Digital subtraction radiography for assessment of simulated root resorption cavities. Performance of conventional and reverse contrast modes.

A previous study of the sensitivity and accuracy of a standardized radiographic technique for the disclosure of root cavities in a cadaver material indicated that it was not possible to perceive small artificial "resorption" cavities. Using the same material, the aim of the present study was to evaluate whether the use of subtraction radiography would improve the detection of root cavities. In an autopsy material of five mandibular blocks each containing two premolars, small, medium, and large cavities were drilled in the cervical, middle, and apical thirds of the proximal and oral root surfaces. Each jaw block was radiographed before (B) and after (A) cavity preparation with three different exposure times resulting in light, medium, and dark film densities. The radiographs were digitized. Digital subtraction was performed between the A- and B images of varying densities by a computer program developed for dental subtraction radiography. Conventional and reverse contrast modes of the subtraction image were assessed independently by four observers. The results showed small inter- and intraobserver differences in diagnostic accuracy for assessment of total number of root cavities. Original film density did not influence the diagnostic performance in the resulting subtraction image. Contrast mode in the subtraction image influenced diagnostic performance as the majority of observers did best with the reverse contrast mode (p < 0.05). Some of the small root cavities were disclosed by the subtraction technique, but overall accuracy was not increased compared to conventional radiography.     

Personal computer equipment for dental digital subtraction radiography vs. industrial computer equipment and conventional radiography

A "low-cost" personal computer (PC) system used to digitize dental radiographs was tested by assessing the accuracy of its subtraction images versus those of "high-cost" industrial equipment and conventional radiography. Subtraction images were made of artificial lesions in human femur bone and subsequently evaluated by students and teachers. The observations were analyzed in terms of true positive and false positive reports. "Low-cost" and "high-cost" subtraction images revealed only small differences in diagnostic accuracy. Compared to conventional radiography, the diagnostic accuracy of the subtraction images with the "low-cost" PC system was significantly higher for all observers. The interexaminer variance was similar for the subtraction and the conventional images for both students and teachers, except for a significantly reduced interexaminer variance for the teachers concerning the true positive reports with the "low-cost" PC subtraction technique.     

Assessment of simulated internal resorption cavities using digital and digital subtraction radiography: a comparative study

Abstract – Aim: To compare the diagnostic accuracy of digital radiography with that of digital subtraction radiography in the detection of simulated internal resorption cavities. Materials and Methods: Simulated internal resorption cavities of varying sizes were created using round burs in 18 single‐rooted teeth with visible pulp chamber, which had been extracted from dentate dry mandibles and split into two halves in a mesio‐distal direction. Resorption cavities were created in the buccal half of the root in the cervical, middle, and apical third. Digital radiographs were taken from three different horizontal view angles before and after the creation of the cavities. This process was followed by digital subtraction radiography to evaluate their detection. Seven experienced observers and all specialists in endodontics were asked to examine the digital and digital subtraction images for the presence of the cavities. The data were analyzed using SPSS 14. Results: The overall sensitivity of digital subtraction radiography was superior to digital radiography and with statistically better results for all cavities regardless of their location (cervical, middle, apical third) (P < 0.05). The detection of the cavities was affected by the root third in which they were located. Cavities in the apical third were more easily detected compared with those in the middle or cervical third of the root. Small‐sized lesions (0.5 mm, 0.6 mm) in the middle and apical third were more frequent and more easily detected using subtraction imaging. Conclusion: Digital subtraction radiography is superior to digital radiography for the detection and monitoring of the progress of internal root resorption.     

Radiographic assessment of simulated root resorption cavities

Abstract A study into the sensitivity and accuracy of a standardized radiographic technique for the disclosure of root resorption cavities was performed in a cadaver material. Film contrast and horizontal angulation were varied in order to identify factors in radiographic exposure which resulted in the greatest diagnostic reliability. In an autopsy material of 5 jaw blocks containing both mandibular premolars, “small, medium and large” cavities simulating root resorptions of 0.6, 1.2 and 1.8 mm in diameter and 0.3, 0.6 and 0.9 mm in depth, respectively, were drilled at the cervical, middle and apical thirds of the proximal and oral root surfaces of the premolars. Cavity locations were distributed to ensure an equal number of locations with and without cavities and an equal number of cavities of each size. Results of the investigation indicated that the small cavities were never visualized, nor were 6 out of 13 medium cavities nor 1 out of 13 large cavities; that cavities located proximally were more readily seen than those located orally and that there was no clif Terence in cavity visualization between cavities on the apical, middle or cervical thirds of the roots; high density (contrast) films allowed the best cavity visualization. Finally, radiographs from the time of injury (i.e. preresorption radiographs) as well as radiographs taken at various horizontal angulations were found to be of importance in order to increase the possibility of cavity visualization.     

Assessment of external root resorption using digital subtraction radiography.

Digital subtraction radiography was investigated for its capability to detect and quantify experimentally produced external root resorptive defects in teeth. Using a long source to object X-ray technique and E-speed film, serial radiographs of teeth with artificial lesions in a dry human skull (soft tissue simulated) were obtained. Receiver operating characteristic analysis was used to evaluate the diagnostic performance for each imaging system (conventional versus subtraction). To explore the quantitative assessment potential of digital subtraction radiography, images were produced after sequential demineralization by HCl. The acid solution was analyzed for calcium concentration by atomic absorption spectrophotometry. Three-dimensional histogram quantification for each subtracted image was performed. In overall performance for detecting experimentally produced external root resorption, digital subtraction radiography was found to be significantly superior to conventional radiography. In addition, digital subtraction radiography can provide quantification of experimentally produced external root resorptive defects.     

The use of a radiopaque contrast medium in endodontic radiography

A series of in vitro studies were carried out to investigate the use and application of a radiopaque contrast medium in conventional periapical dental radiography for the diagnosis and evaluation of root canal systems. The water-soluble radiopaque contrast medium was introduced into the root canals of 30 first permanent maxillary and 30 first permanent mandibular molar teeth. The radiographic images of these teeth with and without radiopaque contrast medium in the root canal systems were compared and contrasted. Further comparisons were made with the same teeth rendered transparent. The results indicate that by standardizing the diagnostic criteria the inter-examiner reliability was in good agreement; it was independent of the radiographic technique used. The validity of the radiographs was enhanced by the use of the radiopaque contrast medium. The results confirm that, with the use of a radiopaque contrast medium, images of root canal systems are easier to read and interpret than plain radiographic images of root canal systems. The use of radiopaque contrast medium in endodontic radiography may be a valuable aid in the diagnosis and evaluation of root canal systems. This system would complement rather than replace plain radiography.     

Basic study of one-shot dual energy subtraction sialography: Evaluation method of optimal conditions

The author produced a bone-iodine step (BI-step) phantom and performed a basic experiment using it in one-shot dual energy subtraction sialography by computed radiography (CR). There are many parameters of energy subtraction such as the tube voltage, filter, Imaging Plate (IP), grid, contrast medium, and image processing. In this study, the author evaluated the influence of tube voltage (50 ∼100 kVp), copper (Cu) and tin (Sn) filters, and the iodinated contrast medium on the resultant image. The conditions of optimal subtraction were theoretically determined, and the separation between bone and iodine reached a maximum at a tube voltage of 50kVp with a Cu-filter of 0.8 mm in this investigation. The correctness of these conditions were confirmed on actual subtraction images. These results appear to be applicable to digital subtraction sialography following a further combination with the other parameters.     

The effect of in-vivo-occurring errors in the reproducibility of radiographs on the use of the subtraction technique

A device for serial radiography in maxillary and mandibular premolar and molar regions was developed. Radiographs of 9 patients were made during a period of 1 year. When testing the device, the influence of the time interval between the radiographs and the influence of the construction of the device on the reproducibility of the X-ray images were determined. An increase of the time interval between radiographs reduced the reproducibility. The use of bilateral bite blocks improved the reproducibility of the X-ray images in comparison with the images obtained with a device with a one-sided bite block. Errors in the reproducibility caused differences in the image geometry of radiographs. The in-vivo-found differences were studied for their effect on the detection threshold of observers using photographic subtraction radiography. An increase of the differences in image geometry between the radiographs resulted in a higher detection threshold and a higher % of false positive decisions. It appeared that very small differences between clinical radiographs, corresponding with an angulation error of 0.7 degrees, can be tolerated in order to prevent the occurrence of high numbers of type-I errors. The % of radiographs, which met this requirement and could be used for photographic subtraction radiography, was 55%, when taken at time intervals of 1 year.     

Direct digital radiography for the detection of periapical bone lesions: a clinical study

Abstract The aim was to compare the observer performance of direct digital radiography, with and without image processing, with that of conventional radiography, for the detection of periapical bone lesions. For 50 patients, a conventional periapical radiograph using E-speed film was taken. Then, a direct digital image of the same area was made. The images presenting the periapical bone tissue of 59 roots were assessed by seven observers using a 5-point confidence scale. The digital images were first presented as original images, with default contrast and brightness set by the computer system. Following this, the observers were allowed to use the processing facilities for greyscale treatment. The results for original and processed direct digital images and for conventional radiographs were compared by Receiver Operating Characteristic (ROC) analysis. The area under the ROC curve, calculated as P(A) value, was 0.88 for conventional film, 0.82 for original digital images and 0.78 for processed images. Corresponding A_z values were slightly higher, 0.89, 0.84 and 0.81. Statistically significant differences between ROC areas calculated as P(A) values for the methods were found. Comparison between A_z values showed no significant differences between conventional radiographs and original digital images, whereas the difference between A_z values for original and processed digital images was still significant. It was concluded that conventional film radiography performed slightly better for the detection of periapical bone lesions than direct digital radiography and that image processing did not improve the observer performance.     

Personal computer equipment for dental digital subtraction radiography vs. industrial computer equipment and conventional radiography.

A "low-cost" personal computer (PC) system used to digitize dental radiographs was tested by assessing the accuracy of its subtraction images versus those of "high-cost" industrial equipment and conventional radiography. Subtraction images were made of artificial lesions in human femur bone and subsequently evaluated by students and teachers. The observations were analyzed in terms of true positive and false positive reports. "Low-cost" and "high-cost" subtraction images revealed only small differences in diagnostic accuracy. Compared to conventional radiography, the diagnostic accuracy of the subtraction images with the "low-cost" PC system was significantly higher for all observers. The interexaminer variance was similar for the subtraction and the conventional images for both students and teachers, except for a significantly reduced interexaminer variance for the teachers concerning the true positive reports with the "low-cost" PC subtraction technique.     

Subtraction radiography for the diagnosis of periapical bone lesions

Abstract Subtraction and conventional radiography were evaluated for the diagnostic potential to assess periapical bone lesions. The periapical region of dry human mandibles was radio-graphically examined, subjectively evaluated and measured by ¹²⁵I absorptiometry before and after the creation of bone defects. Both conventional radiographs and subtraction images made from the conventional radiographs after digitization were interpreted by 10 dentists. Receiver operating characteristic (ROC) analysis technique was used to compare the two techniques. There was a higher diagnostic accuracy using subtraction technique. For a lesion depth corresponding to < 2 mm of compact bone, there was a clear difference between the techniques, but for deeper lesions the conventional technique gained force. The subtraction technique was significantly superior for lesions confined to cancellous bone. The statistical difference in the diagnostic utility of subtraction compared with conventional technique was found to be less for lesions of the cortical bone. Therefore, the conclusion is that subtraction radiography improves the detection of small lesions in the periapical bone area.     

Detection of vertical root fractures using digitally enhanced images: reverse‐contrast and colorization

Abstract – Root fracture diagnosis is a clinical difficulty that in most cases can only be detected through radiography. The objective of this study was to compare the diagnostic accuracy of two types of digitally enhanced images (reverse‐contrast and colorization) with original digital radiographies in detecting experimental root fractures. Two hundred extracted single‐rooted human teeth were endodontically instrumented and then divided in two groups, one control group and one test group, including fractured teeth. Vertical root fractures were experimentally made in the fractured group. The digital image of each tooth was taken, using the paralleling technique. There were three groups of images: (i) original, (ii) reverse contrast, and (iii) colorized. Three experienced dental specialists examined the images with no prior knowledge of the distribution of the root fractures. Two‐way analysis of variance was used to assess the differences in accuracy, sensitivity, and specificity of each technique in detecting root fractures. Cohen’s kappa coefficients were calculated to investigate the degree of interobserver agreement. The accuracy, sensitivity, and specificity of original images were 67.4%, 66.7%, and 68%, respectively; these amounts were 61.5%, 61%, and 65.5% in reverse contrast images and 66.4%, 70.7%, and 62% in colorized digital radiography. The original images had the best inter observer kappa coefficients (between 0.45 and 0.55). The results showed that the accuracy of original images is better than reverse contrast and colorized images. Use of reverse‐contrast and colorization digital images in root fracture detection should be regarded as an adjunct to other diagnostic methods not as a highly critical diagnostic aid.     

直接数字成像技术在龋病诊断中的应用研究

探讨牙科直接数字成像技术诊断龋病可行性。方法采离体带牙人头颅骨,根据图像质量确定牙科直接数字成像仪的曝光时间,然后运用该条件在临床上对无龄讶和龋牙摄像,并在图像质量和诊断准确性上与传统牙片进行比较。结果：①确定了直接数字成像在不同牙位的最佳曝光时间。②直接数字图像和传统牙片在铪 格率和龋病诊断准确性上均无差异,但图像优秀率前者高于后者。结结论Ｌ直接数字成像技术可用于临床龋病诊断。     

Subtraction radiography of interradicular bone lesions.

Subtraction and conventional radiography were evaluated for their diagnostic potential to assess interradicular bone lesions in the mandibular premolar region. Both conventional radiographs and subtraction images were interpreted by 10 observers. The receiver-operating characteristic (ROC) technique was used to compare the two techniques. The diagnostic validity was higher for the subtraction technique, both for lesions confined to cancellous bone and for lesions including the cortical bone, than for the conventional technique. For bone defects confined to cancellous bone the diagnostic accuracy was lower than those reported from periapical bone lesions irrespective of whether subtraction or conventional radiography was used. We conclude that subtraction radiography improves the detectability of bone lesions, shallow ones in particular. Lesions in the interradicular bone are more difficult to detect than those in the periapical bone.     

Intraoral radiography using dry film

The feasibility of intraoral radiography using an industrial dry film in combination with each of four different kinds of intensifying screens was investigated. The contrast characteristics, resolution, granularity, and the radiographic image quality of normal anatomical features were compared using this technique and conventional periapical film. The physical characteristics of the images obtained using the industrial dry film were markedly inferior to those of the images obtained using the conventional periapical film. However, in studying the diagnostic value of normal anatomical features, there was no significant difference between the two techniques. This finding suggests that the industrial dry film employing an intensifying screen can be used for intraaoral radiography.     

Effects of exposure reduction on the accuracy of an intraoral photostimulable-phosphor imaging system in detecting incipient proximal caries

Digital imaging systems for use in intraoral radiography are becoming common in clinical practice, although its physical properties such as resolution and available dynamic range may be inferior to conventional film systems. The purpose of this study was to determine the diagnostic accuracy in detecting incipient proximal caries using a digital system with storage phosphor plate (Digora®) in comparison with a conventional intraoral film (Kodak Ektaspeed Plus®). Thirty-one extracted upper premolars were selected. Of the 62 surfaces, 33 had proximal caries with discoloration or incipient lesions, and the rest showed no evidence of caries verified on strict inspection using fiber-optic transillumination. All teeth were radiographed following the paralleling technique (60 kV, 40 cm focus-to-film distance). Exposure was adjusted to Ektaspeed Plus film, while reduced to 1/2, 1/4, and 1/8 on Digora®. The films and digital images were evaluated by three observers, using a confidence rating for the presence of caries. On Digora®, the observers could control contrast and brightness. The results showed that Digora® had better performance in detecting caries than the film, even when the exposure was used for the film, although there were no statistically significant differences. The results suggest that the storage phosphor plate system may be used clinically to diagnose incipient proximal caries, while reducing the exposure to the patient.     

Endodontic measurements in digital radiographs acquired by a photostimulable storage phosphor system

Abstract Digora® is a newly developed digital system for intraoral radiography utilizing photostimulable storage phosphor image plates. The aim was to test the 相似文献   

Evaluation of chronic periapical lesions by digital subtraction radiography by using Adobe Photoshop CS: a technical report

The purpose of this study was to describe a new technique by using Adobe Photoshop CS (San Jose, CA) image-analysis software to evaluate the radiographic changes of chronic periapical lesions after root canal treatment by digital subtraction radiography. Thirteen upper anterior human teeth with pulp necrosis and radiographic image of chronic periapical lesion were endodontically treated and radiographed 0, 2, 4, and 6 months after root canal treatment by using a film holder. The radiographic films were automatically developed and digitized. The radiographic images taken 0, 2, 4, and 6 months after root canal therapy were submitted to digital subtraction in pairs (0 and 2 months, 2 and 4 months, and 4 and 6 months) choosing "image," "calculation," "subtract," and "new document" tools from Adobe Photoshop CS image-analysis software toolbar. The resulting images showed areas of periapical healing in all cases. According to this methodology, the healing or expansion of periapical lesions can be evaluated by means of digital subtraction radiography by using Adobe Photoshop CS software.     

Assessment of a contrast medium as an adjunct to endodontic radiography

AIM: To assess if a contrast medium improved diagnostic yield of endodontic radiographs. METHODOLOGY: Forty-five extracted mandibular premolar teeth were radiographed in bucco-lingual and mesio-distal planes. Access cavities were prepared, pulpal tissue extirpated and Ultravist contrast medium introduced under pressure. Radiographs were retaken and the teeth cleared following perfusion with India ink. Three examiners assessed all the films for: number of roots, number of root canals, curvature of root and/or root canal, presence of lateral canals, presence of a single foramen or apical delta and the presence or absence of canal obstructions. The examiners' interpretations were compared with the anatomy revealed by clearing. RESULTS: Kappa scores were calculated for each of the examiners, for each set of radiographs, to assess the level of intra- and inter-examiner agreement. Only moderate agreement was found throughout (kappa = 0.40-0.61). For multiple root canals a false-positive result was significantly more likely with contrast (P < 0.05). The use of contrast did not significantly improve the sensitivity of diagnosis of lateral canals or a single apical foramen. Contrast significantly increased the risk of falsely perceiving lateral canals (P < 0.002). Overall there was no statistically significant difference in the overall assessment of the anatomy of the root canals using contrast or plain radiographs (P > 0.2). CONCLUSIONS: Plain film radiographs confidently predict the presence of root or canal curvature but apical anatomy was assessed accurately in only 46% of cases. Plain radiographs were insensitive in assessing the number of root canals present, the presence of lateral canals and the occurrence of canal obstructions. The use of Ultravist contrast medium to improve diagnosis of root canal morphology of premolars is not supported.     

Quantitative digital subtraction radiography for the assessment of peri‐implant bone change

The purpose of this study was to develop a digital subtraction technique to assess peri-implant bone change. The method uses subtraction radiography to enhance visualization of the area of change that has occurred between radiographic examinations, and superimposes the area of change on the original radiographs. Furthermore, a reference wedge allows calculation of the mass of the lesion. The method was validated using 21 small bony chips placed on 3 different skulls prior to the first radiograph. The chips were removed, a second radiograph taken, and the images subtracted. A morphologic method was used to isolate the lesion and the change in bone mass calculated. Overall, there was excellent correlation between the calculated lesion mass (mg) and actual lesion mass (r2 > 0.90). The utility of the method was demonstrated using a case that experienced implant failure. These data indicate that quantitative digital subtraction radiography may be of value in measuring peri-implant bone change in root form implants.