What is Quality Assurance Test for
Radiation Equipment?
As per AERB (Atomic Energy Regulatory Board), Government of
India Quality Assurance (QA) Test of radiation equipment like diagnostic x-ray,
Dental X-ray, CT machine, C-Arm machine means systematic actions will perform
satisfactorily in compliance with safety standards specified by AERB.
Why are QA tests being mandatory?
The main objective of Quality Assurance for radiation equipment is
to ensure that minimum radiation dose to the patient(s), high end image quality
of radiological procedure is achieved. Excellent quality of image is necessary
for accurate diagnosis with minimum possible dose of radiation.
Why is AERB concerned about radiation dose/ exposure to patients?
Human
body can cope with some minimal levels of radiation exposure without any harm.
Hence X-ray equipment are used because they serve a more useful purpose of
diagnosing treatable diseases with minimal radiation. However, careless exposure to and excessive
cumulative radiation over short periods of time can be very harmful to health. Therefore,
AERB regulates use of radiology equipment.
So, how much radiation exposure is harmful for human body?
Large
doses of radiation/acute radiation exposure can destroy the CNS (Central
Nervous System), Red blood corpuscles, White blood corpuscles, and after all
the immune system unable to fight off with victim cells.
For
example, the whole-body exposure threshold for acute hematopoietic
syndrome or "radiation sickness" is 500 mGy. Radiation
doses that exceed a minimum (threshold) level can cause undesirable effects
such as depression of the blood cell-forming process (threshold dose
= 500 mSv, 50 rem) or cataracts (threshold dose = 5,000
mSv, 500 rem).
Epidemiologic studies have found that the estimated lifetime risk of dying from cancer is greater by about 0.004% per mSv (0.04% per rem) of radiation dose to the whole body (NRC, 1990).
Analyzed data of radiation doses we receive during radiology investigation:
Approximate effective radiation dose
So
based on the above data, 4 PET-CT scans/ 8 CT Angios / 10-12 CTs/ 1000
X-Rays/ 20000 Dental X-Rays/ 250 mammograms or 100000 Doxas add up to 100mSv
cumulative radiation which can cause cancer.
In general, if we are not careful it is
possible for various reasons that cumulative exposures could lead to
unacceptable radiation dose.
As
per AERB, the current occupational limit of exposure per
year for a worker (Adult) using radiation is “as low as reasonably
achievable; however, not to exceed 5,0 mSv” above the 3 mSv of natural sources
of radiation and any medical radiation.
These radiation equipment’s require QA testing:
All the above radiation equipment is covered under the AERB QA
program.
What is the AERB QA Program in
its essence?
Quality
Assurance for radiation equipment as per the AERB program is carried-out
in two parts first part for manufacturer and the second is for Supplier/end
user.
First – the performance evaluation of radiation equipment at the
manufacturing stage (called type approval from AERB). Type approval is the
responsibility of the manufacturer. AERB provides type approval of radiation
equipment if the model is as per AERB guidelines.
Second – acceptance testing after the installation of X-ray
equipment at user’s institution(s) to ensure its conformity with the
specifications (Operating license). This part is responsibility of the user.
The QA tests should be carried out thereafter at regular intervals
(periodicity-once in two years) and also after repairs of the equipment or when
equipment malfunctions are suspected. This is to ensure that the equipment
continues to function as per prescribed standards.
A perfect
radiation equipment procedure is one that provides the highest quality
diagnostic information at the lowest radiation risk to the patient, but quality
must always take precedence over radiation dose.