Introduction
Quality Assurance ( QA ) activities include a planned system of reappraisal processs conducted by forces non straight involved in the stock list compilation/development procedure. Reviews, sooner by independent 3rd parties, should be performed upon a finalized stock list following the execution of QC processs. Reviews verify that information quality aims were met, guarantee that the stock list represents the best possible estimations of emanations and sinks given the current province of scientific cognition and information available, and back up the effectivity of the QC plan.
QAP ( Quality Assurance Program ) in mammography is critical because mammography is technically one of the most demanding radiological probe and systematically high quality mammograms are indispensable. Poor quality mammogram will take to misidentify diagnosing and increased figure of inappropriate biopsies.
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QAP in mammography is a combined attempt by all staff to guarantee that every facets of their work are directed towards the accomplishment of high quality public presentation. It can be expressed as the care of criterions and continual chase of excellence.
Considerations on a QA plan based on the chosen parametric quantities are made. It is because x-ray scrutinies of chest must be performed with high quality images and the lowest captive dosage. In film-screen mammography several physical and proficient parametric quantities contribute to the diagnostic consequences. A full optimisation, which considers the entire figure of parametric quantities that can be varied, is non realistic. A treatment on the comparative importance of the individual parametric quantities is made to supply assurance that their optimisation will fulfill demands of good diagnostic consequences with minimal dosage.
The purpose of QA harmonizing to European EPMS is to guarantee:
– The radiotherapist is provided with images that have the best possible diagnostic information obtainable when the appropriate radiographic technique is employed.
– The image quality is stable with regard to information content and average optical denseness.
– The chest dosage is “as low as moderately achievable” for the diagnostic information required.
The success of mammography, whether for testing or diagnosing depends on bringing of high-quality, low-dose images. To make this end, QC begins with specification and purchase of mammography equipments that meet the credence criterion of public presentation. After credence, the public presentation of all equipment constituents must be maintained at the higher degree possible, at least above the minimal degree.
Abstraction
There are 3 trials has been done to find the efficiency of the mammography unit in HUSM. First, the half-value bed measuring. In this trial, the half value bed ( HVL ) when aluminium is irradiated with x-ray beam of 45 ma for wide focal size and 56 ma for little focal size is about 0.5 millimeters Al at the same 28 kilovolt with Mo mark and Mo filter.
The exposure is half of initial value when x-ray beam base on balls through 0.5 millimeters Al sheet. The HVL obtained is more than 0.28 millimeter of Al at 28 kVp shows that the value is equal to minimise dosage to patient. As the value of concluding exposure without aluminium for both little and wide focal topographic point size is below than 2 % from the first exposure without aluminium, no repeat is required for this trial.
2nd trial was done to find the image quality produced by utilizing ACR-RMI 156 Phantom is within the standard harmonizing to the local governments and to supervise the alterations of the system public presentation from clip to clip.
Several consequences were obtained to measure the mammography unit public presentation. Number of object at the apparition image was studied to find the either there is production of artefacts or non. Here, the figure of objects in each image for both wide and little focal topographic point is 4 largest fibres, 3 largest pinpoints group and three 3 multitudes. This consequence obtained is more than the minimal figure of objects required by standard image.
The mark for the RMI 156 after summing up of each object for the whole survey with artifact decrease is 10 for both wide and little focal size where the minimal mark required is ? 10. Therefore, the machine has passed the trial. For the specific bunch survey, entire mark required for the trial is ? 21. In this trial, the consequence obtained for both wide and little focal topographic point is 24. So, the machine has passed the trial.
The optical denseness of the movie in the centre of the phantom image at 28 kVp is 0.63 for wide focal topographic point size and 0.56 for little focal topographic point size. But, the scope required to go through the trial is within 1.10 to 1.50 and should non alter by more than ± 0.20. Because of that, it failed the trial and some accommodation must be done to maintain the machine in good status. The denseness difference for wide focal topographic point size is 0.23 and 0.15 for little focal topographic point size. For runing optical denseness degree, the 4.0 millimeters acrylic phonograph record is maintain at the value suggested ( 0.40 ± 0.05 ) when the movie is exposed at 28 kVp.
Last, the AEC duplicability and denseness control map trial has besides been done to measure the public presentation of the AEC system to bring forth the uniformity of the X raies with respects to the end product duplicability measuring and to besides to look into the efficiency of the denseness alterations on the mammography movie relation to the end product strength discrepancy as a consequence of difference choice on the denseness accountant.
After the trial has been done, CV value for both mas and optical denseness ( OD ) are determined. Since all the CV value are less than the needed value, 0.05 it is concluded that the machine is still in good status.
For a normal operation system, each denseness control measure alteration should ensue in a 12 – 15 % alteration in ma and about 1.0 to 1.5 alterations in OD. For this trial, comparative ma of denseness +1 for both little and wide FSS is in recognized value but comparative ma of denseness -1 for both little and wide FSS is non acceptable. For comparative OD, about all mean denseness for little and wide FSS is acceptable and can be used.
A. HALF VALUE LAYER MEASUREMENT
Introduction
The thickness of any given stuff where 50 % of the incident energy has been attenuated is known as the half-value bed ( HVL ) . The HVL is expressed in units of distance ( millimeter or centimeter ) . Like the fading coefficient, it is photon energy dependant. Increasing the perforating energy of a watercourse of photons will ensue in an addition in stuff ‘s HVL. The HVL is reciprocally relative to the fading coefficient. If an incident energy of 1 and a familial energy is 0.5 is plugged into the equation introduced on the preceding page, it can be seen that the HVL multiplied by m must be 0.693.
Aim:
To guarantee that the half value bed of the x-ray beam is equal to minimise patient chest dosage and non overly degrade the contrast of the attendant image.
Test Frequency:
Acceptance Testing
Annually
Equipment:
1. Ionization chamber ( Victoreen Model 07-430 )
2. Aluminum HVL attenuator set
3. Mammography exposure metre ( Nuclear Associates Model 600-526 Rad-Check Plus ) .
Procedure:
1. The chest compaction paddle is placed every bit near as possible to the x-ray tubing.
2. The ionisation chamber is placed about 5 centimeters above the image receptor centered left to compensate and 4 centimeter from the chest wall border of the image receptor.
3. The ionisation chamber is within the x-ray field.
4. The kVp is selected at which the system is usually used clinically and it is recorded. ( 28kVp )
5. The unit is set to sufficient ma ( around 40-50 ma ) to supply an exposure of about 500mR.
6. An exposure without any aluminium between x-ray tubing and ionisation chamber is made. Ionization chamber is ensured in to the full exposed and the reading is recorded.
7. 0.2 mm midst aluminium is added between the x-ray tubing and the ionisation chamber, placed on top of the compaction paddle.
8. The light field is used to verify that the x-ray way to the ionisation chamber is to the full blocked by the aluminium sheet. An exposure is made and the reading is recorded.
9. The above measure is repeated with extra of 0.1 millimeters thick aluminium, until the recorded reading is one half less than the exposure without any attenuators
10. All aluminium sheets is removed from the top of the compaction paddle and a concluding exposure is made and recorded. The trial is repeated once more following the above sequence if the consequence of the reading differs by more than 2 % from the original first exposure.
11. This trial is done on both BROAD and FINE FOCAL SPOT.
12. The ionisation chamber reading ( Mister ) versus the thickness of the aluminium attenuators ( mm Al ) is plotted on a graph paper.
Reading:
Focal Spot Size: Broad
Target: Molybdenum
Filter: Molybdenum
Initial exposure reading without added aluminium:
kilovolt
ma
Exposure ( Mister )
28
40
444
28
45
503
Table 1: Initial exposure reading
Exposure reading with added aluminium ( ma: 45 )
Thickness of HVL ( millimeter )
Exposure ( Mister )
0.1
433
0.2
366
0.3
323
0.4
281
0.5
251
Table 2: Exposure measuring when ionisation chamber is to the full blocked with aluminium in peculiar thickness.
Concluding exposure consequence without added aluminium:
kilovolt
ma
Exposure ( Mister )
28
45
504
Table 3: Concluding exposure reading after aluminium is removed
Focal Spot Size: Small
Target: Molybdenum
Filter: Molybdenum
Initial exposure reading without added aluminium:
kilovolt
ma
Exposure ( Mister )
28
45
396
28
50
443
28
56
491
28
63
554
Table 4: Initial exposure consequence
Exposure reading with added aluminium ( ma: 56 )
Thickness of HVL ( millimeter )
Exposure ( Mister )
0.1
426
0.2
389
0.3
321
0.4
282
0.5
243
Table 5: Exposure measuring when ionisation chamber is to the full blocked with aluminium in peculiar thickness
Concluding exposure consequence without added aluminium
Kv
ma
Exposure ( Mister )
28
56
491
Table 6: Concluding exposure reading after aluminium is removed
Consequence:
* For Broad Focal:
HVL = 0.1 millimeter x 5
= 0.5 millimeter
As the credence bound of HVL ? kVp ( in units of millimeter Al )
100
? 28 millimeters Al
100
? 0.28 millimeters Al
Hence, the HVL of 0.5 millimeter Al is accepted
% Different of first and concluding exposure = ( 504 – 503 ) x 100
504
= 0.2 %
* For Small Focal:
HVL = 0.1 millimeter x 5
= 0.5 millimeter
As the credence bound of HVL ? kVp ( in units of millimeter Al )
100
? 28 millimeters Al
100
? 0.28 millimeters Al
Hence, the HVL of 0.5 millimeter Al is accepted
% Different of first and concluding exposure = ( 491 – 491 ) x 100
491
= 0 %
Discussion:
The half value bed ( HVL ) when aluminium is irradiated with x-ray beam of 45 ma for Broad focal size and 56 ma for Small focal size is about 0.5 millimeters Al at the same 28 kilovolt with Mo mark and Mo filter. The exposure is half of initial value when x-ray beam base on balls through 0.5 millimeters Al sheet. The HVL obtained is more than 0.28 millimeter of Al at 28 kVp shows that the value is equal to minimise dosage to patient.
For mammography less than 50 kVp,
HVL ? kVp ( in units of millimeter Al )
100
But, if HVL for screen-film units is inordinate, both capable contrast and image contrast will be reduced. ACT 304 recommended that the HVL be near the lower limit acceptable HVL.
HVL ? kVp + 0.1 ( mm Al )
100
The value of concluding exposure without aluminium for both little and wide focal topographic point size is below than 2 % from the first exposure without aluminium. So, no repeat is required for this trial.
Decision:
The HVL of the X ray for this mammogram machine is equal to minimise the dosage at patient chest. But, inordinate in these value will do contrast decrease of attendant image. Hence, the service forces should look into the unit to guarantee that X ray has an appropriate filtration.
B. IMAGE QUALITY USING ACR-RMI 156 PHANTOM
Introduction
The image quality was assessed over the scope of Kilovoltage puting available and for all target/filter combination available. The appraisal is carried out by numbering figure of artefact in the image produced by exposing the movie with apparition. The concluding consequence show that the movie is safe to utilize since the numeration is within the safe bound.
Aim:
1. The appraisal is done to find the image quality produced within the standard harmonizing to the ordinance of the local governments.
2. To supervise the alterations of the system public presentation from clip to clip.
Test Frequency:
Monthly
Equipment:
1. Mammographic apparition RMI 156 or tantamount harmonizing to the Mammography Accreditation Program.
2. RMI 156 ( Nuclear associates 18-220 ) specification:
– 4.2 centimeter thickness compressed breast tissue equivalent
– 50 % glandular and adipose tissue mimics
– Fibers diameter: 1.56, 1.12, 0.89, 0.75, 0.54 and 0.40 millimeter
– Speck diameter: 0.54, 0.40, 0.32, 0.24 and 0.16 millimeter
– Multitudes diameter: 2.0, 1.0, 0.75, 0.50 and 0.25 millimeter
3. Acrylic phonograph record ( 4mm midst, 1 centimeter diameter )
4. Mammography cassette and movie.
5. Magnifying glass
6. Film mask
7. densitometer
Procedure:
1. The acrylic phonograph record is topographic point in a consistent country of the RMI 156 apparition such as along cardinal axis between anode and cathode. The disc arrangement should n’t be compromised with the shadow casting of AEC sensor and must non befog the inside informations of the apparition
2. Imaging home base ( IP ) is placed on the IP holder with the chest wall border of the apparition aligned with the chest side of the image receptor.
3. The compaction paddle is lowered until it is merely in contact with the top of the apparition.
4. The phototimer sensor is made certain located beneath the centre of the apparition. The same location is maintained for subsequent image quality rating cheques.
5. The kVp and denseness control puting used clinically for a chest of thickness and denseness corresponding to the apparition is selected, that is presently in used for 4.2 centimeters compressed chest thickness to acquire the mean denseness.
6. Both the BROAD and FINE focal point is tested with AEC manner exposed and all technique factors is recorded on the informations signifier.
7. The movie is processed and the cardinal background optical denseness on the movie is measured. This reading is recorded as the background optical denseness on the informations signifier.
8. The optical denseness of the movie inside the phonograph record and merely outside the phonograph record left or right ( perpendicular to the anode-cathode axis ) is measured. The differences as the denseness difference is recorded on the informations signifier ( average RMI background – acrylic denseness ) . The movie denseness is recorded with densitometer in three different locations:
9. Under optimum status, read apparition images with magnifying.
10. Each object is count harmonizing to the group get downing from the largest to the smallest.
11. The fibre:
– Measure the fibre as 1 point if the fibre image appears in a full size and in the right orientation.
– The point is 0.5 if the fibre length is more than half.
– All the points are added to hold the entire fibre mark before artifact tax write-off.
– The overall country is checked for fiber-like artefact in the wax insert country of the image.
– Each located artefact is deducted 0.5 from the last existent fibre if there is any. The concluding mark is recorded.
12. The pinpoint:
– The pinpoints are get downing numbering from largest group. The group is count as 1 point if 4 or more out of the 6 pinpoints in the group are seeable within the proper location.
– The group is count as 0.5 point if there are 2 or 3 pinpoints that are visualized.
– All points is added to hold the entire mark ( the altogether ) of the pinpoints group before artifact tax write-off.
– The speck-like artefact is checked from the overall background. 1 point is deducted from the entire mark of the pinpoints if the noise or speck-like artefact seemingly seeable into the country of the wax insert.
13. The mass:
– Each mass is count as 1 point if the denseness country appears by and large round against the background about ? of the margin and within the right location.
– The mass is count as 0.5 point if the denseness country visualized in the right location but does non hold round visual aspect.
– Check the overall background to happen the mass-like artefact after holding the entire mass. The last existent whole mass is deducted if a mass-like artefact is seen in a incorrect location within the wax insert or half of the mass mark if the mass go every bit or more evident.
Reading and computation:
Thickness: 35mm
Pressure: 20 Newton
Field size: 13 tens 18
Magnification factor: 1.0
Focal size
Target
Filter
Contrast
kilovolt
ma
Large
Moment
Moment
+0
28
64
Small
Moment
Rhesus factor
+0
28
88
Table 7: Relative kilovolt and ma for Broad and Small Focal Spot Size
* Focal Spot Size: Broad
Background
Reading
Quadrant
1
2
3
4
Average
1
0.61
0.60
0.60
0.60
0.60
2
0.62
0.62
0.60
0.63
0.62
3
0.63
0.63
0.63
0.63
0.63
4
0.66
0.66
0.65
0.66
0.66
Table 8: Optical denseness of four quarter-circles
Acrylic
Reading
1
2
3
4
Average
Value
0.43
0.38
0.38
0.39
0.40
Table 9: Optical denseness of acrylic phonograph record
Average optical denseness for Broad FSS = 0.60 + 0.62 + 0.63 + 0.66
4
= 0.63
Density difference = Average OD of Broad FSS – Average OD of acrylic phonograph record
= 0.63 – 0.40
= 0.23
* Focal Spot Size: Small
Background
Reading
Quadrant
1
2
3
4
Average
1
0.48
0.49
0.47
0.50
0.49
2
0.49
0.51
0.52
0.46
0.50
3
0.61
0.61
0.60
0.62
0.63
4
0.64
0.62
0.63
0.62
0.63
Table 10: Optical denseness of four quarter-circle
Acrylic
Reading
1
2
3
4
Average
Value
0.41
0.40
0.40
0.44
0.41
Table 11: Optical denseness of acrylic phonograph record
Average optical denseness for Small FSS = 0.49 + 0.50 + 0.61 + 0.63
4
= 0.56
Density difference = Average OD of Small FSS – Average OD of acrylic phonograph record
= 0.56 – 0.41
= 0.15
Image Quality
Method 1:
Count by object, must be at least 10 objects
Fibers: 3/4
Specks: 3/6
Mass: 4/4
Objects
Focal Size
Fiber
Speck
Mass
Entire
Broad
4
3
4
11
Small
4
3
4
11
Table 12: Number of test objects of each type that is seeable in phantom image for wide
and little focal topographic point size
Method 2:
Object Size
Objects
Focal Size
Fiber
Speck
Mass
Entire
Broad
4
3
4
11
Small
4
3
4
11
Table 12: Number of test objects of each type that is seeable in phantom image for wide
and little focal topographic point size
Artifacts
Objects
Focal Size
Fiber
Speck
Mass
Entire
Broad
0
2 ten 0.5 = 1.0
0
1
Small
0
2 ten 0.5 = 1.0
0
1
Table 13: Number of artefacts found in both wide and little focal topographic point size image which
calculated by 2nd method
Objects
Focal Size
Entire Object Size
Broad
11 – 1 = 10
Small
11 – 1 = 10
Table 13: Number of objects of each type that is seeable in phantom image for wide and
little focal topographic point size after being deducted by the seeable artefacts
Method 3:
Entire Structure
Objects
Focal Size
Fiber
Speck
Mass
Entire
Broad
4
3 ten 6 = 18
4
26
Small
4
3 ten 6 = 18
4
26
Table 14: Number of entire construction that is seeable in phantom image for wide and little
focal topographic point size
Objects
Focal Size
Fiber
Speck
Mass
Entire
Broad
0
2
0
2
Small
0
2
0
2
Table 15: Number of entire artifact constructions that visible in phantom image for wide and
little focal topographic point size
Objects
Focal Size
Entire Structure
Broad
26 – 2 = 24
Small
26 – 2 = 24
Table 16: Number of entire constructions that is seeable in phantom image for wide and little
focal topographic point size after being deducted by entire construction of seeable artefacts
Discussion:
1 ) The figure of objects in each image for both wide and little focal topographic point is 4 largest fibres, 3 largest pinpoints group and three 3 multitudes. This consequence obtained is more than the minimal figure of objects required
2 ) The mark for the RMI 156 after summing up of each object for the whole survey with artifact decrease is 10 for both wide and little focal size where the minimal mark required is ? 10. Therefore, the machine has passed the trial.
3 ) For the specific bunch survey, entire mark required for the trial is ? 21. In this trial, the consequence obtained for both wide and little focal topographic point is 24. So, the machine has passed the trial.
4 ) The optical denseness of the movie in the centre of the phantom image at 28 kVp is 0.63 for wide focal topographic point size and 0.56 for little focal topographic point size. But, the scope required to go through the trial is within 1.10 to 1.50 and should non alter by more than ± 0.20. Because of that, it failed the trial and some accommodation must be done to maintain the machine in good status.
5 ) The denseness difference for wide focal topographic point size is 0.23 and 0.15 for little focal topographic point size
6 ) The operating optical denseness degree for 4.0 millimeters acrylic phonograph record is maintain at the value suggested ( 0.40 ± 0.05 ) for movie exposed at 28 kVp.
Decision:
The machine is still in its good status since it has passed most of the trial done. However, the artefacts were clearly discernible in the image and some accommodation must be done to better the public presentation particularly for the trial that the machine has been failed. This is of import to guarantee that the image green goods are in high quality and cut down the opportunities of misinterpreting the diagnostic images obtained.
C. AEC REPRODUCIBILITY AND DENSITY CONTROL FUNCTION
Aim:
1. To measure the public presentation of the AEC system to bring forth the uniformity of the x-ray with respects to the end product duplicability measuring.
2. To look into the end product strength discrepancy as a consequence of difference choice on the denseness accountant. Test Frequency:
Acceptance proving
Semi-annually
Equipment:
1. A Perspex apparition 2.3 centimeter midst slabs ( x2 ) to supply 4.6 cm additive dimensions.
2. Densitometer.
Procedure:
I ) Output Reproducibility
1. The mammographic imagination system is set for operation in the AEC manner with “normal” denseness control scene.
2. The AEC detector is selected closest to the chest wall.
3. The kilovolt, ( FINE and BROAD ) focal topographic point, and tube current ( ma ) routinely used for the selected imagination manner is selected.
4. That factor is recorded as mention.
5. To bring forth a series of four images utilizing the same IP, these process above is repeated three times.
6. The movie is divided into equal quarter-circles after each exposure and movie processed and the optical denseness at each location is measured.
7. Extra optical denseness at the centre of the Perspex image is measured and recorded on the informations signifier.
8. The average values and standard divergences for each denseness ( 0, +1 and -1 ) are calculated from the measured ma and OD.
9. 0.05 is the maximal acceptable coefficient of fluctuation ( CV ) for both mas and OD.
two ) Density Control Function
1. The AEC duplicability process from stairss 1 through 9 is followed.
2. Step 1 is repeated for each other available scene of the AEC system ‘s denseness control picker ( 0, +1 and -10 for FINE and BROAD focal point.
3. The optical denseness at the Centre of the Perspex image on the processed movie is measured and recorded on the information.
4. The comparative ma ( ratio of ma to that at the “normal” scene ) and comparative OD ( difference between the OD and the OD at the “normal” scene ) is calculated.
5. The trial consequence, technique factors used in each subdivision of the trial is recorded immediately during the process.
6. Each denseness control measure alteration for a usually functioning system should ensue in a 12 – 15 % alteration in ma and about 1.0 to 1.5 alterations in OD.
Reading and consequence:
Thickness: 39 millimeter
Pressure: 20 Newton
Field size: 13 tens 18
Magnification factor: 1.0
U1
U2
L1
L2
U1: Left Upper Quadrant U2: Right Upper Quadrant
L1: Left Upper Quadrant L2: Right Lower Quadrant
* Focal Spot Size: Broad
1 ) Density: -1
Reading
Quadrant
1
2
3
4
Average OD
Std. Dev
Curriculum vitae
U1
0.67
0.63
0.67
0.69
0.67
0.029
0.040
U2
0.66
0.69
0.74
0.73
0.71
0.006
0.008
L1
0.72
0.75
0.74
0.76
0.74
0.012
0.017
L2
0.77
0.75
0.76
0.76
0.74
0.012
0.017
Table 17: Optical denseness reading, Standard divergence and CV value
Target
Filter
kilovolt
ma
Std. Dev
Curriculum vitae
Moment
Moment
28
122
0
0
Table 18: Standard divergence and CV value
Average OD = 0.67 + 0.71 + 0.74 + 0.74
4
= 0.72
Average CV for OD = 0.040 + 0.008 + 0.017 + 0.017
4
= 0.021
2 ) Density: 0
Reading
Quadrant
1
2
3
4
Average OD
Std. Dev
Curriculum vitae
U1
0.74
0.71
0.73
0.73
0.73
0.006
0.008
U2
0.72
0.76
0.74
0.75
0.74
0.012
0.017
L1
0.67
0.69
0.70
0.70
0.69
0.017
0.024
L2
0.72
0.68
0.76
0.73
0.72
0
0
Table 19: Optical denseness reading, Standard divergence and CV value
Target
Filter
kilovolt
ma
Std. Dev
Curriculum vitae
Moment
Moment
28
120
0
0
Moment
Moment
28
121
0.707
0.006
Moment
Moment
28
120
0
0
Table 20: Standard divergence and CV value
Average OD = 0.73 + 0.74 + 0.69 + 0.73
4
= 0.72
Average CV for OD = 0.008 + 0.017 + 0.024 + 0
4
= 0.012
Average ma = 120 + 121 + 120
3
= 120
3 ) Density: +1
Reading
Quadrant
1
2
3
4
Average OD
Std. Dev
Curriculum vitae
U1
0.73
0.76
0.73
0.75
0.74
0.006
0.008
U2
0.74
0.79
0.75
0.75
0.76
0.017
0.023
L1
0.71
0.71
0.74
0.69
0.71
0.012
0.016
L2
0.73
0.74
0.69
0.73
0.72
0.006
0.008
Table 21: Optical denseness reading, Standard divergence and CV value
Target
Filter
kilovolt
ma
Std. Dev
Curriculum vitae
Moment
Moment
28
138
0.707
0.005
Moment
Moment
28
137
0
0
Moment
Moment
28
137
0
0
Table 22: Standard divergence and CV value
Average OD = 0.74 + 0.76 + 0.71 + 0.72
4
= 0.73
Average CV for OD = 0.008 + 0.023 + 0.016 + 0.008
4
= 0.014
Average ma = 138 + 137 + 137
3
= 137
* Focal Spot Size: Small
1 ) Density: -1
Reading
Quadrant
1
2
3
4
Average OD
Std. Dev
Curriculum vitae
U1
0.65
0.63
0.67
0.66
0.65
0.035
0.049
U2
0.65
0.69
0.69
0.74
0.69
0.012
0.017
L1
0.72
0.74
0.74
0.75
0.74
0.017
0.024
L2
0.77
0.75
0.78
0.76
0.77
0.035
0.049
Table 23: Optical denseness reading, Standard divergence and CV value
Target
Filter
kilovolt
ma
Std. Dev
Curriculum vitae
Moment
Moment
28
218
0
0
Table 24: Standard divergence and CV
Average OD = 0.65 + 0.69 + 0.74 + 0.77
4
= 0.71
Average CV for OD = 0.049 + 0.017 + 0.024 + 0.049
4
= 0.035
2 ) Density: 0
Reading
Quadrant
1
2
3
4
Average OD
Std. Dev
Curriculum vitae
U1
0.67
0.63
0.67
0.69
0.67
0.029
0.040
U2
0.66
0.69
0.74
0.73
0.71
0.006
0.008
L1
0.72
0.75
0.74
0.76
0.74
0.012
0.017
L2
0.77
0.75
0.76
0.76
0.74
0.012
0.017
Table 25: Optical denseness reading, Standard divergence and CV value
Target
Filter
kilovolt
ma
Std. Dev
Curriculum vitae
Moment
Moment
28
214
0.707
0.003
Moment
Moment
28
212
0.707
0.003
Moment
Moment
28
212
0.707
0.003
Table 26: Standard divergence and CV
Average OD = 0.67 + 0.71 + 0.74 + 0.74
4
= 0.72
Average CV for OD = 0.040 + 0.008 + 0.017 + 0.017
4
= 0.021
Average ma = 214 + 212 + 212
3
= 213
3 ) Density: +1
Reading
Quadrant
1
2
3
4
Average OD
Std. Dev
Curriculum vitae
U1
0.68
0.64
0.68
0.70
0.67
0.029
0.040
U2
0.70
0.70
0.65
0.73
0.70
0.012
0.017
L1
0.72
0.73
0.70
0.73
0.72
0
0
L2
0.80
0.74
0.79
0.76
0.77
0.029
0.040
Table 27: Optical denseness reading, Standard divergence and CV value
Target
Filter
Kv
ma
Std. Dev
Curriculum vitae
Moment
Moment
28
244
0
0
Table 28: Standard divergence and CV
Average OD = 0.67 + 0.70 + 0.72 + 0.77
4
= 0.72
Average CV for OD = 0.040 + 0.017 + 0 + 0.040
4
= 0.025
Calculation of comparative ma and comparative Doctor of optometry:
Relative ma for A, denseness
= Exp ( A ) – Exp ( 0 ) x 100 %
Exp ( 0 )
Focal Spot Size
Density
ma
Relative ma
Small
+1
244
14.55
-1
218
2.35
138
15.00
Broad
+1
137
14.17
137
14.17
-1
122
1.67
Relative OD for A, denseness
Focal Spot Size
Density
ma
Relative ma
0.67
0.93
+1
0.70
0.97
0.72
1.00
Small
0.77
1.07
0.65
1.90
-1
0.69
1.07
0.74
1.03
0.77
1.07
Focal Spot Size
Density
ma
Relative ma
0.74
1.03
+1
0.76
1.06
0.71
0.99
Broad
0.72
1.00
0.67
0.93
-1
0.71
0.99
0.74
1.03
0.74
1.03
Discussion:
1. Standard divergence ( SD ) is obtained by utilizing mathematical computation:
SD = v ( value – mean ) 2
n – 1
2. The coefficient of fluctuation ( CV ) for both mas and OD in acceptable scope less than 0.05
3. For a normal operation system, each denseness control measure alteration should ensue in a 12 – 15 % alteration in ma and about 1.0 to 1.5 alterations in OD. For this trial, comparative ma of denseness +1 for both little and wide FSS is in recognized value but comparative ma of denseness -1 for both little and wide FSS is non acceptable. For comparative OD, about all mean denseness for little and wide FSS is acceptable and can be used.
Decision:
The public presentation of AEC system is fulfilling and bring forthing x-ray uniformly. If the consequence is exceeded, the unit should be checked by the service personal in order to keep the efficiency of the system.
