1. Brachytherapy: Clinical implementation LDR/HDR Kent A. Gifford, Ph.D.

2. Prostate seed LDR (PPI)
Advantages
Dose conformity, normal tissue sparing
Continuous LDR delivery
Monotherapy can ablate prostate cancer cells
“One and done” procedure
No concerns about EBRT motion, setup uncertainties

3. Prostate seed LDR (PPI)
Disadvantages
Rapid falloff of ~25keV photon sources
Edema of implant
Variability of manufacture and activity of sources
Interseed and Intraseed attenuation
Subject to skill/experience of brachytherapist (art??)

4. Prostate seed LDR (PPI) Seed properties
Radionuclide
Cs-131
I-125
Pd-103
Half-life (days)
9.65
59.4
16.97
Average Energy (keV) 29 27 21
Λ (cGy hr-1 U-1)
1.05
0.69
Half-value layer (mm)
0.035
0.025
0.008

5. Monotherapy and boost doses
Isotope
Cs-131
I-125
Pd-103
Monotherapy dose (cGy)
Boost (cGy)
70-80
80-110

6. Treatment Guidelines Seeds
I-125: Nycomed-Amersham Model 6711 (NIST 99)
Pd-103: Theraseed Model 200 (NIST 99)
Activities used at MD Anderson
I-125: .391 mCi = .497 U (used in planning software)
Pd-103: 1.4 mCi= U
Will use 1 week decayed sources with a 7.77% decay; .361 mCi= .457 U

7. Treatment Guidelines Cont.
Doses are given as the total dose given over the life of the radioactive seed (decayed to 0 mCi)
Planned dose - TG 43
Full Dose: Brachytherapy only
I-125: 145 Gy
Pd-103: 115 Gy
External Beam + Brachytherapy
XRT 45 Gy + I Gy
XRT 45 Gy + Pd-103: 100 Gy

8. Advantages and Disadvantages of Seed Types
NIST Traceable Calibration
Well Characterized dosimetry
Rapid Strands available
Disadvantages
Relatively long half life
Rounded seed ends makes them mobile
Very anisotropic dose distribution
Pd-103
Advantages
Short Half Life
Cupped seed ends tend to anchor seeds
Seed activities within +/- 5%
Disadvantages
No calibration standard
Dosimetry based on only two studies
Activity decays 4% a day

9. Which to use? I-125 or Pd-103
Generally use Pd-103 for higher grade tumors
The disadvantage is Pd-103 short half life – may miss the slower growing tumor cells.

10. Pd-103 Seed in comparison with I-125 Seed

11. Prostate Implants at MD Anderson
Modified Peripheral Loading based on Seattle technique
Pre-Plan/ Pre-loaded technique
Use I-125 seeds, Pd-103, Cs-131
Pre-Implant Ultrasound Volume Study performed 2 weeks to a month before actual implant by the Radiation Oncologist and Resident
Plan based on ultrasound images acquired during volume study

12. Implants at MD Anderson Cont.
Varian Variseed computer software used for planning
Implant performed under anesthesia as an outpatient procedure
Post Implant CTs performed on Day 1 and Day 30 (2 wks potentially for Pd-103, Cs-131)

13. Pre-Implant US Volume Study
2 weeks to a month before actual implant
scheduling
ordering of seeds
Done in Urology with the patient awake
Procedure time: min.
Patient positioned in stirrups similar to those in the operating room
Transrectal Ultrasound (TRUS) used to acquire images

14. TRUS Imaging Diagram

15. Pre-Implant US Volume Study
Without a good volume study a good plan can not be designed
Oncologist draws target volume, tissue that is identified to be treated on each 5 mm slice
Prostate Volume is determined from the prostatic margin
The target volume includes the prostate volume and some of the surrounding tissue
Ultrasound study is done in Urology
Considered an art to find prostate margins on US although the imaging with new units has improved significantly over the years
The target may appear outside of the prostate margin but due to uncertainty of margins this is OK
Take slices 5 cm caudal to the apex and 5 cm cephalad to the base
Do a sagittal image

16. Pre-Implant US Volume Study

17. Pre-Implant US Volume Study
KY Jelly or Ultrasonic Gel used as medium for ultrasound transmission
Condom placed over the probe
Standoff cap used for prostates that lie posteriorly
Requirements for adequate ultrasound images
complete contact between transducer and the medium
absence of air in the medium
good contact with the rectal wall
absence of gas or stool in the rectum

18. Pre-Plan

19. Variseed Software: Template Registration
3 Point Method
1.) Lower Left Location: A 1.0
2.) Lower Right Location: G 1.0
3.) Designated Row: Any Hole (usually row 5)
Template (in red)

20. Contours

21. Source Placement Set Reference Plane to Base Slice (0.00 cm)
Right Click on image when highlighted in big window

22. Planning Guidelines Pre-Implant US Volume Study ultrasound images used
Modified Peripheral Loading Technique
Base Pattern- basic pattern of needles that begin at the base of the prostate
Implant small letters (a,b,c,d…) and whole integers (1.0, 2.0, 3.0…) starting with the base slice
Place needles and seeds in the template locations in the prostate or within 1/2 cm from prostatic capsule delineated by the contour
Continue pattern every 1 cm

23. Base Pattern Base Slice 0.5cm Slice 1.0cm Slice 1.5 cm Slice

24. 0.0 cm Slice (base)

25. 1.0 cm Slice

26. 2.0 cm Slice

27. 3.0 cm Slice

28. Planning Guidelines Cont.
Patching Pattern- On the slices with a retraction of a 1/2 cm from the previous pattern-
Implant at the big letters (A,B,C,D…) and the half-integers (1.5, 2.5, 3.5,…)
Place needles and seeds in the template locations in the prostate or within a 1/2 cm from the prostatic capsule delineated by the contour
Avoid the “Big D” column due to the position of the urethra
Continue pattern every 1 cm
Modify central needles for urethral sparing
remove complete needles if 100% isodose line sufficiently covers the prostate
Remove central seeds in the needles- leave seeds at base and apex

29. Patching Pattern Base Slice 0.5cm Slice 1.0cm Slice 1.5 cm Slice

30. 0.5 cm Slice

31. 1.5 cm Slice

32. 2.5 cm Slice

33. 3.5 cm Slice (apex)

34. Remove seeds from “c,d” between rows 2 and 3
0.0 cm slice
2.0 cm slice
Urethral Sparing
Remove seeds from “c,d” between rows 2 and 3
1.0 cm slice
3.0 cm slice

35. Remove seeds from “C & D” between rows 2.5 and 3.5
0.5 cm slice
1.5 cm slice
Urethral Sparing
Remove seeds from “C & D” between rows 2.5 and 3.5
2.5 cm slice
3.5 cm slice

36. Considerations when Planning
Dipping of the 150% isodose line down the center of the gland - urethral sparing
Don’t compromise the 100% isodose line for urethral sparing

37. Dipping of 150% Isodose Line
Urethral
Area
150% Line
150% Line

38. Considerations when Planning
Dipping of the 150% isodose line down the center of the gland - urethral sparing
Don’t compromise the 100% isodose line for urethral sparing
No needles can have less than 2 seeds
Try to keep the needle count < 30
Optimal prostate sizes to implant: cc
The length of the urethra that receives more than 400 Gy for I-125 should be kept as low as possible

39. Considerations when Planning
Plan with sufficient dose at the base
loose periprostatic tissue has a high probability of causing seed migration
a more extended lithotomy position during implant causes the base slice to be larger
decreases total number of slices
area with most cold spots, due to anatomical position
Load posteriolateral aspects of the prostate light
location of neurovascular bundles
seed migration very likely
Symmetry is important for uniform dose

40. Considerations when Planning
Solutions for prostates that lie posteriorly
drop the needles in the “big letter (A,B,..)” columns from the half-integers (1.5,2.5,…) to the whole integer (1.0,2.0,…) rows below them
follow loading guidelines despite modifications
Avoid the rectum as much as possible by loading the central template locations cooler (“big” C-E)
Rectal dose should not exceed 100 Gy
Do not implant or include the seminal vesicles due to unreliable source placement

41. Considerations when Planning
Mid-gland- generous coverage laterally and anteriorly, no margin posteriorly because of the rectum
Recommended to load 70% on the periphery and 30% on the interior
Hot spots in the interior of Gy can be expected
145 Gy line should extend 3-5 mm beyond the margin drawn

42. Final Plan
Images 1 - 4
Images 5 - 8
Images

43. Seed Assay and Loading 10% of seeds assayed and then sterilized
Loaded under a sterile environment
Seeds loaded according to VariSeed computer printouts
seed positions with correct orientation
most needles loaded with a seed to begin with and then a seed at every cm with a spacer in between each seed
each needle ends with a seed due to doctor preference
Once all the needles are finished then a verification film must be taken to assure that the needles are loaded correctly

44. Prostate Seed Implant Needle QA Films

45. Needle Loading Box
Based on the plan and template location, the needles are placed in the needle box after verification and taken up to the Operating Room the following day

46. Operating Room Procedures
In the Operating Room the patient will be returned to the same position as they were in for the pre-plan (a catheter will be placed with contrast in the Foley balloon)
Fluoroscopy used
The Physician will need the pre-planning US to check for patient position for the implant
Need patient plan, loading diagram, small lead pig, calculator, NaI detector, Geiger-Mueller detector and any radiation safety forms you may need should the patient require a stay in the hospital over night

47. Operating Room Setup

48. OR Procedures
Coordinates of the needle and retraction of the needle are read from the treatment plan
When all the needles have been loaded, the extra needles will be used to fill in at the apex and any “cold” spots
This is done using fluoroscopy as well as ultrasound
The urologist will do a cystoscopy to ensure there are no seeds in the bladder, if there are seeds they will be retrieved and put in the little lead pig

49. OR Procedures
Make a note in the patient chart with total seeds and needles, total activity, and survey meter reading of the patient with the Geiger detector
You must remain in the OR until every seed has been accounted for!!!
Once the patient has left the room, use the NaI detector to survey EVERYTHING.
X-ray taken of last fluoroscopic image to verify the number of seeds implanted (verification)

50. Verification Fluoroscopy Image

51. Post-Implant Dosimetry
Seed Identification- 5 mm CT scan example

52. Post-Implant Dosimetry
3-D Dose Reconstruction with Dose 100% isodose cloud (2 different cases)

53. Post-Implant Dosimetry
Timing of CT Scans
Edema
Average swelling- 20%-50% post implant (Range: 0-96%)
calculated by interseed spacing
prostate border delineation not as accurate of a measurement
T 1/2 = 10 days
D90 increases 30 % from day 1 to day 21
Anderson’s experience- prostate back to normal by day 30
Volume increase results in average of 10% underestimate of dose
Suggested Timing between 2 post-implant scans: Pd weeks, I weeks

54. Post-Implant Dosimetry
Dose Evaluations
Isodose Distributions
2-D distributions on sequential slices of target
Recommended isodose lines: 200%, 150, 100, 90, 80, and 50.
Dose Volume Histograms (DVH)
Cumulative DVH recommended
Percent volume of prostate that receives greater than or equal to dose delivered
Report following:
D100, D90, D80 (dose that 100% of the prostate receives)

55. Implementation, QA, physicist responsibilities- TG-56
Nath et al., Med. Phys. 24(10)

56. Implementation, QA, physicist responsibilities
Nath et al., Med. Phys. 24(10)

57. Implementation, QA, physicist responsibilities
Nath et al., Med. Phys. 24(10)

58. Implementation, QA, physicist responsibilities
Nath et al., Med. Phys. 24(10)

59. Implementation, QA, physicist responsibilities
Nath et al., Med. Phys. 24(10)

60. Implementation, QA, physicist responsibilities
Nath et al., Med. Phys. 24(10)

61. Implementation, QA, physicist responsibilities
Nath et al., Med. Phys. 24(10)

62. Implementation, QA, physicist responsibilities
Nath et al., Med. Phys. 24(10)