Image acquisition and ultrasound. Taeyoung Kang Yonsei Univeristy Wonju College of Medicine South KOREA

Transcription

1 Image acquisition and ultrasound technique Taeyoung Kang Yonsei Univeristy Wonju College of Medicine South KOREA 1

2 Ultrasound Examination in Rheumatology; How to get best image Sonography is the most operator-dependent imaging technique Good quality examination depends on detailed attention to several factors Understanding the importance of machine set-up for optimal image acquisition Able to manipulate aspects of US equipment to obtain optimal image 2

3 Ultrasound Technique in Rheumatology; requirements for adequate image acquisition Ergonomic US machine and environment Knobology Focus, depth Anisotrophy B-mode gain Doppler ; Doppler gain Joint position Pressure of the probe Doppler frequency and Pulse repetition frequency (PRF) 3

4 Ergonomics: Machine and environment Adjustable screen Blinds, adjustable lighting, air conditioning Hand washing facilities and storage Swivel chair and adjustable height Essential Application of US in rheumatology 4

5 Ultrasound machine; Knobology, Touch screen Probe Selection Gain Depth Focus Measure Freeze;Cineloop 5

6 Probe selection Probe frequency Higher frequency, better resolution but poor penetration Footprint(hockey stick) probe linear, smaller for better access around small joints 6

7 Focus Focus to region of interest Use least number possible More foci, slow frame rate 7

8 Focus Focus 8

9 Depth Zoom can be too much sometimes. Adjust depth to maximize images on screen 9

10 Focus Depth 1 cm 2 cm 10

11 Probe positioning; Anisotropy Probe not Perpendicular Correct Incorrect 11

12 Probe positioning; Anisotrophy can be caused by even minimal changes of the probe inclination. Flexor pollicis longus tendon 12

13 Anisotropy; Tendon, ligament Rheumatoid Arthritis (tenosynovitis of the finger flexor tendons). Partial anisotropy. Circumscribed anisotropy induced by a slight inclin ation of the probe generates an intratendinous anechoic area(*) that could be misinterpreted as a partial tear. (Courtesy of Grassi, TUI Asian Summit) 13

14 Gain; brightness Overgain; too bright underrgain; too dark 14

15 Gain Regulation Normal gain Low gain Rheumatoid arthritis (tenosynovitis). Low gain may induce to o verestimate the amount of fluid collection inside the tendon sh eath. 15

16 Gain Regulation Normal gain Low gain Rheumatoid Arthritis (wrist). A wrong gain regulation may cause misinterpreation of joint cavity content. 16

17 Time Gain Compensation 17

18 Extended field of view 18

19 Colour versus Power Doppler Use Doppler Shift The Doppler shift (velocity and direction of flow) information displayed in different colour (blue ~ red) and brightness Use total back scattered power (energy) The power displayed in brightness 19

20 Doppler Gain Rheumatoid Arthritis (synovitis of the PIP joints, volar scan). Variability of the Doppler signal induced by the gradual reduction of gain level 20

21 Doppler Gain; Rubin method The method used to optimize gain Gain to fill the colour box with colour by increasing the gain 2. reduce the gain till no colour is seen the colour box Colour gain can b set at a level just below the disappearance of color noise deep to the cortical bone; Gain 0 21

22 Joint position Changes in GS and PD semi-quantitative grading following alterations in MCP joint position in an RA patient. Zayat A.S. et al; Rheumatology 2012;51:

23 Pressure of the probe Rheumatoid Arthritis (metacarpal head). A. No pressure B. Average degree of pressure of the probe on the skin 23

24 Doppler; PRF(Pulse Repetition Frequency) PRF 500 Hz Low High PRF 1000Hz Doppler sensitivity to lower slow flow High Low 24

25 Power Doppler Frequency 11.1 MHZ 9.1 MHZ 14.3 MHZ Rheumatoid Arthritis (wrist joint). 25

26 Optimal Doppler frequency Torp-Pedersen, S.T. et al; Ann Rheum Dis 2008;67:

27 In Summary US; most operator DEPENDENT imaging technique Ergonomics knobology Adequate Image acquisition and ultrasound examination technique Gain Frequency Doppler operator INDEPENDENT imaging technique 27

28 Thank you for your attention