Interlocking Systems

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    Interlocking systems are one of the significant systems in the radiotherapy installation or treatment unit. The interlocking systems should be properly planned before constructing the treatment unit room and it should be arranged in such way that to achieve all the required safety features of the treatment unit or installation. The interlocking can be divided into several types out of which a few important types are discussed below.

They are,

1. Machine interlocking systems

2. Door interlocking systems 

3. Fire interlocking systems

Machine Interlocking Systems:

    Machine interlocking systems are one of the interlock will arise due to the problem in machine system and its hardware. In linac the interlock numbers will vary for different vendors for example in varian approximately 48 interlocking variables are there. If any, of these got repaired or malfunction means the interlock will be enabled and we cannot able to treat the patient until or unless cleared or necessary action taken against that problem. Some of the most common interlock occurs in the linac machines are mentioned below.

Gas Pressure

Temperature and Pressure

Water level

Touch guard

Mlc’s are not ready, jaws are not ready


Door interlocking System:

    Treatment room door interlocking system is crucial interlocking system. It ensures the technologist that treatment unit room door is closed or no body is inside during the treatment. The door interlocking system is directly connected to the control console of the machine. If the treatment unit room door is open we cannot execute the treatment it will display the information like room doors are open in linear accelerators and other radiotherapy machines are in use.

The first and foremost duty of the radiation technologist is check all the interlocking systems with some special attention to door interlocking system. If they found any problem means it needs to inform and regular and necessary action should be taken in that regard.
Fire Interlocking Systems:

 However, it is not popular interlocking systems its helpful potential situation like sudden fire happens in the treatment and associated rooms. The interlocking system will be enabled and display fire. Special attention should be required ignoring this leads to potential damage to treatment unit and others.


1. Interlocking systems are useful in

a) Treatment purposes

b) Safety of the Radiation Worker

c) Safety of the patients

d) All

2. The problem regarding the interlocking systems should be informed to,

a) Radiation oncologist

b) Director

c) Medical Physicist

c) All


d) All.

c) Medical Physicist.

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