tele cobalt therapy and tele therapy with

teletherapy with main focus on cobalt 60 machine. machine design and parts are discussed at lenght. source loading pitures and pictures of real teletherapy machine.
INTRODUCTION
TELETHERAPY
TYPES OF TELETHERAPY
COBALT 60
CLINAC

RADIOTHERAPY
Clinical modality dealing with the use of ionising radiations in the treatment of patients with malignant neoplasms and occasionally benign diseases.

AIM OF RADIOTHERAPY
Delivery of known and uniform dose of radiation to a zone believed to encompass the tumour, and as little radiation as possible elsewhere.

TELETHERAPY(external beam radiotherapy)
Treatments where the external source of radiation is away from the part being treated.
TYPES OF TELETHERAPY

GRENZ THERAPY(1mV)
Isotopic teletherapy machines
Treatment machines incorporating gamma ray sources for use in EBRT
The important characteristics of radioisotopes in EBRT
1. High gamma ray energy
2. High specific activity
3. Relatively long half life
4. Large specific air kerma rate constant
5. Must be available in large quantities





COBALT 60
Co 60 was discovered by Glenn Seaborg and John Livingood at California Berkeley University in 1930.
Co 60 teletherapy unit was invented by H.E. JOHNS along with national research council in Canada in early 1950s.
The first two cobalt teletherapy units were installed in Canada in 1951
at the Saskatoon Cancer Clinic and the Victoria Hospital, London Ontario-first patient
Cobalt machines are arranged on a gantry so the source may rotate on horizontal axis.
This is referred to as isocenter of the machine.
Source to skin distance is usually 80 to 100cm

Co 59(hard, stable. Bluish gray, easily breakable) is
irradiated with neutrons in a nuclear reactor to
produce Co 60.
Co 60 decays by beta decay to the stable isotope
nickel 60.
The beta particles(0.31MeV) are absorbed in
the cobalt metal and stainless steel capsules (emits
Bremsstrahlung and small amount characteristic X-rays).


Produce 2 gamma rays during de-excitation of
60Ni to ground sate : 1.17 and 1.33 MeV(avg 1.25MeV),
the useful treatment beams.
50% depth dose is 10 cm, Dmax at 0.5cm from surface.
Replaced every 5-7 yrs when dose rate is too low..

1. COBALT 60 Presenter: Dr. Harshitha , DNB resident Moderator: Dr.Bijina . Senior Medical physicist, HCG

2. OVERVIEW INTRODUCTION TELETHERAPY TYPES OF TELETHERAPY COBALT 60 CLINAC

3. RADIOTHERAPY Clinical modality dealing with the use of ionising radiations in the treatment of patients with malignant neoplasms and occasionally benign diseases. AIM OF RADIOTHERAPY Delivery of known and uniform dose of radiation to a zone believed to encompass the tumour, and as little radiation as possible elsewhere. TELETHERAPY(external beam radiotherapy) Treatments where the external source of radiation is away from the part being treated.

4. TYPES OF TELETHERAPY GRENZ THERAPY(<20kV) CONTACT THERAPY(40-50kV) SUPERFICIAL THERAPY(50-150kV) ORTHOVOLTAGE THERAPY(150-500kV) SUPERVOLTAGE THERAPY(500-1000kV) MEGAVOLTAGE THERAPY(>1mV )

5. Isotopic teletherapy machines Treatment machines incorporating gamma ray sources for use in EBRT The important characteristics of radioisotopes in EBRT 1. High gamma ray energy 2. High specific activity 3. Relatively long half life 4. Large specific air kerma rate constant 5. Must be available in large quantities Common radioisotopes Energy(MeV) Means of production Half life Radium 226 0.830 Radioactive decay of 238 U 1622yrs Caesium 137 0.662 Fission by-product 30yrs Cobalt 60 1.250 (1.17,1.33) 59 Co + n in reactor fission 5.26yrs Iridium 192 0.380 191 Ir + n -fission 74.2d

6. COBALT 60 Co 60 was discovered by Glenn Seaborg and John Livingood at California Berkeley University in 1930. Co 60 teletherapy unit was invented by H.E. JOHNS along with national research council in Canada in early 1950s. The first two cobalt teletherapy units were installed in Canada in 1951 at the Saskatoon Cancer Clinic and the Victoria Hospital, London Ontario-first patient

7. Cobalt machines are arranged on a gantry so the source may rotate on horizontal axis. This is referred to as isocenter of the machine. Source to skin distance is usually 80 to 100cm

8. . Parts of a teletherapy machine A radioactive source A source housing, including beam collimator and source movement mechanism A gantry and stand in isocentric machines or a housing support assembly in stand alone machines A patient support assembly A machine console

9. About cobalt Co 59(hard, stable. Bluish gray, easily breakable) is irradiated with neutrons in a nuclear reactor to produce Co 60. Co 60 decays by beta decay to the stable isotope nickel 60. The beta particles(0.31MeV) are absorbed in the cobalt metal and stainless steel capsules (emits Bremsstrahlung and small amount characteristic X-rays).

10. Produce 2 gamma rays during de-excitation of 60 Ni to ground sate : 1.17 and 1.33 MeV ( avg 1.25MeV), the useful treatment beams. 50% depth dose is 10 cm, D max at 0.5cm from surface. Replaced every 5-7 yrs when dose rate is too low..

11. Radioactive source The 60 Co source, usually in the form of solid cylinder, discs or pellets, is contained inside a standard stainless steel capsule and sealed by welding. This capsules is placed into another steel capsule, again sealed by welding .(1X2.5cm) This double welded seal is to prevent any leakage.

12. Source Housing Called the “source head”, includes shielding, beam collimator and source movement mechanism. Consist of steel shell filled with lead for shielding purposes D evice for bringing the source in front of an opening in the head . heavy metal alloy sleeve is provided to form an additional primary shield when the source is in the OFF position.

13. Source movement is designed so that in the event of treatment termination or device failure the source is automatically returned to the shielded condition. An emergency pushbar (T-bar) can be used to manually return the source to the shielded position, if necessary.

14. COLLIMATORS Provide beams of desired shape and size. Provides only square and rectangular radiation fields 5X5cm to 35*35cm 2 at 80 cm from surface. Trimmer bars can be used to reduce the beam penumbra, which is large because of the relatively large source size of approximately 1.5 inches.

15. Cross-hairs and a field light are used to delineate the central ray and field dimensions. optical visualization of the radiation field.

16. GANTRY Gantry rotates by 360 . The rotational movement of the gantry is motorized and controlled in two directions ; the rotation speed can be adjusted. Its most often mounted isocentically, allowing the beam to rotate about the patient at a fixed SAD. They can be used either as fixed field machines or rotation units .

17. ISOCENTRE : The point at which the axis of rotation of gantry, collimator and couch coincide Longitudinal Lateral Vertical Rotational

18. PATIENT SUPPORT ASSEMBLY Treatment bed has motorised movements in 7 directions : The treatment bed has a nylon mesh as it provides negligible build-up for under the couch treatments. The couch is made of steel. The patient weight capacity is 136kg.

19. CONTROL CONSOLE Situated outside the bunker. Interlocks are present on the console for Air pressure Door Head lock OFF shield Treatment mode Wedge filter Tray interlock Timer Source on and off indicator

20. TIMER The prescribed target dose is delivered with the help of two treatment timers: Primary timer – actually controls the treatment time Secondary timer – accounts for the source movement from OFF to ON position and again to OFF position (shutter error) SOURCE ON AND OFF INDICATOR RED - ON GREEN - OFF AMBER – TRANSIT

21. PERIODIC QUALITY ASSURANCEOF COBALT-60 UNITS FREQUENCY PROCEDURE TOLERANCE DAILY SAFETY DOOR INTERLOCK RADIATION ROOM MONITOR AUDIOVISUALMONITOR MECHANICAL LASERS DISTANCE INDICATOR FUNCTIONAL FUNCTIONAL FUNCTIONAL 2mm 2mm WEEKLY CHECK OFSOURCE POSITIONING 3mm MONTHLY DOSIMETRY OUTPUT CONSTANCY MECHANICAL CHECKS LIGHT/RADIAION FIELD COINCIDENCE FIELD SIZE INDICATOR (COLLIMATOR SETTING) GANTRY AND COLLIMATOR ANGLE INDICATOR 2% 3mm 2mm 1 degree

22. CONT… FREQUENCY PROCEDURE TOLERANCE CROSS HAIR CENTERING LATCHING OF WEDGES, TRAYS SAFETY INTERLOCKS EMERGENCY OFF WEDGE INTERLOCKS 1mm FUNCTIONAL FUNCTIONAL FUNCTIONAL ANUUAL DOSIMETRY OUTPUT CONSTANCY FIELD SIZE DEPENDECE OF OUTPUT CONSTANCY CENTRAL AXIS DOSIMETRY PARAMETER CONSTANCY(PDD/TAR) TRANSMISSION FACTOR CONSTANCY FOR ALL STANDARD ACCESSORIES WEDGE TRANSMISSION FACTOR CONSTANCY TIMER LINEARITY AND ERROR OUTPUT CONSTANCY VS GANTRY ANGLE 2% 2% 2% 2% 2% 1% 2%

23. CONT… FREQUENCY PROCEDURE TOLERANCE BEAM UNIFORMITY VS GANTRY ANGLE SAFETY INTERLOCKS FOLLOW TEST PROCEDURES OF MANUFACTURERS MECHANICAL CHECKS COLLIMATOR ROTATION ISOCENTER GANTRY ROTATION ISOCENTER COUCH ROTATION ISOCENTER COINCIDENCE OF COLLIMATOR, GANTRY, COUCH AXIS WITH ISOCENTER COINCIDENCE OF RADIATION AND MECHANICAL ISOCENTER TABLETOP SAG VERTICAL TRAVEL OF TABLE FIELD-LIGHT INTENSITY 3% FUNCTIONAL 2mm DIAMETER 2mm DIAMETER 2mm DIAMETER 2mm DIAMETER 2mm DIAMETER 2mm 2mm FUNCTIONAL

24. Bunker layout

25. Room Walls: The walls should be made of concrete or other dense materials to prevent radiation leakage. The thickness of the walls typically ranges from 1.5 to 2 meters, depending on the radiation shielding requirements. Floor: Shielding is also incorporated in the floor, as radiation can scatter downwards. Ceiling: A thick concrete ceiling prevents any radiation leakage above the treatment room. Doors: Lead-lined doors are typically used for entry/exit. Interlocks and emergency stop functions are commonly used to prevent accidental exposure during treatment.

26. BHABHATRON Indigenous cobalt 60 teletherapy machine developed in BARC. Fully closable collimator for improved radiation safety. SAD 80cm Advanced Centre for Treatment, Research and Education in Cancer (ACTREC) in Navi Mumbai in 2005

27. Bhabhatron 3i 28 pair dynamic MLC – 3Dcrt and IMRT 6D couch Sad 80 with 25X25cm field Kv , cbct , furoscopy imaging with dicom compatatbility Counter weight wich acts as beam stopper Higher safety

28. Thank you