Posted at 11.19.2018
The research design because of this analysis is of a comparative quantitative, quasi-experimental character. The rationale because of this comparative study is to see what impact two different anti-scatter techniques have on image quality. The properties that make this a quasi-experimental study are manipulation of specific parameters and control in experimentation and screening (Parahoo, 2006). True experimental research is characterised by three properties: manipulation, control and randomisation (Parahoo, 2006). As the researcher won't randomise any parameters, this study is recognized as quasi-experimental rather than a genuine experimental research.
In this research manipulation was achieved since a typical anti-scatter strategy was in comparison to an air gap technique adapted for the projection of the hip in the lateral position. Exposure factor factors were also manipulated using an computerized publicity control (AEC). Control was retained by testing both techniques under the same conditions using the same research tools. Furthermore, the researcher kept control of the study by tests only the anti-scatter techniques using one specific projection. Which means results achieved by this study are specific to the lateral hip projection. However, the rule could be employed to other projections in order to discover which technique works better in providing good image quality in that specific projection.
The following strategy was adapted from a report carried out in the United Kingdom by Goulding (2006) who looked at the air space and the grid strategy used to image the hip laterally in the University Hospital she trained in. The analysis was conducted with the aid of reporting radiographers in the Incident and Emergency (A&E) division where they performed both grid and air difference technique as usual projections on patients. Goulding (2006) looked at image quality by attaining the hip radiographs performed with both anti scatter techniques separately. Goulding (2006) collected her data by asking reporting radiographers to comment on these radiographs. In Goulding's (2006) analyze the radiographs on which she founded her results and results were conducted on patients of different size and this may have lacked reliability due to different visibility factors used for every single assessment, different patient medication dosage depending on patient size as well as image quality.
Using an identical strategy in this review the researcher evaluated image quality by using a quality control phantom and an anthropomorphic phantom. In doing this the researcher will ensured that tests done on both anti-scatter techniques to determine for image quality were more correct. The methodology because of this research and the tools used to measure image quality in both grid and air space technique are described in the following sub-sections.
In this analysis the tools mentioned in this section were used to assemble the data. They were used to test the anti-scatter techniques being compared and looked into in this review which is explained further on in this section.
Since this research looks at image quality in two anti-scatter techniques, a lead quality control phantom (PTW Normi 13) was a very important tool used to collect the data. According to Carlton & Adler (2006), spatial resolution and contrast resolution are the most crucial properties upon which devices and techniques can be analyzed. The lead quality control phantom (Appendix B) is designed to perform constancy and popularity tests on plain digital x-ray systems and is able to test image receptors because of their homogeneity, spatial image resolution and contrast resolution (PTW-Freiburg, 2005). However, in this research, spatial resolution and contrast resolution were the two relevant key checks for image quality. Spatial image resolution is measured by keeping track of the greatest amount of series pairs per millimetre (Lp/mm) while distinction resolution is assessed by the low contrast steps seen on the resultant image. The areas on the phantom that are used to evaluate spatial and contrast image resolution are shown in Appendix B.
In collecting the data, the researcher used an anthropomorphic pixy phantom AR10A (Appendix B) to image the hip laterally by using a horizontal beam. This phantom was used so that the exposures of both grid and air difference technique performed on the product quality control phantom could be done to image a hip that resembles that of a man. As the anthropomorphic phantom used possessed the same attenuation coefficient of any body, it stops the radiation transferring through it just as that a human body would.
Although this study evaluates image quality in two anti-scatter techniques, rays given to the subject matter/object at each exposure using the environment space and grid strategy was also saved and likened. The quantity of radiation shown by the pipe at each publicity was also measured using a dose area product (DAP) metre. This was important in order to see how much radiation was being used at each contact with produce an image using the grid and air difference technique.
All the exposures (in this experimental screening) were made using an automatic vulnerability control (AEC) which is included in the erect bucky in the digital x-ray system used. This product established how much mAs was used in each exposure so the right amount of x-ray photons irradiated the image receptor to produce a graphic with adequate quality. This device was used since the mAs that is used in an exposure determines how good the image quality is really as well as the individual medication dosage. Therefore when the readings using the tools mentioned were compiled from all exposures, the researcher could compare these results and identify the ideal technique and coverage that should be used in imaging the hip laterally. This system and publicity should ideally produce a good quality image with as low a medication dosage as is possible.
The pursuing two subsections will describe in detail the way the data was collected during the experimentation on the anti scatter techniques. The researcher ensured that the tools used in the trials were stored the same to test both techniques. The same digital x-ray system was also used throughout the whole experimentation.
Testing for this approach was divided in two stages. Within the first stage the researcher used the quality control phantom (PTW Normi 13). The phantom was put on a tailor made table in touch with the erect imaging receptor. A fixed parallel grid was positioned between the phantom and the receptor since this is the sort of grid used in a lateral hip capture through projection. In this system, the object to image distance (OID) was that of 0cm because the phantom was in touch with the grid and image receptor. The foundation to image distance (SID) used was that of 1 metre (100 cm) since this is actually the standard SID found in such a projection in the radiology division of the neighborhood hospital. The kV used was held continuous at 75 kV and the phantom was centred to the central AEC. The light beam diaphragm was arranged around the curves of the quality control phantom. An additional publicity was made using the same grid approach setting. However, this time around the grid was removed. This is done to be able to discover whether the grid was working effectively in absorbing scatter radiation, which could affect image quality. The DAP metre was documented so that the researcher may have an approximate idea of the dose given to the phantom.
The second stage in testing the grid technique was done by using the anthropomorphic phantom. The researcher set up the pixy phantom AR10A with the hip in touch with the grid and receptor. The hip was centred with the central AEC and open. The kV and the SID were the same as the ones found in testing the product quality control phantom 75kV and 100cm SID. The set-ups used to check the grid techniques using both phantoms are available in Appendix B.
To test for the air gap technique the researcher also divided the tests into two stages. The identical quality control phantom used recently in the grid technique was also utilised in this test/experiment. The PTW Normi 13 was positioned over a custom-made stand. However, in this system, an air space between the phantom and the image receptor was applied. There were a total of six air spaces applied, varying from 10cm to 60cm. This was done in order to see which air difference was far better in reducing scatter radiation achieving the receptor. To achieve this aim the thing to image distance (OID) was increased by 10 cm after each exposure to no more than 60 cm. The foundation to subject distance (SOD) was held at 100 cm to lessen object magnification as much as possible since this might create a reduction in image sharpness. The source to image distance (SID) depended on what OID was used. Therefore when an OID of 20cm was applied, the SID was that of 120cm. This was done to ensure that the distance of the foundation to the thing remained at 100cm. In each coverage the phantom was centred to the central AEC and the light beam diaphragm was placed around the curves of the quality control phantom. The researcher also used the DAP metre to see which air gap produced a good quality image with a sensibly low dose. This was done so the air gap exposures could be weighed against the typical grid approach.
In the second stage of tests for the air gap strategy the researcher also used the same anthropomorphic phantom. The environment of the technique to image the hip laterally was modified from Goulding's (2006) analysis by using the same patient placement that the author used in her research. This setting involved applying an air space between the phantom's hip and the receptor, keeping the SOD at 100cm. A total of six exposures were also performed on the pixy phantom AR10A with the same OIDs and SIDs used to image the product quality control phantom. The researcher ensured that the phantom's hip was centred with the central AEC of the erect image receptor. Both options used to execute testing on mid-air gap technique are available in Appendix B.
The data was accumulated during Feb 2010. The data record bed sheets used to track record the data can be found in Appendix A.
· Visibility Factors
The vulnerability factors used to create the images in the grid and air distance technique were documented. The kV was a regular factor as the mAs changed based on the technique used and its own setting. The mAs was manipulated through the AED. This was done so that the amount of x-ray photons had a need to produce the image and the distance of the publicity was recorded depending on approach used.
· Object to Image Distance (OID)
The OID found in testing the grid and air gap technique was noted. This is important, especially in the use of the air gap technique. It is because the OID in the air gap technique driven the magnitude of the air gap that needs to be used to achieve a good quality image while keeping rays dose only possible. Which means researcher could see and analyse the result on the image quality whenever a specific OID was found in relation to vulnerability factors. In the air space technique the SID depended on what OID was used. The researcher placed the SOD at 100cm to reduce whenever you can magnification of the resultant image.
· Dose Area Product (DAP)
The DAP metre was noted at each exposure for both grid and air distance techniques. Although this metre does not measure the radiation dose directed at the phantoms at each exposure, it gives an indication of whether the dose would be low or high. A high DAP reading means that more radiation was used in the exposure and therefore the resultant patient medication dosage may be higher. The readings from this metre for both techniques were compared with regards to image quality of the radiographs.
· Transmission to noise ratio (SNR)
The sign to noise proportion (SNR) includes the un-attenuated photons which have penetrated the topic without discussion (sign) and the Compton scatter and other factors that degrade image quality (sound). The SNR was used to determine how much contrast resolution an image acquired after each visibility. The bigger the SNR the better the contrast resolution of an image (Dendy & Heaton, 2006). However a high SNR does mean high mAs and therefore a higher patient dose. The SNR was determined by dividing the mean pixel value by the standard deviation of the indication of each coverage. The mean pixel value and standard deviation of the signal were recorded after every coverage provided by the digital x-ray system. Which means formula used was:
Signal to Sound proportion = mean pixel value/standard deviation (reference point)
· Spatial Resolution and Comparison Resolution
The spatial and contrast resolution readings were noted by the researcher from the radiographs achieved using the product quality control phantom in the grid and air gap technique. The brand pairs per millimetre (Lp/mm) were assessed to test for spatial image resolution, while for compare resolution the low compare steps were counted. The info documented was tabulated in desks 2a and 2b respectively in the data record sheet. This saved data enabled the researcher to compare the image quality in both techniques.
Unlike Goulding (2006) in this analysis two self-employed radiologists which were chosen randomly from the researcher were asked to article on image quality on all the radiographs performed on the anthropomorphic pixy phantom AR10A. Radiologists were chosen in this research since in Malta there are no confirming radiographers that survey on the appendicular skeleton. The radiologists were asked to article on the images by answering a likert range (1=very poor and 5=very good) to examine image quality. The results were tabulated in table 3 of the data record sheet.
Validity identifies the degree the study instrument used in the study steps what it is supposed to assess. Therefore:
"Validity reflects the precision with that your findings reveal the occurrence being researched" (Parahoo, 2006, p. 80)
In this research, the researcher consulted with the medical physicist at the neighborhood hospital who was simply asked to evaluate the content validity of the research tools used to gather the data. The medical physicist considered the research tools valid since the same tools are used in the medical imaging team to test for image quality on the digital x-ray systems. As the research tools were regarded to be totally valid, the info collected to measure image quality in the grid and air difference technique can be said to be valid.
Reliability identifies how consistent a musical instrument is in calculating what it is intended to measure (Parahoo, 2006). To keep the equivalence consistency of the lead quality control phantom used for analysis of image quality, two 3rd party observers were asked to evaluate both spatial and contrast image resolution of the two images achieved using the same publicity factors, OID and SID. The researcher tested for the reliability of the automated coverage device used. This was done by revealing the lead phantom twice without manipulating the setting up or subjection factors and the results were documented. The spatial quality, contrast resolution and DAP metre readings were the same in both images so the AEC was considered reliable enough to use in the screening and data collection.
Ethics is defined by Polit & Beck (2006) as a system of moral prices that can protect the participant from the research types of procedures as the researcher has professional, legal and sociable obligations for the participants involved in the research. However, in this research, no human being subjects were mixed up in experimentation and collection of data, so there have been no ethical issues about the exposures done on the PTW NORMI 13 phantom and the anthropomorphic phantom pixy AR10A. Agreement was desired for the use of the x-ray equipment from Medical Imaging Section at the local hospital. Experimentation was performed under supervision and safety measures were taken up to ensure that radiation would not harm every other members of the personnel or public where in fact the study was performed.
Limitations were came across by the researcher throughout this analysis. The study was conducted utilizing a quality control phantom and an anthropomorphic phantom. Although both phantoms are created to mimic and represent a patient as well concerning produce comparative scatter radiation, patient size was a adjustable that cannot be put into the analysis. The DAP metre was found in this study so the researcher could have an idea of the dosage being attenuated by the phantoms used. Ultimately the real patient medication dosage should be measured but this may not be achieved since no human subject matter were used. Extension of this research would lead to a much better knowledge of the dose given to patients while evaluating the air distance and grid way of the lateral hip throw through.
This research was completed using a digital x-ray system in the radiology department at the local hospital. Tube outcome and technique setup may vary when working with other systems. Inside the radiology department, computed radiography is utilized to execute a lateral hip capture through examination rather than digital system which is exactly what the researcher used in this study. In data analysis the readings from the product quality control phantoms were interpreted by the researcher himself and not by numerous people. If several person interpreted the results, the results may have mixed. Although these restrictions are valid, they had no effect on the data collected and the results achieved.
This chapter explained the technique and the research design of this study. Another chapter includes presentation, evaluation and discussion of the data.