- Email: [email protected]
A pilot study on the quality control of film processing in medical radiology laboratories in Greece
European Journal of Radiology 33 (2000) 24 – 31 www.elsevier.nl/locate/ejrad
A pilot study on the quality control of film processing in medical radiology laboratories in Greece C.J. Hourdakis a,*, J. Delakis b, V. Kamenopoulou a, H. Balougias a, E. Papageorgiou a a
Greek Atomic Energy Commission, Agia Paraske6i, Attiki, 153 10 Greece Physics Department, Uni6ersity of Athens, Ilisia, Athens, 161 21 Greece
b
Received 19 January 1999; received in revised form 6 May 1999; accepted 7 May 1999
Abstract The results of a pilot study on the quality of film processing in 80 medical diagnostic radiology laboratories all over Greece are presented. The sensitometric technique for the evaluation of processing has been used to calculate film’s base + fog, maximum optical density, speed and contrast, parameters which describe the performance characteristics of automatic film processors and films. The mean values of the base +fog and the maximum optical density were well within the acceptance limits. The film speed was almost constant while the film contrast showed significant variation. © 2000 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Processor; Film; Quality control
1. Introduction Diagnostic radiology contributes more than 90% to the collective dose of the population resulting from all manmade radiation sources. [1,2]The patient who undergoes a diagnostic X-ray examination should have a sufficient net benefit against the detriment that the exposure might cause [3]. This can be achieved by keeping the patient doses as low as reasonably achievable while optimising the image quality and taking advantage of all the information that could be gained. The X-ray image is the final product of a series of procedures, where different parts and types of radiodiagnostic equipment are involved and which should co-operate to a satisfactory standard. Therefore, well established quality control tests of radiodiagnostic installations are essential not only to assure the patient radiation protection but also to assure the optimisation of the information gained. Since films and film processing are essential components and contribute independently to radiological
* Corresponding author. Tel.: + 30-1-65-44-522; fax: + 30-1-6533-939.
imaging, their quality control is essential in every radiology department. The use of automatic film processors eliminates problems associated with manual processing techniques, such as manual development of films. However, quality control tests must to be performed in order to ensure their satisfactory operation. The sensitometric technique for the evaluation of processing (STEP) is a widely accepted survey procedure [4–6] which empirically measures the processing parameters of automatic film processors.The licensing and inspection division of the Greek atomic energy commission initiated a pilot program aiming to gain information about the quality of film processing system in diagnostic radiology departments in Greece. There are : 800 diagnostic radiology facilities in private medical centres and 250 radiology departments in public, state owned, hospitals and health care centres in Greece. Although the number of automatic film processors in use countrywide is not accurately known, it is estimated that there must be : 1200 processors in operation.This paper presents the results of the quality control tests performed in 80 automatic film processors installed in private or state owned radiology departments.
0720-048X/99/$ - see front matter © 2000 Elsevier Science Ireland Ltd. All rights reserved. PII: S 0 7 2 0 - 0 4 8 X ( 9 9 ) 0 0 0 7 6 - 5
C.J. Hourdakis et al. / European Journal of Radiology 33 (2000) 24–31
2. Materials and methods During the last two years (1997 – 1998) the licensing and inspection division of the Greek Atomic Energy Commission implemented a pilot program concerning the quality control of film processing in 80 automatic film processors established in medical radiology departments. For the assessment of the film processing system the STEP was employed. A conventional film was exposed to, by means of a sensitometer (X-Rite 334) [7], a stepwedge having 21 optical densities in steps of 0.15, having a light of a colour appropriate to the type of film being used for process control (either blue or green). Each one of the film’s sides (edges) was exposed by the sensitometer and thus, in each film, four strips were obtained. The exposed film was then processed with the processor being assessed, under ordinary processing conditions. The 21 optical densities of each strip of the processed film were measured by a ‘Kodak control strip reader’ and the corresponding values were entered to the ‘Kodak X-Omat process control manager KX/PCM windows version’ computing program [8] to obtain film’s characteristic curve. In each film, four characteristic curves corresponding to the four different strips, were averaged, in order to minimise any film’s spatial optical fluctuations or nonuniformity. From the average characteristic curve of the film the following parameters have been evaluated, which characterise the overall performance of the imaging system : the base +fog, which represents the optical density of a non-irradiated film and corresponds to the lower part (toe) of the film’s characteristic curve the maximum optical density, which corresponds to the upper part of the characteristic curve (shoulder). the film speed, which represents the sensitivity of the film and indicates the amount of radiation needed to produce an optical density of 1.00 above the base+ fog [9]. the film contrast, which indicates the range and the
25
level of discrimination between different intensities of exposure. The contrast is calculated from the slope of the linear part of the characteristic curve, defined by the points corresponding to the film speed and the optical density obtained by the next fourth step of the sensitometer’s stepwedge [9]. This parameter is also referred to as Gamma of the film or average film gradient. For the calibration of the ‘Kodak control strip reader’ a Kodak calibration control strip was used. The 21 optical densities of the control strip were measured by a calibrated transmission densitometer DT 1105 (R.Y. Perry) and set to calibrate the ‘Kodak control strip reader’ by using its own software. This calibration was periodically performed in order to ensure the satisfactory performance of the reader.
3. Results Film processing was assessed by evaluating the four film parameters previously described, that is base+ fog, maximum optical density, speed and contrast. In this survey, four different types of films (Agfa Curix Ortho, Dupond Cronex Ortho, Fuji HR ortho and Kodak X-Omat) were used to assess the performance of 80 automatic film processors: 33 Agfa Gevamatic, 27 Kodak X-Omat, 12 Protec Compact and the final eight were of various type and manufacturer (Williamson, Litton, Philips and Konica). In Tables 1–4 the measured values of the base + fog, maximum optical density, film speed and film contrast are presented. Due to the fact that film parameters are affected by automatic film processor performance as well as film characteristics, the results of this survey have been classified according to the film and automatic film processor type. Therefore, in each table, the results are presented for the total assessed number of films and automatic film processors, as well as for each film type and each processor separately. Graphical representations of the above results are shown in Figs. 1–4 (A, B and C).
Table 1 Base+fog measured values for the evaluation of film processing
Sample Size Mean S.D. Min Max Median
All
Film type
Data 80 0.23 0.06 0.16 0.45 0.22
Dupond 9 0.28 0.05 0.22 0.35 0.27
Processor type Agfa 34 0.22 0.05 0.17 0.35 0.21
Kodak 16 0.25 0.07 0.18 0.45 0.24
Fuji 21 0.23 0.05 0.16 0.39 0.22
Protec 12 0.25 0.06 0.18 0.35 0.25
Agfa 33 0.22 0.05 0.17 0.35 0.21
Kodak 27 0.24 0.06 0.16 0.45 0.22
Other 8 0.27 0.09 0.19 0.42 0.23
26
C.J. Hourdakis et al. / European Journal of Radiology 33 (2000) 24–31
Fig. 1. (A), Base + fog values for all the assessed film and automatic film processor types. (B), Base + fog values for different film types. (C), Base + fog values for different automatic film processor types.
C.J. Hourdakis et al. / European Journal of Radiology 33 (2000) 24–31
27
Table 2 Maximum optical density measured values for the evaluation of film processing
Sample size Mean S.D. Min Max Median
All
Film type
Data 80 3.35 0.43 2.22 4.22 3.39
Dupond 9 3.68 0.49 3.11 4.22 3.46
Processor type Agfa 34 3.37 0.38 2.50 3.90 3.43
Kodak 16 3.47 0.28 3.10 4.11 3.38
Fuji 21 3.14 0.52 2.22 3.67 3.52
Protec 12 3.65 0.43 3.11 4.22 3.51
Agfa 33 3.35 0.40 2.22 4.11 3.48
Kodak 27 3.27 0.38 2.28 3.78 3.37
Other 8 3.49 0.43 2.85 3.96 3.57
Agfa 33 1.81 0.14 1.47 2.04 1.82
Kodak 27 1.77 0.14 1.38 2.00 1.81
Other 8 1.76 0.17 1.55 2.11 1.79
Agfa 33 2.45 0.49 1.21 3.26 2.53
Kodak 27 2.14 0.55 1.07 3.00 2.13
Other 8 2.46 0.54 1.80 3.40 2.50
Table 3 Film Speed measured values for the evaluation of film processing
Sample size Mean S.D. Min Max Median
All
Film type
Data 80 1.80 0.15 1.38 2.11 1.82
Dupond 9 1.86 0.21 1.55 2.10 1.91
Processor type Agfa 34 1.80 0.14 1.47 2.03 1.81
Kodak 16 1.80 0.17 1.38 2.11 1.82
Fuji 21 1.80 0.12 1.58 3.04 1.82
Protec 12 1.89 0.15 1.67 2.10 1.93
Table 4 Contrast measured values for the evaluation of film processing
Sample size Mean S.D. Min Max Median
All
Film type
Data 80 2.36 0.59 1.07 3.59 2.49
Dupond 9 2.24 1.02 1.15 3.59 1.97
Processor type Agfa 34 2.27 0.49 1.07 2.87 2.42
Kodak 16 2.12 0.56 1.47 3.40 1.96
4. Discussion The quality control of a film processing system in a medical radiology department is essential and should be carried out on a daily basis [6,10,11], in order to ensure its continuous satisfactory function. STEP can measure the most important film parameters, that is base + fog, maximum optical density, speed and slope which can successfully describe the overall performance of film processing. These parameters were measured in this pilot study in 80 diagnostic radiology departments all over Greece. The measured base+fog values were within the proposed acceptance limit of 0.22 [12] in more than half of the assessed film processing facilities (58% of the total) (Fig. 1A). This indicates that in the majority of radiology departments the dark room safe lighting and lightproofing were at appropriate levels, while the films had
Fuji 21 2.74 0.3 1.84 3.26 2.76
Protec 12 2.41 0.86 1.15 3.59 2.40
not deteriorated from environmental conditions and were not affected by ionising radiation. In 85% of the assessed processing facilities the values of the maximum optical density were found to exceed the value of 3.00 (Fig. 2A), a value which is suggested in almost all manufacturers’ specifications. The measured values for film contrast and speed are difficult to be compared to values provided on manufacturers’ specifications, since different test methods for the evaluation of film contrast and speed are applied by film manufacturers. The film contrast is calculated from the gradient of the linear part of the characteristic curve of the film. Since, this curve is normally sigmoid in shape, the linear part can be defined in many ways. For instance, according to Agfa [13], the two points of the characteristic curve corresponding to optical densities 0.25+ base+ fog and 2.00+ base+ fog are used for defining
28
C.J. Hourdakis et al. / European Journal of Radiology 33 (2000) 24–31
the linear part of the curve. This approach is different from DIN6868 [9] followed in this work. For the film speed, nearly all film companies [13,14] as well as several investigators [4,5] give values for the relative film speed rather than the absolute values of the film speed. The relative speed for a given film type is the ratio of the speed value of that film type to that of a reference. Agfa uses the Curix RP1 as a reference film, while Kodak uses the X-Omat RP film. Furthermore, film characteristic curves presented by manufacturers, were obtained by exposing a proper film screen combination (instead of a single film) to an X-ray beam of a given quality and using suitable stepwedge phantoms to obtain the stepwedge optical density on the film.For these reasons, the direct comparison of the data concerning film contrast and speed provided by
the film companies in various prospectus and the values of the film parameters measured in this survey, was not feasible. Therefore, intercomparisons could only be safely drawn between the performance characteristics of the assessed processors and films. The mean value of the film speed was found to be almost the same for all film and processor types ranging between 1.8 and 1.9. Film contrast mean values vary significantly from film and processor type to type. The mean contrast value (2.36) of all the assessed films and processors is somewhat below the recommended range (2.46–3.69) [13–15], while only Fuji type films proved to have contrast values within these limits. The sensitometric technique for the evaluation of film processing, used in this pilot study, showed that there
Fig. 2. (A), Maximum optical density values for all the assessed film and automatic film processor types. (B), Maximum optical density values for different film types. (C), Maximum optical density values for different automatic film processor types.
C.J. Hourdakis et al. / European Journal of Radiology 33 (2000) 24–31
29
Fig. 3. (A), Film speed values for all the assessed film and automatic film processor types. (B), Film speed values for different film types. (C), Film speed values for different automatic film processor types.
are discrepancies in the performance characteristics of automatic film processors and films, either of different or of the same type. Routine checks and quality control on a daily basis of the imaging systems should be implemented in order to improve image quality and reduce patient dose. Although this sample corresponds to only a few percent (7%) of the estimated total number of film processing facilities, it can be representative, since the type and manufacturer of the assessed films and automatic film processors are the most common. Also, the assessed processing facilities are well distributed all over
Greece operating in radiology departments of private medical centres, public hospitals and health care centres. Developer temperature, pH and passing time, although they essentially contribute to the performance of the automatic film processors [11], were not checked during this survey, since the scope of the study was to assess the performance of the film processing under actual working conditions and not to determine the reasons of any discrepancies from the normal operation. Developer temperature, pH and passing time were meant to align with the film manufacturers’ recommendations in every radiology department.
30
C.J. Hourdakis et al. / European Journal of Radiology 33 (2000) 24–31
.
Fig. 4. (A), Film contrast values for all the assessed film and automatic film processor types. (B), Film contrast values for different film types. (C), Film contrast values for different automatic film processor types.
References [1] Hendy PP. Enquiry by the commission of the European communities into the qualified expert in radiophysics. Eur Med Phys News 1990;17:3–4. [2] National Radiological Protection Board (NRPB). National Protocol for Patient Dose Measurements in Diagnostic Radiology. Dosimetry Working Party of the Institute of Physical Sciences in Medicine 1992: 1–2. [3] Council Directive 97/43 EURATOM of 30 June 1997 on health protection of individuals against the damage of ionising radiation in relation to medical exposure and repealing directive 84/466/Euratom, No L 180/22 EN Official Journal of the European Communities, 1997. [4] Suleiman OH, Rueter FG, Antonsen RG, Conway BJ, Slayton RJ. The sensitometric technique for the evaluation of processing (STEP). Rad Protec Dosim 1993;49(1/3):105–6. [5] Suleiman OH, Conway BJ, Reuter FG, Slayton RJ. Automatic
[6]
[7] [8] [9]
[10]
[11]
film processing : analysis of 9 years of observation. Radiology 1992;185:25 – 8. Gminder M, May E. Experience with the implementation of the constancy test for film processing according to §16(2) of the Roentgenverordnung (X-ray ordinance). Rad Protec Dosim 1993;49(1/3):107– 9. X-RITE 334 Operation Manual. Kodak ‘X-Omat’ Process Control Manager, Version 1.4, User Guide, 1990. DIN 6868 Teil 2 vom 2.85. Sicherung der Bildqualitat in rontgendiagnostischen Betrieben; Filmverarbeitung : Konstanzprufung der visuellen optischen Dichte (Beuth Verlag GmbH, Postfach 1145, 100 Berlin 30). National council on radiation protection and measurements, Quality Assurance for Diagnostic Imaging Equipment, NCRP Report No 99. Bethesda. 1988: 61 – 98. C Lymberis, EP Efstathopoulos, A Manetou and G Poudridis. Automatic film processors’ quality control test in Greek military hospitals. Eur J Rad 1993:246 – 9.
C.J. Hourdakis et al. / European Journal of Radiology 33 (2000) 24–31 [12] The quality assurance working group of the diagnostic methods committee of the British Institute of Radiology. Assurance of Quality in the Diagnostic X-ray Department. London: The British Institute of Radiology, 1988: 37–40. [13] Agfa, CURIX film documentation
31
[14] Kodak, X-Omat film documentation [15] HPA, Measurements of the performance characteristics of diagnostic X-ray systems used in Medicine. Topic group Report 32, Part N. 1984: 27.
A pilot study on the quality control of film processing in medical radiology laboratories in Greece C.J. Hourdakis a,*, J. Delakis b, V. Kamenopoulou a, H. Balougias a, E. Papageorgiou a a
Greek Atomic Energy Commission, Agia Paraske6i, Attiki, 153 10 Greece Physics Department, Uni6ersity of Athens, Ilisia, Athens, 161 21 Greece
b
Received 19 January 1999; received in revised form 6 May 1999; accepted 7 May 1999
Abstract The results of a pilot study on the quality of film processing in 80 medical diagnostic radiology laboratories all over Greece are presented. The sensitometric technique for the evaluation of processing has been used to calculate film’s base + fog, maximum optical density, speed and contrast, parameters which describe the performance characteristics of automatic film processors and films. The mean values of the base +fog and the maximum optical density were well within the acceptance limits. The film speed was almost constant while the film contrast showed significant variation. © 2000 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Processor; Film; Quality control
1. Introduction Diagnostic radiology contributes more than 90% to the collective dose of the population resulting from all manmade radiation sources. [1,2]The patient who undergoes a diagnostic X-ray examination should have a sufficient net benefit against the detriment that the exposure might cause [3]. This can be achieved by keeping the patient doses as low as reasonably achievable while optimising the image quality and taking advantage of all the information that could be gained. The X-ray image is the final product of a series of procedures, where different parts and types of radiodiagnostic equipment are involved and which should co-operate to a satisfactory standard. Therefore, well established quality control tests of radiodiagnostic installations are essential not only to assure the patient radiation protection but also to assure the optimisation of the information gained. Since films and film processing are essential components and contribute independently to radiological
* Corresponding author. Tel.: + 30-1-65-44-522; fax: + 30-1-6533-939.
imaging, their quality control is essential in every radiology department. The use of automatic film processors eliminates problems associated with manual processing techniques, such as manual development of films. However, quality control tests must to be performed in order to ensure their satisfactory operation. The sensitometric technique for the evaluation of processing (STEP) is a widely accepted survey procedure [4–6] which empirically measures the processing parameters of automatic film processors.The licensing and inspection division of the Greek atomic energy commission initiated a pilot program aiming to gain information about the quality of film processing system in diagnostic radiology departments in Greece. There are : 800 diagnostic radiology facilities in private medical centres and 250 radiology departments in public, state owned, hospitals and health care centres in Greece. Although the number of automatic film processors in use countrywide is not accurately known, it is estimated that there must be : 1200 processors in operation.This paper presents the results of the quality control tests performed in 80 automatic film processors installed in private or state owned radiology departments.
0720-048X/99/$ - see front matter © 2000 Elsevier Science Ireland Ltd. All rights reserved. PII: S 0 7 2 0 - 0 4 8 X ( 9 9 ) 0 0 0 7 6 - 5
C.J. Hourdakis et al. / European Journal of Radiology 33 (2000) 24–31
2. Materials and methods During the last two years (1997 – 1998) the licensing and inspection division of the Greek Atomic Energy Commission implemented a pilot program concerning the quality control of film processing in 80 automatic film processors established in medical radiology departments. For the assessment of the film processing system the STEP was employed. A conventional film was exposed to, by means of a sensitometer (X-Rite 334) [7], a stepwedge having 21 optical densities in steps of 0.15, having a light of a colour appropriate to the type of film being used for process control (either blue or green). Each one of the film’s sides (edges) was exposed by the sensitometer and thus, in each film, four strips were obtained. The exposed film was then processed with the processor being assessed, under ordinary processing conditions. The 21 optical densities of each strip of the processed film were measured by a ‘Kodak control strip reader’ and the corresponding values were entered to the ‘Kodak X-Omat process control manager KX/PCM windows version’ computing program [8] to obtain film’s characteristic curve. In each film, four characteristic curves corresponding to the four different strips, were averaged, in order to minimise any film’s spatial optical fluctuations or nonuniformity. From the average characteristic curve of the film the following parameters have been evaluated, which characterise the overall performance of the imaging system : the base +fog, which represents the optical density of a non-irradiated film and corresponds to the lower part (toe) of the film’s characteristic curve the maximum optical density, which corresponds to the upper part of the characteristic curve (shoulder). the film speed, which represents the sensitivity of the film and indicates the amount of radiation needed to produce an optical density of 1.00 above the base+ fog [9]. the film contrast, which indicates the range and the
25
level of discrimination between different intensities of exposure. The contrast is calculated from the slope of the linear part of the characteristic curve, defined by the points corresponding to the film speed and the optical density obtained by the next fourth step of the sensitometer’s stepwedge [9]. This parameter is also referred to as Gamma of the film or average film gradient. For the calibration of the ‘Kodak control strip reader’ a Kodak calibration control strip was used. The 21 optical densities of the control strip were measured by a calibrated transmission densitometer DT 1105 (R.Y. Perry) and set to calibrate the ‘Kodak control strip reader’ by using its own software. This calibration was periodically performed in order to ensure the satisfactory performance of the reader.
3. Results Film processing was assessed by evaluating the four film parameters previously described, that is base+ fog, maximum optical density, speed and contrast. In this survey, four different types of films (Agfa Curix Ortho, Dupond Cronex Ortho, Fuji HR ortho and Kodak X-Omat) were used to assess the performance of 80 automatic film processors: 33 Agfa Gevamatic, 27 Kodak X-Omat, 12 Protec Compact and the final eight were of various type and manufacturer (Williamson, Litton, Philips and Konica). In Tables 1–4 the measured values of the base + fog, maximum optical density, film speed and film contrast are presented. Due to the fact that film parameters are affected by automatic film processor performance as well as film characteristics, the results of this survey have been classified according to the film and automatic film processor type. Therefore, in each table, the results are presented for the total assessed number of films and automatic film processors, as well as for each film type and each processor separately. Graphical representations of the above results are shown in Figs. 1–4 (A, B and C).
Table 1 Base+fog measured values for the evaluation of film processing
Sample Size Mean S.D. Min Max Median
All
Film type
Data 80 0.23 0.06 0.16 0.45 0.22
Dupond 9 0.28 0.05 0.22 0.35 0.27
Processor type Agfa 34 0.22 0.05 0.17 0.35 0.21
Kodak 16 0.25 0.07 0.18 0.45 0.24
Fuji 21 0.23 0.05 0.16 0.39 0.22
Protec 12 0.25 0.06 0.18 0.35 0.25
Agfa 33 0.22 0.05 0.17 0.35 0.21
Kodak 27 0.24 0.06 0.16 0.45 0.22
Other 8 0.27 0.09 0.19 0.42 0.23
26
C.J. Hourdakis et al. / European Journal of Radiology 33 (2000) 24–31
Fig. 1. (A), Base + fog values for all the assessed film and automatic film processor types. (B), Base + fog values for different film types. (C), Base + fog values for different automatic film processor types.
C.J. Hourdakis et al. / European Journal of Radiology 33 (2000) 24–31
27
Table 2 Maximum optical density measured values for the evaluation of film processing
Sample size Mean S.D. Min Max Median
All
Film type
Data 80 3.35 0.43 2.22 4.22 3.39
Dupond 9 3.68 0.49 3.11 4.22 3.46
Processor type Agfa 34 3.37 0.38 2.50 3.90 3.43
Kodak 16 3.47 0.28 3.10 4.11 3.38
Fuji 21 3.14 0.52 2.22 3.67 3.52
Protec 12 3.65 0.43 3.11 4.22 3.51
Agfa 33 3.35 0.40 2.22 4.11 3.48
Kodak 27 3.27 0.38 2.28 3.78 3.37
Other 8 3.49 0.43 2.85 3.96 3.57
Agfa 33 1.81 0.14 1.47 2.04 1.82
Kodak 27 1.77 0.14 1.38 2.00 1.81
Other 8 1.76 0.17 1.55 2.11 1.79
Agfa 33 2.45 0.49 1.21 3.26 2.53
Kodak 27 2.14 0.55 1.07 3.00 2.13
Other 8 2.46 0.54 1.80 3.40 2.50
Table 3 Film Speed measured values for the evaluation of film processing
Sample size Mean S.D. Min Max Median
All
Film type
Data 80 1.80 0.15 1.38 2.11 1.82
Dupond 9 1.86 0.21 1.55 2.10 1.91
Processor type Agfa 34 1.80 0.14 1.47 2.03 1.81
Kodak 16 1.80 0.17 1.38 2.11 1.82
Fuji 21 1.80 0.12 1.58 3.04 1.82
Protec 12 1.89 0.15 1.67 2.10 1.93
Table 4 Contrast measured values for the evaluation of film processing
Sample size Mean S.D. Min Max Median
All
Film type
Data 80 2.36 0.59 1.07 3.59 2.49
Dupond 9 2.24 1.02 1.15 3.59 1.97
Processor type Agfa 34 2.27 0.49 1.07 2.87 2.42
Kodak 16 2.12 0.56 1.47 3.40 1.96
4. Discussion The quality control of a film processing system in a medical radiology department is essential and should be carried out on a daily basis [6,10,11], in order to ensure its continuous satisfactory function. STEP can measure the most important film parameters, that is base + fog, maximum optical density, speed and slope which can successfully describe the overall performance of film processing. These parameters were measured in this pilot study in 80 diagnostic radiology departments all over Greece. The measured base+fog values were within the proposed acceptance limit of 0.22 [12] in more than half of the assessed film processing facilities (58% of the total) (Fig. 1A). This indicates that in the majority of radiology departments the dark room safe lighting and lightproofing were at appropriate levels, while the films had
Fuji 21 2.74 0.3 1.84 3.26 2.76
Protec 12 2.41 0.86 1.15 3.59 2.40
not deteriorated from environmental conditions and were not affected by ionising radiation. In 85% of the assessed processing facilities the values of the maximum optical density were found to exceed the value of 3.00 (Fig. 2A), a value which is suggested in almost all manufacturers’ specifications. The measured values for film contrast and speed are difficult to be compared to values provided on manufacturers’ specifications, since different test methods for the evaluation of film contrast and speed are applied by film manufacturers. The film contrast is calculated from the gradient of the linear part of the characteristic curve of the film. Since, this curve is normally sigmoid in shape, the linear part can be defined in many ways. For instance, according to Agfa [13], the two points of the characteristic curve corresponding to optical densities 0.25+ base+ fog and 2.00+ base+ fog are used for defining
28
C.J. Hourdakis et al. / European Journal of Radiology 33 (2000) 24–31
the linear part of the curve. This approach is different from DIN6868 [9] followed in this work. For the film speed, nearly all film companies [13,14] as well as several investigators [4,5] give values for the relative film speed rather than the absolute values of the film speed. The relative speed for a given film type is the ratio of the speed value of that film type to that of a reference. Agfa uses the Curix RP1 as a reference film, while Kodak uses the X-Omat RP film. Furthermore, film characteristic curves presented by manufacturers, were obtained by exposing a proper film screen combination (instead of a single film) to an X-ray beam of a given quality and using suitable stepwedge phantoms to obtain the stepwedge optical density on the film.For these reasons, the direct comparison of the data concerning film contrast and speed provided by
the film companies in various prospectus and the values of the film parameters measured in this survey, was not feasible. Therefore, intercomparisons could only be safely drawn between the performance characteristics of the assessed processors and films. The mean value of the film speed was found to be almost the same for all film and processor types ranging between 1.8 and 1.9. Film contrast mean values vary significantly from film and processor type to type. The mean contrast value (2.36) of all the assessed films and processors is somewhat below the recommended range (2.46–3.69) [13–15], while only Fuji type films proved to have contrast values within these limits. The sensitometric technique for the evaluation of film processing, used in this pilot study, showed that there
Fig. 2. (A), Maximum optical density values for all the assessed film and automatic film processor types. (B), Maximum optical density values for different film types. (C), Maximum optical density values for different automatic film processor types.
C.J. Hourdakis et al. / European Journal of Radiology 33 (2000) 24–31
29
Fig. 3. (A), Film speed values for all the assessed film and automatic film processor types. (B), Film speed values for different film types. (C), Film speed values for different automatic film processor types.
are discrepancies in the performance characteristics of automatic film processors and films, either of different or of the same type. Routine checks and quality control on a daily basis of the imaging systems should be implemented in order to improve image quality and reduce patient dose. Although this sample corresponds to only a few percent (7%) of the estimated total number of film processing facilities, it can be representative, since the type and manufacturer of the assessed films and automatic film processors are the most common. Also, the assessed processing facilities are well distributed all over
Greece operating in radiology departments of private medical centres, public hospitals and health care centres. Developer temperature, pH and passing time, although they essentially contribute to the performance of the automatic film processors [11], were not checked during this survey, since the scope of the study was to assess the performance of the film processing under actual working conditions and not to determine the reasons of any discrepancies from the normal operation. Developer temperature, pH and passing time were meant to align with the film manufacturers’ recommendations in every radiology department.
30
C.J. Hourdakis et al. / European Journal of Radiology 33 (2000) 24–31
.
Fig. 4. (A), Film contrast values for all the assessed film and automatic film processor types. (B), Film contrast values for different film types. (C), Film contrast values for different automatic film processor types.
References [1] Hendy PP. Enquiry by the commission of the European communities into the qualified expert in radiophysics. Eur Med Phys News 1990;17:3–4. [2] National Radiological Protection Board (NRPB). National Protocol for Patient Dose Measurements in Diagnostic Radiology. Dosimetry Working Party of the Institute of Physical Sciences in Medicine 1992: 1–2. [3] Council Directive 97/43 EURATOM of 30 June 1997 on health protection of individuals against the damage of ionising radiation in relation to medical exposure and repealing directive 84/466/Euratom, No L 180/22 EN Official Journal of the European Communities, 1997. [4] Suleiman OH, Rueter FG, Antonsen RG, Conway BJ, Slayton RJ. The sensitometric technique for the evaluation of processing (STEP). Rad Protec Dosim 1993;49(1/3):105–6. [5] Suleiman OH, Conway BJ, Reuter FG, Slayton RJ. Automatic
[6]
[7] [8] [9]
[10]
[11]
film processing : analysis of 9 years of observation. Radiology 1992;185:25 – 8. Gminder M, May E. Experience with the implementation of the constancy test for film processing according to §16(2) of the Roentgenverordnung (X-ray ordinance). Rad Protec Dosim 1993;49(1/3):107– 9. X-RITE 334 Operation Manual. Kodak ‘X-Omat’ Process Control Manager, Version 1.4, User Guide, 1990. DIN 6868 Teil 2 vom 2.85. Sicherung der Bildqualitat in rontgendiagnostischen Betrieben; Filmverarbeitung : Konstanzprufung der visuellen optischen Dichte (Beuth Verlag GmbH, Postfach 1145, 100 Berlin 30). National council on radiation protection and measurements, Quality Assurance for Diagnostic Imaging Equipment, NCRP Report No 99. Bethesda. 1988: 61 – 98. C Lymberis, EP Efstathopoulos, A Manetou and G Poudridis. Automatic film processors’ quality control test in Greek military hospitals. Eur J Rad 1993:246 – 9.
C.J. Hourdakis et al. / European Journal of Radiology 33 (2000) 24–31 [12] The quality assurance working group of the diagnostic methods committee of the British Institute of Radiology. Assurance of Quality in the Diagnostic X-ray Department. London: The British Institute of Radiology, 1988: 37–40. [13] Agfa, CURIX film documentation
31
[14] Kodak, X-Omat film documentation [15] HPA, Measurements of the performance characteristics of diagnostic X-ray systems used in Medicine. Topic group Report 32, Part N. 1984: 27.