isocentric teleisotope machine..

2. Definition
:- The isotope which are used in
teletherapy is known as teleisotope
machine.

3. PRINCIPLE
 Patient are treated by iso-centric tele-isotope machine so the
location of tumor is positioned of the axis of rotation of the
treatment unit.
 This type of machine is useful in rotational therapy /arch therapy.
 In isocentric therapy dose is measured when the tumor is
positioned at the axis of rotation.
 Tele-isocentric teleisotope machine are designed to rotate
about an axis located at fixed distance from source is 80-100cm.
 Lazers light also provided with this therapy because they
produce narrow light beam that intersects at iso-centric.
 It provides proper alignment on patient
 A counter weights balance is provided with equipment which
serves a primary barrier reduces shielding required for
treatment.

4. Cont.
 co-60 unit is preferred as iso-centric teletherapy unit because
they have no. of high tension cable to get an angle during the
rotation, so the unit is rotated along the axis of tumor.
 Iso-centric positioning is used to locate at the centre of tumor
but care should be taken to adjust the radiation field.

8. ISO-CENTRIC TECHNIQUE
 All teletherapy unit can rotate about a horizontal axis. In this
therapy units or machine gantry is capable of rotating through
360°
 The isocentric is the point of intersection of collimators axis and
the gantry axis of rotation.
 The isocentric technique of irradiation consist of placing the
isocentre of the machine at a depth within the patient and
directing the beam from different direction.This technique can be
done in 2 ways:
 SAD method
 Rotational therapy

10. SAD METHOD
 This is a isocentric type of treatment by using stationary
beam
 Distance of the source from the iso-center remains constant
irrespective of the beam direction
 SAD refers the source to axis of beam rotation distance
 The field size is referred at the tumor level since the slash
is above the tumor
 It will encounter a lesser field size than at the tumor for a
given beam
SSD= SAD-d

12. Rotational therapy technique
 Beam moves contineously about the point or the patient is
rotated while the beam is field fixed
 Primary aim of using rotational technique to reduce the skin
reaction
 Source to tumor distance is fixed and the ssd is keeps on
changing as the machine rotates
 Size of the field is fixed at the tumor while that at the skin varies
 Rotational therapy is well suited for small deep seated tumor
which is vary near the centre of counter
e.g.- oesophagus
Bladder
Chordomas of vertebrae