Assessment of AGD in UAE Hospital

Achieve consistently high quality mammograms. Limit radiation dose by determine the Average Glandular Dose (DG) resulting craniocaudal projections. IAEA guidance was used for measuring the Entrance Surface Air Kerma (Ka,e) and EUREF guidelines DG calculations. Minimize the number of supplementary and repeat examinations. Minimize the number of unnecessary invasive procedures. The main objective of this work was to evaluate the Average Glandular Dose (DG) resulting from exposure to mammographic X-rays while the ultimate aim of the project remains the establishment of Dose Reference Levels (DRL) in the UAE.


Introduction
X-ray mammography is the most reliable method of detecting breast cancer. It is the method of choice for the Breast Screening Program in a variety of developed countries In order to obtain high quality mammograms at an acceptable breast dose, it is essential to use the correct equipment.
In the United Arab Emirates (UAE), the number of mammography examinations has been rising steadily the past few years due to the rapid economic growth of the country and the increasing use of computed and digital radiography systems, as film based mammography systems are being abandoned progressively.
At present, there is a growing concern about the radiation doses incurred by patients when undergoing breast examinations. For this reason, the UAE has decided to join the IAEA Task4 project to undertake a survey of patient exposure in digital mammography in several Hospitals.

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Achieve consistently high quality mammograms. The main objective of this work was to evaluate the Average Glandular Dose (DG) resulting from exposure to mammographic X-rays while the ultimate aim of the project remains the establishment of Dose Reference Levels (DRL) in the UAE.
It is worth noting that the quantities and symbols used in this presentation are those suggested by the International Commission on radiation Units and Measurements (ICRU) in its publication 74.
The Total numbers of mammography system in Dubai are 26 facilities both in Governmental and Privet sector, the Average number of patients per year were 528, the number of CR system 18, the DR system 5 and the screen film 3.
There are some factors affecting the visibility of the objects:

Beam quality test (HVL)
Method: 1. Raise the compression paddle to its highest position. Mount the 6000-529 ionization chamber on a ring stand so there is approximately 5 cm of space between the bottom of the chamber and table. The chamber should be centered in the beam laterally, and approximately 4 cm from the chest wall. 2. Collimate the beam, using the light field, so that the entire chamber is included in the beam. The field should be approximately 6 cm x 6 cm. If necessary, relocate the chamber such that it is centered in the field. 3. Set the kVp selector at a kVp setting that is frequently used for making mammograms. 4. Connect the chamber to the Nero Max8000 device. 5. Make an exposure. Note the reading and label it X0. 6. Place a sheet of aluminum 0.2 mm thick on the compression paddle. Using the collimator light, be sure the entire ionization chamber is in the shadow of the aluminum sheet. Make an exposure. Record the reading and label it X1; also record the thickness of aluminum used to make the exposure. Label it t1. 7. Place an additional 0.01 mm of aluminum on top of the aluminum absorbers) already in place. Make an exposure. Record the reading, labeling it with sequential indices. Also, record the total thickness of aluminum used in making the measurement, labeling it as tN where N is the total number of filtered exposures taken so far. If XN is less than one half of X0 proceed to step 7, otherwise, repeat step 8. It is now assumed that you have compiled a list of data pairs, labeled "ti" and "Xi"-If N is the total number of filtered exposures, then the half-value layer may then be calculated using the following formula:

Image quality
For general image, we use the ACR mammography phantom contains test objects that are similar to microcalcifications, fibers, and masses -Image quality tests were performed at clinical settings to ensure that the X-ray machines were functioning properly, in accordance to the manufacturer's specifications. The image will represent the imaging abilities of your machine using these clinical factors.
-If the image is over or under exposed, make a suitable adjustment in your factors and repeat the exposure. -This is an indication that adjustments may be necessary for patient imaging of these compressed breast thicknesses and should be checked.
Use the ToRMAX-316 (Leeds Test Object) for Detailed Image (total thickness 7 cm) and repeat the pervious step for each breast thickness.
Image 1. ToRMAX-316 (Leeds Test Object). Image.2 Image 3. this image reflect the image that we got from the phantom after exposure.

Contrast-to-Noise Ratio (CNR)
- The Contrast-to-Noise Ratio (CNR) was determined by placing a square-shaped 2 cm x 2 cm piece of aluminum of thickness 0.2 mm on the PMMA phantom, 6 cm from the edge of the phantom and table, in the centre of the phantom. -Two ROIs of 4 cm2 were selected in the saved image to calculate the mean (S) and the standard deviation (σ).
The Contrast-to-Noise Ratio (CNR) is obtained using the equation:

Average Glandular Dose, DG
The AGD cannot be measured directly but it is derived from measurements with the standard phantom for the actual technique set-up of the mammographic equipment.
The measurements of the Entrance Surface Air Kerma Ka,e were performed in two steps, First 1. Set up the x-ray machine for a typical mammographic technique. Place a loaded cassette in the cassette holder, of the size and type consistent with the examination being simulated. Set the machine in the AEC mode and set the density control to the position most commonly used for the examination. 2. Place a mammographic LTO phantom on the cassette holder assembly at the position normally occupied by the breast. Be sure the phantom completely covers the AEC sensor.
3. The LTO phantom was exposed to X-ray beams using automatic mode to get the kVp, mAs, and target/filter combination used. 4. Then, remove the phantom and a similar exposure will perform in manual mode with no phantom. Note that the c and g-factors applied are those for the corresponding thickness of typical breast rather than the thickness of PMMA block used. Where necessary interpolation may be made for different values of HVL.
The dose should be determined using the usual clinically selected exposure factors including any automatic selection of kV and target/filter combination.   In our survey we use the limiting dose values to compare our date with it, as it will be shown in the next figures.

Discussion
The Results of the measured Average Glandular Dose (AGD) were performed on different breast thickness, we chose 2cm breast thickens, 4.5 cm breast thickens which simulate the standard breast thickens and the third thickens was 7 cm, so in our survey we were covered the small, medium and large breast thickness.
We inspected (21 facilities), and 4 of them have a DR mammography, 13 CR mammography and 3 screen film mammography.
www.intechopen.com    Hospital at 2cm BT), we observe from this figure that there are 3 hospitals were exceeding the AGD acceptable limit, which they are H6, H11&H13 with different anode\filter combination. H6: they are using the automatic mode, H11: they only have one Anode\Filter combination they use manual setting for Kv and automatic setting for mAs they were advice to change their setting to reduce the dose. H13: the technician were use the manual mode for acquiring their images , they were advised to fix call the service to fix their machine on the same time their cassette also were old and it was need to be changed. Regarding the other hospitals the most of them were fully automatic and the other have manual Kv settings. , shows that there was one hospital exceeding the acceptable dose limit (H2 Mo\Mo), the technician was use manual setting, they advise to call service to fix their machine. On the other hand we observe that (H7 Mo\Mo) have the lowest radiation dose to the patient, the technician were use manual setting for both KV & mAs. Fig. 6.((CR) AGD vs. Hospital at 7 cm BT),we observe that all hospital were below the AGD acceptable limit. As I explain before most of the hospital were using the manual settings for the Kv parameter. H7 Mo\Mo has the lowest radiation dose, the parameter that their use were so small Kv=27 & mAs= 50 the image quality was acceptable to their physician. , shows that all hospitals were below the AGD acceptable limit. All of these hospitals were using the manual setting for acquiring their images, their images were acceptable to their physician, for H3 the parameters used was Kv=28 & mAs=25.

Comparison between Calculated Average Glandular Dose (AGD) & System AGD
In most facilities, the difference between AGD values measured by the Physicist and those generated by the system were found acceptable, thus justifying a survey of patient doses on the basis of the AGD recorded by the system.   www.intechopen.com Fig. 11. the Contrast to Noise Ratio (CNR) -CR system.

Conclusion
This study on radiation exposure in mammography concerned number of facilities in Dubai region and will be extended to a larger number of facilities in the near future.
The results obtained show that quality control and patient Dosimetry are crucially needed in order to ensure a safe and efficient use of mammographic X-rays on patients whether for routine diagnosis or breast screening.
Also , we found that the value of the CNR is depend on the specification of the manufacture for each mammography machine , so we can't compare the value measured of the hospitals to each other because they are from different manufactures  Frequency: Acceptance, yearly and after tube or collimator repair/exchange.

Collimation assessment
Source to image receptor distance (SID) ----------cm Deviation between X-ray field and light field www.intechopen.com ACTION LIMIT: ACR/MQSA -If X-ray field exceeds image receptor at any side by more than 2% of SID or if X-ray field falls within image receptor on the chest wall side, seek service adjustment.
ACR -If X-ray field falls within image receptor by more than -2% on the left and right sides or by more than -4% on the anterior side, seek service adjustment.

Alignment of chest-wall edges of compression paddle and film
Difference between paddle edge and film Difference as % of SID ACTION LIMIT: ACR/MQSA -If chest-wall edge of compression paddle is within the image receptor or projects beyond the chest-wall edge of the image receptor by more than 1% of SID, seek service correction. www.intechopen.com