Quality assurance programme applied to mobile C-arm fluoroscopy systems

Eur. Radiol. 7, 534–541 (1997)  Springer-Verlag 1997

European Radiology

Physics

Original article Quality assurance programme applied to mobile C-arm fluoroscopy systems B. Tuohy, D. M. Marsh, G. O’Reilly, A. Dowling, P. Cooney, J. F. Malone Department of Medical Physics and Bioengineering, St. James’s Hospital, James’s Street, Dublin 8, Ireland Received 16 February 1996; Revision received 8 July 1996; Accepted 23 August 1996

Abstract. The importance of quality assurance (QA) of X-ray equipment in diagnostic imaging departments is well recognised. However, practically no attention has been paid in the literature to the application of QA programmes to mobile C-arm fluoroscopy systems. This equipment is sometimes omitted from these programmes because it is often “off-site” from the main radiological facility and suitable QA protocols are unavailable. The need for QA can be substantiated by the fact that these systems are finding greater clinical use in orthopaedic, vascular and cardiac applications. Hence, there is a growing awareness among users for the need of good image quality and low patient radiation dose. In view of this, the objective of this study was to review the existing literature, design a suitable QA protocol for this equipment and use it to survey 10 C-arms in clinical use. The protocol was designed to address mechanical and electrical safety in addition to radiation safety and image quality. Results indicate substantial performance differences between systems with significant variations in input air kerma rate to the image receptor. The authors believe that such a protocol is necessary with a view to establishing optimal performance levels and assist in the development of suitable “write-off” criteria for such systems. Key words: Quality assurance – Mobile X-ray equipment – C-arms – Fluoroscopy

Introduction Extensive literature exists on the design and implementation of quality assurance (QA) programmes for diagnostic imaging equipment [1–6]. These programmes assist in ensuring that optimum image quality with miniCorrespondence to: B. Tuohy

mum radiation exposure to patients and staff are obtained in a cost-effective manner [5, 7]. This large body of literature has resulted in widespread interest in the development and application of QA programmes to radiological equipment. This interest has been further enhanced by the European communities Directive on the protection of the patient undergoing medical procedures which involve ionizing radiation, and the consequent national regulations which exist throughout the member states. These regulations require that a QA programme for imaging equipment which emits ionizing radiation be implemented [8]. Fluoroscopic equipment is presently responsible for a highly significant component of medical radiation dose [10, 11]. Physicians and staff members performing these procedures are exposed to relatively high levels of scattered radiation and are sometimes irradiated directly [11]. In particular, the use of mobile C-arm fluoroscopy systems has found increased application in a number of areas which include orthopaedic, vascular and cardiac procedures [10, 11]. Arising from this greater use is the awareness among users of the need for good image quality and minimum radiation exposure to patients and staff. Notwithstanding the above, practically no attention has been paid in the literature to the application of QA programmes to mobile C-arm fluoroscopy systems. This equipment is often omitted from these programmes because it is usually off-site from the main radiological facility and suitable QA protocols are unavailable. In addition to the radiological equipment QA documents cited previously [1–6], a number of IEC and DIN standards have been published which are useful reference material for the development of an approach to QA of mobile C-arm systems (Table 1). In the main, although the IEC standards provide a sound rationale for the application of QA programmes to imaging equipment, little direct attention is focused on the subject of mobile C-arms. The DIN standards provide detailed technical descriptions of various “constancy” and “acceptance” checks which should be performed on X-

B. Tuohy et al.: Quality assurance programme applied to mobile C-arm Table 1. Some DIN/IEC standards applicable to quality assurance (QA) protocol development DIN 6868 (part 4)

Image QA in X-ray diagnostics; constancy checking in fluoroscopy with X-ray image intensifier (1987)

DIN 6868 (part 50)

Image QA in X-ray diagnostics; acceptance testing of medical X-ray equipment for radiography, fluoroscopy and film processing (1990)

BS-EN 61223-2-4

Evaluation and routine testing in medical imaging departments; constancy tests; methods for hard-copy cameras (1995) Evaluation and routine testing in medical imaging departments; constancy tests; methods for image display devices (1995) Medical electrical equipment; general requirements for safety; collateral standard: general requirements for radiation protection in diagnostic X-ray equipment (1995)

BS-EN 61223-2-5

BS-EN 60601-1-3

BS-EN 60601-2-32

Medical electrical equipment; particular requirements for safety; specifications for associated equipment of X-ray equipment (1995)

ray equipment. Again little attention is focussed on Carm systems. In addition, neither the various recommendations from international bodies cited above [1–6] nor the standards listed in Table 1 comprehensively address other areas of concern which have become important during recent years, namely, electrical and mechanical safety [12]. These issues are particularly important in the case of complex interventional procedures in which C-arms find extensive application. From the substantial literature review, a practical QA protocol suitable for routine application to mobile C-arm fluoroscopy systems was developed and is included in the Appendix. The QA protocol was used to assess the performance of ten C-arms in clinical use. This paper presents the principal findings of this study and will show: (a) the need for the application of QA programmes to mobile C-arm systems, so that equipment faults are identified and appropriate corrective action taken; (b) the absence of an agreement among manufacturers regarding acceptable entrance air kerma rates to an image intensifier; and (c) the necessity for developing criteria which establishes the appropriate level of performance at which mobile C-arm fluoroscopy systems should be “written off”. Methods The principal features of the protocol which was developed consisted of the following: 1. A listing of system details which included manufacturer name, model, age and total filtration in the X-ray beam as indicated by the manufacturers. 2. A detailed mechanical safety inspection of the mobile C-arm fluoroscopy systems, which included checking the functionality of all brakes, tube locks and system

535

ease of movement. In addition, the presence of rough or sharp edges was noted. Finally, the presence and functionality of the collimator was checked. 3. Examination of the electrical safety of the units consisted of (a) the general condition of the exposure handswitch, with all plugs and other electrical cables being checked, and (b) the conformity of the C-arm systems to IEC 601.1 [13] was assessed. 4. A radiation safety inspection under three headings: (a) Radiography mode. The protocol addressed the following: radiation output measurement as a function of kV, checks on output consistency, half value layer (HVL) assessment and, finally, kVp and exposure timer accuracy. (b) Image intensifier-TV system (II-TV) assessment. The II-TV systems were assessed with a set of Leeds TV fluoroscopy test objects, which provide both subjective and objective information about an X-ray image intensifier-TV system. Details about the various test objects and the particular parameters assessed are presented in detail elsewhere [14, 15]. The application of the test objects was in accord with the detailed instructions recommended for their correct use as documented in the literature [14, 15]. (c) Fluoroscopic automatic exposure control (AEC). The ability of the system to provide a constant input air kerma rate to the image intensifier independent of the attenuation present in the X-ray beam was assessed. This was accomplished by the addition of increasing thickness of water-equivalent material (5–25 cm H2O) between the X-ray tube and image intensifier. The test equipment used comprised the following: (a) Rigel electrical safety tester (Model 233), (b) MDH 2025 (180 cm3 chamber) dosimeter, (c) RTI, PMX II (kVp and exposure time measurement), (d) Leeds TV fluoroscopy test objects, (e) Hitachi 100MHz-oscilloscope (model VC 6165) and (f) blocks of water-equivalent material (RMI). Results and discussion A total of 10 mobile C-arm fluoroscopy systems were examined in the survey. The systems ranged in age from 3 to 11 years with 70 % of the systems greater than 5 years old. Table 2 presents the salient features of the mechanical safety survey. The mechanical safety of the systems examined was generally satisfactory. However, in 30 % of the systems the collimator failed to function properly (i. e. not closing or opening completely). In two of the three systems with this problem up to 50 % of the image field of view was effected. These problems were due to a mechanical problem in the collimator system resulting in poor control of image collimation, hence undermining image quality and compromising efforts at reducing radiation dose both to the patient and to the staff in the vicinity of the C-arm. The findings of the electrical safety survey were less than encouraging, and in the case of 30 % of the systems

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B. Tuohy et al.: Quality assurance programme applied to mobile C-arm

Table 2. The percent of the total number of C-arms which were judged to have mechanical safety problems Condition

Percent of total

Difficulty in system movement (forward/reverse) Poor function of system brakes Problem with motorised/mechanical C-arm movement Unsatisfactory C-arm locks Damaged visible indicators Presence of rough or sharp edges Problem with collimator

0 10 0 30 10 0 30

investigated, earth leakage currents in excess of 1000 mA were measured. Mobile C-arms find extensive application in the imaging of patients who are undergoing major surgery or complex interventional examinations/procedures (e. g. orthopaedic/vascular surgery or cardiac pacemaker insertion). In many of these procedures the resistance offered by the skin to leakage currents has been reduced significantly or removed, and hence current can gain direct access to a patient’s heart with possible potentially fatal consequences. The radiation output per mAs (mGy/mAs) was a linear function of kV2 for all ten systems, with a correlation coefficient, r, greater than 0.96 in nine of the units examined. In one system, however, the correlation coefficient was 0.93, which is somewhat lower than expected. In this case the output was seen to “level off” at high values of kVp, indicating a problem with the kVp compensation circuitry. The radiation output per mAs at 70 kVp at a distance of 100 cm from the focus is presented in Fig. 1. The mean radiation output is 27 mGy/mAs, which is comparable to the mean output of 12 mobile radiographic machines assessed in a previous study by Tuohy et al. [16], in which the mean output was 39 mGy/mAs at an identical kVp and distance. In addition, there was a lower spread of radiation outputs across the C-arms in the present study in comparison with the data reported by Tuohy et al. [16]. This lower spread is possibly due to the modern high-frequency-type generators in mobile C-arm systems as compared with the older technology available on some old mobile radiographic machines. All mobile C-arms were found to perform consistently over ten repeat exposures at factors of 70 kVp and 20 mAs. The percent coefficient of variation was < 1 % for all systems examined, which is well within established norms reported in the literature [2]. The HVL is a useful parameter in specifying the quality of an X-ray beam [3]. Figure 2 presents the findings of the HVL assessment. The HVL values in mm Al are reported, because they provide a useful indication of beam quality and require less interpretation than estimates of total filtration. Total filtration depends on many factors, such as kV waveform ripple and target angle, and hence may be inadvertently estimated incorrectly [3, 18]. The NCRP [5] specify that the HVL should be greater than 1.5 mm Al at 70 kVp. All of the C-arm systems investigated had HVLs greater than 3 mm Al with one

Fig. 1. Variation in the output of nine mobile C-arm fluoroscopy systems (radiography mode) at 70 kVp and at a distance of 100 cm. The radiography mode had been disabled in one of the ten C-arm systems

Fig. 2. The number of X-ray tubes with various half value layers (HVLs) measured at 70 kVp. In one system, the radiography mode had been disabled and consequently the HVL could not be measured

system greater than 4 mm Al. This is in contrast to similar data for mobile radiographic machines reported in the literature [17], which showed that 83 % of the systems assessed had a HVL between 2 and 3 mm Al. This may reflect an attempt by the manufacturers to reduce the entrance skin dose to the patient in the case of mobile fluoroscopy systems. The accuracies of the selected kVp and exposure times are presented in Table 3. The BIR [2] report an acceptable tolerance of ± 5 % for kVp accuracy and ± 10 % for timer accuracy; 62 % of kVp measurements and 100 % of timer measurements are within the tolerances specified by the BIR. However, 100 % of kVp measurements are within ± 6 % of the selected kVp value. Thus, kVp and exposure timer accuracy in the case of the C-arm systems surveyed is acceptable. The results of the 10 II-TV system assessments are presented in Table 4. Apart from video voltage measurements, the data is subjective because it is based on

B. Tuohy et al.: Quality assurance programme applied to mobile C-arm Table 3. Accuracy of kVp and exposure timer of C-arm fluoroscopy systems (radiography mode) kVp

Time

No. of measurements

60

28

Measurements within ± 5 % of setting

62 %

79 %

Measurements within ± 5 to ± 10 % of setting

38 %

21 %

threshold criteria developed by two of the authors. However, this criteria was consistently applied to all ten systems, and hence some interesting comparisons can be deduced from the data. Measured video voltages range from 242 to 568 mV. From the data no correlation can be found between video voltages and any of the other parameters assessed in the II-TV systems. Thus, the data indicate that video voltages are only useful for monitoring an individual fluoroscopic system with respect to time or in comparison with recommended video levels available from the manufacturers. For the ten systems investigated the resolution limit (lp/mm) ranged from 0.9 to 1.8 lp/mm (see Table 4). The resolution limit for a complete system with a welladjusted 5/6“ image intensifier with a CsI input phosphor should be greater than or equal to 1.6 lp/mm [19]. In the survey 70 % of the systems assessed failed to meet this requirement with 40 % of the systems assessed less than or equal to 1.12 lp/mm. These four systems would be particularly problematic in vascular applications where image resolution limits of the order

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of 1.6 lp/mm are required to visualize small blood vessels. Good correlation was found between focal homogeneity across the entire fluoroscopic image and the respective resolution limit determined for each system. In six systems pincushion distortion was particularly evident and would possibly compromise clinical application, for example in quantitative vascular measurements. Low contrast sensitivity of the systems ranged from 0.033 to 0.066 (see Table 4), with 90 % of the units greater than the recommended threshold contrast, 0.04 [19]. Figure 3 presents the results of the threshold contrast detail detection assessment. The better the imaging performance of a system, the greater the number of lowcontrast and small-diameter details which are visible. Included in the figure is a set of data adapted from Cowen et al. [15] obtained from a 6/5“ mode II-TV system in good adjustment. A curve is fitted to this data. In view of the fact that the results are subjective, it is difficult to make absolute statements regarding the findings. Notwithstanding their subjectivity, the data indicates significant performance variations between the ten systems investigated, and in the main, with one exception, the systems assessed in the survey performed poorly with respect to their ability to detect low-contrast and small-detail diameters, in comparison with what is regarded in the literature as a good system. The findings here also support the data presented in Table 4 where it was found that the low-contrast sensitivity of the systems was poor. Input air kerma rate (mGy/s) to the image intensifier is presented in Fig. 4 for each C-arm system as a function of attenuation (cm H2O). In the main, input air kerma

Table 4. The results of the II-TV system assessment. Results for all test objects are included except TO.10 (contrast threshold detail detectability). In the case of focal homogeneity MS13 implies that wire mesh MS1 is resolvable across the complete image, whereas MS4 X implies that MS4 was not resolvable across the entire image. All C-arms investigated used a 5/6“ image intensifier with a CsI input phosphor System

Video voltage (mV)

Resolution (lp/mm)

1

468

1.8

2

468

1.6

3

462

1.4

4

470

1.12

5

550

1.4

6

242

1.12

7

568

1.8

8

326

1.12

9

280

1.25

10

382

0.9

Focal homogeneity MS1 3; MS3 3; MS4 3 MS1 3; MS3 3; MS4 X MS1 3; MS3 3; MS4 X

MS1 3; MS3 X; MS4 X

MS1 3; MS3 3; MS4 X MS1 3; MS3 3; MS4 X MS1 3; MS3 3; MS4 3

MS1 3; MS3 X; MS4 X

MS1 3; MS3 3; MS4 X

MS1 3; MS3 X; MS4 X

Geometrical distortion (pin cushion)

Low-contrast sensitivity

Significant

0.055

Significant

0.055

Slight

0.045

Significant

0.055

Slight

0.055

Slight

0.033

Significant

0.055

Slight

0.045

Significant

0.055

Significant

0.066

538

Fig. 3. Threshold contrast detail detectability data for the ten mobile C-arm fluoroscopy systems assessed in the survey. The curve is fitted to a set of data adapted from the literature for a system in good adjustment. (From [15])

Fig. 4. Input air kerma rate plotted as a function of attenuation present in the X-ray beam

rate decreases with increasing attenuation in the X-ray beam; however, when the TV camera video signal was monitored, its value was generally seen to remain constant. This finding is generally in line with the design of modern automatic exposure control (AEC) facilities. These devices in conjunction with the AEC facility incorporate some form of automatic gain control (AGC) in the TV camera, so that a constant level of image brightness is maintained on the monitor. In two systems (4 and 10), however, the AEC facility did not perform satisfactorily with the input air kerma rate falling practically to zero at moderate attenuation levels. The AGC also in these cases failed to function correctly resulting in very serious degradation of image quality. These particular systems were therefore used clinically in a manual operating mode, possibly giving rise to higher patient radiation doses than would be the case if the AEC

B. Tuohy et al.: Quality assurance programme applied to mobile C-arm

system had been functioning correctly. Furthermore, it is clear that little or no QA was performed on these particular AEC devices. For a typical patient attenuation of 20 cm H2O, entrance air kerma rate to the II varies by a factor close to six across the range of systems investigated (system 10 is excluded in this comparison because air kerma rate was 0 at 20 cm H2O). Thus, there seems to be no agreement among manufacturers on AEC design or an appropriate input air kerma rate to the image intensifier. As discussed previously there is a vast body of literature concerned with the development and application of QA programmes to diagnostic imaging equipment. However, no sufficiently sophisticated set of criteria exist to aid in the “write-off” of fluoroscopy equipment in practice. A significant number of systems assessed in this survey produced entrance air kerma rates (dependent on attenuation present) to the image intensifier which exceed recommended values reported in the literature, e. g. 0.9 mGy/s [3]; however, these systems still find clinical application. In addition, several systems exhibited poor image quality (Fig. 2; Table 4); however, no studies appear to exist which relate image quality indices, as determined by the Leeds test objects, to the clinical performance of a fluoroscopy system as judged subjectively by a physician. Criteria which combine these two facets remain to be developed and are the source of further work in this area for our group. This developmental work will greatly assist in providing suitable “write off” criteria, because presently the absence of such criteria, coupled with the strong financial arguments against replacing equipment, renders it extremely difficult to “write off” fluoroscopy systems in practice. The QA protocol developed during the course of this study addresses an obvious deficiency in the published literature in this area. It provides a practical approach to the routine testing of such systems, which may be implemented at a comprehensive level by technical staff attached to radiology departments. A modified version of this protocol, e. g. with the removal of video voltage and electrical safety measurements, could be implemented on a routine basis by radiography staff employed by these departments. Both of these approaches are necessary to maintain good image quality with low radiation doses to both patients and staff. In addition, the implementation of such programmes satisfies the requirements of the European directive on the protection of the patient [8]. Conclusions Little attention has previously been paid to QA of mobile C-arm fluoroscopy systems. This paper indicates the need for the application of comprehensive QA programmes to this type of equipment. These programmes should include mechanical and electrical safety in addition to the more traditional element of radiation safety. In the survey many problems and some potentially seri-

B. Tuohy et al.: Quality assurance programme applied to mobile C-arm

ous faults were identified; their correction will result in increased patient and/or operator safety, improved image quality and reduced radiation exposure to patients and staff. The programme presented in this paper provides a useful QA protocol for mobile C-arm fluoroscopy systems. In addition, it has potential application in monitoring service contracts performed by equipment suppliers. Significant performance variations with respect to image quality were observed in the study. Image quality indices which combine the results obtained from II-TV system assessments using fluoroscopy test objects and the impact these results have in practice as judged

539

subjectively by a physician require development, so that a suitable “write off” criteria based on both image quality and entrance air kerma rate to the patient/image intensifier can be developed. Acknowledgements. The authors thank Dr. G. Wilson and the Diagnostic Imaging Department, St. James’s Hospital, Dublin, for their cooperation. The authors also thank those who supported the work reported in this paper, and in particular. Dr. Lesley Malone, Mr. P. Kenny and Mr. P. Gilligan. This work was supported in part by the commission of the European Communities, Radiation Protection Research Programme (contract no. F13P-CT920014).

Appendix 1. Equipment details

Manufacturer

Model

Serial no.

X-ray tube Model: Serial no. Target angle Filtration

2. Equipment location 3. Mechanical safety

Ease of movement

Safety Brakes

Collimator function

4. Electrical safety

Condition of all cables

Mains plug wiring

Motorised movement

Sharp edges

C-arm locks

Availability of earth reference terminal on system

Visible indicator

Condition of exposure handswitch

Earth leakage current, enclosure leakage current and earth bonding measurement Normal conditions (0.5 mA) Equipment on

(Normal

X-rays on

(Normal

F) F)

(Reverse (Reverse

F) F)

Single fault conditions (1 mA) (Normal (Normal

Earth bonding measurement (< 0.1

W ):

F) F)

(Reverse (Reverse

F) F)

5. Radiation safety A. Radiography mode (i) Radiation output (d = 50 cm; mAs = 20) kV Select O/P (mGy/mAs) 50 60 70 80 90 100 110 120

(ii) Radiation output consistency Factors: 70 kVp, 20 mAs, d = 50 cm Measurement O/P (mGy) 1 2 3 4 5 6 7 8 9 10 Mean =

(iv) Radiation output vs exposure time Factors: 70 kVp; 100 mA Exposure time O/P (mGy/mAs)

(iii) Radiation output vs tube current Factors: 70 kVp, exposure time = 0.1 s I (mA) O/P (mGy/mAs) 50 75 100 125 150

Std. Dev. = cv% =

(v) Kilovoltage/timer accuracy (both kV and time vary) Set kV Set time measured kV measured time

(vi) Half value layer assessment (mm Al) Factors: 70 kVp; 20 mAs Filtration (mm Al) O/P (mGy) 0 1 2 3 4 5

540

B. Tuohy et al.: Quality assurance programme applied to mobile C-arm

5 B. Image intensifier system assessment I. II-TV system details II. System set-up details

Cu filter present

Manual/auto screening

Source intensifier Added filtration distance

Tube current (mA)

I. I. Entrance exposure rate

III. Video voltage test object (E1)

Sync. pulse (mV)

Pedestal (mV)

Signal voltage (mV)

Peak noise amplitude (mV)

Vignetting (l, r)

IV. Grey-scale test object (GS2)

Number of grey-scale steps visible

Blk level – Wht edge (mV)

Are black and white discs visible?

Does the monitor require adjustment?

V. Low-contrast Number of discs visible cut-off test object (N3) VI. Contrast detail test oblect (TO 10)

Number of discs visible in each row A

B

C

VII. Field coverage test object M1

Field 1: cm horizontal

VIII. Limiting resolution test object – Huttner

Remove copper filter,

IX. Uniformity of focus, MS1, MS3, MS4

MS1

D cm vertical

E

F

G

Field 2: cm horizontal

H cm vertical

J

K

Field 3: cm horizontal

L

M cm vertical

Any pin cushion or geometric distortion of image present? Number of groups visible New kVp = Limiting resolution = MS3

MS4

5 C. Automatic exposure control (AEC) function Does the AEC system operate (a) fully automatically (b) fully manually or (c) combination of (a) and (b)? X-ray beam attenuation (cm H2O) 0 5 10 15 20 25

References 1. WHO (1982) Quality assurance in diagnostic radiology. World Health Organisation, Geneva 2. BIR (1988) Assurance of quality in the diagnostic X-ray department. British Institute of Radiology, London 3. HPA (1980) Measurement of the performance characteristics of diagnostic X-ray systems used in medicine, parts 1-VI. TGR-32. Hospital Physicist Association, London 4. AAPM (1988) Protocols for the radiation safety surveys of diagnostic radiological equipment. Report no. 25. American Association of Physicists in Medicine, New York 5. NCRP (1988) Quality assurance for diagnostic imaging equipment. Report no. 99. National Commission for Radiological Protection, Bethesda 6. AAPM (1985) Performance evaluation and quality assurance in DSA. Report no. 15. American Association of Physicists in Medicine, New York 7. Moran B, Upton J, Malone JF (1995) A practical approach to a quality assurance programme for radiography at the constancy check level. Radiat Prot Dosim 57: 1–4, 263 8. CEC (1984) Council directive laying down basic measurements for the protection of persons undergoing medical examination or treatment (84/466 Euratom). Off J Eur Comm 27: 1–3

Input air kerma to image intensifier

9. Malone JF, Cooney P, Busch HP, Faulkner K (1995) A review of the background to the decision to write off fluoroscopy equipment in 15 instances – and the impact of patient dose and image quality in practice. Radiat Prot Dosim 57: 1–4, 249 10. NRPB (1990) Patient dose reduction in diagnostic radiology. Documents of the NRPB 1: 3. National Radiological Protection Board, Didcot 11. Goldstone KE, Wright H, Cohen B (1993) Radiation exposure to the hands of orthopaedic surgeons during procedures under fluoroscopic X-ray control. Br J Radiol 66: 790 12. IPSM (1995) Electrical and mechanical safety. In: Faulkner K, Jones AP, Walker A (eds) Safety in diagnostic radiology, Institute of Physical Scientists in Medicine, York, UK 13. IEC (1988) Medical electrical equipment, part 1: general requirements for safety IEC 601.1. International Electrotechnical Commission, Geneva 14. Hay GA, Clarke OF, Coleman TNJ, Cowen AR (1985) A set of X-ray test objects for quality control in television fluoroscopy. Br J Radiol 58: 335 15. Cowen AR (1994) The physical evaluation of the imaging performance of television fluoroscopy and digital fluorography systems using the Leeds X-ray test objects: a UK approach to quality assurance in the diagnostic radiology department. In: Seibert JA, Barnes GT, Gould RG (eds) Specification, acceptance testing and quality control of diagnostic X-ray imaging

B. Tuohy et al.: Quality assurance programme applied to mobile C-arm equipment. Medical Physics Monograph no. 20. American Association of Physicists in Medicine, New York 16. Tuohy B, Tuohy G, Cooney P, Moran B, Malone JF (1995) Quality assurance programme applied to mobile X-ray equipment. Radiat Prot Dosim 57: 1–4, 241 17. Tuohy B, Tuohy G, Cooney P, Moran B, Malone JF (1993) Quality assurance programme applied to mobile X-ray equip-

Book reviews

541 ment. In: Proceedings of Radiation Protection in Diagnostic Radiology. Grado, Italy 18. Cranley K, Fogarty GWA (1988) The measurement of total filtration of diagnostic X-ray tubes. Br J Radiol 61: 388 19. DHSS (1982) The testing of X-ray image intensifier television systems. STB/7/82 Department of Health and Social Services, London

European Radiology

Meholic A., Ketai L., Lofgren R.: Fundamentals of Chest Radiology. Philadelphia: W. B. Saunders Company 1996, 255 pages, over 250 illustrations, (ISBN 0-7216-5400-2), US $ 38.00

Weill F. S. : Ultrasound Diagnosis of Digestive Diseases. 4th revised edn. Berlin, Heidelberg, New York, Springer 1996. 743 pp., 969 illustrations, (ISBN 3-540-60412-X), DM 298,00.

Written for novice radiology residents and residents in family practice and internal medicine, this new addition to the Fundamentals of Radiology series is concise yet comprehensive. Fourteen chapters bring the reader from basics, normal variants, and artifacts through all anatomic compartments of the chest. Radiographic anatomy, technical modifications of chest roentgenography relevant in the clinical setting as well as classical signs (such as the silhouette sign and air bronchogram) are discussed. As compared with similar basic textbooks of chest radiology, however, computed tomography and magnetic resonance imaging are introduced with important technical modifications, artifacts, selected normal anatomy, and recognized clinical indications. Important factors relating to one problem are regularly summarized in tables. The main section presents chest pathology by anatomic areas, starting with the airways, i. e. large airway disease and obstructive pulmonary disease. The subsequent six chapters discuss lung parenchymal disease with an introductory basic terminology (airspace disease, interstitial disease, and atelectasis), traumatic and toxic disease, infectious lung disease, pneumoconioses and immunologic lung disease, neoplasms and developmental lesions, and intraparenchymal vascular lesions. The final four chapters deal with the pleura and diaphragm, cardiovascular disease, the hilum and mediastinum, and the chest wall. The relative weight of subjects within the volume is clinically adequate; all important entities are covered as well as some rare situations where imaging plays a special role. The reader will easily find the requested information based on either the chapters and headings or on the extensive index. Illustrations are of mostly excellent quality; legends and the main text are written fluently and invite the reader to enjoy reading the textbook continuously. There are no logical, and hardly any orthographic, errors (threshold diameter of descending right pulmonary artery 16 mmHg instead of 16 mm). Minor criticism will include the composition of chapters (e. g., neoplasms and developmental lesions in one chapter; vascular lesions integrated in several chapters), the lack of a bibliography, and some of the diagnostic algorithms. However, in order to be clear, the authors tried to simplify the diagnostic decision tree; their approach is reasonable but will not be identical to the reality practiced in many cooperative teams of pulmonary specialists, internists, thoracic surgeons, and radiologists. When compared with the many advantages, these few weak points can certainly be disregarded. In conclusion, I recommend this book without hesitation for any medical doctor who wants to get acquainted with chest radiology beyond the level of medical school and who wants to interpret chest radiographs. Even practicing radiologists may well go back and enjoy reading this concise introduction text. P. Vock, Berne

This is the fourth edition of this classic text by Francis Weill, one of the pioneers of abdominal US. Eighteen years have elapsed since the first edition appeared (in 1978), and the book still holds up. The reader is offered a huge number of separate illustrations, 2651 in all, captioned with the well-known flamboyant, albeit verbose, comments of the author. Weill’s English is excellent and effective, and a few unfamiliar terms, such as “hydropancreatosis” and “aeroportia,” are amusing rather than disturbing. The US images are of moderate quality, many of them unchanged from the first edition. The few color-Doppler images are disappointing for reasons of poor quality. Throughout the book there is strong emphasis on the isolated US image with too little correlation to CT scan or barium studies and too little attention to clinical relevance of the US findings. The US images appear to live a life of their own when the author offers over 40 images of normal gallbladders or classifies liver metastases and cirrhosis into countless patterns without any obvious clinical need. There is also an imbalance of clinical relevance: A total of 69 images of echinococcosis – a relatively rare disease – is shown for only two images of such a common and important entity as sigmoid diverticulitis. The 31 chapters are arranged in a disorderly and haphazard manner, and several conditions are dealt with more than once under different headings. Typical are the separate chapters ”Jaundice“ and ”Biliary lithiasis“ and the title of yet another chapter, which reads ”Other nonpancreatic masses, mainly retroperitoneal.“ In view of the book’s title one can understand that in the chapter ”Acute abdomen“ urological and gynecological conditions are only superficially dealt with, although this remains somewhat artificial. However, it is surprising to see that other nondigestive conditions, such as splenic trauma, psoas hematoma and aortic aneurysm, are extensively discussed. In view of its classic aura, this book will undoubtedly find its way to the reader, and the individual who is prepared to search will find much useful information in the wealth of illustrations provided by an obviously experienced sonographer. However, 18 years have passed since the birth of the first edition and many textbooks on abdominal US, competitive in both price and content have appeared. In view of this I am not sure that this book is a good value for the money. J. B. C. M. Puylaert, Den Haag