Apirum Janhom - Academia.edu (original) (raw)

Papers by Apirum Janhom

Research paper thumbnail of Dental radiography quality assurance practice in Northern Thailand

Oral Surgery Oral Medicine Oral Pathology Oral Radiology and Endodontology, 2005

most commonly exposed dental radiographs. Conventional film positioning devices typically provide... more most commonly exposed dental radiographs. Conventional film positioning devices typically provide no shielding.

Research paper thumbnail of A quantitative analysis of dental radiography quality assurance practices among North Carolina dentists

Oral Surgery Oral Medicine Oral Pathology Oral Radiology and Endodontology, 1998

Objective. The purpose of this study was to assess the level of compliance with dental radiograph... more Objective. The purpose of this study was to assess the level of compliance with dental radiography quality assurance recommendations on the part of dental practitioners in the state of North Carolina and to determine whether the age of the practice was an influential factor affecting compliance.

Research paper thumbnail of Effect of noise on the compressibility and diagnostic accuracy for caries detection of digital bitewing radiographs

Community Dentistry and Oral Epidemiology, 1999

To determine the eect of noise on the compressibility and the diagnostic accuracy for caries dete... more To determine the eect of noise on the compressibility and the diagnostic accuracy for caries detection of digital bitewing radiographs. Methods: Bitewing radiographs of patients were obtained with a storage phosphor (Digora, Soredex, Helsinki, Finland) and compressed at dierent JPEG compression levels (2, 27, 53 and 128). A just noticeable dierence study was performed to select a compression level to study the added noise eect. Gaussian noise was added at low, medium, and high levels to both the original and compressed images. Seven observers examined the selected approximal surfaces to identify the caries depth. ROC analysis was performed together with ANOVA at P=0.05. Results: The compressibility of the images decreased as the noise level increased. ROC analysis revealed no signi®cant dierence between the original and compressed images within the same noise level (P40.06). With added noise compressed/decompressed images had a higher A Z than the corresponding original images. Conclusions: JPEG compression at level 27 can be used without a signi®cant deterioration in diagnostic accuracy. Compression at this level seemed to reduce the eect of noise to some extent.

Research paper thumbnail of Effect of noise on the compressibility and diagnostic accuracy for caries detection of digital bitewing radiographs

Dentomaxillofacial Radiology, 1999

To determine the eect of noise on the compressibility and the diagnostic accuracy for caries dete... more To determine the eect of noise on the compressibility and the diagnostic accuracy for caries detection of digital bitewing radiographs. Methods: Bitewing radiographs of patients were obtained with a storage phosphor (Digora, Soredex, Helsinki, Finland) and compressed at dierent JPEG compression levels (2, 27, 53 and 128). A just noticeable dierence study was performed to select a compression level to study the added noise eect. Gaussian noise was added at low, medium, and high levels to both the original and compressed images. Seven observers examined the selected approximal surfaces to identify the caries depth. ROC analysis was performed together with ANOVA at P=0.05. Results: The compressibility of the images decreased as the noise level increased. ROC analysis revealed no signi®cant dierence between the original and compressed images within the same noise level (P40.06). With added noise compressed/decompressed images had a higher A Z than the corresponding original images. Conclusions: JPEG compression at level 27 can be used without a signi®cant deterioration in diagnostic accuracy. Compression at this level seemed to reduce the eect of noise to some extent.

Research paper thumbnail of Scanning resolution and the detection of approximal caries

Dentomaxillofacial Radiology, 2001

Objective: To determine a proper scanning resolution for digitizing bitewing radiographs in the d... more Objective: To determine a proper scanning resolution for digitizing bitewing radiographs in the detection of approximal caries. Methods: Fifty-two premolars and 48 molars were mounted in blocks and imaged on conventional ®lm (Ektaspeed Plus, Eastman-Kodak, Rochester, NY USA) simulating a bitewing projection. The 15 bitewing radiographs were then scanned with a¯atbed scanner at three resolutions 150, 300 and 600 d.p.i. The digitized images were displayed in random order on a high-resolution cathode ray tube monitor. Ten observers assessed the caries status of 200 approximal surfaces. They scored lesion presence on a 5-point con®dence scale and depth on a 3-point scale. The observer's scores were compared with the results from a histological examination. Data were analysed using analysis of variance, by calculating signed observer error, absolute observer error and observer con®dence. Results: Lesion depth had a signi®cant eect on con®dence of lesion recognition. The main eect of resolution and the interaction between resolution and lesion depth were signi®cant. Pair-wise comparison showed a signi®cant dierence between resolutions in case of sound surfaces and surfaces with dentinal lesions for absolute error. The con®dence increased as the resolution increased but no signi®cant dierence was found between 300 and 600 d.p.i. The best score for depth estimation was obtained at the 300 d.p.i. scanning resolution. Conclusions: When bitewing radiographs are scanned with a¯atbed scanner, a resolution of 300 d.p.i. seems the best choice. At this resolution the digital ®le size is manageable without signi®cant loss of the information necessary for caries diagnosis.

Research paper thumbnail of Interaction between noise and file compression and its effect on the recognition of caries in digital imaging

Dentomaxillofacial Radiology, 2000

Objectives: To determine the interaction between image noise and ®le compression, with special em... more Objectives: To determine the interaction between image noise and ®le compression, with special emphasis on the accuracy of caries diagnosis. Methods: Fifty-nine bitewing radiographs of patients were taken simultaneously with Ektaspeed Plus (Eastman-Kodak, Rochester, NY, USA) ®lm without lead foil and the Digora 1 storage phosphor system (Soredex, Helsinki, Finland). Three dierent levels of Gaussian noise were added to the original digital images which were then compressed with JPEG 53. Seven observers evaluated the presence and depth of caries lesions on selected approximal surfaces on a 5-point scale. The results of JPEG 27 compression from a previous study were also included. ROC analysis was used together with multivariate analysis of variance (MANOVA). Results: JPEG 27 and 53 reduced the ®le size down to 7% and 4.6% of the original respectively. ROC curve analysis showed no signi®cant dierence between image conditions (original, JPEG 27, and JPEG 53) at the same noise level. JPEG 27 and 53 had larger A z scores than their original counterparts at the same noise level. However, MANOVA showed that for depth estimation of enamel lesions JPEG 53 resulted in a higher observer error. Conclusions: Both JPEG 53 and 27 could reduce some of the adverse eect of noise from the image by removing high spatial frequencies. JPEG 53, resulting in a compression ratio of 1 : 21, does not compromise the diagnostic performance in general. JPEG 53 compression may however aect the ability to detect enamel lesions.

Research paper thumbnail of Dental radiography quality assurance practice in Northern Thailand

Oral Surgery Oral Medicine Oral Pathology Oral Radiology and Endodontology, 2005

most commonly exposed dental radiographs. Conventional film positioning devices typically provide... more most commonly exposed dental radiographs. Conventional film positioning devices typically provide no shielding.

Research paper thumbnail of A quantitative analysis of dental radiography quality assurance practices among North Carolina dentists

Oral Surgery Oral Medicine Oral Pathology Oral Radiology and Endodontology, 1998

Objective. The purpose of this study was to assess the level of compliance with dental radiograph... more Objective. The purpose of this study was to assess the level of compliance with dental radiography quality assurance recommendations on the part of dental practitioners in the state of North Carolina and to determine whether the age of the practice was an influential factor affecting compliance.

Research paper thumbnail of Effect of noise on the compressibility and diagnostic accuracy for caries detection of digital bitewing radiographs

Community Dentistry and Oral Epidemiology, 1999

To determine the eect of noise on the compressibility and the diagnostic accuracy for caries dete... more To determine the eect of noise on the compressibility and the diagnostic accuracy for caries detection of digital bitewing radiographs. Methods: Bitewing radiographs of patients were obtained with a storage phosphor (Digora, Soredex, Helsinki, Finland) and compressed at dierent JPEG compression levels (2, 27, 53 and 128). A just noticeable dierence study was performed to select a compression level to study the added noise eect. Gaussian noise was added at low, medium, and high levels to both the original and compressed images. Seven observers examined the selected approximal surfaces to identify the caries depth. ROC analysis was performed together with ANOVA at P=0.05. Results: The compressibility of the images decreased as the noise level increased. ROC analysis revealed no signi®cant dierence between the original and compressed images within the same noise level (P40.06). With added noise compressed/decompressed images had a higher A Z than the corresponding original images. Conclusions: JPEG compression at level 27 can be used without a signi®cant deterioration in diagnostic accuracy. Compression at this level seemed to reduce the eect of noise to some extent.

Research paper thumbnail of Effect of noise on the compressibility and diagnostic accuracy for caries detection of digital bitewing radiographs

Dentomaxillofacial Radiology, 1999

To determine the eect of noise on the compressibility and the diagnostic accuracy for caries dete... more To determine the eect of noise on the compressibility and the diagnostic accuracy for caries detection of digital bitewing radiographs. Methods: Bitewing radiographs of patients were obtained with a storage phosphor (Digora, Soredex, Helsinki, Finland) and compressed at dierent JPEG compression levels (2, 27, 53 and 128). A just noticeable dierence study was performed to select a compression level to study the added noise eect. Gaussian noise was added at low, medium, and high levels to both the original and compressed images. Seven observers examined the selected approximal surfaces to identify the caries depth. ROC analysis was performed together with ANOVA at P=0.05. Results: The compressibility of the images decreased as the noise level increased. ROC analysis revealed no signi®cant dierence between the original and compressed images within the same noise level (P40.06). With added noise compressed/decompressed images had a higher A Z than the corresponding original images. Conclusions: JPEG compression at level 27 can be used without a signi®cant deterioration in diagnostic accuracy. Compression at this level seemed to reduce the eect of noise to some extent.

Research paper thumbnail of Scanning resolution and the detection of approximal caries

Dentomaxillofacial Radiology, 2001

Objective: To determine a proper scanning resolution for digitizing bitewing radiographs in the d... more Objective: To determine a proper scanning resolution for digitizing bitewing radiographs in the detection of approximal caries. Methods: Fifty-two premolars and 48 molars were mounted in blocks and imaged on conventional ®lm (Ektaspeed Plus, Eastman-Kodak, Rochester, NY USA) simulating a bitewing projection. The 15 bitewing radiographs were then scanned with a¯atbed scanner at three resolutions 150, 300 and 600 d.p.i. The digitized images were displayed in random order on a high-resolution cathode ray tube monitor. Ten observers assessed the caries status of 200 approximal surfaces. They scored lesion presence on a 5-point con®dence scale and depth on a 3-point scale. The observer's scores were compared with the results from a histological examination. Data were analysed using analysis of variance, by calculating signed observer error, absolute observer error and observer con®dence. Results: Lesion depth had a signi®cant eect on con®dence of lesion recognition. The main eect of resolution and the interaction between resolution and lesion depth were signi®cant. Pair-wise comparison showed a signi®cant dierence between resolutions in case of sound surfaces and surfaces with dentinal lesions for absolute error. The con®dence increased as the resolution increased but no signi®cant dierence was found between 300 and 600 d.p.i. The best score for depth estimation was obtained at the 300 d.p.i. scanning resolution. Conclusions: When bitewing radiographs are scanned with a¯atbed scanner, a resolution of 300 d.p.i. seems the best choice. At this resolution the digital ®le size is manageable without signi®cant loss of the information necessary for caries diagnosis.

Research paper thumbnail of Interaction between noise and file compression and its effect on the recognition of caries in digital imaging

Dentomaxillofacial Radiology, 2000

Objectives: To determine the interaction between image noise and ®le compression, with special em... more Objectives: To determine the interaction between image noise and ®le compression, with special emphasis on the accuracy of caries diagnosis. Methods: Fifty-nine bitewing radiographs of patients were taken simultaneously with Ektaspeed Plus (Eastman-Kodak, Rochester, NY, USA) ®lm without lead foil and the Digora 1 storage phosphor system (Soredex, Helsinki, Finland). Three dierent levels of Gaussian noise were added to the original digital images which were then compressed with JPEG 53. Seven observers evaluated the presence and depth of caries lesions on selected approximal surfaces on a 5-point scale. The results of JPEG 27 compression from a previous study were also included. ROC analysis was used together with multivariate analysis of variance (MANOVA). Results: JPEG 27 and 53 reduced the ®le size down to 7% and 4.6% of the original respectively. ROC curve analysis showed no signi®cant dierence between image conditions (original, JPEG 27, and JPEG 53) at the same noise level. JPEG 27 and 53 had larger A z scores than their original counterparts at the same noise level. However, MANOVA showed that for depth estimation of enamel lesions JPEG 53 resulted in a higher observer error. Conclusions: Both JPEG 53 and 27 could reduce some of the adverse eect of noise from the image by removing high spatial frequencies. JPEG 53, resulting in a compression ratio of 1 : 21, does not compromise the diagnostic performance in general. JPEG 53 compression may however aect the ability to detect enamel lesions.