Evolution of gynaecological brachytherapy


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Evolution of gynaecological brachytherapy

  1. 1. Dr. Ritam Joarder R.G.Kar Medical College
  2. 2. Down the memory lane…… 1895: Discovery of X-ray by Röntgen 1896: Discovery of Radioactivity by Becquerel 1898 : Discovery of Radium & Polonium by Marie Curie and Pierre Curie
  3. 3. Pierre made a rubber capsule of 0.398g of radium sulfate for Dr.Danlos of St.Luis Hospital Dr. Henri Danlos and Paul Blotch in 1901 successfully treated lupus skin lesion with Radium
  4. 4. “… there is no reason why a tiny fragment of radium sealed up in a glass tube should not be inserted into the very heart of the cancer; thus acting directly upon the diseased material. A.G. Bell Letter to Science, 1903
  5. 5. In 1903 Gynecological Brachytherapy was first introduced by……. On 15 September 1903 she treated an inoperable cancer of the cervix uteri with 700 milligrams of radium bromide sealed in a glass tube. Two applications of 10 minutes each were made with an interval of 3 days between. O'Brien, F. w. (1947): Amer. J. Roentgenol., 57, 281. Margaret Abigail Cleaves And The Journey Begins Here ……
  6. 6. The dose prescription was entirely empirical Due to lack of – Knowledge about the biological effects of radiation on the normal tissues and the tumor Understanding about the dose, dose distribution and the duration of treatment The Concept of Dosimetric system was introduced Dosimetric systems denotes a set of rules taking into account the source strengths ,geometry and method of application in order to obtain suitable dose distributions over the volume(s) to be treated.
  7. 7. Evolution of Gynecological Brachytherapy Systems
  8. 8. Intracavitary systems Interstitial systems Edith Quimby Quimby System Gosta Forssell Stockholm System R. Paterson & H.M Parker Manchester System Claude Regaud Paris System M.C.Todd Manchester System B .Pierquin & A. Dutreix Paris System
  9. 9. Stockholm system Developed by Gosta Forssell by 1913 in Radiumhemmet , Stockholm Later perfected by James Heyman and Hans Kottmeier  Fractionated (2--3 applications) delivered within about a month  Each application 20--30 hours  The amount of Radium was unequal in uterus (30--90 mg, in linear tube) and in vagina (60--80 mg, in shielded silver or lead boxes)  Vaginal and uterine applicators were not fixed together  Total mg--hrs were usually 6500 to 7100 out of which 4500 mg were in vagina.
  10. 10. Paris system Developed by Claude Regaud by 1922 in Institute du Radium , Paris 2 applicators were used a) Uterine applicator containing 13·33 + 13·33 + 6·66 mg. tubes of radium loaded in tandem fashion. b) Vaginal colpostat and cork together containing 33·32 mg. of radium.  Single application of 120 hrs.  Vaginal and uterine applicators were not fixed together.  Total dose given to both uterus and vagina was 30 m.c.d (4000 mg-hr)
  11. 11. When compared……  Uterine sources in both systems were arranged in a line extending from the external os to nearly the top of the uterine cavity.  Both systems preferred the longest possible intrauterine tube to increase the dose to paracervical region and pelvic region lymph nodes. There was a limited use of external beam therapy in Stockholm system, whereas Paris system used external beam therapy before the implant.
  12. 12. Manchester system Developed by M.C.Todd & W.J.Meredith in 1938 in Holt Radium Institute ,Manchester Later revised in 1953 Normal Tissue Tolerance : “ paracervical triangle," ……… as roughly pyramidal in shape, with its base resting on the lateral fornix and the apex curving round with the anteverted uterus ”
  13. 13. Manchester system “ point A is 2 cm. lateral to the central canal of the uterus and 2 cm. from the mucous membrane of the lateral fornix in the axis of the uterus” “ a secondary point, designated B, five centimetres from the mid-line and on the same level as Point A, is either in or near enough the node to be used to give a measure of the dose received by it.”
  14. 14.  Initially used radium units were 6.66mg but later changed to 2.5 mg each.  Two application 72hrs apart with 4 days in between  Dose of 8000R was delivered at pt A when radium used alone for stage I/II ds  When radium was used along with deep-X ray therapy for stage III or IV ds radium dose to pt A reduced to 6500R.
  15. 15. Paterson-Parker system Dosage : 1. because 2. 3.
  16. 16. Single Plane Implant : Rule 1: A fraction of the total activity is placed on the periphery of the target volume with the remainder spread uniformly over the interior. Implant Area Fraction on Periphery < 25 cm2 2/3 25 – 100 1/2 > 100 1/3 Rule 2: The needles should be arranged in parallel rows 1 cm apart with the ends crossed. Rule 3: If the ends of the implant are uncrossed, the area should reduced by 10 % for each uncrossed end for table reading purposes.
  17. 17. Cylindrical volume Implant : 1. Total amount of Ra-226 is divided into 8 parts: 4 parts in the belt, 2 parts for core, and each end 1 part. 2. Needles should be parallel, spaced uniformly and not more than 1 cm apart. 3. 7.5% is reduced from the volume for uncross end for table reading purpose. 4. The stated dose in 10% higher than min dose in the volume.
  18. 18. Quimby system Developed at Memorial Hospital, NYC in 1930s and 1940s by Edith Quimby for Ra sources spaced R26 needles • The Quimby system is characterized by a uniform distribution of activity. • Leads to higher dose in the central portion of the implant. • Designed for interstitial implants using radium needles. • Implantation Rules: Lookup tables give number of mg-hr/1000 R in the center of the treatment plane (top or bottom of a planar implant). Stated dose is the maximum dose in the treatment plane. Sources are spaced 1 cm apart and of same strength. Ends are crossed.
  19. 19. Quimby based systems using Ir-192 seeds in ribbon • Kwan System ( Kwan et al. 1983) • Tufts System ( Zwicker et al. 1985) • Memorial System ( Anderson et al. 1986) • Saw System ( Saw et al. 1988)
  20. 20. Evolution of Gynecological Brachytherapy Sources
  21. 21. What is an Ideal Radionuclide? • Easily available & Cost effective • Gamma ray energy high enough to avoid increased energy deposition in bone by PEE & low enough to minimise radiation protection requirements • Preferably monoenergetic: Optimum 300 KeV to 400 KeV (max=600 kev) • Absence of charged particle emission or it should be easily screened (Beta energy as low as possible: filtration) • Half life such that correction for decay during treatment is minimal • Moderate gamma ray constant (determines activity & output) & Godden ,1988 also determine shielding required.
  22. 22. What is an Ideal Radionuclide? • No radioactive daughter product; No gaseous disintegration product to prevent physical damage to source and to avoid source contamination • High Specific Activity (Ci/gm) to allow fabrication of smaller sources & to achieve higher output (adequate photon yield) • Material available is insoluble & non-toxic form • Sources can be made in different shapes & sizes • Disposable without radiation hazard to environment • Isotropic: same magnitude in all directions around the source • No self attenuation Godden ,1988
  23. 23. Radium • • • • • • • • • Earliest & once the most commonly used isotope Naturally occuring ,extracted from Pitchblend ore T ½ =1622 yrs Disintegrates very slowly to hazardous radioactive gas Radon (Rn222) Energy- ranging from 0.184 MeV - 2.45 MeV (avg.0.83Mev) Some high energy β rays (max.3.26 Mev) β filtration : 0.5 mm of platinum Has been widely used for intracavitary,interstitial & mould applications Radium sulfate/Ra chloride mixed with inert filler & loaded in cell(1cm long &1mm in dia.made of 0.1-0.2 mm thick Gold foil). Uranium T1/2 Ra 1620Yrs α Rn 3.83days α RaA 3.05min • Exposure rate constant : 8.25 R cm² /mg-h α RaB 26.8min βγ βγ RaC Pb 19.7min Stable
  24. 24. TYPES OF RADIUM SOURCES Shapes : Uniform o.33mg/cm 0.66mg/cm Indian Club 0.66mg/cm 0.33mg/cm 0.66mg/cm Dumb bell Tube Physical characters : Wall thickness: 0.5mm of Pt+Ir alloy Gold foil : 0.1 mm thick Cells : used for loading Outer case(Pt+10%Ir) Space for Ra+filler mixture Eyelet hole cells
  25. 25. Why Radium is not used now? •Spectrum has > 8 photon energies ranging from 0.047- 2.45 MeV : gives heterogeneous beam & non uniform dose distribution • Low specific activity : 1 Ci/gm : requiring large diameter needles • High gamma ray constant: requires more protection • High energy: High radiation shielding will be required • Rn 222 being the gaseous daughter product - threat of leaks from long bent needles • Storage & disposal of leaked sources a big problem •Costly Ra source
  26. 26. CESIUM 137: ( Cs137) • Recovered from fission products of U-235 made in Nuclear Reactor • T1/2 : 30 yrs 1.8 • Relatively cheaper, extraction simple, • Decay system : 137 Cs 55 137 Ba 56 + 0-1e + γ • No gaseous decay product, safer than Ra • γ ray energy = 0.662 MeV 5mm Active bead (1.1mm dia.) • β filtration – 0.5 mm stainless steel • Available in tubes, needles, pellets. • Replaced Ra in t/t of gynecologic cancers. • Exposure rate constant : 3.26 Rcm² /mCi-h Stainless steel Miniature cylindrical source
  27. 27. Manual afterloading system of Cs Spiral spring Source train consist of flexible stainless steel holder containing miniature source separated by spherical steel spacers 1.8 mm in diameter. Sources and spacers retained by a steel spring. Min.cyl.sources Spacer beads Screw thread Retaining spring Source train
  28. 28.  T1/2 =73.8 days  Decays through β emission and electron capture to 192Pt and 192Osmium  Decay scheme:  Emits γ rays of energies ranging from 0.136 to 0.613 MeV (avg. 0.380 MeV)  Emits β particles max energy 0.670 MeV  β filtration =0.1mm of platinum(Eliminated by stainless steel capsule)  HVT- 4.5mm of Lead (Pb)  Available in nylon strands or as platinum cladded wire. 192Ir 192 Pt+ 0-1e+ γ
  29. 29. •Seeds are 3mm long & 0.5 mm in dia. spaced with their centre 1cm apart. •Internal core of 30%Ir +70%Pt surrounded by 0.2 mm thick stainless wall Single Pin 192 Ir wire( coil form) Hair Pin Core diam: 0.1mm- 0.4mm Sheath thickness : 0.1mm-0.4mm Overall thickness: 0.3mm- 0.6mm
  30. 30.  Produced by neutron activation of stable isotope 59Co  Decay scheme: 6027Co  T1/2 = 5.26 yrs  Each disintegration produces 2 y rays of energy 1.33 & 1.17 MeV (avg energy 1.25 MeV)  β energy= 0.318 MeV ;  HVL in Lead = 11 mm  High specific activity , miniaturized source can be made and used in brachytherapy. 60 Ni+ 0 28 -1 e +y
  31. 31.  Modern techniques → Sources of higher Sp Activity → Decreased source size compatible with remote afterloading stepping source machines for HDR.  No need for frequent replacements  Cost effective  Low operating cost.
  32. 32. Ir-192 : A near ideal radioisotope Compatible with after loading techniques Ideal energy (0.3-0.4 MeV) – monoenergetic – more radiobiological effect Flexible & malleable – can be used in form of wires of any size Energy is low – thinner shields required for radiation safety β-energy is low – so lesser filtration required Product (Pt192) not radioactive Easily available , less costly x Limitation Short half life (73.8 days) so source has to be replaced every 3 months
  33. 33. RADIUM SUBSTITUTES Element Energy (MeV) Half life HVLLead (mm) Exposure rate Constant Rcm2mCi-1h-1 Source form Clinical application Cesium Cs-137 0.662 30yrs 5.5 3.26 Tubes & Needles LDR I/C & temporary implants Cobalt Co-60 1.25 avg 5.26 yrs 11 13.07 Encapsulated sphere HDR I/C Iridium Ir -192 0.397 avg 73.8 Days 2.5 4.69 Seeds in Nylon; Metal wires ; Encapsulated source on cable Gold Au-198 0.412 2.7 Days 2.5 2.38 Seeds or “Grains” Permanent implants
  34. 34. Radium applicators for surface and intracavitary applications, used by Danlos and later by Wickham.
  35. 35. Applicators Applicators used to insert intracavitary sources in the uterus and vagina included  Rubber catheters and ovoids developed by French researchers.  Metallic tandems and plaques designed in Sweden.  Thin rubber tandems and ovoids of the Manchester system.  Fletcher (1953) designed a preloadable colpostat, which Suit et al. (1963) modified and made after loading.
  36. 36. Types of Brachytherapy…… • Depending on source loading pattern: – Preloaded: Inserting needles/tubes containing radioactive material directly into the tumor – After loaded: First, the non-radioactive tubes inserted into tumor • Manual afterloading: Sources manipulated into applicator by means of forceps & hand-held tools • Remote after loading: consists of pneumatically or motor-driven source transport system
  37. 37. Stockholm Applicators
  38. 38. Paris System Applicators
  39. 39. Manchester System Applicators Intrauterine applicator : A thin rubber tube with a flange at the end, which is held by the spacer and packing Intravaginal applicator : Vaginal applicators are essentially modification of corks described by Regaud , in the Paris technique. Made of hard rubber, and bored along the axis to take 1 or more radium tubes of actual length 2.2 cm., active length 1.5 cm. The shape of the ovoid follows the distribution in three-dimensional space of the isodose curves round a radium tube of 1 -5 cm. active length Large ovoid : 3cm , Medium : 2.5 cm, Small : 2cm in shortest diameter The ovoid pairs are separated at 1cm by a rubber made “Spacer” Or Kept in contact by means of a “Washer”
  40. 40. Loose preloaded system with chances of slipping of ovoids and hence disturbed geometry and creation of cold and hot spots leading to high failure or increased morbidity.
  41. 41. Photographs of original preloadable Fletcher applicators Pair of cylindrical “small” ovoids (2 cm in diameter) with inter-locking handles. Plastic jackets of two thicknesses are added to made medium (‘2.5 cm in diameter) and large (3 cm in diameter) sizes. The applicators have the same diameter as the Manchester ovoids but not the shape of an isodose Fletcher et al. Radiology 60:77-84, 1953
  42. 42. •In 1960-Ulrich K Henschke first described Manual afterloading •In 1962-Walstram first described remote afterloading (Based on ALARA principle – As Low As Reasonably Achievable) •In 1964- First developed Remote afterloading device Curietron prototype (1965) Initial single channel remote Afterloading machine 1962 Cobalt Ralston 1970
  43. 43. Fletcher afterloading colpostats In 1958, Suit et al. developed the first afterloadable Fletcher colpostat In 1978, Delclos et al. improved design of the afterloadable Fletcher colpostats Fletcher Suit a. Fletcher-Suit rectangular-handle model b. Round-handle, lighter model. Delclos
  44. 44. Manual after loading source trains of 137Cs MDR Selectron machine
  45. 45. Modern HDR Brachytherapy Machine MicroSelectron (Nucletron) VariSource & GammaMed (Varian). HDR plus (IBt Bebig)
  46. 46. PDR Brachytherapy Series of short HDR treatments ( 10 minute pulse repeated at 1 hr intervals)replacing the Continuous LDR treatment lasting several days. Overall time remains same as LDR Source strength : 1 Ci ADVANTAGE: •Radiobiologically nearer to LDR •optimization possible •Nursing care possible without radiation hazards Nucletron PDR afterloader
  47. 47. Thank You