Total body irradiation

1. TOTAL BODY IRRADIATION
DR DIVYA KUKREJA

2. • Special radiotherapy technique that delivers uniform dose to patient’s whole body.
• Used to treat benign and malignant disorders.

3. HISTORICAL DEVELOPMENT

4. CLINICAL IMPLICATIONS OF TBI
• Prior to Haematopoetic Stem Cell Transplant (HSCT)—
As a part of conditioning regime
Purpose -
1. Cytotoxic
2. Immunomodulatory
• The conditioning regimen may be based on chemotherapyalone; however,
the most common pre-transplant conditioning is a combination of high dose
chemotherapy and TBI

5. • Advantages-
1. No sparing of sanctuary sites like brain, testis.
2. Dose delivered is homogenous and independent of blood supply.
3. Dose distribution may be tailored either by blocking critical organs or by boosting
areas at highest risk of recurrence.

6. • Diseases treated with HSCT are -
• -Various types of leukaemia (acute lymphoblastic leukaemia, chronic
myelogenous leukaemia)
• -Non Hodgkin Lymphoma
• -Multiple myeloma
• -Neuroblastoma
• -Ewing’s sarcoma
• Non neoplastic disorders– Aplastic anaemia, Fanconi’s anaemia, Wiscott-
Aldrich syndrome

7. CLINICAL TBI CATEGORIES
• High dose / myeloablative TBI- Dose delivery in a single session (dose: 7.5 to 9
Gy) or in up to six fractions of 2 Gy each in 3 days (total dose: 12 Gy)
• Low dose / non-myeloablative TBI- Dose delivery in 10 to 15 fractions of 10 to
15 cGy each

9. TBI IRRADIATORS
• TBI techniques use megavoltage photon beams produced by Cobalt-60 machines
or linear accelerators (LINAC).
• TBI procedures may be performed on specially designed machine or on standard
radiotherapy equipment.
• The beams used for TBI are:
• Stationary
• Moving- Translational or rotational motion
• Usually, parallel-opposed beams used

11. EXAMPLE 1
• Treatment at extended source-surface distance
• Radiation field covers the whole patient

12. EXAMPLE 2
• Memorial Sloan-Kettering Cancer Center (MSKCC), New York, USA

13. EXAMPLE 3
• McGill University, Montreal, Canada

14. EXAMPLE 4
• Translational technique (patient moves
through beam)

15. EXAMPLE 5
• Sweeping beam technique with a column mounted LINAC

16. UNIVERSITY OF MINNESOTA TECHNIQUE
• Special couch – back supported – legs
collapsed – arms laterally positioned to
follow body contour shadowing the lungs
• Distances measured between external bony
landmarks
• Sagittal laser to position the patient
• Compensators for H&N, lungs, legs

17. COMPENSATOR DESIGN
• TBI protocols require ±10% dose uniformity – hence compensators!
• Compensator design for TBI is complicated – due to large variations, no
immobilization, tissue heterogeneities

18. SKIN SURFACE DOSE
• Leukemia can infiltrate skin, so no skin sparing is required.
• Surface dose is increased by-
1. Bolus
2. Beam spoilers- 1-2 cm acrylic sheet, kept at a distance of 10 cm from patient

19. DOSE RATE AND DOSE PRESCRIPTION
• Dose rate should be less than 10cGy/min as higher dose rates associated with
increased lung toxicity.
• Dose is usually prescribed at midplane, at the level of umbilicus.

20. TREATMENT UNIT BACKUP
• Once TBI treatment started, it must be completed without any break.
• Backup treatment unit must be there in case a machine goes down.

21. IN VIVO DOSIMETRY
• A suitable in-vivo dosimetry system should be available and commissioned for
dose measurements.
• TLD system
• Diode system
• Ion chamber with special build-up caps
• Radio-chromic film dosimetry

22. RESOURCES FOR ESTABLISHING TBI
TECHNIQUE

23. COMPLICATIONS OF TBI
1. LOW DOSE TBI
• Thrombocytopenia
• Nausea and vomiting
2. HIGH DOSE TBI
• Acute toxicity
• Delayed toxicity

24. ACUTE TOXICITY
• Nausea, vomiting
• Headache
• Diarrhoea
• Xerostomia
• Oral and oesophageal mucositis
• Parotitis
• Alopecia

25. DELAYED TOXICITY
• 1) LUNG (Dose-limiting)
• Interstitial pneumonitis
• 2) LIVER
• Veno-occlusive disease of liver or sinusoidal obstructive syndrome
• 3) LENS
• Cataract
• 4)KIDNEY
• 5) GROWTH, GONADAL AND ENDOCRINE EFFECTS

26. • 6) SECONDARY CANCERS
-Myelodysplastic syndrome
-AML
-PTLD (post-transplant lymphoproliferative disorder)

27. SUMMARY
• Dose variation should be within 10% of prescribed dose.
• AP-PA technique is preferable because of better dose uniformity.
• Bilateral technique is more comfortable for patient (patient seated or lying
down) – however, dose uniformity may not be good due to larger variation in
body thickness along the path of beam.
• Beam spoiler used to increase surface dose.
• Used in HSCT due to cytotoxic and immunomodulatory action.

28. THANK YOU