Objective(s). The major challenge encountered to decrease the milliamperes (mA) level in X-ray imaging systems is the quantum noise phenomena. This investigation evaluated dose exposure and image resolution of a low dose X-ray imaging (LDXI) prototype comprising a low mA X-ray source and a novel microlens-based sensor relative to current imaging technologies. Study Design. A LDXI in static (group 1) and dynamic (group 2) modes was compared to medical fluoroscopy (group 3), digital intraoral radiography (group 4), and CBCT scan (group 5) using a dental phantom. Results. The Mann-Whitney test showed no statistical significance in dose exposure between groups 1 and 3 and 1 and 4 and timing exposure (seconds) between groups 1 and 5 and 2 and 3. Image resolution test showed group 1 > group 4 > group 2 > group 3 > group 5. Conclusions. The LDXI proved the concept for obtaining a high definition image resolution for static and dynamic radiography at lower or similar dose exposure and smaller pixel size, respectively, when compared to current imaging technologies. Lower mA at the X-ray source and high QE at the detector level principles with microlens could be applied to current imaging technologies to considerably reduce dose exposure without compromising image resolution in the near future. 1. Introduction With all other technical factors (e.g., kilovolts, distance, time, etc.) held constant, patient radiation dose is directly proportional to the milliamperes (mA). A 50% reduction in mA would result in a decrease in radiation dose by 50% [1]. Previously, the mA range has not been taken into consideration in any attempt to reduce radiation dose to which dental patients are being exposed [2–6]. The sensitivity of a digital sensor is measured at a constant wavelength in nanometers (nm) on the basis of the detective quantum efficiency (DQE). This value is used primarily to describe imaging detectors in optical imaging and medical radiography [7]. The quantum efficiency (QE) is the ratio of impinging photons on a pixel to the number of collected electrons. The QE of the pixel is equal to the QE of the complementary metal oxide semiconductor (CMOS) photodiode multiplied for the fill factor of the pixel [8]. Fluoroscopy is a dynamic X-ray or X-ray movie showing images of video frame rates produced by a low mA X-ray source and image intensification at the detector level [9]. An image intensifier unit is capable of multiplying 1,000 to 20,000 times, electron-by-electron, of the produced image, therefore increasing the system QE while allowing dose reduction [10, 11].
References
[1]
Q. B. Carroll, Fuchs’s Radiographic Exposure and Quality Control, Charles C Thomas Publisher, 7th edition, 2003.
[2]
D. Uzbelger, “Comparison between medical fluoroscopy, digital dental imaging and intraoral radiography,” Journal of Dental Research, vol. 97, p. 701, 2005.
[3]
D. Uzbelger-Feldman, C. Susin, and J. Yang, “The use of fluoroscopy in dentistry: a systematic review,” Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontology, vol. 105, article e61, 2008.
[4]
D. Uzbelger Feldman, J. Yang, and C. Susin, “A systematic review of the uses of fluoroscopy in dentistry,” The Chinese Journal of Dental Research, vol. 13, no. 1, pp. 23–29, 2010.
[5]
D. Uzbelger Feldman, P. M. Panchal, and J. Yang, “Resolution and dose rates comparison among fluoroscopy, digital/film-based intraoral radiography and CBCT scan,” in Proceedings of the 61th Annual Meeting of the American Academy of Oral & Maxillofacial Radiology, San Diego, Calif, USA, 2010.
[6]
D. Uzbelger Feldman, A. Mistry, and J. Yang, “Radiation exposure and image resolution testing of a low-dose X-ray imaging,” in Proceedings of the 64th Annual Meeting of American Academy of Oral & Maxillofacial Radiology, Beverly Hills, Calif, USA, October 2013.
[7]
A. R. Cowen, A. G. Davies, and M. U. Sivananthan, “The design and imaging characteristics of dynamic, solid-state, flat-panel x-ray image detectors for digital fluoroscopy and fluorography,” Clinical Radiology, vol. 63, no. 10, pp. 1073–1085, 2008.
[8]
G. C. Holst and T. S. Lomheim, CMOS/CCD Sensors and Camera Systems, SPIE Press Book, Bellingham, Wash, USA, 2nd edition, 2011.
[9]
B. D. Giordano, S. Ryder, J. F. Baumhauer, and B. F. DiGiovanni, “Exposure to direct and scatter radiation with use of mini-c-arm fluoroscopy,” Journal of Bone and Joint Surgery—Series A, vol. 89, no. 5, pp. 948–952, 2007.
[10]
J. T. Thirlwall, “The detective quantum efficiency of medical x-ray image intensifiers,” Review of Scientific Instruments, vol. 69, no. 11, pp. 3953–3957, 1998.
[11]
S. Hasham, F. D. Burke, S. J. Evans, M. K. Arundell, and D. N. Quinton, “An audit of the safe use of the mini c-arm image intensifier in the out-patient setting,” Journal of Hand Surgery, vol. 32, no. 5, pp. 563–568, 2007.
[12]
J. A. Seibert, “Flat-panel detectors: how much better are they?” Pediatric Radiology, vol. 36, no. 14, pp. 173–181, 2006.
[13]
D. Uzbelger Feldman, “Real Time Imaging Technologies, LLC, Assignee. Apparatus for Diagnosis and/or Treatment in the Field of Dentistry using Fluoroscopic and Conventional Radiography,” US Patent 6543936, 2003.
[14]
D. Uzbelger Feldman, “Real Time Imaging Technologies, LLC, assignee. Dental Fluoroscopic Imaging System,” US patent 8,430,563, April 2013.
[15]
D. P. Chakraborty, “Image intensifier distortion correction,” Medical Physics, vol. 14, no. 2, pp. 249–252, 1987.
[16]
Y. Jiang and D. L. Wilson, “Optimization of detector pixel size for stent visualization in x-ray fluoroscopy,” in Medical Imaging 2004: Image Perception, Observer Performance, and Technology Assessment, vol. 5372 of Proceedings of SPIE, p. 311, May 2004.
[17]
B. A. Arnold and P. O. Scheibe, “Noise analysis of a digital radiography system,” American Journal of Roentgenology, vol. 142, no. 3, pp. 609–613, 1984.
[18]
D. W. Mah, J. A. Rowlands, and J. A. Rawlinson, “Measurement of quantum noise in fluoroscopic systems for portal imaging,” Medical Physics, vol. 23, no. 2, pp. 231–238, 1996.
[19]
M. Hensel, T. Pralow, and R. R. Grigat, “Modeling and real-time estimation of signal-dependent noise in quantum-limited imaging,” in Proceedings of the 6th WSEAS International Conference on Signal Processing, Robotics and Automation (ISPRA '07), World Scientific and Engineering Academy and Society, Corfu Island, Greece, February 2007.
[20]
S. Suh, S. Itoh, S. Aoyama, and S. Kawahito, “Column-parallel correlated multiple sampling circuits for CMOS image sensors and their noise reduction effects,” Sensors, vol. 10, no. 10, pp. 9139–9154, 2010.
[21]
American National Standards Institute, Photography—Direct-Exposing Medical and Dental Radiographic Film/Process Systems—Determination of ISO Speed and ISO Average Gradien, American National Standards Institute ISO, New York, NY, USA, 1991.
[22]
F. Tr？ger, Handbook of Lasers and Optics, Springer, Berlin, Germany, 2012.
[23]
M. K. Khoury, I. Parker, and D. W. Aswad, “Acquisition of chemiluminescent signals from immunoblots with a digital single-lens reflex camera,” Analytical Biochemistry, vol. 397, no. 1, pp. 129–131, 2010.
[24]
T. Ang, Digital Photography: An Introduction, DK Publishing, New York, NY, USA, 4th edition, 2012.
[25]
The British Journal of Photography Report. The 50 Best Photography Products of 2012. The British Journal of Photography, Apptitude Media Ltd., London, UK, 2012.
[26]
R. F. Stevens and N. Davies, “Lens arrays and photography,” The Journal of Photographic Science, vol. 39, pp. 199–208, 1991.
[27]
R. Hooke, Micrographia: or some Physiological Descriptions of Minute Bodies made by Magnifying Glasses, The Royal Society of London, London, UK, 1st edition, 1665.
[28]
P. H. Nussbaum, R. V？lkel, H. P. Herzig, M. Eisner, and S. Haselbeck, “Design, fabrication and testing of microlens arrays for sensors and microsystems,” Pure and Applied Optics, vol. 6, no. 6, pp. 617–636, 1997.
[29]
R. A. Stern, L. Shing, N. Waltham, H. Mapson-Menard, A. Harris, and P. Pool, “EUV and soft X-ray quantum efficiency measurements of a thinned back-illuminated CMOS active pixel sensor,” IEEE Electron Device Letters, vol. 32, no. 3, pp. 354–356, 2011.
[30]
S. N. Vasan, P. Sharma, C. N. Ionita, et al., “Image acquisition, geometric correction and display of images from a 2x2 x-ray detector array based on electron multiplying charge coupled device (EMCCD) technology,” in Medical Imaging 2013: Physics of Medical Imaging, vol. 8668 of Proceedings of SPIE, Lake Buena Vista, Fla, USA, 2013.
[31]
A. G. Farman and T. T. Farman, “A comparison of 18 different x-ray detectors currently used in dentistry,” Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology and Endodontics, vol. 99, no. 4, pp. 485–489, 2005.
[32]
http://www.sensorgen.info/CanonEOS_5D_MkIII.html.
[33]
R. G. van Silfhout and A. S. Kachatkou, “Fibre-optic coupling to high-resolution CCD and CMOS image sensors,” Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, vol. 597, no. 2-3, pp. 266–269, 2008.
[34]
H. Fan, H. L. Durko, S. K. Moore, et al., “DR with a DSLR: digital radiography with a digital single-lens reflex camera,” Proceedings of the Society of Photo-Optical Instrumentation Engineers, vol. 15, p. 7622, 2010.
[35]
D. Uzbelger Feldman, “Real time imaging technologies, LLC, assignee. Imaging apparatus and methods,” International patent application PCT/US13/49504, July 2013.
[36]
W. K. Chu, C. Smith, R. Bunting, P. Knoll P, R. Wobig, and R. Thacker, “Application of the CCD camera in medical imaging,” in Sensors, Cameras, and Systems for Scientific/Industrial Applications, 121, vol. 3649 of Proceedings of SPIE, San Jose, Calif, USA, January 1999.
[37]
M. K. Shrout, J. Weaver, B. J. Potter, and C. F. Hildebolt, “Spatial resolution and angular alignment tolerance in radiometric analysis of alveolar bone change,” Journal of Periodontology, vol. 67, no. 1, pp. 41–45, 1996.
[38]
M. K. Shrout, C. M. Russell, and B. J. Potter, “Spatial resolution in radiometric analysis of enamel loss A pilot study,” Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontics, vol. 81, no. 2, pp. 245–250, 1996.
[39]
A. Wenzel, F. Haiter-Neto, and E. Gotfredsen, “Influence of spatial resolution and bit depth on detection of small caries lesions with digital receptors,” Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology and Endodontology, vol. 103, no. 3, pp. 418–422, 2007.
[40]
A. C. M？rner-Svalling, Digital intraoral radiography: determination of technical properties and application evaluations [Dissertation], Department of Oral Radiology and Oral and Maxillofacial Surgery, Institute of Odontology, Karolinska Institute, Stockholm, Sweden, 2002.
[41]
H. S. Cho, S. G. Choi, B. S. Lee, and S. Kim, “Image quality evaluation of a highly-integrated digital X-ray imaging sensor for dental intraoral-lmaging applications,” Journal of the Korean Physical Society, vol. 51, no. 1, pp. 30–34, 2007.
