant geometry

• TRUS guided •Transaxial and sagittal

• SET UP:

•Baseline to include posterior capsule and seminal vesicles •Urethra along Row D •Minimise probe pressure

•

Implant technique

Catheter insertion TWO SCHOOLS

Peripheral Uniform

Tips for a good implant

• Good peripheral coverage is essential

• Pay particular attention to superior catheters and baseline

• Monitor both transaxial and sagittal images; scroll through prostate length regularly

Positioning of posterior template row is crucial Adjustment through probe position and build up cap

Baseline definition Is critical Do not elevate gland Ensure inferior row will cover bottom of CTV …………… allow for any expansion

HDR implant: seminal vesicles

‘Overinsertion’

Needle / catheter fixation

• Rigid needle template

• Flexible latex template

CTV definition

• Ultrasound

• CT

• MR

Vitesse • Intraoperative HDR planning • Eliminates the CT scanner step • Plan is created in parallel with patient

recovery using Brachyvision

Offenbach

HDR implant: volume definition

5mm planning CT Volume defined on screen

HDR implant: volume definition

MR vs CT outlining • CT: better needle tracking • MR: better soft tissue definition • Image registration:

– NB potential matching errors

CTV criteria GEC ESTRO guidelines

Kovacs et al 2006

• CTV1: whole gland defined by capsule – Margin around capsule may be added 3 –5 mm

• CTV2: peripheral zone

• CTV3: GTV

• PTV = CTV

Peripheral loading

Homogeneous loading

Seminal vesicles

Probability of ECE and seminal vesicle invasion [Partin 2001]

ECE SV PSA 6.1-10 T2b Gl 3+4 52% 16% Gl 4+3 60% 13% Gl 8-10 57% 17%

Rades et al 2007

Quality control

Single step technique: Movement of template with catheters

Baltas 2009

DAY 1 DAY 2

DAY 1 DAY 2

Silicon Template

at skin

Catheter shift between fractions

HDR implant: verification for multiple fractions

Repeat skin to hub measures Repeat limited CT Adjust catheters Recalculate dose distribution

Presenter

Presentation Notes

Second possible source of error is internal movement of the prostate itself, due to rectal and bladder filling and emptying - allowing the prostate to sup/inf over the needles. Final possible source of error is tissue oedema between the prostate apex and the perineum due the local trauma of the implant to this region. This swelling causes the template to migrate in the caudal direction, causing the template to pull the needles back with it due to its effectiveness as a fixation device. Minimum QA to observe these two possible sources of error is a CT prior to the second fraction to assess the internal movement of the prostate with respect to the catheters. Patient aligned in CT using tattoos, with the tattoo slice being used as a reference slice. To allow the first fraction plan to be used corrective action may need to be implemented.

Prostate movement from CT before 1st and 2nd fractions

Mean 11.5mm Median 9.7mm Range 0-42mm

20 consecutive monotherapy implants 31.5Gy in 3 fractions in 2 days

RT&O 2009

Impact of implant dosimetry on local control Kovacs: Kiel

69 patients with local failure

HDR Brachytherapy

• Meticulous technique • Individualised dosimetry • Good QA

prostate hdr technique

Health & Medicine

fractions hdr implant

planning ct volume

baseline definition

impact of implant dosimetry

implant geometry

limited ct

prostate movement

mr vs ct outlining ct