MICHELLE FERDERBAR 1217500
Reproducibility is important in diagnostic radiography, but it arguably may be even more important when it comes to specialty branches of radiography such as mammography. Reproducibility in the mammography setting would ensure that all patients' breasts' are being imaged exactly the same and the sensitive tissue is not being overexposed. It is so important, it is often suggested that women return to the same breast clinic for their routine and follow-up images. This lab was done to test for the reproducibility of a mammography unit, done in B114 of the Institute of Applied Health Sciences on the McMaster University Campus.
To conduct this lab, a Rad Check, lead sheet, and a mammography machine were utilized. The mammography machine was produced by Christie Group Limited. The lead sheet was placed on the plate and the Rad Check, or exposure meter, was placed on the lead sheet. The compression panel was lowered onto the Rad Check meter, as demonstrated in Figure 1. 10 exposures were taken at 25 kVp and 5 mAs. Between each exposure, it was pertinent to wait for the machine to flash "READY" to show it was prepared for the next exposure. In the meanwhile, "STANDBY" was lit. Table 1 demonstrates the various values that were obtained in each of the 10 exposures. The average of the exposures was found to be 0.0916 R.
|
Exposure Number | Reading (R) |
---|---|
1 | 0.092 |
2 | 0.092 |
3 | 0.092 |
4 | 0.091 |
5 | 0.091 |
6 | 0.091 |
7 | 0.091 |
8 | 0.092 |
9 | 0.092 |
10 | 0.092 |
The next step was to determine the reproducibility coefficient.
According to Safety Code 36 (SC 36) (2013), "...the coefficient of variation of any ten consecutive radiation exposure measurements, taken at the same source to detector distance within a time period of one hour, is no greater than 0.05." Since our value was determined to be 0.005, as shown in Figure 2, we are well within the established guidelines. SC 36 (2013) further states, "...and each of the ten radiation exposure measurements is within 15 percent of the mean value of the ten measurements." The values are all within this parameter as well. It is suggested that this test be performed semi-annually. There are several other tests that are to be performed on the mammography machine. Focal spot size, beam limiting device, and compression plate alignment tests are to be done annually. Tests that are to be done semi-annually include radiation output, x-ray timer, backup timer, x-ray tube voltage, and radiation beam quality tests.
If a mammography machine is not functioning properly, there are many detrimental effects that would result. As aforementioned, reproducibility is what is strived for in mammography and a machine that would fail any of the tests would not have high reproducibility. An improperly functioning machine could result in harm to the patient, the technologist, and the general public. The patient would suffer in a matter of different ways. In this scenario, if the reproducibility coefficient failed, it is possible that the breast would either be under- or over-penetrated, which could result in a misdiagnosis and either a false positive or false negative. Another issue would be that the patient dose could be much higher than desired. Additionally, the tech could also be in danger if the beam limiting device was not functioning properly as well as the public through scatter radiation. All tests performed are very important to ensure safety of all involved, which is a main goal of SC 36.
If a mammography machine is not functioning properly, there are many detrimental effects that would result. As aforementioned, reproducibility is what is strived for in mammography and a machine that would fail any of the tests would not have high reproducibility. An improperly functioning machine could result in harm to the patient, the technologist, and the general public. The patient would suffer in a matter of different ways. In this scenario, if the reproducibility coefficient failed, it is possible that the breast would either be under- or over-penetrated, which could result in a misdiagnosis and either a false positive or false negative. Another issue would be that the patient dose could be much higher than desired. Additionally, the tech could also be in danger if the beam limiting device was not functioning properly as well as the public through scatter radiation. All tests performed are very important to ensure safety of all involved, which is a main goal of SC 36.
references
Health Canada. (2013). Radiation Protection and Quality Standards in Mammography
- Safety Procedures for the Installation, Use and Control of Mammographic X-ray
Equipment: Safety Code 36. Retrieved 12 March 2015 from
http://www.hc-sc.gc.ca/ewh-semt/pubs/radiation/safety-code_36-securite/
index-eng.php.
- Safety Procedures for the Installation, Use and Control of Mammographic X-ray
Equipment: Safety Code 36. Retrieved 12 March 2015 from
http://www.hc-sc.gc.ca/ewh-semt/pubs/radiation/safety-code_36-securite/
index-eng.php.