In quality assurance, we try to maintain the desired level of quality in an experiment, service or product, especially by means of attention to every stage of the process of delivery or production. We have determined this thing with the help of measurements of important factors of radiographic X-ray system like kVp, mA, and exposure time.
Kilovoltage affects both contrast and density. If it is too low, the resulting film will have a "soot and whitewash" appearance, i.e. high contrast. When the kilovoltage is too high, contrast will be reduced because the shorter wavelength. The kilovoltage potential (kVp) determines the quality of the x-ray beam and thus its ability to penetrate tissue. Higher kVp settings produce more penetrating beams, with a higher percentage of radiation reaching the film. A higher kVp setting allows for use of a lower mas setting. This would generally mean a short time of exposure. Gammex 330 is used for this purpose. The following graph shows that, at which levels should we maintain to achieve quality results. The inverse relation ship exists between kVp and mAs.
Milliamperage (ma) is a major factor in determining the quantity (dose) of x-rays produced. The mA-s Factor (time × milliamperes) affects film density by governing the amount of X-ray photons which reach the film emulsion. This, however only affects film contrast in a negative way, by reducing the contrast when the mA-s factor is incorrect. If the quantity of X-rays reaching the film is too low, the film will be pale. The relationship between ma and time is a direct one. Therefore, a higher ma setting allows for a corresponding decrease in required exposure time. The product of milliamperage and time is called milliamperseconds (mas); equal mas settings will produce radiographs of equal density or contrast. The following output graph can show us,
Exposure time is another most important considerations in determining whether an x-ray machine is adequate for examinations like Gammex 330. Exposure times of 0.1 sec or less generally ensure that the problem of motion during the exposure will be minimal. If the exposure times are longer than 0.1 sec, there will frequently be motion of the film holder, or tube. The range of available exposure times is great in Gammex and have settings of 0.3ms to 999s. Reviewing the relationship between ma and exposure time, it is obvious that a short exposure time can be obtained only in association with the utilization of a high milliamperage. Conversely, a machine with a low milliamperage (15-30 ma) must utilize exposure times of rather long duration (0.1-0.5 sec).
Key Methods " Numeracy
Radiography is a method of non-destructive testing where many types of manufactured components can be examined to verify the internal structure and integrity of the specimen. Radiography can be performed utilizing either X-rays or gamma rays. In radiography, the concept of radiation doze is the main thing. The amount of ionization produced in a given mass of matter is proportional to the amount of energy imparted by ionizing radiation in that mass. The amount of energy deposited per unit mass of matter can therefore be used to quantify radiation exposure and this quantity is called dose.
The Gammex 330 is used to analyze the essential parameters of X-ray system, their behavior according to calibrated outputs.
Vary
kVp
mA
sec
mA.s
Dose 1 uGy
Dose 2 uGy
Dose 3 uGy
Average
Std.Dev
Output
DAP/EI
Heat %
uGy
uGy
uGy/mAs
kVp
100
25
0.04
10
19.700
19.300
19.500
0.3
19.50
0.01
0
90
25
0.04
10
15.100
15.100
15.1000
15.100
0.00
15.10
0.03
1
70
25
0.04
10
8.300
8.300
8.300
0.00
8.30
0.07
2
50
25
0.04
10
3.100
3.100
3.100
0.0
3.10
0.02
2
mA
70
25
0.04
10
8.300
8.300
8.300
0.00
8.300
0.07
2
70
75
0.04
30
25.000
25.000
25.000
0.00
0.833
0.21
3
time
70
25
0.04
10
8.300
8.300
8.300
0.0
0.830
0.07
3
70
25
0.08
20
16.300
16.300
16.300
0.00
0.815
0.04
3
70
25
0.125
10
63.980
70
25
0.16
10
70.090
Integration
From experiments, it is obvious that the accuracy of the equipment is dependent on how you use it. Placing, cleaning, and handling are all related to managing an equipment. Similarly, from clinical prospective, a patient management is as important as equipment management. Both are related to each other. Better the equipment will give better results to understand the condition of the patient.
Safety
All Diagnostic X-ray Suites have potential hazards and we all practitioners’ must be aware of and be knowledgeable of hazard management practices.
Radiation Safety
The Deakin Diagnostic Suite is partitioned into 2 main areas:
Supervised area: where instantaneous doserates are < 7.5 uSv/hr
During exposures, with the examination room doors closed, the control room is a Supervised Area, and all occupants must wear TLD monitoring badges.
Controlled area: where instantaneous doserates are > 7.5 uSv/hr
During exposures, with the examination room doors closed, the examination room is a Controlled Area, and NO occupants are permitted in the room.
A Radiation Supervisor, with a Radiation Use License (DoH) or equivalent, must be present and monitoring all exposures undertaken. No exposures may be undertaken without a supervisor present. Examination room doors must be fully closed before exposures are undertaken. Warning lights will activate on Prepare and Expose
and the examination room doors must not be opened, or the room entered. Never point the x-ray tube (primary beam) at the door or window.
Electrical Safety
The Deakin Diagnostic Suite has High Voltage (HV) generators to energise the x-ray tubes. The generators and connected HV cables must not be touched. Visual inspection for cable and connection faults must be employed prior to use, and the Radiation Supervisor informed if any faults are suspected.
Mechanical Safety
The Deakin Diagnostic Suite has moveable x-ray and bucky stands, some of which may be moved under autonomous computer control. These movements pose a serious risk of mechanical collision to unwary occupants. Equipment may not be moved without prior warning and assent from by-standers.
Conclusion
Overall, we learn, how to measure the values of all the factors, their importance, and the respective effects on the outputs of an X-ray system. Besides that, accuracy is dependent on the equipment handling and safety precautions should be taken to avoid any accident.
References
Bushberg: The Essential Physice of Medical Imaging, 2nd
Edition
ARPANSA. (2008) Radiation Protection in the Medical Applications of Ionizing Radiation, RPS 14, ISBN 978-0-9803236-3-4
https://www.radiologyinfo.org/en/info.cfm?pg=safety-hiw_09
http://www.peo-radiation-technology.com/en/product/model-330-digital-kv-dose-and-time-meter-gammex/
