LDR and HDR Brachytherapy: A Primer for non radiation oncologists

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: Sealed radioactive sources Intra / peri-tumor placement Geometrical Arrangement Image: wired.com

3. Primer on Sources Radioactive sources: Natural Man-made Sealed. Most Common: Iridium 192 Cobalt 60 Cesium 137 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: Amount of Radioactive source implanted Point of measurement.

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

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

8. LDR vs HDR : Sources Low specific activity Various forms: Wires Needles Tubes Inventory required Personnel protection : distance and time High specific activity Single form: 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: Lethal Sub - lethal Sublethal damage can be repaired 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: Normal cells: 2 - 4 hours . Tumor cells: 0.5 - 1 hour . So during LDR treatment - repair of damage also occurs.

12. LDR vs HDR : Biology In HDR treatments: Sublethal damage is not repaired. 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: HDR is given in lower total dose Correction factor of 0.6 used . Implies for a LDR dose of 70 Gy, HDR dose will be 42 Gy 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: DVT Pressure Ulcers Low residue diet Pain Applicator displacement

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

17. LDR vs HDR : Nursing Radioactive source placed inside patient for a long time: Barrier nursing Isolation of patient 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: Logistical advantages Dosimetric advantages Radiation Protection advantages

21. Thank You