Exploring the useful exposure range limits of three intraoral image receptors for various tube potential, tube current and exposure time settings

doi:10.4236/health.2011.35051

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Vol.3, No.5, 292-299 (2011)

doi:10.4236/health.2011.35051

Health

Exploring the useful exposure range limits of three

intraoral image receptors for various tube potential,

tube current and exposure time settings

Elli Katsoni1*, Ioannis A. Tsalafoutas2, Panagiotis Gritzalis3, Evripides Stefanou3,

Evangelos Georgiou1, Emmanouel Yakoumakis1

1Department of Medical Physics, Medical School, University of Athens, Athens, Greece;

*Corresponding Author: jzar@rocketmail.com

2Medical Physics Department, Agios Savvas Hospital, Athens, Greece;

3Department of Oral Diagnosis and Radiology, Dental School, University of Athens, Athens, Greece.

Received 28 February 2011; revised 20 April 2011; accepted 4 May 2011.

ABSTRACT

Objectives: To determine the useful exposure

range limit s of three intraoral image r eceptors of

different technology when exposed to different

X-ray beam spectra, dose and dose rate levels.

Study Design: A dental X-r ay unit offering a wide

range of tube potential, tube current and expo-

sure time settings was used to expose a dental

quality control phantom. The receptors that

were used to capture the radiogr aphic im ages of

the phantom were: the Kodak Insight, the Koda k

RVG-6000 and the Duerr Vistascan system. The

images that were produced over a wide range of

exposure factor settings were evaluated in

terms of dia gnostic qual ity by three e xperienc ed

radiologists. Results: The number of images

with acceptable diagnostic quality was in total

1257; 310 with Insight, 331 with RVG 6000 and

616 with Vistascan. At 60 kV, diagnosable im-

ages were produced with doses ranging from

0.44 - 1.56 mGy for the Insight film 0.44 - 2.82

mGy for the RVG 6000 and 0.22 - 4.93 mGy for

the Vistascan system. At 70 kV, the respective

ranges were 0.39 - 1.28 mGy for the Insight film

0.31 - 2.55 mGy for the RVG6000 and 0.30 - 3.46

mGy for the Vistascan system. Conclusions:

The Vistascan exhibited the widest useful ex-

posure rang e an d r equ ir ed th e l eas t ex pos ur e to

produce a diagnosable image at almost all tube

potential settings. The RVG 6000 exhibited a

slightly wider useful exposure range than the

Insight film, with almost the same dose re-

quirements especially in higher Kv settings.

Keywords: Radiography, Dental, Digital; Dosage

1. INTRODUCTION

According to the UNSCEAR 2000 Report, dental in-

traoral radiography is among the most frequently per-

formed radiological procedures [1]. Although the patient

exposure associated with dental radiography is relatively

low, intraoral radiography should be optimised in order

to keep the radiation risk “as low as reasonably achiev-

able”, something that is widely known as the ALARA

principle [2].

Over the past 20 years both the X-ray units and the

X-ray receptors used in dental radiology have been

evolved. Modern dental X-ray units incorporate high

frequency generators, operate at higher tube potentials

and produce X-ray spectra that have higher mean energy

and therefore are more penetrating compared to those

produced by older dental X-ray units. These improve-

ments have contributed in the reduction of the radiation

dose to the entrance skin surface of the patient and the

enhancement of image quality. Concerning the X-ray

receptors, new digital systems have been introduced in

to the clinical practice and nowadays digital radiography

is considered an accepted imaging technique in dentistry.

Currently, solid-state detectors based on CCD or CMOS

technology, photostimulable storage phosphor (PSP)

systems, along with the old-fashioned but still widely

used silver halide based films, are commercially avail-

able for intraoral radiography.

In the international literature many remarkable articles

can be found describing digital receptor systems and

presenting comparisons among various systems with

regard to their diagnostic performance [3-7]. Their re-

sults, however, have been derived using a limited range

of exposure factors, despite the fact that the response of

films and solid state or PSP receptors is dependent on

the energy spectrum of the X-ray beam used and the

E. Katsoni et al. / Health 3 (2011) 292-299

293293

dose levels to which they are exposed. The influence of

the exposure factors on the performance of dental re-

ceptors of different technologies has not yet been inves-

tigated extensively.

The purpose of this study was to comparatively evalu-

ate, in a systematic inter-equipment manner, the useful

exposure range of three intraoral image receptors which

are representative of the currently available technologies,

when exposed to different X-ray beam spectra, dose and

dose rate levels.

2. MATERIAL AND METHODS

A modern dental X-ray unit (Prostyle Intra DC, Plan-

meca Oy, Helsinki, Finland) was used, offering eight

tube potential settings (ranging from 50 to 70 kVp),

seven tube current settings (ranging from 2 - 8 mA) and

26 exposure time settings (ranging from 0.01 to 3.2 sec).

The nominal total filtration was 2 mm Al and the focus

to collimator end distance was 30 cm.

A calibrated ion chamber dosimeter (Dosimeter 9010,

ionization chamber type 90x6-6; Radcal Corporation,

Monrovia, USA) positioned at 30 cm from the tube fo-

cus was used to measure the dose in free air and deter-

mine the tube output at that distance. These measure-

ments were carried out for all the available tube potential,

tube current and exposure time selections, in order to

identify possible variations in output with different tube

loading values. The tube potential accuracy and repro-

ducibility were checked using a calibrated kilovolt peak

meter (Gammex RMI 245, Gammex Inc., Middleton,

USA).

The intraoral radiographic receptors evaluated in this

study were: the Kodak Insight F speed class film (East-

man Kodak Company, Rochester, NY), the Kodak RVG

6000 (Eastman Kodak Company, Rochester, NY), and

the Duerr Vistascan Combi PSP system (Duerr Dental,

Bietingsheim-Bissingen, Germany). The main technical

characteristics of the systems tested are summarized in

Table 1.

A cylindrical Perspex based phantom (Dental Image

Quality Test Tool, model 76025; Nuclear Associates,

Division of Victoreen, Inc, Carle Place, NY) was used

for the evaluation of image quality [8]. This phantom

contains a real human tooth in the centre and around it

three cylindrical air filled holes of different height. In the

periphery of the phantom four wire meshes of different

wire thickness are included. Finally, the phantom has a

slot in order to fit in the various image receptors. A pho-

tograph and a radiographic image of the phantom are

shown in Figure 1 and Figure 2, respectively.

The phantom was attached to the collimator end and

the image to receptor distance was kept constant at 35 cm.

The phantom was radiographed using all the image re-

ceptors and for each receptor all the tube potential, tube

current and exposure time combinations possible. Thus,

1456 exposures were required for each image receptor in

total.

The films were processed immediately after exposure,

with an automatic processor (Velopex Extra-X, Medivance

Instuments, England) using the Readymatic dental de-

veloper and Readymatic dental fixer solutions (Eastman

Kodak, Rochester NY), at a temperature of 27˚C. This

processor features an automatic replenishment system,

however, in order to ensure that the processing condi-

tions remain fairly constant during the experiments, the

processing stability was repeatedly tested every 50 films

using sensitometry (Pehamed densitometer Densinorm

21, PEHA med. Geräte GmbH Sulzbach, Germany). The

acquired film radiographs were mounted in opaque plas-

tic holders and coded for later use. The film radiographs

were evaluated on a viewing box, with all extraneous

light masked.

For the Vistascan the PSP image plates were unpacked

in a dimly lit room and scanned immediately after expo-

sure, using the Vistascan Combi system [9,10]. The

scanner’s resolution pitch settings were adjusted to 12.5

μm (corresponding to a theoretical resolution of 40 line

pairs per mm). Concerning the RVG 6000 the original

software of the system was used for image capture. No

image processing was performed to enhance image qual-

ity other than the system’s default pre-process.

All digital images were viewed in fit to screen mode

Table 1. Specifications of the systems.

Model ManufacturerPixel Size

(μm) Technology Software Size Bit/PixelWidth

(Pixel)

Height

(Pixel)

File Size

(MB)

INSIGHT KODAK N/A SILVER

HALIDE N/A 2 N/A 3.1 (cm) 4.1 (cm)N/A

RVG 6000 KODAK 18.5 × 18.5 CMOS

KODAK

WINDOWS

6.0.1

1 8 1200 1600 1.8

PSP VISTASCAN DUERR SCAN PITCH

12.5 IMAGE PLATEDBSWIN V.3.32 16 2476 3195 Up to 9.3

E. Katsoni et al. / Health 3 (2011) 292-299

294

Figure 1. Photograph of the phantom used for the evaluation

of image quality.

Figure 2. Radiographic image of

the phantom used for the evalua-

tion image quality.

on a 19-inch TFT monitor (Sony SDMHS95PR), with

1280 × 1024 resolution under subdued lighting conditions.

The monitor’s brightness and contrast were adjusted

using the SMPTE (Society of Motion Picture and Tele-

vision Engineers) test pattern [11,12].

All the images acquired were evaluated by three ex-

perienced radiologists in the department of Oral Diagno-

sis and Radiology of the Dental School of the University

of Athens. For each image, the observers evaluated the

cementoenamel junction, the dentoenamel junction, the

root canals and the apical region of the tooth, as well as,

the perceptibility of the three holes and the four

wire-mesh areas included in the phantom. An image was

considered to have adequate diagnostic quality when all

the aforementioned anatomical characteristics of the

tooth were properly imaged and additionally the holes

and the wire meshes were discernible. It had been de-

cided that in case of disagreement among the observers,

the images in question would be reviewed for a second

time and if disagreements were not resolved, the opinion

of the majority would be adopted.

3. RESULTS

The output measurements revealed that the linearity of

output was within accepted limits at all tube potentials,

even though for small tube loadings ( 0.5 mAs) a re-

duction in output of up to 20% was observed with re-

spect to the mean value of output over the whole mAs

range. The reproducibility of output using the same ex-

posure conditions was found to be better than 1%. The

tube potential accuracy and reproducibility were found

better than 3% and 1%, respectively.

For all the images of acceptable quality, the receptor

type, the exposure factors (kV, mA, s) were noted and

the respective entrance surface air kerma (ESAK) values

at the phantom were then assigned. Examples of such

images derived for a given combination of tube potential

and tube current and varying exposure time, are embed-

ded in Table 2, which is indicative of the differences

observed among receptors with respect to their useful

exposure range.

Concerning the images of insufficient quality that

were considered non-diagnosable, these included the

under and over exposed films and those digital images in

which the appearance of the phantom resembled those of

over or under exposed films, as well as, digital images

with excessive noise or other artifacts (partial inversion

of the greyscale in parts of the image, blooming effects

etc).

The number of images with acceptable diagnostic

quality was in total 1257; 310 with Insight, 331 with

RVG 6000 and 616 with Vistascan. An overview of the

useful exposure range of all receptors is presented (Fig-

ure 3). In this figure the exposure range of each receptor

is presented with respect to the nominal mAs (left side)

and the ESAK (right side), for all tube potential settings.

For reasons of straightforward comparison among re-

ceptors in all insert figures the same axis scale was used.

From Figure 3, it is obvious that the VistaScan PSP sys-

tem exhibited by far the most extended useful exposure

range for all the tube potential values used. Furthermore,

it required the least dose to produce a diagnosable image

at all tube potentials except 50 and 55 kV, where the

Insight film required less and exactly the same ESAK,

respectively. The second wider useful exposure range

was exhibited by the RVG 6000. However, it required a

slightly higher minimum ESAK to produce a diagnos-

able image compared to the Insight film, except from 60

and 70 kV where the RVG 6000 required exactly the

same and less dose, respectively. The Insight film exhib-

ited a relatively limited useful exposure range but in

terms of the minimum ESAK required to produce a di-

agnosable image, it was the second after the Vistascan.

Indicatively at 60 kV the useful exposure ranges of the

VistaScan PSP, RVG 6000, Insight and were 0.22 - 4.93,

0.44 - 2.82 and 0.44 - 1.56 mGy, respectively. At 70 kV,

the respective ranges 0.30 - .46 mGy, 0.31 - 2.55 mGy 3

E. Katsoni et al. / Health 3 (2011) 292-299

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Table 2. Images with satisfactory image quality obtained at 70 kV and 4mA with the three different receptors. The exposure time and

the respective ESAK are given in the bottom rows.

Insight

RVG 6000

Vistascan

sec 0.1 0.125 0.16 0.20 0.25 0.32 0.4 0.5 0.64 0.8 1

mGy 0.33 0.41 0.53 0.67 0.83 1.07 1.34 1.68 2.16 2.70 3.38

Figure 3. The useful exposure range of the three receptors studied is given for all tube.

E. Katsoni et al. / Health 3 (2011) 292-299

296

and 0.39 - 1.28 mGy.

One may notice that a discrepancy exists among the

width of useful exposure ranges of Insight film and the

RVG 6000 as shown in Figure 3 and the respective

number of diagnosable images mentioned above. This is

due to the fact that RVG 6000 exhibited a dependency

on the dose rate, since for a specific tube potential set-

ting and different mA selections, the same ESAK some-

times produced a diagnosable image and sometimes a

non-diagnosable image. This can be seen in Figure 4

where the useful exposure range is given for each tube

loading setting separately, for tube potentials settings of

60 and 70 kV, which are the most frequently tube poten-

tial settings encountered in modern X-ray units. In this

figure it can be seen that RVG 6000 exhibited a better

response at low dose rates (i.e. lower mA settings).

Concerning the images of insufficient quality, these

included the under and over exposed films and those

digital images in which the appearance of the phantom

was resembling this of over or under exposed films and

images with excessive noise and artifacts. Some charac-

teristic examples of the non diagnosable images and er-

ror images obtained with the three receptors have been

gathered in Figures 5(a) to 5(h).

It can be seen that while in Figure 5(a) the appear-

ance of the digital image obtained with the RVG 6000

receptor was similar to that of an overexposed film, fur-

ther increase of the exposure time produced the noisy

image of Figure 5(b), in which the greyscale was auto-

matically inverted. A similar situation is presented in

Figures 5(c) to 5(e). With tube potential and tube current

constant, starting from a digital image that was looking

like an overexposed film (Figure 5(c)), further increase

of the exposure time produced initially an image that

was almost black (Figure 5(d)) and then an image where

the phantom structures reappeared to some extent but

with inverted greyscale (Figure 5(e)).

In Figures 5(f) and 5(g) the appearance of an under-

exposed and an overexposed image with the Vistascan

receptor, respectively, are shown. Finally, in Figure 5(h)

Figure 4. The useful exposure range of the three receptors studied is given for each one of the tube current settings used, for a tube

loading of 60 (left figure’s side) and 70 kV (right figure’s side). Each diagnosable image is represented by a data point.

E. Katsoni et al. / Health 3 (2011) 292-299

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(a) (b) (c) (d)

(e) (f) (g) (h)

Figure 5. Examples of images that were rejected due to lack of image quality and error images that when the exposure was repeated

they resulted in diagnosable images. Rejected images with the RVG 6000 receptor; (a) 50 kV, 8 mA, 1.6 sec, (b) 50 kV, 8 mA, 2.5 sec,

(c) 63 kV, 8mA, 0.64 sec, (d) 63 kV, 8mA, 0.8 sec, (e) 63 kV, 8mA, 1.6 sec. Vistascan (f) - (g), f) 70 kV, 8mA, 0.01 sec (g) 70 kV,

3mA, 3.2 sec, (h) 55 kV, 8mA, 0.01 sec. Error images with the RVG 6000 (k) receptor.

an error with the RVG 6000 receptors is shown. This

error was attributed to some kind of “fatigue” that the

detectors may have experienced during successive ex-

posures.

4. DISCUSSION

Diagnosable image refers to a quality radiograph in

which the examined anatomic structure is captured with

fidelity. Image quality describes the subjective judgment

by the clinician of the overall appearance of a radiograph.

It combines the features of density, contrast, latitude,

sharpness, resolution and perhaps other parameters.

Various mathematical approaches have been used to

evaluate these parameters further, such the detective

quantum efficiency (DQE) that encompasses image con-

trast, blur, speed and noise. Often a system can be opti-

mized for one of these parameters, but this is usually

achieved at the expense of others. However, more in-

formation is needed for complete understanding of all

the factors responsible for the subjective impression of

image quality. Three main factors that control quality are

receptor characteristics, geometric factors and subject

characteristics.

The wide exposure range of the storage phosphor

technology receptors, well known from their applica-

tions in general radiology, has been also confirmed in the

dental field [13-17]. The phosphor plate systems can

accommodate exposure times which are close to or at the

end of the electronic timer range of many commercially

available X-ray units. Since the radiographs from the

Vistascan receptor remained diagnosable from very low

to very high values of tube loading for all tube potential

values, no re-takes will be normally needed when this

type of receptor is used. On the other hand, it is also true

that with receptors of this type, higher doses than those

actually needed for diagnosis can be systematically used,

something that from the aspect of radiation protection is

considered disadvantageous and in general radiology it

has been reported as “the exposure factor creep” [18].

Concerning the minimum exposure that could give a

diagnosable image, as it can be seen in Figure 3, differ-

ences were observed among the three receptors tested,

especially for the lower kV settings used. However, for

the larger tube potential settings these differences were

quite smaller. At 70 kV the minimum required ESAK

value was about 0.3 mGy for the Vistascan and the RVG

6000, and about 0.4 mGy for the Insight. Regarding the

variation of the minimum ESAK required to produce

diagnosable images with the different tube potential set-

tings, the smallest variations were observed for Insight

(0.35 - 0.44 mGy) and the Vistascan (0.31 - 0.48 mGy).

The manufacturers of digital radiographic systems of-

E. Katsoni et al. / Health 3 (2011) 292-299

298

ten claim that their systems offer a reduction in patient

exposure when compared to films. In the literature it is

also generally accepted that the patient dose is generally

lower in digital than in conventional film based intraoral

radiography with films of E-speed class [19-21]. How-

ever, in this study only the Vistascan produced diagnos-

able images at lower doses than the Insight film in all

tube potentials except at 50 kV, where it required more

dose and at 55 kV where it required exactly the same

dose.

The dependence of the response of RVG 6000 on the

dose rate was another interesting finding of this study.

The limitation of the useful exposure range of the RVG

6000 observed with the increase of tube current settings,

could be in part attributed to the difficulty of the receptor

controlling, in a linear and reproducible way, the ex-

tremely short exposure times.

European guidelines, in the context of the ALARA

principle, have recommended the establishment of diag-

nostic reference levels (DRLs) in dental radiography

[22]. Relevant surveys conducted in Greek dental radio-

graphic facilities over the last 10 years have demon-

strated a trend for reduction of the entrance surface dose

[8,23]. Hatziioannou et al. had suggested a DRL of 3.5

mGy for the intraoral dental equipment operating in

Greece [24]. However, in a recent study Gonzalez et al.,

have suggested a reference value of 1.8 mGy for E/F

speed class films and 0.6 mGy for the digital image re-

ceptors [25].

In this study it was shown that for the specific phan-

tom used, the Kodak Insight F speed class film required

doses quite smaller than the typical value suggested by

Gonzalez et al. [25] to produce images of satisfactory

diagnostic quality. On the other hand, regarding the

digital receptors the entrance dose of 0.6 mGy proposed

by Gonzalez et al. was outside the lower limit of the

useful exposure range of the RVG 6000 at tube poten-

tials of 50, 55 and 57 kV [25]. It is therefore obvious that

since the minimum dose required is strongly dependent

on the tube potential selection, any reference or DRL

values should also specify the tube potential range to

which they apply.

Since the vast majority of the dental X-ray units of

those commercially available and those currently in use

worldwide, offer a single or at best two tube potential or

tube current settings, it should not be taken for granted

that these are compatible with all commercially available

digital receptors.

Most modern dental X-ray units operate at a tube po-

tential value in the range of 60 to 70 kV. However, many

of them have only one tube current value setting that is

usually 7 mA and therefore, if combined with a digital

receptor of limited exposure range, only the very short

exposure time settings in the range of 0.1 to 0.3 sec

could be utilized for tube potentials larger than 60 kV

(assuming that these X-ray units have an output and a

total filtration similar to that of the unit used in this

study and that the same focus to receptor distance is

used). This problem will be more pronounced in dental

X-ray units with shorter collimators offering a minimum

focus to skin distance of about 20 cm (which is the case

for the majority of dental X-ray units), where only two

or three exposure time selections smaller or equal to 0.1

sec may be available for producing a diagnosable image.

However, in X-ray units which offer a tube current

around 4 mA as the standard or as an alternative selec-

tion, a wider range of exposure time settings can be util-

ized.

The differences observed in the useful exposure range

of the receptors tested, suggest that manufacturers

should include in the technical data sheets relevant in-

formation concerning the useful exposure range of their

receptors in terms of tube potential, ESAK and ESAK

rate in reference to a dental phantom (like this used or

any other that could serve as a reference dental phantom).

In this way the potential user would be able to determine

if a given receptor is compatible with the dental X-ray

unit that may already have and furthermore he/she would

be able to compare receptors using a performance index

that relates to the clinical practice and therefore is easy

to comprehend.

5. CONCLUSIONS

In conclusion, Vistascan presented the widest useful

exposure range compared to the RVG 6000 and the In-

sight film. At almost all tube potentials Vistascan re-

quired the least dose to produce a diagnosable image,

something that clearly is an advantage. On the other

hand, Vistascan could produce diagnosable image with

doses twice or three times the upper limit of the useful

exposure range of the RVG 6000 and the Insight, some-

thing that in the hands of an untrained dentist may be-

come a serious disadvantage. RVG 6000 exhibited a

wider useful exposure range than the Insight film with

almost the same dose requirements especially in higher

Kv settings.

6. ACKNOWLEDGEMENTS

We are grateful to the following companies: Dentomedica SA, Den-

tofair SA and Duerr Gmbh Germany, for supplying us with the image

detectors. We also thank our colleagues who served as observers.

REFERENCES

[1] United Nations Scientific Committee on the Effects of

Atomic Radiation (2000) Sources and effect of ionizing

E. Katsoni et al. / Health 3 (2011) 292-299

299299

radiation. Report, 1, UNSCEAR publications, Vienna.

[2] European Union. (1997) Council Directive 97/43 Eura-

tom, on health protection of individuals against the dan-

gers of ionizing radiation in relation to medical expo-

sures, and repealing Directive 84/466 Euratom. Official

Journal of the European Communities, Legislation 180,

22.

[3] Kitagawa, H. and Farman, A.G. (2004) Effect of beam

energy and filtration on the signal-to-noise ratio of the

Dexis intraoral X-ray detector. Dentomaxillofacial Radi-

ology, 33, 21-24. doi:10.1259/dmfr/26493631

[4] Wenzel, A. (2006) A review of dentists’ use of digital

radiography and caries diagnosis with digital systems.

Dentomaxillofacial R a d i o l o gy, 35 , 307-314.

doi:10.1259/dmfr/64693712

[5] Hellen-Halme, K. (2007) Quality aspects of digital radi-

ography in general dental practice. Swedish Dental

Journal. Supplement, 184, 9-60.

[6] Cowen, A.R., Kengyelics, S.M. and Davies, A.G. (2008)

Solid-state, flat-panel, digital radiography detectors and

their physical imaging characteristics. Clinical Radiology,

63, 487-498. doi:10.1016/j.crad.2007.10.014

[7] Hintze, H. (2006) Diagnostic accuracy of two software

modalities for detection of caries lesions in digital radio-

graphs from four dental systems. Dentomaxillofacial Ra-

diology, 35, 78-82. doi:10.1259/dmfr/50356588

[8] Yakoumakis, E.N., Tierris, C.E., Stefanou, E.P., Phanoura-

kis, I.G. and Proukakis. C.C. (2001) Image quality as-

sessment and radiation doses in intraoral radiography.

Oral Surgery, Oral Medicine, Oral Pathology, Oral Ra-

diology, and Endodontics, 91, 362-368.

doi:10.1067/moe.2001.111940

[9] Ang, D.B., Angelopoulos, C. and Katz, J.O. (2006) How

does signal fade on photo-stimulable storage phosphor

imaging plates when scanned with a delay and what is

the effect on image quality? Oral Surgery, Oral Medicine,

Oral Pathology, Oral Radiology, and Endodontics, 102,

673-679. doi:10.1016/j.tripleo.2005.11.002

[10] Ramamurthy, R., Canning, C.F., Scheetz, J.P. and Farman,

A.G. (2004) Impact of ambient lighting intensity and du-

ration on the signal-to-noise ratio of images from photo-

stimulable phosphor plates processed using DenOptix

and ScanX systems. Dentomaxillofacial Radiology, 33,

307-311. doi:10.1259/dmfr/91373164

[11] Parsons, D.M., Kim, Y. and Haynor, D.R. (1995) Quality

control of cathode-ray tube monitors for medical imaging

using a simple photometer. Journal of Digital Imaging, 8,

10-20. doi:10.1007/BF03168051

[12] Jervis, S.E. and Brettle, D.S. (2003) A practical approach

to soft-copy display consistency for PC-based review

workstations. The British Journal of Radiology, 76,

648-652. doi:10.1259/bjr/25693100

[13] Berkhout, W.E.R., Beuger, D.A., Sanderink, G.C.H. and

Stelt, van der P.F. (2004) The dynamic range of digital

radiographic systems: Dose reduction or risk of overex-

posure? Dentomaxillofacial Radiology, 33, 1-5.

doi:10.1259/dmfr/40677472

[14] Borg, E. and Grondahl, H.G. (1996) On the dynamic

range of different X-ray photon detectors in intra-oral ra-

diography. A comparison of image quality in film,

charge-coupled device and storage phosphor systems.

Dentomaxillofacial R a d i o l o gy, 25 , 82-88.

[15] Borg, E., Attaelmanan, A. and Grondahl, H.G. (2000)

Image plate systems differ in physical performance. Oral

Surgery, Oral Medicine, Oral Pathology, Oral Radiology,

and Endodontics, 89, 118-124.

doi:10.1016/S1079-2104(00)80026-8

[16] Farman, A.G. and Farman, T.T. (2005) A comparison of

18 different x-ray detectors currently used in dentistry.

Oral Surgery, Oral Medicine, Oral Pathology, Oral Ra-

diology, and Endodontics, 99, 485-489.

doi:10.1016/j.tripleo.2004.04.002

[17] Kitagawa, H., Farman, A.G., Scheetz, J.P., Brown, W.P.,

Lewis, J., Benefiel, M., et al. (2000) Comparison of three

intra-oral storage phosphor systems using subjective im-

age quality. Dentomaxillofacial Radiology, 29, 272-276.

doi:10.1038/sj.dmfr.4600532

[18] Willis, C.E. (2004) Strategies for dose reduction in ordi-

nary radiographic examinations using CR and DR. Pedi-

atric Radiology, 34, Supplement 3, S196-200, discussion,

S34-41.

[19] Bhaskaran, V., Qualtrough, A.J.E., Rushton, V.E., Wor-

thington, H.V. and Horner, K. (2005) A laboratory com-

parison of three imaging systems for image quality and

radiation exposure characteristics. International Endo-

dontic Journal, 38, 645-652.

doi:10.1111/j.1365-2591.2005.00998.x

[20] Hayakawa, Y., Shibuya, H., Ota, Y. and Kuroyanagi, K.

(1997) Radiation dosage reduction in general dental prac-

tice using digital intraoral radiographic systems. The

Bulletin of Tokyo Dental College, 38, 21-25.

[21] Yoshiura, K., Welander, U., McDavid, W.D., Li, G., Shi,

X.Q., Nakayama, E., et al. (2004) Comparison of the

psychophysical properties of various intraoral film and

digital systems by means of the perceptibility curve test.

Dentomaxillofacial R a d i o l o gy, 33 , 98-102.

doi:10.1259/dmfr/29102849

[22] Radiation Protection (2004) European guidelines on ra-

diation protection in dental radiology: The safe use of ra-

diographs in dental practice. 136.

[23] Syriopoulos, K., Velders, X.L., Stelt, van der P.F., Ginkel,

van F.C. and Tsiklakis, K. (1998) Mail survey of dental

radiographic techniques and radiation doses in Greece.

Dentomaxillofacial R a d i o l o gy, 27 , 321-328.

doi:10.1038/sj.dmfr.4600385

[24] Hatziioannou, K., Psarouli, E., Papanastassiou, E., Bous-

bouras, P., Kodona, H., Kimoundri, O., et al. (2005)

Quality control and diagnostic reference levels in in-

traoral dental radiographic facilities. Dentomaxillofacial

Radiology, 34, 304-307. doi:10.1259/dmfr/38802780

[25] Gonzalez, L. and Moro, J. (2007) Patient radiation dose

management in dental facilities according to the X-ray

focal distance and the image receptor type. Dentomaxil-

lofacial Radiology, 36, 282-284.

doi:10.1259/dmfr/67494525