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Study concludes that ultralow-dose CT may substitute for standard-dose CT in some COPD patients

June 06, 2016

Leesburg, VA, June 6, 2016-- A Japanese retrospective study that reviewed the CT data of 50 emphysema patients found that ultralow-dose CT (ULDCT) can substitute for standard-dose CT (SDCT) in disease quantification if both iterative reconstruction (IR) and filtered back projection are used.

The study, titled "Emphysema Quantification Using Ultralow-Dose CT with Iterative Reconstruction and Filtered Back Projection," was published in the June 2016 issue of the American Journal of Roentgenology.

"Although further studies are needed to validate the usefulness of emphysema quantification with ULDCT, we expect that emphysema quantification can be reliably performed with ULDCT both without and with IR to stratify lung cancer risk and reduce the radiation dose associated with CT screening for lung cancer," said lead author Dr. Mizuho Nishio, of the Advanced Biomedical Imaging Research Center, Kobe University Graduate School of Medicine, Kobe, Hyogo, Japan.

The introduction of MDCT has greatly increased the total number of CT examinations, accordingly raising concerns about radiation exposure and the associated cancer risk [1]. The current principle of clinical CT practice is to use a radiation dose as low as reasonably achievable while maintaining acceptable diagnostic accuracy.

"However, given the trade-off between image quality and radiation dose in CT, excessive dose reduction can interfere with the interpretation and analysis of CT images," Nishio said.

Since the early 1970s, filtered back projection has been used for CT image reconstruction.

It is being replaced, however, by iterative reconstruction (IR), which is becoming widely used to decrease the radiation dose in CT. Many studies have shown that substantial dose savings can be achieved in CT when IR is used [2-13].

CT is widely performed in patients with chronic obstructive pulmonary disease (COPD), and this technique allows quantitative evaluation to assess the progression of COPD and to monitor therapeutic effects.
To view the June 2016 issue of AJR, visit ARRS's website at and click the yellow flag.


1. Fazel R, Krumholz HM, Wang Y, et al. Exposure to low-dose ionizing radiation from medical imaging procedures. N Engl J Med 2009; 361:849-857

2. Willemink MJ, de Jong PA, Leiner T, et al. Iterative reconstruction techniques for computed tomography. Part 1. Technical principles. Eur Radio 2013; 23:1623-1631

3. Willemink MJ, Leiner T, de Jong PA, et al. Iterative reconstruction techniques for computed tomography. Part 2. Initial results in dose reduction and image quality. Eur Radiol 2013; 23:1632-1642

4. Prakash P, Kalra MK, Ackman JB, et al. Diffuse lung disease: CT of the chest with adaptive statistical iterative reconstruction technique. Radiology 2010; 256:261-269

5. Pontana F, Pagniez J, Duhamel A, et al. Reduceddose low-voltage chest CT angiography with sinogram affirmed iterative reconstruction versus standard-dose filtered back projection. Radiology 2013; 267:609-618

6. Ohno Y, Takenaka D, Kanda T, et al. Adaptive iterative dose reduction using 3D processing for reduced- and low-dose pulmonary CT: comparison with standard-dose CT for image noise reduction and radiological findings. AJR 2012; 199:[web]W477-W485

7. Khawaja RD, Singh S, Gilman M, et al. Computed tomography (CT) of the chest at less than 1 mSv: an ongoing prospective clinical trial of chest CT at submillisievert radiation doses with iterative model image reconstruction and iDose4 technique. J Comput Assist Tomogr 2014; 38:613-619

8. Yamada Y, Jinzaki M, Tanami Y, et al. Modelbased iterative reconstruction technique for ultralow-dose computed tomography of the lung: a pilot study. Invest Radiol 2012; 47:482-489

9. Yanagawa M, Gyobu T, Leung AN, et al. Ultralow-dose CT of the lung: effect of iterative reconstruction techniques on image quality. Acad Radiol 2014; 21:695-703

10. Nishio M, Matsumoto S, Ohno Y, et al. Emphysema quantification by low-dose CT: potential impact of adaptive iterative dose reduction using 3D processing. AJR 2012; 199:595-601

11. Mets OM, Willemink MJ, de Kort FP, et al. The effect of iterative reconstruction on computed tomography assessment of emphysema, air trapping and airway dimensions. Eur Radiol 2012; 22:2103-2109

12. Koyama H, Ohno Y, Nishio M, et al. Iterative reconstruction technique vs filter back projection: utility for quantitative bronchial assessment on low-dose thin-section MDCT in patients with/without chronic obstructive pulmonary disease. Eur Radiol 2014; 24:1860-1867

13. Choo JY, Goo JM, Lee CH, Park CM, Park SJ, Shim MS. Quantitative analysis of emphysema and airway measurements according to iterative reconstruction algorithms: comparison of filtered back projection, adaptive statistical iterative reconstruction and model-based iterative reconstruction. Eur Radiol 2014; 24:799-806

Founded in 1900, ARRS is the first and oldest radiology society in the United States, and is an international forum for progress in radiology. The Society's mission is to improve health through a community committed to advancing knowledge and skills in radiology. ARRS achieves its mission through an annual scientific and educational meeting, publication of the American Journal of Roentgenology (AJR) and InPractice magazine, topical symposia and webinars, and print and online educational materials. ARRS is located in Leesburg, VA.

American Roentgen Ray Society

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