Why Quality Assurance Test Is Most Important ?

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

• CT Angio is 12 mSv
• PET-CT scan is 25 mSv
• CT Chest is 7-8 mSv
• CT – Abdomen & Pelvis is 10 mSv
• X-Ray Chest is 0.1 mSv
• Dental X-Ray is 0.005 mSv
• Bone densitometry is 0.001 mSv
• Mammography is 0.4 mSv

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:

• X Ray Machine (Fixed & Mobile)
• X Ray Machine (Fluoroscopy)
• Portable X Ray Machines
• Digital Radiography (DR)
• C Arm
• Dental X Ray Machines
• Dental Orthopantogram (OPG)
• Cone Beam Computed Tomography (CBCT)
• Mammography
• Bone Mineral Density (BMD)
• CT
• Cath Lab
• Interventional Radiology

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.