Low-dose CT coronary angiography: Role of adaptive statistical iterative reconstruction (ASIR)

Transcription

1 Low-dose CT coronary angiography: Role of adaptive statistical iterative reconstruction (ASIR) Poster No.: 456 Congress: ESCR 2012 Type: Authors: Keywords: DOI: Scientific Exhibit M. A. Glazkova, I. Arkhipova, V. Sinitsyn, E. A. Mershina; Moscow/ RU CT-Angiography, Cardiac, Radiation safety, Arteriosclerosis /ESCR.2012.P-456 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 12

2 Purpose Coronary CT angiography (CTA) is an accurate method for the noninvasive detection and follow-up of the patients with coronary artery disease. This method had been criticized for high radiation exposure to patient. The use of modern technology of an adaptive statistical iterative reconstruction (ASIR) can reduce the tube voltage (100 kv and less), that can decrease the radiation dose, but there are concerns about image quality. Purpose of Study To determine the effect of ASIR-algorithm on radiation dose and image quality for coronary CT angiography (CTA). Methods and Materials 57 patients undergoing CTA were prospectively included into the analysis. All patients with a resting HR higher than 85 bpm received mg metoprolol minutes before the coronary CTA examination. Exclusion criteria for this study were following: (#) frequent extrasystoles; (b) renal insufficiency with creatinine level >1,5 mg/dl; (c) allergy to iodinated contrast agents; (d) severe heart failure (NYHA III-IV); (e) pregnancy. Examinations were performed with 2 types of 64-row scanners using retrospective ECGgating. The results of 27 patients were reconstructed with filtered back projection (FBP) (group I) and 30 patients - with ASIR-algorithm (40 %) (group II). Characteristics of the patients (age, heart rate, BMI) were not statistically different between the two groups (Table 1). The CTA examinations using ASIR-algorithm were done with lower tube voltage than those using FBP (100 kv and 120 kv, resp.; p < 0,0001). According to the vendor's recommendations, we used 40% ASIR and 60% FBP image reconstruction for the 2-nd group. The phantom's analysis results also showed that 40% ASIR-algorithm should produce a diagnostically acceptable image with less noise than Page 2 of 12

3 a full-dose FBP, but without artificial smoothing of 100% ASIR-algorithm (Fig. 1 on page 3). Tab. 1 Patient's characteristics and CTA acquisition for two groups (group I - FBP; group II - 40 % ASIR-algorithm). Characteristics Group I Group II p-value (n=27) (n=30) Age¹ 61±9,65 61±10,9 0,54 Mean heart rate (beats/min) ¹ 62,7±8,3 59±8,9 0,71 Slice collimation 64 0,625 mm 64 0,625 mm - Tube voltage (kv) ,0001 Tube current (ma) ¹ 535±30,57 596±10,2 0,001 ¹ Mean±SD Patients received an intravenous injection of ml contrast medium (ioversol, 350 mgi/ml) with a rate 4-5 ml/s. We measured contrast level, image noise, signal-to-noise ratio (SNR) of ascending aorta, myocardium, left ventricular cavity and pulmonary trunk (Fig. 2 on page 4). Effective radiation doses were calculated using volume CT dose index (CTDIvol) and dose-length product (DLP) with a conversion coefficient 0,014 msv/ mgy*cm. Images for this section: Fig. 1: Effect of ASIR -algorithm on image noise. #. FBP reconstruction at half dose. b. 100% ASiR. c. 50% ASiR. Page 3 of 12

4 Fig. 2: Measurement of the contrast level (HU), image noise (HU) and signal-to-noise ratio (SNR) at the root of ascending aorta. The region of interest (ROI) was defined as 100 mm2. Page 4 of 12

5 Results Contrast level, image noise, SNR of an ascending aorta, pulmonary artery, left ventricular (LV) myocardium and cavity were not statistically different between the FBP- and ASIRgroups (Tab. 2, Fig. 3 on page 6 ). Tab. 2 Image noise and SNR in various anatomical ROI in FBP- and ASIR-groups. ROI Ascending aorta Image noise ¹ SNR ¹ FBP ASIR p FBP ASIR p 42,6 [15,53] LV 46 myocardium [16,7] LV cavity 45,7 49 [21,87] 51 [15,7] 53 0,53 7,8 [2,7] 0,124 2,1 [0,9] 0,24 6,4 9,25 [5,4] 1,9 [0,95] 0,05 0,6 7,48 [3,44] 0,21 [19] [24,38] [3,9] Pulmonary artery 43 [21] 42,9 [13] ¹median [interquartile ranges] 0,62 7,5 [5,3] 9,1 [3,9] 0,182 Application of ASIR-algorithm significantly improved overall images quality, especially in obese patients (Fig. 4 on page 6). There was 45,9 % reduction in the median [interquartile ranges] radiation dose between the ASIR- and FBP-groups (8,7 [3,5] msv vs 16,1 [1,4] msv, resp.; p < 0,0001). The values of CTDIv, DLP and E are shown in Table 3. Calculated CTDIv and DLP were 46 and 47 % lower for ASIR-algorithm, than those for FBP-reconstruction. Tab. 3 Characteristics of the radiation exposure for FBP- and ASIR-groups. Characteristics FBP (n=27) ASIR (n=30) #-value CTDIv (mgy)¹ 66 [7,6] 35,2 [7,6] 0,0001 DLP (mgy *cm)¹ 1151 [101] 606, 52 [279,7] 0,0001 Page 5 of 12

6 E (msv)¹ 16,1 [1,4] 8,7 [3,5] 0,0001 ¹Median [interquartile ranges] Using of 40 % ASIR-algorithm could reduce radiation dose by 45,9 % without significant image quality change (Fig. 5 on page 7 Fig. 6 on page 7). Images for this section: Fig. 3: FBP (a) and ASIR (b) reconstructions at the level of ascending aorta. Image noise in the ROI was lower in images reconstructed using ASIR-algorithm (circle in fig. b) compared with those reconstructed using FBP (circle in fig. a). Page 6 of 12

7 Fig. 4: 40 % ASIR-algorithm. Images of obese patient (BMI = 28,9 kg/m2). Effective radiation dose was 4, 5 msv. Fig. 5: Comparison of two reconstruction algorithm: 40 % ASIR (a) and FBP (b). Effective radiation dose was 7,3 msv for 40 % ASIR -algorithm (a) and 16 msv for FBP reconstruction (b). There was 54,3% dose reduction at 40 % ASIR -algorithm without image quality change. Page 7 of 12

8 Fig. 6: 40 % ASIR-algorithm : SSD, curved MPR of coronary arteries at 8 msv, with excellent image quality Page 8 of 12

9 Conclusion Coronary CTA using 40 % ASIR is accompanied with significant decrease of radiation dose without loss of image quality. References 1.Mettler FA Jr, Bhargavan M, Faulkner K, Gilley DB, Gray JE, Ibbott GS, Lipoti JA, Mahesh M, McCrohan JL, Stabin MG, Thomadsen BR, Yoshizumi TT (2009) Radiologic and nuclear medicine studies in the United States and worldwide: frequency, radiation dose, and comparison with other radiation sources Radiology 253(2): Alkadhi H (2009) Radiation dose of cardiac CT-what is the evidence? Eur Radiol 19: Hall EJ, Brenner DJ. Cancer risks from diagnostic radiology. Br J Radiol 2008; 81: National Institute of Environmental Health Sciences Website. List of cancer-causing agents grows. htm. Accessed March 28, Brenner DJ, Hall EJ. Computed tomography: an increasing source of radiation exposure. N Engl J Med 2007; 357: Leschka S, Stolzmann P, Schmid FT, et al. Low kilovoltage cardiac dual-source CT: attenuation, noise, and radiation dose. Eur Radiol 2008; 18: Prakash P, Kalra MK, Kambadakone AK, et al. Reducing abdominal CT radiation dose with adaptive statistical iterative reconstruction technique. Invest Radiol 2010; 45: Marin D, Nelson RC, Schindera ST, et al. Lowtube- voltage, high-tube-current multidetector abdominal CT: improved image quality and decreased radiation dose with adaptive statistical iterative reconstruction algorithm-initial clinical experience. Radiology 2010; 254: Leipsic J, Labounty TM, Heilbron B et al (2010) Estimated radiation dose reduction using adaptive statistical iterative reconstruction in coronary CT angiography: the ERASIR study. AJR 195: Page 9 of 12

10 10. Hara AK, Paden RG, Silva AC, Kujak JL, Lawder HJ, Pavlicek W. Iterative reconstruction technique for reducing body radiation dose at CT: feasibility study. AJR 2009; 193: Leipsic J, LaBounty TM, Heilbron B, et al. Adaptive statistical iterative reconstruction: assessment of image noise and image quality in coronary CT angiography. AJR 2010; 195: Einstein, AJ, Elliston, CD, Arai AE, et al. Radiation dose from single-heartbeat coronary CT angiography performed with a 320-detector row volume scanner. Radiology. 2010;254: Leschka S, Stolzmann P, Schmid FT et al (2008) Low kilovoltage cardiac dual-source CT: attenuation, noise, and radiation dose. Eur Radiol 18: Paul JF, Abada HT (2007) Strategies for reduction of radiation dose in cardiac multislice CT. Eur Radiol 17: Achenbach S, Anders K, Kalender WA (2008) Dual-source cardiac computed tomography: image quality and dose considerations. Eur Radiol 18: Jakobs TF, Becker CR, Ohnesorge B et al (2002) Multislice helical CT of the heart with retrospective ECG gating: reduction of radiation exposure by ECG-controlled tube current modulation. Eur Radiol 12: Cheng Z, Wang X, Duan Y et al (2010) Low-dose prospective ECG-triggering dualsource CT angiography in infants and children with complex congenital heart disease: first experience. Eur Radiol 20(10): Klass O, Jeltsch M, Feuerlein S et al (2009) Prospectively gated axial CT coronary angiography: preliminary experiences with a novel low-dose technique. Eur Radiol 19: Sommer WH, Schenzle JC, Becker CR et al (2009) Saving dose in triple-rule-out computed tomography examination using a highpitch dual spiral technique. Invest Radiol 45: Lell M, Hinkmann F, Anders K et al (2009) High-pitch electrocardiogram-triggered computed tomography of the chest: initial results. Invest Radiol 44: Leschka S, Stolzmann P, Desbiolles L et al (2009) Diagnostic accuracy of high-pitch dual-source CT for the assessment of coronary stenoses: first experience. Eur Radiol 19: Budoff MJ (2009) Radiation dose of cardiac CT-what is the evidence? Int J Cardiovasc Imaging 25: Page 10 of 12

11 23. Leschka S, Kim CH, Baumueller S et al (2010) Scan length adjustment of CT coronary angiography using the calcium scoring scan: effect on radiation dose. AJR 194:W272- W Liu YJ, Zhu PP, Chen B, et al. A new iterative algorithm to reconstruct the refractive index. Phys Med Biol 2007; 52:L5-L Cheng LCY, Fang T, Tyan J. Fast iterative adaptive reconstruction in low-dose CT imaging. Proceedings of the IEEE International Conference on Image Processing. New York, NY: IEEE. 2006: Silva AC, Lawder HJ, Hara A, Kujak J, Pavlicek W. Innovations in CT dose reduction strategy: application of the adaptive statistical iterative reconstruction algorithm. AJR Am J Roentgenol Jan;194(1): Personal Information Maria A. Glazkova 1 Student mary-ga@yandex.ru Irina M. Arkhipova, MD 1 Radiologist iarkhipova77@mail.ru Elena A. Mershina MD., PhD 1 Associate Professor of Radiology elena_mershina@mail.ru Valentin E. Sinitsyn, MD, ScD 1 vsini@mail.ru 1 Radiology Department Page 11 of 12

12 Federal Center of Medicine and Rehabilitation Ivankovskoe shosse 3, Moscow , Fussian Federation Page 12 of 12