This document discusses the establishment of Local Dose Reference Levels (LDRLs) for common radiology examinations at Nicosia General Hospital in Cyprus. The LDRLs were originally established in 2008 based on measurements of Dose Area Product and Entrance Surface Dose for four digital radiography systems. Four protocols (Chest PA, Lumbar Spine AP/Lat, Abdomen AP) were re-evaluated based on measurements from 10 patients weighing 70±10 kg. The original LDRLs were also compared to UK national reference levels. Image quality was evaluated by radiologists according to European criteria. Revised LDRLs showing improved entrance surface doses were established based on a compromise between lower dose and highest image quality

1. Establishment of the Local Dose Reference Levels for
Direct Digital Radiology protocols at the
Nicosia General Hospital
Stelios Christofides1, Georgiana Kokona1, Constantinos Demetroullas2,
Omiros Omirou2, Nicoletta Nicolaou3
1. Medical Physics Department - Nicosia General hospital
2. Radiology Department – Arch. Makarios III Hospital
3. Physics Department, University of Cyprus, Nicosia, Cyprus.
4. School of Physics and Astronomy, University of Birmingham, U.K.
1. INTRODUCTION
Local Dose Reference Levels (LDRLs) of Nicosia General Hospital (NGH) were established in
2008 from four Direct Digital Radiography Systems MECALL EIDOS 3000 nine most common
examination protocols. Recently an effort is being made to optimise these protocols. So far
four of these have been optimized taking into account the weight of the patients and LDRLs
have been revised. Evaluation of the above protocols carried out from radiologists according
the EUR 162601.
2. MATERIALS AND METHODS
The original LDRLs have been established based on Dose Area Product (DAP) and Entrance
Surface Dose (ESD) measurements. DAP values of randomly selected patients were retrieved
from the Picture Archiving and Communications System (PACS). ESD measurements were
derived from the X-ray tube output measurements and X-ray exposure measurements for
each radiology system2.
Four protocols (Chest PA, Lumbar Spine AP, Lumbar Spine Lat, and Abdomen AP) were
chosen and data were collected from 10 patients weighted in the range of the 70 ± 10 kg3.
The ESD doses were derived following the aforementioned procedure. At the same time for
each measurement DAPs readings was also recorded.
Examination protocols established in the previous stage (Chest PA, Lumbar Spine AP, Pelvis)
were evaluated and optimized following the below procedure. ESD and DAP measurements
were assessed for the above protocols after small changes at the tube voltage (±10 kV with
±5kV pace). The images of three protocols were chosen and two radiologists evaluated
them by scoring them according to the EUR 16260.The scoring criteria were divided in three
groups relating the image quality with the tube output, the good positioning and the
preparation of the patient. The best protocols were chosen after a compromise between
lower doses and highest scored quality criteria.
3.ESTABLISHMENT OF LOCAL DRLS
Table 1: NGH LDRLs compared to the UK NDRLs. Patients were selected randomly
4. IMAGE EVALUATION
Table 2: Revised NGH LDRLs compared to the original LDRLs. Patients were
selected in the range of the 70 ± 10 kg
6. REFERENCES
1. CEC. European Guidelines on Quality Criteria for Diagnostic Radiographic Images. Report
EUR 16260EN. Office for Official Publication of the European Community (1996)
2. Wall, B. (eds), European Guidance on Estimating Population Doses from Medical X-Ray
Procedures, Radiation Protection No 154, European Commission 2008.
3. International Commission for Radiation Units and Measurements (ICRU) (1998). Patient
dosimetry for x-rays used in medical imaging. J ICRU 2005; 5: iv–vi, Petoussi-Henss et al.
4. Hart, D. & Hillier, M. & Wall, B. (2002), Doses to patients from medical X-ray
examinations in the UK- 2000 review, NRPB-W4.
5. Irish X-ray departments demonstrate varying levels of adherence to European guidelines
on good radiographic technique. The British Journal of Radiology, 75 (2002).
5. CONCLUSIONS
The original established NGH ESD LDRLs were lower as the weight of the patients was taken
into account. It was revealed that radiographers after the acquisition of the image are often
trimming it to the correct area electronically and therefore the NGH DAP LDRLs (original and
revised) are not reliable5.
In order to establish effectively LDRLs and NDRLs it is necessary to consider the weight of
the patient and educate the radiographers to adhere to the correct positioning of the
patient.
In implementing EUR 16260 it was observed that poor quality image was strongly related
with inadequate patient positioning, and preparation. In addition doctors should further
familiarize themselves with evaluation criteria. It is recommended that this study be
extended to greater scale for reliability and that relevant training programs must be initiated
to all radiology staff.
Examination
Prorocol
ESD (mGy) DAP (mGy.cm2)
NGH LDRs UK NDRLs NGH LDRLs UK NDRLs
Skull AP 2.78 3.00 795.21 N/A
Skull Lat 1.71 1.50 693.48 N/A
Cervical AP 1.17 N/A 226.31 400.00
Cervical Lat 1.17 N/A 157.27 400.00
Chest PA 0.39 0.20 124.84 120.00
Lumbar Spine AP 4.00 6.00 2228.36 1600.00
Lumbar Spine Lat 10.49 14.00 3715.17 3000.00
Abdomen AP 4.50 6.00 3126.08 3000.00
Pelvis AP 3.83 4.00 2714.73 3000.00
Table 1 compares the NGH LDRLs that were established in 2008 with the UK National
DRLs4. This comparison indicates that the ESD NGH LDRLs are lower that those of the UK
NDRLs except for the Chest PA protocol. Contrarily, most of the NGH DAP LDRLs are
substantially higher than the UK NDRLs.
Examination
Prorocol
ESD (mGy) DAP (mGy.cm2)
Original Revised Original Revised
Chest PA 0.39 0.11 124.84 121,08
Lumbar Spine AP 4.00 4,96 2228.36 2121.61
Lumbar Spine Lat 10.49 8,49 3715.17 4399,66
Pelvis AP 3.83 3,59 2714.73 3583,61
Table 2 compares the revised NGH LDRLs with those originally established. It is
evident that most of the revised ESD LDRLs show improvement. This is not true for
the DAP LDRLs that do not show any improvement.
Doses were calculated for 10 patients weighted in the range of the 70 ± 10 kg for different
values of tube output for the below examination protocols. Two doctors evaluated the
image quality with different tube output values, good positioning and preparation of the
patient according to the EUR 16260. Table 3 summarizes only the tube output values that
give the best quality scoring . There is a strong correlation between good positioning and
preparation of the patient with poor image quality.
Table 4 presents the tube output values that result in the maximum dose minimization.
These protocols were chosen as the optimum protocol after the compromise between
lower doses and highest scored quality criteria.
Examination
Prorocol
Tube output-image quality
Good
positiong
Good
preparation
Tube voltage Scores (%) Dose(mGy) Scores(%) Scores(%)
Chest PA 115 99 0,04 77 N/A
Lumbar Spine AP 80 93 2,66 93 N/A
Pelvis AP 85 100 1,59 89,5 61
Examination
Prorocol
Before optimization After optimization
Difference
In
Dose
Tube voltage Dose(mGy) Tube voltage Dose(mGy) %
Chest PA 100 0,048 115 0,037 54
Lumbar Spine
AP
75 4,54 80 2,66 41
Pelvis AP 75 3,5 85 1,59 23
Table 4:Protocls that were chosen after the compromise between lower dose and highest quality scored
Table 3: Scores with best scored tube output value , good positioning and preparation of the patient