Analysis of the detective quantum efficiency of a radiographic screen-film combination

902 J. Opt. Soc. Am. A/Vol. 4, No. 5/May 1987

Analysis of the detective quantum efficiency of aradiographic screen-film combination

Phillip C. Bunch, Kenneth E. Huff, and Richard Van Metter

Health Sciences Division, Eastman Kodak Company, Rochester, New York 14650

Received August 19, 1986; accepted January 20, 1987

Detective quantum efficiency provides a useful measure of the imaging efficiency of imaging systems. Methods formeasuring the exposure and the spatial-frequency dependence of the contrast transfer function, the noise powerspectrum, and the detective quantum efficiency are developed for x-ray imaging systems. These are applied to ahigh-resolution screen-film combination exposed to a 30-kV-peak x-ray spectrum. The major component sourcesof screen-film noise in this system are identified and quantified. These are interpreted in terms of a simple modelto predict the screen-film noise power spectrum and detective quantum efficiency. Reasonable agreement is foundbetween model predictions and experimental measurements.

INTRODUCTION

The image quality of radiographic imaging systems is ulti-mately limited by the finite fluence of x-ray quanta. Therole of this finite number of quanta in screen-film imagenoise has long been recognized1' 2 and is referred to as quan-tum mottle. A linear systems model for screen-film x-rayimaging, describing the combined effects of quantum mottleand film-grain noise components, was developed byDoerner3 and was used by Rossmann4' 5 to interpret experi-mental measurements. Since then, a number of other noisesources in screen-film radiography have been recognizedand modeled. One such noise source results from the pro-cess by which x rays are absorbed and their energy is con-verted to light quanta that expose the film.68 This noisesource has been characterized for a number of commerciallyavailable screens by Dick and Motz9' 10 and by Drangova andRowlands." In recent papers12-'4 these component noisesources were considered in a theoretical analysis of the imag-ing characteristics of screen-film systems based on the pre-viously mentioned work as well as on the more recent workby Kemperman and Trabka.15 This analysis predicted theexposure and the spatial-frequency dependence of thescreen-film contrast transfer function (CTF) and the noisepower spectrum (NPS) as well as overall measures of signal-to-noise ratio (SNR) and efficiency, that is, noise-equivalentquanta and detective quantum efficiency (DQE)161 interms of a small number of independently measurablescreen and film properties. In this paper our theoreticalanalysis will be extended to include an independently mea-surable component of noise power associated with screennoise following the work of Albrecht and Proper,1 9 Wagnerand Muntz, 2 0 and others. 2' 21' 22

In recent years, the practical evaluation of diagnostic im-aging systems has been made increasingly in terms of theimage-quality metrics described above.23-25 Measurementsof the exposure and the spatial-frequency dependence ofCTF and NPS, and the SNR quantities derivable fromthem, have now been reported for several radiographicscreen-film systems.2 -29 In this paper we present a refinedset of experimental data for a high-resolution, low-noise

radiographic system. Separate measurements of quantumfluence, film noise, and screen noise permit comparison ofthe screen-film measurements with theoretical predictions.

The purposes of this paper are as follows: to extend ourprevious theoretical model12 to include an independentlymeasurable source of noise associated with the screen; toreport a refined set of measurements of CTF, NPS, and DQEfor the Kodak Min-R screen-Kodak ortho M film combina-tion; and to compare the predictions of theory with experi-ment. We show that the sources of noise included in thetheory are necessary for an explanation of the measured dataand that the agreement between theory and experiment isconsistent with the validity of the simplifying assumptionson which the theory is based.

THEORY

A linear systems model for radiographic screen-film systemswas analyzed by Shaw and Van Metter12 -14 based on thework of Doerner, 3 Rossmann, 4 Swank, 7 Kemperman andTrabka,15 and Dillon et al.

3 0 In this model, the x-rayscreen-film imaging system is modeled as a linear transduc-er that converts absorbed x-ray quanta into light quanta,which, in turn, expose the film. The single-screen single-emulsion theory that follows will simplify some terminologyin the above model while extending it to include polyenerget-ic x-ray spectra and a residual screen noise power componentassociated with noise processes within the screen.

The mean number of light quanta emitted by the screen ina unit area is expressed as

q = mQ, (1)

where

Q = Qe(E)dE (2)

is the mean number of incident x-ray quanta per unit area interms of Q(E), the mean number of incident x-ray quantaper unit area at energy E per unit x-ray energy;

0740-3232/87/050902-08$02.00 © 1987 Optical Society of America

Bunch et a.

Vol. 4, No. 5/May 1987/J. Opt. Soc. Am. A 903

f n,(E)Q,(E)dE

is the mean quantum absorption efficiency expressedterms of Qe(E) and e(E), the energy-dependent quantabsorption efficiency at energy E; and

J17J)Qe(E)me(E)dEm =

is the mean number of light quanta emitted by the screenabsorbed x-ray quantum in terms of me(E), the energy-pendent mean number of emitted light quanta per absorlx-ray quantum at energy E, and the above factors.3'

The mean developed density for x-ray exposure ofscreen-film combination and the light exposure of the fare related as

DSf(Q) = Df(q).

and NPSr is a measurable residual-noise power componentassociated with a stationary screen-noise pattern, which willbe assumed to be of the form(3)

in NPS,(q, w) = #32(c)CTFf 2(q, ), (9)

um where CTFf(q, a) reflects the film's response and f3(w) is ameasure of the frequency-dependent noise amplitude thatcharacterizes the screen and that will be measured experi-mentally. The absence of explicit dependence on the x-ray

(4) quantum fluence, Q, reflects the assumption that the residu-al noise is proportional to screen light emission.

per The DQE for the screen-film combination then followsde- from the working relationshipbed

theilm

(5)

The CTF for x-ray exposure of the screen-film combinationis given by

CTF/f(Q, c) = CTFf(q, co)Ts(c), (6)

where CTFf is for film exposure to light, T8 (w) is the modula-tion-transfer factor resulting from screen composition andscreen-film geometry, and co is the spatial frequency.

The noise sources in radiographic imaging include thefinite number of x-ray quanta absorbed by the screen, theconversion of absorbed x-ray quanta into light quanta thatexpose the film, and the film granularity, which we consid-ered previously.'2 Following the work of Albrecht andProper,' 9 we now add a residual noise term so that the NPSof developed film density that measures the screen-filmsystem output noise is in this linear model, expressed as thesum of three terms,

NPSsf(Q, ) = (log e)2(1 + m) CTF, (Q, (o)nQ k mnl I

+ NPSf(q, a) + NPS(q, (a), (7)

where c = (n 2 /m) - 1 is the Poisson excess noise associatedwith the x-ray-to-light conversion process, expressed interms of the variance and the mean of the number of lightquanta produced per absorbed x-ray quantum. The vari-ance in the number of light quanta per absorbed x-ray isgiven by

Qe(E)fl(E)var[m(E)]dE=2 =

=~~n

+JQe(E),q,(E)Me2(E)dE

(8)nQ

which is the sum of the weighted average of the intrinsicenergy-dependent variance in light emission, var[me(E)],and the variance resulting from the dependence of the aver-age light emission on x-ray energy, me(E), as selected by theabsorbed x-ray energy spectrum ie(E)Qe(E).7

NPSf is the noise power of the film when exposed to light,

DQE/f( (,) =(log e)'CTF,,/f'(Q, as)DQES/f(Q, wo) =- QNPSS,/f(Q, wo)

given by Shaw.3 2

EXPERIMENTAL PROCEDURE

(10)

Calculation of the exposure and the spatial-frequency de-pendence of theoretical and experimental CTF, NPS, andDQE requires data from several different measurements.The procedures used are described in this section.

Materials and Film ProcessingA Kodak Min-R screen and Kodak ortho M film were usedfor this work. Film processing was performed on a KodakRP X-Omat processor (model M6AW), flood replenishedwith Kodak RP X-Omat processing chemicals. The devel-oper temperature was maintained at 950 F.

DensitometryOptical densities are expressed in terms of diffuse density asmeasured by an X-rite Model 310 densitometer, which isfactory calibrated to American National Standards InstituteStandard Ph 2.19 and is traceable to a National Bureau ofStandards (NBS) calibration step tablet. Density measure-ments for NPS and modulation transfer function (MTF)measurements were made using a Perkin-Elmer PDS Model1010A microdensitometer with 0.8-N.A. objectives and aneffective scanning aperture of 0.02 mm by 0.76 mm. Acalibration step-wedge exposure on the film studied wasscanned along with each sample in order to calibrate themicrodensitometer to diffuse density.

Exposing Procedures

X-Ray SensitometryOur x-ray sensitometer is a dedicated, computer-controlled,intensity-scale system that is qualitatively similar to thesystem described by Haus et al.

3 3 In order to reduce sensi-tometric error, we averaged the data from three sensitomet-ric film strips.

X-Ray Modulation Transfer Function and Noise PowerSpectrumX-ray NPS exposures were performed using a tungsten tar-get x-ray tube (12° target angle) driven by a three-phase,twelve-pulse generator operated at 30 kV peak (kVp). Totalbeam filtration (inherent plus added) was 1.5-mm alumi-num equivalent, yielding a measured first half-value layer of

Bunch et al.


0.86-mm aluminum. X-ray exposure values were measuredusing calibrated (5%) air-ionization chambers (RADCALModels 10X5-60, 20X5-60, and 20X5-6M). The exposurevalues were converted to incident quantum fluence by usinga conversion factor determined from the half-value layer andthe calculated relationship between quantum fluence perunit exposure and half-value layer for appropriate publishedx-ray spectra.3 4 This procedure was described in more de-tail by Bunch and Huff.28 MTF exposures were made at 30kVp with a 13.5° tungsten target tube operated by the samex-ray generator used for the NPS exposures. Total beamfiltration was 1.5-mm aluminum equivalent.

Light SensitometryStep-wedge exposures for light sensitometry were made witha Kodak sensitometer, Model Ib, in which light from a 3000 Klamp was passed through a 540-nm, 8-nm half-bandwidthinterference filter. This light source approximates the pri-mary emission line of the Kodak Min-R screen. The photonfluence was determined by using a photodiode calibratedagainst local standards traceable to a NBS standard source.

Light Noise Power SpectrumUniform film exposures for NPS analysis were made with acustom camera having a light source similar to that used forlight sensitometry. The camera had -a flat-black-paintedinterior and was baffled to eliminate specular reflections.The deviation from exposure uniformity with this camera is<1% over the 20 cm by 25 cm film plane.

Modulation Transfer Function MeasurementOur x-ray MTF data for the screen-film combination wereobtained with the slit exposure method for measuring theline-spread function using the procedure described by Doi etal.2 3 The MTF of a single-emulsion, halation-protectedfilm such as Kodak ortho M can be taken to be 1.0 at thespatial frequencies of interest, as discussed by Huff andWagner.3 5

Noise Power MeasurementA contiguous area of film, 8.192 cm by 9.728 cm, was scannedwith the 0.02 mm by 0.76 mm microdensitometer aperture,yielding 128 rasters of 4096 points each. To minimize theeffects of aliasing, a low-pass, four-pole Butterworth elec-tronic filter, with the 3-dB point set to the Nyquist frequen-cy for the scan, was inserted into the analog signal line of themicrodensitometer. From these data, an effective scanningslit, 12.16 mm by 0.02 mm, was synthesized. The resulting128 slit-synthesized 256-point blocks were used to estimatethe NPS. The algorithm used is similar to the digital Black-man-Tukey method, as summarized in several recent publi-cations,23'36' 37 except that we have found it to be harmful toperform spatial filtering or explicit windowing. We did em-ploy a low-order polynomial detrending operation on eachscan raster to reduce the contaminating effects of slowlyvarying x-ray exposing nonuniformities, having first verifiedthat this detrending operation causes negligible distortionson trendless synthetic data.

Where necessary, microdensitometer noise has been re-duced by using the cross spectrum between two registeredscans of each film sample; each of these scans had beencorrected for platen transmission irregularities. The result-

ing microdensitometer NPS ranged from 0.003 ,um2 below adensity of 1.7 to 0.10 ,um2 at a density of 2.9. After consider-able experimentation, we decided to use a separable, nonlin-ear, two-dimensional combination running-median andHanning smoothing method for the interpolated NPS datasurfaces.38 39 This technique is resistant to outlier data andcauses less distortion to the rapidly changing low-frequencyNPS data than most other smoothing techniques. Beforesmoothing, the statistical precision of our NPS data is esti-mated to be ±10% by using the basic methods described bySandrik and Wagner37 ; our smoothing method reduces thisestimated error to +3%.

RESULTS

Signal-Transfer CharacteristicsFigure 1 shows the absolute sensitometric data for the Ko-dak ortho M film when it is exposed to light and when thescreen-film combination is exposed to our x-ray spectrum.Both the density (D) and its derivative (y) of the developedfilm are plotted as functions of the incident quantum fluencelogarithm over the exposure range used for this work. Thesimilarity in the shapes of the two curves is in agreementwith the theoretical assumptions as discussed above. Fig-ure 2 is a plot of the screen-film combination MTF.

4.0-c] .0- - -- ---0 / D

co

- 2.0---7 t-

I ~~~~2.23(8 __ __ --- -- -L ----

Xray I Light

0.0 6.0 7.0 - &0 9.0

Log1o (quantum fluence)

Fig. 1. Absolute sensitometric characteristics of the film exposedto light and the screen-film combination exposed to x rays as afunction of the incident quantum fluence.

MTF

0.4

0 2.0 4.0 6.0 8.0Cycles/ mm

Fig. 2. MTF data for the screen-film combination.

10.0

Bunch et al.


I ~~X-ray exposure

o O \ -. -o Light exposure ------------

0.2 16 2.9 4.3 5.7 7.0Cycles/mm

Fig. 3. Measurements related to the residual screen NPS data.The net NPS data are obtained by subtracting the light-exposedfilm NPS data from the x-ray-exposed screen-film NPS data andare then used as an estimate of the residual screen NPS. In thisparticular experiment, Kodak Panatomic-X Aerographic II film wasused instead of the faster Kodak ortho M film, for reasons discussedin the text.

Estimation of Screen ParametersThe calculated x-ray quantum absorption, q, is 0.58 for thex-ray spectrum used and is similar to that published byothers.4 0 From Eq. (8), we calculated a value of 0.398 for E/mfrom the incident x-ray spectrum and published data for thestatistical fluctuations of fluorescent light as a function of x-ray energy for the Kodak Min-R screen.9 Equation (1) isused to estimate the mean number of light quanta per ab-sorbed x-ray quantum, m, to be 284, based on the absolutesensitometric data above and the calculated x-ray quantumabsorption.

Screen Noise Power Spectrum ComponentsExperimental procedures have been reported for measuringthe components of a screen NPS. 2

,19

,20

,21

,41 Following these,

we measured total screen noise by replacing the Kodak orthoM film with a slow, fine-grained film (Kodak Panatomic-XAerographic II film). With this film, the screen-film combi-nation required an incident x-ray quantum fluence of>4,000,000 quanta/mm2 to produce a developed film densityof 1.12. At such high exposure, the first term of Eq. (7) isrelatively small. In this case, the residual screen noise canbe estimated by subtracting the light-exposed film NPSfrom the x-ray exposed screen-film NPS, as indicated in Fig.3. The CTF of the Kodak Panatomic-X Aerographic II filmwas 2.28 at this density, independent of spatial frequencyover the range studied. Knowledge of this CTF and that ofthe Kodak ortho M film as a function of exposure allowed usto predict the screen NPS recorded by the ortho M filmaccording the Eq. (9). The detailed mechanisms of theresidual NPS are under investigation in our laboratory.

One measured residual screen-noise source can be attrib-uted to the spatial variability of screen x-ray absorption.This was measured separately by radiographing the screenunder the same x-ray spectral condition with Kodak X-Omat V film, which is a slow, fine-grained direct x-ray filmnormally used for radiation-therapy verification. For thisexperiment, the screen was sealed in a light-tight envelope toprevent screen fluorescent light from contributing to the

radiographic image. The resulting NPS, after subtractingthe NPS associated with exposing the X-Omat V film to thedirect x-ray beam, was analyzed analogously to the total-screen NPS term described above to produce an estimate ofthe recorded x-ray absorption NPS. In agreement with thetheoretical estimate of Barnes and Chakraborty,4 2 we foundthis NPS component to be relatively unimportant (- 0.6 Am

2

at density D = 1.0 and spatial frequency X = 2.0 cycles/mm,which is 6.5% of the total screen-film NPS at that densityand spatial frequency), except possibly at the lowest mea-sured spatial frequencies. Therefore we neglect this noisesource in the remainder of this paper.

Film-Noise Power SpectrumOur film NPS data are strongly dependent on both spatialfrequency and exposure, as shown in Fig. 4. The increase offilm NPS with increasing exposure and film density at thehigher spatial frequencies is generally expected.4 34 4 Therapid rise of the NPS at low spatial frequencies, while notpredicted by existing theory,4 5 has been experimentally ob-

NPS(pm2 D2 )

(a)

0.2

EECna)

01

70L7.3 7.6 8.0 8.4

Log1 0 q

(b)Fig. 4. NPS of Kodak ortho M film when exposed to an incandes-cent light source that is filtered to match the principal emission lineof the screen.

Bunch et al.


NPS(pm

2D

2) 2

0.

0.2

1.2

2.1

EE

a)

0

3.1

4.1

5.1

6.1

7.0

(a)

Log10 Q(b)

Fig. 5. Measured NPS for the screen-film combination.

served by others23 40 and is generally observed in our filmNPS measurements. While this effect has not been ana-lyzed in detail at this time, we are confident that it is not anartifact of our measurement arising from nonstationarity ortrends in our raw data.

Comparison of Experimental and Theoretical NoisePower SpectraMeasured experimental screen-film combination NPS dataare shown in Fig. 5. From the parameters and measuredfunctions described above and using Eq. (7), we calculate thetheoretical system NPS surface shown in Fig. 6. The gener-al agreement between theory and experiment is apparent bycomparison of these figures. A more detailed assessment ofthe agreement between theory and the experimental NPScan be obtained by constructing the difference surfaceshown in Fig. 7. The average value of the difference be-tween experiment and theory is 0.4 Am

2, with a rms error of1.5 ,tm2. The average fractional error was computed to be

0.037, with a standard deviation of 0.15, which is generallywithin experimental error. A comprehensive, detailed anal-

ysis of the agreement between theory and experiment wascomplicated by our use of complex interpolation andsmoothing methods, and it is not yet available.

Comparison of Experimental and Theoretical DetectiveQuantum EfficiencyExperimental and theoretical DQE surfaces are shown inFigs. 8 and 9, respectively. The general qualitative agree-ment between experiment and theory is apparent from thesefigures, as would be expected from the CTF and the NPSalready shown. An analysis of difference and fractionalerror surfaces reveals an average difference between theoryand experiment of 0.026, with a rms error of 0.014, and anaverage fractional error of -0.067, with a standard deviationof 0.19. As discussed in some detail by Sandrik and Wag-ner,37 the precision of our DQE data is estimated to be ±10-15%, based on the estimated precision of the DQE compo-nents. Thus experiment and theory, with respect to DQE,generally agree to within a simple estimate of our experi-mental error.

NPS(Um2 D2 )

(a)

0.2

EE

a)

0

7.0 I.'' ' Ii ' ... ' ' I ' I " ' ' II I "' ' '15.0 5.4 5.8 6.2

Log1 0Q

(b)

Fig. 6. Theoretical NPS for the screen-film combination as givenby Eq. (7).

Bunch et al.


ANPS(' m2 D2 )

(a)

0.2

1.2

2.1-

EEC)a,

0

3.1-

4.1-

5.1

6.1

7.05.0

Fig. 7. The differencescreen-film NPS.

Log1 0 Q

(b)

between experimental and theoretical

DISCUSSION

We have reviewed a simple model for the NPS of a screen-film combination that includes the effects of quantum fluc-tuations, x-ray absorption, conversion-efficiency fluctua-tions, screen noise, and film noise. A comparison of themodel predictions with our experimental measurements ofthe Kodak Min-R screen-Kodak ortho M film combinationshows reasonable agreement over the range of x-ray expo-sure and spatial frequency studied. While the model per-mits interpretation of the imaging characteristics of screen-film systems in terms of a small number of independentlymeasurable parameters, it is known to be incomplete in anumber of ways. For example, it does not include the depthdependence of the MTF6 or the reabsorption of fluorescentx-ray quanta. 4 6

Our experimental results can also be compared with thosereported by others. In this regard, a significant differencebetween our current data and data published by Nishikawaand Yaffe40 occurs at low (<1-cycle/mm) spatial frequencies,

where our NPS data are significantly greater than their data.At higher frequencies our data are in good agreement.There are several differences in the experimental methodsused, such as slit length, detrending algorithm, and x-ray-exposing equipment, which may account for these observa-tions. We used a 12-mm synthesized scanning slit, as op-posed to the 2.16-mm slit used by Nishikawa and Yaffe; wedid polynomial detrending instead of using their differenc-ing technique; and we used general-purpose x-ray equip-ment, which suffers from measurable nonuniformities underlow-kVp conditions. Nevertheless, we agree with Ni-shikawa and Yaffe that film noise apparently cannot beaccurately modeled as white noise. With respect to thesomewhat more theoretically oriented work of Barnes andChakraborty,4 2 our measurements of an x-ray-absorptionNPS tend to support their calculations, indicating the rela-tive unimportance of phosphor coating nonuniformities as acontributor to the screen-film NPS. Our inclusion of aresidual-noise term in Eq. (7) is consistent with the ap-proach taken by Wagner and Muntz, and it results in reason-ably good agreement between experiment and theory.

DQE

(a)

0.2

1.2

2.1

EE(na)

0

3.1

4.1

5.1

6.1

7.0

Log10 Q

(b)

Fig. 8. Measured DQE for the screen-film combination.

Bunch et al.


DQE

(a)

0.2

1.2

2.1

EEC,,

a,

C)

3.1

4.1

5.1

6.1

7.05.0 5.4 5.8 6.2

Log1 0 Q

(b)

Fig. 9. Theoretical DQE for the screen-film combination, as givenby Eqs. (7) and (10).

More-detailed comparisons with other laboratories wouldrequire that all involved groups work with nominally identi-cal materials, exposing conditions, and film processing, sincemany of the effects reported in this and other publicationsmay depend on specific experimental conditions. Theselast considerations are probably most important for radio-graphic imaging systems used at very-high-x-ray quantumfluences.

ACKNOWLEDGMENTS

A project of this magnitude depends on the efforts andabilities of many people. In particular, we are indebted toHarold G. Giddings for preparing the hundreds of film sam-ples used and for his skill and experience in performing themicrodensitometry. We acknowledge the many valuablecontributions of Arthur H. Simmons, Jr., in the areas ofcomputer programming, data analysis, and computer graph-ics. The contributions of Paul W. Wagner in terms ofexperimental coordination, consultations, and MTF data

analysis are deeply appreciated. We are indebted to WayneV. Stencel for maintaining our film processor at a high per-formance level. In addition, we benefitted from discussionswith many of our colleagues in the image-science and radio-graphic communities.

REFERENCES AND NOTES

1. R. E. Sturm and R. H. Morgan, "Screen intensification systemsand their limitations," Am. J. Roentgenol. 62, 617-634 (1949).

2. H. M. Cleare, H. R. Splettstosser, and H. E. Seeman, "An ex-perimental study of the mottle produced by x-ray screens," Am.J. Roentgenol. 88, 168-174 (1962).

3. E. C. Doerner, "Wiener-spectrum analysis of photographicgranularity," J. Opt. Soc. Am. 52, 669-672 (1962).

4. K. Rossmann, "Modulation transfer function of radiographicsystems using fluorescent screens," J. Opt. Soc. Am. 52,774-777(1962).

5. K. Rossmann, "Measurement of the modulation transfer func-tion of radiographic systems containing fluorescent screens,"Phys. Med. Biol. 9, 551-557 (1964).

6. G. Lubberts, "Random noise produced by x-ray fluorescentscreens," J. Opt. Soc. Am. 58, 1475-1483 (1968).

7. R. K. Swank, "Absorption and noise in x-ray phosphors," J.Appl. Phys. 44, 4199-4203 (1973).

8. H. P. Chan and K. Doi, "Studies of x-ray energy absorption andquantum noise properties of x-ray screens by use of MonteCarlo simulation," Med. Phys. 11, 37-46 (1984).

9. C. E. Dick and J. W. Motz, "Image information transfer proper-ties of x-ray fluorescent screens," Med. Phys. 8,337-346 (1981).

10. C. E. Dick and J. W. Motz, "Utilization of monoenergetic x-raybeams to examine the properties of radiographic intensifyingscreens," IEEE Trans. Nucl. Sci. NS-28, 1554-1558 (1981).

11. M. Drangova and J. A. Rowlands, "Optical factors affecting thedetective quantum efficiency of radiographic screens," Med.Phys. 13, 150-157 (1986).

12. R. Shaw and R. L. Van Metter, "An analysis of the fundamentallimitations of screen-film systems for x-ray detection: I. Gen-eral theory," in Application of Optical Instrumentation inMedicine XI, G. D. Fullerton, ed., Proc. Soc. Photo-Opt. In-strum. Eng. 454, 128-132 (1984).

13. R. Shaw and R. L. Van Metter, "An analysis of the fundamentallimitations of screen-film systems for x-ray detection: II.Model calculations," in Application of Optical Instrumenta-tion in Medicine XI, G. D. Fullerton, ed., Proc. Soc. Photo-Opt.Instrum. Eng. 454, 133-141 (1984).

14. R. Shaw and R. L. Van Metter, "The role of screen and film indetermining the noise-equivalent number of quanta recordedby a screen-film system," in Application of Optical Instrumen-tation in Medicine XIII: Medical Image Production, Process-ing, and Display, R. H. Schneider and S. J. Dwyer III, eds.,Proc. Soc. Photo-Opt. Instrum. Eng. 535, 184-194 (1985).

15. J. H. B. Kemperman and E. A. Trabka, "Exposure fluctuationsin model photographic emulsions: II. Statistics due to intensi-fying screens," Photogr. Sci. Eng. 25, 108-111 (1981).

16. A. Rose, Vision: Human and Electronic (Plenum, New York,1974).

17. R. C. Jones, "Quantum efficiency of detectors for visible andinfrared radiation," Adv. Electron. Electron Phys. 11, 87-183(1959).

18. P. B. Fellgett, "On necessary measurements for the character-ization and optimum use of photographic materials for scientif-ic purposes," J. Photogr. Sci. 9, 201-206 (1961).

19. C. Albrecht and J. Proper, "Quantum mottle and intrinsic noisesources in radiographic systems," in Television in DiagnosticRadiology, R. D. Moseley and J. H. Rust, eds. (Aesculapius,Birmingham, Ala., 1969), pp. 279-295.

20. R. F. Wagner and E. P. Muntz, "Detective quantum efficiency(DQE) analysis of electrostatic imaging and screen-film imag-ing in mammography," in Application of Optical Instrumenta-tion in Medicine VII, J. E. Gray, ed., Proc. Soc. Photo-Opt.Instrum. Eng. 173, 162-165 (1979).

21. K. Doi, "Wiener spectrum analysis of quantum statistical fluc-

Bunch et al.


tuation and other noise sources in radiography," in Televisionin Diagnostic Radiology, R. D. Moseley and J. H. Rust, eds.(Aesculapius, Birmingham, Ala., 1969), pp. 313-333.

22. G. T. Barnes, "Radiographic mottle: a comprehensive theory,"Med. Phys. 9, 656-667 (1982).

23. K. Doi, G. Holje, L. Loo, H. Chan, J. Sandrik, R. Jennings, andR. Wagner, "MTFs and Wiener spectra of radiographicscreen-film systems," U.S. Department of Health and Human ServicesPub. FDA 82-8187 (U.S, Government Printing Office, Washing-ton, D.C., April 1982).

24. M. G. Fisher, "MTF, noise power and DQE of radiographicscreens," Photogr. Sci. Eng. 26, 32-41 (1982).

25. R. F. Wagner, "Low contrast sensitivity of radiographic, CT,nuclear medicine, and ultrasound medical imaging systems,"IEEE Trans. Med. Imaging MI-2, 105-121 (1983).

26. P. C. Bunch, R. Shaw, and R. L. Van Metter, "Signal-to-noisemeasurements for a screen-film system," in Application of Op-tical Instrumentation in Medicine XI, G. D. Fullerton, ed.,Proc. Soc. Photo-Opt. Instrum. Eng. 454, 154-163 (1984).

27. P. C. Bunch, "Comparison of signal-to-noise ratios of some newscreen-film systems," in Medical Imaging and Instrumenta-tion '84, J. A. Mulvaney, ed., Proc. Soc. Photo-Opt. Instrum.Eng. 486, 99-107 (1984).

28. P. C. Bunch and K. E. Huff, "Signal-to-noise ratio measure-ments on two high-resolution screen-film systems," in MedicalImaging and Instrumentation '85, J. A. Mulvaney, ed., Proc.Soc. Photo-Opt. Instrum. Eng. 555, 68-83 (1985).

29. P. C. Bunch, K. E. Huff, and R. Van Metter, "Sources of noise inhigh-resolution screen-film radiography," in Application ofOptical Instrumentation in Medicine XIV: Medical Imaging,Processing, and Display, R. H. Schneider and S. J. Dwyer III,eds., Proc. Soc. Photo-Opt. Instrum. Eng. 626, 64-75 (1986).

30. P. L. Dillon, J. F. Hamilton, M. Rabbani, R. Shaw, and R. L. VanMetter, "Principles governing the transfer of signal modulationand photon noise by amplifying and scattering mechanisms," inApplication of Optical Instrumentation in Medicine XIII:Medical Image Production, Processing, and Display, R. H.Schneider and S. J. Dwyer III, eds., Proc. Soc. Photo-Opt. In-strum. Eng. 535, 130-139 (1985).

31. In this paper m, the number of emitted light quanta per ab-sorbed x-ray quantum, replaces the product miq2, used by uspreviously, where m had been the number of light quanta creat-ed per absorbed x-ray quantum and 2 had been the efficiencywith which they emerged from the screen.

32. R. Shaw, "The equivalent quantum efficiency of the photo-graphic process," J. Photogr. Sci. 11, 199-204 (1963).

33. A. G. Haus, K. Rossmann, C. Vyborny, P. B. Hoffer, and K. Doi,"Sensitometry in diagnostic radiology, radiation therapy, andnuclear medicine," J. Appl. Photogr. Eng. 3, 114-124 (1977).

34. T. R. Fewell and R. E. Shuping, "Handbook of mammographicx-ray spectra," U.S. Department of Health, Education and Wel-fare Pub. FDA 79-8071 (U.S. Government Printing Office,Washington, D.C., 1978).

35. K. E. Huff and P. W. Wagner, "Crossover and MTF characteris-tics of a tabular-grain x-ray film," in Medical Imaging andInstrumentation '84, J. A. Mulvaney, ed., Proc. Soc. Photo-Opt.Instrum. Eng. 486, 92-98 (1984).

36. R. F. Wagner, "Fast Fourier digital quantum mottle analysiswith application to rare earth intensifying screen systems,"Med. Phys. 4, 157-162 (1977).

37. J. M. Sandrik and R. F. Wagner, "Radiographic screen-filmnoise power spectrum: variation with microdensitometer slitlength," Appl. Opt. 20, 2795-2798 (1981); J. M. Sandrik, R. F.Wagner, and K. M. Hanson, "Radiographic screen-film noisepower spectrum: calibration and intercomparison," Appl. Opt.21, 3597-3601 (1982); R. F. Wagner and J. M. Sandrik, "Anintroduction to digital noise analysis," in The Physics of Medi-cal Imaging: Recording System Measurements and Tech-niques, A. G. Haus, ed. (American Institute of Physics, NewYork, 1979), pp. 524-545.

38. P. F. Velleman and C. D. Hoaglin, Applications, Basics andComputing of Exploratory Data Analysis (PWS, Boston,Mass., 1981).

39. P. M. Narendra, "A separable median filter for image noisesmoothing," IEEE Trans. Pattern Anal. Mach. Intell. PAMI-3,20-29 (1981).

40. R. M. Nishikawa and M. J. Yaffe, "Signal-to-noise properties ofmammographic -film-screen systems," Med. Phys. 12, 32-39(1985).

41. K. Rossmann, "Spatial fluctuations of x-ray quanta and therecording of radiographic mottle," Am. J. Roentgenol. RadiumTher. Nucl. Med. 90, 863-869 (1963).

42. G. T. Barnes and D. P. Chakraborty, "Radiographic mottle andpatient exposure in mammography," Radiology 145, 815-832(1982).

43. E. W. Selwyn, "A theory of graininess," Photogr. J. 75, 571-580(1935).

44. H. Siedentopf, "Concerning granularity, resolution and the en-largement of photographic negatives," Phys. Z. 38, 454-459(1937).

45. M. Savelli, "Theoretical and experimental study of the granu-larity of uniformly exposed photographic films," Rev. Opt.Theor. Instrum. 38, 269-281 (1959).

46. C. E. Metz and C. J. Vyborny, "Wiener spectral effect of spatialcorrelation between the sites of characteristic x-ray emissionand reabsorption in radiographic screen-film systems," Phys.Med. Biol. 28, 547-564 (1983).

Bunch et al.

Documents

Analysis of the detective quantum efficiency of a radiographic screen-film combination