Analysis of Quality Assurance Items of Film Screen and CR Systems

 

Kyung-Wan Kim¹, Cheong-Hwan Lim^*2, Sung-Hun Joung³

Dept. of Radiological Science, Hanseo University, Korea

 

ABSTRACT:

Background/Objectives: Korea is currently using F/S and CR systems for diagnostic radiation equipment. However, due to the lack of quality assurance items, further research regarding the criteria and items of diagnostic radiation equipment for analog and digital systems is needed.

Methods/Statistical analysis: Diagnostic radiation equipment installed at H University in Chungnam, Korea, was used for testing and both F/S and CR systems were scrutinized. For the F/S system, a 10×12inch cassette, 10×12inch films and an automatic developing machine (JP-33) were used. The CR system was assessed using a 10x12 inch IP cassette and an image reader. The measurement items comprised the uniformity of images, resolution, and high-contrast resolution.

Findings: In the uniformity test, the difference in optical density between the F/S system and the CR system was ±0.1%. Regarding uniformity, the IEC recommends an optical density baseline difference to be less than ±0.10. The uniformity of this test meets international standards. In the high-contrast resolution test, F/S system and CR system values were 4.0 and 3.0, respectively. In the resolution test, F/S system and CR system values were 5.62 and 4.61 at 5mAs, respectively. At 10mAs, the F/S system’s value was 5.62 and that of the CR system was 4.84.

Improvements/Applications: The uniformity test, high-contrast resolution test, and resolution test results showed the F/S system to be superior to the CR system. Therefore, it is considered that the uniformity test, the high-contrast resolution test, and the resolution test should be performed as common items in the quality assurance of each system’s diagnostic radiation equipment.

 

 

 

 

1. INTRODUCTION:

The images of modern diagnostic radiation equipment have changed from film screen (F/S) systems to picture archiving communication systems (PACS) and they are digitally acquired^1-4 However the development of diagnostic radiation equipment is accompanied by an increased number of diagnostic radiological examinations and radiation exposure to the patients. To decrease the dose of radiation exposure, the radiologists’ techniques must be skilled, the irradiation dose at a minimum, and an accurate quality assurance system in place^5-7.

 

However, the diagnostic radiation equipment in Korea is currently only inspected every three years and images are not evaluated⁸. The F/S and computed radiography (CR) systems have many differences in terms of image acquisition methods and image representations. Since the image acquisition of diagnostic radiation equipment has changed to digital means, the quality assurance for image evaluations has changed as well. Compared to analog systems which mainly use phantoms for image evaluations, digital image devices employ programs which involve a more complicated process. Korea currently utilizes a mixture of analog F/S systems and digital CR systems due to differences in the equipment’s development and implementation. Therefore, it is necessary to establish a quality assurance item capable of evaluating analog and digital systems from the same baseline. The objective of this research was to provide basic data for the determination of common quality assurance items for diagnostic radiation equipment that apply to both analog and digital systems.

 

2. MATERIALS AND METHODS:

2.1 Equipment:

The equipment used in this study was a diagnostic radiation system installed at H University in Chungnam Province (Dong Kang Medical, AccuRay-525R [R-500-125], Korea). To measure the F/S system’s quality assurance items, 10×12inch cassette (Fujifilm, Japan), 10×12 inch films (Fujifilm, Japan), and an automatic developing machine (JP-33, Korea) were used. The CR system was measured with 10×12 inch IP cassettes (Fujifilm FCR, Japan) and an image reader (Fujifilm FCR, Japan). The image’s size and region of interest (ROI) were set for measurement and analyzed with an image J 1.50 program [Figure 1], [Figure 2].

 

Figure 1. FUJIFILM. JAPAN FCR IP 10”X12”

 

Figure 2. DongKang MEDICAL Accuray525R. KOREA(R-500-125)

2.1.1Measured Objects:

A test instrument manufactured in accordance with the recommended IEC 61223-2-11 method was used for uniformity measurement [Figure 3]. A high-resolution bar phantom was employed for high-contrast resolution assessment [Figure 4] and a star test phantom determined the resolution [Figure 5],

 

Figure 3. Film maker testing equipment [IEC 61223-2-11]

 

Figure 4.High Resolution Bar phantom

 

Figure 5.Star test Phantom

 

2.2. Research Method:

2.2.1 Uniformity Test:

An IEC 61223-2-11recommended method was used for measurement. The CR system was measured at RQA5 (70 kVp) as recommended by the IEC 61267 standard and a focus film distance (FFD) of 150 cm. The F/S system was measured at 40kVp 100mA and twice at 5mAs and 10mAs. Four ROI regions were set–two inner and two outer each. The mean values of the measured images’ inner and outer regions were determined. To assess concentration values, a densitometer was used for the F/S system and Image J for the CR system [Figure 6], [Figure 7].

 

Figure 6.Uniformity TEST

 

Figure 7.Uniformity TEST

 

2.2.2 High-Contrast Resolution Test:

High-contrast resolution was assessed based on the IEC 61223-2-11-5.4 standard. The CR system was measured at 60 KVP, 1 m A, tube angle 45°, and at a FFD of 150cm from the instrument’s surface. The F/S system was assessed at 40 kVp, 100 mA, 5 mA, and 10 mA [Figure 8], [Figure 9].

 

Figure 8. High Contrast Resolution TEST

 

Figure 9. High Contrast Resolution TEST

 

2.2.3 Resolution Test:

Resolution was measured based on the AAPM NO.93 8.4.6test method. The CR system was assess data FFD of 150 cm and a RQA 5 (70 kVp). The F/S system was measured at 40 kVp, 100 mA, 5 mA, and 10 mA, and the image was evaluated by measuring the ratio of the total lead’s length to the disappeared lead’s length (Equation 1)⁹ [Figure 10], [Figure 11].

          

         D_Image

D=----------------                                               (1)

             D                                                          

 

 

 

Figure 10. Resolution TEST

 

Figure 11. Resolution TEST

 

3. RESULTS AND DISCUSSION:

3.1 Uniformity Test Results:

In the uniformity test, the F/S system was more uniform than the CR system as shown in the results at 5mAs and 10mAs. In the F/S system, the inner average was 2.28 and the outer average 2.24, with a total uniformity of 1.01 at 10mAs. In the CR system, the inner average was 31.72 and the outer average 31.21, with a total uniformity of 0.97 [Table 1].

 

Table 1. Uniformity TEST

	5 mAs		10 mAs
	F/S system	CR system	F/S system	CR system
1	2.31	30.02	2.47	33.23
2	2.26	36.52	2.45	30.21
Avr.	2.28	33.27	2.46	31.72
3	2.23	30.61	2.44	30.64
4	2.25	37.98	2.46	31.78
	2.24	34.29	2.45	31.21
Total Mean	1.01	0.97	1.00	1.01

 

3.2. High-Contrast Resolution Test Results:

In the high-contrast resolution test, the F/S system was 4.0 LP/mm and the CR system 3.0 LP/mm. The difference between the two systems was 1.0 LP/mm with the F/S system’s value being higher [Table 2].

 

Table 2. High Resolution TEST (unit: (LP/mm))

 

3.3. Resolution Test Results:

At 5mAs, the resolution of the F/S system was 5.62 and of the CR system 4.61, the F/S system exhibited a higher resolution by 1.01. At 10mAs, the F/S system’s resolution was 5.62 and the CR system’s was 4.84.The F/S system showed a higher resolution by 0.71[Table 3].

 

Table 3.Resolution TEST

	5mAs		10mAs
	F/S system	CR system	F/S system	CR system
D image	4.50	299.93	4.50	301.84
D	0.80	65.00	0.80	62.35
M	5.62	4.61	5.62	4.84
Dimage=Total length of leadD=Length from the part where lead is lost

 

3.4. DISCUSSION:

In the “IEC 61223-2-11” and the “JISZ 4752,” it is stated that an optical density difference of the uniformity test should be within ± 0.10 and ± 0.20 of the baseline. The results of this research revealed a 1.01 uniformity of the F/S system and a 0.97uniformity of the CR system at 5mAs. At 10mAs, the F/S system uniformity was 1.00 and the CR system’s1.01. The uniformity can be used as a quality assurance item, because the results are within the recommended standard values of both the IEC 61223-2-11 and the JISZ 4752 standards.

 

The resolution was measured using equation (1) of the star test phantom as stated in the report "Evaluating X-Ray Tube and Generator Performance: Demo for Practical Quality Control". In this test, using the method above, the F/S system proved to have a higher resolution than the CR system. This can be an important indicator to measure resolution for the image readability quality assurance of each system¹⁰. High-contrast resolution test results were used as a quality assurance item in this test as an indicator that can observe a high-contrast resolution in image quality assurance.

 

Therefore, quality assurance test items recommended by the IEC 61223-2-11, AAPM NO.93, and AAPM NO. 74, such as a consistency test, should be conducted in this type of research.

 

4. CONCLUSION:

This study was conducted to determine the common quality assurance items of diagnostic radiation equipment for analog and digital systems. The following conclusions were reached: As a result of the uniformity test, F/S and CR systems both measured within ± 10%, and were suitable as uniformity evaluation items. The high-contrast resolution test was 4.0 for the F/S system and 3.0 for the CR system. In the resolution test, the F/S system’s values were 5.62, 5.62, and the CR system’s 4.61, 4.84.

 

Therefore, the uniformity test, the high-contrast resolution test, and the resolution test are considered to be suitable as common items for the quality assurance of diagnostic radiation equipment.

 

5. ACKNOWLEDGMENT:

This research has been conducted with financial support by Hanseo University in 2016.

 

6. REFERENCES:

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Accepted on 25.03.2017          © RJPT All right reserved