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Brachytherapy And Gyn Malignancy

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  • 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
  • 4.  
  • 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.
  • 8.  
  • 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)
  • 15.  
  • 16.  
  • 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
  • 23.  
  • 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)
  • 27.  
  • 28.  
  • 29.  
  • 30. Applicator of ICRT
  • 31.  
  • 32.  
  • 33. Intracavitary insertion (ICRT)
  • 34.  
  • 35.  
  • 36.  
  • 37.  
  • 38.  
  • 39.  
  • 40. Postoperative brachytherapy (Intravaginal radiotherapy)
  • 41. Intravaginal radiotherapy (IVRT)
  • 42.  
  • 43.  
  • 44. Female urethral cancer
  • 45.  
  • 46. Endometrial cancer