The effect of dose reduction on the detection - Dentomaxillofacial ...

RESEARCH 

<strong>The</strong> <strong>effect</strong> <strong>of</strong> <strong>dose</strong> <strong>reduction</strong> on the detection <strong>of</strong> anatomical 

structures on panoramic radiographs 

G Kaeppler *,1 , K Dietz 2 and S Reinert 3 

1 Department <strong>of</strong> Oral Radiology, School <strong>of</strong> Dental Medicine, University <strong>of</strong> Tübingen, Germany; 2 Department <strong>of</strong> Medical Biometry, 

University <strong>of</strong> Tübingen, Germany; 3 Department <strong>of</strong> Oral and Maxill<strong>of</strong>acial Plastic Surgery, University <strong>of</strong> Tübingen, Germany 

Introduction 

Objectives: <strong>The</strong> aim was to evaluate the <strong>effect</strong> <strong>of</strong> <strong>dose</strong> <strong>reduction</strong> on diagnostic accuracy using 

different screen–film combinations and digital techniques for panoramic radiography. 

Methods: Five observers assessed 201 pairs <strong>of</strong> panoramic radiographs (a total <strong>of</strong> 402 panoramic 

radiographs) taken with the Orthophos Plus w (Sirona, Bensheim, Germany), for visualization <strong>of</strong> 11 

anatomical structures on each side, using a 3-point scale 21, 0 and 1. Two radiographs <strong>of</strong> each 

patient were taken at two different times (conventional setting and setting with decreased <strong>dose</strong>, done 

by increasing tube potential settings or halving tube current). To compare the <strong>dose</strong> at different tube 

potential settings <strong>dose</strong>–length product was measured at the secondary collimator. Films with 

medium and regular intensifying screens (high and low tube potential settings) and storage phosphor 

plates (low tube potential setting, tube current setting equivalent to regular intensifying screen and 

halved) were compared. <strong>The</strong> five observers made 27 610 assessments. Intrarater agreement was 

expressed by Cohen’s kappa coefficient. 

Results: <strong>The</strong> results demonstrated an equivalence <strong>of</strong> regular screens (low tube potential setting) 

and medium screens (high and low tube potential settings). A significant difference existed between 

medium screens (low tube potential setting, mean score 0.92) and the group <strong>of</strong> regular film–screen 

combinations at high tube potential settings (mean score 0.89) and between all film–screen 

combinations and the digital system irrespective <strong>of</strong> exposure (mean score below 0.82). <strong>The</strong>re were 

no significant differences between medium and regular screens (mean score 0.88 to 0.92) for 

assessment <strong>of</strong> the periodontal ligament space, but there was a significant difference compared with 

the digital system (mean score below 0.76). <strong>The</strong> kappa coefficient for intrarater agreement was 

moderate (0.55). 

Conclusions: New regular intensifying screens can replace medium screens at low tube potential 

settings. Digital panoramic radiographs should be taken at low tube potential levels with an exposure 

equivalent at least to a regular intensifying screen. 

Dentomaxill<strong>of</strong>acial Radiology (2006) 35, 271–277. doi: 10.1259/dmfr/16653683 

Keywords: radiography, panoramic; kV setting; intensifying screens; storage phosphor radiography 

Possibilities <strong>of</strong> <strong>dose</strong> <strong>reduction</strong> in radiography have been 

provided by a new type <strong>of</strong> film, 1,2 a new screen–film 

system 3,4 or by the use <strong>of</strong> a digital system. 5,6 In the case <strong>of</strong> 

new screen–film systems or digital systems the question 

<strong>of</strong> the detection <strong>of</strong> anatomical structures becomes the focus 

<strong>of</strong> attention. 

*Correspondence to: Priv.-Doz. Dr. Gabriele Kaeppler, Department <strong>of</strong> Oral 

Radiology, School <strong>of</strong> Dental Medicine, Osianderstr. 2-8, University <strong>of</strong> Tübingen, 

D-72076 Tübingen, Germany; E-mail: gabriele.kaeppler@med.uni-tuebingen.de 

Received 30 June 2005; revised 10 October 2005; accepted 23 October 2005 

Dentomaxill<strong>of</strong>acial Radiology (2006) 35, 271–277 

q 2006 <strong>The</strong> British Institute <strong>of</strong> Radiology 

http://dmfr.birjournals.org 

Film–screen systems <strong>of</strong> speed class 200 have been 

accepted in extraoral radiography. <strong>The</strong> problem up to now 

has been that a regular screen has not been able to gain 

uniform acceptance in maxill<strong>of</strong>acial radiology because <strong>of</strong> a 

concern about a reduced recognition <strong>of</strong> clinical structures 

with this screen. 

<strong>The</strong> most commonly used tube potential is 70 kV in 

88%. 4 An increase in tube potential and a <strong>reduction</strong> <strong>of</strong> 

milliamperes could reduce the radiation <strong>dose</strong> required but 

could also result in poorer image contrast and image 

quality, whose <strong>effect</strong>s on the patient radiograph should be 

assessed.

272 

<strong>The</strong> aim <strong>of</strong> this study was to compare image quality, as 

measured by detection <strong>of</strong> anatomic structures, in panoramic 

radiographs made with different radiation <strong>dose</strong>s. Doses 

were varied by altering the image receptor (various film– 

screen combinations and digital imaging) and tube 

potential and/or tube current settings. 

Patients and methods 

Two panoramic radiographs each <strong>of</strong> 201 patients (402 

radiographs), taken in the Department <strong>of</strong> Oral Radiology <strong>of</strong> 

the Centre <strong>of</strong> Dentistry at two different times in a 

randomized order with conventional settings and with a 

reduced <strong>dose</strong>, were used for this study. Both radiographs 

were taken on the basis <strong>of</strong> current medical indication in 

accordance with the German X-ray rules. 7 No additional 

radiographs were taken for the study. 

<strong>The</strong> two radiographs <strong>of</strong> the same patient were taken 

with a high tube potential setting ($80 kV) and a low tube 

potential setting (#75 kV) and also with a high and low 

tube current setting, depending on the screen used, medium 

or regular, respectively. 

All <strong>of</strong> the radiographs were made with Orthophos Plus w 

(Sirona, Bensheim, Germany) and one <strong>of</strong> the following 

image receptor systems: Kodak T-MAT G RA films 

(Kodak, Chalon-sur-Saone, France), equipped with a 

medium intensifying screen (Ko200); Agfa Dentus Ortholux 

(Agfa, Mortsel, Belgium), equipped with a regular 

intensifying screen (plastic cassette; AgKu); Kodak 

Ektavision G, equipped with an Ektavision intensifying 

screen (regular screen, Ektav); and the DenOptix w 

(Gendex, VixWin 2000, Hamburg, Germany; low tube 

potential setting; DenO) storage phosphor system. DenOptix 

w used VixWin 2000 s<strong>of</strong>tware. <strong>The</strong> original image had a 

16-bit resolution; the images were assessed on the monitor 

with 8-bit resolution. <strong>The</strong> DenOptix w plates were scanned 

at 300 dpi. <strong>The</strong> films were developed at 358C with Agfa 

developing and fixing solution (Agfa G 334 fixer, Agfa G 

138 developer; Agfa-Gevaert, Mortsel, Belgium) in the 

Protec 45 compact developing machine (Du Pont de 

Nemours, Bad Homburg, Germany). 

<strong>The</strong> standard settings (kV, mA) resulted from previous 

<strong>dose</strong> measurements in the film plane at low and high tube 

potential-settings and previous in vitro assessments. 8 For 

the patient radiographs the kV/mA settings (mean values) 

were adjusted to 66/16 (kV/mA) and 69/15 (Kodak T-MAT 

G RA, medium screen), 70/8 (Agfa Dentus Ortholux and 

Kodak Ektavision G, both with regular screens; Denoptix w 

storage phosphor plates), 70/4 (Denoptix w ) and 80/6 

(Kodak T-MAT G RA, medium screen) and 80/5 (Agfa 

Dentus Ortholux, regular screen). As the in vitro results 

were insufficient for high tube potential settings and digital 

radiography, only 70 kV was used for the digital patient 

radiographs taken by DenOptix w . 

To compare the <strong>dose</strong> at different tube potential settings 

<strong>dose</strong>–length product (DLP) was measured at the secondary 

collimator (Quart dido/time 22P; Quart, Zorneding, 

Germany). <strong>The</strong> following exposure settings in panoramic 

radiography were used for measuring the DLP (median <strong>of</strong> 

Dentomaxill<strong>of</strong>acial Radiology 

Dose <strong>reduction</strong> and detection <strong>of</strong> anatomical structures 

G Kaeppler et al 

five measured values): 66 kV/16 mA (DLP 6.35 mGy cm, 

medium screen), 69 kV/15 mA (DLP 6.43 mGy cm, 

medium screen), 70 kV/8 mA (DLP 3.53 mGy cm, regular 

screen and storage phosphor plate), 70 kV/4 mA (DLP 

1.75 mGy cm, storage phosphor plate), 80 kV/6 mA (DLP 

3.48 mGy cm, medium screen), 80 kV/5 mA (DLP 2.91 

mGy cm, regular screen), 80 kV/4 mA (DLP 2.28 mGy cm, 

regular screen). 

Films combined with a medium screen (high and low 

tube potential settings) could be compared with films 

combined with a regular screen (high and low tube 

potential settings) and storage phosphor plates (low tube 

potential setting, tube current setting equivalent to regular 

screen and at half the <strong>dose</strong>). 

Several combinations could be distinguished from the 

paired radiographs: 

(1) Medium screen–film systems (speed class 250), low 

tube potential setting compared with high tube 

potential setting; 

(2) Medium intensifying screen compared with regular 

intensifying screen (both at low tube potential 

settings); 

(3) Regular screen–film systems (speed class 400), low 

tube potential setting compared with high tube 

potential setting; 

(4) Digital panoramic radiograph, <strong>dose</strong> in accordance 

with the regular intensifying screen and low tube 

potential setting, compared with film and regular 

intensifying screen; 

(5) Digital panoramic radiograph, <strong>dose</strong> equivalent to 

half <strong>of</strong> regular intensifying screen and low tube 

potential setting, compared with film and regular 

intensifying screen. 

Assessment <strong>of</strong> the digital panoramic radiographs was 

performed directly on the monitor screen (Monitor 21 00 

F77-T95, FlexScan F77S, EIZO; Eizo Nanao Technologies 

Inc., CA). <strong>The</strong> film radiographs were assessed using 

a film viewer (Ella Type N6.1; Fa. Ella, Mérieux, 

France). 

Assessment <strong>of</strong> the radiographs was done by five 

observers, all <strong>of</strong> whom had at least 7 years experience in 

assessing radiographs. Two <strong>of</strong> the observers were oral 

surgeons and three were training to become oral or 

maxill<strong>of</strong>acial surgeons. <strong>The</strong> procedure was in line with 

other studies assessing anatomical structures. 9–12 

<strong>The</strong> following 11 anatomical structures were assessed 

on the radiographs: Periapical region <strong>of</strong> 13 and 36, 

periodontal ligament space (PDL) <strong>of</strong> tooth 26 and 

46, floor <strong>of</strong> the maxillary sinus, floor <strong>of</strong> the nasal cavity, 

condyle, dentine–enamel junction (DEJ) <strong>of</strong> tooth 46, 

mandibular canal (ro<strong>of</strong>, floor), and the trabecular structure 

<strong>of</strong> the mandibular horizontal ramus. Three scores were 

used for assessing the radiographs (“structure well 

visible” ¼ 1, “structure partly visible” ¼ 0, “structure not 

or hardly visible” ¼ 21). 

Tooth 47 could be substituted for tooth 46 if the latter 

was crowned and, likewise, tooth 37 or 47 could be 

substituted for a missing 36. <strong>The</strong> ro<strong>of</strong> and floor <strong>of</strong> the

mandibular canal were assessed caudally to the roots <strong>of</strong> the 

last lower molar (right side). 

For control <strong>of</strong> the intraobserver and interobserver 

differences each observer had to assess 100 panoramic 

radiographs in a rerun, resulting in an additional 1100 

assessments by each observer. Altogether the five observers 

voted 27 610 times, including 22 110 in the first 

session (402 radiographs £ 11 structures £ 5 observers) 

and 5500 in the second session. 

<strong>The</strong> statistical analysis was undertaken with JMP w 

(Version 5.0.1.2; SAS Institute Inc., Cary, NC). An 

analysis <strong>of</strong> variance (with Tukey’s HSD post-hoc test, 

P , 0.05) (HSD ¼ honest significant difference) was 

performed, based on the anatomical structures, the film– 

screen combinations, the digital system, tube potential 

setting and the observers (interobserver and intraobserver 

differences). Intrarater agreement was expressed by 

Cohen’s kappa coefficient. <strong>The</strong> six-point scale as proposed 

by Landis and Koch 13 was used to interpret the kappa 

coefficient. 

Results 

Frequency <strong>of</strong> visibility scores for five film–screen 

combinations and two combinations <strong>of</strong> the storage 

phosphor system are given in Table 1. 

No statistically significant difference was found 

between panoramic radiographs at high tube potential 

settings and speed class 250 and panoramic radiographs at 

low tube potential settings and speed class 250 or 400 

(Table 2). <strong>The</strong> assessment revealed no <strong>reduction</strong> in the 

detection <strong>of</strong> anatomical details (Tukey HSD-test, 

P , 0.05). <strong>The</strong> panoramic radiographs <strong>of</strong> patients were 

<strong>of</strong> equal quality for regular intensifying screens at low tube 

potential settings and medium intensifying screens at low 

and high tube potential settings (Figure 1, Table 2). 

<strong>The</strong>re was a significant difference between the medium 

film–screen combination at a low tube potential setting 

(mean score 0.92) and the regular film–screen combination 

at 80 kV (AgKu80/5, mean score 0.89) and the 

storage phosphor system at 70 kV and exposure equivalent 

to a regular intensifying screen or half <strong>of</strong> it (DenO70/8, 

DenO70/4; mean score below 0.821; Table 2). 

Table 1 Frequency <strong>of</strong> scores for five film–screen combinations and two 

combinations <strong>of</strong> the storage phosphor system 

System kV mA p(1) p(0) p(21) n 

DenO 70 4 0.820 0.153 0.0270 1595 

DenO 70 8 0.832 0.157 0.0108 2310 

AgKu 80 5 0.900 0.090 0.0098 2640 

Ko200 80 6 0.912 0.084 0.0036 3355 

AgKu 70 8 0.913 0.081 0.0063 8855 

Ektav 70 8 0.924 0.070 0.0063 1595 

Ko200 66/69 15, 16 0.924 0.072 0.0040 7260 

Total 27610 

p(1), structure well visible; p(0), structure partly visible; p(21), structure 

not or hardly visible; Ektav, Ektavision G (Ektavision screen); Ko200, 

Kodak T-Mat G RA (medium screen); AgKu, Agfa Dentus Ortholux 

(regular screen, plastic cassette); DenO, DenOptixw storage phosphor 

radiography system 


G Kaeppler et al 273 

Table 2 Mean scores for the seven systems (n ¼ 27610 scores) 

Abbreviation System * * * 

Mean 

scores 

Ko200 Medium film–screen, 66 kV, 

69 kV 

A 0.920 

Ektav Regular film–screen, 70 kV A B 0.918 

Ko200 Medium film–screen, 80 kV A B 0.908 

AgKu Regular film–screen, 70 kV A B 0.907 

AgKu Regular film–screen, 80 kV B 0.890 

DenO Storage phosphor plate, 70 kV C 0.821 

DenO Storage phosphor plate, 70 kV 

(1/2 mA) 

C 0.793 

Ektav, Ektavision G (Ektavision screen); Ko200, Kodak T-Mat G RA 

(medium screen); AgKu, Agfa Dentus Ortholux (regular screen, plastic 

cassette); DenO, DenOptixw storage phosphor radiography system; 1/2 

mA, mA halved 

*Levels not connected by the same letter are significantly different. <strong>The</strong> 

same letters (A, B, C) in front <strong>of</strong> the row mean scores indicate that there 

are no significant differences among those rows 

<strong>The</strong> Kodak T-MAT G RA film (Ko200, 66 kV, 69 kV) 

got a poor assessment in 4 parts per thousand 

( p(21) ¼ 0.0040), the Ektavision (Ektav) and Ortholux 

(AgKu) films in 6.3 parts per thousand ( p(21) ¼ 0.0063), 

i.e. one-third worse than Kodak T-MAT G RA (medium 

intensifying screen). Nevertheless the differences in parts 

per thousand were small (Table 1). 

When assessing the anatomical structures on the 

panoramic views there were significant differences 

between the specific combinations with films or storage 

phosphor radiography, particularly concerning the periapical 

region 13 (Table 3; Ektavision, mean score 0.952; 

DenOptix 70/8, mean score 0.743), the floor and ro<strong>of</strong> <strong>of</strong> the 

mandibular canal (Table 4; Kodak T-MAT G, at 69 kV, 

mean score 0.933; Kodak T-MAT G, 80 kV, mean score 

0.682. DenOptix 70/4, mean score 0.724 and 0.352), and 

the floor <strong>of</strong> the nasal cavity (Table 5; Ektavision, mean 

score 1.000, DenOptix 70/8, mean score 0.867). 

<strong>The</strong> periapical region <strong>of</strong> 13 was not visible in equal 

quality with all systems, a fact shown by the significant 

differences between the digital system and almost all film– 

screen combinations (Table 3). Only in comparison with 

the medium screen–film combination exposed with high 

tube potential (Ko200, 80 kV 6 mA, mean score 0.846) did 

the digital system show no significant difference (DenO 

70/4, mean score 0.766, Tukey HSD test, P , 0.05). 

In assessing the floor <strong>of</strong> the mandibular canal there was 

a significant difference between the DenOptix w storage 

phosphor radiographs exposed with half <strong>of</strong> the <strong>dose</strong> <strong>of</strong> a 

regular screen (DenO70/4, mean score 0.724) and all film– 

screen combinations. For the ro<strong>of</strong> <strong>of</strong> the mandibular canal 

there was no significant difference between the levels <strong>of</strong> 

exposure for the digital radiographs with half or corresponding 

exposure to the regular screen (DenO70/8 and 

DenO70/4) but a significant difference between DenOptix w 

radiographs exposed with half <strong>of</strong> the <strong>dose</strong> <strong>of</strong> a regular 

screen (DenO70/4, mean score: 0.352) and nearly all film– 

screen combinations (Table 4, best combination Kodak 

T-MAT G RA, 80 kV, mean score: 0.682). 

Neither was any significant difference revealed in the 

rating <strong>of</strong> the floor <strong>of</strong> the nasal cavity and the maxillary 

sinus for DenOptix w exposed with half or equivalent 

Dentomaxill<strong>of</strong>acial Radiology

274 



Figure 1 Panoramic radiographs revealed an equal quality <strong>of</strong> medium intensifying screens (a, b) at low and (c) high tube potential settings and regular 

intensifying screens (d) at low tube potential settings 

<strong>dose</strong> <strong>of</strong> a regular screen (DenO70/8 and DenO70/4; 

Table 5). <strong>The</strong> periapical region <strong>of</strong> 36 was classified as 

clearly visible with almost all systems (Table 6), 

although there was a significant difference between the 

digital system with an exposure in line with a regular 

Table 3 Mean scores for the periapical region <strong>of</strong> 13. Total ratings: 2510 

System n * * * * Mean scores 

Ektav 70/8 145 A 0.952 

AgKu 70/8 805 A 0.917 

Ko200 66/69/16 660 A B 0.906 

AgKu 80/5 240 A B 0.896 

Ko200 80/6 305 B C 0.846 

DenO 70/4 145 C D 0.766 

DenO 70/8 210 D 0.743 



cassette); DenO, DenOptixw storage phosphor radiography system 

*Levels not connected by same letter are significantly different 

screen (DenO70/8, mean score 0.986) and almost all 

film–screen combinations. 

In assessing the periodontal ligament space <strong>of</strong> tooth 26 

and 46, dentine–enamel junction <strong>of</strong> tooth 46 and the 

trabecular structure there were no significant differences 

between the medium and regular film–screen combinations 

but a significant difference to the digital system 

(Table 7). <strong>The</strong> storage phosphor system revealed no 

significant difference with exposure <strong>of</strong> half the amount or 

equivalent to a regular screen (DenO70/8 and DenO70/4; 

Table 7). 

Assessment <strong>of</strong> the condyle revealed no significant 

difference between the two exposures <strong>of</strong> the digital system 

(DenO70/8 vs DenO70/4; Table 8) but a significant 

difference between the digital system at the lowest 

exposure (DenO 70/4, mean score 0.917) and all film– 

screen combinations. 

For the digital panoramic radiographs (storage 

phosphor plates) the results were better using a higher 

Table 4 Mean scores for the mandibular canal (floor; ro<strong>of</strong>). Total ratings: 2510 

Anatomical structure: mandibular canal (floor) Total ratings: 2510 Anatomical structure: mandibular canal (ro<strong>of</strong>) Total ratings: 2510 

System * * * * Mean scores System * * * * * Mean scores 

Ko200 66/69/16 A 0.933 Ko200 80/6 A 0.682 

AgKu 70/8 A B 0.927 Ko200 66/69/16 A B 0.626 

Ko200 80/6 A B C 0.925 Ektav 70/8 A B C 0.607 

Ektav 70/8 A B C 0.897 DenO 70/8 B C D E 0.519 

AgKu 80/5 B C 0.854 AgKu 70/8 C D 0.514 

DenO 70/8 C 0.843 AgKu 80/5 D E 0.429 

DenO 70/4 D 0.724 DenO 70/4 E 0.352 

Ektav, Ektavision G (Ektavision screen); Ko200, Kodak T-Mat G RA (medium screen); AgKu, Agfa Dentus Ortholux (regular screen, plastic cassette); 

DenO, DenOptixw storage phosphor radiography system 



Table 5 Mean scores for the floor <strong>of</strong> the nasal cavity and the maxillary sinus. Total ratings: 2510 

Anatomical structure: floor <strong>of</strong> the nasal cavity. Total ratings: 2510 Anatomical structure: floor <strong>of</strong> the maxillary sinus. Total ratings: 2510 

System * * * Mean scores System * * Mean scores 

Ektav 70/8 A 1.000 Ektav 70/8 A 1.000 

AgKu 70/8 A 0.979 Ko200 66/69/16 A 0.997 

Ko200 66/69/16 A 0.977 Ko200 80/6 A 0.997 

AgKu 80/5 A 0.975 AgKu 70/8 A 0.996 

Ko200 80/6 B 0.921 AgKu 80/5 A 0.996 

DenO 70/4 B C 0.904 DenO 70/8 A B 0.981 

DenO 70/8 C 0.867 DenO 70/4 B 0.966 


DenO, DenOptix w storage phosphor radiography system 


exposure (DenO70/8). Results for the digital radiograph 

were worst at the lowest exposure (DenO70/4) for the 

floor and ro<strong>of</strong> <strong>of</strong> the mandibular canal (Table 4, mean 

score 0.724 and 0.352), the floor <strong>of</strong> the maxillary sinus 

(Table 5; mean score 0.966), periodontal ligament space 

<strong>of</strong> tooth 26 (Table 7; mean score 0.579), dentine– 

enamel junction <strong>of</strong> tooth 46 (Table 7; mean score 

0.897), trabecular structure (Table 7; mean score 0.862) 

and condyle (Table 8; mean score 0.917). 

Table 6 Mean scores for the periapical region <strong>of</strong> 36. Total ratings: 2510 

System * * Mean scores 

DenO 70/4 A 1.000 

Ektav 70/8 A 1.000 

Ko200 66/69/16 A 1.000 

Ko200 80/6 A 1.000 

AgKu 70/8 A 0.999 

AgKu 80/5 A B 0.996 

DenO 70/8 B 0.986 





As with the periodontal ligament space <strong>of</strong> tooth 26 

and 46, dentine–enamel junction <strong>of</strong> tooth 46 and the 

trabecular structure (Table 7) there were no significant 

differences between the medium and regular film– 

screen combinations (Table 8). 

Regarding the interobserver variations, the best 

ratings were given by the first four observers (86.9– 

97.5%), followed by observer 5 (77.3%; Table 9). 

<strong>The</strong> kappa index for intraobserver agreement was only 

0.55 (Table 10) which was a moderate agreement as 

proposed by Landis and Koch 13 . <strong>The</strong> differences in 

intraobserver ratings (first assessment versus rerun) 

showed that the observed agreement <strong>of</strong> 91.5% is high 

(0.27 þ 5.45 þ 85.80%), but the high proportion <strong>of</strong> 

random agreement is the reason for the moderate kappa 

value. 

Discussion 

In the present clinical study it could be demonstrated that 

in panoramic radiography film–screen systems <strong>of</strong> speed 

Table 7 Mean scores for the periodontal ligament space <strong>of</strong> tooth 26 and 46, dentine-enamel junction <strong>of</strong> tooth 46, trabecular structure <strong>of</strong> the mandibular 

horizontal ramus. Total ratings: 2510 

Anatomical structure: periodontal ligament space <strong>of</strong> tooth 26. Total 

ratings: 2510 



Anatomical structure: periodontal ligament space <strong>of</strong> tooth 46. Total 

ratings: 2510 

System * * Mean scores System * * Mean scores 

Ko200 66/69/16 A 0.800 Ko200 80/6 A 0.915 

AgKu 70/8 A 0.798 Ko200 66/69/16 A 0.912 

AgKu 80/5 A 0.788 AgKu 80/5 A 0.892 

Ektav 70/8 A 0.786 Ektav 70/8 A 0.876 

Ko200 80/6 A 0.764 AgKu 70/8 A 0.876 

DenO 70/8 B 0.619 DenO 70/4 B 0.759 

DenO 70/4 B 0.579 DenO 70/8 B 0.733 

Anatomical structure: dentine–enamel junction <strong>of</strong> tooth 46. Total 

Anatomical structure: trabecular structure <strong>of</strong> the mandibular 

ratings: 2510 

horizontal ramus. Total ratings: 2510 

AgKu 80/5 A 1.000 Ektav 70/8 A 1.000 

Ektav 0/8 A 1.000 AgKu 80/5 A 0.996 

Ko200 66/69/16 A 0.999 AgKu 70/8 A 0.991 

AgKu 70/8 A 0.996 Ko200 66/69/16 A 0.989 

Ko200 80/6 A 0.980 Ko200 80/6 A 0.977 

DenO 70/8 B 0.929 DenO 70/8 B 0.871 

DenO 70/4 B 0.897 DenO 70/4 B 0.862 


DenO, DenOptixw storage phosphor radiography system 



276 

Table 8 Mean scores for the condyle. Total ratings: 2510 

System * * * Mean scores 

Ko200 80/6 A 0.987 

AgKu 70/8 A B 0.980 

Ektav 70/8 A B 0.979 

Ko200 66/69/16 A B 0.976 

AgKu 80/5 A B 0.971 

DenO 70/8 B C 0.943 

DenO 70/4 C 0.917 





Table 9 Differences in interobserver ratings 

% scores 

Observer 21 0 1 n 

1 0.81 1.68 97.50 5522 

2 0.38 3.57 96.05 5522 

3 0.49 5.83 93.68 5522 

4 1.77 11.30 86.93 5522 

5 0.18 22.53 77.29 5522 

Total 0.73 8.98 90.29 27610 

Table 10 Differences in intraobserver ratings, first assessment versus 

rerun. (Kappa ¼ 0.55, Std Err ¼ 0.018) 

Rerun 

Total % 

First assessment 

21 0 1 

21 0.27 0.51 0.35 

0 0.24 5.45 4.56 

1 0.24 2.58 85.80 

class 400 and distinct <strong>dose</strong> <strong>reduction</strong>s do not lead to higher 

diagnostic uncertainty. According to these results, the use 

<strong>of</strong> a film–screen system <strong>of</strong> speed class 250 and high tube 

potential or <strong>of</strong> a film–screen system <strong>of</strong> speed class 400 and 

low tube potential is meaningful in panoramic radiography 

for <strong>dose</strong> <strong>reduction</strong> (Table 2). 

Fuhrmann et al and Gregersen give priority to screens <strong>of</strong> 

speed class 200 for diagnosis. 14,15 According to Rother 

(personal communication) and Gregersen, 15 the advantage 

<strong>of</strong> the regular screen had not yet been proved and the 

differences between exposing the medium and regular 

screen had been small. 

According to the present study, however, the reason for 

this result was that the tube potential setting was reduced at 

the same time. A lower tube potential value at an 

unchanged tube current level led to a higher absorbed 

<strong>dose</strong>, which partly cancelled out the possible <strong>dose</strong> 

<strong>reduction</strong> achieved by the regular screens. 

References 

1. Conover GL, Hildebolt CF, Anthony D. A comparison <strong>of</strong> six intra-oral 

X-ray films. Dentomaxill<strong>of</strong>ac Radiol 1995; 24: 169–172. 

Dentomaxill<strong>of</strong>acial Radiology 



5500 

In the studies by Dannewitz et al 16 and Dannewitz 17 the 

image quality <strong>of</strong> anatomical structures and pathological 

findings was assessed on digital panoramic radiographs 

based on a sensor technique. <strong>The</strong> temporomandibular joint 

radiographs (program 4 and 6) at a 50% <strong>reduction</strong> in <strong>dose</strong> 

were considered to be <strong>of</strong> equal image quality. <strong>The</strong> 

radiographs exposed at <strong>dose</strong>s reduced by 50% and 65% 

(occlusal overview, lateral view, periapical radiographs <strong>of</strong> 

frontal teeth) showed an inferior subjective image quality. 

A third study by Dannewitz et al 18 reduced the <strong>dose</strong> by 

50%, to that equivalent to a medium film–screen system 

for digital panoramic radiography and sensor technique. 

This <strong>dose</strong> was equivalent to the exposure with the regular 

screens used in this study. 

<strong>The</strong> patients in Dannewitz’s study were radiographed 

twice in one session, but according to German X-ray rules, 

radiographs <strong>of</strong> patients can only be made on the underlying 

medical indication. 7 For the present study, this meant 

assessing radiographs made at two different times and 

resulting differences in the patient’s position, such as a 

different position <strong>of</strong> the tongue in relation to the hard 

palate. In this respect there is a distinct difference to in 

vitro radiographs <strong>of</strong> human skulls made at the same time. 

According to the present study, the use <strong>of</strong> both regular 

and medium intensifying screens is possible although there 

was a significant inferiority <strong>of</strong> the storage phosphor plates 

with films in panoramic radiography when exposure was 

reduced (Table 2). 

In conclusion there is, according to the present study, a 

possibility to reduce the <strong>dose</strong> in film-based panoramic 

radiography by means <strong>of</strong> newly developed regular screens 

and films in combination with a <strong>reduction</strong> <strong>of</strong> mAs 

compared with medium intensifying screens or by 

increasing tube potential and reducing mAs when using a 

medium intensifying screen. 

<strong>The</strong> new information from the study is that the medium 

intensifying screen can be used at high tube potential 

settings (DLP 3.48 mGy cm, 80 kV/6 mA) instead <strong>of</strong> at 

low tube potential settings (DLP 6.35 mGy cm, 

66 kV/16 mA) or the regular intensifying screen can be 

used at low tube potential settings (DLP 3.53 mGy cm, 

70 kV/8 mA) with the same diagnostic value. So a <strong>dose</strong> 

<strong>reduction</strong> <strong>of</strong> about 40% is possible. 

In practice the regular intensifying screens at a low tube 

potential level can replace medium intensifying screens and 

be used for all age-groups. High tube potential levels should 

not be used with regular intensifying screens. Digital 

panoramic radiographs should be taken at low tube potential 

levels with an exposure equivalent at least to a regular 

intensifying screen and with digital post-processing. 

Halving exposure compared with a regular intensifying 

screen is only possible if one accepts increased noise and 

therefore a higher error rate. <strong>The</strong>refore it is not advisable. 

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5. Farman TT, Farman AG, Kelly MS, Firriolo FJ, Yancey JM, Stewart 

AV. Charge-coupled device panoramic radiography: <strong>effect</strong> <strong>of</strong> beam 

energy on radiation exposure. Dentomaxill<strong>of</strong>ac Radiol 1998; 27: 

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6. Visser H, Rodig T, Hermann KP. Dose <strong>reduction</strong> by direct-digital 

cephalometric radiography. Angle Orthod 2001; 71: 159–163. 

7. Sonnek C, Bauer B. Die neue Röntgenverordnung (vom 18. Juni 

2002) (9th edn). Berlin: H<strong>of</strong>fmann Verlag, 2002. 

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panoramic radiographs depending on the exposure. Dentomaxill<strong>of</strong>ac 

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12. Tyndall DA, Washburn DB. Rare-earth filters in panoramic 

radiography: a means <strong>of</strong> reducing patient <strong>dose</strong> without compromising 

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