A small presentation I made for a 30 minutes class comparing and contrasting LDR and HDR brachytherapy. Good for a person with non radiation oncology background to grasp the basics.

1. Brachytherapy
LDR and HDR:
A Primer
Dr Santam Chakraborty
Radiation Oncology

2. Brachytherapy
● Derived from: Brachys (Gr.) -
short range/ distance
● Involves:
o Sealed radioactive sources
o Intra / peri-tumor placement
o Geometrical Arrangement
Image: wired.com

3. Primer on Sources
● Radioactive sources:
o Natural
o Man-made
● Sealed.
● Most Common:
o Iridium 192
o Cobalt 60
o Cesium 137
o Radium 226

4. What is dose
● Dose : Amount of energy absorbed per unit mass of
tissue.
● Energy deposition : Ionization
● Unit : Gy

5. What is Dose Rate
● Amount of Dose per unit time.
● Earlier : Exposure per unit time
● Depends upon:
o Amount of Radioactive source implanted
o Point of measurement.

6. Size does matter ..
High specific activity of Iridium makes miniaturization
possible.

7. Types of Dose Rate
1. Ultralow dose rate: 0.01 - 0.03 Gy / hr
2. Low dose rate (LDR): 0.4 - 2 Gy / hr
3. Medium dose rate (MDR): 2 - 12 Gy /hr
4. High dose rate (HDR): > 12 Gy / hr

8. LDR vs HDR : Sources
● Low specific activity
● Various forms:
o Wires
o Needles
o Tubes
● Inventory required
● Personnel protection :
distance and time
● High specific activity
● Single form:
o Tubular source
● Inventory not required
● Personnel protection:
NA (cannot be handled)

9. Equipment...
L Bench Selectron Microselectron

10. LDR vs HDR : Biology
● Biological implications - related to how well cells
repair radiation induced damage.
● Radiation induced damage:
o Lethal
o Sub - lethal
● Sublethal damage can be repaired
o Provided we give time to the cell !!

11. LDR vs HDR : Biology
● In LDR treatment times are in the range of 60 - 144
hours.
● Repair half times:
o Normal cells: 2 - 4 hours.
o Tumor cells: 0.5 - 1 hour.
● So during LDR treatment - repair of damage also
occurs.

12. LDR vs HDR : Biology
● In HDR treatments:
o Sublethal damage is not repaired.
o As a result cell kill is more.
● As a result normal cells are damaged MORE with
HDR as compared to LDR if the SAME dose is used.

13. LDR vs HDR : Biology

14. LDR vs HDR : Biology
● To circumvent this problems:
o HDR is given in lower total dose
o Correction factor of 0.6 used.
 Implies for a LDR dose of 70 Gy, HDR dose will be 42 Gy
o Also dose is fractionated
 Typical fraction sizes :3.5 - 7 Gy.
 Interfraction gap: 6 hours.

15. LDR vs HDR : Nursing
Several nursing implications for LDR brachytherapy:
● Prolonged treatment time:
o DVT
o Pressure Ulcers
o Low residue diet
o Pain
o Applicator displacement

16. LDR vs HDR : Nursing
Several nursing implications for LDR brachytherapy:
● Prolonged treatment time:
o DVT
o Pressure Ulcers
o Low residue diet
o Pain
o Applicator displacement

17. LDR vs HDR : Nursing
● Radioactive source placed inside patient for a long
time:
o Barrier nursing
o Isolation of patient
o Personnel dosimetry

18. LDR vs HDR : Cervical Cancer
http://www.jeccr.com/content/28/1/47

19. LDR vs HDR : Oral Cancer
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0065423

20. Summary
● Though potentially radiobiologically superior LDR
superseded by HDR:
o Logistical advantages
o Dosimetric advantages
o Radiation Protection advantages

21. Thank You