Applicators for Brachytherapy in Ca cervix.pptx

Bracchytherapy Principles of ICA, ISBT

1. Brachytherapy: APPLICATORS & PRINCIPLES OF TREATMENT IN CA CERVIX Presenter – Dr Chandrima Mukherjee Moderator – Dr Rahul Sisodiya Faculty Moderator – Dr Abhishek Shinghal

2. Contents Brachytherapy Sources History & Systems of Brachytherapy Principles of Gyn Brachy Procedure of BT Applicators – Evolution, Types, Application in various Clinical settings 2

3. Brachytherapy sources Brachytherapy is a method by which radiation treatment is delivered with the help of sealed radionuclide which is kept close to the target tissue. 3 Element Half Life Energy ( Mev) Exposure Rate Constant ( mCi /h) Radium (Ra 226 ) 1626 years 0.83 8.25 Cesium (Cs 137 ) 30 years 0.662 3.28 Iridium (Ir 192) 73.8 day 0.38 4.69 Cobalt (Co60) 5.26 years 1.25 13.07 Iodine (I 125) 60 days 0.028 1.45 Palladium (Pd 103) 17 days 0.021 1.48 Gold (Au 198) 2.7 days 0.412 2.35

4. History of Brachy therapy

5. Need for systems: T o implement prescription in reproducible manner and as a common language for Prescribing, Reporting & Recording/Audit “The term system denotes a set of rules which takes into account  the  source types and strengths, geometry and the method of application  to obtain  suitable dose distributions   across the volume to be treated” -ICRU: International Commission on Radiation Units and Measurement , Report 38 Systems of intracavitary Brachytherapy

6. Stockholm System Work of Forsell at Radium H emmet 1910 This system used: Intravaginal boxes made up of silver or gold The intrauterine tube made up of flexible rubber ( These were not fixed together ) Unequal amounts of radium used Uterus – 30-90 mg in rubber tube Vagina – 60-80 mg in shielded lead/silver boxes Fractionated (2-3#) course Separated by 1-3wks. Total prescribed dose: 6500 –7100 mg hrs f or a period of 20-30 hours each Dose Rate: 110 R/hr or 2500 mg/hr/# Limited use of EBRT

7. 7 Regaud , 1919, Institute of Radium, Paris • Single application of Radium for 120 hrs (5-6days) • Designed to deliver a dose of 7000-8000mg/hrs over a period of 5 days (45 R/hr) (5500 mg/hr) • In this system , almost an equal amount of Radium was used in the uterus and the vagina. • The system in corporated • Two cork colpostats (cylinder) with 13.3mg Radium each • An intrauterine tube of rubber with 33.3mg Radium ( in the ratio of 1:1:0.5 i.e. 13.3 mg, 13.3 mg & 6.6 mg respectively) Fixed mg- hrs for a specified tumor volume. Combined with EBRT Paris system

8. Manchester system INTRA-UTERINE TUBE The intrauterine tube was made up of the rubber These tubes were available in three separate lengths: 2cm, 4cm & 6cm Length = 2.2 cm (Active length – 1-1.5 cm) The I.U.tubes were closed at one end, and had a flange at the other end so that when packed into position, the uterine tube did not slip out during the treatment. OVOIDS Used in pairs, one in each lateral fornix. The shape of ovoids mimic the shape of isodose curves around a Radium tube having “active length” of 1.5cm. The ovoids were designed to be adaptable to different vaginal capacities, with diameter of 3 sizes. Small dia = 2 cm = 17.5 mg Medium dia = 2.5 cm = 20 mg Large dia = 3 cm = 22.5 mg Preloaded ovoids containted no shielding & extensive packing was needed to spare OARs Originated from the Paris system. Consists of a pair of ovoids & an intra uterine tube Dose specified at fixed points – point A Specified therapy in terms of absorbed dose – Roentgen instead of mg hrs. SPACERS/ WASHERS •To maintain the distance between the ovoids •To help in their fixation •Pairs of ovoids held apart by a “SPACER” rubber. •Fixed at a distance of 1 cm. •Spacer was used to give the largest possible separation b/w the ovoids so that the dose could be carried out as far laterally as possible.

9. The pointA should receive the same dose rate , irrespective of the combination of applicators used. Not more t han one third of the total dose to point A should be delivered by any single vaginal ovoid. ( So that tolerance of vagina mucosa is not exceeded) Standard or ideal loading is 60-40 i.e. 60 % of the dose to point A is contributed by intrauterine sources while 40% is contributed by ovoids . Total Dose to point A : 8000R Total number of applications:2 Total time for each application:72hrs Totaltime:144hrs with 4–7 days gap between each treatment Dose – rate desired : 55.5R/hour to pointA Amount of radium to be used was defined in terms of units. 1 unit = 2.5 mg of radium filtered by 1 mm platinum. The loadings were specified in terms of integral multiples of this unit. 9

10. POINT A Todd & Meredith defined a point in paracervical triangle where the uterine vessels cross the ureter as pointA . • Point A, lies in the paracervical triangle. • Point A is defined as a point 2 cm. lateral to the center of the uterine canal and 2 cm. superior to the mucosa of the lateral fornix, in the plane of the uterus. 10

11. Point B To know the rate of fall of dose external to point A, as an index to the volume of tissue treated. • Initially thought to quantify the dose delivered to the obturator lymph nodes. • Def: 5cm from the patient’s midline, at the same level as point A. • Dose to Pt B, depends little on the geometric distribution of the sources, but on the total amount of radium used. 11

12. Icru 38 12

13. RECTAL POINT : The dose is calculated at a point 5 mm posterior to (opacified) vaginal cavity along an AP line midway between vaginal sources. On the frontal radiograph, this reference point is taken at the intersection of (the lower end of) the intrauterine source through the plane of the vaginal sources 13

14. Why did we move away from point a?? Point A & Point B are not anatomical sites. It is dependent on the applicator geometry Inter-fraction variation may exist

15. IMAGE BASED BT GTV- includes macroscopic tumour extension at time of BT as detected by clinical examination and as visualised on MRI: High signal intensity mass(es) (FSE, T2) in cervix/- corpus, parametria, vagina, bladder and rectum. HRCTV – includes GTVB1, B2, . , always the whole cervix and the presumed extracervical tumour extension at time of BT. IRCTV – encompasses high risk CTV1 with a safety margin of 5– 15 mm. ( include GTV at Diagnosis) 15 1 st Guidelines – Haie Meder et al – GEC ESTRO CONSORTIUM – 2005

16. Icru 89 Residual GTV (GTV-Tres): The GTV-Tres represents the residual GTV at the time of brachytherapy, assessed clinically and/or by imaging. (high-signal intensity mass using FSE T2-w MR ) High-Risk CTV: CTV-T HR consists of the whole cervix , the GTV-Tres and of adjacent residual pathologic tissue as defined by clinical examination and by MRI Intermediate Risk (CTV-T IR ) : represents the GTV- Tinit as superimposed on the topography at the time of brachytherapy, together with a margin surrounding the anatomical cervix border (CTV-THR) in areas without an initial GTV- Tinit . By definition, it includes all of the CTV-THR and margins as appropriate. 16 It is defined as one or more of the following: - residual palpable mass; - residual visible mucosal change; - pathologic induration; - residual gray zones (MRI);

17. Principles of brachytherapy

18. 18 Slide Courtesy: Dr Umesh Mahantshetty

19. Dose distribution - icbt 19 Slide Courtesy: Dr Umesh Mahantshetty

20. Final takeaways 20 SLIDE COURTESY: DR BHAVANA RAI NA 10% 10%

21. Procedure of intracavitary application 21

22. Steps of intracavitary application Patient Identity confirmation & Pre- anaesthetic Checklist Anaesthesia induction – GA/Spinal ( ICBT can also be done under Local) Painting & Draping – Umblicus to mid thigh Examination under Anaesthesia Determination of Tandem Length by using the Uterine Sound Placing the Uterine Tandem & Ovoids ( Preferably under USG Guidance), applicator assesmbly is locked in place. In case of Hybrid Applicators ( IC + IS) – Needles are inserted at this step. Vaginal packing is done – prevents displacement of Applicator + removes the OARs away from the Tandem & Ovoids . 22

23. 23 Instruments Tray Intra-op USG showing applicator-in-situ Uterine Sounding (& dilation if required) EUA Tandem & Ovoid Insertion Packing with Iodine soaked gauge

24. 24

25. Imaging protocol After application – Pt is shifted for Imaging For 3D Planning - Planning CT scan with Bladder Contrast ( 2 mm scan) For 2D Planning – AP & orthogonal X rays For MR Based Planning – 3T MRI – Para sagittal, Para-coronal, Para-axial sections ( 3-5 mm) 25

26. orthogonal planning Simulation – Using AP & Orthogonal Radiographs with Markers Tandem – Should Bisect the Ovoids in AP & Lateral Films - Should be 1/3 distance between Pubis& Sacrum Should be midway between Sacrum & Bladder Tip should be Below Promontory Bladder & Rectum should be packed away from the implant with no packing above the ovoids 26

27. Image Guided BT planning 27 PAC Clinical Evaluation Verification of labs CT MR ( Gold std) TRUS with CT

28. OAR delineation Important OARs: Bladder, Rectum, Sigmoid, Vagina When assessing late effects from brachytherapy, small organ (wall) volumes irradiated to a high dose are imp. For Organs at Risk (OAR) the minimum dose in the most irradiated tissue volume is recommended for reporting: 0.1, 1, and 2 cm to be contoured 28 ICRU 89

29. Treatment planning 29 Treatment plans are generated in Oncentra Brachytherapy Planning System v4.6.0. Applicator reconstruction performed with a 3D model of the Applicator generated with the Applicator library manager ( Flexitron HDR Co-60, Elekta, Sweden). ( Needle reconstruction if required is performed manually based on MR/CT images.)

30. Treatment planning 30 Source Activation – Done according to Standard Loading

31. Treatment planning 31 Dose is Normalised to Point A

32. Treatment planning 32 Dose is Optimised (Manually or Graphically) Be careful not to change the peardose isodose shape while doing manual optimization!!

33. Treatment planning 33 Dose is prescribed to Point A or Targets ( eg D90HRCTV)

34. Plan evaluation 34 EMBRACE-II

35. Evolution of bt applicators

36. Choice of Applicator Depends: Extent / geometry of disease Space for placement / size Availability Experience of the Physician & Physicist INTRACAVITARY APPLICATORS Ring applicator - Stockholm Tandem Ovoid - Manchester, Fletcher, Henschke , etc Tandem Cylinder – Single channel, Multi-Channe l ( eg Miami) INTERSTITIAL APPLICATORS MUPIT, Syed Neblet , Kelowna , Indigenous templates with needles,tubes HYBRID APPLICATORS Aarhus Applicator

37. Fletcher Family tandem and colpostat / Ovoid system Fletcher applicator was developed in 1952 1950s – Preloaded Fletcher Applicator Made up of stainless steel with cylindrical shape ovoids . Each ovoid has its discrete tube, which facilitates the movement of the ovoid anteriorly or posteriorly. Ovoid tubes were held together with a scissors-type joint Tungsten shielding was located on the medial aspects of the anterior and posterior ovoids to minimize the dose to the bladder and rectum 1960s - Fletcher‑suit applicator Fletcher design improved by Suit to accommodate Afterloading . Loading and unloading of the radium carriers with this system was quicker than standard preloaded Fletcher applicators.

38. Most commonly used applicators Tandem & 2 ovoids held together with a flange. The ovoids are 2.0 cm, 2.5 cm, and 3.0 cm in diameter with and without shielding. They are angled at 40 degree to the vaginal axis. Designed to deliver adequate doses to uterus/cervix, upper vagina (2-2.5 cm) and medial parametrium by a standard pear-shaped dose distribution. Tandem and ovoid (TO) – FLETCHER SUIT APPLICATOR ** ICRU 89

39. Tandem and ring (TR) applicator – Based on Stockholm System The vaginal ring is perpendicular and fixed to the rigid tandem and rests against the cervix, secured by gauze packing. The metal ring is covered by a plastic cap, which places the vaginal mucosa 0.6 cm from the source path. Advantages of : easier placement and fixed reproducible geometry. Ideal for patients with shallow or obliterated vaginal fornices and with non-bulky disease** Short distance from the ring to the vaginal mucosa can result in Increase dose to the vaginal surface ( Berger et al., 2007) Sometimes not suitable for patients with a narrow vagina Usually preferred in case of shallow fornices Eg : Vienna, Arhus, Venezia, Mick Applicator) ** ICRU 89

40. TANDEM- CYLINDER APPLICATORS Consists of central tandem and vaginal cylinders Useful in vaginal spread of disease (to treat cervix and vagina in a single BT application) Cylinders vary in diameter from 2.0 cm to 4.0 cm and have varying lengths Dose distribution: Cylindrical Lower absorbed dose in the lateral cervix and pelvic sidewall due to lack of ovoid and ring Single source channel, lateral throw-off of dose to parametrium is less Multichannel and shielded cylinder applicators- Possible to shape the dose distribution-Better protection of bladder and rectum Increased length of treated vagina in extensive disease. High rectum and bladder toxicity For Vaginal cuff BT – dose prescribed to 5mm distance from surface of applicator

41. Interstitial applicators In patients where an acceptable D90 of the HR-CTV cannot be feasibly achieved using ICBT alone, both HBT or ISBT should be evaluated, as D90 is strongly associated with local control.  Commonly used templates MUPIT and Syed Neblett . Others: Benidorm template (MRI compatible), Pamplona applicator, Kelowna applicator, customized templates Usually Consists of a perineal template with provision of vaginal cylinder and tandem. Interstitial implantation is helpful in patients with **: Bulky infiltrative extensive disease, Anatomical unfavorable topography such as asymmetrical tumor growth, Narrow vagina or Obliterated endo-cervical canal, Extensive Paremetrial & lateral pelvic wall involvement Vaginal spread of disease, or recurrent disease. 41 **ICRU 89

42. MUPIT (Martinez Universal Perineal Interstitial Template) Single template for multiple sites • Used for cervical, vaginal, female urethral, perineal, prostatic and anorectal carcinomas. Consists of Flat acrylic template and flat acrylic cover late. (11x8x1cm) Acrylic obturator (two sets), screws and stainless steel needles Three large holes are located along the vertical centerline. The top slot hole is for the passage of Foley catheter from the urethra ; Central & Bottom holes for the vaginal and rectal cylinders. Array of holes that for the most part determine the geometry of source placement with respect to anatomic structures. 42

43. SYED-NEBLETT TEMPLATE Two Plastic / Silicone plates 1.2 cm thick 2 cm central hole for vaginal obturator, 34 holes with rubber rings ( O-rings) drilled 1 cm apart in incomplete concentric circles to accommodate the guide needles. Vaginal obturator 2 cm diameter Three different lengths of 12, 15 and 18 cm Central tunnel to accommodate tandem Six longitudinal grooves on the surface for guide needles Embedded screw at it’s distal end to secure the tandem. 17 Gauge hollow needles 20 cm long. Long axis held perpendicular to sagittal plane to treat parametria. 43

44. Combined Intracavitary Interstitial Applicators 44 Indication: Disease extension into parametrium beyond the medial third at the time of BT, Large endocervical disease ( not covered by ICA) The needles/tubes inserted through the array of holes in the ovoids /ring into the medial parametrium, in parallel direction to the tandem ( e.g. Vienna applicator) If the residual disease extends into the lateral parametrium, then insertion of additional oblique needles/tubes in the lateral parametrium can be attempted ( eg Venezia, Geneva applicator). Ladbury et al, Brachytherapy Sept 2023 Use of HBT can typically permit extension of dose coverage by an additional 1–2 cm beyond what can be achieved with an IC alone technique.

45. venezia 45 Venezia – Advanced Gynaecological Applicator by Elekta Sweden 2 Lunar Shaped Ovoids which click together to form a ring Allows insertion of Interstitial Tubes – 6/8 depending on size of Ovoid ( 22/26 mm) Option of Parallel/ Straight needles available Advantages over ICA: Better Dosimetric profile, allows to treat distal parametrial residue Advantages over MUPIT : less invasive & painful - Vaginal caps & Perineal template provide the ability to treat the caudal vagina.

46. geneva - IC + IS Applicator - T-O type applicator – Tandem available in different uterine lengths – 30-80 mm & 3 different angles ( 15,30,45 degrees) Ovoids – 13-40 mm Ability to insert parallel needles 46

47. summarizing CLINICAL SCENARIO APPLICATOR TYPE Intact cervix, no residue post EBRT ICBT alone ( eg Fletcher Suit ) Intact cervix, with min residue post EBRT ( NMD < 2 cm) ICBT alone ( eg Fletcher Suit ) Intact cervix, with residue post EBRT ( NMD > 2 cm) IC + IS BT ( eg Vienna II, Venezia ) Intact cervix with residual disease extending upto LPW ISBT Post- op Cervix with no residue Vaginal Cylinder Post- op Cervix with residue ISBT Cylinder with interstitial needles 47

48. BIBLIOGRAPHY 48 ICRU 89 PEREZ & BRADY’S Principles & Practices of Brachytherapy Recommendations from Gynaecological (GYN) GEC-ESTRO Working Group* (I): concepts and terms in 3D image based 3D treatment planning in cervix cancer brachytherapy with emphasis on MRI assessment of GTV and CTV 7 TH AROI ESTRO GYN TEACHING COURSE MATERIAL Practical Radiation Oncology By Supriya Mallick ELEKTA BRACHY APPLICATORS MANUAL