Assessment of vertical magnification ratios in digital panoramic radiography using phantoms: evaluation of DICOM metadata and calibration consistency
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Published on: March 12, 2021
Han-Gyeol Yeom1, Hyun-Gab Kim2, Yeon-Tae Kim3
1Department of Oral and Maxillofacial Radiology and Wonkwang Dental Research Institute, College of Dentistry, Wonkwang University, Iksan, 54538, Republic of Korea.
Objectives:
This study aimed to investigate the vertical magnification ratios of various digital panoramic radiography devices and assess their consistency. It also xamined the relationship between magnification ratios and Digital Imaging and Communications in Medicine (DICOM) header information to determine the potential use of key metadata in inferring or standardizing magnification corrections.
Methods:
A ball phantom with metal spheres and an implant phantom were used to assess vertical magnification ratios. Eleven panoramic radiography systems were tested, and three DICOM tags-pixel spacing, imager pixel spacing, and aspect ratio-were analyzed. Three specialists measured phantom lengths in randomized DICOM images using PACS software, repeating measurements after 4 weeks. Magnification ratios were calculated by averaging 24 measurements per sample and comparing them to actual lengths.
Results:
Intra- and interobserver reliability were high (ICC > 0.99). Most devices showed magnification ratios of 0.95-1.08, whereas those of devices 3 and 9 ranged from 1.21 to 1.30. Although some magnification ratios, which were used for system-based calibration, could be indirectly inferred by dividing the imager pixel spacing value by the pixel spacing value when both values were precisely recorded, no DICOM headers explicitly provided magnification ratios.
Conclusions:
This study demonstrated that many digital panoramic radiography devices apply software-based corrections to achieve a vertical magnification ratio close to 1.0; however, inconsistencies remain across different systems. Measurement accuracy and clinical reliability can be enhanced by standardization of magnification correction methods and improved documentation in product specifications and DICOM headers, which is clinically relevant for increasing the accuracy of vertical measurements in procedures such as dental implant planning and thereby enhancing treatment predictability and patient safety.
