The DRLs should be set in terms of the practical dose quantities used to monitor practice.
For radiography,
air kerma - area product and entrance surface air kerma are recommended DRL quantities which are closely similar to Entrance Surface Dose (ESD) and it can be easily estimated by dose area product meter in routine practice.
Radiation protection survey and quality assurance of X-ray installations
The radiation exposure levels during the operation of the radiological equipment were measured for the radiological installation and quality control and quality assurance procedures prescribed by Atomic Energy Regulatory Board for x-ray equipment was carried out by using PTW NOMAX multimeter to ensure the stability,
filtration and output consistency of x-ray equipment.
The machine setup,
procedure,
and exposure protocols were optimized to be within tolerance limits as per AERB guidelines
Radiation protection and safety awareness amongst the radiation professionals
Although the radiation workers and professionals are trained to work in the radiation field,
constant reassessment and updating are also required to keep them abreast with the technological and safety advances.
With an increase in the use of radiation,
the probability of occurrence of radiation injuries and hazards (in the case of inadvertent accidents or malpractices) also increases.
This training,
however,
should not be restricted to learning the functioning of a department but must encompass the radiation protection and safety aspects.
The inclusion of radiation safety with special emphasis on safe work practices and safety protocols instills confidence in the radiation professionals and reduces the anxiety and fear that surrounds radiation usage.
We have conducted specialized awareness programme for all radiation workers of the institute,
radiological diagnosticians,
interventionists,
anesthesiologists,
post-graduate trainees,
paramedical and nursing staff and trainees.
The impact of such programmes was assessed through evaluation questionnaires (Pre and Post).
Although the radiation professionals have undergone training for radiation safety,
they were found to be less confident in applying it in routine practice.
A lacuna was also observed in the awareness about regulatory aspects and dose limits.
The training programme showed some improvement but it threw light on the importance of regular and periodic training sessions.
(Fig.1)
Fig. 1
Validation of dose measurement for DRL
Initially for validation of effective dose measured from DAP for each examination site was done and compared with the dose values obtained on whole body anthropomorphic Phantom "Kyoto Kagaku PBU-50" (Fig) by PTW Nomex multimeter and by Monte Carlo simulation under standard imaging parameters and mimicking the patient geometry.
(Fig.
2)
Fig. 2: X-Ray machine connected with DAP meter and multimeter place on the site going to view
Fig. 3: Multimeter kept on the Human Body Phantom at chest site
The observed readings are within limits as compared to the values of National Radiological Protection Board (NRPB) in the UK.
The difference between the organ site doses measured by DAP meter,
PTW NOMEX Multimeter and by Monte Carlo Simulation was within tolerance limits.
Some organ sites (Cervix and Head and Neck) measurements are higher than the DRL values mentioned in NRPB.
Data Collection
The entrance surface dose measurement for various radiographic imaging procedures was carried out on 33 X-ray generating equipment.
A total of 4835 patient examinations were evaluated in the present study.
Supplementary data to support the patient dose surveys for establishing DRL were also collected.
It includes manufacturer and type of equipment ,
detector system (Screen/film,
including speed class ,
Computed Radiography ,
Digital radiography-type of detector ),
Focus to Film distance (FFD) , Added filtration,
Grid (used/not used/not removable),
Exposure parameters used kV,
mA,
mAs,
Automatic exposure control (AEC) (activated/ deactivated) etc.
Data Evaluation
As per the international guidelines,
local DRL (LDRL) is based on the 3rd quartile (the 75th percentile) value of the distribution of patient doses obtained from radiology departments in a single large healthcare facility or a group of healthcare facilities,
for a defined clinical imaging task (i.e.,
common indication based protocol) surveyed for standardized patient groupings.
If a large group of healthcare facilities is involved,
it would be appropriate to use the 75th percentile of the distribution of median values obtained from the facilities,
but if just a small group (2-4) of healthcare facilities are involved or one large healthcare facility,
then it would be appropriate to use the 75th percentile value of the patient dose distribution (pooled distribution).
The 75th percentile has been chosen to be consistent with the definition of National DRLs.
The 50th percentile value of patient dose distributions obtained from each radiology department should regularly be compared with LDRLs.
The 3rd quartile (the 75th percentile) value of the distribution of patient doses obtained for various sites of examination is tabulated and compared with the international reference guideline and other national DRLs.