47-55ÀÌÁ¤ÈÖ

Size: px

Start display at page:

Download "47-55ÀÌÁ¤ÈÖ"

응수 장
6 years ago
Views:

1 47

Fig. 2. Sagittal localizer image of ACR phantom. Table 1.

TE(ms) Matrix FOV(cm) Slice Thickness(mm) Gap(mm) NEX

0500 20 256256 25 05 5 1 T2 Spin Echo 2000 20/80 256256 25

2 Fig. 2. Sagittal localizer image of ACR phantom. Table 1. ACR Pulse Sequence Acquisition Parameters Image TR(ms) TE(ms) Matrix FOV(cm) Slice Thickness(mm) Gap(mm) NEX Sagittal Localizer T1 Spin Echo T2 Spin Echo / A Fig. 1. Oblique (A) and lateral (B) views of ACR phantom. B 48

3 A B Fig. 4. A. Slice 1 with resolution insert and hole array pairs indicated. B. Magnification view of high contrast resolution insert from slice 1 shows three sets of two arrays of holes. A B C Fig. 3. A. Positioning of length measurement on sagittal localizer (arrow). B. Slice 1 with diameter measurements illustrated (arrows). C. Position for diameter measurements on slice 5 (arrows). 49

4 Fig. 7. Image of slice 7 showing size and placement of the large ROI. Fig. 5. Magnified portion of slice 1 showing slice thickness signal ramps. The length measurements for the ramps are shown on the image (arrows). Fig. 6. Magnified portion of slice 1 illustrating slice position error. The arrows indicate the bar length difference measurement. Fig. 8. Image of slice 7 illustrating four small ROIs placement. 50

5 Fig. 9. Image of slice 11 showing the circles of low contrast objects. Table 2. MRI Instruments Symbol Site* Year MR Magnetic field Manufactured Manufacturer strength(tesla) A Ailab 0.3 B Toshiba 1.5 C Medison 1.0 D Fornor 0.35 E Picker 1.0 F Toshiba 1.5 G Picker 1.5 H Siemens 1.0 I GE 1.5 J GE 3.0 K GE 1.5 L Siemens 1.5 M Hitachi 0.3 N Isol 0.3 O GE 1.5 P GE 1.5 Q GE 1.5 R Medinus 1.5 S Elscint 0.5 T Hitachi 0.3 * 1: University hospitals, 2: General hospitals, 3: Hospitals, 4: Local clinics GE: General electric 51

6 Table 3. Results of MRI Phantom Test Test Slice Item Normal Range Mean Test Instruments Failed Instruments Failure Rate (No.) (No.) (%) Geometric Localizer End-to-End mm accuracy ACR T1 #1 Top-to-Bottom mm Left-to-Right ACR T1 #5 Top-to-Bottom Left-to-Right High contrast ACR T1 #1 Left-to-Right spatial resolution Top-to-Bottom ACR T2 #1 Left-to-Right Top-to-Bottom Slice thickness ACR T1 #1 Slice thickness mm accuracy ACR T2 #1 Slice thickness Slice position ACR T1 #1 Length difference 5 mm accuracy ACR T1 #11 Length difference ACR T2 #1 Length difference ACR T2 #11 Length difference Image intensity ACR T1 #7 PIU uniformity ACR T2 #7 PIU Percent signal ACR T1 #7 Ghosting ratio ghosting Low contrast ACR T1 #8# object ACR T2 #8# detectability Site T1 #8# Site T2 #8# ACR: American College of Radiology PIU: Percent integral uniformity 52

7 Table 4. Inter-Observer Variation Test Slice Item Measurements Variation (p Value) Failure Variation (p Value) Geometric accuracy Localizer End-to-End ACR T1 #1 Top-to-Bottom Left-to-Right ACR T1 #5 Top-to-Bottom Left-to-Right High contrast spatial resolution ACR T1 #1 Left-to-Right Top-to-Bottom ACR T2 #1 Left-to-Right Top-to-Bottom Slice thickness accuracy ACR T1 #1 Slice thickness ACR T2 #1 Slice thickness Slice position accuracy ACR T1 #1 Length difference ACR T1 #11 Length difference ACR T2 #1 Length difference ACR T2 #11 Length difference Image intensity uniformity ACR T1 #7 PIU ACR T2 #7 PIU Percent signal ghosting ACR T1 #7 Ghosting ratio Low contrast object detectability ACR T1 #8-# ACR T2 #8-#

8 1.. MRI,. In.., , ,,,,, ;50: American College of Radiology. MRI quality control manual. American College of Radiology, Reston, Chen CC, Wan YL, Wai YY, Liu HL. Quality assurance of clinical MRI scanners using ACR MRI phantom: preliminary results. J Digit Imaging 2004;17: Duina A, Mascaro L, Moretti R, Belletti S. Results of the quality control of magnetic resonance images. Radiol Med (Torino) 1992; 83: Kjaer L, Thomsen C, Henriksen O, Ring P, Stubgaard M, Pedersen EJ. Evaluation of relaxation time measurements by magnetic reso- imaging: a phantom study. Acta Radiol 1987;28: nance 8. Covell MM, Hearshen DO, Carson PL, Chenevert TP, Shreve P, Aisen AM, et al. Automated analysis of multiple performance characteristics in magnetic resonance imaging systems. Med Phys 1986;13: Hyde RJ, Ellis JH, Gardner EA, Zhang Y, Carson PL. MRI scanner variability studies using a semi-automated analysis system. Magn Reson Imaging 1994;12: Mascaro L, Strocchi S, Colombo P, Del Corona M, Baldassarri AM. Definition criteria for a magnetic resonance quality assurance program:multicenter study. Radiol Med (Torino) 1999;97: Firbank MJ, Harrison RM, Williams ED, Coulthard A. Quality assurance for MRI: practical experience. Br J Radiol 2000;73: Redpath TW, Wiggins CJ. Estimating achievable signal-to-noise ratios of MRI transmit-receive coils from radiofrequency power mea- surements: applications in quality control. Phys Med Biol 2000;45: Bourel P, Gibon D, Coste E, Daanen V, Rousseau J. Automatic quality assessment protocol for MRI equipment. Med Phys 1999; 26: Och JG, Clarke GD, Sobol WT, Rosen CW, Mun SK. Acceptance testing of magnetic resonance imaging systems: report of AAPM Nuclear Magnetic Resonance Task Group No. 6. Med Phys 1992; 19: Price RR, Axel L, Morgan T, Newman R, Perman W, Schneiders N, et al. Quality assurance methods and phantoms for magnetic resonance imaging: report of AAPM Nuclear Magnetic Resonance Task Group No. 1. Med Phys 1990;17: (MRI)., American College of Radiology. Phantom test guidance for the ACR MRI accreditation program. Reston: American College of Radiology

9 Usefulness of ACR MRI Phantom for Quality Assurance of MRI Instruments 1 Jung Whee Lee, M.D., Kook Jin Ahn, M.D., Seung Koo Lee, M.D. 2, Dong Gyu Na, M.D. 3, Chang Hyun Oh, Ph.D. 4, Yong Min Chang, Ph.D. 5, Tae Hwan Lim, M.D. 6 1 Department of Radiology, College of Medicine, The Catholic University of Korea 2 Department of Radiology, Yonsei University, College of Medicine 3 Department of Radiology, Seoul National University 4 Department of Electronics and Information Engineering, Korea University 5 Department of Diagnostic Radiology, College of Medicine, Kyungpook National University 6 Department of Diagnostic Radiology, Asan Medical Center, University of Ulsan Purpose: To examine whether the ACR phantom could be used in quality standards for magnetic resonance imaging (MRI) instruments in Korea. Materials and Methods: We conducted the phantom test using the ACR MRI phantom in 20 MRI instruments currently used in Korea. According to ACR criteria, we acquired the phantom images which were then assessed by the following seven tests: geometric accuracy, high spatial resolution, slice thickness accuracy, slice position accuracy, image intensity uniformity, percent signal ghosting, and low contrast object detectability. The phantom images were interpreted by three experienced radiologists according to ACR criteria. Then, we examined the failure rate of each test and evaluated the inter-observer variation in the measurements and test failure. Results: The failure rate of each test could be broken into the following components: geometric accuracy (11 21%), high contrast spatial resolution (1015%), slice thickness accuracy (622%), slice position accuracy (5 17%), image intensity uniformity (6%), percent signal ghosting (16%), and low contrast object detectability (8 10%). In this series, all the failure rates were less than 30%. In addition, no inter-observer variation was seen in the measurements and test failure. Conclusion: ACR MRI phantom promises to be established as the standard phantom for MRI instruments in Korea because of its objectivity in assessing the phantom images. Index words : Magnetic resonance (MR), quality assurance Phantoms Address reprint requests to : Kook Jin Ahn, M.D., Department of Radiology, College of Medicine, The Catholic University of Korea, St. Mary s Hospital, 62 Youido-dong, Youngdeungpo-gu, Seoul , Korea. Tel Fax ahn-kj@catholic.ac.kr 55

(

317 318 319 320 1 3 5 5 5 5 2 321 : 1.,,,,, 06 2. X-ray beam penetration (density) (contrast) 03 3. patch coating, precipitation, flaking 03 4. centering 03 5. Esophagus, cardia, fundus, body, angle, antrum,