618 AJR:187, September 2006 AJR 2006; 187:618–622 0361–803X/06/1873–618 © American Roentgen Ray Society M E D I C A L I M A G I N G A C E N T U R Y O F Ha et al. Motion Artifacts and Image Noise in CT of the Lung Chest Imaging • Original Research Effects of High-Resolution CT of the Lung Using Partial Versus Full Reconstruction on Motion Artifacts and Image Noise Hong Il Ha 1 Hyun Woo Goo Joon Beom Seo Jae-Woo Song Jin Seong Lee Ha HI, Goo HW, Seo JB, Song J-W, Lee JS Keywords: CT technique, high-resolution CT, lung DOI:10.2214/AJR.05.0852 Received May 19, 2005; accepted after revision July 12, 2005. 1 All authors: Department of Radiology, Asan Medical Center, University of Ulsan College of Medicine, 388-1 Poongnap-2 dong, Songpa-gu, Seoul, South Korea 138-736. Address correspondence to H. W. Goo (hwgoo@amc.seoul.kr). OBJECTIVE. The purpose of our study was to evaluate the effects of 0.3-second high-resolu- tion CT (HRCT) of the lung using partial reconstruction on cardiac motion artifacts and image noise. SUBJECTS AND METHODS. Thirty-seven pairs of 0.3-second (partial reconstruction) and 0.75-second (full reconstruction) HRCT images were obtained for the lower lung zone during full-inspiration breath-holding. Imaging parameters other than temporal resolution were identical for each patient. Two radiologists visually graded motion artifacts of the cardiac border, bronchi, pulmonary vessels, and fissure in the left lung on a 4-point scale (with 4 indicating no artifacts). The maximum width of motion along the left cardiac border and the area percentage of motion artifacts in the left lung were calculated. Image noise in the air and lung was also determined. Car- diac motion artifacts and image noises were compared between the two sets of CT images. RESULTS. Visual grades for the cardiac border (4 ± 0), bronchi (3.8 ± 0.7), pulmonary vessels (3.6 ± 0.8), and fissure (3.9 ± 0.5) were higher for 0.3-second images than for 0.75-sec- ond images (1.7 ± 0.7, 2.0 ± 1.0, 1.6 ± 0.7, and 2.4 ± 0.9, respectively) (p < 0.001). The max- imum width of motion along the left cardiac border (0.1 ± 0.5 mm) and the area percentage of motion artifacts in the left lung (6.7% ± 18.4%) were smaller for 0.3-second images than for 0.75-second images (4.5 ± 1.7 mm and 36.2% ± 20.9%, respectively) (p< 0.001). Image noises in the air (38.0 ± 9.2) and the lung (86.0 ± 23.1) were greater for 0.3-second images than for 0.75-second images (35.6 ± 9.6 and 76.0 ± 20.3, respectively) (p < 0.01). CONCLUSION. Compared with 0.75-second HRCT using full reconstruction, 0.3-sec- ond HRCT using partial reconstruction substantially reduces cardiac motion artifacts in the lung at the expense of increasing image noise. igh-resolution CT (HRCT) of the lung is the accepted diagnostic method for the detection and char- acterization of various pulmonary parenchymal abnormalities involving the air- ways, air space, and interstitium [1–4]. HRCT image quality is substantially affected by respi- ratory motion artifacts, cardiac motion artifacts, and radiation dose. Respiratory motion artifacts can be virtually eliminated if patients hold their breath during the scan, and better breath-hold- ing may be achieved by hyperventilation and administration of oxygen before scanning. Re- gardless of breath-holding, cardiac motion arti- facts can still affect lung images, particularly in the paracardiac regions, and may lead to misin- terpretation (e.g., bronchiectasis) [2, 5–7]. Car- diac motion artifacts can be reduced by the use of shorter gantry rotation times, prospective ECG triggering, retrospective ECG gating, and partial reconstruction [8–11]. Although associ- ated with an increase in image noise, low-dose HRCT has been reported to provide diagnostic- quality images [12, 13]. Modern CT machines are able to achieve shorter gantry rotation times up to 0.33 seconds, and as a result half-tempo- ral resolution (approximately 0.22 seconds) of the HRCT scan can be obtained using partial re- construction. The purpose of this prospective study was to evaluate 0.3-second HRCT of the lung using partial reconstruction in terms of cardiac motion artifacts and image noise. Subjects and Methods Between February 2004 and March 2004, 43 consecutive patients referred for HRCT were en- rolled in this study. The institutional review board approved the study and informed consent was ob- tained from all patients. All patients underwent HRCT during single or clustered full-inspiration breath-holding using a 16-MDCT (Somatom Sen- sation 16, Siemens Medical Solutions) scanner that was capable of partial (0.3-, 0.36-, or 0.54-second) or full (0.42-, 0.5-, or 0.75-second) reconstruction H Downloaded from www.ajronline.org by 52.73.204.196 on 05/17/22 from IP address 52.73.204.196. Copyright ARRS. For personal use only; all rights reserved