Imaging Sci Dent.  2019 Jun;49(2):131-137. 10.5624/isd.2019.49.2.131.

Factors affecting modulation transfer function measurements in cone-beam computed tomographic images

• Choi JW

• KMID: 2450179
• DOI: http://doi.org/10.5624/isd.2019.49.2.131

Abstract

PURPOSE
This study was designed to investigate the effects of voxel size, the oversampling technique, and the direction and area of measurement on modulation transfer function (MTF) values to identify the optimal method of MTF measurement.
MATERIALS AND METHODS
Images of the wire inserts of the SedentexCT IQ phantom were acquired, and MTF values were calculated under different conditions (voxel size of 0.1, 0.2, and 0.3 mm; 5 oversampling techniques; simulated pixel location errors; and different directions and areas of measurement). The differences in the MTF values across various conditions were evaluated.
RESULTS
The MTF 10 values showed smaller standard deviations than the MTF 50 values. Stable and accurate MTF values were obtained in the 0.1-mm voxel images. In the 0.3-mm voxel images, oversampling techniques of 11 lines or more did not show significant differences in MTF values depending on the presence of simulated location errors. MTF 10 values showed significant differences according to the direction and area of the measurement.
CONCLUSION
To measure more accurate and stable MTF values, it is better to measure MTF 10 values in small-voxel images. In large-voxel images, the proper oversampling technique is required. MTF values from the radial and tangential directions may be different, and MTF values vary depending on the measured area.

Keyword

Cone-Beam Computed Tomography; Radiography, Dental; Quality Control

MeSH Terms

Cone-Beam Computed Tomography
Methods
Quality Control
Radiography, Dental

Figure

• 

  Fig. 1 Modulation transfer function measurement (MTF) procedure using the MATLAB program. A. The axial image of a stainless steel wire (0.25-mm diameter) is loaded (0.1-mm voxel size). B. The image is magnified to locate the wire center. C. A 2-dimensional plot profile shows that the wire and surrounding areas were included in the region of interest. D. MTF measurement in the vertical direction with 11 oversampling lines.

• 

  Fig. 2 MTF values measured in the radial direction and tangential direction at 3 peripheral areas using the MATLAB program. A. Tangential direction in the upper area. B. Tangential direction in the upper-left area. C. Tangential direction in the left area. D. Radial direction in the upper area. E. Radial direction in the upper-left area. F. Radial direction in the left area.

Reference

1. SEDENTEXCT Guideline Development Panel. Radiation protection No 172. Cone beam CT for dental and maxillofacial radiology. Evidence based guidelines. Luxembourg: European Commission Directorate-General for Energy;2012.

2. International Commission on Radiological Protection. Managing patient dose in digital radiology. A report of the International Commission on Radiological Protection. Ann ICRP. 2004; 34:1–73.

3. Choi JW, Lee SS, Choi SC, Heo MS, Huh KH, Yi WJ, et al. Relationship between physical factors and subjective image quality of cone-beam computed tomography images according to diagnostic task. Oral Surg Oral Med Oral Pathol Oral Radiol. 2015; 119:357–365.

4. Pauwels R, Beinsberger J, Stamatakis H, Tsiklakis K, Walker A, Bosmans H, et al. Comparison of spatial and contrast resolution for cone-beam computed tomography scanners. Oral Surg Oral Med Oral Pathol Oral Radiol. 2012; 114:127–135.

5. Nakahara S, Tachibana M, Watanabe Y. One-year analysis of Elekta CBCT image quality using NPS and MTF. J Appl Clin Med Phys. 2016; 17:211–222.

6. Watanabe H, Honda E, Kurabayashi T. Modulation transfer function evaluation of cone beam computed tomography for dental use with the oversampling method. Dentomaxillofac Radiol. 2010; 39:28–32.

7. Ozaki Y, Watanabe H, Nomura Y, Honda E, Sumi Y, Kurabayashi T. Location dependency of the spatial resolution of cone beam computed tomography for dental use. Oral Surg Oral Med Oral Pathol Oral Radiol. 2013; 116:648–655.

8. Bamba J, Araki K, Endo A, Okano T. Image quality assessment of three cone beam CT machines using the SEDENTEXCT CT phantom. Dentomaxillofac Radiol. 2013; 42:20120445.

9. Elkhateeb SM, Torgersen GR, Arnout EA. Image quality assessment of clinically-applied CBCT protocols using a QAT phantom. Dentomaxillofac Radiol. 2016; 45:20160075.

10. de Oliveira MV, Wenzel A, Campos PS, Spin-Neto R. Quality assurance phantoms for cone beam computed tomography: a systematic literature review. Dentomaxillofac Radiol. 2017; 46:20160329.

11. Choi JW. Analysis of the priority of anatomic structures according to the diagnostic task in cone-beam computed tomographic images. Imaging Sci Dent. 2016; 46:245–249.

12. Suomalainen A, Kiljunen T, Käser Y, Peltola J, Kortesniemi M. Dosimetry and image quality of four dental cone beam computed tomography scanners compared with multislice computed tomography scanners. Dentomaxillofac Radiol. 2009; 38:367–378.

13. Özer SY. Detection of vertical root fractures by using cone beam computed tomography with variable voxel sizes in an in vitro model. J Endod. 2011; 37:75–79.

14. Liedke GS, da Silveira HE, da Silveira HL, Dutra V, de Figueiredo JA. Influence of voxel size in the diagnostic ability of cone beam tomography to evaluate simulated external root resorption. J Endod. 2009; 35:233–235.

15. Kwan AL, Boone JM, Yang K, Huang SY. Evaluation of the spatial resolution characteristics of a cone-beam breast CT scanner. Med Phys. 2007; 34:275–281.

16. Araki K, Maki K, Seki K, Sakamaki K, Harata Y, Sakaino R, et al. Characteristics of a newly developed dentomaxillofacial X-ray cone beam CT scanner (CB MercuRay): system configuration and physical properties. Dentomaxillofac Radiol. 2004; 33:51–59.

17. Watanabe H, Honda E, Tetsumura A, Kurabayashi T. A comparative study for spatial resolution and subjective image characteristics of a multi-slice CT and a cone-beam CT for dental use. Eur J Radiol. 2011; 77:397–402.

18. Ludlow JB, Walker C. Assessment of phantom dosimetry and image quality of i-CAT FLX cone-beam computed tomography. Am J Orthod Dentofacial Orthop. 2013; 144:802–817.

19. Torgersen GR, Hol C, Møystad A, Hellén-Halme K, Nilsson M. A phantom for simplified image quality control of dental cone beam computed tomography units. Oral Surg Oral Med Oral Pathol Oral Radiol. 2014; 118:603–611.

20. Steiding C, Kolditz D, Kalender WA. A quality assurance framework for the fully automated and objective evaluation of image quality in cone-beam computed tomography. Med Phys. 2014; 41:031901.

21. Dillenseger JP, Matern JF, Gros CI, Bornert F, Goetz C, Le Minor JM, et al. MSCT versus CBCT: evaluation of high-resolution acquisition modes for dento-maxillary and skull-base imaging. Eur Radiol. 2015; 25:505–515.