Brachytherapy Final

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  • 1.
    • DR. MANOJ KUMAR B
    • MODERATOR:PROF. S.C. SHARMA
    • DEPTT. OF RADIOTHERAPY AND ONCOLOGY
    • PGIMER,CHANDIGARH
    BRACHYTHERAPY PRINCIPLE AND METHODS
  • 2. BRACHYTHERAPY
    • Type of radiation treatment in which radioactive sources are arranged in such a fashion that radiation is delivered to the tumor at a short distance by interstitial, intracavitary or surface application.
  • 3. CLINICAL ADVANTAGES
    • High biological efficacy
    • Rapid dose fall-off
    • High tolerance
    • Tolerable acute intense reaction
    • Decreased risk of tumor population
    • High control rate
    • Better cosmesis
    • Minimal radiation morbidity
    • Day care procedure
  • 4. LIMITATIONS & DISADVANTAGES
    • Difficult for inaccessible regions
    • Limited for small tumors (T 1 _T 2 )
    • Invasive procedures, require GA
    • Higher dose inhomogeneity
    • Greater conformation –small errors in placement of sources lead to extreme changes from the intended dose distribution
    • Radioactive hazards (not now)
    • Costly
  • 5. SELECTION CRITERIA
    • Easily accessible lesions
    • Early stage diseases (Ideal implant ≤ 5 cm)
    • Well localized tumor to organ of origin
    • No nodal or distant metastases
    • No local infections or inflammation
    • Favorable histology- mod. diff. i.e. SCC
    • Non DM / HTN
    • Proliferative/ ulcerative lesions preferred
  • 6. INDICATIONS
    • RADICAL RADIATION
      • Skin malignancies- BCC, SCC
      • Head & neck cancers
      • Ca cx
      • Ca prostate
    • BOOST AFTER EXT.RT±CCT
      • Head & neck cancers
      • Ca Breast
      • Esophagus
      • Anal canal
  • 7. INDICATIONS...
    • PERIOPERTIVE
      • STS
      • Ca Breast
    • POSTOP
      • Ca Endometrium
      • Ca cx
      • Ca Breast
    • PALLIATIVE
      • Bronchogenic Ca
      • Biliary duct malignancy
      • Ca Esophagus
      • Recurrent tumors
    • BENIGN
      • Keloids / Pterygium
    • OTHERS
      • Endovascular/Rad. stent
  • 8. CLASSIFICATION Classification Schemes Positioning of Radionuclide Dose rate of irradiation Duration of irradiation Loading pattern
  • 9. CLASSIFICATION
    • SURGICAL APPROACH / POSITIONING
      • SOURCE IN TUMOR
        • INTERSTITIAL
        • INTRACAVITARY
        • INTRALUMINAL
        • ENDOVASCULAR
      • SOURCE IN CONTACT BUT SUPERFICIAL
        • SURFACE BRACHYTHERAPY/ MOULAGE
    • DURATION OF IRRADIATION
      • TEMPORARY-Cs 137 ,Ir 192
      • PERMANENT-I 125 ,Au 198
  • 10. DOSE RATE(ICRU 38)
    • LOW DOSE RATE (LDR)
      • 0.4-2 Gy/hr
      • Bed confinement
      • LDR A/L : Cs 137
    • MEDIUM DOSE RATE (MDR)
      • 2-12 Gy/hr
    • HIGH DOSE RATE (HDR)
      • > 12 Gy/hr
    • ULTRA LOW DOSE RATE
      • 0.01-0.3 Gy/hr
    • ROUGHLY
      • LDR – 10 Gy/day
      • MDR -10 Gy/hr
      • HDR – 10 Gy/min
  • 11. ADVANTAGES
    • LDR
    • HDR
    • Predictable clinical effects
    • Superior radiobiological role
    • Less morbidity, control is best
    • Well practised since long
    • Minimum intersession variability in dose distribution
    • SHORT T/T TIME
      • Geometry well maintained
      • Better patient compliance / comfort
      • Day care procedure
    • OPTIMIZATION
    • NO RADIATION HAZARDS
    • SMALL APPLICATOR
      • Less tissue trauma
      • Better packing
  • 12. MDR BRACHYTHERAPY
    • ADVANTAGES
      • Comparative shorter T/T time
      • One time treatment can be used
      • Patient convenience
      • Radio biologically acceptable nearer to LDR Brachytherapy
    • DISADVANTAGES
      • Late complications increases if correction not done
  • 13. SOURCE LOADING TECHNIQUE
    • PRELOADING SYSTEM
      • Live sources
      • ADVANTAGES
        • Clinical results are best
        • Affordable
        • Long term results with lesser morbidities
      • DISADVANTAGES
        • Radiation hazards
        • Special instruments
        • Difficult application / hasty
        • Geometry not maintained
        • ? Optimization
  • 14. AFTER LOADING TECHNIQUE
    • MANUAL
      • Avoids radiation protection issue of preloading
      • Better applicator placement
      • Verification prior to source placement
      • Min. radiation hazard
      • Advantages of preloading
    • REMOTE CONTROLLED
      • No radiation hazard
      • Accurate placement
      • Geometry maintained
      • Better dose distribution
      • Highly precise
      • Short T/T time
      • Day care procedure
      • Mainly used for HDR
  • 15. INTERSTITIAL BRACHYTHERAPY
    • Sealed Radioactive sources directly implanted into the tumor in a geometric fashion
    • First suggested by Alexander Graham Bell
    • ADVANTAGES
      • Higher local dose in shorter time
      • Rapid dose fall
      • Better tumor control
      • Lesser radiation morbidities
      • Superior cosmetics
      • Functional preservation of organs
  • 16. INTERSTITIAL BRACHYTHERAPY…
    • DISADVANTAGES
      • Radiation hazards in older days
      • Costly
      • Not applicable to inaccessible areas
    • INTENTION OF TREATMENT
      • Always RADICAL
        • As radical brachytherapy alone (smaller lesions)
        • Local boost in combination with EBRT (larger lesion)
        • NEVER USED FOR PALLIATION
  • 17. SELECTION CRITERIA
    • Easily accessible lesions, at least from one side
    • Early stage disease
      • T 1 -T 2 and sometimes early T 3
      • Ideally total size of implant ≤ 5 cm
    • Non DM /HTN
    • No local infection
    • Proliferative and ulcerative lesions preferred
  • 18. CLINICAL APPLICATIONS
    • Head & neck tumors
      • Early stage oropharyngeal cancers
    • Ca breast- Boost /PBI
    • Ca prostate
    • Soft tissue sarcoma
    • Gynecologic malignancies
    • Ca anal canal and rectum
    • Ca lung and pancreas
  • 19. TYPES OF INTERSTITIAL IMPLANTS ACCORDING TO SIZE/LOCATION/PROXIMITY OF TUMOR TO NORMAL STRUCTURES
    • TEMPORARY
      • Radioactive sources removed after desirable dose has been delivered
      • Rigid stainless steel needles/flexible Teflon / nylon guides/plastic tubes
      • Preloaded/After loaded
    • PERMANENT
      • Preloaded – rigid needle eg. Ra 226 ,Cs 137
      • After loaded – Manual/ Remote
      • Advantages
        • Flexibility of implant design
        • Reduction of radiation exposure levels resulting in more accurate placement of needles and guides
  • 20. SYSTEMS OF IMPLANT DOSIMETRY
    • OBJECTIVES OF TREATMENT PLANNING
      • To determine the distribution & type of radiation sources to provide optimum dose distribution
      • To provide complete dose distribution in irradiated volume
    • SYSTEM USED
      • Paterson-Parker (Manchester) system
      • Quimby system (Memorial) system
      • Paris system – Pierquin, Chassagne , Dutreix and Marinello
      • Computer System
  • 21. SYSTEMS OF IMPLANT DOSIMETRY
    • These system designed during times when computers were not available for routine planning
    • Extensive table & elaborate rules of source distribution were devised to facilitate the process of manual treatment planning
    • These systems differ in rule of implantation, definition of dose uniformity & method used in reference dose specification
  • 22. RULES OF INT.IMPLANT SYSTEM PARAMETERS MANCHESTER QUIMBY PARIS COMPUTER Linear strength Variable Constant Constant Constant Source distribution Planar implant:(periphery) Area <25 cm- 2/3 Ra; 25-100 cm- ½ Ra; >100 cm- 1/3 Volume implant::Cylinder:belt-4 parts,core-2,end-1 Sphere:shell-6,core-2 Cube :each side-1,core-2 Uniform Uniform Uniform Line sources parallel planes Uniform Line sources Parallel or cylinderic volumes Spacing line source Constant approx. 1 cm apart from each other or from crossing ends Same as Manchester Constant, Selective Separation 8-15 mm Constant Selective Crossing needles Required to enhance dose at implant ends Same Crossing needles not used;active length 30-40% longer Crossing needles not used;active length 30-40% longer
  • 23. COMPONENTS-CLASSICAL SYSTEM
    • DISTRIBUTION RULES : given a target volume, distribution rules determine how to distribute RA sources & applicators in & around target volume
    • DOSE SPECIFICATION & IMPLANT OPTIMIZATION CRITERIA : Each system has a definition of prescribed dose
    • Above 2 criteria determine dose homogeneity, normal tissue sparing, no. of catheters implanted & margins around target
    • DOSE CALCULATION AIDS : Older systems used tables that give dose delivered per mg Ra-Eq-hr as a function of treatment volume or area
      • Recent Paris system uses computerized treatment planning to relate absorbed dose to source strength & treatment time
  • 24. PRINCIPLE-MANCHESTER SYSTEM FEATURES DOSE & DOSE RATE 6000-8000 R in 6-8 days (1000 R/day; 40 R/hr) UNIT / USE OF RADIUM mg Ra hr – defined as amount of radium to give specified dose in 1 hr DOSE SPECIFICATION CRITERA Effective minimum dose 10% above absolute minimum dose LINEAR ACTIVITY Variable: 0.66 and 0.33 mg RaEq/cm
  • 25. QUIMBY SYSTEM
    • Developed by Edith Quimby et al
    • Dose 5000-6000 R in 3-4 days
    • Equal linear intensity (mg RaEq/cm) needles distributed uniformly (fixed spacing) in each implant, although spacing selected in 1-2 cm range acc. to implant size
    • Quimby tables (Nomogram ) give mg RaEq-hr to deliver stated exposure of 1000 R as function of T.V. or area (5000-6000 R over 3-4 days; 60-70 R/hour)
    • No clear description of rules for distributing Ra needles
    • Crossing recommended; peripheral needles placed on or beyond T.V. boundaries
    • Dose specification criteria inconsistent
    • NOT RECOMMENDED FOR CLINICAL USE
  • 26. PARIS SYSTEM- PRINCIPLES
    • RADIOACTVE SOURCES
    • Rectilinear/parallel -arrangement so that centers are located in the same plane which is perpendicular to the direction of sources- CENTRAL PLANE
    • Equidistant
    • Linear activity-uniform and identical
    • Source geometries
      • Linear- single-plane implants
      • Squares/Equilateral triangles- two plane implants
  • 27. PARIS SYSTEM FEATURES DOSE AND DOSE RATE 6000 -7000 cGy in 3-11 days DOSE PRESCRIPTION POINT Average of the minimum doses in the region defined by the source REFERENCE DOSE & DOSE GRADIENT 85 % of the BASAL DOSE 15 % between the Reference dose and the Basal dose RA SOURCE PLACEMENT Reference isodose volume covers the treated volume
  • 28. PERMANENT IMPLANTS
    • ADVANTAGES
    • DISADVANTAGES
      • Less accessible sites
      • Cont. ultra low dose rate>Max biological effectiveness
      • Better tissue heal
      • Better effect in slow and radio resistant tumors
      • Improved mobility
      • Environmental issue
      • Dosimetric uncertainties > Later part of T/T becomes less effective
      • Source displacement
      • Large tumor > Difficult procedure and geometry
      • Radio biologically less effective for rapidly proliferating tumors
  • 29. COMPUTER SYSTEM
    • Implant system evolved through use of computers
    • Implantation rules: Sources of uniform strength
    • Spaced uniformly (1-1.5 cm), larger spacing for larger implants to cover entire T.V.
    • Active length 30-40% longer than Target length as ends uncrossed
    • T.V.: sufficient safety margins; peripheral sources implanted on outer surface
    • Dose specified by isodose surface that surrounds target
    • Whole planning with help of computers
  • 30. COMPUTER DOSIMETRY
    • Possible to preplan implants & complete isodose distribution corresponding to final source distribution
    • Rapid & fast; helps modify implant
    • Isodose patterns can be magnified & superimposed on implant radiograph
    • Localization of sources:
      • Orthogonal Imaging method
      • Stereo-shift method
      • CT
    • Dose Calculation:
      • No. of milligrams or millicurie in implant
      • Location of each source with respect to dose calculation point
      • Type of isotope being used
      • Filtration of the encapsulation
  • 31. COMPUTER DOSIMTERY
    • Dose Computation:
      • Dose calculation Formalisms’ (AAPM TG 43 algorithm)
        • Use Sievert Integral directly
        • Precalculated dose tables
          • For Radium & other long lived sources: Dose rates in form of isodose curves
          • For Iridium & relatively short lived implants: Computer calculates cumulative dose with decay correction
  • 32. CLINICAL APPLICATIONS
    • Oral Cavity:
    • LIP:
      • Indications: T1-2N0 Lesions
      • T.V.: All visible & palpable tumour with 5-10 mm margin
      • Dose: 50-70Gy in 5-7 days LDR
      • Technique:
        • Rigid afterloading needles maintained in place by Template
        • Classical plastic tubes
      • Spacers to decrease dose to gingiva, teeth & other lip
  • 33. CLINICAL APPLICATIONS…
    • Buccal Mucosa:
      • Indications:
        • Brachytherapy alone indicated for small (<4cm), well-defined lesions in anterior 2/3 rd
        • As boost after EBRT for larger lesions
      • T.V.: GTV + margins
      • Dose: Alone 65-70 Gy
          • Boost 25-30 Gy
      • Technique: Guide Gutter Technique: Lesion < 2cm
      • Plastic tube technique : For other lesions
  • 34. CLINICAL APPLICATIONS…
    • Oral Tongue:
    • Indications: T1 N0, T2 N0 < 3cm lesion
    • T.V.: GTV + 5 mm margin
    • Dose: Alone:60-65 Gy LDR
        • Boost 20-25 Gy after EBRT dose of 45-50 Gy
    • Techniques: Guide-gutter technique
    AP X-ray
  • 35. CLINICAL APPLICATIONS…
    • Floor of Mouth :
      • Indications: T1-2N0 lesions, ≥ 5 mm away from mandible
      • Dose: Techniques same as for Tongue implants
      • Complication: Osteoradionecrosis:5-15%
    • Oropharynx:
      • Indications: Ca BOT , soft palate, tonsillar fossa & vallecula usually as boost after EBRT
        • Lesions < 5 cm (after EBRT)
      • T.V.: GTV + 10 mm margin
      • Dose: Tonsillar fossa-25-30 Gy; BOT 30-35 Gy
      • Technique: Classical Plastic Loop technique
  • 36. CLINICAL APPLICATIONS…
    • Breast
      • Indications: Boost after BCS & EBRT
            • Postoperative interstitial irradiation alone of
            • the primary tumor site after BCS in selected
            • low risk T1 and small T2N0 (PBI)
            • Chest wall recurrences
    Moderator: Prof. S. C. Sharma As sole modality As Boost to EBRT
    • Patient choice: cannot come for 5-6 wks treatment :
        • Distance
        • Lack of time
    Close, positive or unknown margins Elderly, frail, poor health patient EIC Large breasts: unacceptable toxicity Younger patients Deep tumour in large breast Irregularly thick target vol.
  • 37. CLINICAL APPLICATIONS…
    • T.V.: Primary Tumor site + 2-3 cm margin
    • Dose: As Boost: 10-20 Gy LDR
        • AS PBI: 45-50 Gy in 4-5 days LDR (30-70 cGy/hour)
            • 34 Gy/10#, 2# per day HDR
    • Technique:
      • Localization of PTV: Surgical clips (at least 6)
        • USG, CT or MRI localization, Intraop USG
      • During primary surgery
      • Guide needle technique or
      • Plastic tube technique using Template
        • Double plane implant
        • Skin to source distance: Minimum 5 mm
  • 38. CLINICAL APPLICATIONS…
  • 39. CLINICAL APPLICATIONS…
    • Prostate:
    • Indications
      • Brachytherapy as monotherapy:
        • Stage T1-2a & Gleason score 2-6 & PSA ≤ 10 ng/ml
      • As boost after EBRT
        • Stage T2b, T2c or Gleason score 7-10 or PSA > 10 ng/ml
      • For brachytherapy, Prostate size < 50 cc
    • Exclusion criteria:
      • Life expectancy < 5 yrs
      • Large or poorly healed TURP defect
      • Distant Mets or operative risk
    • T.V.: Whole prostate within capsule + 2-3 mm margin
    • Methods: Permanent Implant (I 125 or Pd 103 ) or
    • Temporary Implant (Ir 192 )
  • 40. CLINICAL APPLICATIONS…
    • Technique for Permanent implant
    • Retropubic approach with I 125 seeds- Disappointing results
    • Modern technique: Transperineal Approach
      • TRUS guided
      • Two step approach
        • Volume study of prostate
      • Computer planning
        • Seed positioning
    • Coverage check -USG & Flouroscopy
    • Check Cystoscopy
    • Post-implant image based dosimetry
  • 41. CLINICAL APPLICATIONS
    • Dose:
      • I 125 : 145 Gy as sole RT
          • 100-110 Gy as boost to 40-50 Gy EBRT
      • Pd 103 : 125 Gy as sole RT
          • 90-100 Gy as boost to 40-50 Gy EBRT
    • Temporary Implants with Ir 192 (LDR or HDR):
      • Procedure same as above; lesser no. of plastic catheters required (8-15)
      • Dose:
        • LDR 30-35 Gy seeds left for 3 days(Boost to 45 Gy EBRT)
        • HDR 20-25 Gy, 4-6 Gy/#(Boost to 45 Gy EBRT)
  • 42. CLINICAL APPLICATIONS
    • Soft tissue Sarcomas (using Ir 192 or I 125 )
    • Indications:
      • As sole postop RT:
        • completely resected intermediate or high grade tumours of extremity or superficial trunk with -ve margins
      • As boost to postop EBRT:
        • Intermediate or high grade sarcoma with +/- margins
        • Postop pts with small lesions & +ve/uncertain margins
        • Deep lesions
        • Low grade sarcomas
    • T.V.: GTV + 2-5 cm margin
        • GTV based on preop MRI & clinical findings
    • Dose: LDR (Ir seeds or wires) as sole treatment 45-50 Gy in 4-6 days
        • As boost to 45-50 Gy EBRT: 15-25 Gy in 2-3 days
  • 43. CLINICAL APPLICATIONS…
    • Technique:
      • Usually performed at time of surgery
      • Basic or sealed end temporary implant technique
  • 44.
    • Brain: Permanent or temporary (using I 125 or Ir 192 seeds/wires )
    • Indications:
      • As boost to EBRT or recurrence
      • Anaplastic astrocytoma or GBM, unifocal, well cicumscribed, peripheral lesions & < 5 cm in diameter
    • T.V.: Contrast enhancing area on MRI +/- 5mm margin
    • Dose: LDR 50-60 Gy, 0.4-0.5 Gy/hr
    • Technique: Planning CT/MRI done
    CLINICAL APPLICATIONS…
  • 45. CLINICAL APPLICATIONS…
    • Ca Anorectum
    • Indications: As boost to EBRT/ChemoRT
          • If T.V. doesnot exceeds 1/2 circumference, 5 mm thick, 5 cm long i.e. T1-2 & small T3 lesions
          • T1N0 adenocarcinoma of rectum 3-10 cm above anus
    • T.V.: Visible palpable tumor+5 mm
    • Dose: LDR 15-20 Gy at 0.3-0.6 Gy/hr
    • Technique: Guide needle technique with template
  • 46. CLINICAL APPLICATIONS…
    • Gynecological Tumors ( Ir 192 LDR or HDR)
    • Indications:
      • Ca Cervix
      • Ca Endometrium
        • Postop local recurrence
      • Ca Vagina & Vulva
        • Radical BT in select early lesions (T1-2N0)
        • Boost after EBRT in large lesions (T2-3N1)
    • Technique:
      • Guide-gutter technique
      • Blind plastic tube implant
      • (transperineal technique)
      • Plastic or guide needles
  • 47. CLINICAL APPLICATION – CA CX
        • ABS Recommendations
        • Bulky primary disease
        • Prior hysterectomy-inability to place tandem
        • Post hysterectomy
          • vault recc./cut-through hysterectomy/cervical stump presentation
        • Extesive parametrial involvement
        • Distorted anatomy
          • Narrow vagina & fornices
          • Extensive / Distal vaginal wall involvement
        • Re-irradiation after recurrences
        • Prior course of RT to area of interest
  • 48. CLINICAL APPLICATIONS…
      • PERINEAL IMPLANTS
    Martinez Universal Perineal Interstitial Template (MUPIT ) Syed-Neblett template
  • 49. CLINICAL APPLICATIONS…
    • Dose:
      • Radical BT:
        • LDR: 55-60 Gy @ 50-90 cGy/hr
        • HDR: 3.5 Gy/#@ 2#/day/12-16#
      • Boost
        • LDR: 15-25 Gy , 50-90 cGy/hr
        • HDR: as above, no. of # depend upon EBRT doses
  • 50. CLINICAL APPLICATIONS…
    • Other sites:
      • Lung: Permanent perioperative BT, I 125 seeds, Au 198 Grains
          • Persistent or recurrent ds after EBRT or residual ds after surgery
      • Pancreas: Permanent perioperative BT, I 125 seeds
          • Locally advanced unresectable ds
      • Penis & Urethra:
  • 51. INTRACAVITARY APPLICATION
    • Radioactive sources are placed in a existing cavity usually inside a predefined applicator with special geometry
    • Uses:
      • Cervix
      • Endometrium
      • Vagina
      • Maxilla
      • Nasopharynx
  • 52. PARIS SYSTEM
    • Single application of radium
    • Two cork colpostats (cylinder) and an intrauterine tube
    • Delivers a dose of 7000- 8000 mg-hrs of radium over a period of five days(45R/hr) (5500mg/hr
    • Equal amount of radium used in the uterus and the vagina
    • Intrauterine sources
      • 3 radioactive sources, with source strengths in the ratio of 1:1:0.5
    • colpostats
      • sources with the same strength as the topmost uterine source
  • 53. STOCKHOLM SYSTEM
    • Fractionated course of radiation delivered over a period of one month.
    • Usually 2-3 applications, each for a period of 20- 30 hours (repeated 3weekly)
    • Intravaginal boxes -lead or gold intrauterine tube -flexible rubber
    • Unequal loading
      • 30 - 90 mg of radium in uterus
      • 60 - 80 mg in vagina
    • Total prescribed dose -6500-7100 mg Ra
      • 4500 mg Ra contributed by the vaginal box (dose rate-110R/hr or 2500mg/hr/#)
  • 54. DRAWBACKS OF PARIS AND STOCKHOLM SYSTEMS
    • Long treatment time
    • Discomfort to the patient
    • No dose prescription
  • 55. MANCHESTER SYSTEM
    • To define the treatment in terms of dose to a point. Criteria of the point:
      • Anatomically comparable
      • Position
        • where the dosage is not highly sensitive to small alteration in applicator position
        • Allows correlation of the dose levels with the clinical effects
    • To design a set of applicators and their loading which would give the same dose rate irrespective of the combination of applicators used
    • To formulate a set of rules regarding the activity, relationship and positioning of the radium sources in the uterine tumors and the vaginal ovoids, for the desired dose rate
  • 56. POINT A
    • PARACERVICAL TRIANGLE where initial lesion of radiation necrosis occurs
    • Area in the medial edge of broad ligament where the uterine vessel cross over the ureter
    • The point A -fixed point 2cm lateral to the center of uterine canal and 2 cm from the mucosa of the lateral fornix
    • POINT B
    • Rate of dose fall-off laterally
    • Imp. Calculating total dose-Combined with EBRT
    • Proximity to important OBTURATOR LNs
    • Same level as point A but 5 cm from midline
    • Dose ~20-25 % of the dose at point A
  • 57.  
  • 58. LOADING OF APPLICATORS
    • In order that point A receives same dosage rate no matter which ovoid combination is used ,it is necessary to have different radium loading for each applicator size
    • Dose rate 57.5 R/hr to point A
    • Not more than 1/3 dose to point A must be delivered from vaginal radium
    • APPLICATORS
  • 59. LOADING PATTERN TUBE TYPE LENGTH TUBES RADIUM (mg) UNITS (FUNDUS to CX) LOADING TUBES (mg) LARGE 6 3 35 6-4-4 15-10-10 MEDIUM 4 2 25 6-4 15-10 SMALL 2 1 20 8 20 VAGINAL OVOIDS TUBES RADIUM (mg) UNITS LOADING TUBES(mg) LARGE 3 22.5 9 10-10-5 or 20/25 MEDIUM 2 20 8 20 SMALL 1 17.5 7 10-5-5 or 20/15
  • 60. GUIDELINES
    • Largest possible ovoid
      • Lesser dose to mucosa
    • Longest possible tandem (not > 6 cm)
      • Better lateral throwoff
      • Smaller dose to mucosa
    • Dose to point A- 8000R
    • Dose to uterus wall -30,000R
    • Dose to vaginal mucosa-20,000R
    • Dose to recto-vaginal septum- 6750 R
    • Dose limitation
      • BLADDER <80 Gy
      • RECTUM <75 Gy
  • 61. INTRACAVITARY APPLICATORS
    • MANCHESTER
    • PGI
  • 62. IDEAL APPLICATION
    • Tandem
      • 1/3 of the way between S1 –S2 and the symphysis pubis
      • Midway between the bladder and S1 -S2
      • Bisect the ovoids
    • Marker seeds should be placed in the cervix
    • Ovoids
      • against the cervix (marker seeds)
      • Largest
      • Separated by 0.5-1.0 mm
      • Axis of the tandem-central
    • Bladder and rectum - should be packed away from the implant
  • 63. ICRU REPORT NO.38
    • DOSIMETRIC INFORMATION FOR REPORTING
    • Complete description
      • Technique
      • Time-dose pattern
    • Treatment prescription
    • Total Reference Air Kerma
    • Dose description
      • Prescription points/surface
      • Reference dose in central plane
      • Mean central /peripheral dose
    • Volumes: Treated/ point A/ reference volume
    • Dose to Organs at Risk : bladder, rectum
  • 64.
    • REFERENCE VOLUME
      • Dimensions of the volume included in the corresponding isodose
      • The recommended dose 60 Gy
    • TREATED VOLUME
      • Pear and Banana shape
      • Received the dose appropriate to achieve the purpose of the treatment, e.g., tumor eradication or palliation, within the limits of acceptable complications
    • IRRADIATED VOLUME
      • Volumes surrounding the Treated Volume
      • Encompassed by a lower isodose to be specified, e.g., 90 – 50% of the dose defining the Treated Volume
      • Reporting irradiated volumes may be useful for interpretation of side effects outside
  • 65. CERVICAL BRACHYTHERAPY
  • 66. ABS.DOSE AT REFERENCE POINTS
    • BLADDER POINT
    • RECTAL POINT
    • LYMPHATIC TRAPEZOID OF FLETCHER
      • LOW PA, LOW COMM.ILIAC LN & MID EXT ILIAC LNs
    • PELVIC WALL POINTS
      • DISTAL PART OF PARAMETRIUM & OBTURATOR LNs
  • 67. DOSE SCHEDULE
    • LDR (<200cgy/hr)
      • 35-40 Gy at point A
    • MDR (200-1200cgy/hr)
      • 35 Gy LDR EQUIVALENT at point A
    • HDR(>1200cgy/hr)
      • 9 Gy in 2 #
      • 6.8Gy in 3# at point A
  • 68. EXTERNAL RT WITH BRACHYTHERAPY
    • Brachytherapy can follow external irradiation
      • SIMULTANEOUS
        • Stage I - II with very minimal parametriun involvement
        • HDR -5 sessions (9gy /#/ 5, 1week apart)
        • 40 Gy by XRT simultaneously
      • SANDWICH
        • Stage I-II
        • MDR 40 Gy LDR eq.—› XRT 40 Gy —› MDR 35 Gy LDR eq.
    • In both above cases a MIDLINE SHIELD is used
  • 69. POST OP/ VAULT BRACHYTHERAPY
    • Vault RT
      • No residual disease
        • 8500 cGy at 5mm from the surface of the vault
        • 2 sessions 1 week apart
      • Residual disease
        • CTV of 2 cm given to gross tumor and the prescription of 8500cgy encompassing the whole CTV is made
        • 2 sessions 1 week apart
    • Mostly after XRT
  • 70. POST OP BRACHYTHERAPY
    • CONTRAINDICATIONS
      • Vaginal wall involvement ( middle- lower 13)
      • Heavy parametrium infiltration
      • VVF or VRF
      • Inadequate space
      • Medical contraindications
      • Metastatic disease
    • Supplementary radiation 2000 cGy 10# 2 weeks
  • 71. SURFACE MOULDS
    • Radiation is delivered by arranging RA sources over the surface of tumor
    • Types
      • Planar
        • Circular
        • Square
        • Rectangular
      • Line source
      • Cylinder
  • 72. INDICATIONS
    • Superficial /Accessible tumors
    • Skin ca
    • Post mastectomy recurrence
    • Oral tumor
      • hard palate ,alveolus
    • Penile carcinoma
  • 73. CIRCULAR MOULDS
    • Amount of radium used is obtained from the table for a particular treating distance
    • Circular arrangement is the best
    • Space between the needles (end) should not be more than H
  • 74. SQUARE MOULDS
    • An arrangement is considered to be linear if the distance between the active end of the sources does not exceed the height
    • Length of the side of the square is less than twice the height
      • No further radium is placed in the center
  • 75. RECTANGULAR MOULDS
    • The dividing lines or bars are placed parallel to the longer side
    • Elongation correction factor: Increase the reading in milligrams hour by a given factor
      • This factor is proportional to the ratio of the sides of the rectangle
        • 1.5:1 = 2.5%
        • 2:1 = 5%
        • 3:1 = 9%
        • 4:1 = 12%
  • 76. CIRCULAR MOULDS
    • CURVED SURFACES
    • COAXIAL RINGS
    • Irregular area
    • Curved surfaces: convex, concave
      • The smaller area is used for calculation of radium dose and implant rules
    • Cylinder mould: Amount of radium is 30D 2
    • DISTRIBUION RULES
      • In case of coaxial rings radium is placed at a distance equal to 2H
  • 77. INTRALUMINAL BRACHYTHERAPY
    • Radioactive source is passed through a tube and passed into a hollow lumen
    • Sites
      • Esophagus
      • Bronchus : Bronchogenic carcinoma
        • Definitive : T 1 -T 2 tumors
        • Palliative
          • Dyspnea
          • Cough
          • Atelectasis
      • Biliary tract
  • 78. RADIOBIOLOGY
    • Biological effects depend on
      • Dose prescribed
      • Treated volume
      • Dose rate
      • Fractionation
      • Treatment duration
    • Heterogeneous dose distribution
    • Higher average dose
    • Short treatment
  • 79. RADIOBIOLOGY – 4 Rs
    • Repair
    • Reassortment / redistribution
    • Repopulation
    • Reoxygenation
  • 80. RADIOBIOLOGY- LDR
    • Repair of Sublethal damage
    • Most significant- 1 Gy/min and 0.3 Gy /h
    • DNA repair
      • Dynamic process
      • Special kinetics
    • Simple exponential kinetics
    • Reassortment - slow and imp. <1 Gy/min
    • Repopulation-slowest and significant
    • Reoxygenation - relative slow process may be a disadvantage
  • 81. LDR AND HDR
    • LDR vs HDR
    • EFFECTS OF HDR
  • 82. RADIOACTIVE SOURCES
    • Naturally occurring
    • Artificial
    • Induced by neutron bombardment
    • Induced by bombardment of protons
    • Fission product
    • CHARACTERISTICS
      • HALF LIFE
      • GAMMA ENERGY
      • BETA ENERGY
      • HALF VALUE LAYER
      • EXPOSURE RATE CONSTANT
      • BETA FILTRATION
      • DECAY SCHEME
  • 83. IDEAL RADIONUCLIDE
    • Photon energy :low to medium- 0.03 to 0.5 MeV
      • Monoenergetic beam preferred
    • Moderate Gamma ray constant
    • Long half life
    • High specific activity
    • Isotropic
    • No gaseous disintegration/daughter product
    • Nuclei should not disperse if source damaged
    • Low beta energy
    • Low or no self attenuation
    • Insoluble and nontoxic
    • Flexible
    • Easily available and cost effective
    • Withstand sterilization process
    • Disposable without radiation hazards to environment
  • 84. RADIUM 226
    • Sixth member of the radio active series which starts with uranium and ends with lead
    • Half life 1620 years
    • Gamma energy 0.83 MeV
    • Half value 12mm Pb
    • Exposure rate constant 8.25 Rcm 2 /mCi-h
    • Filtration 0.5 – 1 mm Pt
  • 85. RADIUM SUBSTITUTES NAME ORIGIN T 1/2 γ ENERGY-MeV β ENERGY β FILTRATION HVL (Pb -mm) ERC SPECI. ACTI. DECAY PRODUCT Rn 222 NATURAL 3.83 days 0.83 Stainless steel 12 10.27 Pb 206 Cs 137 FISSION 30.17 yrs 0.662 0.512 1.17 - do - 6.5 3.26 87 Ba 137 Co 60 NEUTRON ACTIVAT. 5.26 yrs 1.17, 1.33 0.38 - do- 11 13.07 1020 Ni 60 Ir 192 - do - 73.8 yrs 0.136- 1.06 0.079-0.068 Platinum 4 4.69 7760 Pt 192 Tn 182 - do - 115 yrs 0.67 - Platinum 12 6.87 - - Au 198 - do - 2.7 days 1.088- 0.412 0.96 St. steel 3.3 2.376 - Hg 198 I 125 - do - 59.4 days 0.274, 0.314 No Titanium 0.01 10th 1.403 - Te 125 Pd 103 - do - 16.97 days 0.21 No Platinum 0.03 6.87 - Ru 103
  • 86. Thank You