Brachytherapy involves placing radioactive sources close to or in contact with the target tissue and can be used to treat gynecological cancers. Common radioactive sources include radium-226, cesium-137, cobalt-60, iridium-192, and iodine-125. Brachytherapy is often used in combination with external beam radiation therapy and can be given as low dose rate brachytherapy over many hours or high dose rate brachytherapy over minutes. It allows high doses of radiation to be delivered to the tumor while sparing surrounding healthy tissues.

1. Brachytherapy and GYN malignancy

2. Brachytherapy Brachytherapy ( brachy , from the Greek for “short distance”) consists of placing sealed radioactive sources close to or contact with the target tissue. Interstitial, intracavity, or transluminal approach. Temporary, or permanent implant. Low or high dose rate.

3. Introduction Discovery in 1898 Short distance (cm) High radiation dose can be delivered locally to the tumor with rapid dose fall-off in the surrounding normal tissue

5. Radioactive sources

6. Radioactive sources Radium-226 Average energy 0.83Mev (0.5mm of platinum) A filtration of at least 0.5mm platinum is sufficient to absorb all the α particles and most of the β particles emitted by the radium and its daughter products. Half life ~ 1600 years It was loaded into cells about 1cm long and 1mm in diameter . Radium sources are manufactured as needles or tubes in a variety of lengths and activities

7. Radioactive sources Cesium-137 Substitute for radium in both interstitial and intracavitary brachytherapy Energy 0.662Mev nearly the same penetrating power as radium Half life 30 years (clinically used 7 years without replacement) It was doubly encapsulated in stainless-steel needles and tubes.

9. Radioactive sources Cobalt-60 High specific activity Small sources required for some special applicators More expensive than 137 Cs and short half life (5.26 years) The sources can be used to replace 226 Ra in intracavitary application

10. Radioactive sources Iridium-192 It has a complicated γ ray spectrum with an average energy of 0.38 MeV. -> It required less shielding for personnel protection. It has the disadvantage of a short half-life (73.8 days) It is fabricated in the form of thin flexible wires which can be cut to desired lengths

11. Radioactive sources Iodine-125 Widely used for permanent implants. Longer half-life: 59.4 days (convenient for storage) Low photon energy (0.028MeV) -> less shielding. Disadvantages: dosimetry of 125 I is much more complex.

12. Brachytherapy Permanently Implanted 0.19G/h 17 22keV 13 Pd 0.07G/h 59.6 28keV 125 I 1.07G/h 2.70 412keV 198 Au 0.75G/h 3.83 1.2MeV 222 Rn Dose Rate T1/2 Energy Source

13. Radioactive sources ICRU38 LDR sources: 0.4-2 Gy/hr ( 137 Cs) HDR sources: ≥ 12 Gy/hr ( 60 Co, 192 Ir) 226 Ra  leakage Radon gas. 137 Cs better than 226 Ra  less shielding and microsphere form with leakage gas. 137 Cs better than 60 Co  less shielding and cheap. 192 Ir better than 137 Cs  lower energy require less shielding for personnal protection and higher specific activity. 103 Pd better than 198 Au and 125 I  less shielding and biologic advantage .

14. Radioactive sources Short treatment times and minimal radiation protection problems . Possibility of optimizing dose distribution by altering the dwell times of the source at different Longer treatment times allow for leisurely review of and potential modifications to the treatment . Plan prior to the delivery of a significant portion of treatment. Favorable dose-rate effect on repair of normal tissues . Infrequent replacement and calibration of sources because of long isotope half-life. Physical Maintain position of the sources during the brief treatment. Patient preparation. No specialized nursing. Ability to treat great patient loads. Improves chances of atching tumors in sensitive phase of cell cycle. Clinical No long term confinement to bed . No indwelling bladder catheters. Not labeled “radiation risk zone” to relative, visitors, and staff. Avoid several anesthesias. Long history of use. Ability to predict rate of late complications Patient High Dose Rate (HDR) Low Dose Rate (LDR)

17. Brachytherapy and GYN Malignancy

18. Reference point from which lymph node position were measured on lymphoangiograms and the range of location Int. J Radiat Oncol Biol Phys 34:167-172, 1996

19. Distribution of pelvic node metastases in patients with Ib-IIa cervical cancer Gynecol Oncol 62:19-24, 1996 Tumor size <=4 cm Local advanced tumor

20. External beam radiotherapy for GYN Malignancy

21. Pelvic irradiation portal in cervical cancer 4-field box technique

22. Pelvic irradiation portal in cervical cancer 4-field box technique

24. Combination of external beam pelvic irradiation and intracavitary brachytherapy (ICRT)

25. Brachytherapy in definitive radiotherapy of cervical cancer (Intracavity radiotherapy, ICRT)

26. Intracavitary Radiotherapy (ICRT)

30. Applicator of ICRT

33. Intracavitary insertion (ICRT)

40. Postoperative brachytherapy (Intravaginal radiotherapy)

41. Intravaginal radiotherapy (IVRT)

44. Female urethral cancer

46. Endometrial cancer