Performance of seven rapid radiographic processing solutions

Performance of seven rapid radiographic processing solutions Donna Maddalozzo, DDS, MS,a Ray 0. Knoeppel,b and Charles M. Schoenfeld, DDS, PhD,C Chicago, Ill, NORTHWESTERN

UNIVERSITY

AND

AMERICAN

DENTAL

ASSOCIATION

This study evaluated the performance of seven rapid radiographic processing products. A conventional automatic processing solution was evaluated as a standard of comparison. The products were analyzed with respect to image quality and speed. The results indicate that rapid manual processing generally involves some compromise of image quality as well as slower speeds with an accompanying increase in patient radiation exposure. Accordingly, there seems to be little motivation for the use of rapid manual proEessing solutions unless there is a compelling rationale in terms of time or convenience.

(ORALSURG ORAL MEDORALPATHOL

1990;69:382-7)

T he purpose of this study was to evaluate

the performance of rapid manual processing solutions for intraoral radiographic films. These solutions are intended to process films with developing and fixing times of the order of 10 to 30 seconds each, depending on temperature. Rapid processing solutions are being increasingly marketed to the dental profession under the rationale of expediency and convenience. Some products include the processing solution within the film packet or provide for injection of the solutions into the film packet, presumably for increased convenience. Processing methods affect both image quality and the amount of radiation required to produce an image. Accordingly, it is reasonable to investigate whether the use of rapid processing solutions, and in some cases in-the-packet processing, compromises image quality or necessitates increased patient radiation exposure. In this study, image quality was evaluated in terms of contrast, exposure latitude, spatial resolution, and low frequency noise. Patient exposure was evaluated in terms of the speed of the film/film process combi-

aAssistant Professor of Periodontics, Northwestern University Dental School, Chicago, III. bResearch Assistant, Council on Dental Materials, Instruments, ~14 Eqriipmtxt, ,imerican Dcntai Association, Chicago, 111. CAssistant Secretary, Council on Dental Materials, Instruments, and Equipment, American Dental Association, Chicago, Ill.

7/16/16907 382

nation. Previous studies have evaluated some rapid processing solutions1-7; however, new products have subsequently appeared, including those with in-thepacket processing. There is virtually no objective image quality and speed information for the new products. Moreover, none of the prior studies evaluated speed or included objective measurements of spatial resolution and noise to supplement sensitometric properties. METHODS

Seven different rapid processing solutions were evaluated (Table I). A widely used method of conventional automated processing was evaluated as a standard of performance (RP X-Omat Developer and Replenisher/RP X-Omat Fixer and Replenisher, Eastman Kodak Co., Rochester, New York). Speed, average gradient, and exposure latitude were derived from sensitometric curves. Spatial resolution was expressed in terms of contrast frequency responses derived from images of a test pattern with variable spatial frequencies, but with a constant subject contrast. Some of the films used to generate the sensitometric curves were also used for noise measurements. Films for all of the types of measurements were processed by each of the processing solutions. Two sets of films were used to provide two independent measurements of each property for each product. An E-speed film (Ektaspeed dental x-ray film, Eastman Kodak Co.) was used for all of the measurements except for the in-the-packet products, which are supplied with D-

Performance

of seven rapid radiographic

Volume Number

69 3

Table

I. The products evaluated and the processing conditions Product Company

name: name

Endo A&B: Allied Photo Products Company I F P: M & D International lnsta Neg/Insta Fix: Microscopy Instant Developer/Instant Fixer: Ada Products Inc. Phil X 30”: American Dental Diversified Systems QD: Hanshin Technical Laboratory Ltd. Rapid Access: Eastman Kodak Company *Denotes tHardening

film was presoaked time.

according

to manufacturer

Develop time (se4

Temp. (‘Cl

processing

solutions

Fix time (se4

Rinse (se4

383

Wash time (min)

24

12

3

25

21

16* 16*

18

3 5 3

30 30 30

30 30 30

21

22 30

N/A N/A

31 30

30 30

22

15

3

120

10

22 22 24

5

instructions

speed film sealed inside the film packets. E-speed film was chosen as a film representative of current state of the art intraoral radiography. Since both the film and the film processing affect an image, the use of one type of film provides for comparison of the processing solutions. The results for the two in-the-packet processing products must be interpreted with the realization that the film is not the same as that for the other processing solutions. Films were processed for each instant processing solution product in accordance with the manufacturer’s instructions (Table I). If more than one set of processing temperatures and times was recommended for a product, then a convenient, middle-of-the-range, temperature and time were selected. If prolonged fixing and washing were recommended for archival quality, then that was used. Agitation was used during processing if suggested. The processing solutions were prepared in one gallon manual processing tanks and were aged for 24 hours after mixing to avoid the possibility of a period of hyperactivity shortly after mixing. (In-the-packet processing was the exception to this.) These conditions were intended to achieve a representative measure of the typical performance of each type of solution that might be expected during actual use. All of the films for the two determinations of the sensitometric curves for each product were processed simultaneously. (Again, in-the-packet processing was the exception to this.) Processed films were dried in a conventional warm air film dryer before densitometric analysis. Films for sensitometric curves were exposed at 70 kVp, 10 mA, 1 m target-film distance, and 2.5 mm aluminum equivalent total filtration. Thirty different exposures were used for each curve as well as an unexposed film to establish base plus fog levels. Variable exposure times were used for convenience since timeintensity reciprocity failure is known not to occur with direct exposure film.* An ionization chamber and a

Table

II. Sensitometric

Product

name

E Speeds (Kodak Ektaspeed) Endo A + B IFP Insta Neg/Insta Fix Instant Developer/ Instant Fixer Rapid Access RP X-Omat Developer/ RP X-Omat Fixer D Speeds (In packet processing) Phil-X 30”

QD

properties Speed (R-l)

Average gradient

26.9 35.9 33.4

1.39 1.86

17.2

1.96 1.15

32.2

1.80

46.3

2.18

10.1

1.63 1.24

5.2

Exposure latitude (m W

0.12 0.54 0.51 0.87 0.55 0.46

0.62

0.81

film were positioned symmetrically with respect to the central ray of the x-ray beam to provide a measurement of exposure during the exposure of each film. The optical density of the films was expressed as the average of measurements at three locations. A 1 mm diameter aperture was used for the density readings. Each set of exposure and optical density measurements was used to create a sensitometric curve in the form of a computer-generated third order polynomial curve fit of the data. Speed was calculated as the reciprocal of the exposure in roentgens required to produce an optical density of 1 OD above base plus fog. Average gradient was calculated as the slope of the line on a sensitometric curve between densities of 0.25 and 2.00 above base plus fog. Densities between 0.25 and 2.00 above base plus fog were assumed to be the clinically usable part of the dynamic range. Accordingly, exposure latitude was calculated as the exposure range corresponding to that density range. The images for contrast-frequency responses were

384

Maddalozzo,

Knoeppel,

T Optical Density

and Schoenfeld

Products v------v 0-0 A--A AA n . = l - -*

ORAL

Endo A& I3 IFP Insta Neg/Insta Inst. Dev./Inst. Rapid Access RP XOmat

A

Exposure

47

SURG

ORAL

MED

ORAL PATHOL March 1990

Fix Fixer

(mR)

Products o--o A-A

QD Phil

X-30”

3 -Optical Density 2 --

/ AA. ,O’

1 -II 0 -’ 1

B Fig.

0’

0

/0

A.$O-”

2

o--04-o

,OO

C@v+/-A

(+2-&#

10 Exposure

100

I 1000

(mR)

1. Sensitometriccurvesfor (A) E-speedfilm and (B) D- speed(in-the-packet) film.

made by the same geometry of projection and general technique factors used for the sensitometric curves. Exposure time was adjusted to provide a low-frequency density of about one above base plus fog. The test pattern consisted of square waves of constant subject contrast with spatial frequencies from 0.25 to 10.0 lp/mm. Frequencies above 10 lp/mm are probably not clinically useful.9 The dependence of contrast on spatial frequency was analyzed by microdensitometer scans of each of the images of the square wave subject. The scans were made with a slit aperture of

10 pm X 1 mm at the film plane. The contrast from two cycles of square waves was averaged for each frequency. Noise was analyzed by microdensitometer scans of two films for each processing condition. One of the films was unexposed but processed, and the other film was exposed to provide a density of about 1 OD above base plus fog. These films were selected from the series of films used to generate the sensitometric curves for each set of processing solutions. The unexposed film provides a measure of fixer performance at the

Volume Number

Performance

69 3

of seven rapid radiographic

0.8 --

Contrast Response

v---v e-0 A---A A-A A-A 0-O W 8 l - -*

0.4 --

--

0.0 2

Endo A k B IFP Insta Neg/Insta Inst. Dev./Inst. Phil-X 30” QD Rapid Access RP X-Omat

1I

II

I

I

tI

I

I

I

3

4

5

6

7

8

9

10

Spatial Fig.

Frequency 2. Spatial

most demanding condition, namely clearing all of the emulsion from an unexposed film. The film at one above base plus fog provides a measure of fixer and developer performance estimated to be representative of the average optical density of a typical clinical film. Microdensitometer scans were made with a 1 mm x 1 mm aperture at the film plane. A relatively large scanning aperture was used to emphasize low-frequency noise indicative of fixer performance rather than high-frequency noise indicative of film graininess. Noise was expressed as the absolute value of the deviation from the mean optical density. The data collected for each of the methods above were statistically analyzed by means of the Student Neuman Keuls analysis of variance at a confidence level of 95%. RESULTS

solutions

385

Products

0.6 --

0.2

processing

AND DISCUSSION

The sensitometric curves are presented in Fig. 1 and the sensitometric data derived from the curves are presented in Table Il. In terms of the overall sensitometric curves, the reference standard, Insta Neg/Insta Fix, IFP, and Rapid Access are clustered into a group with the highest speeds and average gradients. The speed for the reference standard is significantly greater than that of any of the rapid processing products. Although Endo A & B and Instant Developer/Instant Fixer resulted in the slowest speeds for E-speed film, they were significantly faster than the in-the-packet processing solutions with the D-speed films. Of the two inthe-packet processing products, Phil-X 30” was sig-

Fix Fixer

(lp/mm)

resolution

properties.

III. Spatial resolution at spatial frequency of ten line pairs per millimeter

Table

Product

name

Contrast

Endo A + B IFP lnsta

Neg/

Insta

Fix

response 0.913 0.909 0.982

Instant Developer/ Instant Fixer

0.994

Phil-X

0.922 0.882 1.03 0.979

30”

QD Rapid Access RP X-Omat Developer/ RP X-Omat Fixer

(10 Ip/mm)

nificantly faster than QD. As expected, there is generally a trade-off between speed and average gradient on the one hand, and exposure latitude on the other hand. For most diagnostic tasks, average gradient is more significant than exposure latitude.‘O High speed is desirable in terms of reducing patient radiation dose, minimizing motion blur, and prolonging X-ray tube lifetime. Based on speed and average gradient, the reference standard, IFP, Insta Neg/Insta Fix, and Rapid Access had the best performance. Contrast frequency responses are presented in Fig. 2, and the contrast responses at a frequency of 10 1 p/ mm are presented in Table III. There are no statistically significant differences in spatial resolutions obtained with all of the rapid processing products and the reference standard. Virtually no loss of contrast

366

Maddalozzo,

Knoeppel,

and Schoenfeld

ORAL SURC ORAL

MED ORAL PATHOL March 1990

0.1 OD Rapid

A

Distance

Access

(mm)

Instant Developer/ Instant Fixer

0.1 ODT Rapid

Access I

I 0

25 Distance

B Fig.

3. Exampless

of optical

density

scans

for

(mm) high

and

low

image

noise

at

(A) base plus fog and (B) one

OD above base plus fog.

occurred over the complete frequency range up to 10 1p/mm. Graphic examples of high and low noise for both base plus fog and 1 OD above base plus fog are presented in Fig. 3. The noise data for all of the rapid processing products and for the reference standard are presented in Table IV. The reference standard, Insta Neg/Insta Fix, and Rapid Access exhibited low noise levels for both base plus fog and 1 OD above base plus fog. IFP had low noise at base plus fog and moderately low noise at 1 OD above base plus fog. QD exhibited low noise at one above base plus fog, but had relatively high noise at base plus fog. Phil-X 30”, Endo A & B, and Instant Developer/Instant Fixer all exhibited relatively high noise at both base plus fog and 1 OD above base plus fog. There are several likely causes for high noise. For the products that exhibited high noise at base plus fog, it was obvious from visual examination that incom-

plete fixing had occurred. Instant Developer/Instant Fixer had a definite periodic variation in the optical density at 1 OD above base plus fog. This variation is probably related to the agitation during the development of the film. Phil-X 30”, one of the in-the-packet products, had a higher optical density at the center of the film for 1 OD above base plus fog and to a lesser extent base plus fog. For 1 OD above base plus fog, this was probably caused by poor circulation of the processing solutions near the edges of the processing packet. The other in-the-packet film had poor fixing at base plus fog. This product had a one solution developer/fixer chemistry. It seems probable that the undeveloped films simply needed to have too much material removed for the short development time recommended for QD. QD did have low noise at 1 OD above base plus fog; however, each film had a tissue placed next to the film inside the packet. The tissue was about 10% smaller than the film and the developed film was

Volume Number

Performance

69 3

darkened around the edges of this tissue. This limited the effective area of each film by approximately 10%. CONCLUSIONS

The reference standard (autoprocessing) provided the highest speed and the highest average gradient. No significant difference in spatial resolution was found among all of the processing solutions. Rapid

IV. Image noise at base plus fog and one above base plus fog

of seven rapid radiographic

processing

SOhtiOnS

387

Access, Insta Neg/Insta Fix, and IFP had noise levels generally as low or lower than the reference standard. Although these rapid processing products can produce an overall image quality that approached that of the reference standard,‘rapid processing generally involves slower speeds and an accompanying increase in patient radiation exposure. Accordingly, there seems to be little motivation for the use of rapid manual processing solutions unless there is a compelling rationale in terms of time or convenience.

Table

Product

name

Instant Developer/ Instant Fixer Endo A & B

QD Phil-X 30” Insta Neg/lnsta IFP

Fix

0.4034

A

0.2851 0.1956 0.0790 0.0289 0.0132

B c D E F F F F F

RPX-Omat

0.0095

Rapid

0.0085

Product

Access

Average noise at one above base plus fog

name

Statistical grouping

Phil-X 30” Instant Developer/ Instant Fixer Endo A & B

0.1750 0.1638

A B

0.0608

IFP Rp X-Omat

0.0534 0.0496 0.0309

Rapid

0.0257

C C C D E E E E E

QD Access

Insta Neg/Insta

Fix

0.0255

REFERENCES 1, Van de Poe1 ACM, The Kodak Dx 80R replenisher as quick developer. J Am Dent Assoc 1973;86:401-3. 2. Manson-Hing LR, Turgut E. Evaluation of film processing with concentrated solutions, ORAL SURG ORAL MED ORAL PATHOL 1973;36:280-6. 3. Pestritto ST, Anderson SJ, Braselton JA. Comparison of diagnostic radiographs produced by five rapid processing technics. J Am Dent Assoc 1974;89:353-5. 4. Manson-Hing LR, Monier PY. Radiographic densitometric evaluation of seven processing solutions. ORAL SURG ORAL MED ORAL PATHOL 1975;39:493-501. 5. Manson-Hing LR, Pate1 JR. Densitometric evaluation of quick x-ray developing solutions. ORAL SURG ORAL MED ORAL PATHOL 1977;43:467-72. 6. Thunthy KH, Weinberg R. Comparison of films processed in automatic and manual1 processors. ORAL SURG ORAL MED ORAL PATHOL 1980;50:479-83. MM, Tamse A. Densitometric evaluation of 7. Kaffe I, Littner three x-ray films with five different developing solutions. ORAL SURC ORAL MED ORAL PATHOL 1984;57:207-11. 8. Sensitometric properties of x-ray films. Rochester, New York: Eastman Kodak Co. 9. Webber RL, Koziol PH. Radiographic spatial frequencies essential to the diagnosis of incipient interproximal lesions. J Dent Res 1976;55:805-11. IO. Clark W. ed. Physical and photographic principles of medical radiography. New York: J. Wiley & Sons Inc, 1968:22-36. Reprint requests 10. Donna Maddalozzo, DDS, MS Assistant Professor of Periodontics Northwestern University Dental School 240 E. Huron Chicago, Illinois 606 1 l-2909