Comparison of radiation dose in Multidetector computed tomography and Flat-panel computed tomography for imaging of the wrist

Transcription

1 Comparison of radiation dose in Multidetector computed tomography and Flat-panel computed tomography for imaging of the wrist Poster No.: C-1457 Congress: ECR 2015 Type: Scientific Exhibit Authors: J. Neubauer 1, C. Neubauer 1, M. Langer 1, E. Kotter 1, J. M. Voigt 2, Keywords: DOI: M. Fiebich 2 ; 1 Freiburg/DE, 2 Gießen/DE Radioprotection / Radiation dose, CT, Cone beam CT, Comparative studies, Dosimetric comparison /ecr2015/C-1457 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 7

2 Aims and objectives The aim of our study was to find the lowest radiation dose still resulting in good image quality for a multidetector computed tomography (MDCT) and a flat-panel computed tomography (FPCT) in wrist examinations. Methods and materials We used a 320-row MDCT (Aquilion One, Toshiba, Otawara-shi, Japan) and a mobile dedicated extremity FPCT (Verity; Planmed, Helsinki, Finland) for data acquisition. For the MDCT the voltage can be set to 80, 100, 120 and 135 kvp. In FPCT the voltage can be changed from 80 to 96 kvp. The default settings for wrist examinations were 120 kvp / 40 mas in the MDCT and 90 kvp / 36 mas in the FPCT. In vitro wrist examinations of a cadaveric human hand were performed in default settings and all possible settings with lower doses in the MDCT (default setting and 20 low dose settings) and the FPCT (default setting and 19 low dose settings). The tube voltage we used in the MDCT ranged from 80 to 120 kvp (80, 100, 120 kvp) with equally modified tube currents from 5 to 40 mas (5, 7, 10, 15, 20, 30, 40 mas) for each voltage setting. Accordingly to the capabilities of the FPCT we chose a tube voltage from 80 to 90 kvp (80, 84, 88, 90 kvp) with a tube current ranging from 12 to 36 mas (12, 18, 24, 30, 36 mas) for each voltage setting in the FPCT. Monte Carlo simulations were used to calculate the radiation doses as previously described [1]. The images were reconstructed with iterative technique (AIDR3) for MDCT and with filtered back projection algorithm for FPCT. Then the data were sent to a PACS (AGFA Impax 6, Agfa, Mortsel Belgium). Image quality regarding the cortical bone, cancellous bone, articular surface, soft tissue and artifacts was analyzed by 5 independent and blinded readers: 3 radiologists with an experience of 1, 3 and 5 years and 2 orthopedic surgeons with an experience of 10 and 18 years. The images were presented in a randomized order. Modality and dose settings were masked for the readers. For the analysis a Likert scale with a score ranging from 1 (= very good), 2 (= good), 3 (= fair), 4 (= poor) to 5 (= very poor) was used. Good overall image quality was assumed with a sum of all ratings #50. Results The calculated mean dose in the wrist ranged from 1.14 mgy in the lowest dose setting to mgy in default dose setting in MDCT examinations and from 1.76 mgy in lowest Page 2 of 7

3 dose setting to 7.15 mgy in default dose setting in FPCT examinations. The lowest dose resulting in good image quality for all structures was 4.54±0.10 mgy for MDCT using a voltage of 100 kvp and a current of 20 mas (Fig. 1), for FPCT it was 5.72±0.13 mgy with 90 kvp and 30 mas (Fig. 2). The overall interrater correlation was 0.43 (p<0.001). Images for this section: Fig. 1: Scatterplot: Sum of all ratings for MDCT vs. Dose. The color of the points indicates the kvp. Good overall image quality was assumed with a sum of all ratings #50, indicated by the black vertical line. Page 3 of 7

4 Fig. 2: Scatterplot: Sum of all ratings for FPCT vs. Dose. The color of the points indicates the kvp. Good overall image quality was assumed with a sum of all ratings #50, indicated by the black vertical line. Page 4 of 7

5 Fig. 3: Scatterplot: Sum of all ratings for MDCT and FPCT vs. Dose. The shape of the points indicates the device. Good overall image quality was assumed with a sum of all ratings #50, indicated by the black vertical line. Page 5 of 7

6 Conclusion We found both MDCT and FPCT to produce good image quality in wrist imaging with lower dose settings than the default settings. Although FPCT needed less radiation dose in default settings, we found the lowest dose setting with a good overall image quality to be achieved by the MDCT. Thus, adjusting CT protocols for wrist imaging seems advisable for both modalities with the MDCT having an even higher potential for dose reduction. In the last decade several studies suggested that small compact FPCTs would administer lower radiation doses than MDCTs [2-4]. These investigations did not correlate the radiation dose with the image quality and therefore could not properly adjust MDCT protocols. If the image quality is investigated under equivalent dose conditions, the MDCT is reported to show better results for contrast resolution [1, 5]. Consistent to our findings Hofmann et al. showed in a study on orthodontic examinations that under optimized conditions clinically useful images could be performed by MDCT with even lower radiation doses than by different FPCTs [6]. Further investigations are needed to confirm these preclinical results. Personal information References 1. Neubauer J, Voigt JM, Lang H, et al. (2014) Comparing the Image Quality of a Mobile Flat-Panel Computed Tomography and a Multidetector Computed Tomography: A Phantom Study. Investig Radiol 49: Loubele M, Bogaerts R, Van Dijck E, et al. (2009) Comparison between effective radiation dose of CBCT and MSCT scanners for dentomaxillofacial applications. Eur J Radiol 71: Silva MAG, Wolf U, Heinicke F, et al. (2008) Cone-beam computed tomography for routine orthodontic treatment planning: A radiation dose evaluation. Am J Orthod Dentofac Orthop 133: Page 6 of 7

7 4. Schulze D, Heiland M, Thurmann H, Adam G (2004) Radiation exposure during midfacial imaging using 4- and 16-slice computed tomography, cone beam computed tomography systems and conventional radiography. Dentomaxillofacial Radiol 33: Kyriakou Y, Kolditz D, Langner O, et al. (2011) [Digital volume tomography (DVT) and multislice spiral CT (MSCT): an objective examination of dose and image quality]. RöFo#: Fortschritte auf dem Geb der Röntgenstrahlen und der Nukl 183: Hofmann E, Schmid M, Lell M, Hirschfelder U (2014) Cone beam computed tomography and low-dose multislice computed tomography in orthodontics and dentistry: a comparative evaluation on image quality and radiation exposure. J Orofac Orthop = Fortschritte der Kieferorthopädie#: Organ/official J Dtsch Ges für Kieferorthopädie 75: Page 7 of 7