THE MOST PRACTICAL INTRAORAL DIGITAL X-RAY IMAGING

1997 Fiscal Year Final Research Report Summary

• Project/Area Number: 08457501
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 病態科学系歯学(含放射線系歯学)
• Research Institution: TOKYO DENTAL COLLEGE
• Principal Investigator: KUROYANAGI Kinya TOKYO DENTAL COLLEGE,DEPARTMENT OF DENTISTRY,PROFESSOR, 歯学部, 教授 (60085751)
• Co-Investigator(Kenkyū-buntansha): NISHIKAWA Keiichi TOKYO DENTAL COLLEGE,DEPARTMENT OF DENTISTRY,ASSISTANT, 歯学部, 助手 (30180590) ; HAYAKAWA Yoshihiko TOKYO DENTAL COLLEGE,DEPARTMENT OF DENTISTRY,LECTURER, 歯学部, 講師 (70164928) ; WAKOH Mamoru TOKYO DENTAL COLLEGE,DEPARTMENT OF DENTISTRY,ASSISTANT PROFESSOR, 歯学部, 助教授 (70211670)
• Project Period (FY): 1996 – 1997
• Keywords: INTRAORAL / DIGITAL / RADIOGRAPHY / CHARACTERISTIC CURVE / CCD

Research Abstract

Several investigations were carried out to design the most practical intraoral digital x-ray imaging system with CCD (Charge-Coupled Device) sensor under consideration of on the response properties to x-ray.
Firstly, dark current property, gradient and dynamic range, granularity, tube voltage dependency, tube current dependency, and contrast resolution of commercially available systems were evaluated. Each system showed the difference especially in the dark current property and the dynamic range. The bit number for quantization of gray scale should be set at more than 12 to get rid of the effect of the dark current. The dynamic ranges were 1 : 25-1 : 35.
Secondly, relations between the gain value to amplify the analog output signals from the CCD sensor and the dynamic range obtained with digitization of the amplified signals were investigated using the kit for evaluation of CCD sensor properties. The dynamic range could be changed to 1 : 45, which was wider than those of the existing systems.
To decide the dynamic range required in minimum and optimize the gradient in response properties to x-ray, the x-ray contrast in the maxillary molar region was analyzed becouse the largest x-ray contrast in intraoral radiography is obtained in there. The dynamic range required was 1 : 12 at most. Therefore larger gradient, namely larger contrast resolution than those in the existing systems can be acquired by narrowing the dynamic range.