Therac-25

br Therac-25 1

Running head : Therac-25

Therac-25

Seema Mishra

India Therac-25 2

Abstract

Therac-25 is a radiation therapy machine which was involved with some accidents that

lead to patient 's death leaving behind the health informers to discuss whether software

control of safety-critical systems is worth or not . Therac-25 is considered as socio-

technical system as it is a complex mixture of technology and people The safety of

Therac-25 is not the question of the machine alone but the people who are involved in the

p whole process are also answerable . If the TV in the patient 's room is unplugged it

becomes impossible for the operator to monitor the exact status of the patient and he does

not know when the patient is in trouble . So safety is the responsibility of all involved in

the entire socio-technical system and only the machine is not to be blamed . Therac-25 3 Therac-25

Therac-25 was designed for radiation therapy for cancer patients that was computerized

and was assured that it was virtually impossible ' to give overdose to any patient with it

When a cancer patient is advised for radiation he or she is told that because of the

radiation process there will be a certain level of discomfort and so the patient is mentally

prepared for that . The therapy takes more than one sitting and there is a feeling of slight

sunburn on the area that is treated . But in some cases more than scheduled radiation was

given and that resulted in death for some patients . When doctor decides that a particular

patient should be treated with radiation rays , he or she also prescribes how many rads (radiation absorbed dose ) should the patient receive . These are instructions to the medical

linear accelerator operator who will provide rads with all precautions

Initially this therapy engaged the operators a lot and they had to spend a lot of time

arranging the machine for the treatment . With the introduction of Therac-25 this

laborious work got easy for the operators . Along with the set up the computer also

monitored the safety measures , which left the operators with nominal work . When the

cancer treatment facilities are housed in large hospitals they are monitored by experts

from time to time but when these are in profit making organizations they are not properly

checked at regular intervals . The radiation is used to treat cancerous tissues but if it is not

given in proper proportion it is harmful

Therac-25 helped the radiation beams to enter into the body more deeply and without

harming intervening tissues . It produced low energy electron beams for outer surface and

high intensity electron beam that entered into the body . This is the reason why Therac-25 Therac-25 4

was called a dual mode machine . While deciding whether or not Therac-25 is worth , one

will have to study the case narrative materials provided because here we are at the

decision maker 's seat . We also need to study the design of the machine and an overview

of its history...