Philips Site Yearly Performance Evaluation Philips Intera 1.5T 2-Mar-08. Table of Contents

Transcription

1 Philips Site Yearly Performance Evaluation Philips Intera.5T 2Mar8 Table of Contents Summary and Signature Page 2 Specific Comments Site Information 4 Equipment Information 4 Table Position ccuracy 4 Magnetic Field Homogeneity 4 Slice ccuracy 4 Slice Crosstalk 5 Soft Copy Displays 6 RF Coil Performance Evaluation Coil Inventory List 7 Body Integrated 8 Body Sense Coil 9 Breast Coil Head and eck Head Sense 2 Knee/Foot Quadrature 4 Shoulder rray Large 6 Shoulder rray Small 8 Spine Synergy 2 Surface C 2 Surface C 24 Surface C4 25 Surface E 26 Synergy FlexM 27 Wrist Coil High Res. ppendix : Magnet Homgeneity Map ppendix B: Slice / Profiles / RF Crosstalk ppendix C: CR Phantom nalysis ppendix D: Explanation of RF Coil Test Format

2 MRI Equipment Evaluation Summary & Signature Page Site ame: Philips Site MRP # ddress: Survey Date: City, State, Zip Report Date: MRI Mfg: Philips Model: Intera Field: /8/8 /7/8.5T MRI Scientist: Moriel essiver, Ph.D. Signature: Equipment Evaluation Tests Pass Fail * /. Magnetic field homogeneity: 2. Slice position accuracy:. Table positioning reproducibility: 4. Slice thickness accuracy: 5. RF coils' performance: a. Volume QD Coils b. Phase rray Coils c. Surface Coils 6. Interslice RF interference (Crosstalk): 7. Soft Copy Display 8. Hard Copy Display Evaluation of Site's Technologist QC Program Pass Fail * /. Set up and positioning accuracy: (daily) 2. Center frequency: (daily). Transmitter attenuation or gain: (daily) 4. Geometric accuracy measurments: (daily) 5. Spatial resolution measurements: (daily) 6. Low contrast detectability: (daily) 7. Head Coil (daily) 8. Body Coil (weekly) 9. Fast Spin Echo (F/T) ghosting levels: (daily). Film quality control: (weekly). Visual checklist: (weekly) *See comments page for description of any failures. Philips Site Philips Intera.5T 2

3 Specific Comments and Recommendations. The following warning was often seen: "Batteries of Magnet Emergency Rundown Unit are Low Contact Philips Service" Edwin says this is a known issue and the batteries are actually fine. How are we sure? 2.. The wrist coil has one totally dead channel and one weak channel. The film response is very good. The monitor's response curve is good in the middle but it dims a little too fast at the high end. The 5% is also rather difficult to see at the low end. 4. In general, the shim is very good. s can be seen in ppendix, there is a small region in the Inferior Right region that has slightly less homogeneity (still within spec). 5. Overall image quality looks good. O: Please be sure to read appendix D for an explanation of the new format of this document. Philips Site Philips Intera.5T

4 Site ame: Philips Site MRI Equipment Performance Evaluation Data Form Contact Title Owner Chief Tech. Phone Equipment Information MRI Manufacturer: Philips Model: Intera S: 54 Software:..4. Camera Manufacturer: Model: S: Software: PCS Manufacturer: Model: S: Software: CR Phantom umber used: Table Positioning Reproducibility: Table motion out/in: IsoCenter Measured Phantom Center.2 Comment: Out/In.8 Out/In Out/In.5.4 Pass 2. Magnetic Field Homogeneity See appendix for field plots. PSS xial: Coronal: Sagittal: Last Year CF: / This Year CF: 6929 CF Change: 5 cm 2 cm 25 cm GRE : 5, : & 5 Flip ngle: 45, : 4 mm skip mm, :.4KHz, x28, 2nex Comments: In general, the shim is very good. s can be seen in ppendix,.2.2. there is a small region in the Inferior Right region that has slightly less homogeneity (still within spec). Slice ccuracy : 25mm Matrix: x (Slice # from CR Phantom) ll values in mm (CR) (2/8) (2/8) Flip Calc Target % Error.6%.8% 2.8%.% T(5) % % Comments: Philips Site Philips Intera.5T 4

5 4. Slice Crosstalk (RF interference) The following data were obtained using the CR phantom slice thickness wedges to measure the slice profile of two T weighted sequences, a Spin Echo with either 69 pr 9 flip angle, when the slice gap varies from 2% down to % (contiguous) s the slices get closer together it is expected that the edges of the slices will overlap causing a deterioration of the slice profile. The data shown below clearly demonstrates this effect. Once the slice gap reaches % () of the slice thickness, the measured slice profile begins to drop. The main difference between the two sequences is the lower flip angle has a slightly smaller thickness as would be expected. ll of the slice profiles can be seen in ppendix B. (cm 2 ) Matrix # of slices Slice Measured x x Skip T Weighted Slice es (mm) Slice (mm) Philips Site Philips Intera.5T 5

6 5. Soft & Hard Copy Displays Luminance Meter Make/Model: Tektronix J6 Digital Photometer Monitor Description: LCD Luminance Measured: Ft. lamberts Cal Expires: 4/6/6 SMP Which Monitor Center of Image Display Top Left Corner Top Right Corner Bottom Left Corner Bottom Right Corner MX MI Percent Delta OK? Console Fair % delta =2% x (maxmin)/(max+center) (>% is action limit) imum Brightness must be > Ft. Lamberts The film response is very good. The monitor's response curve is good in the middle but it dims a little too fast at the high end. The 5% is also rather difficult to see at the low end. Density Ft Lamber ts Film from scanner Film from Camera. LCD & Film Response Curve Log FtLambert. Ideal Curve LCD Film Film % Density Philips Site Philips Intera.5T 6

7 Coil and Other Hardware Inventory List Site ame CR Magnet # Philips Site ickname chieva ctive Coil Description Manufacturer Model Rev. Mfg. Date S Channels Body Integrated QD Philips Jan, 24 Body Sense Coil Philips pr, Breast Coil Philips Mar, Head and eck Philips /86 Jun, /62 Head Quadrature Philips Mar, Head Sense Invivo Mar, Knee/Foot Quadrature Med. dvances Jan, Shoulder rray Large MRI Devices 227 Oct, 24 U Shoulder rray Small MRI Devices 227 Oct, 24 U Spine Synergy Mar, /S 5 Surface C Philips Feb, Surface C Philips Feb, Surface C4 Philips ov, 2 8 Surface E Philips May, /29 Syn. Multi Connect IGC Med. dvances Px Oct, /9 Syn. MultiConnect Philips Px Mar, 22 25/ Synergy FlexM Philips Mar, Synergy MultiConnect IGC Med. dvances Px Jan, /9 Wrist Coil High Res. MRI Devices 5 ug, 25 U

8 Coil: Body Integrated QD Mfg.: Philips Mfg. Date: //24 Coil ID: 562 Phantom: 2 cm GE sphere (used on pillows without table.) Test Date: /2/28 Model: S: # of Channels 2 T Coil Mode: BodyQD nalysis of Test Image % % Test Images Philips Site Intera 8

9 Coil: Body Sense Coil Mfg.: Philips Mfg. Date: 4//2 Coil ID: 5 Phantom: Philips Body disk Test Date: /2/28 Model: S: 974 # of Channels 4 2 T Coil Mode: Body Synergy nalysis of Composite Image clr, ,45,47, % 5.% 49.7% nalysis of Uncombined Images Ch ,27,45,9, % 68% % 89% % 69% 95% % The first composite image used CLER hence a greater signal uniformity. Composites Channels Channel Channel 2 Channel Channel 4 Philips Site Intera 9

10 Coil: Breast Coil Mfg.: Philips Mfg. Date: //24 Coil ID: 58 Phantom: 2 liter bottles with pad between them Test Date: /2/28 Model: S: 255 # of Channels 2 C Coil Mode: Breast (linear) nalysis of Test Image,228,24, %,26,, % Test Images Philips Site Intera

11 Coil: Head and eck Mfg.: Philips Mfg. Date: 6//22 Coil ID: 529 Phantom: CR Phantom in Head, liter bottle in neck Test Date: /2/28 Model: /86 S: /62 # of Channels 2 T Coil Mode: head head neck neck Head/eck HP ,8,8,62,64,64, nalysis of Composite Image % 79.9% 82.8% 82.7% nalysis of Uncombined Images Ch H P, ,,74, % 66% 46% % % 29% 46% % Composites Channels Channel Channel 2 Channel Channel 4 Philips Site Intera

12 Coil: Head Sense Mfg.: Invivo Mfg. Date: //2 Coil ID: 528 Phantom: CR Phantom Test Date: /2/28 Model: S: 8 # of Channels 6 2 T Coil Mode: Head Port # nalysis of Composite Image CL, ,57,9,4, % 68.8% 68.7% nalysis of Uncombined Images Ch ,87,8,5,77,28, % % 62% 67% 97% 6% % % 66% 7% 98% 66% This is normally an 8 channel coil, not a 6. channels 2 and 5 are actually 2 coils combined each. The results from Ports # & 2 are virtually identical. The first composite image used CLER hence a greater signal uniformity. Channel Channel 2 Channel Composites Channel 4 Channel 5 Channel 6 Philips Site Intera 2

13 Coil: Head Sense Mfg.: Invivo Mfg. Date: //2 Coil ID: 528 Phantom: CR Phantom Test Date: /2/28 Model: S: 8 # of Channels 6 2 T Coil Mode: Head Port #2 nalysis of Composite Image CL, ,5,26,26, % 69.2% 69.% nalysis of Uncombined Images Ch ,95,5,64,75,22, % 98% 6% 69% % 62% % 96% 67% 72% % 66% This is normally an 8 channel coil, not a 6. channels 2 and 5 are actually 2 coils combined each. The results from Ports # & 2 are virtually identical. Channel Channel 2 Channel Composites Channel 4 Channel 5 Channel 6 Philips Site Intera

14 Coil: Knee/Foot Quadrature Mfg.: Med. dvances Mfg. Date: //24 Coil ID: 526 Phantom: liter bottle in Knee, wrist phantom in foot Test Date: /2/28 Model: S: 878 # of Channels 2 T Coil Mode: Knee/Foot nalysis of Test Image,94, % 994, %,42,47, %,4,47, % Test Images Philips Site Intera 4

15 Coil: Knee/Foot Quadrature Mfg.: Med. dvances Mfg. Date: //24 Coil ID: 526 Phantom: liter bottle in Knee, wrist phantom in foot Test Date: /2/28 Model: S: 878 # of Channels 2 S Coil Mode: Knee/Foot PW nalysis of Test Image % %,224,8, %,224,4, % o phase wrap is used to eliminate wrap around of ghost into phantom. Test Images Philips Site Intera 5

16 Coil: Shoulder rray Large Mfg.: MRI Devices Mfg. Date: //24 Coil ID: 59 Phantom: Breast coil phantom Test Date: /2/28 Model: 227 S: U7964 # of Channels 4 2 T Coil Mode: SMCMRID 245 (Shoulder) nalysis of Composite Image ,7, % 52.% nalysis of Uncombined Images Ch ,5, % 6% % 92% % 44% 88% % Channel Channel 2 Composites Channel Channel 4 Philips Site Intera 6

17 Coil: Shoulder rray Large Mfg.: MRI Devices Mfg. Date: //24 Coil ID: 59 Phantom: Breast coil phantom Test Date: /2/28 Model: 227 S: U7964 # of Channels 4 2 S Coil Mode: SMCMRID 245 (Shoulder) nalysis of Composite Image 54 54,, % 29.% nalysis of Uncombined Images Ch ,94,2,29, % 75% 86% % % 58% 45% % Channel Channel 2 Composites Channel Channel 4 Philips Site Intera 7

18 Coil: Shoulder rray Small Mfg.: MRI Devices Mfg. Date: //24 Coil ID: 56 Phantom: Breast coil phantom Test Date: /2/28 Model: 227 S: U7999 # of Channels 4 2 T Coil Mode: SMCMRID 245 (Shoulder) nalysis of Composite Image % 46.2% nalysis of Uncombined Images Ch ,,9 87, % 42% % 68% % 8% 92% 6% Channel Channel 2 Composites Channel Channel 4 Philips Site Intera 8

19 Coil: Shoulder rray Small Mfg.: MRI Devices Mfg. Date: //24 Coil ID: 56 Phantom: Breast coil phantom Test Date: /2/28 Model: 227 S: U7999 # of Channels 4 2 S Coil Mode: SMCMRID 245 (Shoulder) nalysis of Composite Image % 7.8% nalysis of Uncombined Images Ch ,2 25 9,47, % 74% % 84% % 6% 55% % Channel #2 is a little lower than normal for this coil... but.. it could be related to phantom position. I don t think it is significant enough of a difference to merit action at this time. Channel Channel 2 Composites Channel Channel 4 Philips Site Intera 9

20 Coil: Spine Synergy Mfg.: Mfg. Date: //998 Coil ID: 525 Phantom: Philips Body Disk Test Date: /2/28 Model: S: 2667/S # of Channels 5 2 S Coil Mode: Spine Coil &2 nalysis of Composite Image % 27.8% nalysis of Uncombined Images Ch % 9% % 94% Composites Channel Channel 2 Philips Site Intera 2

21 Coil: Spine Synergy Mfg.: Mfg. Date: //998 Coil ID: 525 Phantom: Philips Body Disk Test Date: /2/28 Model: S: 2667/S # of Channels 5 2 S Coil Mode: Spine Coil 2& nalysis of Composite Image ,62, % 2.9% nalysis of Uncombined Images Ch 2 2 4,7, % % % % Composites Channel Channel 2 Philips Site Intera 2

22 Coil: Spine Synergy Mfg.: Mfg. Date: //998 Coil ID: 525 Phantom: Philips Body Disk Test Date: /2/28 Model: S: 2667/S # of Channels 5 2 S Coil Mode: Spine Coil 4&5 nalysis of Composite Image % 6.4% nalysis of Uncombined Images Ch , % % % % Composites Channel Channel 2 Philips Site Intera 22

23 Coil: Surface C Mfg.: Philips Mfg. Date: 2//24 Coil ID: 5 Phantom: PIQT Test Date: /2/28 Model: S: 756 # of Channels 2 C Coil Mode: C Ports & 2 nalysis of Test Image P,8, % P,8, % P2,2, % P2,7, % Test Images Philips Site Intera 2

24 Coil: Surface C Mfg.: Philips Mfg. Date: 2//24 Coil ID: 5 Phantom: PIQT Test Date: /2/28 Model: S: 62 # of Channels 2 C Coil Mode: C nalysis of Test Image,4, % 995, % Test Images Philips Site Intera 24

25 Coil: Surface C4 Mfg.: Philips Mfg. Date: //2 Coil ID: 52 Phantom: PIQT Test Date: /2/28 Model: S: 8 # of Channels 2 T Coil Mode: C4 nalysis of Test Image 845, % 88, % Test Images Philips Site Intera 25

26 Coil: Surface E Mfg.: Philips Mfg. Date: 5//2 Coil ID: 54 Phantom: liter bottle Test Date: /2/28 Model: S: 4574/29 # of Channels 2 T Coil Mode: E nalysis of Test Image 874, % 868, % Test Images Philips Site Intera 26

27 Coil: Synergy FlexM Mfg.: Philips Mfg. Date: //24 Coil ID: 55 Phantom: 5 liter bottle Test Date: /2/28 Model: S: 57 # of Channels 2 2 T Coil Mode: Synergy Flex M nalysis of Composite Image % 76.6% nalysis of Uncombined Images Ch % 97% % 88% Composites Channel Channel 2 Philips Site Intera 27

28 Coil: Synergy FlexM Mfg.: Philips Mfg. Date: //24 Coil ID: 55 Phantom: 5 liter bottle Test Date: /2/28 Model: S: 57 # of Channels 2 2 S Coil Mode: Synergy Flex M nalysis of Composite Image % 54.% nalysis of Uncombined Images Ch 2 4 5, % 95% % % Composites Channel Channel 2 Philips Site Intera 28

29 Coil: Wrist Coil High Res. Mfg.: MRI Devices Mfg. Date: 8//25 Coil ID: 54 Phantom: Wrist Phantom Test Date: /2/28 Model: 5 S: U2426 # of Channels 4 2 T Coil Mode: Wrist nalysis of Composite Image,294,294,98,97,68, % 9.2% nalysis of Uncombined Images Ch % % 5% 22% % % 52% 24% Channel 2 is dead, channel 4 is very sick. Channel Channel 2 Composites Channel Channel 4 Philips Site Intera 29

30 Coil: Wrist Coil High Res. Mfg.: MRI Devices Mfg. Date: 8//25 Coil ID: 54 Phantom: Wrist Phantom Test Date: /2/28 Model: 5 S: U2426 # of Channels 4 2 C Coil Mode: Wrist nalysis of Composite Image 92 92,6, % 4.7% nalysis of Uncombined Images Ch ,497, % % 8% 2% % % % 8% Channel 2 is dead, channel 4 is very sick. Channel Channel 2 Composites Channel Channel 4 Philips Site Intera

31 Coil: Wrist Coil High Res. Mfg.: MRI Devices Mfg. Date: 8//25 Coil ID: 54 Phantom: Wrist Phantom Test Date: /2/28 Model: 5 S: U2426 # of Channels 4 2 S Coil Mode: Wrist nalysis of Composite Image ,4, % 7.5% nalysis of Uncombined Images Ch ,, % % 9% 2% % % % 8% Channel 2 is dead, channel 4 is very sick. Channel Channel 2 Composites Channel Channel 4 Philips Site Intera

32 ppendix : Magnet Homogeneity Field Maps Philips Intera.5T central planes Measured March 2, 28 xial Right nterior 2 Left xial DIMER MI MX RGE PPM ME STDEV Posterior Coronal Right Superior 2 Left Coronal DIMER MI MX RGE PPM ME STDEV Inferior Sagittal nteriror Superior Posterior Sagittal DIMER MI MX RGE PPM ME STDEV Inferior

33 ppendix : Magnet Homogeneity Field Maps Philips Intera.5T Measured March 2, 28 Diameter cm 5cm 2cm 25cm 28cm cm Philips Site Intera xial Field Plot /2/ ppm cm from Isocenter (S/I) Diameter cm 5cm 2cm 25cm 28cm cm Philips Site Intera Coronal Field Plot /2/ ppm cm from Isocenter (P/) Diameter cm 5cm 2cm 25cm 28cm cm Philips Site Intera Coronal Field Plot /2/ ppm cm from Isocenter (R/L)

34 H9 2 H8 2 H7 2 2 H6 2 2 H5 2 2 H4 2 2 H 2 2 H H Isocenter F F2 2 2 F 2 2 F4 2 F5 F6 F7 F8 F9 xial Field Plots

35 Isocenter P 2 P2 2 P 2 2 P4 2 P5 2 P6 2 P7 2 P8 2 P9 Coronal Field Plots

36 2 2 L L L L L L4 2 2 L 2 2 L2 2 L 2 Isocenter 2 R 2 2 R2 2 2 R 2 2 R4 2 2 R5 2 2 R6 2 2 R7 2 R8 2 2 R9 Sagittal Field Plots

37 ppendix B: RF Slice Profiles and Crosstalk Spin Echo : Flip = 69 / = 4/5 = 4.4 KHz nex = 2 Scan time: :25 RF Xtalk 69 sk Upper= Lower=48.6 RF Xtalk 69 sk 5. Upper=48.67 Lower= RF Xtalk 69 sk 2.5 Upper=48.6 Lower= Slice = RF Xtalk 69 sk 2. Upper=48.72 Lower=48. Slice = RF Xtalk 69 sk.5 Upper=48.7 Lower=48.44 Slice = RF Xtalk 69 sk. Upper=47.9 Lower= Slice = RF Xtalk 69 sk.5 Upper=46.9 Lower=45.82 Slice = RF Xtalk 69 sk.2 Upper=44.66 Lower=44.2 Slice = RF Xtalk 69 sk. Upper=4.7 Lower= Slice = Slice Slice = Slice =4.4 Slice thickness as a function of slice gap Slice

38 ppendix B: RF Slice Profiles and Crosstalk Spin Echo : Flip = 69 / = 4/5 = 4.4 KHz nex = 2 Scan time: :25 RF Xtalk 9 sk Upper=5.7 8 Lower=48.94 RF Xtalk 9 sk 5. Upper=49.59 Lower= RF Xtalk 9 sk 2.5 Upper=49.78 Lower= Slice = RF Xtalk 9 sk 2. Upper=49. Lower= Slice = RF Xtalk 9 sk.5 Upper=49.4 Lower= Slice = RF Xtalk 9 sk. Upper=47.88 Lower= Slice = RF Xtalk 9 sk.5 Upper=46.6 Lower= Slice = RF Xtalk 9 sk.2 Upper=44.8 Lower= Slice = RF Xtalk 9 sk. Upper=44.8 Lower= Slice = Slice = Slice = Slice Slice thickness as a function of slice gap Slice

39 Philips Site Coil Used: Head Sense Sagittal Locator Length of phantom, end to end (mn 48± 2) 2 Slice Location # Resolution (.,.,.9 mm) Slice (fwhm in mm) Wedge (mm) Diameter (mm) (9±2) Slice Location #5 Diameter (mm) (9±2) Top Bottom Slice Location # Signal (mean only) Big ROI High Low 7 (>87.5%) (mean ±std dev) Top Bottom Left Right 22 2 Ghosting Ratio (<2.5%) (no spec) Calculated value 5.±.7 Low Con Detectability Slice Location #8 Slice Location #9 Slice Location # Slice Location # Total # of Spokes (>=9) Slice Location # Wedge (mm) Slice Position Error = + =.4% 2.5%.6% 5.% = + = 46.6 chieva Test Date: /2/28 = calculated field ( 5/2) ( 2/2) ( 2/8) (Site T) (Site T2) CR T CR PD CR T2 Site T Site T % 9.2% 9.% 9.2% 92.5% 4.7 ± ± ± ± 5.8. ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 5.2.%.2%.%.2%.%

40 Philips Site chieva parameters Test Date: /2/28 Coil Used: Head Sense Test ID Study Descrip tion Pulse (ETL) (ms) (ms) (cm) Phase Sample Ratio umber of Slices (mm) Slice (ex) Freq Matrix Phase Matrix Band Width (khz) Scan Time (min:sec) CR T :9 CR PD Dual Echo :2 CR T2 Dual Echo :2 Site T :5 Site T2 T(5) : Magnet ID: 95 Coil ID: 528 TestID:

41 ppendix C: CR Phantom nalysis CR T Sagital Length High Contrast Resolution Slice Slice Position Inferior Upper=5.98 Lower=49.7 Slice = Diff.=.49 xial Diameters # xial Diameters #5 & Ghosting #7 Slice Position Superior : :5 : PIU: 92.4% S.D S.D S.D S.D Diff.=.2 /2/8 : 499 : 2. Low Contrast #8 Low Contrast #9 Low Contrast # Low Contrast #

42 ppendix C: CR Phantom nalysis CR PD High Contrast Resolution Slice Slice Position Inferior Upper=5.7 Lower=49.47 Slice =5.4 Diff.=.56 xial Diameters # xial Diameters #5 & Ghosting #7 Slice Position Superior : :529 :4 PIU: 9.2% S.D S.D S.D S.D. 4.4 Diff.=.6 /2/8 :2 : 2. Low Contrast #8 Low Contrast #9 Low Contrast # Low Contrast #

43 ppendix C: CR Phantom nalysis CR T2 High Contrast Resolution Slice Slice Position Inferior Upper=5. Lower=47.2 Slice =4.86 Diff.=.52 xial Diameters # xial Diameters #5 & Ghosting #7 Slice Position Superior : :9 :794 PIU: 9.% S.D S.D S.D S.D Diff.=.4 /2/8 :2 : 8. Low Contrast #8 Low Contrast #9 Low Contrast # Low Contrast #

44 ppendix C: CR Phantom nalysis Site T High Contrast Resolution Slice Slice Position Inferior Upper=5.4 Lower=49.5 Slice =5. Diff.=.48 xial Diameters # xial Diameters #5 & Ghosting #7 Slice Position Superior : :547 :5 PIU: 9.2% S.D S.D S.D S.D Diff.=.2 /2/8 : 45 : 5. Low Contrast #8 Low Contrast #9 Low Contrast # Low Contrast #

45 ppendix C: CR Phantom nalysis Site T2 High Contrast Resolution Slice Slice Position Inferior Upper=54.97 Lower=52.9 Slice =5.9 Diff.=.64 xial Diameters # xial Diameters #5 & Ghosting #7 Slice Position Superior : :89 :769 PIU: 92.5% S.D S.D S.D S.D. 2.6 Diff.=.4 /2/8 :4 :. Low Contrast #8 Low Contrast #9 Low Contrast # Low Contrast #

46 ppendix D: Explanation of RF Coil Testing Report Introduction The primary goal of RF coil testing is to establish some sort of base line for tracking coil performance over time. The most common measure is the Signal to Ratio or. In addition, we can look at overall signal uniformity, ghosting level (or better lack of ghosting) and in the case of phased array coils we look at the of each and every channel and at symmetry between channels. Unfortunately, there is no single best method for measuring. Below I explain the different methods used and the rationale for each. One needs to measure the signal in the phantom (either mean or peak or both) and then divide that by the back noise. Measuring the signal is fairly straightforward, the noise can be more problematic. The simplest method is to measure the standard deviation () in the back air. However, MRI images are the magnitude of complex data. The noise in the underlying complex data is Gaussian but it follows a Rician distribution when the magnitude is used. The true noise can be estimated by multiplying the measured by.526. During the reconstruction process, most manufacturers perform various additional operations on the images, This could include geometric distortion correction, low pass filtering of the kspace data resulting in low signal at the edge of the images, RF coil intensity correction (PURE, CLER, SCIC, etc), and other processing during the combination of phased array data and parallel imaging techniques. ll of these methods distort the back noise making it impossible to obtain an accurate (and reproducible) estimate of the image noise in the air region. The alternative is to use a method which I shall refer to as the (ational Electrical Manufacturers ssociation) method. The signal in the phantom area is a sum of the proton signal and noise. Once the signal to noise ratio exceeds 5:, the noise in the magnitude image is effectively Gaussian. To eliminate the proton signal, you acquire an image twice and subtract them. The measured in the phantom region should now be the true times the square root of 2. When determining the using the method, calculate the mean signal of the average of the two source images then divide by.77 x the measured in the same area as the mean signal. Unfortunately, this doesn t always work. It is absolutely imperative that the RF channel scalings, both transmit and receive, be identical with both scans. ny ghosting in the system is not likely to repeat exactly for both scans and will cause a much higher. Finally, the phantom needs to be resting in place prior to the scan long enough for motion of the fluid to have died down. Depending on the size and shape of the phantom, this could take any where from 5 to 2 minutes. One of the most common causes of ghosting is vibration from the helium coldhead. The best way to eliminate this artifact is to turn off the cold head, which will increase helium consumption. Because this vibration is periodic, the ghosting is usually of an over 2 (/2) nature. The affect inside the signal region of the phantom can be minimized by using a that is twice the diameter of the phantom (measured in the PE direction.) If the noise is to be measured in the air, then be sure to OT make measurements to either side of the phantom in the PE direction. Scan parameters also significantly affect measured. For most of the testing performed in this document I used a simple Spin Echo with a of, a of 2 and a slice thickness of mm and a receiver of 28. KHz (a pixel fat/water chemical shift). The was varied depending on the size of the coil and the phantom used. ll of the parameters used for each test can be found on each page immediately below the coil description.

47 Report Layout Each page of this report lists the data from a single test. The top third of the page describes the coil and phantom information, followed by the scan parameters used. The middle third contains the numbers measured and calculated results. This section will contain one table if the coil being tested is a single channel coil (i.e. quadrature or surface coils) and two tables if it is a multichannel phased array coil. The entries in the table will be described further below. The bottom section contains a few lines of comments (if necessary), a picture of the coil with the phantom as used for the testing and one or more of the images that were used for the measurements. There is usually one image for each composite image measurement and one image for each separate channel measurement. Each image shows the ROI (red line) where the mean signal was measured and two smaller ROIs (green lines) where the signal minimum and maximum was found. In the top left corner of each image is the mean signal in the large ROI. The bottom left corner contains the large ROI s area (in mm 2 ). The top right corner contains two numbers a mean and a standard deviation. If the method was used, then the top right corner will list the mean and of the large ROI (labeled ROI M and ROIsd) applied to the subtraction image. If the noise was measured in the back air the the numbers are labeled M and. Data Tables The meaning of most of the entries in the data table are should be self evident with a few exceptions. The first column in each table is labeled. In the composite analysis, this field may be empty or contain some sort of abbreviation to identify some aspect of the testing. Some possibilities are the letter for, for, L for Left, R for Right, C for CLER, oc for o CLER. In the Uncombined Image table, the label usually contains the channel number or similar descriptor. The column labeled will be either or SubSig which stands for Subtracted Signal, i.e. the method. Both tables contain a column for and which are the or signal divided by the of the noise scaled by either.526 () or.77 (). Composite Image Table: The final two columns in this table are and. It can be rather difficult to compare the performance of different coils particularly if different scan parameters are used. (Of course, it s even more difficult from one scanner to another.) I have standardized most of my testing to use a spin echo with a / of /2msec and a thickness of mm. The changes to depending on the size of the phantom used although I try to use a that is at least twice the diameter of the phantom as measured in the PE direction. For one reason or another, a change may be made in the scan parameters (either accidentally or intentionally such as turning on o Phase Wrap to eliminate aliasing, etc.). In order to make it easier to compare values I calculate a value. This value is theoretically what the would be if a of cm, x matrix, average, receiver of 5.6 KHz and slice thickness of mm had been used. Obviously, the final number is affected by the T/T2 values of the phantoms used as well as details of the coil and magnet field strength but it can be useful in certain situations. The value is defined by the CR as (maxmin)/(max+min). This is most important when looking at volume coils or for evaluating the effectiveness of surface coil intensity correction algorithms (such as PURE, CLER or SCIC). Uncombined Image Table: This table has two columns labeled and. When analyzing multichannel coils it is important to understand the relationship between the different channels, the inherent symmetry that usually exists between channels. In a 8 channel head or 4 channel torso phased array coil, all of the channels are usually have about the same. These two columns list how the (either or ) of each channel compares to the of the channel with the maximum value.