Computer-based Image Analysis of Natural Approximal Caries on Radiographic Films

Abstract

This paper reports on the development of computer software for automatic detection and measurement of approximal caries lesions on digital images obtained from radiographic films. If the program detects a lesion, it defines the lesion's border and measures and reports these lesion parameters: percent mineralization, area, maximum enamel penetration, and mean enamel penetration.

Two experiments are reported; both were conducted with the use of extracted human premolar teeth. In the first experiment, thin sections were obtained from 13 approximal surfaces with caries lesions. Microradiographs were made of the sections, and software measurements of the lesions were obtained from the microradiographs. The software was able to separate the lesions into two groups: those that had penetrated less than 100% of the enamel and those that had penetrated 100% of the enamel. The software measurements agreed with evaluation of lesion penetration by polarized light microscopy of the thin sections.

In the second experiment, simulated clinical radiographs were made of 16 approximal surfaces, 12 with lesions and four without. Thin sections were obtained for microradiography. Software was used for automatic detection and measurement of the lesions on both types of film. The ability of the software to detect the lesions on the clinical films was compared with that of 10 experienced clinicians. Correlations of the same parameter from the two types of radiographic films were statistically significant, 0.86 ≤ r ≤ 0.95 and p < 0.05. The coefficients of variation were low for both microradiographs, 0.4–2.3%, and for clinical films, 0.7–8.5%. A receiver-operating characteristic (ROC) curve was constructed for the clinicians and the software. The software was more accurate than the clinicians in deciding whether or not a lesion was present. In conclusion, under the conditions of this experiment, the software was able accurately to decide whether caries was present and, when present, to provide information about the extent of the lesion which was in good agreement with that from microradiographs.

Get full access to this article

View all access options for this article.

References

BILLE

, and THYLSTRUP

(1982): Radiographic Diagnosis and Clinical Tissue Changes in Relation to Treatment of Approximal Carious Lesions, Caries Res 16: 1–6.

GRÖNDAHL

H.-G.

(1987): Radiographic Assessment of Caries and Caries Progression. In: Quality Evaluation of Dental Restorations, Chicago: Quintessence, pp. 151–168.

HEAVEN

T.J.

; FIRESTONE

A.R.

; and FEAGIN

F.F.

(1990): Quantitative Radiographic Measurement of Dentinal Lesions, J Dent Res 69: 51–54.

MARTHALER

T.M.

, and GERMANN

(1970): Radiographic and Visual Appearance of Small Smooth Surface Caries Lesions Studied on Extracted Teeth, Caries Res 4: 224–242.

METZ

C.E.

(1978): Basic Principles of ROC Analysis, Seminars in Nuclear Medicine VIII: 283–298.

OKANO

; HUANG

H.-J.

; and NAKAMURA

(1985): Diagnostic Accuracy on Detection of Proximal Enamel Lesions in Nonscreen Radiographic Performance, Oral Surg Oral Med Oral Pathol 59: 543–547.

PITTS

N.B.

(1983): Monitoring of Caries Progression in Permanent and Primary Posterior Approximal Enamel by Bitewing Radiography, Commun Dent Oral Epidemiol 11: 228–235.

PITTS

N.B.

(1984): Detection and Measurement of Approximal Radiolucencies by Computer-aided Image Analysis, Oral Surg Oral Med Oral Pathol 58: 358–366.

PITTS

N.B.

(1987): Detection of Approximal Radiolucencies in Enamel: A Preliminary Comparison between Experienced Clinicians and an Image Analysis Method, J Dent 15: 191–197.

10.

PITTS

N.B.

, and RENSON

C.E.

(1985): Reproducibility of Computer-aided Image-analysis-derived Estimates of the Depth and Area of Radiolucencies in Approximal Enamel, J Dent Res 64: 1221–1224.

11.

PITTS

N.B.

, and RENSON

C.E.

(1986): Further Development of a Computer-Aided Image Analysis Method of Quantifying Radiolucencies in Approximal Enamel, Caries Res 20: 361–370.

12.

RAPER

H.R.

(1925): Practical Clinical Preventive Dentistry Based upon Periodic Roentgen-ray Examinations, J Am Dent Assoc 12: 1084–1100.

13.

RUGG-GUNN

A.J.

(1972): Approximal Carious Lesions. A Comparison of the Radiological and Clinical Appearances, Br Dent J 133: 481–484.

14.

SAS INSTITUTE, INC. (1985a): The GLM Procedure. In: SAS User's Guide: Statistics, Version 5 Edition. Cary, NC: SAS Institute, Inc., pp. 433–506.

15.

SAS INSTITUTE, INC. (1985b): The CORR Procedure. In: SAS User's Guide: Basics, Version 5 Edition. Cary, NC: SAS Institute, Inc., pp. 861–874.

16.

WHITE

S.C.

; GRATT

B.M.

; and BAUER

J.G.

(1988): A Clinical Comparison of Xeroradiography and Film Radiography for the Detection of Proximal Caries, Oral Surg Oral Med Oral Pathol 65: 242–248.