MICHELLE FERDERBAR 1217500
Kilovolt peak (kVp) is a technical factor set by the technologist when performing x-rays. Its purpose is to set the penetrating power of the x-rays or the quality of the beam. The number set is the highest amount of energy that an x-ray photon could have leaving the tube. It is important that the kVp setting reflects what is actually coming out of the tube to ensure reproducibility. This lab was conducted in x-ray room 4 and x-ray room 3, B114 of the Institute of Applied Health Sciences on the McMaster University Campus.
The procedure was fairly simple. We set the SID to 70 cm and collimated to the entirety of the sensor. We took three exposures each at 60 kVp, 81 kVp, and 102 kVp at 5 mAs. We took another three exposures each at the aforementioned kVps but at 16 mAs. We used the Cobia Smart x-ray meter to determine the kVp values in Room 4 and a different meter in room 3. When we took these exposures, we waited roughly 30 seconds between each exposure to prevent tube overload.
kVp | mAs | Value 1 | Value 2 | Value 3 | Average kVp | Percentage Difference |
---|---|---|---|---|---|---|
60 | 5 | 51.83 | 51.50 | 51.35 | 51.56 | -14.07 |
60 | 16 | 51.32 | 51.35 | 51.25 | 51.31 | -14.48 |
81 | 5 | 78.93 | 79.17 | 79.35 | 79.15 | -2.28 |
81 | 16 | 79.13 | 79.19 | 79.12 | 79.15 | -2.28 |
102 | 5 | 98.54 | 98.01 | 98.06 | 98.20 | -3.73 |
102 | 16 | 99.56 | 98.79 | 98.61 | 98.99 | -2.95 |
kVp | mAs | kVp 1 | kVp 2 | kVp 3 | Average kVp | Percentage Difference |
---|---|---|---|---|---|---|
60 | 5 | 60.07 | 60.17 | 60.23 | 60.16 | +1.93 |
60 | 16 | 60.15 | 60.16 | 60.22 | 60.18 | +1.97 |
81 | 5 | 80.95 | 81.01 | 80.97 | 80.98 | +1.23 |
81 | 16 | 81.14 | 81.10 | 81.11 | 81.12 | +1.40 |
102 | 5 | 101.6 | 101.6 | 101.7 | 101.6 | -0.36 |
102 | 16 | 101.9 | 101.9 | 101.8 | 101.9 | -0.13 |
There are guidelines set by H.A.R.P. and S.C. 35 to ensure an appropriate range of kVp accuracy. H.A.R.P. sets the accuracy at ±8% while S.C. 35 sets it at ±10%. Papp (2011) is the most strict with ±5%. In room 4, all kVp settings pass. In room 3, 60 kVp at 5 mAs and 60 kVp at 16 mAs fail by all standards. Some possible reasons for this are that the reader was less sensitive to this lower kVp setting, the unit has faulty circuitry, the high voltage transformer may be malfunctioning, the autotransformer may have an issue, or the supply to the generator is not the greatest (Stelmark, 2010). It is very important that kVp accuracy is maintained to ensure that the desired technique is coming out of the tube. Since kVp controls both x-ray beam quality and quantity, having the incorrect kVp exiting the tube may result in failing to follow the ALARA principle and overdosing our patient. This test should be performed annually (Papp, 2011).
References
Health Canada. (2008). Safety code 35: Safety procedures for the installation, use and
control of x-ray equipment in large medical radiological facilities.
Retrieved from http://www.hc-sc.gc.ca.
Papp, J. (2011). Quality management in the imaging sciences (4th ed.). St. Louis,
Mo.: Mosby Elsevier.
Service Ontario. (2011). Healing Arts Radiation Protection Act. Retrieved from
http://www.e-laws.gov.on.ca/html/regs/english/elaws_regs_900543_e.htm.
Stelmark, J. (2010). Applied Quality Management: kVp Accuracy and Reproducibility.
Retrieved from http://profstelmark.com/QA_new/report%20sample.pdf.
control of x-ray equipment in large medical radiological facilities.
Retrieved from http://www.hc-sc.gc.ca.
Papp, J. (2011). Quality management in the imaging sciences (4th ed.). St. Louis,
Mo.: Mosby Elsevier.
Service Ontario. (2011). Healing Arts Radiation Protection Act. Retrieved from
http://www.e-laws.gov.on.ca/html/regs/english/elaws_regs_900543_e.htm.
Stelmark, J. (2010). Applied Quality Management: kVp Accuracy and Reproducibility.
Retrieved from http://profstelmark.com/QA_new/report%20sample.pdf.